Patent Description:
Comparing to the current non-lithium battery system, the lithium battery system has advantages of high operation voltage (up to <NUM>. 6V), high energy density (up to 120Wh/kg), light weight, longer cycle life, friendly to the environment and so on. According to the researching history of the lithium battery system, the earliest lithium battery developed is the rechargeable lithium metal battery which has pretty high energy density but meanwhile has serious issues of stability and safety because of the high chemical reacting ability to the electrolyte. Considering the safety issue of the lithium metal battery system, the developments of the rechargeable lithium battery gradually focus on replacing the organic solvent with the polymer electrolyte.

Patent application <CIT> relates to a lithium metal electrode and its related lithium metal battery, comprising a current collector, a lithium metal layer, an insulation frame, a porous electrical insulation layer and an ionic diffusion layer.

As for the performances of the battery system, except for the safety requirement, it is crucial to ensure that the capacity of the battery system is enough for supporting the operation duration of the device. Consequently, the capacity of the battery system becomes the important developing issue again. In the past, the development of the lithium metal battery system was suspended due to its safety issue. Comparing to the lithium-ion and the lithium polymer systems, the energy density of the lithium metal system is much higher than other systems. However, because the lithium metal has high chemical activity, an extreme oxidation-reduction reaction occurs if the lithium metal is not stored or operated under the proper condition. Practically, the lithium metal battery system is quite suitable for the current smart electrical device only if the issues of safety, processing and storage of the lithium metal can be conquered.

Therefore, how to overcome the technical bottleneck that has always existed in the lithium metal battery system has become the focus of the battery system manufacturers. For example, during the charging process, the lithium metal is not uniformly deposited on the surface of the electrode, which leads to the rapid deposition in some portions and the formation of dendritic crystals, which are called lithium dendrites. When the lithium dendrites gradually grow, they may break to form dead lithium resulting in irreversible capacity losses. More seriously, the lithium dendrites may pierce through the separator, causing internal short circuits and battery explosions. Moreover, because lithium is an extremely reactive material, it may react with the electrolyte to consume active lithium and cause potential safety issues.

Accordingly, a lithium electrode is provided to overcome the above problems.

The present invention is defined by appended claim <NUM>. Preferred embodiments are defined by the appended dependent claims.

It is an objective of this invention to provide a lithium electrode. The lithium dendrites are constrained to plate in a specific region by the arrangement of the electrically conductive structure layer and the solid electrolyte layer.

It is an objective of this invention to provide a lithium electrode. The solid electrolyte layer and the electrolyte storage layer, which is disposed above the solid electrolyte layer efficiently inhibit the height of plating of the lithium dendrite during charging due to the structural strength thereof. The lithium dendrite will mainly plate horizontally to prevent to penetrate through the electrical insulator, i.e. the separator, to avoid inner shorting. Meanwhile, the lithium dendrites are constrained to plate toward the vertical direction so that the thickness of the battery will not vary extremely.

It is another objective of this invention to provide a lithium electrode. By the arrangement of the porous covering layer, the electrolyte storage layer and the solid electrolyte layer, the lithium dendrites only can push the solid electrolyte layer toward the electrolyte storage layer during plating and stripping of the lithium dendrites. The electrolyte storage layer would be pressed or released to make the liquid or gel electrolyte impregnated therein outflow and inflow. The liquid or gel electrolyte impregnated in the electrolyte storage layer does not contact to the negative active material, the lithium metal layer, to avoid the liquid or gel electrolyte being decomposed and reduce the irreversible capacity losses.

In order to implement the abovementioned, this invention discloses a lithium electrode, which includes an electrically conductive structure layer, a lithium metal layer, a solid electrolyte layer, an electrolyte storage layer and a porous covering layer. The electrically conductive structure layer has at least one recess with one-side opening and an inner surface of the recess has at least one electrically conductive region and at least one electrically insulating region. The lithium metal layer is disposed in the recess of the electrically conductive structure layer and contacts to the electrically conductive region. The solid electrolyte layer and the electrolyte storage layer are disposed thereon sequentially. The porous covering layer is disposed on the electrically conductive structure layer to cover the opening of the recess. By this arrangement, the electrolyte storage layer impregnated with the liquid or gel electrolyte does not contact to the lithium metal layer, due to the existence of the solid electrolyte layer. Moreover, when the lithium dendrites are grown from the lithium metal layer, the lithium dendrites would be directly suppressed by the solid electrolyte layer. Also, the solid electrolyte layer is constrained by the electrolyte storage layer disposed above. Therefore, the lithium dendrites only can push the solid electrolyte layer toward and press the electrolyte storage layer. The lithium dendrites will be constrained to plate in a specific region and mainly plate horizontally. The electrical insulator, i.e. the separator, would not be penetrated through by the lithium dendrites to avoid inner shorting.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter.

The present invention will become more fully understood from the detailed description given hereinbelow illustration only, and thus are not limitative of the present invention, and wherein:.

This invention discloses a lithium electrode. Please refer to <FIG>, which is a schematic diagram of the lithium electrode of this invention. The lithium electrode <NUM> of this invention includes an electrically conductive structure <NUM>, a lithium metal layer <NUM>, a solid electrolyte layer <NUM>, an electrolyte storage layer <NUM> and a porous covering layer <NUM>. The electrically conductive structure layer <NUM> has at least one recess <NUM> with one-side opening. Please also refer to <FIG>, which is a schematic diagram of the electrically conductive structure layer of the lithium electrode according to <FIG> of this invention. The width of the opening of the recess <NUM> is greater than <NUM> or not less than <NUM> micrometers, preferably. The maximum available value is depended on the active range of the battery. Also, the depth of the recess <NUM> ranges from <NUM> to <NUM> micrometers.

The inner surface of the recess <NUM> has at least one electrically conductive region <NUM> and at least one electrically insulating region <NUM>. The lithium metal layer <NUM> is disposed in the recess <NUM> of the electrically conductive structure layer <NUM> and contacts to the electrically conductive region <NUM>. The thickness of the lithium metal layer <NUM> ranges from <NUM> to <NUM> micrometers. The solid electrolyte layer <NUM> is movably disposed in the recess <NUM> of the electrically conductive structure layer <NUM>. The bottom of the solid electrolyte layer <NUM> covers and contacts to the lithium metal layer <NUM>, and the sides of the solid electrolyte layer <NUM> are contacted with the electrically insulating region <NUM>. The electrolyte storage layer <NUM> is disposed in the recess <NUM> of the electrically conductive structure layer <NUM>. The bottom of the electrolyte storage layer <NUM> covers and contacts to the solid electrolyte layer <NUM>, and the sides of the electrolyte storage layer <NUM> are contacted with the electrically insulating region <NUM>. The porous covering layer <NUM> is disposed on the electrically conductive structure layer <NUM> to cover the opening of the recess <NUM> of the electrically conductive structure layer <NUM>. The porous covering layer <NUM> has a plurality of through holes to allow lithium ions to pass. An adhesive layer <NUM> is disposed between the electrically conductive structure layer <NUM> and the porous covering layer <NUM> to adhere the porous covering layer <NUM> to the electrically conductive structure layer <NUM>.

The liquid and/or gel electrolyte are impregnated in the electrolyte storage layer <NUM>. The material of the solid electrolyte layer <NUM> may be any solid electrolyte series, such as oxide-based solid electrolyte, sulfide-based solid electrolyte, lithium-aluminum alloy solid electrolyte or lithium azide (LiN<NUM>) solid electrolyte, which may be crystalline or glassy. In this invention, the lithium metal layer <NUM> and the electrolyte storage layer <NUM> are separated by the solid electrolyte layer <NUM>. Therefore, the unnecessary contact between the liquid or gel electrolyte impregnated in the electrolyte storage layer <NUM> and the active material, the lithium metal layer <NUM> are reduced or avoided. The unnecessary consumption for the lithium ions are also reduced or avoided to prevent the performance attenuation of the lithium batteries. Hence, it is preferably that the lithium metal layer <NUM> is completely covered by the solid electrolyte layer <NUM>. The side edges of the solid electrolyte layer <NUM> abuts against the side walls of the recess <NUM> to reduce or avoid the unnecessary contact between the liquid or gel electrolyte impregnated in the electrolyte storage layer <NUM> and the lithium metal layer <NUM>.

The lithium metal layer <NUM> is disposed at the bottom of the recess <NUM>. Therefore, the bottom of the recess <NUM> is the electrically conductive region <NUM>. When the lithium electrode <NUM> is assembled as a battery, the electricity generated during the electrochemical reaction is outputted from the electrically conductive region <NUM>. It is necessary that the electrically conductive region <NUM> is with an electrical conductive path between the inside and the outside of the battery. The solid electrolyte layer <NUM> and the electrolyte storage layer <NUM> have to contact with the electrically insulating region <NUM> of the recess <NUM>. Therefore, the side walls of the recess <NUM> are the electrically insulating region <NUM>.

Moreover, the shape of the recess <NUM> of the electrically conductive structure layer <NUM> is not limited. As shown in <FIG>, the side walls of the recess <NUM> is, but not limited to, vertical. Excepting for the above-mentioned requirements, it has to be considered that the solid electrolyte layer <NUM> is moveable to suppress the growth of the lithium dendrites, which only can push the solid electrolyte layer <NUM> to press the electrolyte storage layer <NUM>. A more detailed description of the present invention is presented below. Therefore, the side walls, for arrangement of the solid electrolyte layer <NUM>, of the recess <NUM> are preferably smooth and equidistant.

For the electrically conductive structure layer <NUM>, two embodiments are provided and described in detail with respect to the drawings.

Please refer to <FIG>, which is a schematic diagram of a first embodiment of the electrically conductive structure layer of the lithium electrode of this invention. In this embodiment, an electrically conductive element <NUM> is the main body of the electrically conductive structure layer <NUM>. An electrically insulating element <NUM> is disposed directly on the top surface of the electrically conductive element <NUM>. The electrically insulating element <NUM> has at least one through hole <NUM>. Parts of the electrically conductive element <NUM> are exposed from the through hole <NUM>. Therefore, the recess <NUM> with one-side opening is formed thereof. The bottom 111b of the recess <NUM> is formed by the electrically conductive element <NUM> to be defined as the electrically conductive region <NUM>. The side wall 111w of the recess <NUM> is formed by the electrically insulating element <NUM> to be defined as the electrically insulating region <NUM>. The lithium electrode <NUM> constructed by the electrically conductive structure layer <NUM> based on the first embodiment is illustrated in <FIG>. The bottom 111b of the recess <NUM> is formed by the electrically conductive element <NUM>. Therefore, an electrical conductive path between the inside and the outside of the battery can be formed to output the electricity generated thereof. That means the electrically conductive element <NUM> serving the current collector of the lithium electrode <NUM>. The material of the electrically conductive element <NUM> may be metal or any other electrically conductive materials, such as copper, nickel, steel or any combinations thereof.

The material of the electrically insulating element <NUM> may be insulating polymer material, insulating ceramic material, insulating glass material, insulating glass fiber material and any combinations thereof. The insulating polymer material includes polyimide, polyethylene terephthalate, polyurethane, polyacrylate, epoxy or silicone. The insulating glass fiber material may be FR4-class, such as FR4 epoxy glass fiber material.

Then please refer to <FIG>, which is a schematic diagram of a second embodiment of the electrically conductive structure layer of the lithium electrode of this invention, and a schematic diagram of the lithium electrode based on the second embodiment of the electrically conductive structure layer shown in <FIG> of this invention respectively. The electrically conductive structure layer <NUM> of this second embodiment also includes an electrically conductive element <NUM> and an electrically insulating element <NUM>. More specifically, the electrically conductive element <NUM> has a blind hole 101b to form the recess <NUM> directly. The electrically insulating element <NUM> is disposed on a side wall of the blind hole 101b to be defined as the electrically insulating region <NUM>. A bottom of the blind hole 101b is uncovered by the electrically insulating element <NUM> and defined as the electrically conductive region <NUM>. Similar, the electrically conductive element <NUM> is the main body of the electrically conductive structure layer <NUM>. The uncovered bottom of the recess <NUM> is formed by the electrically conductive element <NUM>. Therefore, an electrical conductive path between the inside and the outside of the battery can be formed to output the electricity generated by the battery constructed by lithium electrode <NUM>. Also, the electrically conductive element <NUM> can be regarded as the current collector of the lithium electrode <NUM>.

Please refer to <FIG>, <FIG> and <FIG>, the electrolyte storage layer <NUM> contacts and covers the solid electrolyte layer <NUM>. When the electrolyte storage layer <NUM> is filled in the recess <NUM>, the top surface of the electrolyte storage layer <NUM> is substantially aligned with the top surface of the electrically conductive structure layer <NUM>. In other words, the remaining space is filled by the electrolyte storage layer <NUM>. The electrolyte storage layer <NUM> is used to impregnate with the liquid and/or gel electrolyte. In this invention, the lithium metal layer <NUM> and the electrolyte storage layer <NUM> are separated by the solid electrolyte layer <NUM>. Therefore, the unnecessary contact between the liquid or gel electrolyte impregnated in the electrolyte storage layer <NUM> and the active material (i.e. the lithium metal layer <NUM>) are reduced or avoided. The unnecessary consumption for the lithium ions are also reduced or avoided to prevent the performance attenuation of the lithium batteries.

The electrolyte storage layer <NUM> is porous to impregnate with the liquid and/or gel electrolyte. The material of the electrolyte storage layer <NUM> may be polymer material, ceramic material, glass material, fiber material and any combinations thereof. The porous structure of the electrolyte storage layer <NUM> is formed by stacked particles and/or crossed fibers. The particles include ceramic particles, polymer particles and/or glass particles. The fibers include polymer fibers and/or glass fibers.

The porous covering layer <NUM> is adhered to the electrically conductive structure layer <NUM> to cover the opening of the recess <NUM>. The porous covering layer <NUM> has a plurality of through holes to allow lithium ions and the electrolyte to pass for the electrochemical reactions. The through holes may be linear or non-linear (ant holes) formed by chemical or mechanical processes. Moreover, the porous covering layer <NUM> may be made of porous materials to offer the through holes.

Further, please refer to <FIG>, the adhesive layer <NUM>, located between the electrically conductive structure layer <NUM> and the porous covering layer <NUM>, and the electrically insulating element <NUM> are integrated into an electrically insulating glue frame <NUM>. As shown in the drawing, the electrically insulating glue frame <NUM> is formed between the porous covering layer <NUM> and the electrically conductive element <NUM>. The electrically insulating glue frame <NUM> located on the side walls of the recess <NUM> is used for the electrically insulating element <NUM> to define as the electrically insulating region <NUM>. The electrically insulating glue frame <NUM> located between the electrically conductive structure layer <NUM> and the porous covering layer <NUM> is used to adhere the electrically conductive structure layer <NUM> and the porous covering layer <NUM>. The material of the electrically insulating glue frame <NUM> is selected from the group consisting of thermosetting polymer, thermoplastic polymer and any combinations thereof. The thermosetting polymer is selected from the group consisting of silicone, epoxy, acrylic acid resin and any combinations thereof and the thermoplastic polymer is selected from the group consisting of polyethylene, polypropylene, thermoplastic polyimide, thermoplastic polyurethane and any combinations thereof. Due to the liquid or gel electrolyte is adapted, the material of the electrically insulating glue frame <NUM> is preferably selected from the electrolyte-inert material, such as silicone, polyethylene, polypropylene, thermoplastic polyimide and so on. Therefore, the electrically insulating glue frame <NUM> will not react with the electrolyte to maintain the adhesion ability.

Also, for the embodiment shown in <FIG>, the adhesive layer <NUM> and the electrically insulating element <NUM> may be integrated into an electrically insulating glue frame <NUM>. The electrically insulating glue frame <NUM> is used for the electrically insulating element <NUM> of the recess <NUM> and is used to adhere the electrically conductive structure layer <NUM> and the porous covering layer <NUM>. Moreover, excepting for the single-layered structure shown in the drawings, the electrically insulating glue frame <NUM> may be multi-layered structure. With the modification of the adhesive material, the adhesive will be better.

In general, when the lithium metal is plated, the lithium dendrites will grow vertically. With the arrangement of this invention, the growth of the lithium dendrites is constrained by the solid electrolyte layer <NUM>. The vertical growth of the lithium dendrites will push the solid electrolyte layer <NUM>. The solid electrolyte layer <NUM> is moveably disposed in the recess <NUM>. Therefore, the solid electrolyte layer <NUM> is pushed to move toward the electrolyte storage layer <NUM>. Due the porous covering layer <NUM> is adhered on the electrically conductive structure layer <NUM> firmly, the movement range of the solid electrolyte layer <NUM> is limited. The electrolyte storage layer <NUM> is porous to store the liquid and/or gel electrolyte. Also, the electrolyte storage layer <NUM> is compressible. When the electrolyte storage layer <NUM> is pressed by the solid electrolyte layer <NUM>, the electrolyte storage layer <NUM> will be deformed to squeeze out parts of the liquid and/or gel electrolyte impregnated therein. Also, the compressibility of the electrolyte storage layer <NUM> is limited. As the compression distance increases, the resistive force to compress the electrolyte storage layer <NUM> will become larger to inhibit the vertical growth of the lithium dendrites. The lithium dendrites are forced to grow in a horizontal direction. The penetration through issue for the electrical insulator, i.e. the separator, caused by the lithium dendrites can be eliminated to avoid inner shorting. When the lithium metal is striped, the solid electrolyte layer <NUM> will move back to the original position and the electrolyte storage layer <NUM> will recover to the original state. The squeezed-out liquid and/or gel electrolyte will flow back to be impregnated in the electrolyte storage layer <NUM>.

Further materials illustrations for the solid electrolyte layer <NUM> are described below. The sulfide -based solid electrolyte may be selected from one or more of the groups consisting of a glassy state of Li<NUM>S-P<NUM>S<NUM>, a crystalline state of Lix'My'PSz', and a glassy ceramic state of Li<NUM>S-P<NUM>S<NUM>. wherein M is selected from one or more of the groups consisting of Si, Ge, and Sn; <MAT>.

Preferably, the glassy state of Li<NUM>S-P<NUM>S<NUM> may be selected from one or more of the groups consisting of glassy state of 70Li<NUM>S-30P<NUM>S<NUM>, glassy state of 75Li<NUM>S-25P<NUM>S<NUM>, and glassy state of 80Li<NUM>S-20P<NUM>S<NUM>. The glassy ceramic state of Li<NUM>S-P<NUM>S<NUM> may be selected from one or more of the groups consisting of glassy ceramic state of 70Li<NUM>S-30P<NUM>S<NUM>, glassy ceramic state of 75Li<NUM>S-25P<NUM>S<NUM>, and glassy ceramic state of 80Li<NUM>S-20P<NUM>S<NUM>. The crystalline state of Lix'My'PSz' may be selected from one or more of the groups consisting of Li<NUM>PS<NUM>, Li<NUM>SnS<NUM>, Li<NUM>GeS<NUM>, Li<NUM>SnP<NUM>S<NUM>, Li<NUM>GeP<NUM>S<NUM>, Li<NUM>SiP<NUM>S<NUM>, Li<NUM>GeP<NUM>S<NUM>, Li<NUM>P<NUM>S<NUM>, L<NUM>4Si<NUM>P<NUM>S<NUM>Cl<NUM>, B-Li<NUM>PS<NUM>, Li<NUM>P<NUM>SI, Li<NUM>P<NUM>S<NUM>, <NUM>. 4LiI-<NUM>. 6Li<NUM>SnS<NUM>, and Li<NUM>PS<NUM>Cl.

The oxide-based solid electrolyte may be a fluorite structure oxide-based solid electrolyte. For example, it may be yttria stabilized zirconia (YSZ) with molar fraction <NUM>-<NUM>%. The oxide-based solid electrolyte may be a ABO<NUM> oxide-based solid electrolyte, such as doping LaGaO<NUM>. Or, the oxide-based solid electrolyte may be Li<NUM>+x+y(Al, Ga)x (Ti, Ge)<NUM>-xSiyP<NUM>-yO<NUM> with crystalline structure, where <NUM>≦x≦<NUM> and <NUM>≦y≦<NUM>. Moreover, the oxide-based solid electrolyte may be Li<NUM>O-Al<NUM>O<NUM>-SiO<NUM>-P<NUM>O<NUM>-TiO<NUM>, Li<NUM>O-Al<NUM>O<NUM>-SiO<NUM>-P<NUM>O<NUM>-TiO<NUM>-GeO<NUM>, Na<NUM>Zr<NUM>La<NUM>Si<NUM>PO<NUM>, Li<NUM>Si<NUM>P<NUM>O<NUM>, Li3xLa<NUM>/3xTiO<NUM>, Li<NUM>La<NUM>Zr<NUM>O<NUM>, Li<NUM>La<NUM>Ti<NUM>Al<NUM>O<NUM>, or Li<NUM>LaTiO<NUM>.

The side walls, for arrangement of the solid electrolyte layer <NUM>, of the recess <NUM> of the electrically conductive structure layer <NUM> are smooth and equidistant. Therefore, the solid electrolyte layer <NUM> will be move upward and downward smoothly during plating and striping of the lithium metal.

When adapting for the battery system, referring to <FIG>, the electrically conductive structure layer <NUM> of the lithium electrode <NUM> includes a plurality of recesses <NUM>. The porous covering layer <NUM> serves as a separator. The positive active material layer <NUM> and the positive current collector <NUM> are disposed thereon sequentially. The electrically insulating glue frames <NUM> of the adjacent recesses <NUM> are connected, and the electrically insulating glue frames <NUM> in the side edges are adhered with the first adhesive layer <NUM> and the second adhesive layer <NUM> to the positive current collector <NUM> to form the package for the battery system. The materials of the first adhesive layer <NUM> and the second adhesive layer <NUM> may be the same with the material of the electrically insulating glue frames <NUM>. Also, the recess <NUM> in the <FIG> is only illustrated as a blind hole, such as shown in <FIG>. However, it is not limited that the recess <NUM> only can be a blind hole. The electrically conductive structure layer <NUM>, shown in <FIG>, or the combinations thereof can also be adapted. Further, the size, location, distance or the distribution of the recess <NUM> may be varied.

Please refer to <FIG>, one or more recess <NUM>, especially located in middle portion or any locations which the adhesive is poor, may have a separate adhesive structure to improve adhesive. The separate electrically insulating glue frame <NUM> is also adhered with the first adhesive layer <NUM> and the second adhesive layer <NUM> to the positive current collector <NUM> to form the package for the battery system. As shown in <FIG>, all the electrically insulating glue frames <NUM> of the recesses <NUM> are separate, and the separate first adhesive layers <NUM> and the separate second adhesive layers <NUM> are adhered to the positive current collector <NUM> to extremely improve adhesive thereof.

Claim 1:
A lithium electrode (<NUM>), comprising:
an electrically conductive structure layer (<NUM>), having at least one recess (<NUM>) with one-side opening and an inner surface of the recess having at least one electrically conductive region (<NUM>) and at least one electrically insulating region (<NUM>);
a lithium metal layer (<NUM>), disposed in the recess (<NUM>) of the electrically conductive structure layer (<NUM>) and contacting to the electrically conductive region (<NUM>); and
a porous covering layer (<NUM>), disposed on the electrically conductive structure layer (<NUM>) and having a plurality of through holes to allow lithium ions and the electrolyte to pass
characterized in that it further comprises:
a solid electrolyte layer (<NUM>), movably disposed in the recess (<NUM>) of the electrically conductive structure layer (<NUM>), and covering and contacting to the lithium metal layer (<NUM>); and
an electrolyte storage layer (<NUM>), disposed in the recess (<NUM>) of the electrically conductive structure layer (<NUM>) and covering the solid electrolyte layer (<NUM>), wherein the electrolyte storage layer (<NUM>) contains a liquid or gel electrolyte.