Thin film lithium-ion battery

A multi-cell battery includes a negative current collecting substrate; at least two laminated electric cores arranged in parallel to each other on the negative current collecting substrate; and a positive current collecting substrate, wherein the two laminated electric cores sandwiches about the positive current collecting substrate, thereby forming two cells on opposite sides of the positive current collecting substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to batteries. More particularly, the present invention relates to a thin film lithium-ion battery.

2. Description of the Prior Art

Lithium-ion secondary batteries or lithium-ion batteries have been used as power supplies for personal computers, portable devices such as cell phones, cameras, electric tools, and the like. In secondary batteries, the electron producing and consuming reactions are for the most part reversible, and therefore such a battery can be cycled between a charged and discharged state electrochemically.

When the rechargeable battery is charged, ions formed of the cathode material pass from the cathode through the electrolyte to the anode, and when the battery is discharged these ions travel back from the anode through the electrolyte to the cathode. For example, in batteries having a cathode comprising lithium, such as a LiCoO2or LiMnO2cathode, lithium species originating from the lithium-containing cathode travel from the cathode to the anode and vice versa during the charging and discharging cycles, respectively.

FIG. 1illustrates a conventional structure of a lithium-ion battery. As shown inFIG. 1, the lithium-ion battery1includes an electrochemical cell comprising an anode active material layer11disposed on one side surface of a separator10, a cathode active material layer21disposed on the other side surface of the separator10, an anode current collector12, and a cathode current collector22. The separator10may be made of polymers such as polyimide (PI), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC) or polycarbonate (PC) having porous structure to only allow the passage of the lithium ions, while preventing internal shorting between the anode active material layer11and the cathode active material layer21. To electrically connect the anode current collector12and the cathode current collector22to an external circuit or device, the lithium-ion battery1may further include two outwardly extended tabs12aand22a.

Typically, the separator10, the anode active material layer11and the cathode active material layer21are wetted with a liquid electrolyte solution or gel electrolyte. The electrochemical cell is typically enclosed in a parallelepipedic metal case20such as an aluminum case in a gas-tight manner with a sealant layer24securely sealing a gap between the tabs12aand22a.

FIG. 2illustrates another form of a lithium-ion battery known in the art. As shown inFIG. 2, the lithium-ion battery3is integrated with a circuit substrate30such as a copper clad laminate (CCL) substrate. The base dielectric of the CCL substrate may include polyimide (PI), polyethylene terephthalate (PET) or glass fiber. The circuit substrate30includes a separator portion30ahaving therein a plurality of through holes or porous structures for the passage of lithium ions. The separator portion30ais sandwiched by a pair of electrodes41and51. A current collector42is disposed directly on a top surface of the electrode41. The electrode41is sealed by a packaging unit43. Likewise, a current collector52is disposed directly on a top surface of the electrode51. The electrode51is sealed by a packaging unit53. Both of the current collectors42and52are typically made of expensive CCL substrates. The use of CCL substrates increases manufacturing cost/complexity and battery weight.

Portable electronic devices have been progressively reduced in size and weight and improved in performance. It is therefore required to develop a rechargeable lithium-ion battery or lithium-ion secondary cell having a high energy density and a high output, which is also cost-effective. Further, after being stored or circled for certain numbers, gas may be generated in lithium-ion batteries, especially at high temperature, which will reduce life span of the lithium-ion battery. What is needed, therefore, is to provide a lithium-ion battery which has desirable life span.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an improved thin film battery that is cost-effective, and has simple structure, high capacity, desirable life span and cycle performance.

Another object of the present invention is to provide a thin film battery with improved ability of gas resistance and moisture resistance.

According to one embodiment, a thin film lithium-ion battery unit includes a positive current collecting substrate, a positive electrode active material layer coated on an inner surface of the positive current collecting substrate, a negative current collecting substrate, a negative electrode active material layer coated on an inner surface of the negative current collecting substrate, a separator sandwiched between the positive electrode active material layer and the negative electrode active material layer, and electrolyte retained at least in the separator. The positive electrode active material layer, the separator and the negative electrode active material layer constitute a laminated electric core.

An outer conductive frame is provided to encompass the positive electrode active material layer with a gap formed therebetween. The outer conductive frame is substantially flush with the positive current collecting substrate. According to one embodiment of the present disclosure, the outer conductive frame may have an opening for accommodating a positive tab that juts out from an edge of the positive current collecting substrate. According to one embodiment of the present disclosure, the outer conductive frame may have a protruding negative tab. A glue layer may be provided to fill the gap.

According to another aspect of the invention, a stack structure of a thin-film lithium-ion battery includes an intermediate current collecting substrate having a first surface and a second surface opposite to the first surface; a first laminated electric core laminated on the first surface; a first current collecting substrate laminated on the first laminated electric core, wherein the intermediate current collecting substrate, the first laminated electric core, and the first current collecting substrate constitute a first battery unit; a second laminated electric core laminated on the second surface; a second current collecting substrate laminated on the second laminated electric core, wherein the intermediate current collecting substrate, the second laminated electric core, and the second current collecting substrate constitute a second battery unit; a first sealant layer sealing the first laminated electric core; and a second sealant layer sealing the second laminated electric core.

According to still another aspect of the invention, a multi-cell battery includes a negative current collecting substrate; at least two laminated electric cores arranged in parallel to each other on the negative current collecting substrate; and a positive current collecting substrate, wherein said negative current collecting substrate is a folded substrate such that the two laminated electric cores sandwiches about the positive current collecting substrate, thereby forming two cells on opposite sides of the positive current collecting substrate.

It should be noted that all the figures are diagrammatic. Relative dimensions and proportions of parts of the drawings are exaggerated or reduced in size, for the sake of clarity and convenience. The same reference signs are generally used to refer to corresponding or similar features in modified and different embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are given to provide a thorough understanding of the invention. It will, however, be apparent to one skilled in the art that the invention may be practiced without these specific details. Furthermore, some well-known system configurations and process steps are not disclosed in detail, as these should be well-known to those skilled in the art.

Likewise, the drawings showing embodiments of the apparatus are semi-diagrammatic and not to scale and some dimensions are exaggerated in the figures for clarity of presentation. Also, where multiple embodiments are disclosed and described as having some features in common, like or similar features will usually be described with like reference numerals for ease of illustration and description thereof.

The following sets forth a detailed description of a mode for carrying out the invention. The description is intended to be illustrative of the invention and should not be taken to be limiting. It is understood that present invention may be applicable to both primary batteries and secondary batteries, although some embodiments take the secondary battery as an example.

Please refer toFIG. 3andFIG. 4.FIG. 3is a schematic top view of an exemplary thin-film lithium-ion battery according to one embodiment of the invention.FIG. 4is a cross-sectional diagram taken along line I-I′ inFIG. 3. As shown inFIG. 3andFIG. 4, the lithium-ion battery unit100comprises a positive current collecting substrate102, a positive electrode active material layer111coated on an inner surface of the positive current collecting substrate102, a negative current collecting substrate104, a negative electrode active material layer113coated on an inner surface of the negative current collecting substrate104, a separator112sandwiched between the positive electrode active material layer111and the negative electrode active material layer113, and electrolyte (not explicitly shown) retained at least in the separator112. The positive electrode active material layer111, the separator112and the negative electrode active material layer113constitute a laminated electric core110. The separator112between the positive and negative electrodes prevents physical contact of the electrodes while enabling ionic transport.

An outer conductive frame105, which is spaced apart from the positive current collecting substrate102, may be provided to encompass the positive current collecting substrate102with a gap125formed therebetween. The outer conductive frame105is substantially flush or coplanar with the positive current collecting substrate102. The outer conductive frame105and the positive current collecting substrate102are formed in the same horizontal level. According to one embodiment of the present disclosure, the outer conductive frame105is not a closed loop shaped frame and may have an opening115for accommodating a positive tab102athat juts out from an edge of the positive current collecting substrate102. According to one embodiment of the present disclosure, the outer conductive frame105may have a protruding negative tab105a. A glue layer130may be provided to fill the gap125. The glue layer130is flush with a covering insulation layer132that covers the outer conductive frame105and the positive current collecting substrate102. On the bottom surface of the negative current collecting substrate104, a covering insulation layer142may be provided. The covering insulation layers132and142may comprise polyimide (PI), polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyurethane (PU), or polyethylene terephthalate (PET), but not limited thereto. The laminated electric core110may be sealed by a sealant layer122provided along the periphery of the laminated electric core110between the positive current collecting substrate102and the negative current collecting substrate104. A conductor layer124may be provided adjacent to the sealant layer122by using welding, soldering, or any suitable techniques.

According to one embodiment of the present disclosure, the outer conductive frame105may be electrically coupled to the underlying negative current collecting substrate104through the conductor layer124. However, in another embodiment, the layer124may be composed of non-conductive materials such as an adhesive material. It is to be understood that other approaches may be used to accomplish the electrical connection between the negative current collecting substrate104and the outer conductive frame105.

FIG. 5AandFIG. 5Bshow such embodiment. As shown inFIGS. 5A and 5B, the periphery of the laminated electric core110between the positive current collecting substrate102and the negative current collecting substrate104is sealed by using only the sealant layer122. To electrically connect the negative current collecting substrate104with the outer conductive frame105, an extension portion105bof the outer conductive frame105and an extension portion104bof the negative current collecting substrate104may be provided. A conductive layer126may be applied between the extension portion105band the extension portion104bto electrically connect the negative current collecting substrate104with the outer conductive frame105.

The shape of the battery cell as set forth in the figures is only for illustration purposes. It is not necessary that the outline of the battery cell has a rectangular shape as depicted inFIGS. 3 and 5A. In other embodiments, the outline of the battery cell may have an irregular shape, when viewed from the above, as shown inFIG. 8A.FIG. 8Bshows a battery cell having an irregular shape and outline. In addition, a through opening310may be provided. The through opening310extends through the entire thickness of the battery cell.

FIG. 9andFIG. 10illustrate another embodiment of the present invention, whereinFIG. 10is a cross-sectional view taken along line II-II′ ofFIG. 9. As shown inFIG. 9andFIG. 10, the outer conductive frame105is a closed loop. An interconnect layer154is formed on the covering insulation layer132and is electrically connected to the positive current collecting substrate102through the via plug152. The via plug152may comprise conductive pastes, plated copper, solder pastes or other suitable conductive materials known in the art. The interconnect layer154may extend beyond the outer conductive frame105to form a positive connecting tab154a. Likewise, the outer conductive frame105may also extend beyond the edge of the cell to form a negative connecting tab105a. The positive connecting tab154aand the negative connecting tab105aform a battery terminal pair.

It is to be understood that the number of the battery terminal pair depends upon the design requirements and one battery cell may have multiple battery terminal pairs. As shown inFIG. 11, the battery cell comprises two battery terminal pairs150and160. The battery terminal pair150comprises positive connecting tab154aand the negative connecting tab105a. Likewise, as previously described, the positive connecting tab154aof the interconnect layer154is formed on the covering insulation layer132and is electrically connected to the positive current collecting substrate102through the via plug152. The battery terminal pair160comprises positive connecting tab164aand the negative connecting tab105b. The positive connecting tab164aof the interconnect layer164is formed on the covering insulation layer132and is electrically connected to the positive current collecting substrate102through the via plug162. In addition to the interconnect layers154and164, it is to be understood that other circuit patterns or circuit elements may also be formed on the covering insulation layer132.

The glue layer130is optional. For example, inFIG. 12A, the covering insulation layer132directly fills into the gap125. InFIG. 12B, the gap125is filled with the sealant layer122that is extruded when assembling the battery cell. InFIG. 12C, the glue layer130may protrude from an upper end of the gap125and covers a portion of the outer conductive frame105and a portion of the positive current collecting substrate102. InFIG. 12D, the glue layer130is covered by the covering insulation layer132.

According to one embodiment of the present disclosure, the lithium-ion battery100may have a thickness T ranging between 0.25 mm and 0.5 mm, but not limited thereto. In some cases that the battery100comprises folded cells, thickness may reach 2 mm.

The sealant layer122, in combination with the conductor layer124, satisfactorily protects the laminated electric core110from exposure to air or moisture. The disclosed structure provides high moisture-proof capability and insulating property.

FIGS. 6A-6Dshow some variations of the moisture-proof and air-proof packaging structure according to some embodiments of the invention.

As shown inFIG. 6A, an air gap123may be provided between the sealant layer122and the outer, peripheral conductor layer124. The air gap123may be vacuumed in one embodiment. According to another embodiment, dry air or dry inert gas may be filled into the air gap123.

Alternatively, as shown inFIG. 6B, the peripheral ends of the current collecting substrates may be pressed together or pressed toward each other to form a tapered cross-sectional profile of the periphery of the battery cell. In this case, both of the sealant layer122and the conductor layer124have a trapezoid shaped cross section.

InFIG. 6C, the conductor layer124is omitted. The outer conductive frame105and the negative current collecting substrate104are welded together.

InFIG. 6D, the conductor layer124is omitted. Only the seal layer122is used to seal the periphery of the electric core110. The peripheral ends of the current collecting substrates may be pressed together or pressed toward each other to form a tapered cross-sectional profile of the periphery of the battery cell. In this case, the sealant layer122has a trapezoid shaped cross section.

The positive current collecting substrate102may be any one well known in the art such as an aluminum foil. The positive electrode active material layer111may comprise a positive electrode active substance and an adhesive, in which the positive electrode active substance may be any one known in the art for the lithium ion battery. According to some embodiments of the present disclosure, the positive electrode active substance may comprise LiCoO2, LiFePO4, LiMn2O4, or any suitable three-component substances known in the art. The adhesive may be any one well known in the art such as polyvinylidene fluoride (PVDF). According to some embodiments of the present disclosure, the positive electrode active material layer may also comprise positive electrode additives. The positive electrode additive may be any one well known in the art and may be selected from conductive agents, for example, at least one of acetylene black, conductive carbon black and conductive graphite.

The negative current collecting substrate104may be any one well known in the art such as copper foil. The negative electrode active material layer113may comprise a negative electrode active substance and an adhesive. The negative electrode active substance may be any one commonly used in lithium ion batteries, such as natural graphite and artificial graphite. The adhesive may be any one well known in the art such as polyvinylidene fluoride (PVDF) and polyvinyl alcohol.

The electrolyte may comprise a lithium salt electrolyte and solvent. In some cases, gel-type or solid state electrolytes may be used. The lithium salt electrolyte may be at least one selected from lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium halide, lithium aluminum tetrachloride and lithium fluoro-alkyl sulfonate. The solvent may comprise an organic solvent, such as a mixture of chain-like acid esters or cyclic acid esters. The chain-like acid ester may comprise at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), dipropyl carbonate (DPC) and other fluorine-containing, sulfur-containing or unsaturated bond-containing chain-like organic esters. Alternatively, a solid state electrolyte such as lithium phosphorus oxynitride (also known as LiPON) may be used.

The separator112is electrically insulated and also has good electrolyte retaining performance. According to some embodiments of the present disclosure, the separator may be any kind of separators used in lithium-ion batteries known in the art, such as polyolefin micro-porous membrane, polyethylene felt, glass fiber felt or ultrafine glass fiber paper. Alternatively, an adhesive resin layer (not shown) may be provided to bond the positive electrode active material layer111or negative electrode active material layer113to the separator112. The adhesive resin layer may have a large number of through holes that communicate the positive electrode active material layer111or negative electrode active material layer113with the separator112. The adhesive resin layer may create an intimate interfacial contact between adjacent layers.

FIG. 7is a schematic, cross-sectional diagram illustrating a stack structure of a thin-film lithium-ion battery according to another embodiment of the invention. The stack structure of a thin-film lithium-ion battery may be composed of several secondary cells as described above in parallel to increase the discharge current capability, and may be available in series packs to increase the total available voltage.

As shown inFIG. 7, the stacked thin-film lithium-ion battery200may comprise at least two lithium-ion battery units100aand100b, each of which has a structure that is similar toFIG. 4. For example, the upper lithium-ion battery unit100acomprises a laminated electric core110acomprising a positive electrode active material layer111acoated on a first surface of an intermediate current collecting substrate203, a separator112asandwiched between the positive electrode active material layer111a, and a negative electrode active material layer113a. On the second surface of the intermediate current collecting substrate203is the laminated electric core110bof the lower lithium-ion battery unit100b. The laminated electric core110bcomprises a positive electrode active material layer111bcoated on the second surface of an intermediate current collecting substrate203, a separator112bsandwiched between the positive electrode active material layer111b, and a negative electrode active material layer113b. The laminated electric core110aand the laminated electric core110bare sandwiched between an upper current collecting substrate202and a lower current collecting substrate204. Likewise, sealant layers122a,122band outer packaging layers124a,124bmay be employed to provide high moisture-proof capability and insulating property.

The layers in the stack structure as described inFIG. 7may have different dimensions according to another embodiment of the invention. As shown inFIG. 13AandFIG. 13B, the topmost layer110ahas a dimension that is smaller than the underlying layer110b, which is smaller than the layer110c, which is smaller than the layer110d. The layer stack forms a non-rectangular or an irregular shape, terraced structure and may have a rounder corner. By providing such non-rectangular configuration of the battery, the free space within a portable electronic device can be efficiently utilized.

FIG. 14Ashows a two-cell battery according to yet another embodiment. As shown inFIG. 14A, the two cells including two laminated electric cores110aand110bmay be arranged in parallel to each other on the negative current collecting substrate104and then folded to sandwich about the positive current collecting substrate102. The battery is then sealed by using sealant layers122. The two cells inFIG. 14Aare electrically coupled in parallel.FIG. 14Bshows a four-cell battery according to yet another embodiment. As shown inFIG. 14B, the negative current collecting substrate104and the four cells including four laminated electric cores110are folded in a zigzag manner. The four cells inFIG. 14Bare electrically coupled in parallel.

FIG. 15illustrates the manufacturing steps for a three-cell battery pack. As shown inFIG. 15, an array of positive electrode active material layers111are formed on a panel A. An array of negative electrode active material layers113are formed on a panel B. On the panel A, respective electrical connection points C0, C2and C4are provided, which correspond to the electrical connection points C1, C3and C5on the panel B. The panel A is laminated onto the panel B to form a three-cell in series configuration.