Multilayer electrode for battery

Abstract

The present disclosure provides a multilayer electrode for a battery. The present disclosure relates to a secondary solid state battery. The battery comprises a current collector, and the current collector comprises a poly (3, 4-ethylenedioxythiophene) polystyrene sulfonic acid (PEDOT-PSS) layer which is in direct surface contact with the negative electrode. The battery also comprises a positive electrode; and a solid electrolyte separator positioned between the positive electrode and the negative electrode. The PEDOT-PSS layer may be compressed and expanded in response to expansion and contraction of the negative electrode. In some embodiments, the current collector may include a carrier film onto which the PEDOT-PSS layer is coated. The cell stack of the plurality of assemblies also includes a positive electrode, a solid electrolyte separator, a negative electrode, and a current collector, some adjacent pairs of which are separated by carbon fiber paper.

Description

Technical Field

[0001] The present disclosure relates to solid-state batteries (SSBs), and in particular, to mitigating problems associated with volume changes during battery charging and discharging in SSBs, especially those employing metal anodes such as lithium (Li) or silicon (Si). Background Art

[0002] SSBs can provide increased specific energy density and volumetric energy density. Utilizing metal anodes (such as Li or Si) in SSBs helps achieve these energy density metrics. These anodes are sometimes challenged by the significant volume changes they undergo during charge and discharge cycles.

[0003] In order to maintain interfacial contacts within the cell and compensate for these volume changes, stack pressures in the range of 5–50 MPa are typically required. Nevertheless, performance degradation of Li- or Si-based SSBs is still possible. This problem is partly attributed to stress fluctuations and associated strain accumulation in the electrodes during operation. Summary of the invention

[0004] This disclosure outlines a secondary SSB design that integrates a current collector, a poly (3,4-ethylenedioxythiophene polystyrene sulfonic acid) layer (PEDOT-PSS), with a negative electrode. The negative electrode is coated onto the PEDOT-PSS layer, which is structured to expand and contract in response to corresponding expansion and contraction of the negative electrode, thereby managing the strains involved in the operation of the battery.

[0005] In the proposed battery configuration, the positive and negative electrodes are separated by a solid electrolyte separator. The current collector can be further strengthened by adding a support film on which the PEDOT-PSS layer is coated, thereby increasing the mechanical integrity of the current collector.

[0006] The support film may be a polyimide substrate, providing insulation and structural benefits to the overall battery design.The combination of the positive electrode, solid electrolyte separator, negative electrode and current collector forms the electrode assembly.

[0007] The present disclosure further introduces a secondary SSB composed of several such electrode assemblies. Each assembly includes a positive electrode and a negative electrode; a solid electrolyte separator; and a current collector in direct surface contact with the negative electrode, thereby positioning the negative electrode between the solid electrolyte separator and the current collector.

[0008] In addition to these elements, the described battery configuration can incorporate carbon fiber papers interlaced with the electrode assemblies. These carbon fiber papers act as additional separators and stabilizers so that not all adjacent pairs of electrode assemblies are in direct contact. Some adjacent pairs of electrode assemblies are separated by one of these carbon fiber papers.

[0009] In another secondary SSB embodiment, the battery includes a positive electrode and a negative electrode; a solid electrolyte separator; and a current collector formed of a PEDOT-PSS layer coated on a carrier film. The carrier film is in direct surface contact with the negative electrode, wherein the negative electrode is located between the solid electrolyte separator and the current collector. In this design, the carrier film can be a polyimide substrate, thereby adding a layer of structural integrity to the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A is a schematic cross-section of a current collector comprising carbon fiber paper;

[0011] Figure 1B is a schematic cross section of an anode coating on a current collector;

[0012] Figure 2A is a schematic cross section of a single cell arrangement with a carbon fiber paper current collector;

[0013] Figure 2B is a schematic cross section of a battery cell stack arrangement with a carbon fiber paper current collector;

[0014] Figure 3 is a schematic cross section of carbon fiber paper as a strain buffer in a secondary SSB battery cell stack;

[0015] Figure 4 is a schematic cross section of an elastic material sandwiched between two metal foils;

[0016] Figure 5 is a schematic cross-section of a microporous layer-coated metal foam; and

[0017] Figure 6 is a schematic cross-section of a conductive polymer current collector in a secondary SSB cell. DETAILED DESCRIPTION

[0018] Embodiments are described herein. However, it should be understood that the disclosed embodiments are merely examples and that other embodiments may take various and alternative forms. The drawings are not necessarily drawn to scale. Some features may be enlarged or minimized to show details of particular components. Therefore, the specific structural details and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art.

[0019] Various features illustrated and described with reference to any one of the accompanying drawings may be combined with features illustrated in one or more other drawings to produce embodiments that are not explicitly illustrated or described. The combinations of illustrated features provide representative embodiments for typical applications. However, for specific applications or implementations, various combinations and modifications of features consistent with the teachings of the present disclosure may be desired.

[0020] Measures that can mitigate stress fluctuations, relieve strain accumulation, and reduce the need for stack pressure may be desirable. Such measures can enhance cycle stability and battery life, representing a significant advance in battery technology. The disclosed embodiments can mitigate challenges associated with volume changes of SSBs. The disclosed embodiments introduce elastic conductive layers that can be used as current collectors or separate strain buffers. The layers can be used for SSBs that exhibit significant volume changes during charge and discharge, such as those based on metal anodes such as Li metal and Si.

[0021] The conductivity of the layer should exceed 1 S / cm, ideally exceeding 10 S / cm. To accommodate SSB anode volume changes, the elasticity of the layer should be able to compensate for strains, for example, 40% strain under a compressive stress of 1.5 MPa. Ideally, the layer should have a compressive elastic modulus ranging between 1 MPa and 10 MPa, and a strain range of up to 60%. The thickness of the layer should be small, ideally less than 80 microns in the uncompressed state.

[0022] In one embodiment, carbon fiber paper can be used as a current collector. A microporous layer composed of nano-sized carbon particles is coated on the carbon fiber paper to ensure a smooth surface for coating an electrode (eg, Si anode layer).

[0023] In another embodiment, metal foam can be used as the main elastic component, with a microporous (carbon) layer coated on top of it to tune the surface roughness and enhance electrical contact. The elastic properties of the metal foam can be designed as desired. The microporous layer composed of nano-sized carbon particles is used to ensure a smooth surface for coating the Si anode layer.

[0024] In another embodiment, a sandwich configuration of an elastic material between two metal layers is envisioned. In this design, an elastic material (such as silicone rubber) is sandwiched between two metal foils. The metal foil provides electrical connection, and the spring-like intermediate layer contracts when the electrode expands, thereby releasing the strain of the electrode active material. When the active material contracts, the layer rebounds to keep the particles in close contact. The properties of the elastic material (such as elastic modulus and thickness) can be customized to meet the expansion and contraction requirements. The thickness of the metal foil can be in the range of 2 to 5 μm to minimize the total thickness of the collector. The metal foil can be the same metal (such as Cu foil or Al foil) or different metals (one side can be Cu foil and the other side is Al foil).

[0025] These elastic and conductive layers can be used not only as direct replacements for metal foil current collectors (i.e., copper foil on the anode and aluminum foil on the cathode) in the present battery manufacturing, but also as strain buffers between individual cells. The latter may be more cost effective in the case of SSB electrodes that show smaller volume changes during charge and discharge. The number of such strain buffer layers and their location need to be carefully considered to have optimal performance and minimal cost increase.

[0026] The present disclosure relates to cycling stability, thereby increasing the useful life of metal anode based SSBs. Another potential benefit of the present disclosure is to reduce operating stack pressures, which is currently challenging for battery packaging in electric vehicles. The present disclosure has the potential to reduce stack pressures to less than 1 MPa, thereby simplifying battery packaging.

[0027] Furthermore, the envisioned embodiments do not increase battery manufacturing complexity. For example, the new current collector is a direct replacement for current metal foils in a roll-to-roll process. Strain buffer layers can be easily inserted between individual cells.

[0028] Figure 1A An exemplary embodiment of a carbon fiber paper is provided. Such a carbon fiber paper, designated as reference numeral 10, is a composite structure comprising a core carbon fiber layer 12 encapsulated between two microporous layers designated as reference numerals 14 and 16, respectively. The microporous layers 14 and 16 include a plurality of nano-sized carbon particles 18 effectively embedded within the microporous layers. The typical thickness of the microporous layers is in the range of 1-10 um.

[0029] The presence of these microporous layers 14, 16 on both sides of the carbon fiber layer 12 not only helps to enhance the mechanical stability of the carbon fiber paper 10, but also serves to make its surface smoother. This enhanced surface smoothness is advantageous when the Si anode layer is subsequently coated, thereby assisting the adhesion and uniform coverage of the layers.

[0030] In one embodiment, the carbon fiber paper 10 acts as a current collector within the construction of the SSB. In this function, the carbon fiber paper is configured so that one of the microporous layers (say, 14) is in direct surface contact with the negative electrode, while the other microporous layer (say, 16) is in direct area contact with the negative electrode or the positive electrode. The result of this arrangement ensures that the surface of the current collector is smoother than the surface of the constituent carbon fibers.

[0031] Convert to Figure 1B , depicts the process of coating Si anode slurry (indicated as numeral 20) onto carbon fiber paper 10. Once applied, the Si anode slurry 20 assumes the role of a negative electrode.

[0032] It is noted that nano-sized carbon particles 18 are incorporated into the microporous layers 14, 16 for enhanced conductivity and to facilitate efficient electron transfer within the battery. In certain embodiments, the carbon fiber layer 12 may be in the form of a metal foam such as Cu or Al. The size of the metal foam layer may be such that the thickness of the metal foam layer exceeds the thickness of each of the microporous carbon layers 14, 16.

[0033] After the coating process, a solid electrolyte separator is applied such that it is in direct contact with the Si anode 20. Furthermore, in some configurations, a positive electrode may be introduced into the cell structure, arranged such that it is in direct facing contact with the solid electrolyte separator on the other side.

[0034] This outlined configuration forms an integrated battery cell assembly comprising: a positive electrode coated on a current collector, which may be a carbon fiber paper 10; a solid electrolyte separator; and a negative electrode, which may be applied as a Si slurry on the current collector. Multiple such cell assemblies and carbon fiber papers may be assembled in a staggered manner. Adjacent pairs of electrode assemblies may be separated by one of the carbon fiber papers.

[0035] Continue to Figure 2A , the battery cell structure in the embodiment mentioned is illustrated. The battery cell includes carbon fiber paper 10 as a base layer. On top of the base layer, a Si anode layer 22 is deposited, which represents the negative electrode in the battery cell structure. The Si anode layer 22 directly interfaces with the microporous layer 14 of the carbon fiber paper 10, thereby benefiting from the smoother surface provided by the microporous layer.

[0036] After the Si anode layer 22, a solid electrolyte separator 24 is applied, which directly interfaces with the Si anode layer 22. The solid electrolyte separator 24 facilitates ion transport between the battery electrodes while preventing direct electronic contact between the battery electrodes.

[0037] On top of the solid electrolyte separator 24, a cathode layer 26 is applied to form the positive electrode of the battery cell structure. The complete structure is then completed with a current collector to form a single battery cell. Currently commonly used aluminum foil can be used as a cathode current collector. Carbon fiber paper current collector 10 can also be used for the cathode. The configuration represents a coherent cell assembly that integrates the positive electrode (cathode layer 26), the solid electrolyte separator 24 and the negative electrode (Si anode layer 22).

[0038] Convert to Figure 2B , which presents an embodiment of a bipolar arrangement of a battery cell. Figure 2AIn the embodiment of the present invention, a complete battery cell structure is formed in the stack, and another complete battery cell structure is stacked on top of the existing structure. Each cell in the stack maintains the same layer sequence as a single cell, i.e., starting with a carbon fiber paper current collector 10 at the base, followed by a Si anode layer 22, a solid electrolyte separator 24, and a cathode layer 26, and then repeating the structure. Finally, the battery cell can be completed with the carbon fiber paper 10.

[0039] This bipolar stack design allows for enhanced energy density by allowing the series connection of multiple cells. The bipolar configuration allows both the anode and cathode to share current collectors, thereby reducing the overall weight and volume of the battery, resulting in a more compact and efficient design. Therefore, this design accommodates multiple electrode assemblies and carbon fiber papers in a staggered manner, where only some adjacent electrode assembly pairs are separated by one of the carbon fiber papers. This compact layer arrangement in the bipolar configuration optimizes the performance and efficiency of the battery.

[0040] The elastic and conductive carbon fiber structure can be used not only as a current collector but also as a strain buffer layer. Figure 3 , illustrating an extended battery stack. The configuration starts with a carbon fiber paper (denoted by the number 30), which is used as a base layer. The layer is followed by two or more individual battery cells, denoted by the number 32. Each of these individual cells 32 includes several components: a Si anode 34, a solid electrolyte separator 36, a cathode 38, and a substrate layer. The cathode substrate can be an aluminum (Al) foil 40, and the substrate of the anode can be a copper foil 42. Another layer of carbon fiber paper 30 is placed on these components, followed by subsequent individual cells 32.

[0041] In this particular arrangement, a Si anode 34 is coated on a Cu foil 42 in accordance with conventional battery manufacturing techniques. However, this structure differs in that the carbon fiber paper 30 is integrated as a strain buffer layer. The role of this layer is to help dissipate mechanical stresses, thereby contributing to the overall durability and life of the battery cell.

[0042] Note that it is not necessary to include carbon fiber paper 30 for every single cell 32. Depending on the experimental determination and desired properties of the battery, this layer may be included after every 3 to 5 single cells, for example. The exact placement will be determined based on experimental results. By reducing the number of carbon fiber papers 30 in the stack, the configuration becomes more compact, thus enhancing the volumetric energy density of the battery.

[0043] The complete structure represents a secondary SSB. The secondary SSB incorporates several electrode assemblies, each of which includes: a positive electrode and a negative electrode; a solid electrolyte separator 36, which is located between the positive electrode and the negative electrode; and a current collector, which is in direct surface contact with the negative electrode. In this design, the negative electrode (Si anode 34) is retained between the solid electrolyte separator 36 and the current collector (carbon fiber paper 30).

[0044] The secondary SSB configuration also employs carbon fiber papers 30 interlaced with the electrode assemblies. In this arrangement, some but not all adjacent pairs of electrode assemblies are separated by one of the carbon fiber papers 30.

[0045] In additional aspects of the depicted embodiments, the current collector may incorporate a carrier film to support structural integrity and better bonding with the negative electrode. A viable choice for the carrier film may be a polyimide substrate due to its mechanical and thermal stability. The polyimide substrate may be coated with a layer of poly-3,4-ethylenedioxythiophene polystyrene sulfonic acid (i.e., a conductive polymer) to enhance the current collection capability of the current collector.

[0046] Now transfer to Figure 4 , which presents a configuration of an elastic material 40 encapsulated between two metal foils 42 and 44. Specifically, in this configuration, an elastic material (such as silicone rubber) is used as a central layer, thereby creating an elastic structure that can adapt to the expansion and contraction behavior of the battery components.

[0047] The role of the metal foils 42 and 44 is multifaceted. Primarily, the metal foils act as conduits to provide electrical connections. Additionally, the metal foils act in conjunction with the elastic material 40 to form a compressible structure. This "spring-like" interlayer is designed to contract when the electrode expands during a charge cycle, thereby relieving the strain experienced by the electrode active material. Conversely, this "spring-like" interlayer springs back or expands when the active material retracts during a discharge cycle, thereby ensuring that the particles remain in close contact.

[0048] These adaptive behaviors help maintain the integrity of the battery, thereby enhancing its durability and performance.It should be noted that the properties of the elastic material 40, such as its elastic modulus and thickness, can be precisely designed to meet the specific expansion and contraction requirements of the battery.

[0049] To maintain a compact design of the battery and minimize the overall thickness of the current collector, the thickness of the metal foils 42 and 44 can be kept in the 2-5 um range. This careful balance ensures that the battery maintains its energy density while incorporating the strain relief benefits of the elastic layer 40.

[0050] Depending on design needs and performance requirements, metal foils 42 and 44 can be made of the same material or different materials. In some configurations, both can be Cu, Al, or any other conductive material suitable for application requirements. In other cases, the metal foils can be composed of different materials to optimize certain properties, such as conductivity, mechanical strength, or corrosion resistance.

[0051] The secondary SSB configuration incorporates this current collector design in which the elastomeric material is sandwiched between two metal foils. In this configuration, the negative electrode and the positive electrode are separated by a solid electrolyte separator, and each of the metal foils of the current collector is in direct face contact with the positive electrode or the negative electrode.

[0052] The entire configuration consisting of positive and negative electrodes, solid electrolyte separators, and uniquely designed current collectors forms an electrode assembly. The battery may also include multiple of these electrode assemblies and carbon fiber papers interlaced with the electrode assemblies. This arrangement ensures that some but not all adjacent pairs of electrode assemblies are separated by one of the carbon fiber papers, thereby enhancing the mechanical stability and performance of the battery.

[0053] Now turn to Figure 5 , presenting a novel design configuration. Here, a metal foam 50 is used as the main elastic component encapsulated by two microporous layers 52 and 54. These microporous layers are composed of nano-sized carbon particles and provide multiple functions to the overall system.

[0054] The microporous layers 52 and 54 serve as important interfaces, contributing to both the mechanical and electrical properties of the assembly. The microporous layers are used to tune the surface roughness of the metal foam 50, resulting in a more uniform and conductive surface. This smooth surface becomes ideal for subsequent coating of the Si anode layer, helping to enhance its adhesion and uniformity. The microporous layers 52 and 54 also play a key role in enhancing electrical contact, contributing to electrical conductivity within the assembly.

[0055] The metal foam 50 was chosen at the core of this design because of its inherent elasticity. This elasticity allows the metal foam to respond to the expansion and contraction of the electrode during the charge-discharge cycle of the battery, thereby enhancing durability and reliability. The elastic properties of the metal foam 50 can be carefully designed to meet desired specifications, thereby ensuring optimal performance in response to the mechanical behavior of the active material.

[0056] The described configuration is integrated in a secondary SSB, where the current collector comprises the described metal foam 50 sandwiched between microporous layers 52 and 54. The positive and negative electrodes are separated by a solid electrolyte separator, and each of the microporous layers of the current collector is in direct facing contact with the positive or negative electrode.

[0057] The entirety of this assembly - including the positive and negative electrodes, the solid electrolyte separator and the uniquely designed current collector - forms a cell assembly. The battery design may include multiple such cell assemblies. In addition, the carbon fiber paper may be interlaced with these assemblies so that not all pairs of adjacent electrode assemblies are in direct contact. Instead, some electrode assemblies are separated by the carbon fiber paper, thereby providing additional mechanical stability and enhancing the overall performance of the battery.

[0058] Reference now Figure 6, introducing a secondary SSB cell configuration 60. In this embodiment, a strain buffer layer and current collector integrated poly 3,4-ethylenedioxythiophene polystyrene sulfonic acid (PEDOT-PSS) layer 62 forms the basic component. An anode layer 64, which can be a Si anode, can be directly coated on the PEDOT-PSS layer.

[0059] The PEDOT-PSS layer 62 itself is coated on a carrier film 66 , such as an insulating polyimide substrate, which is used to provide structural support to the PEDOT-PSS layer 62 , thereby enhancing the overall mechanical stability of the SSB cell 60 .

[0060] However, the carrier film 66 may be retained or removed in a SSB stack, depending on the specific cell configuration. For example, the carrier film may be removed in a bipolar stack configuration to optimize space and material efficiency.

[0061] To further increase the mechanical strength of the conductive polymer current collector (PEDOT-PSS) 62, the layer can be reinforced with other porous substrates or polymer materials. These may include expanded polytetrafluoroethylene (e-PTFE), fiberglass, cellulose substrates, or polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and other options. These reinforcements ensure that the current collector is robust and able to withstand the mechanical stresses experienced during battery operation.

[0062] The SSB cell 60 as a whole is composed of a positive electrode 68, a solid electrolyte separator 70, a negative electrode 64, and a current collector 62. The current collector 62 including a PEDOT-PSS layer is in direct surface contact with the negative electrode 64. The negative electrode 64 is in turn positioned between the solid electrolyte separator 70 and the current collector 62.

[0063] The arrangement including the positive electrode 68, the solid electrolyte separator 70, the negative electrode 64 and the current collector 62 forms a cell assembly. These assemblies can be used to produce secondary SSBs including multiple such assemblies. In addition, the carbon fiber paper can be interlaced with these assemblies so that not all adjacent pairs of electrode assemblies are in direct contact. Instead, some electrode assemblies are separated by carbon fiber paper, thereby providing additional mechanical stability and enhancing the overall performance of the battery.

[0064] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms covered by the claims. The words used in the specification are words of description rather than limitation, and it should be understood that various changes can be made without departing from the spirit and scope of these disclosed materials.

[0065] As previously described, features of the various embodiments may be combined to form additional embodiments of the present disclosure that may not be explicitly described or illustrated. Although various embodiments may have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, it will be appreciated by those of ordinary skill in the art that one or more features or characteristics may be compromised to achieve desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, and the like. Therefore, embodiments that are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are within the scope of the present disclosure and may be desirable for a particular application.

Claims

1. A secondary solid-state battery, comprising: a current collector comprising a poly (3,4-ethylenedioxythiophene) polystyrene sulfonic acid layer; a negative electrode coated on the poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid) layer such that the poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid) layer is configured to compress and expand, respectively, in response to expansion and contraction of the negative electrode; Positive electrode; as well as A solid electrolyte separator is located between the positive electrode and the negative electrode. 2 . The secondary solid-state battery of claim 1 , wherein the current collector further comprises a carrier film. 3 . The secondary solid-state battery according to claim 2 , wherein the carrier film is a polyimide substrate. 4 . The secondary solid-state battery according to claim 2 , wherein the poly (3,4-ethylenedioxythiophene) polystyrene sulfonic acid) layer is coated on the carrier film.

5. The secondary solid-state battery of claim 1, wherein the positive electrode, the solid electrolyte separator, the negative electrode and the current collector form an electrode assembly, and the secondary solid-state battery further comprises a plurality of the electrode assemblies and carbon fiber paper interlaced with the electrode assembly.

6. The secondary solid-state battery of claim 5, wherein the carbon fiber papers are interlaced with the electrode assemblies such that some but not all adjacent pairs of the electrode assemblies are separated by one of the carbon fiber papers.

7. A secondary solid-state battery, comprising: a plurality of electrode assemblies, each of the electrode assemblies comprising a positive electrode and a negative electrode, a solid electrolyte separator positioned between the positive electrode and the negative electrode, and a current collector in direct surface contact with the negative electrode such that the negative electrode is positioned between the solid electrolyte separator and the current collector; and Carbon fiber papers are interlaced with the electrode assemblies such that some but not all adjacent pairs of the electrode assemblies are separated by one of the carbon fiber papers. 8 . The secondary solid-state battery of claim 7 , wherein the current collector comprises a poly (3,4-ethylenedioxythiophene) polystyrene sulfonic acid) layer.

9. The secondary solid-state battery of claim 8, wherein the current collector further comprises a carrier film.

10. The secondary solid-state battery according to claim 9, wherein the carrier film is a polyimide substrate. 11 . The secondary solid-state battery according to claim 10 , wherein the poly (3,4-ethylenedioxythiophene) polystyrene sulfonic acid) layer is coated on the carrier film.

12. A secondary solid-state battery, comprising: Positive and negative electrodes; a solid electrolyte separator, the solid electrolyte separator being located between the positive electrode and the negative electrode; as well as A support film and a poly (3,4-ethylenedioxythiophene) polystyrene layer coated on the support film to form a current collector in direct surface contact with the negative electrode, so that the negative electrode is located between the solid electrolyte separator and the current collector.

13. The secondary solid-state battery of claim 12, wherein the carrier film is a polyimide substrate.

14. The secondary solid-state battery of claim 12, wherein the positive electrode, the solid electrolyte separator, the negative electrode and the current collector form an electrode assembly, and the secondary solid-state battery further comprises a plurality of the electrode assemblies and carbon fiber paper interlaced with the electrode assembly.

15. The secondary solid-state battery of claim 14, wherein the carbon fiber papers are interlaced with the electrode assemblies such that some but not all adjacent pairs of the electrode assemblies are separated by one of the carbon fiber papers.

Images