Electrochemical cell

An electrochemical cell includes: an electrode assembly; and a housing including a first sheet and a second sheet, wherein the first sheet includes a first gas blocking layer, and a first sealing layer, and wherein the second sheet includes a second gas blocking layer and a second sealing layer, wherein the housing defines an accommodation region which accommodates the electrode assembly, which is disposed between the first sheet and the second sheet, and wherein the housing includes a bonded member, wherein the bonded member includes a third gas blocking layer disposed between the first gas blocking layer and the second gas blocking layer, wherein the third gas blocking layer includes a plurality of nanostructures.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0161055, filed on Nov. 17, 2015, in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which is incorporated herein in its entirety by reference.

BACKGROUND

The present disclosure relates to an electrochemical cell.

2. Description of the Related Art

In line with technical advances in electronic fields, the market for various kinds of portable electronic devices such as mobile phones, game machines, portable multimedia players (PMPs), MPEG audio layer-3 (MP3), smart watches, smart phones, smart pads, e-book terminals, tablet computers, and wearable devices that attach to human bodies has been rapidly growing. As such as the portable electronic device-related market continues to grow, demand for batteries suitable for use in driving portable electronic devices are also increasing.

Unlike primary batteries, which are not rechargeable, secondary batteries are chargeable and dischargeable. In particular, lithium secondary batteries have higher voltages and higher energy densities per unit weight than nickel-cadmium batteries and nickel-hydrogen batteries. Recently, research into flexible secondary batteries is also underway. Thus there remains a need for an improved electrochemical cell.

SUMMARY

Provided is an electrochemical cell having enhanced gas blocking characteristics.

According to an aspect of an embodiment, an electrochemical cell includes an electrode assembly, and a housing configured to accommodate the electrode assembly and including a first sheet and a second sheet, wherein the first sheet includes a first gas blocking layer, and a first sealing layer, and wherein the second sheet includes a second gas blocking layer and a second sealing layer, wherein the housing defines an accommodation region which accommodates the electrode assembly, which is disposed between the first sheet and the second sheet, wherein the housing includes a bonded member, wherein the bonded member includes a third gas blocking layer disposed between the first gas blocking layer and the second gas blocking layer, wherein the third gas blocking layer includes a plurality of nanostructures.

An electrochemical cell including, a housing including a first sheet including a first gas blocking layer and first sealing layer on an inner surface of the first gas blocking layer, a second sheet including a second gas blocking layer and a second sealing layer on an inner surface of the second gas blocking layer, and a third gas blocking layer disposed between the first gas blocking layer and the second gas blocking layer and adjacent to adjacent edge portions of the first sealing layer and the second sealing layer, wherein the third gas blocking layer includes a plurality of nanostructures; and an electrode assembly disposed within a space defined by the first sheet and the second sheet.

A method of manufacturing an electrochemical cell, the method including: providing first sheet including a first gas blocking layer and first sealing layer on an inner surface of the first gas blocking layer; disposing an electrode assembly on the first sealing layer; disposing a second sheet on the electrode assembly, wherein the second sheet includes a second gas blocking layer and a second sealing layer; bonding an inner portion of the first sealing layer to an inner portion of the second sealing layer to form a fused sealing layer; disposing a composition including a plurality of nanostructures between edge portions of the first sealing layer and the second sealing layer; and fusing the edge portions of the first sealing layer and the second sealing layer and the nanostructures to form a third gas blocking layer between the first gas blocking layer and the second gas blocking layer, wherein the third gas blocking layer is adjacent to the fused sealing layer, wherein the third gas blocking layer includes the plurality of nanostructures to manufacture the electrochemical cell.

DETAILED DESCRIPTION

In the drawings, the size or thickness of each element may be exaggerated for clarity of explanation. In addition, it will be understood that when a predetermined material layer is referred to as being “on” a substrate or another layer, it can be directly on the substrate or the other layer or a third layer may also be present therebetween. In addition, in the following embodiments, a material for forming each of a plurality of layers is for illustrative purposes only and other materials may also be used.

Hereinafter, an electrochemical cell according to an embodiment will be described in more detail.

An electrochemical cell according to an embodiment includes an electrode assembly and a housing configured to accommodate the electrode assembly and including: a first sheet including a first gas blocking layer and a first sealing layer; and a second sheet including a second gas blocking layer and a second sealing layer. The housing includes an accommodation region which defines an internal area to accommodate the electrode assembly disposed between the first sheet and the second sheet and a bonded part formed by bonding edges of the first and second sheets together, the bonded part comprising a third gas blocking layer between the first gas blocking layer and the second gas blocking layer, wherein the third gas blocking layer includes a plurality of nanostructures.

The electrochemical cell may comprise a housing comprising a first sheet comprising a first gas blocking layer and first sealing layer on an inner surface of the first gas blocking layer, a second sheet comprising a second gas blocking layer and a second sealing layer on an inner surface of the second gas blocking layer, and a third gas blocking layer disposed between the first gas blocking layer and the second gas blocking layer and adjacent to adjacent edge portions of the first sealing layer and the second sealing layer, wherein the third gas blocking layer comprises a plurality of nanostructures; and an electrode assembly disposed within a space defined by the first sheet and the second sheet.

Since the bonded part of the electrochemical cell further includes the third gas blocking layer disposed between the first and second gas blocking layers and including the nanostructures, permeation of gases and/or moisture into the internal area of the electrochemical cell via the bonded part is suppressed and accordingly, the lifespan of the electrochemical cell may be enhanced.

Referring toFIG. 1andFIG. 2, which is an enlarged view of a first bonded member120ofFIG. 1, an electrochemical cell200includes an electrode assembly10and a housing100to accommodate the electrode assembly10. The housing100includes a first sheet101and a second sheet102, the first sheet101including a first gas blocking layer101band a first sealing layer101aand the second sheet102including a second gas blocking layer102band a second sealing layer102a. In addition, the housing100includes a region having an internal area105to accommodate the electrode assembly10, which is disposed between the first sheet101and the second sheet102and the first bonded member120and a second bonded members130that are formed by bonding inner portions of the first and second sealing layers101aand102atogether. In addition, the first and second bonded members120and130include third gas blocking layers122and132between the first gas blocking layer101band the second gas blocking layer102b, and the third gas blocking layers122and132include a plurality of nanostructures140. In addition, the first sheet101and the second sheet102may further include a first external insulating layer101cand a second external insulating layer102c, respectively at the respective outermost parts thereof. In addition, the electrochemical cell200may further include an electrolyte30disposed together with the electrode assembly10in the internal area105. AlthoughFIG. 1shows first and second bonded members120and130as separate elements for clarity, it is noted that the first and second bonded members120and130may be portions of a same bonded part. For example, in an embodiment in which the electrochemical cell is cylindrical, the bonded part would encircle an edge of the electrochemical cell, and in cross-section would show two portions, e.g., the first and second bonded members120and130.

Since the third gas blocking layers122and132are disposed between the first gas blocking layer101band the second gas blocking layer102b, the internal area105for accommodating the electrode assembly10is completely surrounded by the first and second gas blocking layers101band102b, respectively, and by the third gas blocking layer122and132, and thus permeation of gaseous molecules and/or moisture into the internal area105may be prevented or suppressed. The third gas blocking layers122and132may be disposed between the first and second gas blocking layers101band102bin the entire area of the first and second bonded members120and130, which may be formed by bonding the edges of the first and second sheets101and102together, for example. Although not shown in the drawings, the third gas blocking layers122and132entirely bond the edges of the first and second sheets101and102together. For example, referring toFIG. 3, a third gas blocking layer entirely bonds the edges of the electrochemical cell200together and is disposed between the first and second sheets.

Referring toFIGS. 1 and 2, in the first and second bonded members120and130, the first sealing layer101aand the second sealing layer102amay be completely fused so as to form a single layer. Hereinafter, the single layer formed by completely fusing the first and second sealing layers101aand102ais referred to as a fused sealing layer. For example, the first bonded member120may include a first fused sealing layer121at a right edge portion of the electrochemical cell200by fusing the first and second sealing layers101aand102a, and the second bonded member130may include a second fused sealing layer131at a left edge portion of the electrochemical cell200by fusing the first and second sealing layers101aand102a.

Referring toFIGS. 1 and 2, the third gas blocking layers122and132may be respectively separated from the internal area105by the first and second fused sealing layers121and131, which may be formed by fusing an inner a first portion of the first sealing layer101aand an inner a second portion of the second sealing layer102a. For example, the first fused sealing layer121may be disposed between the third gas blocking layer122and the internal area105, at the right edge portion of the electrochemical cell200. For example, the second fused sealing layer131may be disposed between the third gas blocking layer132and the internal area105, at the left edge portion of the electrochemical cell200. By including the first and second fused sealing layers121and131and the third gas blocking layers122and132, the internal area105may be protected or blocked from gaseous molecules and/or moisture of external environments.

Referring toFIGS. 1 and 2, the amount of the nanostructures in the third gas blocking layers122and132of the electrochemical cell200may be in the range of about 1 weight percent (wt %) to about 99 wt %, about 2 wt % to about 95 wt %, or about 4 wt % to about 90 wt %, with respect to the total weight of the third gas blocking layers122and132. For example, the amount of the nanostructures in the third gas blocking layers122and132may be in the range of about 5 wt % to about 90 wt % with respect to the total weight of the third gas blocking layers122and132. However, the amount of the nanostructures is not limited to the above ranges and may be appropriately adjusted to within a range that provides improved gas blocking characteristics.

Referring toFIGS. 1 and 2, in the electrochemical cell200, the thickness of the third gas blocking layers122and132may be in the range of about 0.2 micrometers (μm) to about 400 μm. However, the thickness of the third gas blocking layers122and132is not limited to the range described above and may be appropriately selected from ranges that may provide a low gas transmission rate and/or a low moisture transmission rate according to the standard of desired batteries. For example, the thickness of the third gas blocking layers122and132may be in the range of about 2 μm to about 400 μm. For example, the thickness of the third gas blocking layers122and132may be in the range of about 2 μm to about 200 μm. For example, the thickness of the third gas blocking layers122and132may be in the range of about 10 μm to about 100 μm. For example, the thickness of the third gas blocking layers122and132may be in the range of about 10 μm to about 80 μm.

Referring toFIGS. 1 and 2, in the electrochemical cell200, a width between a first end of the third gas blocking layer122(or132) contacting the outside and a second end thereof contacting the first fused sealing layer121(or the second fused sealing layer131) may be in the range of about 0.1 millimeter (mm) to about 30 mm. However, the width therebetween is not limited to the above range and may be appropriately selected from ranges that may provide a low gas transmission rate and/or a low moisture transmission rate as desired. For example, the width of the third gas blocking layers122and132may be in the range of about 0.1 mm to about 30 mm. For example, the width of the third gas blocking layers122and132may be in the range of about 0.5 mm to about 20 mm. For example, the width of the third gas blocking layers122and132may be in the range of about 1 mm to about 10 mm. For example, the width of the third gas blocking layers122and132may be in the range of about 1 mm to about 5 mm.

The term “one-dimensional nanostructures” as used herein refers to structures confined to the nanoscale in two dimensions. For example, the one-dimensional nanostructures have a size of about 0.1 nanometer (nm) to about 100 nm in two dimensions and a significantly larger size in the other dimension. Examples of the one-dimensional nanostructures include nanotubes, nanowires, and the like. The term “two-dimensional nanostructures” as used herein refers to structures confined to the nanoscale in one dimension. For example, the two-dimensional nanostructures have a size of about 0.1 nm to about 100 nm in one dimension and a significantly larger size in the other dimensions. Examples of the two-dimensional nanostructures include nanoplates, nanosheets, and the like. The term “three-dimensional nanostructures” as used herein refers to structures confined to the nanoscale in three dimensions. For example, the three-dimensional nanostructures may have a size of about 0.1 nm to about 100 nm in three dimensions. The three-dimensional nanostructures may be, for example, nanoparticles, or the like. An aspect ratio of the nanostructures may be about 1:2 to about 1:1,000,000, about 1:4 to about 1:100,000, or about 1:8 to about 1:10,000. Also, the nanostructures may have any suitable particle size, e.g., about 10 nm to about 10 μm, or about 100 nm to 1 μm. The particle size may be determined by light scattering.

Referring toFIGS. 1 and 2, in the electrochemical cell200, the nanostructures140may include a carbonaceous material. A carbonaceous material has a lower density than a non-carbonaceous inorganic material such as a metal oxide and thus may provide improved energy density of an electrochemical cell. The nanostructures140may include at least one material selected from graphene, carbon nanotubes, carbon nanowires, carbon nanobelts, fullerene, and graphite. However, the material of the nanostructures140is not limited to the above examples and any suitable carbonaceous material, including those used in the art, may be used.

For example, the nanostructures140may include exfoliated graphene. The exfoliated graphene including a plurality of graphene layers may have an interspacing d002 of about 0.35 nm to about 1.2 nm. For example, the interspacing d002 of the exfoliated graphene including a plurality of graphene layers may be in the range of about 0.35 nm to about 0.7 nm. For example, the interspacing d002 of the exfoliated graphene including a plurality of graphene layers may be in the range of about 0.35 nm to about 0.5 nm. The gas blocking characteristics of the third gas blocking layers122and132may be adjusted by adjusting the interspacing d002 of the exfoliated graphene.

For example, the nanostructures140may include graphene oxide, reduced graphene oxide, modified graphene oxide, or the like. However, the material of the nanostructures140is not limited to the above examples and any suitable carbonaceous material, including those available in the art for forming the nanostructures140, may be used. The reduced graphene oxide may be formed by chemically reducing graphene oxide using a reducing agent such as hydrazine, NaBH4, or the like or by thermally reducing graphene oxide through a heat treatment at a high temperature, e.g., about 300° C. to about 1000° C. According to a degree to which graphene oxide is reduced, the interspacing of graphene layers may be adjusted. For example, the higher the temperature, the smaller the interspacing of graphene layers. The modified graphene oxide may include a deformed graphene oxide. Non-limiting examples of a material for forming the nanostructures140include a wrinkled graphene oxide and a crumpled graphene oxide. However, the material of the nanostructures140is not limited to the above examples and any suitable modified graphene oxide, such as those used in the art for the nanostructures140may be used.

Referring toFIGS. 1 and 2, in the electrochemical cell200, the nanostructures140may include a non-carbonaceous inorganic material. For example, the nanostructures140may include a layered clay. For example, the nanostructures140may include at least one selected from an organized layered clay, intercalated layered clay, and exfoliated layered clay, or the like. The organized layered clays may be a layered clay mineral organized with the organizing agent, for example. For example, the nanostructures140may include at least one selected from montmorillonite, bentonite, kaolinite, mica, hectorite, fluorohectorite, saponite, beidelite, nontronite, stevensite, vermiculite, hallosite, volkonskoite, suconite, magadite, and kenyalite. However, the material of the nanostructures140is not limited to the above examples and any suitable non-carbonaceous inorganic material, including those used in the art for nanostructures, may be used.

For example, the nanostructures140may include a metal oxide. Examples of the metal oxide include at least one selected from titanium dioxide (TiO2), tin dioxide (SnO2), alumina (Al2O3), zinc oxide (ZnO), and silica (SiO2). However, the metal oxide of the nanostructures140is not limited to the above examples and any suitable metal oxide, including those used in the art for nanostructures may be used. For example, the nanostructures140may be metal oxide nanoparticles. The metal oxide may have insulating properties.

Referring toFIGS. 1 and 2, in the electrochemical cell200, the third gas blocking layers122and132may be a composite layer including a polymer and the nanostructures140. Since the third gas blocking layers122and132include a composite layer of a polymer and the nanostructures140, the internal area105may be effectively protected or blocked from gaseous molecules and/or moisture.

The third gas blocking layers122and132may include the nanostructures140that are non-periodically arranged. In the composite layer, the nanostructures140may be randomly arranged without a certain periodicity. For example, in the third gas blocking layers122and132, the nanostructures140may be spaced from one another by irregular intervals. The third gas blocking layers122and132include a tortuous path formed by the interspacing of the nanostructures140spaced from one another and thus have barrier properties. The nanostructures140may be two-dimensional nanostructures.

The polymer included in the third gas blocking layers122and132may be a polyolefin-based thermoplastic resin. Examples of the polymer included in the third gas blocking layers122and132include at least one selected from polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene (ABS), and polycarbonate (PC). However, the polymer of the third gas blocking layers122and132is not limited to the above examples and any suitable thermoplastic resin, including those used in the art, may be used. For example, the polymer included in the third gas blocking layers122and132may be PE or PP, taking the stability of polymer used with respect to the electrolyte30into consideration.

Referring toFIGS. 1 and 2, in the electrochemical cell200, at least one of the first sealing layer101aand the second sealing layer102amay include the nanostructures140that are non-conductive. Since the electrode assembly10and the electrolyte30are accommodated in the internal area105of the electrochemical cell200, the first and second sealing layers101aand102a, which surround the internal area105, are desirably non-conductive to prevent a short circuit between the electrode assembly10and the electrolyte30. Thus, the nanostructures140included in the first sealing layer101aand/or the second sealing layer102amay be non-conductive. The non-conductive nanostructures140may be the non-carbonaceous inorganic nanostructures described above. In addition, at least one of the first and second fused sealing layers121and131may include the non-conductive nanostructures140.

Referring toFIGS. 1 and 2, the first and second sealing layers101aand102amay have a thickness of about 0.1 μm to about 200 μm. However, the thickness thereof is not limited to the range described above and may be appropriately selected from ranges that may provide a low gas transmission rate and/or a low moisture transmission rate according to the standard of batteries required. For example, the thickness of the first and second sealing layers101aand102amay be in the range of about 1 μm to about 200 μm. For example, the thickness of the first and second sealing layers101aand102amay be in the range of about 1 μm to about 100 μm. For example, the thickness of the first and second sealing layers101aand102amay be in the range of about 5 μm to about 50 μm. For example, the thickness of the first and second sealing layers101aand102amay be in the range of about 5 μm to about 40 μm.

Referring toFIGS. 1 and 2, at least one of the first and second gas blocking layers101band102bmay include at least one material selected from a metal, metal oxide, polymer, and a carbonaceous material. However, the material of the first and second gas blocking layers101band102bare not limited to the above examples and any suitable material, including those used in the art, with a suitable gas transmission rate and/or a suitable moisture transmission rate may be used. By including at least one material selected from the metal, metal oxide, polymer, and the carbonaceous material, the first gas blocking layer101band/or the second gas blocking layer102bhave a water vapor transmission rate (WVTR) or an oxygen transmission rate (OTR) that is equal to or less than one fifth that of the first and second sealing layers101aand102a.

The metal included in the first and second gas blocking layers101band102bmay be at least one selected from aluminum, stainless steel, and nickel. However, the metal is not limited to the above examples and any suitable metal with gas blocking properties, including those used in the art, may be used. For example, when a metal layer includes iron-including aluminum, the metal layer may have improved insulating properties undergoes less formation of pinholes due to bending. Further, when forming the housing, the metal layer may enable sidewalls thereof to be easily formed. For example, at least one of the first and second gas blocking layers101band102bmay be a metal layer. The metal layer may have an uneven portion formed by embossing or the like. The first gas blocking layer101band/or the second gas blocking layer102bmay be a metal layer, e.g., thin metal foil. The metal layer may be formed by deposition or sputtering.

The metal oxide included in the first and second gas blocking layers101band102bmay comprise at least one selected from TiO2, SnO2, Al2O3, ZnO, and SiO2, but is not limited to the above examples. For example, any suitable metal oxide with gas blocking properties, including those used in the art, may be used. For example, at least one of the first and second gas blocking layers101band102bmay be a metal oxide layer. The metal oxide layer may be formed using a sol-gel method. The metal oxide layer may have insulating properties.

The polymer included in the first and second gas blocking layers101band102bmay comprise at least one selected from a polyketone, fluoropolymer, polyvinylidene chloride (PVDC), ethylene vinyl alcohol (EVOH), and liquid crystal polymer (LCP), but is limited to the examples described above. For example, any suitable polymer with gas blocking properties, including those used in the art, may be used. For example, at least one of the first and second gas blocking layers101band102bmay be a polymer layer. The polymer layer may be formed using a coating method.

The carbonaceous material included in the first and second gas blocking layers101band102bmay comprise at least one selected from graphite, carbon nanotubes, graphene, and carbon fibers, but is not limited to the examples described above. For example, any suitable carbonaceous material with gas blocking properties, including those used in the art, may be used. For example, at least one of the first and second gas blocking layers101band102bmay be a carbonaceous material layer. For example, the carbonaceous material layer may be a graphite sheet.

Referring toFIGS. 1 and 2, in the electrochemical cell200, at least one of the first and second gas blocking layers101band102bmay have a multilayer structure including a plurality of layers. For example, the first gas blocking layer101band/or the second gas blocking layer102bmay be a laminate of multiple metal layers. For example, the first gas blocking layer101band/or the second gas blocking layer102bmay comprise a laminate of multiple polymer layers. For example, the first gas blocking layer101band/or the second gas blocking layer102bmay comprise a carbonaceous material layer having a multilayer structure in which polymer layers are disposed on opposite surfaces of a carbon sheet. For example, the carbonaceous material layer may have a structure including three layers, e.g., a polypropylene layer/graphite sheet/nylon layer structure.

Referring toFIGS. 1 and 2, in the electrochemical cell200, the thickness of the first and second gas blocking layers101band102bmay be in the range of about 0.1 μm to about 200 μm, but is not limited to the range described above. That is, the thickness of the first and second gas blocking layers101band102bmay be appropriately selected from ranges that may provide a low gas transmission rate and/or a low moisture transmission rate as desired. For example, the thickness of the first and second gas blocking layers101band102bmay be in the range of about 1 μm to about 200 μm. For example, the thickness of the first and second gas blocking layers101band102bmay be in the range of about 1 μm to about 100 μm. For example, the thickness of the first and second gas blocking layers101band102bmay be in the range of about 5 μm to about 50 μm.

Referring toFIGS. 1 and 2, in the electrochemical cell200, the first sheet101may further include the first external insulating layer101cand the second sheet102may further include the second external insulating layer102c. Since the first and second sheets101and102further include the first and second external insulating layers101cand102c, respectively, the internal area105may be effectively protected or blocked from gaseous molecules and/or moisture of external environments.

The first external insulating layer101cand/or the second external insulating layer102cmay include a polymer. The polymer may be selected from polyesters, polycarbonates, and polyamides. Examples of polyesters include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN). Examples of polyamides include nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon-6,6, nylon-6,10, and poly(meta-xylene adipamide) (MXD 6).

Referring toFIGS. 1 and 2, in the electrochemical cell200, the first and second external insulating layers101cand102cmay have a thickness of about 0.1 μm to about 200 μm, but the thickness thereof is not limited to the range described above. For example, the thickness of the first and second external insulating layers101cand102cmay be appropriately selected from ranges that may provide a low gas transmission rate and/or a low moisture transmission rate as desired. For example, the thickness of the first and second external insulating layers101cand102cmay be in the range of about 1 μm to about 200 μm. For example, the thickness of the first and second external insulating layers101cand102cmay be in the range of about 1 μm to about 100 μm. For example, the thickness of the first and second external insulating layers101cand102cmay be in the range of about 5 μm to about 50 μm.

Referring toFIGS. 1 and 2, in the electrochemical cell200, the first and second sheets101and102may have a thickness of about 0.5 μm to about 500 μm, but the thickness thereof is not limited to the range described above. For example, the thickness of the first and second sheets101and102may be appropriately selected from ranges that may provide a low gas transmission rate and/or a low moisture transmission rate as desired. For example, the thickness of the first and second sheets101and102may be in the range of about 1 μm to about 400 μm. For example, the thickness of the first and second sheets101and102may be in the range of about 1 μm to about 300 μm. For example, the thickness of the first and second sheets101and102may be in the range of about 5 μm to about 200 μm.

Referring toFIGS. 1 and 2, in the electrochemical cell200, at least one of the first and second sheets101and102may be flexible and/or elastic. A flexibility of the first and second sheets may each independently be about 0.01 to about 3 gigaPascals (GPa), about 0.05 to about 2.5 GPa, or about 0.1 to about 1 GPa. Thus, the electrochemical cell200may have suitable flexibility or elasticity. Accordingly, the electrochemical cell200may have suitable durability for repeated bending.

Referring toFIGS. 1 to 3, in the electrochemical cell200, the first and second sheets101and102may have a multilayer structure including at least three layers. For example, the first and second sheets101and102may have a structure in which sealing layers, gas blocking layers, and external insulating layers are alternately arranged. For example, the first and second sheets101and102may further include other layers between a sealing layer and a gas blocking layer and an external insulating layer. For example, the first and second sheets101and102may further include an adhesive layer between at least two layers selected from a sealing layer, a gas blocking layer, and an external insulating layer. By including such an adhesive layer, adhesive strength between the layers described above may become stronger.

Referring toFIGS. 1 to 3, the electrochemical cell200and the electrode assembly10may have a length direction, a thickness direction, and a width direction defined as three directions that are perpendicular to one another. For example, inFIG. 0.1, a horizontal direction may be defined as the width direction, a vertical direction may be defined as the thickness direction, and a direction penetrating the drawing may be defined as the length direction. The electrochemical cell200may be configured such that the length thereof is greater than the width thereof. In this regard, when the electrochemical cell200is bent, the directions described above may vary according to the position of the electrochemical cell200. For example, as illustrated inFIG. 3, in an embodiment in which the electrochemical cell200is bent in a direction towards an axis of the width direction, the width direction is constant at all positions of the electrochemical cell200, while the length and thickness directions may continuously vary according to the positions thereof. In this regard, the length direction may be defined as a tangential direction contacting a curved surface at each position of the electrochemical cell200, and the thickness direction may be defined as a direction extending perpendicular to the tangential direction towards the curvature center of the curved surface.

The electrochemical cell200can have any suitable shape, and can have any desired number of sides. For example, electrochemical cell200may be rectangular and have four sides, as disclosed above, or may be pentagonal, hexagonal, septagonal, or octagonal, for example.

Alternatively, the electrochemical cell200may have a curvilinear shape, for example the electrochemical cell may be cylindrical, and may have a circular, oval, or stadium shaped cross-section.

FIG. 3is a schematic perspective view illustrating the structure of the electrochemical cell200ofFIG. 1. Referring toFIG. 3, the electrochemical cell200may extend in the length direction. That is, the length of the electrochemical cell200may be greater than the width thereof. In addition, the electrochemical cell200may include first and second lead tabs23and24extending in the length direction or the width direction and out of a first end portion thereof. The first and second lead tabs23and24may be electrically connected to the electrode assembly10accommodated in the accommodation part110and may extend from between the first sheet101and the second sheet102. To completely seal a region of the first and second sheets101and102in which the first and second lead tabs23and24are arranged, each of the first and second lead tabs23and24may further include a sealing member25at a middle part thereof. The sealing member25may comprise, for example, a thermoplastic material such as polyethylene or polypropylene and may be bonded with the first and second sealing layers101aand102a.

As illustrated inFIG. 3, the electrochemical cell200may be configured so as to bend towards an axis X of the width direction. AlthoughFIG. 3illustrates that the electrochemical cell200is entirely bent in the length direction, the electrochemical cell200may be partially bent in the length direction, towards the axis X of the width direction. As the electrochemical cell200is bent, the first and second bonded members120and130may also be bent towards the axis X of the width direction.FIGS. 1 and 5 to 11are cross-sectional views taken along the axis X of the width direction ofFIG. 3.

Referring toFIG. 4, the electrode assembly10may include a stacked electrode structure16and a binding member14to bind a first end portion of the stacked electrode structure16. The stacked electrode structure16may have a structure in which a plurality of first electrode plates11and11′, a plurality of separators13, and a plurality of second electrode plates12and12′ are disposed on one another, e.g., stacked. For example, the stacked electrode structure16may include the first electrode plates11and11′ and the second electrode plates12and12′ that are alternately stacked, and the separators13between the first electrode plates11and11′ and the second electrode plates12and12′. In this regard, the separators13may be bonded to the first electrode plates11and11′. The first electrode plates11and11′, the second electrode plates12and12′, and the separators13may comprise a flexible sheet and accordingly, the stacked electrode structure16may be flexible.

The first electrode plates11and11′ may include a first current collector11aand a first electrode active material layer11bdisposed on, e.g., formed on, a surface of the first current collector11a. In this regard, in the first electrode plate11formed on an inner side of the stacked electrode structure16, the first electrode active material layers11bmay be disposed on opposite surfaces of the first current collector11a, and in the first electrode plate11′ formed on an outer side of the stacked electrode structure16, the first electrode active material layer11bmay be disposed only on one surface of the first current collector11a. The second electrode plates12and12′ may include a second current collector12aand a second electrode active material layer12bdisposed on a surface of the second current collector12a. In this regard, in the second electrode plate12disposed on an inner side of the stacked electrode structure16, the second electrode active material layers12bmay be formed on opposite surfaces of the second current collector12a, and in the second electrode plate12′ disposed on an outer side of the stacked electrode structure16, the second electrode active material layer12bmay be disposed only on one surface of the second current collector12a.

Any one of the first electrode plates11and11′ and the second electrode plates12and12′ may be cathode plates and the other thereof may be anode plates. For example, when the first electrode plates11and11′ are cathode plates, the second electrode plates12and12′ may be anode plates. In addition, when the first electrode plates11and11′ are anode plates, the second electrode plates12and12′ may be cathode plates. When the first electrode plates11and11′ are cathode plates and the second electrode plates12and12′ are anode plates, the first current collector11amay be a cathode current collector and the first electrode active material layer11bmay be a cathode active material layer. In addition, the second current collector12amay be an anode current collector and the second electrode active material layer12bmay be an anode active material layer.

The binding member14may be arranged on the first end portion of the stacked electrode structure16. The first end portion of the stacked electrode structure16may be fixed by the binding member14. Examples of the binding member14include an adhesive, a tape coated with an adhesive, and the like, but various other binding members may also be used. Since the first end portion of the stacked electrode structure16is fixed by the binding member14, the first electrode plates11and11′, the separators13, and the second electrode plates12and12′ maintain alignment for a reversible electrochemical reaction even when the electrode assembly10is deformed by bending. The binding member14may be omitted. When the binding member14is not used, the stacked electrode structure16corresponds to the electrode assembly10.

Referring toFIGS. 5 and 6, at least one of the first and second bonded members120and130may be bent at an angle of 180° towards the accommodation part110. Thus, a path through which gases and/or moisture permeates into the internal area105becomes longer and accordingly, the internal area105may be effectively protected or blocked from gaseous molecules and/or moisture of external environments. In addition, in an electrochemical module including a plurality of the electrochemical cells200, an empty space between the second bonded members130of the electrochemical cells200decreases and thus an energy density per unit volume of the electrochemical module may be enhanced. In another embodiment, although not shown in the drawing, at least one of the first and second bonded members120and130may be bent at 90° towards the accommodation part110.

Referring toFIGS. 7 and 8, at least one of the first and second bonded members120and130may be repeatedly bent at 180° towards and away from the accommodation part110. By this configuration, a path through which gases and/or moisture permeates into the internal area105becomes longer and accordingly, the internal area105may be effectively protected or blocked from gaseous molecules and/or moisture of external environments. In addition, in an electrochemical module including a plurality of the electrochemical cells200, an empty space between the second bonded member130of the electrochemical cells200decreases and thus an energy density per unit volume of the electrochemical module may be enhanced. For example, referring toFIG. 7, the first bonded member120of the electrochemical cell200may be bent at 180° once towards the accommodation part110and once apart therefrom. For example, referring toFIG. 8, the first bonded member120of the electrochemical cell200may be bent at 180° once towards the accommodation part110, once away from the accommodation part110, and once towards the accommodation part110.

Referring toFIGS. 9 and 10, at least one of the first bonded member120and the second bonded member130may further include a fourth gas blocking layer, e.g., fourth gas blocking layers123and133respectively contacting the third gas blocking layers122and132or the first and second fused sealing layers121and131. The fourth gas blocking layers123and133correspond to a structure in which the first and second gas blocking layers101band102bare bent so as to face each other and be connected to each other. Accordingly, the first and second sheets101and102of the electrochemical cell200form the housing100that is substantially integrally formed.

Referring toFIGS. 9 and 10, the fourth gas blocking layers123and133may respectively include lower and upper portions123aand123cand lower and upper portions133aand133cthat are respectively parallel to the first and second fused sealing layers121and131and positioned at different heights, and middle portions123band133bthat continuously extend between the lower and upper portions123aand123cand between the lower and upper portions133aand133c, respectively and that are bent so as to surround first ends of the third gas blocking layers122and132or the first and second fused sealing layers121and131.

Referring toFIGS. 10 and 11, in the electrochemical cell200including at least one of the fourth gas blocking layers123and133, at least one of the first bonded member120and the second bonded member130may be bent at 180° towards the accommodation part110. By this configuration, a path through which gases and/or moisture permeates into the internal area105becomes longer and thus the internal area105may be effectively protected or blocked from gaseous molecules and/or moisture of external environments. In addition, in an electrochemical module including a plurality of the electrochemical cells200, an empty space between the second bonded member130of the electrochemical cells200decreases and thus an energy density per unit volume of the electrochemical module may be enhanced.

Referring toFIG. 4, in the electrode assembly10, the first and second electrode active material layers11band12bof the first electrode plates11and11′ and the second electrode plates12and12′ include an electrode active material. The first and second electrode active material layers11band12bmay further include at least one of a conductive agent, a binder, and a plasticizer.

The first and second electrode active material layers11band12bmay include a cathode active material. Any suitable cathode active material including those used in the art as a cathode active material for secondary batteries may be used. The cathode active material may be a lithium-containing metal oxide.

In the formulae above, A is at least one selected from nickel (Ni), cobalt (Co), and manganese (Mn); B′ is at least one selected from aluminum (Al), Ni, Co, Mn, chromium (Cr), iron (Fe), magnesium (Mg), strontium (Sr), vanadium (V), and a rare earth element; D is at least one selected from oxygen (O), fluorine (F), sulfur (S), and phosphorus (P); E is at least one selected from Co, and Mn; F′ is at least one selected from F, S, and P; G is at least one selected from Al, Cr, Mn, Fe, Mg, lanthanum (La), cerium (Ce), Sr, and V; Q is at least one selected from titanium (Ti), molybdenum (Mo), and Mn; I′ is at least one selected from Cr, V, Fe, scandium (Sc), and yttrium (Y); and J is at least one selected from V, Cr, Mn, Co, Ni, and copper (Cu).

The cathode active materials represented by Formulae above may further have a coating layer on their surfaces. The coating layer may include a coating element compound, such as an oxide of a coating element, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The coating element compounds may be amorphous or crystalline. The coating element included in the coating layer may be at least one selected from Mg, Al, Co, potassium (K), sodium (Na), calcium (Ca), silicon (Si), Ti, V, tin (Sn), germanium (Ge), gallium (Ga), boron (B), arsenic (As), and zirconium (Zr). In addition, a cathode active material layer may include a mixture of a cathode active material represented by one of the formulae above and having no coating layer and a cathode active material represented by one of the formulae above and further including a coating layer.

In another embodiment, the first and second electrode active material layers11band12bmay include an anode active material. Any suitable anode active material including those used in the art as an anode active material for secondary batteries may be used. The anode active material may be at least one selected from lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, and a carbonaceous material.

For example, the transition metal oxide may be a lithium titanium oxide, a vanadium oxide, a lithium vanadium oxide, or the like.

For example, the non-transition metal oxide may be SnO2, SiOxwhere 0<x<2, or the like.

For example, the carbonaceous material may comprise at least one selected from crystalline carbon and amorphous carbon. Examples of the crystalline carbon include natural graphite and artificial graphite that is in amorphous, plate, flake, spherical or fibrous form. Examples of the amorphous carbon include soft carbon (carbon calcined at low temperatures), hard carbon, meso-phase pitch carbides, calcined cokes, and the like.

In addition, the first and second electrode active material layers11band12bmay include a conductive agent. Examples of the conductive agent include carbon black, graphite particulates, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, metallic powders, fibers or tubes formed of copper, nickel, aluminum, silver, or the like, and conductive polymers such as polyphenylene derivatives, but the conductive agent is not limited to the above examples. For example, any suitable conductive material including those used in the art may be used.

In addition, the first and second electrode active material layers11band12bmay include a binder. Examples of the binder include a vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the polymers described above, and styrene butadiene rubber-based polymers.

Referring toFIG. 4, in an embodiment in which the first electrode plates11and11′ are anode plates and the second electrode plates12and12′ are cathode plates, the stacked electrode structure16may be prepared as follows.

For example, cathode plates12and12′ are prepared. A cathode active material composition is prepared by mixing a cathode active material, a conductive agent, a binder, and a solvent together. The cathode active material composition is directly coated onto at least one surface of a current collector12a, which may comprise aluminum, and dried to manufacture the cathode plates12and12′ with the cathode active material layer(s)12bformed thereon. In another embodiment, the cathode active material composition is cast onto a separate support and a film separated from the support is laminated on at least one surface of the current collector12awhich may comprise aluminum, to manufacture the cathode plates12and12′ with the cathode active material layer(s)12bformed thereon.

The cathode active material, the conductive agent, and the binder used in the manufacture of the cathode plates12and12′ may be the same as those used to manufacture the electrode plates described above. The solvent used to manufacture the cathode plates12and12′ may be at least one selected from N-methylpyrrolidone (NMP), acetone, water, or the like, but is not limited to the above examples. For example, any suitable solvent including solvents used in the art may be used. In some embodiments, the cathode active material composition may further include a plasticizer to form pores in the cathode plates12and12′.

The amounts of the cathode active material, the conductive agent, the binder, and the solvent used in the manufacture of the cathode plates12and12′ are the same levels as those used in general secondary batteries. At least one of the conductive agent, the binder, and the solvent may be omitted if desired. The secondary battery may be a lithium battery.

Next, anode plates11and11′ are prepared. The anode plates11and11′ may be manufactured using the same method as that used to manufacture the cathode plates12and12′, except that an anode active material is used instead of the cathode active material. When preparing an anode active material composition, a conductive agent, a binder, and a solvent that are the same as those used for the cathode plates12and12′ may be used.

For example, the anode active material composition is prepared by mixing an anode active material, a conductive agent, a binder, and a solvent together, and the anode active material composition is directly coated onto at least one surface of a Cu current collector to manufacture the anode plates11and11′. In another embodiment, the anode active material composition is cast onto a separate support and an anode active material film separated from the support is laminated on at least one surface of a Cu current collector to manufacture the anode plates11and11′. The amounts of the anode active material, the conductive agent, the binder, and the solvent used to manufacture the anode plates11and11′ can be determined by one of skill in the art without undue experimentation and thus are not further elaborated for clarity.

Next, the separators13to be disposed between the cathode plates12and12′ and the anode plates11and11′ are prepared. As the separators13, any suitable separator including those used in secondary batteries such as lithium batteries may be used. The separator may have low resistance to transfer of ions in an electrolyte and high electrolyte-retaining ability. Examples of the separator include glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), and combinations thereof, each of which may be a nonwoven fabric or a woven fabric. For example, in a lithium ion battery, a windable separator formed of polyethylene, polypropylene, or the like may be used. In a lithium ion polymer battery, a separator having a high ability to retain an organic electrolytic solution may be used.

The separators13may be manufactured according to the following method. For example, a separator composition may be prepared by mixing a polymer resin, a filler, and a solvent together. The separator composition may be directly coated onto a cathode plate or an anode plate and dried to form the separator13. In another embodiment, the separator composition may be cast onto a support and dried and a separator film separated from the support is laminated on an electrode to form the separator13.

The polymer used to prepare the separator13is not particularly limited, and any suitable materials used as binders for a cathode plate or an anode plate may be used. Examples of the polymer include a vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, and mixtures thereof, but the polymer resin is not limited to the above examples. For example, any suitable material for forming a separator, including those used in the art, may be used.

Subsequently, the separators13are disposed between the cathode plates12and12′ and the anode plates11and11′ to prepare the stacked electrode structure16. A first end of the stacked electrode structure16is fixed by the binding member14, thereby completing the manufacture of the electrode assembly10.

Referring toFIGS. 1 to 4, the electrochemical cell200may include the electrode assembly10including the stacked electrode structure16described above. In the electrode assembly10, the binding member14may be omitted.

Referring toFIGS. 1 to 4, the electrochemical cell200may be prepared as follows. For example, the electrochemical cell200may be a lithium battery.

First, the stacked electrode structure16is prepared as described above.

Next, the electrolyte30is prepared. For example, the electrolyte30may be an organic electrolytic solution. In some embodiments, the electrolyte30may be a solid electrolyte. The solid electrolyte may comprise a boron oxide, lithium oxynitride, or the like, but is not limited to the above examples. For example, any suitable solid electrolyte including those used in the art may be used. The solid electrolyte may be formed on the electrode plate or the separator by sputtering or the like.

For example, an organic electrolytic solution may be prepared as the electrolyte30. The organic electrolytic solution may be prepared by dissolving a lithium salt in an organic solvent.

Examples of the organic solvent include at least one selected from propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, and dimethyl ether, but the organic solvent is not limited to the above examples. For example, any suitable organic solvent for organic electrolytic solutions, including those that may be used in the art, may be used.

Examples of the lithium salt include at least one selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(CxF2x+1SO2)(CyF2y+1SO2) where x and y are natural numbers, LiCl, and LiI, but the lithium salt is not limited to the above examples. For example, any suitable lithium salt including those used in the art may be used.

Referring toFIGS. 1 to 4, the electrochemical cell200includes the electrode assembly10including the stacked electrode structure16. The electrode assembly10is impregnated with an organic electrolytic solution as the electrolyte30and then accommodated in a pouch100as a housing, and the resulting structure is sealed, thereby completing the manufacture of the electrochemical cell200. A plurality of electrochemical cells200may be stacked to form a battery pack, and such a battery pack may be used in any kinds of device benefiting from a flexible secondary battery. The electrochemical cell200may be used in, for example, wearable devices such as smart watches, and the like. A secondary battery may be an alkali metal battery. For example, the secondary battery may be a lithium secondary battery or a sodium secondary battery.

An embodiment will now be described in further detail with reference to the following examples and comparative examples. However, these examples are for illustrative purposes only and are not intended to limit the scope of the one or more embodiments.

EXAMPLES

Manufacture of Electrode Plate

Two multilayer sheets (manufactured by Dai Nippon Printing Co., Ltd.) each formed of polypropylene/aluminum/nylon and having an area of 60 millimeters (mm)×70 mm were stacked such that the polypropylene layers faced each other and then three edges of the stacked two multilayer sheets were bonded together by thermal bonding after 3 mm remained on each edge. 1 gram (g) of diethyl carbonate (DEC) was injected between the two multilayer sheets via the non-bonded edge thereof and the non-bonded edge was subjected to thermal bonding to form a fused sealing layer.

Subsequently, graphene powder (manufactured by Cheap tubes Inc.) was uniformly coated between the polypropylene layers positioned on the non-bonded 3 mm edge portions, followed by thermal bonding, to form a gas blocking layer, thereby completing the manufacture of a housing.

Example 2: Clay Nanostructures

A housing was manufactured in the same manner as in Example 1, except that a nanoclay (CLOISITE 15A, manufactured by Southern Clay) was used instead of the graphene powder.

A housing was manufactured in the same manner as in Example 1, except that silica (SiO2) nanoparticles (SI-OX-02-NP, manufactured by American Elements) were used instead of the graphene powder.

Example 4: Graphite Sheet (Used Instead of Al Layer)

A polypropylene sheet, a graphite sheet, and a nylon sheet, each of which had an area of 60 mm×70 mm, were sequentially stacked and then subjected to thermal bonding to form a multilayer sheet consisting of polypropylene/graphite/nylon layers.

Two multilayer sheets, each consisting of polypropylene/graphite/nylon layers, were stacked such that the polypropylene layers faced each other and then three edges of the stacked two multilayer sheets were bonded together by thermal bonding after 3 mm remained on each edge. 1 g of DEC was injected between the two multilayer sheets via the non-bonded edge thereof and the non-bonded edge was subjected to thermal bonding to form a fused sealing layer.

Subsequently, graphene powder (manufactured by Cheap tubes Inc.) was uniformly coated between the polypropylene layers positioned on the non-bonded 3 mm edge portions, followed by thermal bonding, to form a gas blocking layer, thereby completing the manufacture of a housing.

Comparative Example 1

A housing was manufactured in the same manner as in Example 1, except that a gas blocking layer was formed by thermal bonding without using the graphene powder.

Evaluation Example 1: Moisture Transmission Rate Evaluation

The housings manufactured according to Examples 1 to 4 and Comparative Example 1 were put in an isothermal-isohumidity chamber at 60° C. and a relative humidity of 85%, maintained therein for 5 days to 7 days, and then taken out of the chamber, and moisture content in each housing was measured using a Karl-Fischer moisture meter. A part of the measurement results is shown in Table 1 below.

As shown in Table 1 above, moisture content in the housing of Example 1 decreased by 17% or more as compared to the housing of Comparative Example 1. Such moisture content reduction is attributed to further including a gas blocking layer including nanostructures on edge portions of a housing according to an embodiment, which suppresses permeation of moisture into the housing.

As is apparent from the foregoing description, according to an embodiment, an electrochemical cell including a gas blocking layer including nanostructures has enhanced gas blocking characteristics.