Current collector assembly and secondary battery

Abstract

The present invention improves high-rate charge / discharge characteristics. This current collector assembly includes: an insulating substrate having a first main surface and a second main surface on the side opposite the first main surface; a positive-electrode current collector provided on the first main surface; and a negative-electrode current collector provided on the second main surface. The insulating substrate, the positive-electrode current collector, and the negative-electrode current collector are porous bodies.

Description

Current collector assembly and secondary battery

[0001] The present invention relates to a current collector assembly and a secondary battery.

[0002] Non-Patent Documents 1 and 2 state that if the electrodes of a secondary battery are made thicker, the proportion of active material in the battery increases, and the battery capacity and energy density can be improved.

[0003] Yudi Kuang, Chaoji Chen, Dylan Kirsch, Liangbing Hu, Thick Electrode Batteries: Principles, Opportunities, and Challenges, Advanced Energy Materials 9, 1901457 (2019).Christian Heubner, Michael Schneider, Alexander Michaelis, Diffusion-Limited C-Rate: A Fundamental Principle Quantifying the Intrinsic Limits of Li-Ion Batteries, Advanced Energy Materials 10, 1902523 (2020).

[0004] Non-Patent Documents 1 and 2 state that thickening the electrodes of a secondary battery increases the diffusion distance of carrier ions, making it difficult to pass a large current, which may result in a decrease in capacity at high rates with large currents.

[0005] In view of the above problems, an object of the present invention is to provide a current collector assembly and a secondary battery that improve the charge / discharge characteristics at high rates.

[0006] A current collector assembly according to one aspect of the present invention includes an insulating film having a first main surface and a second main surface opposite the first main surface, a positive electrode current collector provided on the first main surface, and a negative electrode current collector provided on the second main surface, wherein the insulating film, the positive electrode current collector, and the negative electrode current collector are porous.

[0007] A secondary battery according to one aspect of the present invention includes an insulating film having a first main surface and a second main surface opposite the first main surface, a positive electrode provided on the first main surface, and a negative electrode provided on the second main surface, wherein the positive electrode has a positive electrode current collector and a positive electrode active material layer, the negative electrode has a negative electrode current collector and a negative electrode active material layer, the insulating film is a porous body, and the positive electrode current collector and the negative electrode current collector are porous bodies or porous plates.

[0008] According to the present invention, it is possible to provide a current collector assembly and a secondary battery that improve the charge / discharge characteristics at high rates.

[0009] FIG. 1 is a cross-sectional view showing an example of a secondary battery according to the first embodiment. FIG. 2 is an enlarged cross-sectional view showing a portion of the cross section of the electrode body according to FIG. 1. FIG. 3 is an enlarged cross-sectional view showing the current collector assembly according to FIG. 2. FIG. 4 is a diagram showing a manufacturing process of the current collector assembly according to the first embodiment. FIG. 5 is an enlarged cross-sectional view showing a portion of the cross section of the electrode body of a secondary battery according to Comparative Example 1. FIG. 6 is a diagram showing changes in areal capacity of secondary batteries according to Comparative Example 1 and Example 1. FIG. 7 is a diagram showing capacity versus rate of secondary batteries according to Comparative Example 1 and Example 1. FIG. 8A is a diagram showing charge / discharge curves of the secondary battery according to Comparative Example 1. FIG. 8B is a diagram showing charge / discharge curves of the secondary battery according to Example 1. FIG. 9 is a cross-sectional view showing an example of an electrode body of a secondary battery according to the second embodiment. FIG. 10 is a diagram showing an enlarged view of a positive electrode current collector according to the second embodiment. FIG. 11 is a cross-sectional view showing an example of an electrode body of a secondary battery according to a fourth modified example. FIG. 12 is a cross-sectional view showing an example of an electrode body of a secondary battery according to a fifth modified example. FIG. 13 is a diagram showing a positive electrode current collector according to Example 4. FIG. 14 is a diagram showing a negative electrode current collector according to Example 4. FIG. 15 is a diagram showing the results of a first charge / discharge test according to Example 2. FIG. 16 is a diagram showing the results of a second charge / discharge test according to Examples 2 and 3. FIG. 17 is a diagram showing the results of a third charge / discharge test according to Example 4. FIG. 18A is a diagram showing the design principle of a porous current collector in a battery. FIG. 18B is a diagram showing the design principle of a porous current collector in a battery. FIG. 18C is a diagram showing the design principle of a porous current collector in a battery. FIG. 19A is a diagram showing the results of a numerical simulation of a battery having a TCC and a PCC, respectively. FIG. 19B is a diagram showing the results of a numerical simulation of a battery having a TCC and a PCC, respectively. FIG. 19C is a diagram showing the results of a numerical simulation of a battery having a TCC and a PCC, respectively. FIG. 19D is a diagram showing the results of a numerical simulation of a battery having a TCC and a PCC, respectively. FIG. 19E is a diagram showing the results of a numerical simulation of a battery having a TCC and a PCC, respectively. FIG. 19F is a diagram showing the results of a numerical simulation of a battery having a TCC and a PCC, respectively. FIG. 19G shows the numerical simulation results of the cells with TCC and PCC, respectively.FIG. 19H shows the results of numerical simulations of batteries with TCC and PCC, respectively. FIG. 20A shows the main design concepts and characteristics of PCC and FIG. 20B shows the main design concepts and characteristics of PCC and FIG. 20C shows the main design concepts and characteristics of PCC and FIG. 20D shows the main design concepts and characteristics of PCC and FIG. 20E shows the main design concepts and characteristics of PCC and FIG. 20F shows the main design concepts and characteristics of PCC and FIG. 20G shows the main design concepts and characteristics of PCC and FIG. 20H shows the main design concepts and characteristics of PCC and FIG. 20I shows the main design concepts and characteristics of PCC and FIG. 20J shows the main design concepts and characteristics of PCC and FIG. 21A shows the electrochemical performance of a multi-layer pouch battery with TCC and PCC and FIG. 21B shows the electrochemical performance of a multi-layer pouch battery with TCC and PCC and FIG. 21C shows the electrochemical performance of a multi-layer pouch battery with TCC and PCC. Figure 21D shows the electrochemical performance of a multi-layer pouch battery with TCC and PCC. Figure 21E shows the electrochemical performance of a multi-layer pouch battery with TCC and PCC. Figure 21F shows the electrochemical performance of a multi-layer pouch battery with TCC and PCC. Figure 21G shows the electrochemical performance of a multi-layer pouch battery with TCC and PCC. Figure 22A shows the electrochemical performance of a multi-layer pouch battery with TCC and PCC. ０ FIG. 22B shows differential pressure sensing revealing the deposition of Li during fast charging. ０ FIG. 22C shows differential pressure sensing revealing the deposition of Li during fast charging. ０ FIG. 22D shows differential pressure sensing revealing the deposition of Li during fast charging. ０ FIG. 22E shows differential pressure sensing revealing the deposition of Li during fast charging. ０ FIG. 22F shows differential pressure sensing revealing the deposition of Li during fast charging. ０ FIG. 22G shows differential pressure sensing revealing the deposition of Li during fast charging.０ Figure 23A shows differential pressure sensing revealing the deposition of NMC at a high NMC capacitance areal density of 3 mAh / cm. ２ Figure 23B shows the lithium concentration distribution of NMC|graphite multilayer pouch cells with TCC at high NMC capacity areal densities of 3 mAh / cm and N / P ratios of 1.1. ２ Figure 24A shows the lithium concentration distribution of NMC|graphite multilayer pouch cells with PCC at high NMC capacity areal density of 9 mAh / cm and N / P ratio of 1.1. ２ Figure 24B shows the lithium concentration distribution of NMC|graphite multilayer pouch cells with TCC at a high NMC capacity areal density of 9 mAh / cm and an N / P ratio of 1.1. ２Figure 25A shows the lithium concentration distribution of an NMC|graphite multilayer pouch battery with PCC at an N / P ratio of 1.1 and a charge rate of 4C (15 min charge). Figure 25B shows the spatial distribution of graphite anode potential with PCC at a charge rate of 4C (15 min charge). Figure 26A illustrates the electrochemical stability of a porous Kevlar® membrane in a battery. Figure 26B illustrates the electrochemical stability of a porous Kevlar® membrane in a battery. Figure 27A shows an SEM image of a Celgard 2500 separator before Cu metal coating. Figure 27B shows an SEM image of a Celgard 2500 separator after Cu metal coating. Figure 28A shows a cross-sectional SEM image of a PCC at low magnification. Figure 28B shows a cross-sectional SEM image of a PCC at high magnification. Figure 29A shows the lithium distribution of PCC cells with different porosities. Figure 29B shows the lithium distribution of PCC cells with different porosities. Figure 29C shows the lithium distribution of PCC cells with different porosities. Figure 29D shows the lithium distribution of PCC cells with different porosities. Figure 30 shows the mechanical performance of PCCs tested on an Instron 5565. Figure 31A illustrates the four-probe method for measuring the electronic conductivity of TCCs and PCCs. Figure 31B illustrates the four-probe method for measuring the electronic conductivity of TCCs. Figure 31C illustrates the four-probe method for measuring the electronic conductivity of PCCs. Figure 32A illustrates batteries with different tab configurations and their current collector resistances. Figure 32B illustrates batteries with different tab configurations and their current collector resistances. Figure 32C illustrates batteries with different tab configurations and their current collector resistances. Figure 33 illustrates the arrangement of blocking cells for ionic conductivity testing. Figure 34 shows the wettability of PCC with electrolytes compared to that of Celgard 2325, as measured by contact angle. Figure 35A shows an alternative fabrication of a trilayer polymer matrix as a potential host for PCC.Figure 35B illustrates an alternative fabrication of a trilayer polymer matrix as a potential PCC host. Figure 35C illustrates an alternative fabrication of a trilayer polymer matrix as a potential PCC host. Figure 35D illustrates an alternative fabrication of a trilayer polymer matrix as a potential PCC host. Figure 35E illustrates an alternative fabrication of a trilayer polymer matrix as a potential PCC host. Figure 36 illustrates the stability of thick electrodes using carbon black and isolated Tuball carbon nanotube networks as conductive additives. Figure 37A illustrates the fabrication of an electrode using Tuball carbon nanotubes. Figure 37B illustrates the fabrication of an electrode using Tuball carbon nanotubes. Figure 37C illustrates the fabrication of an electrode using Tuball carbon nanotubes. Figure 37D illustrates the fabrication of an electrode using Tuball carbon nanotubes. Figure 37E illustrates the fabrication of an electrode using Tuball carbon nanotubes. Figure 37F illustrates the fabrication of an electrode using Tuball carbon nanotubes. Figure 38 illustrates the calendaring and alignment of an electrode to a PCC. Figure 39A shows Li during fast charging of the TCC. ０ Figure 39B shows differential pressure sensing revealing deposition of Li during fast charging of the TCC. ０ Figure 39C shows differential pressure sensing revealing deposition of Li during fast charging of the TCC. ０Figure 40A shows the dP / |dQ| curves of a pouch battery with PCC at 4C. Figure 40B shows the dP / |dQ| curves of a pouch battery with PCC at 5C. Figure 40C shows the dP / |dQ| curves of a pouch battery with PCC at 10C. Figure 41A shows the electrochemical performance of a battery with PCC and TCC. Figure 41B shows the electrochemical performance of a battery with PCC and TCC. Figure 42A illustrates the TCC cell structure. Figure 42B illustrates the PCC cell structure with a separator. Figure 42C illustrates the PCC cell structure without a separator. Figure 42D illustrates the effect of a PCC cell structure without a separator on reducing PCC current density. Figure 43A illustrates the construction of a multi-layer pouch battery with TCC. Figure 43B illustrates the construction of a multi-layer pouch battery with PCC. Figure 44A illustrates the fabrication of a proof-of-concept PCC fabricated by UV laser cutting. Figure 44B illustrates a proof-of-concept PCC fabricated by UV laser cutting. Figure 44C illustrates a proof-of-concept PCC fabricated by UV laser cutting. Figure 44D illustrates a proof-of-concept PCC fabricated by UV laser cutting. Figure 44E illustrates a proof-of-concept PCC fabricated by UV laser cutting. Figure 44F illustrates the performance of a proof-of-concept PCC fabricated by UV laser cutting. Figure 44G illustrates the performance of a proof-of-concept PCC fabricated by UV laser cutting. Figure 45A illustrates a porous stainless-steel (SS) mesh. Figure 45B illustrates a porous stainless-steel (SS) mesh. Figure 45C illustrates a porous copper (Cu) mesh. Figure 45D illustrates a porous copper (Cu) mesh. Figure 45E shows a PCC design using porous stainless steel (SS) mesh and porous copper (Cu) mesh, and Figure 45F shows a PCC design verification using porous stainless steel (SS) mesh and porous copper (Cu) mesh.

[0010] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0011] (Secondary battery) Fig. 1 is a cross-sectional view showing an example of a secondary battery according to the first embodiment. The secondary battery 1 shown in Fig. 1 is a laminated lithium-ion secondary battery. As shown in Fig. 1, the secondary battery 1 includes a battery element 20, an exterior member 30, and an adhesive 32.

[0012] The battery element 20 is provided inside an exterior member 30. As shown in FIG. 1 , the battery element 20 includes an electrode body 200, a positive electrode lead 21, and a negative electrode lead 22. The positive electrode lead 21 is a terminal drawn from a positive electrode current collector 212 (described later) to the outside of the exterior member 30. That is, the positive electrode lead 21 is a terminal that serves as a positive electrode of the secondary battery 1. In FIG. 1 , the positive electrode lead 21 is provided on an end surface of the electrode body 200. The negative electrode lead 22 is a terminal drawn from the inside of a negative electrode current collector 213 (described later) to the outside of the exterior member 30. That is, the negative electrode lead 22 is a terminal that serves as a negative electrode of the secondary battery 1. In FIG. 1 , the negative electrode lead 22 is provided on an end surface of the electrode body 200. Details of the electrode body 200 will be described later.

[0013] The exterior member 30 is a case in which the battery element 20 is housed. The exterior member 30 includes two exterior sheets 30a and 30b. The exterior sheets 30a and 30b each include an insulating layer, a metal layer, and an outermost layer. In the example of FIG. 1 , the exterior sheet 30a has a recess 31. As a result, the battery element 20 is housed in the exterior member 30 by housing the battery element 20 in the recess 31 and bonding the peripheral edges of the exterior sheets 30a and 30b.

[0014] The exterior sheets 30a, 30b are constructed by laminating an insulating layer, a metal layer, and an outermost layer in this order from the inside, i.e., the side where the battery element 20 is provided, and then bonding them together by lamination or other processing. The insulating layers of the exterior sheets 30a, 30b are made of resins such as polyethylene, polypropylene, modified polyethylene, modified polypropylene, and polyolefin resins containing ethylene or propylene as monomers. This allows the exterior sheets 30a, 30b to reduce the moisture permeability of the secondary battery 1 and improve its airtightness. The metal layers of the exterior sheets 30a, 30b are metal plate or foil materials such as aluminum, stainless steel, nickel, and iron. The outermost layer may be made of any material, but is preferably made of the same resin as the insulating layer or a material with high resistance to tearing and punctures, such as nylon.

[0015] The adhesive 32 is a member for making the exterior member 30 airtight. The adhesive 32 is provided between the exterior member 30 and the positive electrode lead 21 and the negative electrode lead 22. The material of the adhesive 32 preferably has adhesion to the positive electrode lead 21 and the negative electrode lead 22. For example, when the positive electrode lead 21 and the negative electrode lead 22 are made of a metal material, the adhesive 32 is made of a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene. This allows the adhesive 32 to seal the gap between the exterior member 30 and the positive electrode lead 21 and the negative electrode lead 22, thereby making the interior of the exterior member 30 airtight.

[0016] FIG. 2 is an enlarged cross-sectional view showing a portion of the cross section of the electrode assembly shown in FIG. 1. More specifically, FIG. 2 is a cross-sectional view showing a portion of two pairs of positive and negative electrodes of the electrode assembly 200. As shown in FIG. 2, the electrode assembly 200 includes a current collector assembly 210, a positive electrode active material layer 220, a negative electrode active material layer 230, and a separator 240. In the secondary battery 1, the electrode assembly 200 has a structure in which the positive electrode active material layer 220, the current collector assembly 210, the negative electrode active material layer 230, the separator 240, the positive electrode active material layer 220, the current collector assembly 210, and the negative electrode active material layer 230 are stacked in this order. The positive electrode active material layer 220 and the negative electrode active material layer 230 included in the electrode assembly 200 are layered members for the charge / discharge reaction of the secondary battery according to the first embodiment. In the following description, one thickness direction of the electrode body 200 may be referred to as the Z1 direction, and the other thickness direction of the electrode body 200 may be referred to as the Z2 direction.

[0017] Fig. 3 is an enlarged cross-sectional view showing the current collector assembly shown in Fig. 2. As shown in Fig. 3, the current collector assembly 210 includes an insulating film 211, a positive electrode current collector 212, and a negative electrode current collector 213.

[0018] The insulating film 211 is an insulating film. In the present disclosure, insulating means a film having an electrical conductivity of 10 －６S / m or less. This prevents short circuits between the positive electrode current collector 212 and the negative electrode current collector 213. The insulating film 211 is porous. In the present disclosure, "porous" refers to a material with a porosity of 10% or more. This allows carrier ions of the secondary battery 1, such as lithium ions, to pass through the insulating film 211 in the thickness direction. The porosity of the insulating film 211 is preferably 40% or more. This increases the strength of the insulating film 211, allowing the secondary battery 1 to achieve both electrochemical stability and good mechanical properties. The average pore diameter of the insulating film 211 is preferably 10 nm or more and 50 μm or less, and is more preferably a nanoporous material. Here, a nanoporous material refers to a material with an average pore diameter in the mesopore range, i.e., 10 nm or more and 50 nm or less. This provides excellent lithium ion permeability. The insulating film 211 includes, for example, a polymer material. The insulating film 211 preferably contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide, with polyparaphenylene terephthalamide being particularly preferred. An example of the insulating film 211 containing glass is glass filter paper such as GC-50 from Advantec. Another example of the insulating film 211 containing metal oxide is a porous alumina film. This increases the strength of the insulating film 211, enabling the secondary battery 1 to achieve both electrochemical stability and excellent mechanical properties. In this disclosure, the average pore diameter refers to 4V / A, which is the value obtained by dividing the total pore volume V calculated by the BJH method from pore analysis obtained by gas adsorption by the specific surface area A and multiplying the result by four. In this disclosure, the porosity refers to the ratio of the total pore volume V to the bulk volume, and can be calculated as porosity (%) = total pore volume V / bulk volume × 100. The bulk volume can be calculated based on dimensions such as thickness and area.

[0019] The positive electrode current collector 212 is laminated on a first main surface 211a, which is the surface in the Z1 direction, of the insulating film 211. The positive electrode current collector 212 is a porous body. The positive electrode current collector 212 has a positive electrode porous body 212a and a positive electrode conductive layer 212b.

[0020] The positive electrode porous body 212a is a porous body laminated on the first main surface 211a of the insulating film 211. The average pore diameter of the positive electrode porous body 212a is preferably 10 nm or greater. This ensures excellent lithium ion permeability even when the positive electrode conductive layer 212b is formed within the pores of the positive electrode porous body 212a. Furthermore, the average pore diameter of the positive electrode porous body 212a is more preferably 1 μm or greater. This prevents the pores of the positive electrode porous body 212a from being blocked by the positive electrode conductive layer 212b, even when a sufficient thickness of the positive electrode conductive layer 212b is used to achieve sufficient conductivity. The positive electrode porous body 212a preferably contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide, and includes, for example, a polymer such as polyimide or poly(vinylidene-co-hexafluoropropene). In the present disclosure, polyimide refers to a polymer containing imide bonds. An example of the glass-containing positive electrode porous body 212a is glass filter paper such as GC-50 manufactured by Advantec Corporation. An example of the metal oxide-containing positive electrode porous body 212a is a porous alumina film. This increases the strength of the positive electrode porous body 212a, thereby achieving both electrochemical stability and good mechanical properties for the secondary battery 1.

[0021] The positive electrode conductive layer 212b is a conductive coating that covers the surfaces of the pores of the positive electrode porous body 212a. ４The positive electrode conductive layer 212b is preferably made of a material having a porosity of 0.15 S / m or higher. The positive electrode conductive layer 212b includes a conductor such as aluminum or stainless steel. The thickness of the positive electrode conductive layer 212b is preferably 100 nm or higher, and more preferably 1 μm or higher. This improves electrical conductivity and reduces the internal resistance of the secondary battery 1. The thickness of the positive electrode conductive layer 212b is preferably 10 μm or lower, and more preferably 2 μm or lower. This prevents the positive electrode conductive layer 212b from blocking the pores of the positive electrode porous body 212a, improving electrolyte permeability. Here, the thickness of the positive electrode conductive layer 212b refers to the average thickness of the positive electrode conductive layer 212b along the normal direction to the surfaces of the pores of the positive electrode porous body 212a. The thickness of the positive electrode conductive layer 212b can be measured using a scanning electron microscope.

[0022] The negative electrode current collector 213 is a porous body. The negative electrode current collector 213 includes a negative electrode porous body 213 a and a negative electrode conductive layer 213 b. The negative electrode current collector 213 is laminated on a second main surface 211 b, which is the surface of the insulating film 211 in the Z2 direction.

[0023] The negative electrode porous body 213a is a porous body laminated on the second main surface 211b of the insulating film 211. The average pore diameter of the negative electrode porous body 213a is preferably 10 nm or greater. This ensures excellent lithium ion permeability even when the negative electrode conductive layer 213b is formed in the pores of the negative electrode porous body 213a. The average pore diameter of the negative electrode porous body 213a is preferably 1 μm or greater. This prevents the pores of the negative electrode porous body 213a from being blocked by the negative electrode conductive layer 213b, even when a negative electrode conductive layer 213b with a sufficient thickness is used to achieve sufficient conductivity. The negative electrode porous body 213a preferably contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide, and includes, for example, a polymer such as polyimide or poly(vinylidene-co-hexafluoropropene). An example of the negative electrode porous body 213a containing glass is glass filter paper such as GC-50 manufactured by Advantec Corporation. An example of the negative electrode porous body 213a containing a metal oxide is a porous alumina film. This increases the strength of the negative electrode porous body 213a, enabling the secondary battery 1 to achieve both electrochemical stability and good mechanical properties.

[0024] The negative electrode conductive layer 213b is a conductive coating that covers the surfaces of the pores of the negative electrode porous body 213a. The negative electrode conductive layer 213b includes a conductor such as copper or stainless steel. The thickness of the negative electrode conductive layer 213b is preferably 100 nm or more, more preferably 1 μm or more. This improves electrical conductivity and reduces the internal resistance of the secondary battery 1. The thickness of the negative electrode conductive layer 213b is preferably 10 μm or less, more preferably 2 μm or less. This prevents the pores of the negative electrode porous body 213a from being blocked by the negative electrode conductive layer 213b, improving electrolyte permeability. Here, the thickness of the negative electrode conductive layer 213b refers to the average thickness of the negative electrode conductive layer 213b along the normal direction to the surfaces of the pores of the negative electrode porous body 213a. The thickness of the negative electrode porous body 213a can be measured using a scanning electron microscope.

[0025] The positive electrode active material layer 220 includes one or more positive electrode active materials capable of absorbing and releasing lithium. However, the positive electrode active material layer 220 may further include one or more other materials, such as a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 220 is not particularly limited, and specifically may be a coating method or the like.

[0026] The type of positive electrode active material is not particularly limited, and specifically includes a lithium-containing compound. The lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements. The lithium-containing compound may further contain one or more other elements as constituent elements. The type of the other elements is not particularly limited as long as they are elements other than lithium and transition metal elements, and specifically includes elements belonging to any of Groups 2 to 15 of the long period periodic table.

[0027] The type of lithium-containing compound is not particularly limited, and specific examples of the lithium-containing compound include oxides, phosphate compounds, silicate compounds, and borate compounds. Specific examples of oxides include LiNiO ２ , LiCoO ２ , LiCo ０．９８ Al ０．０１ Mg ０．０１ O ２ , LiNi ０．５ Co ０．２ Mn ０．３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ , Li １．２ Mn ０．５２ Co ０．１７５ Ni ０．１ O ２ , Li １．１５ Mn ０．６５ Ni ０．２２ Co ０．１３ O ２ and LiMn ２ O ４ Specific examples of phosphate compounds include LiFePO ４, LiMnPO ４ , LiFe ０．５ Mn ０．５ P.O. ４ and LiFe ０．３ Mn ０．７ P.O. ４ And so on.

[0028] The positive electrode binder includes one or more synthetic rubbers and polymer compounds. Specific examples of synthetic rubbers include styrene-butadiene rubber, fluorine-containing rubber, and ethylene-propylene-diene. Specific examples of polymer compounds include polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.

[0029] The positive electrode conductive agent contains one or more conductive materials such as a carbon material. Specific examples of the carbon material include graphite, carbon black, acetylene black, and ketjen black. However, the conductive material may also be a metal material or a polymer compound.

[0030] The negative electrode active material layer 230 includes one or more negative electrode active materials capable of absorbing and releasing lithium. However, the negative electrode active material layer 230 may further include one or more other materials, such as a negative electrode binder and a negative electrode conductive agent. The method for forming the negative electrode active material layer 230 is not particularly limited, and may be one or more of a coating method, a vapor phase method, a liquid phase method, a thermal spraying method, and a firing method (sintering method).

[0031] The type of negative electrode active material is not particularly limited, and specifically, it may be one or both of a carbon material and a metal-based material. This allows a high energy density to be obtained. Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite such as natural graphite and artificial graphite. The metal-based material is an element capable of forming an alloy with lithium, and is a material containing one or more elements selected from metal elements and metalloid elements as constituent elements. Specific examples of such elements include silicon and tin. The metal-based material may be one or more of a simple substance, an alloy, and a compound, or may be a mixture or a material containing two or more phases. Specific examples of metal-based materials include TiSi ２ and SiO ｘ (0<x≦2), etc.

[0032] The negative electrode binder may be made of the same material as the positive electrode binder, and the negative electrode conductive agent may be made of the same material as the positive electrode conductive agent.

[0033] The separator 240 is a film that insulates the positive electrode active material layer 220 from the negative electrode active material layer 230. The separator 240 is provided between the main surface of the positive electrode active material layer 220 and the main surface of the negative electrode active material layer 230 so that the positive electrode active material layer 220 and the negative electrode active material layer 230 do not come into direct contact with each other. In the example of FIG. 1 , the shape of the separator 240 is a rectangular sheet when viewed in a plan view in the thickness direction.

[0034] The separator 240 is preferably made of a material that is electrically stable, chemically stable with respect to the positive electrode active material, the negative electrode active material, and the electrolyte, and is insulating. For example, the separator 240 can be made of a polymer nonwoven fabric, a porous film, or a layer containing at least one of glass and ceramic fibers. The separator 240 is more preferably made of a porous polyolefin film. This improves battery safety by preventing short circuits and providing a shutdown effect.

[0035] The separator 240 is not an essential component, and may be replaced with the current collector assembly 210, for example.

[0036] The electrolyte solution is impregnated into the insulating film 211 and the separator 240. In the example of Fig. 1, the electrolyte solution fills the space inside the exterior member 30. The electrolyte solution is a non-aqueous electrolyte solution containing an electrolyte salt and a solvent that dissolves the electrolyte salt.

[0037] The electrolyte salt is, for example, lithium perchlorate (LiClO ４ ), lithium hexafluorophosphate (LiPF ６ ), lithium tetrafluoroborate (LiBF ４ ), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO ２ CF ３ ) ２ ), lithium bis(pentafluoroethanesulfonyl)imide (LiN(SO ２ C ２ F５ ) ２ ), lithium hexafluoroarsenate (LiAsF ６ ) and other lithium salts.

[0038] Examples of the solvent include lactone-based solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone; carbonate-based solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; ether-based solvents such as 1,2-dimethoxyethane, 1-ethoxy-2-methoxyethane, 1,2-diethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; nitrile-based solvents such as acetonitrile; sulfolane-based solvents; phosphoric acids; phosphate ester solvents; and pyrrolidones.

[0039] The electrolyte preferably contains at least one additive selected from the group consisting of fluorinated carboxylic acid esters, sulfonic acid esters, sulfonic acid anhydrides, and carboxylic acid anhydrides. This promotes the formation of a low-resistance solid electrolyte interphase (SEI), thereby improving the charge load characteristics. Examples of fluorinated carboxylic acid esters include fluoroethylene carbonate (FEC). Examples of sulfonic acid anhydrides include propanedisulfonic acid anhydride (PSAH). Examples of sulfonic acid esters include 1,3-propane sultone. Examples of carboxylic acid anhydrides include 1,4-dioxane-2,6-dione.

[0040] The current collector assembly according to the first embodiment is not limited to the one described above, but may be one according to the modified examples described below.

[0041] 3 in that it does not have the positive electrode porous body 212a and the negative electrode porous body 213a. In the first modification, the positive electrode current collector is a positive electrode conductive layer provided on the surface of the pores on the first main surface 211a of the insulating film 211. In the first modification, the negative electrode current collector is a negative electrode conductive layer provided on the surface of the pores on the second main surface 211b of the insulating film 211. Even in this case, carrier ions such as lithium ions can pass through the current collector assembly in the stacking direction, thereby improving the high-rate charge / discharge characteristics.

[0042] 3 in that the positive electrode conductive layer and the negative electrode conductive layer are provided in a portion of the pores of the positive electrode porous body 212a and the negative electrode porous body 213a, respectively. In the second modification, the positive electrode conductive layer and the negative electrode conductive layer are formed, for example, to have a mesh-like shape when viewed in a plan view in the Z direction. In this case, even if the pore diameters of the positive electrode porous body 212a and the negative electrode porous body 213a are made smaller, the pores are not blocked by the positive electrode conductive layer or the negative electrode conductive layer, thereby improving strength.

[0043] Furthermore, the secondary battery according to the first embodiment is not limited to the one described above, but may be one according to the modified examples described below.

[0044] 2 in that a current collector assembly 210 is provided instead of the separator 240. This allows the length of the electron conduction path between the positive electrode current collector 212 and the negative electrode current collector 213, passing through the positive electrode active material layer 220 or the negative electrode active material layer 230, to be further shortened, thereby reducing the current density.

[0045] As described above, the current collector assembly 210 according to the first embodiment includes the insulating film 211 having the first main surface 211a and the second main surface 211b opposite to the first main surface 211a, the positive electrode current collector 212 provided on the first main surface 211a, and the negative electrode current collector 213 provided on the second main surface 211b. The insulating film 211, the positive electrode current collector 212, and the negative electrode current collector 213 are porous.

[0046] This allows carrier ions such as lithium ions to pass through the current collector assembly 210 in the stacking direction. That is, during charge and discharge of the secondary battery 1, carrier ions can move between the positive electrode active material layer 220 and the negative electrode active material layer 230 not only via the separator 240 but also via the current collector assembly 210. This shortens the diffusion distance of carrier ions during charge and discharge reactions, increasing the current that can flow under diffusion resistance control. This prevents the lithium ion concentration from becoming uneven between the positive electrode and the negative electrode, even during high-rate charge and discharge, resulting in the suppression of irreversible capacity due to the generation of metallic lithium, for example. Therefore, the current collector assembly 210 according to the first embodiment can improve high-rate charge and discharge characteristics.

[0047] In a desirable embodiment, the average pore diameter of the positive electrode current collector 212 is 10 nm or more and 50 μm or less. The average pore diameter of the negative electrode current collector 213 is 10 nm or more and 50 μm or less. This makes it possible to prevent the pores of the positive electrode porous body 212 a and the negative electrode porous body 213 a from being blocked by the positive electrode conductive layer 212 b and the negative electrode conductive layer 213 b, respectively, even when the positive electrode conductive layer 212 b and the negative electrode conductive layer 213 b are used with sufficient thicknesses to obtain sufficient conductivity.

[0048] In a preferred embodiment, the insulating film 211 has an average pore size of 10 nm to 50 μm, which allows the insulating film 211 to have both lithium ion permeability and the current collector assembly 210 to have sufficient mechanical strength.

[0049] In a more preferable embodiment, insulating film 211 contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide, which increases the strength of insulating film 211 and allows secondary battery 1 to have both good electrochemical stability and good mechanical properties.

[0050] In a preferred embodiment, the positive electrode current collector 212 has a positive electrode porous body 212a and a positive electrode conductive layer 212b provided on the surfaces of the pores of the positive electrode porous body 212a. The negative electrode current collector 213 has a negative electrode porous body 213a and a negative electrode conductive layer 213b provided on the surfaces of the pores of the negative electrode porous body 213a. This allows carrier ions to pass through the positive electrode current collector 212 and the negative electrode current collector 213 in the thickness direction, and as a result, the ion diffusion distance can be halved compared to conventional methods.

[0051] In a more preferable embodiment, the thickness of the positive electrode conductive layer 212b is 100 nm or more and 10 μm or less. The thickness of the negative electrode conductive layer 213b is 100 nm or more and 10 μm or less. This improves electrical conductivity and reduces the internal resistance of the secondary battery 1, while preventing the positive electrode conductive layer 212b and the negative electrode conductive layer 213b from blocking the pores of the positive electrode porous body 212a and the negative electrode porous body 213a, thereby improving electrolyte permeability.

[0052] In a more desirable embodiment, the positive electrode porous body 212a contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide. The negative electrode porous body 213a contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide. This increases the strength of the positive electrode porous body 212a and the negative electrode porous body 213a, allowing the secondary battery 1 to achieve both electrochemical stability and good mechanical properties.

[0053] As described above, the secondary battery 1 according to the first embodiment includes an insulating film having a first major surface 211a and a second major surface 211b opposite the first major surface 211a, a positive electrode provided on the first major surface 211a, and a negative electrode provided on the second major surface 211b. The positive electrode includes a positive electrode current collector 212 and a positive electrode active material layer 220. The negative electrode includes a negative electrode current collector 213 and a negative electrode active material layer 230. The insulating film 211 is porous. The positive electrode current collector 212 and the negative electrode current collector 213 are porous bodies or porous plates. This allows carrier ions such as lithium ions to pass through the current collector assembly 210 in the stacking direction, thereby improving high-rate charge / discharge characteristics.

[0054] In a preferred embodiment, the positive electrode current collector 212 is provided on the first main surface 211a and is a porous body having a positive electrode porous body and a positive electrode conductive layer provided on the surfaces of the pores of the positive electrode porous body. The negative electrode current collector 213 is provided on the second main surface 211b and is a porous body having a negative electrode porous body and a negative electrode conductive layer provided on the surfaces of the pores of the negative electrode porous body. This can improve the high-rate charge / discharge characteristics.

[0055] In a more desirable embodiment, the battery includes a plurality of current collector assemblies, each of which includes an insulating film 211, a positive electrode current collector 212 provided on the first main surface 211a, and a negative electrode current collector 213 provided on the second main surface 211b. The battery further includes a separator 240. The separator 240 is laminated between a positive electrode active material layer 220 provided on the first current collector assembly 210 and a negative electrode active material layer 230 provided on the second current collector assembly 210. This improves the high-rate charge / discharge characteristics.

[0056] In a more desirable embodiment, the battery has a plurality of current collector assemblies, each of which has an insulating film 211, a positive electrode current collector 212 provided on the first main surface 211a, and a negative electrode current collector 213 provided on the second main surface 211b. The first current collector assembly 210 and the second current collector assembly 210 are stacked with the positive electrode active material layer 220 or the negative electrode active material layer 230 interposed therebetween. This improves the charge / discharge characteristics at high rates.

[0057] A method for manufacturing the current collector assembly according to the first embodiment will now be described. Fig. 4 is a diagram showing the manufacturing process of the current collector assembly according to the first embodiment. As shown in Fig. 4, the manufacturing process of the current collector assembly according to the first embodiment includes a step of preparing an insulating film 211 (step S1), a step of forming a positive electrode porous body 212a and a negative electrode porous body 213a (step S2), and a step of forming a positive electrode conductive layer 212b and a negative electrode conductive layer 213b (step S3).

[0058] In the step of preparing insulating film 211 (step S1), insulating film 211 is prepared by cutting out a sheet of insulating material.

[0059] In the step of forming the positive electrode porous body 212a and the negative electrode porous body 213a (step S2), the positive electrode porous body 212a and the negative electrode porous body 213a are formed on the first main surface 211a and the second main surface 211b of the insulating film 211, respectively. Specifically, for example, pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) are stirred and reacted to obtain a slurry of a microporous polyimide precursor. The obtained slurry is then coated on the first main surface 211a and the second main surface 211b of the insulating film, immersed in a mixed solution of ethanol and water, and dried at room temperature to obtain a composite. The obtained composite is then heated in a box furnace. This allows porous polyimide layers to be formed on the insulating film 211 as the positive electrode porous body 212a and the negative electrode porous body 213a.

[0060] In the step of forming the positive electrode conductive layer 212b and the negative electrode conductive layer 213b (step S3), the positive electrode conductive layer 212b and the negative electrode conductive layer 213b are formed on the surfaces of the pores of the positive electrode porous body 212a and the negative electrode porous body 213a, respectively. Specifically, for example, the positive electrode conductive layer 212b can be formed on the surfaces of the pores of the positive electrode porous body 212a by pulsed DC magnetron sputtering on the positive electrode porous body 212a using the material of the positive electrode conductive layer 212b as a target. Similarly, the negative electrode conductive layer 213b can be formed on the surfaces of the pores of the negative electrode porous body 213a by pulsed DC magnetron sputtering on the negative electrode porous body 213a using the material of the negative electrode conductive layer 213b as a target.

[0061] The manufacturing method described above is an example and is not limited to this. For example, the step (step S2) of forming the positive electrode porous body 212a and the negative electrode porous body 213a may be the following step. Poly(vinylidene-co-hexafluoropropene) (PVDF-HFP) with a molecular weight of approximately 455,000 is dissolved in acetone, and water is added to prepare a precursor slurry. Next, the slurry is applied to the first main surface 211a and the second main surface 211b of the insulating film at room temperature and dried in a vacuum oven to form the positive electrode porous body 212a and the negative electrode porous body 213a.

[0062] Examples will be described below, but the current collector assembly and secondary battery according to the first embodiment are not limited to the following examples.

[0063] The current collector assembly according to Example 1 was prepared in the following manner.

[0064] In the step of preparing an insulating film, a porous aramid film (Kevlar (registered trademark), manufactured by DuPont) having a thickness of 15 μm and a porosity of 65% was prepared as the insulating film.

[0065] In the process (step S2) of forming the positive electrode porous body 212a and the negative electrode porous body 213a, the positive electrode porous body 212a was formed on the first main surface 211a of the insulating film 211, and the negative electrode porous body 213a was formed on the second main surface 211b of the insulating film 211, by the following method. First, a mixture of pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) in a molar ratio of 1:1.02 was added to dimethylformamide while stirring to prepare a honey-like slurry. The honey-like slurry was then applied to the first main surface 211a and the second main surface 211b of the insulating film 211, which was then immersed in a solution of ethanol and water in a volume ratio of 1:1, and dried at room temperature to obtain a composite. The obtained composite was then heated in a box furnace at the following temperature settings (1) to (7) to be imidized. As a result, an insulating film 211 was obtained in which porous polyimide was formed on both sides as the positive electrode porous body 212a and the negative electrode porous body 213a. －１ (2) The temperature is raised (ramp up) from 25°C to 100°C. (3) The temperature is left at 100°C for 30 minutes. －１ (4) Ramp up to 200°C at 200°C for 30 minutes. (5) Ramp up to 200°C at 3°C ​​for 3 minutes. －１ (6) Ramp up to 300°C with a 300°C pressure. (7) Leave at 300°C for 30 minutes. (8) Cool to room temperature.

[0066] In the step of forming the positive electrode conductive layer 212b and the negative electrode conductive layer 213b (step S3), the positive electrode conductive layer 212b and the negative electrode conductive layer 213b were formed on the surfaces of the pores of the positive electrode porous body 212a and the negative electrode porous body 213a, respectively, by the following method. First, the surface of the positive electrode porous body 212a was pretreated with oxygen plasma for 5 minutes. This improved the surface adhesiveness of the positive electrode conductive layer 212b. Then, after 10 minutes of pretreatment, ６ Torr (1.3×10 ８ An Al coating was formed as the positive electrode conductive layer 212b by pulse DC magnetron sputtering using argon as a protective gas at a pressure of 1000 kJ / cm2 or less. Similarly, the surface of the negative electrode porous body 213a was pretreated with oxygen plasma for 5 minutes. This improved the surface adhesiveness of the negative electrode conductive layer 213b. ６ Torr (1.3×10 ８ A Cu coating was formed as the negative electrode conductive layer 213b by pulse DC magnetron sputtering using argon as a protective gas at a pressure of 1000 kJ / cm2 or less.

[0067] Moreover, the secondary battery according to Example 1 was fabricated by the following method.

[0068] The positive electrode active material layer according to Example 1 was prepared by the following method. ０．５ Mn ０．３ Co ０．２ O ２A positive electrode slurry was prepared by mixing NMC (North America, Inc.), a segregated carbon nanotube (CNT) dispersion, and carbon black (Timcal C45 carbon) in butyl benzyl phthalate (Santicizer®). The segregated CNT dispersion was a dispersion in N-methyl-2-pyrrolidone containing 0.4 wt% SWCNT (single-wall carbon nanotubes) and 2 wt% binder (polyvinylidene difluoride). The amounts of raw materials used for the positive electrode slurry were adjusted so that the mass ratio of NMC, SWCNT, carbon black, and binder was 92:1:2:5. The resulting positive electrode slurry was then applied to the PET side of a PET / Al composite film, followed by drying in an oven at 70°C, vacuum drying at 60°C, and then drying in an oven at 120°C to remove the solvent. Then, the positive electrode active material layer was obtained by peeling it off from the PET / Al film.

[0069] The negative electrode active material layer of Example 1 was prepared by the following method. Graphite powder (Superior Graphite SLC1506T) as the negative electrode active material, a segregated CNT (Carbon Nanotube) dispersion, and carbon black (Timcal C45 carbon) were mixed in butyl benzyl phthalate (Santicizer®) to prepare a negative electrode slurry. The segregated CNT dispersion was the same as the segregated CNT dispersion used in preparing the positive electrode active material layer of Example 1. The amounts of raw materials for the negative electrode slurry were adjusted so that the mass ratio of graphite, SWCNT, carbon black, and binder was 86:2:2:10. The obtained negative electrode slurry was then applied to the PET side of a PET / Al composite film, dried in an oven at 70°C, subsequently vacuum dried at 60°C, and then dried in an oven at 120°C to remove the solvent. Then, the negative electrode active material layer was obtained by peeling it off from the PET / Al film.

[0070] The secondary battery of Example 1 was assembled in the following manner. An electrode body was fabricated by laminating a positive electrode active material layer, a positive electrode current collector layer of a current collector assembly, an insulating film, a negative electrode current collector, a negative electrode active material layer, and a separator in this order. The positive electrode conductor coating was connected to a 1 cm-wide strip of Al foil and then to an Al tab. The negative electrode conductor coating was connected to a 1 cm-wide strip of Cu foil using a welding machine and then to a nickel tab. The separator was a porous film (Celgard® 2325) in which a polyethylene sheet was sandwiched between polypropylene sheets. The electrolyte was lithium hexafluorophosphate (LiPF ) in ethylene carbonate / ethyl methyl carbonate (EC / EMC, mass ratio 3:7) containing 2% by mass of fluoroethylene carbonate (FEC, Sigma Aldrich). ６ ) (1.2 mol / L) was used. The prepared electrolyte solution was then impregnated into the insulating film and the separator in an amount that resulted in a battery capacity of 10 g / Ah. The electrode assembly prepared by the above procedure was sealed in an aluminum plastic film to prepare a secondary battery according to Example 1.

[0071] FIG. 5 is an enlarged cross-sectional view showing a portion of the cross section of an electrode body of a secondary battery according to Comparative Example 1. More specifically, FIG. 5 is a cross-sectional view showing a portion of a pair of a positive electrode and a negative electrode of an electrode body 200T. As shown in FIG. 5, the battery according to Comparative Example 1 includes an electrode body 200T having a positive electrode in which a positive electrode active material layer 220 is formed on both sides of a positive electrode current collector 221, a negative electrode in which a negative electrode active material layer 230 is formed on both sides of a negative electrode current collector 231, and a separator 240 between the positive electrode and the negative electrode. The battery according to Comparative Example 1 was fabricated by the following method. A positive electrode active material layer 220 was fabricated by the same method as in Example 1, and the positive electrode active material layer 220 was attached to both sides of an Al foil serving as the positive electrode current collector 221 to fabricate a positive electrode. A negative electrode active material layer 230 was fabricated by the same method as in Example 1, and the negative electrode active material layer 230, serving as the negative electrode current collector 231, was attached to both sides of a Cu foil to fabricate a negative electrode. Here, all positive electrode current collectors were connected to aluminum tabs, and all negative electrode current collectors were connected to nickel tabs. Then, the same separator 240 as in Example 1 was sandwiched between the prepared positive and negative electrodes, and the same amount of the same electrolyte solution as in Example 1 was impregnated into the separator 240. The electrode assembly prepared by the above procedure was sealed in an aluminum plastic film to prepare a secondary battery according to Comparative Example 1.

[0072] <Charge / Discharge Test> A charge / discharge test was conducted on the secondary batteries according to Example 1 and Comparative Example 1. In the charge / discharge test, the secondary batteries were charged and discharged at different charge / discharge rates and different charge times for each cycle. First, as preparation for the charge / discharge test, two charge / discharge cycles were performed, in which the secondary batteries were charged at a constant voltage of 4.2 V and then discharged at a constant current of 0.05 C to 3.0 V. Then, as the charging process, the secondary batteries were charged at a constant current up to 4.2 V, and then charged at a constant voltage after reaching 4.2 V. Here, the constant current charge / discharge rate and charge time (total time for constant current charge and constant voltage charge) were varied for each cycle, as shown in Table 1. Then, as the discharging process, the secondary batteries were discharged at a constant current of 1 C to 3.0 V. In the charge / discharge test, a 5-minute rest period was provided at the end of each charging and discharging process.

[0073]

[0074] FIG. 6 is a graph showing the transition of areal capacity for the secondary batteries according to Comparative Example 1 and Example 1. FIG. 7 is a graph showing the capacity versus rate for the secondary batteries according to Comparative Example 1 and Example 1. The areal capacity shown in FIG. 6 is the discharge capacity per unit area of ​​the current collector. The capacity shown in FIG. 7 is the average value of the discharge capacity for each charge C rate. As shown in FIGS. 6 and 7 , when charging at 1 C, the difference in discharge capacity between Example 1 and Comparative Example 1 was small, but as the charge C rate increased, the capacity of the secondary battery according to Comparative Example 1 rapidly decreased. In particular, when the charge C rate reached 3 C or higher, the capacity of the secondary battery according to Comparative Example 1 significantly decreased. Therefore, it is believed that in Comparative Example 1, irreversible capacity occurred due to the generation of metallic lithium that does not contribute to the charge / discharge reaction, resulting in a decrease in usable capacity. On the other hand, Example 1 maintained a higher capacity than Comparative Example 1 even at a high charge C rate. This demonstrates that the use of a current collector assembly according to the present disclosure suppresses the generation of irreversible capacity and enables sufficient capacity to be obtained even at a high rate.

[0075] FIG. 8A is a diagram showing charge / discharge curves of the secondary battery according to Comparative Example 1. FIG. 8B is a diagram showing charge / discharge curves of the secondary battery according to Example 1. FIGS. 8A and 8B show average charge / discharge curves at charge / discharge rates ranging from 1 C to 5 C. As shown in FIGS. 8A and 8B, the secondary battery according to Example 1 has a longer constant current charging time than the secondary battery according to Comparative Example 1. This is thought to result in a larger usable capacity in Example 1 than in Comparative Example 1. Furthermore, as the charge C rate increased from 1 C to 5 C, the discharge capacity of Comparative Example 1 decreased significantly, whereas the decrease in discharge capacity was suppressed in Example 1. This shows that by using a current collector assembly according to the present disclosure, sufficient capacity can be obtained even at high rates.

[0076] Second Embodiment FIG. 9 is a cross-sectional view showing an example of an electrode assembly of a secondary battery according to a second embodiment. As shown in FIG. 9 , the secondary battery according to the second embodiment differs from the first embodiment in that the current collectors (positive electrode active material layer 220A and negative electrode active material layer 230A) are porous plates. In the present disclosure, a current collector being a porous plate refers to a plate-shaped member made of a metal such as stainless steel or copper, having a large number of holes and a porosity of 10% or more. In the example shown in FIG. 9 , a positive electrode current collector 212A and a negative electrode current collector 213A are provided on the insulating film 211 side of the positive electrode active material layer 220A and the negative electrode active material layer 230A, respectively. That is, the electrode assembly 200A has a structure in which the positive electrode active material layer 220, the positive electrode current collector 212A, the insulating film 211, the negative electrode current collector 213A, and the negative electrode active material layer 230 are stacked in this order. In the following description, providing the current collectors (positive electrode active material layer 220A and negative electrode active material layer 230A) on the insulating film 211 side of the active material layers (positive electrode active material layer 220A and negative electrode active material layer 230A) may be described as a back-to-back method.

[0077] FIG. 10 is an enlarged view of a positive electrode current collector according to the second embodiment. In the second embodiment, the positive electrode current collector 212A is a porous plate laminated on the positive electrode active material layer 220A. The positive electrode current collector 212A includes a porous conductive material, such as a perforated stainless steel (SS) foil. More specifically, as shown in FIG. 10 , the positive electrode current collector 212A has a plurality of holes 212h penetrating in the thickness direction (Z direction). This allows carrier ions of the secondary battery, such as lithium ions, to move in the thickness direction of the positive electrode current collector 212A, thereby improving the charge / discharge characteristics at high rates. Note that in the example shown in FIG. 10 , the positive electrode current collector 212A has circular holes with a diameter of 80 μm, spaced 80 μm apart. However, the shape, diameter, spacing, and arrangement of the holes 212h in the positive electrode current collector 212A are merely exemplary and are not limited thereto. This allows carrier ions such as lithium ions to pass through the positive electrode current collector 212A in the thickness direction.

[0078] In the second embodiment, the negative electrode current collector 213A is a porous plate laminated on the negative electrode active material layer 230A. The negative electrode current collector 213A includes a porous conductive material, such as a copper foil having holes. More specifically, the negative electrode current collector 213A has a plurality of holes 213h penetrating in the thickness direction (Z direction) as in FIG. 10 . Note that the shape, diameter, spacing, arrangement, etc. of the holes in the negative electrode current collector 213A are not limited to those shown in FIG. 10 and may be different from those of the positive electrode current collector 212A.

[0079] In the example of FIG. 10, the positive electrode active material layer 220A and the negative electrode active material layer 230 are porous and have a plurality of pores penetrating in the thickness direction (Z direction) as in FIG.

[0080] The secondary battery according to the second embodiment is not limited to the one described above, but may be one according to the modified examples described below.

[0081] FIG. 11 is a cross-sectional view showing an example of an electrode body of a secondary battery according to a fourth modification. As shown in FIG. 11 , in the secondary battery according to the fourth modification, a positive electrode current collector 212A and a negative electrode current collector 213A are provided on the side of a positive electrode active material layer 220A and a negative electrode active material layer 230A opposite the insulating film 211, respectively. That is, an electrode body 200B according to the fourth modification has a structure in which the positive electrode current collector 212A, the positive electrode active material layer 220, the insulating film 211, the negative electrode active material layer 230, and the negative electrode current collector 213A are stacked in this order. In the following description, providing the current collectors (the positive electrode active material layer 220A and the negative electrode active material layer 230A) on the side of the active material layers (the positive electrode active material layer 220A and the negative electrode active material layer 230A) opposite the insulating film 211 may be referred to as a face-to-face method.

[0082] FIG. 12 is a cross-sectional view showing an example of an electrode assembly of a secondary battery according to a fifth modification. As shown in FIG. 12 , in the secondary battery according to the fifth modification, the positive electrode current collector 212A and the negative electrode current collector 213A are porous plates made of mesh-like metal foil. In the fifth modification, for example, a mesh-like SS foil can be used as the positive electrode current collector 212A, and for example, a mesh-like copper foil can be used as the negative electrode current collector 213A. Here, the mesh-like metal foil may be a sheet made of woven wire-like metal as shown in FIG. 13 (described later) or an expanded metal as shown in FIG. 14 (described later). As a result, as will be described later, there is no need to drill holes in the fabrication of the electrode assembly of the secondary battery. Therefore, in the fifth modification, no pores are provided in the positive electrode active material layer and the negative electrode active material layer.

[0083] As described above, in the secondary battery according to the second embodiment, the positive electrode current collector 212A is a porous plate provided on the insulating film 211 side of the positive electrode active material layer 220A. The negative electrode current collector 213A is a porous plate provided on the insulating film 211 side of the negative electrode active material layer 230A. Even in this case, the high-rate charge / discharge characteristics can be improved.

[0084] In the secondary battery according to the second embodiment, the positive electrode current collector 212A is a porous plate provided on the side of the positive electrode active material layer 220 opposite to the insulating film 211. The negative electrode current collector 213A may be a porous plate provided on the side of the negative electrode active material layer 230A opposite to the insulating film 211. This can further improve the high-rate charge / discharge characteristics.

[0085] A method for manufacturing an electrode assembly for a secondary battery according to the second embodiment will be described below. The manufacturing process for the electrode assembly for a secondary battery according to the second embodiment includes the steps of laminating a current collector on an active material layer, drilling holes in the current collector, and laminating the current collector on an insulating film 211. In the second embodiment, the step of drilling holes in the current collector involves ultraviolet laser cutting to form pores in the current collector, as shown in FIG. 10 . Because the current collector is laminated on the active material layer, holes are also drilled in the active material layer. The laser used here can be, for example, a diode-pumped solid state (DPSS) laser with an ultraviolet laser having a wavelength of 355 nm.

[0086] The process for producing the electrode body of the secondary battery according to the fifth modification includes the steps of laminating a mesh-shaped current collector on the active material layer and laminating the current collector on the insulating film 211. That is, in the fifth modification, the current collector already has gaps, so there is no need to drill holes in the current collector. As a result, no holes are drilled in the active material layer when producing the secondary battery according to the fifth modification.

[0087] Examples will be described below, but the secondary battery according to the second embodiment is not limited to the following examples.

[0088] The secondary battery according to Example 2 was produced by the following method: The secondary battery according to Example 2 is the secondary battery according to the second embodiment.

[0089] First, in the step of laminating a current collector on an active material layer, a 12 μm-thick SS foil was attached as a positive electrode current collector to a positive electrode active material layer similar to that in Example 1 according to the first embodiment, and a 8 μm-thick copper foil was attached as a negative electrode current collector to a negative electrode active material layer similar to that in Example 1 according to the first embodiment.

[0090] Next, in the process of drilling holes in the current collectors, circular holes with a diameter of 80 μm and intervals of 80 μm were drilled in each of the positive and negative current collectors using a diode-pumped solid state (DPSS) laser having an ultraviolet laser with a wavelength of 355 nm, as shown in Fig. 10. This resulted in a porosity of 40% in the positive and negative current collectors.

[0091] Then, in the step of laminating the insulating film 211, the positive electrode current collector and the negative electrode current collector were laminated so as to be in contact with the first main surface 211a and the second main surface 211b, respectively, of the insulating film 211. Thereafter, the same electrolyte solution as in Example 1 of the first embodiment was poured into the insulating film 211, thereby producing a secondary battery according to Example 2.

[0092] The secondary battery according to Example 3 was fabricated in the same manner as in Example 2, except that in the step of laminating the insulating film 211, the positive electrode active material layer and the negative electrode active material were laminated so as to be in contact with the first main surface 211a and the second main surface 211b, respectively, of the insulating film 211. The secondary battery according to Example 3 is a secondary battery according to the fourth modified example.

[0093] Fig. 13 is a diagram showing a positive electrode current collector according to Example 4. Fig. 14 is a diagram showing a negative electrode current collector according to Example 4. The secondary battery according to Example 4 was fabricated in the same manner as in Example 3, except that, in the step of laminating current collectors on active material layers, the woven SS sheet shown in Fig. 13 was attached as a positive electrode current collector to the same positive electrode active material layer as in Example 1 according to the first embodiment, and the copper expand metal shown in Fig. 14 was attached as a negative electrode current collector to the same negative electrode active material layer as in Example 1 according to the first embodiment, and the step of drilling holes in the current collectors was not performed.

[0094] As a first charge-discharge test, a charge-discharge cycle was performed on the secondary battery according to Example 2. First, as preparation for the charge-discharge test, two charge-discharge cycles were performed, in which constant voltage charging was performed at 4.2 V and constant current discharging at 0.05 C to 3.0 V. Then, as a charging process, constant current charging was performed at 1 C to 4.2 V, and after reaching 4.2 V, constant voltage charging was performed. Then, as a discharging process, constant current discharging was performed at 1 C to 3.0 V. In the first charge-discharge test, a 5-minute rest period was provided at the end of each of the charging and discharging processes.

[0095] As a second charge-discharge test, charge-discharge cycles were performed on the secondary batteries according to Examples 2 and 3. First, as preparation for the charge-discharge test, two charge-discharge cycles were performed, in which the secondary batteries were charged at a constant voltage of 4.2 V and then discharged at a constant current of 0.05 C to 3.0 V. Then, as a charging process, the secondary batteries were charged at a constant current of 4.2 V, and then charged at a constant voltage after reaching 4.2 V. Here, the current during the charging process was 1.25 mA up to cycle 20, 2.5 mA from cycle 21 to cycle 40, 5 mA from cycle 41 to cycle 60, 2.5 mA from cycle 61 to cycle 80, and 1.25 mA from cycle 81 to cycle 100. Subsequently, as a discharging process, the secondary batteries were discharged at a constant current of 1 C to 3.0 V. In the second charge-discharge test, a 5-minute rest period was provided at the end of each charging and discharging process.

[0096] As a third charge-discharge test, charge-discharge cycles were performed on the secondary batteries according to Examples 2 and 3. First, as preparation for the charge-discharge test, two charge-discharge cycles were performed, in which the secondary batteries were charged at a constant voltage of 4.2 V and then discharged at a constant current of 0.05 C to 3.0 V. Then, as a charging process, the secondary batteries were charged at a constant current of 4.2 V, and then charged at a constant voltage after reaching 4.2 V. Here, the current during the charging process was 1 C for the first 10 cycles, 2 C from cycles 11 to 20, 3 C from cycles 21 to 30, and 4 C from cycles 31 to 40. Then, as a discharging process, the secondary batteries were discharged at a constant current of 1 C to 3.0 V. In the third charge-discharge test, a 5-minute rest period was provided at the end of each charging and discharging process.

[0097] Fig. 15 is a diagram showing the results of the first charge / discharge test according to Example 2. Here, in Fig. 15, efficiency is the ratio of discharge capacity to charge capacity. As shown in Fig. 15, the secondary battery according to Example 2 suppresses capacity degradation even after 200 cycles or more, and it can be seen that high efficiency is maintained.

[0098] Fig. 16 is a diagram showing the results of the second charge / discharge test according to Examples 2 and 3. As shown in Fig. 16, it can be seen that the secondary battery according to Example 3, which was assembled by the face-to-face method, can achieve a more stable and higher capacity than the secondary battery according to Example 2, which was assembled by the back-to-back method.

[0099] 17 is a diagram showing the results of the third charge / discharge test according to Example 4. As shown in Fig. 17, the secondary battery according to Example 4 using a mesh-like current collector also achieves a high capacity retention rate.

[0100] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and equivalents thereof are also included in the present invention.

[0101] This disclosure includes the contents of U.S. Patent Application No. 63 / 533,319, filed August 17, 2023, as described below.

[0102] In the following description, a porous current collector or PCC (Porous Current Collector) refers to a current collector assembly according to an example of the present disclosure, and a TCC refers to a current collector according to a comparative example of the present disclosure. That is, a PCC is an example of a current collector assembly according to an embodiment of the present disclosure, as shown in FIGS. 2 and 3 . A TCC is also an example of a metal foil current collector, as shown in FIG. 5 . Note that the current collector assembly according to the embodiment of the present disclosure is not limited to the PCC described below. Furthermore, "PCC w / o metal" refers to a PCC without metal, i.e., a PCC without a positive electrode conductor layer and a negative electrode conductor layer, and is the same as a "PCC matrix." Here, "PCC cell," "PCC battery," "PCC pouch cell," and "PCC pouch battery" all refer to batteries having PCC, while "TCC cell," "TCC battery," "TCC pouch cell," and "TCC pouch battery" all refer to batteries having TCC. The notation "NMC|graphite" indicates that NMC is used as the positive electrode active material and graphite is used as the negative electrode active material. The notation "Cu|Al" indicates that copper (Cu) is used as the negative electrode current collector and aluminum (Al) is used as the positive electrode current collector. The term "cathode" is sometimes used to mean "positive electrode," "positive electrode active material layer," or "positive electrode current collector," and the term "anode" is sometimes used to mean "negative electrode," "negative electrode active material layer," or "negative electrode current collector." The term "electrode" is sometimes used to mean "active material layer." Available Li ＋ Transport distance (effective Li + transport distance), effective Li ＋ Transport length (effective Li + transport length), effective Li ＋ Length of effective Li + pathway) and effective Li ＋ Transport route length (effective Li +The terms "dead lithium" and "dead Li" refer to lithium that does not contribute to charge / discharge reactions. The terms "N / P ratio" and "negative / cathode capacity ratio" refer to the ratio of the capacity of the negative electrode to the capacity of the positive electrode.

[0103] ABSTRACT In the field of lithium-ion batteries, achieving extremely fast charging while maintaining high energy density remains a challenge. Diffusion limitations are one of the major factors limiting the rate capability of batteries. In current batteries, solid metal foil current collectors (e.g., Cu and Al) are impermeable to the electrolyte, allowing Li to pass between the two sides of the current collector. ＋ Here, we conceptualize for the first time a porous current collector for high energy density, extremely fast charging batteries. This design allows Li ions to pass through both the porous current collector and the separator, thereby increasing the available Li without compromising the battery's energy density. ＋ Transport distance (effective Li + The transport distance is reduced by half, and the diffusion-limited C-rate capability, i.e., the ratio of the diffusion-limited current value to the capacity, is increased by a factor of four. ２ At an areal cathode loading of 1000 mAh, multilayer pouch batteries equipped with this new current collector exhibited a high energy density of approximately 276 Wh / kg at the whole-cell level. Furthermore, these batteries exhibited remarkable fast-charging capabilities of 4C (15-minute charge, 0% to 78.3% SOC), 6C (10-minute charge, 0% to 70.5% SOC), and 10C (6-minute charge, 0% to 54.3% SOC). This current collector design demonstrates excellent compatibility with current battery manufacturing processes and other fast-charging strategies, opening up new possibilities for high-rate battery design.

[0104] (Introduction) The widespread adoption of electric vehicles (EVs) and the realization of electric aircraft are increasingly dependent on high-energy-density lithium-ion batteries (LIBs). State-of-the-art high-energy-density (>250 Wh / kg) LIBs consist of a nickel-rich layered oxide cathode and a graphite anode. While the use of thick electrodes has enabled EVs to achieve ranges of over 300 miles (approximately 482 km), long charging times remain a significant challenge. As a result, ultra-fast charging has become one of the most sought-after features to accelerate adoption and overcome the barrier of "range anxiety." Ultra-fast charging requires a charging time of less than 15 minutes to go from 0% to 80% state of charge (SOC).

[0105] Diffusion limitations are a significant factor hindering the rate performance of the battery. ＋ Length of effective Li + The diffusion pathway plays a key role and increases with areal loading. Several strategies have been proposed to address the diffusion issue. Thinning the electrode is the primary means to increase the diffusion-limited C rate, but at the expense of reducing the energy density of the battery. Furthermore, electrolyte engineering to improve ionic conduction, Li ＋ Other approaches, such as thermal modulation to enhance the transport of Li and reducing tortuosity to shorten the path length at the electrode, have also been proposed to improve the Li transport in batteries. ＋ However, these strategies may result in trade-offs in terms of electrochemical / thermal stability and energy density.

[0106] Among the various approaches, effective Li ＋ Transport length (effective Li +The diffusion-limited C-rate (DLC), which represents the maximum rate at which lithium ions can diffuse through the electrode and electrolyte and participate in the electrochemical reaction, is expressed by formula (1-1). The charge / discharge C-rate reaches the DLC when the Li ions near the current collector ＋ This means that the concentration reaches 0. DLC is inversely proportional to the square root of the effective electrode thickness (Equation (1-1)). Here, in Equation (1-1), L is the thickness of the electrode. All symbols in Equation (1-1) are explained in Supplementary Note 1 below. When operating beyond DLC, Li ＋ Furthermore, high charge / discharge C rates increase polarization, causing the anode potential to increase toward Li ＋ / Li ０ The potential is lowered below the equilibrium potential. This causes Li to appear on the anode surface. ０ Metallic lithium (Li) known as precipitation ０ ) deposits can form. In the best case scenario, these effects compromise the battery's deployable energy density, reversibility, and lifespan. In the worst case, they can lead to thermal runaway and explosion of the battery.

[0107] Current collectors (TCCs), such as solid metal foils like Cu or Al, lack porosity and are impermeable to the electrolyte (Fig. 18A). ＋ Li between the electrodes does not contribute to the transport ＋ Restrict transport to one direction only.

[0108] 18A to 18C show the design principle of the porous current collector in the battery. Figures 18A and 18B show a multi-layer pouch battery with TCC (Figure 18A) and PCC. In the case of TCC, the Li between the electrodes is dispersed as shown by the black arrow in Figure 18A. ＋ Transport is restricted to one direction only, through the separator. In the case of PCC, Li ＋Transport occurs simultaneously in both directions through both the PCC and the separator. The enlarged view in Figure 18B shows a schematic of the PCC. The PCC is composed of a sandwich of porous, hierarchical polymer stacks coated with two metals. Figure 18C shows a conceptual comparison of the diffusion-limited C rate in TCC and PCC cells. The use of PCC allows for the effective Li ＋ Transport route length (effective Li + The transport path length is half that of the TCC, and the diffusion-limited rate capability of the battery is four times that of the TCC.

[0109] This time, for high-energy batteries (Fig. 18B), we have developed a Li-based current collector and separator. ＋ We have conceptualized for the first time a thin (25 μm) porous current collector (PCC) capable of tunable Li transport. The current collector is composed of a sandwiched, porous, and hierarchical polymer matrix coated on both sides with approximately 1.5 μm thick cathode and anode conductive metals, respectively. Comparing Figures 18A and 18B reveals one important change in the battery cell configuration. While the thickness of each electrode layer remains the same for both the TCC and PCC cases, the anode and cathode arrangement is changed from alternating every two layers (cathode / cathode / anode / anode) to alternating every single layer (cathode / anode / cathode / anode). This modification maintains the high energy density of the battery for both the TCC and PCC cases. However, in the case of the PCC, the available Li ＋ The transport path length was reduced by a factor of two compared to the TCC cell configuration. This reduction in effective diffusion length resulted in a four-fold increase in the diffusion-limited C rate, as conceptually shown in Figure 18C. This multilayer pouch cell with PCC achieved a 3 mAh / cm ２The batteries exhibit a specific energy of approximately 276 Wh / kg at the whole-cell level, with a high cathode capacity areal density of 0.05%. Furthermore, these batteries exhibit excellent diffusion-limited C rates, reaching 4C (15 min charge, 0 to 78.3% SOC), 6C (10 min charge, 0 to 70.5% SOC), and 10C (6 min charge, 0 to 54.3% SOC). This new design makes it possible to achieve high diffusion-limited C rates while using thick electrodes for high-energy-density batteries.

[0110] (Proof of Concept of PCC by Numerical Simulation) To illustrate the concept of PCC, a lithium nickel manganese cobalt oxide (LiNi) ０．５ Mn ０．３ Co ０．２ O ２ A high-energy battery consisting of a TCC (Titanium Dioxide Copolymer) and a PCC (Non-Crystalline Chromatograph) was selected, with graphite as the cathode. Numerical simulations were first performed to better understand the electrochemical processes during fast charging. Figure 19A shows a multilayer pouch cell with TCC and PCC, which represents the battery assembly configuration used in the subsequent demonstration and practical application. In the experiment, a 4C rate (12 mA cm) was used. －２ , C rate is the capacity areal density is 3mAh cm －２ Constant current charging was employed (based on a 1000 W NMC cathode). The cells were charged to a cutoff voltage of 4.2 V and held at 4.2 V until the total charge time reached 15 minutes. Figure 19B shows the distribution of lithium concentration in the active material for the two different cell configurations. Dark red indicates high lithium concentration, and dark blue indicates low lithium concentration.

[0111] At TCC, Li ＋Due to transport limitations, the lithium concentration in TCC batteries is highly nonuniform across the electrode thickness. In the left image of Figure 19B, graphite particles near the separator exhibit a high lithium concentration of approximately 1.0, while those farther from the separator exhibit a low lithium concentration of approximately 0.3. In the cathode, NMC particles also exhibit a nonuniform lithium concentration ranging from 0.4 to 0.6. Previous studies (Yang, Y. et al. Adv. Energy Mater. 9, 1900674 (2019). and Xu, R. et al. J. Mech. Phys. Solids 129, 160-183 (2019)) have shown that such nonuniform electrochemical processes in batteries can damage the active material particles and their interfaces, resulting in irreversible capacity fade during battery cycling.

[0112] On the other hand, in PCC, Li ＋Ions can transport through both the separator and the PCC, effectively reducing the effective transport length by a factor of two and significantly reducing the non-uniformity of lithium distribution. As shown in the right panel of Figure 19B, the lithium distribution within the graphite anode varies minimally, from a fully lithiated state (lithium concentration 1.0) at the side of the anode surface to an 80% lithiated state (lithium concentration 0.8) at the center of the anode. At the same time, the lithium distribution within the NMC cathode is quite uniform, with a lithium concentration of approximately 0.34. It is noteworthy that due to the high tortuosity of the graphite anode, the distribution of Li ions in NMC and graphite is different compared to the NMC cathode. As a result, Li ion transport is suppressed in the graphite anode, resulting in a larger gradient in the Li ion distribution. The more uniform utilization of active material in the battery with PCC can be observed at different states of charge (e.g., 2.5 V, 3.8 V, and 4.2 V) as shown in Figures 19C, 19D, and 23A, 23B. In Figures 19C, 19D, and 23A, 23B, the distribution of lithium in the electrode is plotted along the thickness direction of the electrode. The results show that the battery with PCC exhibits less voltage polarization and higher available capacity compared to the battery with TCC (Figure 19E). This difference in polarization and available capacity can be attributed to a higher charge C-rate (Figure 19F) or thicker electrodes (9 mAh cm). －２, Figures 24A and 24B). Figure 19F shows the simulation of the SOC of TCC and PCC batteries under two different charging protocols. (1) When charged using a simple constant current (CC, dashed line) mode at a cutoff voltage of 4.2 V, the PCC battery exhibited a significantly higher SOC than the TCC pouch battery. The SOC of the PCC cell was most improved at an 8 C charge rate. Above this rate, lithium depletion occurred. This lithium depletion was similar to that observed in the TCC case, although the charge C rate was much lower than that of the PCC. (2) When charged using a combination of constant current and constant voltage (CC-CV, solid line) modes to a cutoff voltage of 4.2 V until a specific charge time was reached, the SOC of the PCC battery was observed to be significantly higher than that of the TCC battery. At a 4 C CC-CV charging mode, the PCC cell could reach an SOC of 92.4% within 15 minutes. In the 8C CC-CV charging mode, the PCC cell can reach 85.7% SOC within 11.6 minutes.

[0113] Figures 19A to 19H show the numerical simulation results for batteries with TCC and PCC, respectively. Figure 19A shows the multilayer pouch cell configuration with TCC and PCC, respectively. Figure 19B shows the lithium concentration maps of the electrodes of two battery units with TCC and PCC, respectively, when charged at a cutoff voltage of 4.2 V. Figures 19C and 19D show the lithium concentration distributions along the electrode thickness at different charging voltages (2.5 V, 3.8 V, and 4.2 V) for the battery with TCC. Figure 19D shows the lithium concentration distributions along the electrode thickness at different charging voltages (2.5 V, 3.8 V, and 4.2 V) for the battery with PCC. Figure 19E shows the charging curves of the TCC and PCC batteries at 4 C when the total charging time was adjusted to 15 minutes. Figure 19F shows the normalized capacity of the batteries with TCC and PCC under different charging protocols. 19G and 19H show the change in the electrode potential Ect on the anode surface near the separator when charged at 4 C and 6 C, respectively.

[0114] Another challenge in fast charging batteries is the ０ The possibility of precipitation occurs, which often starts on the surface of the graphite particles in the anode due to uneven utilization of the graphite in the anode. During fast charging, the graphite particles near the separator rapidly reach a high SOC of 1.0, causing Li ０ Premature deposition may occur. The anode electrode potential is E ｃｔ =η ｉｎｔ +E ｅｑ where η ｉｎｔ is Li to graphite ＋ is the overpotential for intercalation of ｅｑ is the equilibrium potential for Li intercalation into graphite. During fast charging, the graphite particles near the separator rapidly reach 100% SOC, so E ｅｑ falls to 0, resulting in E ｃｔ becomes lower than 0, and Li ０ Precipitation may occur.

[0115] To quantitatively compare the possibility of Li deposition in cells with TCC and PCC, the E ｃｔ The evolution of E was analyzed (Fig. 19G and Fig. 19H). ｃｔ It was observed that E gradually decreased to a low value and reached a minimum value at the end of CC charging. For TCC batteries, E ｃｔ The minimum values ​​of Li are about −0.143 V and about −0.209 V, respectively, and ０ On the other hand, in PCC batteries, E ｃｔ The value was -0.029 V at a charge rate of 4 C and -0.049 V at 6 C, indicating that Li ０ Furthermore, as shown in the spatial distribution of the graphite anode potential at a charge rate of 4 C, the anode of the PCC battery shows a more uniform distribution in the thickness direction of the graphite electrode than the TCC battery (Figs. 25A and 35B). Therefore, the battery with PCC exhibits a more uniform distribution of the Li ０It has high resistance to precipitation and is expected to improve safety during rapid charging.

[0116] PCC Design and Fabrication Based on initial analysis, we determined that achieving our goals required a PCC design that integrated the functions of the current collector (both the cathode and anode) and the separator. Therefore, we developed a three-layer hierarchical porous PCC (Figure 20A). To ensure excellent electrochemical stability (Figures 26A and 26B) and good mechanical properties, we used a bulletproof, thin, nanoporous Kevlar membrane (Figures 20B and 20C; average pore size: 500 nm, porosity: 65%, thickness: 15 μm) as the primary separator substrate. Kevlar is one of the strongest polymers and is often used in body armor due to its bulletproof properties, making it suitable for use as a current collector. Furthermore, the Kevlar separates the two electrodes, preventing potential electrical shorts during battery operation. Then, we coated both sides of the Kevlar membrane with a layer of microporous polymer (approximately 5 μm thick) using a phase separation method (see Fabrication Methods). The pore size of the surface coating layer was optimized to about 3 μm to 4 μm to satisfy both the criteria of good electrolyte permeability and the subsequent thick metal coating (FIGS. 20D and 20E). If the pore size is too small, the metal coating will block the pore structure, preventing Li+ from entering the pores. ＋ This may interfere with the transport of

[0117] Figures 20A through 20J illustrate the main design concepts and properties of PCC. Figure 20A is a schematic of the PCC manufacturing process. Figures 20B through 20G are SEM images. Figures 20B and 20C are SEM images showing the morphology of the bulletproof Kevlar membrane. Figures 20D and 20E are SEM images showing the morphology of the PCC matrix. Figures 20F and 20G are SEM images showing the morphology of the PCC. The image shown in Figure 20E is a digital image of the PCC matrix. Figure 20H is an energy dispersive X-ray spectroscopy image showing the distribution of metal across the thickness of the PCC (SEM images are shown in Figures 28A and 28B). Figure 20I illustrates the variation of current collection resistance with length. Figure 20J compares the ionic conductivities of a commercial separator, a PCC matrix, and a PCC.

[0118] Next, metallic Cu and Al were coated on each side of the composite PCC matrix. With a sufficiently thick metal coating, the electrical conductivity has a negligible effect on cell resistance. The thickness of the metal coating was optimized to 1.5 μm to ensure high electrical conductivity of the PCC. The metal coating maintains the submicron pore size of the surface layer, allowing rapid electrolyte penetration through the PCC (Figures 20F and 20G). As confirmed by cross-sectional SEM images (Figures 28A and 28B) and energy-dispersive X-ray spectroscopy images (Figure 20H), the tortuosity of the microporous polymer coated on the Kevlar ensures that the conductive metal is coated only on the surface layer. Therefore, there is no electronic connection between the electrodes on both sides of the PCC, and the intermediate Kevlar layer remains unoccluded by the metal. The porosity of PCC plays an important role in various aspects of battery performance, including electronic and ionic conductivity, mechanical stability, thermal behavior, and electrochemical performance (Figures 29A to 29D).

[0119] Compared with TCCs using Cu foil (approximately 120 GPa) and Al foil (approximately 70 GPa), PCC exhibited a high Young's modulus of 35.3 GPa (Fig. 30), with a Young's modulus of 4.67 × 10 ７ The PCC cells exhibited high electronic conductivity of 300 S / m (Figures 31A to 31C). Electrical calculations were also performed for two PCC cell designs, including welded and tabless configurations (Figures 20I and 33). The tabless configuration effectively reduced the current collector resistance in 18650-type cells (3 Ah). In the tabless PCC cell, we were able to achieve a resistance of less than 10 mΩ for current collectors with lengths within a practical range (800 nm to 1000 nm).

[0120] To evaluate the electrolyte permeability of PCC, we compared ionic conductivities through blocking cells assembled with different porous films including polyethylene (PE, Celgard 2500), a trilayer polyolefin separator (Celgard 2325), a trilayer PCC polymer matrix (PCC w / o metal), and PCC (Figures 20J and 33). 1 mol / L LiPF in a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3:7) with 2 wt% fluoroethylene carbonate was used. ６ was used as the electrolyte. Both PCC w / o metal (0.942 mS / cm) and PCC (0.918 mS / cm) were found to exhibit much higher ionic conductivities than commercially available polyethylene (0.254 mS / cm) and Celgard 2325 (0.62 mS / cm) separators. In the fabrication of PCC, the ionic conductivity of the porous current collector only slightly decreased after metal coating. This is due to several factors: (1) The porosity of the PCC is well maintained after metal coating, allowing fast ion transport and ensuring high ionic conductivity. (2) The metal coating minimizes its effect on the tortuosity of the pores, thereby maintaining the ion transport pathways. (3) The electrophilic nature of PCC promotes electrolyte redistribution within the PCC, minimizing the decrease in ionic conductivity. Furthermore, the contact angle between PCC and the electrolyte (approximately 2°) was much smaller than that between a commercially available separator (Celgard 2325) and the electrolyte (approximately 34°), demonstrating the electrophilicity of PCC (Figure 34).

[0121] A solid foil (8 μm thick Cu with a surface weight of 7.2 mg / cm ) was used as a current collector. ２ , 12 μm thick Al has a surface weight of 3.2 mg / cm ２ Compared to a cell configuration using a PCC, the PCC design reduces the areal weight of the current collector to 2.2 mg / cm ２This significantly reduces the total cell mass, potentially reducing the battery's "dead weight" by approximately 8% at the whole-cell level. It is also worth mentioning that the new PCC concept is a universal design that can be used with a variety of material choices. Various conductive coatings (e.g., carbon nanotubes, porous metal membranes) and porous films (e.g., commercially available separators, poly(vinylidene fluoride-co-hexafluoropropylene)) could be combined to construct this hierarchical PCC (Figures 35A to 35E).

[0122] (Ultrafast Charge Capability of PCC Multilayer Pouch Battery) Figures 21A through 21G show the electrochemical performance of multilayer pouch batteries with TCC and PCC. Figure 21A shows the rate performance of multilayer pouch batteries with TCC and PCC. Figure 21B shows a comparison of the available capacity of pouch batteries after charging at rates ranging from 1 C to 10 C by adjusting the overall CC-CV charging time. Figures 21C and 21D show the charge-discharge curves of pouch batteries with TCC (Figure 21C) and PCC (Figure 21D). Here, the cells are charged at different rates and discharged at a C-rate of 1 C to a cutoff voltage of 3 V. Figure 21E shows a comparison of the fast charge and fast discharge capacities of TCC and PCC pouch cells from 1 C to 10 C. 21F and 21G show the charge-discharge curves of the pouch cells using a TCC (FIG. 21F) and a PCC (FIG. 21G) at high rate charge-discharge protocols.

[0123] To fabricate pouch batteries with PCC, high stability was achieved by incorporating segregated Tuball® carbon nanotubes into thick electrodes (Fig. 36, Fig. 37A to Fig. 37F). These segregated networks have a capacity of 3 mAh cm. －２ to 9mAh cm －２This contributes to the formation of crack-free electrodes with high areal capacities. The resulting electrodes were then calendered with either TCC or PCC (Figure 38) to assemble multilayer pouch cells. These cells, with a negative / cathode capacity ratio of 1.1, were combined with Celgard 2325 separators and the aforementioned electrolytes and sealed in aluminum plastic film. High capacity areal densities (3 mAh cm) were achieved. －２ Due to the reduced current collector weight and the reduced capacitance, large-sized PCC pouch batteries can achieve a specific energy density of approximately 276 Wh / kg (Supplementary Note 2). To evaluate the rate performance, we used an optimized CC-CV protocol in which the total charge time of CC and CV reached a specific value based on the charge rate (e.g., 1 hour for 1C, 30 minutes for 2C, etc.). This protocol replaces the common charging protocol using CC-CV mode with a cutoff current of 0.5C held at 4.2V, as described in the paper (Song, M. & Choe, S.-YJ Power Sources 436, 226835 (2019)).

[0124] Figure 21A shows the surface discharge capacity of the pouch cell at 1C after charging at various C rates ranging from 1C (1-hour charge) to 10C (6-minute charge). To examine the available capacity after rapid charging at different C rates and eliminate the effect of potential "dead capacity," the cells were fully discharged at 1C to 3.0V and the discharge capacities were compared. After 1C charge, the deliverable discharge capacity of the TCC and PCC pouch cells was very similar, indicating that lithium ion transport was fast enough to participate in the electrochemical reaction in both battery configurations. However, as the charge C rate increased, the capacity of the TCC pouch cell rapidly decreased. At charge C rates above 3C (20-minute charge), lithium depletion became severe, resulting in a significant capacity drop. Even with the same high charge C rate, the available discharge capacity of the TCC case continued to decrease due to the occurrence of irreversible capacity. This decrease in available capacity was mainly due to the Li ion transport caused by the large overpotential. ０ Due to precipitation, "dead lithium" is generated, forming a reversible SEI and sacrificing effective capacity. In contrast, PCC exhibits much higher and more stable capacity at high charge C rates compared to TCC. As shown in Figure 21B, the capacities of the PCC pouch cell at 4C (15 min charge), 6C (10 min charge), and 10C (6 min charge) are 78.3% (TCC: 62.3%), 70.5% (TCC: 33.4%), and 54.3% (TCC: 13.8%) of SOC, respectively.

[0125] Figures 21C and 21D show the charge-discharge curves of the multilayer pouch battery with TCC and PCC. As confirmed by the numerical simulation in Figure 19E, the CC charging portion of the pouch battery with PCC is much longer than that with TCC due to the significant polarization of electrolyte concentration. A long CC charging portion is an important indicator of fast charging capability, as it can contribute to higher capacity. Therefore, the use of PCC significantly increases the available capacity. As the charging C rate increases from 1 C to 5 C, the capacity of the TCC pouch battery decreases exponentially, indicating that the Li concentration in a particular electrode is increasing. ＋The PCC cells exhibit a rapid depletion of lithium, beyond which the active material is no longer available. In contrast, the PCC cells exhibit a nearly linear decay trend, suggesting that mass transport does not significantly affect the rate behavior below 5 C. However, as the charge C rate increases above 5 C, the capacity fade rate of the PCC cells accelerates, indicating an increasing level of lithium depletion. At higher charge C rates (>10 C), we expect to observe rapid capacity fade due to various factors, including increased concentration polarization and particle breakage.

[0126] Effective Li ＋ The halving of the transport path length also promises to improve the high-rate discharge capability of the multilayered battery. Therefore, after the optimized CC-CV charging mode described above, we tested the high-rate discharge performance at C rates ranging from 1C to 10C using a cutoff voltage of 3.0V. As shown in Figure 21E, the TCC pouch battery only achieved limited capacity at a high discharge rate of 4C after a full charge (15-minute charge) at 4C. During this process, both the charge resistance and the lithium ion transport rate contributed to a large overpotential, sacrificing the capacity of the TCC. In contrast, the PCC pouch battery showed a much lower decay rate. Even at a 5C discharge, the discharge capacity of the PCC was still 52.2% after a 5C charge (12-minute charge). Figures 21F and 21G show the charge-discharge curves of the multilayered pouch batteries with TCC and PCC under high-rate discharge scenarios. The overpotential for the PCC was much smaller than that for the TCC, which is reflected in the position of the charge-discharge plateau at the same charge-discharge C rate.

[0127] (Li in PCC pouch cells revealed by differential pressure sensing) ０ As mentioned above, when charging at an extremely fast rate, a large overvoltage occurs, causing Li ＋ Intercalation potential is Li / Li ＋ This can cause Li to be deposited on the anode surface. ０ The presence of precipitated lithium can react violently with the electrolyte, resulting in the formation of "dead lithium", a decrease in coulombic efficiency, and a rapid loss of capacity. ０Dendrites can penetrate the separator and cause internal short circuits, posing a serious safety risk. ０ We have demonstrated a differential pressure sensing technique to accurately monitor deposition. We measure the real-time change in cell pressure per unit charge (dP / dQ) and measure the Li deposition rate to the anode. ＋ By comparing with a threshold defined based on the maximum value of dP / dQ during the intercalation of Li ０ During fast charging, PCC can trap Li before the precipitate grows extensively. ０ To better understand how this affects Li deposition, a multilayer NMC|graphite pouch cell was combined with differential pressure sensing, allowing real-time monitoring of Li deposition during operation. ０ The deposition can be monitored.

[0128] The multilayer PCC and TCC pouch cells were assembled and initially cycled at a C / 20 rate for two cycles. Then, the cells were stacked with a wooden force distribution plate and pressure sensor, and clamped in a vise with a fixed thickness (Figs. 22A, 39A). The total CC-CV time was then adjusted, and the cells were charged using the optimized CC-CV protocol described above, and discharged at 1 C until a voltage of 3.0 V was reached (Figs. 22B, 39B). During this process, the real-time cell pressure was simultaneously recorded (Figs. 22C, 39C). The change in pressure behavior correlates with the charge-discharge behavior of the pouch cell and is mainly governed by the volumetric change of the graphite. The base pressure, i.e., the pressure after full discharge, is determined by the Li ０ This serves as an indirect indicator of Li deposition. The formation of "dead Li" and residual SEI increases the irreversible thickness of the anode, resulting in an increase in residual pressure after each cycle. The base pressure of the TCC and PCC pouch cells is stable below 2 C and 5 C, respectively, and Li ０ However, as the charge / discharge C rate further increases (>2 C for TCC and >5 C for PCC), Li deposition ０ It is shown that residual SEI and "dead lithium" are formed and accumulated as a result of the precipitation.

[0129] 22A to 22G show the Li ０ Figure 22A shows the configuration for operando pressure measurement of a multilayer pouch cell during ultrafast charging. Figures 22B and 22C show the charge-discharge curves (Figure 22B) and pressure evolution (Figure 22C) of an NMC|graphite multilayer pouch cell with PCC cycled at charge-discharge C rates ranging from 1 to 10 C. The pressure fluctuations in the first cycle are caused by the initial pressure adjustment, but do not affect the differential value dP / dQ and therefore the subsequent pressure response. Figures 22D and 22E show the Li deposition in PCC (Figure 22D) and TCC (Figure 22E) cells. ０ dP / dQ profile of a battery charged at a slow charge rate to establish the threshold for Li deposition. ０ Figures 22F and 22G show the dP / dQ profiles of the PCC (Figure 22F) and TCC (Figure 22G) cells charged at different charge / discharge C rates. All discharge protocols were set to 1 C with a cutoff voltage of 3.0 V. To process the dP / |dQ| data, the rest period after charge / discharge was excluded from the data analysis.

[0130] Li ０ Further analysis was performed to study the deposition behavior, plotting the differential pressure dP / |dQ| for TCC and PCC pouch cells (FIGS. 22D and 22E). ０ The threshold for precipitation was determined by selecting the maximum dP / dQ observed at low charge / discharge C rates. The maximum dP / dQ values ​​determined at 1 C for PCC and 0.5 C for TCC were selected because the SOCs after charge were similar. The rest periods after charge / discharge were excluded from the data analysis.

[0131] From the charging rates of 1C (1 hour charge) and 4C (15 minutes charge), dP / |dQ| for PCC remains in the sub-threshold region (blue region), indicating that the anode is Li ＋However, when the charging rate is increased above 5 C, the dP / |dQ| curve crosses a threshold and the Li ０ The upper region (orange region) where Li precipitates, ０ This phenomenon became more pronounced at 10 C (6 min charging) and above. As shown in Figure 22F, in the case of PCC, the peak dP / |dQ| at 4 C or below was ＋ In contrast, in the case of TCC (Fig. 22G), Li ０ In the TCC cell, the maximum value of dP / |dQ| increased from 3 C to 6 C and then decreased from 8 C to 10 C, which was mainly due to the charging process proceeding directly to the CV step from 8 C to 10 C, and the CC part of the TCC cell was not clearly observed at such a high charge / discharge C rate.

[0132] (Extended PCC) Even with fast charging, the PCC design also has great potential for enhancing the battery capacity areal density, resulting in higher battery energy without compromising rate capability. Notably, the PCC pouch cell has a capacity of 6 mAh cm －２ The battery exhibits stable cycling performance for 200 cycles at a charge / discharge rate of 1 C under a high positive electrode (NMC) capacity areal density (Fig. 40A). Therefore, it is possible to achieve an energy density of approximately 287 Wh / kg while maintaining the theoretical charge rate of the battery (Fig. 41B).

[0133] This innovative PCC design offers high energy density and high rate capability, showing great potential for advancing energy storage device design. We expect that the rate capability of this design will be further improved by adopting a tabless-less design in the future. By slightly modifying the electrode coating method, this new battery design maintains maximum compatibility with existing battery manufacturing methods, facilitating the implementation of tabless-less designs in the near future. Furthermore, the introduction of PCC instead of a separator can alleviate local current concentration and promote uniform reactions with the battery system (Figures 42A to 42D).

[0134] Summary In summary, we first conceptualized a porous current collector for high-energy and fast-charging batteries. This design allows for the transport of Li through both the porous current collector and the separator. ＋ It allows simultaneous passage of ions and increases the effective Li without compromising the electrode thickness. ＋ The transport path length was reduced by a factor of two. As a result, the diffusion-limited C rate of high-energy batteries can be increased by a factor of four. The porous current collector is formed of a three-layer hierarchical porous polymer matrix coated on either side with Cu and Al. A multilayer pouch battery with this porous current collector achieved a capacity of 3 mAh / cm. ２ Experimental results demonstrate that this porous current collector design provides remarkable rate capabilities of 4C (15 min charging, 0 to 78.3% SOC), 6C (10 min charging, 0 to 70.5% SOC), and 10C (6 min charging, 0 to 54.3% SOC) while maintaining a high capacity areal density of 1000 mAh and a specific energy of approximately 276 Wh / kg at the whole cell level. Furthermore, this porous current collector design supports Li-ion batteries up to 5C. ０ They exhibit improved resistance to precipitation, enhancing the reversibility and safety of lithium-ion batteries under fast charging. The benefits of porous current collectors could have broad implications for the fast-charging capabilities of next-generation energy storage devices.

[0135] (Fabrication Method) 1. Fabrication of Porous Current Collectors (PCCs) 1.1 Fabrication of Three-Layer and Hierarchical PCC Matrices A bulletproof porous paper-like aramid membrane (Kevlar) with a thickness of 15 μm and a high nano-sized porosity of 65% was used as the main substrate polymer for the PCC. Based on reverse phase separation, microporous polyimide (PI) with tunable pore size was coated on both sides of the Kevlar to form the PCC host. Specifically, the PI precursor was prepared based on the reaction of pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA). ODA and PMDA were added to dimethylformamide in a molar ratio of 1:1.02 under vigorous stirring. The reaction was continued overnight to confirm complete polymerization. The honey-like slurry was then coated onto a Kevlar separator and immersed in a 1:1 volumetric mixture of ethanol and ethanol. ２The composite was then immersed in O solution and then dried at room temperature overnight. The composite was then imidized in a box furnace to form a PI-Kevlar membrane using a step ramping program. Details of the step ramping program are provided in the "Supplementary Manufacturing Methods" section.

[0136] 1.2 Alternative PCC Matrix Fabrication Poly(vinylidene-co-hexafluoropropene) (PVDF-HFP, weight-average molecular weight approximately 455,000) was first dissolved in acetone (10 wt%), and mixed precursor solutions were prepared by gradually adding water to various water contents (0 wt%, 5 wt%, 10 wt%, and 15 wt%). The resulting slurry was then applied to both sides of a commercial separator or Kevlar membrane at room temperature. The samples were dried in a vacuum oven at 60°C for 2 days before use.

[0137] 1.3 PCC manufacturing PCC host ２ The surface was pre-treated with plasma for 5 minutes to enhance the surface adhesion of the metal coating. ６ Torr (1.3×10 ８ Porous conductive Cu and Al layers were deposited on both sides of the porous polymer substrate, respectively, by pulsed DC magnetron sputtering using argon as protective gas at a pressure of 0.1 Pa or less.

[0138] 2. Electrode Fabrication Method Both the cathode and anode composite electrodes were prepared by slurry casting using a segregated carbon nanotube (SWCNT) dispersion (Tuball, OCSiAl) consisting of 0.4 wt% single-wall carbon nanotubes (SWCNT) and 2 wt% binder (polyvinylidene difluoride) in N-methyl-2-pyrrolidone, the active material (NMC or graphite), and carbon black (Timcal, C45 carbon).

[0139] For the anode, the CNT dispersion (including the binder) was mixed with graphite powder (Superior Graphite SLC1506T) and carbon black. Since a specific amount of binder was already included in the CNT dispersion, no additional binder was required. The mass fraction of graphite:CNT:carbon black:binder in the resulting electrode was adjusted to 86%:2%:2%:10% by adjusting the mass ratio. For example, 25 ml of the CNT dispersion was mixed with 4.2 g of graphite, 100 mg of carbon black, and 400 mg of butyl benzyl phthalate (santicizer) to obtain an electrode with 2 wt% CNTs. The slurry was then cast onto the PET side of a polyethylene terephthalate / aluminum (PET / Al) film. The electrode was then dried overnight in an oven at 70 °C, followed by vacuum drying at 60 °C for two days, and then overnight in an oven at 120 °C to remove residual solvent. Electrodes of various thicknesses can be obtained by varying the doctor blade spacing. The dried electrodes can be peeled off from the PET / Al film by bending. Single electrodes can be cut to specific area sizes and placed on Cu foil (Cu on TCC) or on the Cu side of PCC for calendering.

[0140] For the cathode, LiNi was used to mix with the CNT dispersion and carbon black. ０．５ Mn ０．３ Co ０．２ O ２NMC (Toda America, Inc.) was used. The mass fraction of active material, CNT, carbon black, and binder in the resulting electrode was adjusted to 92%, 1%, 2%, and 5%. For example, 25 ml of CNT dispersion was mixed with 9.2 g of NMC, 300 mg of carbon black, and 400 mg of butyl benzyl phthalate (santicizer) to obtain an electrode containing 1.0 wt% CNT. The slurry was then cast onto the PET side of a PET / Al film as an anode. The electrode can be peeled off from the PET / Al film by bending and drying in the same manner as the anode. A separate cathode electrode can be cut to a specific area size and placed on an Al foil (Al for TCC) or the Al side of PCC for calendering.

[0141] Battery Assembly: NMC|graphite multilayer pouch cells were assembled with Cu|Al TCC and the PCC electrodes prepared above. Two additional end electrodes cooperate to balance the capacity of the PCC pouch cells, as shown in Figure 43B. In the TCC pouch cells, all negative current collectors were connected to nickel tabs, and all positive current collectors were connected to Al tabs. In the PCC pouch cells, all Cu metal sides of the PCC were connected to strips of Cu foil (1 cm wide) with a welder and then to nickel tabs, and all Al metal sides of the PCC were connected to strips of Al foil (1 cm wide) and then to Al tabs. A polypropylene-polyethylene-polypropylene (Celgard 2325) porous film was used as the separator for both the TCC and PCC pouch cells. Lithium hexafluorophosphate (LiPF) in ethylene carbonate / ethyl methyl carbonate (EC / EMC, weight ratio 3:7) containing 2 wt% fluoroethylene carbonate (FEC, Sigma Aldrich) ６) (1.2 mol / L) was used as the electrolyte for full-cell measurements. The electrolyte usage in the pouch battery was 10 g / Ah. The total capacity of the pouch cells with TCC and PCC was adjusted to be the same. Therefore, the dimensions of the TCC cathode, TCC anode, PCC cathode, and PCC anode were 1.3 in. x 1.3 in. (3.3 cm x 3.3 cm), 1.4 in. x 1.4 in. (3.6 cm x 3.6 cm), 1.15 in. x 1.15 in. (2.9 cm x 2.9 cm), and 1.25 in. x 1.25 in. (3.2 cm x 3.2 cm), respectively. Cell cycling was performed at currents up to 5 A. Both the TCC and PCC pouch batteries were initially cycled twice by charging to 4.2 V and discharging to 3.0 V at a current density of 0.05 C. The pouch battery is then charged at a constant current (up to 4.2V) and a constant voltage (hold at 4.2V) according to the charge rate (1 hour for 1C, 30 minutes for 2C, etc.) until the total charge time reaches a specific value, and then discharged at the same C rate as 1C. For the fast charge / discharge protocol, the charge protocol is the same, but the discharge rate is set to a constant current discharge from 1C to 10C until the voltage reaches 3V. A 5-minute pause is added at the end of each charge and discharge step.

[0142] (Operando Pressure Test) A wooden block (length x width x height: 2 inches x 2 inches x 1 inch (5 cm x 5 cm x 2.5 cm)) larger than the center of the cell was attached to the pouch cell as a force distribution plate. The multilayer pouch cell, which had been charged and discharged twice, was clamped in a vice along with a pressure measurement device (LBC-500, Transducer Techniques). After the device was left inactive for 6 hours before the test, pressure data collection and battery cycling were started simultaneously.

[0143] (Numerical Modeling Simulation) The numerical model is constructed based on the theory of Ohm's law developed by Newman et al. (Doyle, M., Fuller, T. F. & Newman, J. J. Electrochem. Soc. 140, 1526 (1993).) Specifically, the charge balance in the electrode is expressed by the following equation (2-1): Here, iｃ is the current density in the electrode defined by Ohm's law and is expressed by the following formula (2-2). Here, K ｃ is the electrical conductivity, φ ｓ is the potential of the NMC cathode or graphite anode.

[0144] Using Fick's law (the following formula (2-3)), the Li in the active material particles (i.e., NMC and graphite) ＋ To calculate the solid-state diffusion of , pseudo-dimensionality (P2D) was used in the porous electrode phase. Here, J ｓ is the Li in the active material particles ＋ represents the flux, and D ｓ is the Li in the active material particles ＋ represents the diffusion coefficient.

[0145] The theory of condensed electrolytes was used to describe the charge balance and mass transport in the electrolyte. The charge balance in the electrolyte is expressed by the following equation (2-4): Here, the current in the electrolyte (i ｌ ) is Li ＋ It is governed by the diffusion and movement of and can be described by the following equation (2-5). where φ ｌ is the potential of the electrolyte, K ｌ is the ionic conductivity of the electrolyte, C ｌ is the Li in the electrolyte ＋ concentration, R is the gas constant, T is the temperature, F is the Faraday constant, t ＋ Li ＋ is the transfer number, and f is the average molar activity coefficient of the electrolyte. The Butler-Volmer equation (Equation (2-6) below) is used to describe the relationship between the charge transfer rate (i) and the overpotential (η). where α ａ is the anodic charge transfer coefficient, α ｃ is the cathode charge transfer coefficient, i ０ is the exchange current density, and η is the overvoltage that drives the charge transfer reaction, which is defined by the following equation (2-7): where φ ｅｑ is the equilibrium potential of the lithiation or delithiation of the NMC cathode and graphite anode. The exchange current density i０ is defined as follows: Here, k ｃ is the rate constant of the anodic reaction, k α is the rate constant of the cathode reaction, C ｓ is the bulk Li in the active material ＋ Concentration, C ｓ＿ｍａｘ is the maximum Li in the active material ＋ Concentration, C ｌ＿ｒｅｆ is the reference Li in the electrolyte ＋ Concentration.

[0146] Li in the electrolyte ＋ The mass transport of is defined as follows: Here, J ｌ is the Li in the electrolyte ＋ Flux, D ｌ is the Li in the electrolyte ＋ represents the diffusion coefficient.

[0147] The effective charge and mass transport properties in porous electrodes with liquid electrolyte were corrected using the tortuosity ε and porosity τ. Here, D ｅｆｆ is the effective transport property (e.g., Li ion diffusion coefficient, ionic conductivity), and D ｂｕｌｋ is the bulk transport coefficient of the electrolyte.

[0148] All simulations were performed using modeling software (COMSOL Multiphysics®). For details of the modeling, please refer to previous research (Xu, R. et al. Journal of the Mechanics and Physics of Solids 129, 160-183 (2019)). The electrochemical parameters of the numerical model were set to match the experimental setup, as shown in Table 2. Two battery configurations were used in the simulation: a six-layer battery with TCC and PCC. In the PCC configuration, six repeating units of separator / anode / PCC / cathode were assembled. The PCC unit was set to have the same porosity of 40% as the separator containing the electrolyte. For both the TCC and PCC configurations, the cathode thickness was 3.0 mAh cm. -２The cathode has a fixed thickness of 70 μm and an N / P ratio of 1.1. The cathode has a two-area capacity of 3.0 mAh cm -２ and 9.0 mAh cm -２ The simulation was performed using a 1.1 N / P ratio. The C rate was calculated based on the cathode areal density. Other parameters, such as porosity, migration number, diffusion coefficient, and tortuosity, are shown in Table 2. In Table 2, the unit "1" indicates a dimensionless number.

[0149]

[0150] (Resistance Simulation) Electrical resistance was calculated using a cylindrical lithium-ion battery, an 18650-type lithium-ion battery, as a model. For the TCC, the width and thickness of the current collector were 54 mm and 12 μm for the cathode (Al), and 57 mm and 8 μm for the anode (Cu). For the PCC, both the cathode and anode were 1.5 μm thick. The measured electrical conductivity was 4.67 × 10 for the anode of the PCC and TCC, respectively. ７ S / m and 5.6 x 10 ７ S / m, and 3.14 × 10 for PCC and TCC, respectively, at the cathode. ７ S / m and 3.77 x 10 ７ It was S / m.

[0151] Material Characterization: The in-plane electrical conductivity of the PCC and TCC was measured using a four-probe technique. Four parallel contact lines were deposited on the electrode surface using silver conductive paste. The morphology and microstructure of the samples were investigated using a field emission SEM (Apreo S LoVac Scanning Electron Microscope, Thermo Fisher Scientific) in high vacuum mode with an accelerating voltage of 5 keV. Mechanical measurements were performed using an Instron 5565 tensile tester (100 N load cell) at a strain rate of 0.5 mm min. -１The contact angle measurements were performed on a single sample at a strain rate of 100 s. Contact angle measurements were performed with a contact angle goniometer (Rame-Hart® 290). Ionic conductivity was measured by electrochemical impedance spectroscopy with an electrochemical measurement system (Biologics, VMP3) in the frequency range of 1 MHz–100 mHz. Cyclic voltammetry was performed at a scan rate of 0.5 mV s. －１ and measured by an electrochemical measurement system (Biologic, VMP3) in a voltage window of 0 V to 5 V. The porous current collector on the TCC was fabricated by a UV laser cutter with a wavelength of 355 nm (model 3530-30, diode-pumped solid-state built-in, Samurai marking System).

[0152] (Supplementary information on the manufacturing method) The temperature ramping program for PI imidization was set as follows: (1) 3°C min -１ (2) Ramp from 25°C to 100°C. (3) Leave at 100°C for 30 minutes. －１ (4) Ramp up to 200°C. (5) Leave at 200°C for 30 minutes. －１ (6) Ramp up to 300°C with a 300°C heater. (7) Cool to room temperature in the furnace.

[0153] (Supplementary information 1: Diffusion-limited C-rate model) "Diffusion-limited C-rate" (DLC) is a model in which Li ＋ The theoretical maximum charging rate when the concentration drops to 0 is shown (Equation (3-1)). where z, F, ε, γ, c Ｌｉ ０ , ω, ρ, Q ｍ and L are the valence, Faraday constant, porosity, tortuosity, initial Li ion concentration in the electrolyte, mass fraction of the active material, apparent density of the composite, gravimetric capacity of the active material and thickness of the electrode layer, respectively.

[0154] (Supplementary information 2: Battery weight energy density of TCC and PCC pouch batteries) Battery information: Total capacity: 3 Ah Electrode size: 100 mm x 50 mm Al current collector: 12 μm (3.24 mg / cm ２), Cu current collector: 8 μm (7.2 mg / cm ２ ) PCC: 25 μm (2.2 mg / cm ２ ) Separator size: 105 mm x 55 mm, 0.5 mg / cm ２ Pouch: 110 mm x 60 mm, thickness 0.112 mm (18.04 mg / cm ２ ) NMC cathode (active material 92% by weight, 165mAh / g ＮＭＣ ) Graphite anode (active material 92 wt%, 300 mAh / g ｇｒａｐｈｉｔｅ ) N / P ratio = 1.1, electrolyte: 1.2 g / Ah Weight energy density at pouch cell level = battery capacity x nominal voltage / pouch cell weight: In the case of TCC, it is as shown in the following formula (3-2). In the case of PCC, it is as shown in the following formula (3-3).

[0155] (Supplementary Drawing) Figure 23A shows a high NMC capacity areal density of 3 mAh / cm ２ Figure 23B shows the lithium concentration distribution of NMC|graphite multilayer pouch cells with TCC at high NMC capacity areal densities of 3 mAh / cm and N / P ratios of 1.1. ２ FIG. 10 shows the lithium concentration distribution of NMC|graphite multilayer pouch cells with PCC at an N / P ratio of 1.1 and 1.2.

[0156] FIG. 24A shows a high NMC capacitance areal density of 9 mAh / cm ２ Figure 24B shows the lithium concentration distribution of NMC|graphite multilayer pouch cells with TCC at a high NMC capacity areal density of 9 mAh / cm and an N / P ratio of 1.1. ２ Figure 1 shows the lithium concentration distribution of an NMC|graphite multilayer pouch battery with PCC at an N / P ratio of 1.1. The simulation was performed at a charge rate of 1C (1 h charge). Improving the capacity areal density can reduce the percentage of "dead weight" in the battery, thereby increasing the specific energy of the battery.

[0157] 25A and 25B show the spatial distribution of graphite anode potential with TCC and PCC at a charge rate of 4C (15 min charge), respectively. The lithium concentration distribution along the thickness of the graphite electrode was symmetrical in the case of PCC, but asymmetrical in the case of TCC. The distribution of Li in both directions in the case of PCC was ＋ The transport is unidirectional in the case of TCC. ＋ Rather than transport, this contributes to a better uniformity of the anode potential.

[0158] Figures 26A and 26B illustrate the electrochemical stability of porous Kevlar® membranes in batteries. Figure 26A shows the chemical structure of the Kevlar membrane, which is the intermediate layer of PCC. Figure 26B shows the cyclic voltammogram (CV) curves of one cycle of a Li|stainless steel battery using Celagrad 2325 and Kevlar, respectively.

[0159] Both curves showed low current response over a wide electrochemical potential window from 0 to 5 V, demonstrating the Kevlar membrane's great electrochemical stability. The cyclic voltammograms of the Li / stainless steel battery with the Kevlar separator were also compared with those with a polyolefin separator (Celgard 2325). Polyolefin separators are known for their high saturation and stability as battery separators. The two batteries exhibited very similar behavior, further demonstrating the stability of the Kevlar membrane within the battery.

[0160] Figure 27A shows an SEM image of a Celgard 2500 separator before and after Cu metal coating. Figure 27B shows an SEM image of a Celgard 2500 separator after Cu metal coating. Because of the thick metal coating required, neither battery separators (Celgard 2500) nor Kevlar films can be directly used as substrates for PCCs because their small pore structures (less than a few hundred nanometers) are completely blocked. Furthermore, the low affinity between the coating metal and polyethylene can result in observable cracks. It is worth mentioning that chemical bonding between the coating metal and the substrate is important for improving the stability of PCCs.

[0161] Figure 28A shows cross-sectional SEM images of PCC at low magnification and Figure 28B shows cross-sectional SEM images of PCC at high magnification.

[0162] 29A to 29D show lithium distribution in PCC cells with different porosities.

[0163] The porosity of PCC plays an important role in various aspects of battery performance, including electronic conductivity, ionic conductivity, mechanical stability, thermal behavior, and electrochemical performance (Figures 29A to 29D). To better understand the effect of porosity, we conducted studies to evaluate the impact on the Li concentration distribution in the electrode by varying the porosity of PCC from 0.2 to 0.8 (Figures 29A to 29D). Lower porosity values ​​(e.g., 0.2) resulted in a more non-uniform distribution of Li concentration within the electrode. On the other hand, higher porosity (e.g., 0.8) did not significantly affect the Li concentration, as Li transport within the porous electrode was the limiting factor in this situation.

[0164] Figure 30 shows the mechanical performance of PCC tested on an Instron 5565. The Young's modulus of PCC is 35.3 GPa, which is comparable to that of Al (about 70 GPa) and Cu (about 120 GPa) current collectors. The bulletproof Kevlar membrane gives PCC strong mechanical properties, providing sufficient strength for future roll-to-roll applications.

[0165] Figure 31A is a diagram illustrating the four-probe method for measuring the electronic conductivity of TCC and PCC. Figure 31B is a diagram illustrating the four-probe method for measuring the electronic conductivity of TCC. Figure 31C is a diagram illustrating the four-probe method for measuring the electronic conductivity of PCC. Figure 31A is a circuit diagram showing the mechanism of the four-terminal electronic conductivity test. Figure 31B is a digital image showing the Cu current collector of the TCC. Figure 31C is a digital image showing the PCC. The difference in color is due to the difference in roughness between the solid Cu current collector and the PCC.

[0166] 32A to 32C illustrate batteries with different tab configurations and their current collector resistances. FIG. 32A shows a double-sided tab configuration and current collector resistance R proportional to the length of the current collector. ｔａｂ FIG. 32B shows the current collector resistance R, which is inversely proportional to the length of the current collector and the table-less structure. ｔａｂ－ｌｅｓｓ FIG. 32C shows the current collector resistance as a function of current collector length.

[0167] The battery shown in Figure 32A consists of two metal tabs, one positive and one negative, used to connect to the ends of the electrodes. These tabs function as contacts for current flow. However, this design results in a longer electron path. In contrast, the tabless battery shown in Figure 32B does not require these tabs. Instead, the electrodes are directly integrated into the battery casing. Electrical connections in a tabless battery are typically achieved by direct soldering or welding to the integrated electrodes. As a result, the electron path is significantly shortened. This reduction in the electron path length reduces the overall internal resistance of the battery and improves its electrical performance. As a result, as shown in Figure 32C, a PCC incorporating a tabless structure can achieve a resistance of less than 10 mΩ over a practical range of current collector lengths (18650-type LIB, 3 Ah, 800 mm to 1000 mm, shaded area in Figure 32).

[0168] Figure 33 illustrates the configuration of the blocking cell for ionic conductivity testing. Four types of separators, Celgard 2500, Celgard 2325, PCC matrix, and PCC, were tested under the same conditions.

[0169] Figure 34 shows the electrolyte wettability of PCC compared to that of Celgard 2325, measured by contact angle measurements. The electrolyte contact angle on PCC (2°) is much smaller than the contact angle on the Celgard 2325 separator (34°), indicating better electrolyte wettability of PCC. This improved wettability can enhance the diffusion-limited C rate of PCC pouch cells.

[0170] Figures 35A through 35E illustrate an alternative fabrication of a three-layer polymer matrix as a potential PCC host. Figure 35A shows a schematic (top panel) and digital image (bottom panel) of a commercially available Celgard 2500 separator coated with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). Figures 35B through 35E show that different pore sizes can be tailored by adjusting the phase separation solvent concentration in the PVDF-HFP solution from 0 wt% to 15 wt%. PVDF-HFP was dissolved in acetone, and different percentages of water were added to the slurry. The slurry was applied to the separator by doctor blade coating. The rapid evaporation of acetone prevented precipitation of PVDF-HFP into the pores of the commercial separator. The use of commercially available separators has many advantages, including (1) low cost, (2) high resistance to internal short circuits, and (3) compatibility with current manufacturing processes.

[0171] Figure 36 shows the stability of thick electrodes using carbon black and isolated Tuball carbon nanotube networks as conductive additives. NMC slurries in N-methyl-2-pyrrolidone were coated onto commercial Al current collectors or the Al side of PCC with different thicknesses. All electrodes shown here were dry but not calendered.

[0172] Figures 37A to 37F illustrate the fabrication of electrodes using Tuball carbon nanotubes. Figure 37A shows that segregated tubular nanotubes can be easily obtained from a single electrode by coating a carbon nanotube dispersion onto an aluminum / polyethylene terephthalate (Al / PET) film. Figure 37B shows a single NMC electrode with 1 wt% Tuball carbon nanotube loading. Figure 37C shows a bending test of an NMC electrode using Tuball carbon nanotubes. Figure 37D shows an electrode that can be cut to size for different purposes. Figures 37E and 37F are SEM images showing that Tuball carbon nanotubes encapsulate NMC and graphite particles in the electrode. This contributes to high electrode stability and electronic conductivity even at high capacitance areal densities.

[0173] Figure 38 shows the calendering and alignment of the electrode to the PCC. By optimizing the electrode slurry with a network of segregated Tuball carbon nanotubes and coating it on the PET side of the PET / Al substrate, both the NMC and the graphite anode can be easily peeled off with the aid of calendering pressure and realigned to the PCC. The same is true for the alignment of the electrode to the TCC.

[0174] 39A to 39C show the Li during fast charging of the TCC. ０ Figure 39 shows differential pressure sensing revealing precipitation. Figure 39A shows the configuration for operando pressure measurement of a multilayer pouch cell during ultra-fast charging. Figures 39B and 39C show the charge-discharge curves (Figure 39B) and pressure changes (Figure 39C) of an NMC / graphite multilayer pouch battery with a TCC cycled at different charge-discharge C rates. For the TCC, no obvious constant current portion was observed during the charging process when the charge rate was 5 C or higher.

[0175] Figure 40A shows the dP / |dQ| curves of a pouch battery with PCC at 4 C. Figure 40B shows the dP / |dQ| curves of a pouch battery with PCC at 5 C. Figure 40C shows the dP / |dQ| curves of a pouch battery with PCC at 10 C. The pressure increase per unit capacity caused by lithium deposition is due to Li ＋ The area above the dashed line represents the pressure increase induced by Li during charging. ０ This indicates that deposition of

[0176] Figures 41A and 41B show the electrochemical performance of batteries with PCC and TCC. Figure 41A shows the cycling performance of pouch batteries with PCC and TCC at 1 C with different capacity areal densities. Figure 41B shows the calculated gravimetric energy density of large-scale 3 Ah batteries with TCC and PCC. Battery information for the calculations is provided in Appendix 2.

[0177] FIG. 42A is a diagram illustrating a TCC cell structure. FIG. 42B is a diagram illustrating a PCC cell structure with a separator. FIG. 42C is a diagram illustrating a PCC cell structure without a separator. FIG. 42D is a diagram illustrating that a PCC cell structure without a separator has the effect of reducing PCC current density. FIGS. 42A and 42B show a single-layer TCC (FIG. 42A) and a PCC cell structure (FIG. 42B) and their current density distributions. FIG. 42C shows a single-layer separatorless PCC cell structure and its current density distribution on the PCC. FIG. 42D shows the current density profiles of a PCC and a separatorless PCC. The calculation conditions are the same as those shown in the center diagram of FIG. 23B, and the calculation was performed at 3 mAh / cm. ２ The conditions are 4C, 3.8V charging.

[0178] In the PCC cell, the TCC in Figure 41A is replaced with the PCC in Figure 42B, and this design successfully reduces the effective lithium ion path length by a factor of two.

[0179] Furthermore, when the separator in a PCC cell is replaced with PCC, especially in a separator-less PCC cell (Fig. 42C), the replacement PCC can act as an additional current collector layer, further shortening the electron path in the battery by half and reducing the effective current density per unit area (Fig. 42D).

[0180] Figure 43A shows the construction of a multi-layer pouch battery with a TCC, and Figure 43B shows the construction of a multi-layer pouch battery with a PCC. The end electrodes of the PCC cell are half the thickness of the other electrodes to prevent overcharge / overdischarge during battery cycling.

[0181] Figure 44A illustrates the fabrication of a proof-of-concept PCC fabricated by UV laser cutting. Figures 44B-44E illustrate proof-of-concept PCCs fabricated by UV laser cutting. Figures 44F and 44G illustrate the performance of a proof-of-concept PCC fabricated by UV laser cutting. Figure 44A shows the scheme for coating a standard electrode onto a metal current collector and then cutting it with a diode-pumped solid-state (DPSS) laser with an ultraviolet (UV) laser at a wavelength of 355 nm. Figure 44B illustrates the design pattern for electrode cutting, showing an 80 μm diameter and spacing with a 40% porosity. Figures 44C and 44D are optical images showing the structure of the NMC cathode and graphite anode after UV laser cutting. Figure 44E illustrates the assembly configuration of a battery to compare the effectiveness of PCCs and validate the concept of the porous current collector design. Figure 44F shows the cycling performance of the NMC|graphite cell assembled by the back-to-back method, and Figure 44G shows the rate performance of the NMC|graphite cell assembled by the back-to-back and face-to-face methods shown in Figure 44E.

[0182] Figures 45A and 45B show a porous stainless steel (SS) mesh. Figures 45C and 45D show a porous copper (Cu) mesh. Figure 45E shows a PCC design using a porous stainless steel (SS) mesh and a porous copper (Cu) mesh. Figure 45F shows the validation of a PCC design using a porous stainless steel (SS) mesh and a porous copper (Cu) mesh. Figure 45A shows a digital image of an NMC cathode calendered on a porous SS mesh. Figure 45B shows an SEM image showing the morphology of a porous SS mesh before and after calendering with an NMC electrode. Figure 45C shows a digital image of a graphite (Gr) anode calendered on a porous Cu mesh. Figure 45D shows an SEM image showing the morphology of a porous Cu mesh before and after calendering with a graphite electrode. FIG. 45E shows the scheme of the NMC|graphite (Gr) full cell with PCC based on the back-to-back assembly method, and FIG. 45F shows the rate performance of the NMC|graphite (Gr) full cell with PCC based on the back-to-back assembly method.

[0183] To experimentally verify the feasibility of PCCs, we fabricated an ion-shunting PCC using a laser-induced current collector (FIGS. 44A-44G) and a porous metal mesh (FIGS. 45A-45F). The porous current collector includes two layers of metal mesh on both sides and a single layer of non-conductive porous polymer in the middle.

[0184] The above content is intended to facilitate understanding of the present invention, and is not intended to be interpreted as limiting the present invention. The present invention may be modified or improved without departing from the spirit thereof, and equivalents thereof are also included in the present invention.

[0185] The present disclosure may also take the following forms: (1) A current collector assembly including an insulating film having a first main surface and a second main surface opposite the first main surface, a positive electrode current collector provided on the first main surface, and a negative electrode current collector provided on the second main surface, wherein the insulating film, the positive electrode current collector, and the negative electrode current collector are porous. (2) The current collector assembly according to (1), wherein the positive electrode current collector has an average pore diameter of 10 nm or more and 50 μm or less, and the negative electrode current collector has an average pore diameter of 10 nm or more and 50 μm or less. (3) The current collector assembly according to (1) or (2), wherein the insulating film has an average pore diameter of 10 nm or more and 50 μm or less. (4) The current collector assembly according to any one of (1) to (3), wherein the insulating film contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide. (5) The current collector assembly according to any one of (1) to (4), wherein the positive electrode current collector has a positive electrode porous body and a positive electrode conductive layer provided on the surfaces of the pores of the positive electrode porous body, and the negative electrode current collector has a negative electrode porous body and a negative electrode conductive layer provided on the surfaces of the pores of the negative electrode porous body. (6) The current collector assembly according to (5), wherein the positive electrode conductive layer has a thickness of 100 nm or more and 10 μm or less, and the negative electrode conductive layer has a thickness of 100 nm or more and 10 μm or less. (7) The current collector assembly according to (5) or (6), wherein the positive electrode porous body contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide, and the negative electrode porous body contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide. (8) A secondary battery comprising: an insulating film having a first main surface and a second main surface opposite to the first main surface; a positive electrode provided on the first main surface; and a negative electrode provided on the second main surface, wherein the positive electrode has a positive electrode current collector and a positive electrode active material layer, the negative electrode has a negative electrode current collector and a negative electrode active material layer, the insulating film is a porous body, and the positive electrode current collector and the negative electrode current collector are porous bodies or porous plates.(9) The secondary battery according to (8), wherein the positive electrode current collector is a porous body provided on the first main surface and having a positive electrode porous body and a positive electrode conductive layer provided on surfaces of the pores of the positive electrode porous body, and the negative electrode current collector is a porous body provided on the second main surface and having a negative electrode porous body and a negative electrode conductive layer provided on surfaces of the pores of the negative electrode porous body. (10) The secondary battery according to (9), wherein the secondary battery includes a plurality of current collector assemblies, each having the insulating film, the positive electrode current collector provided on the first main surface, and the negative electrode current collector provided on the second main surface, and further includes a separator, wherein the separator is laminated between the positive electrode active material layer provided on a first current collector assembly and the negative electrode active material layer provided on a second current collector assembly. (11) The secondary battery according to (9), comprising a plurality of current collector assemblies each having the insulating film, the positive electrode current collector provided on the first main surface, and the negative electrode current collector provided on the second main surface, wherein a first current collector assembly and a second current collector assembly are stacked with the positive electrode active material layer or the negative electrode active material layer interposed therebetween. (12) The secondary battery according to (8), wherein the positive electrode current collector is a porous plate provided on the insulating film side of the positive electrode active material layer, and the negative electrode current collector is a porous plate provided on the insulating film side of the negative electrode active material layer.

[0186] REFERENCE SIGNS LIST 1 secondary battery 20 battery element 21 positive electrode lead 22 negative electrode lead 30 exterior member 30a, 30b exterior sheet 31 recess 32 adhesive material 200, 200A, 200B, 200T electrode body 210 current collector assembly 211 insulating film 212, 212A, 221 positive electrode current collector 212a positive electrode porous body 212b positive electrode conductive layer 213, 213A, 231 negative electrode current collector 213a negative electrode porous body 213b negative electrode conductive layer 220, 220A positive electrode active material layer 230, 230A negative electrode active material layer 240 separator

Claims

1. A collector assembly comprising: an insulating film having a first main surface and a second main surface opposite the first main surface; a positive electrode current collector provided on the first main surface; and a negative electrode current collector provided on the second main surface, wherein the insulating film, the positive electrode current collector, and the negative electrode current collector are porous.

2. The current collector assembly according to claim 1, wherein the positive current collector has an average pore diameter of 10 nm or more and 50 μm or less, and the negative current collector has an average pore diameter of 10 nm or more and 50 μm or less.

3. The collector assembly according to claim 1, wherein the insulating film has an average pore size of 10 nm or more and 50 μm or less.

4. The current collector assembly according to claim 1, wherein the insulating film comprises at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide.

5. The current collector assembly according to claim 1, wherein the positive current collector has a positive electrode porous body and a positive electrode conductive layer provided on the surfaces of the pores of the positive electrode porous body, and the negative current collector has a negative electrode porous body and a negative electrode conductive layer provided on the surfaces of the pores of the negative electrode porous body.

6. The current collector assembly according to claim 5, wherein the positive electrode conductive layer has a thickness of 100 nm or more and 10 μm or less, and the negative electrode conductive layer has a thickness of 100 nm or more and 10 μm or less.

7. The current collector assembly according to claim 5, wherein the positive electrode porous body contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide, and the negative electrode porous body contains at least one of polyolefin, polyimide, polyamide, polyester, cellulose, glass, and metal oxide.

8. A secondary battery comprising: an insulating film having a first main surface and a second main surface opposite to the first main surface; a positive electrode provided on the first main surface; and a negative electrode provided on the second main surface, wherein the positive electrode has a positive electrode current collector and a positive electrode active material layer, the negative electrode has a negative electrode current collector and a negative electrode active material layer, the insulating film is a porous body, and the positive electrode current collector and the negative electrode current collector are porous bodies or porous plates.

9. The secondary battery described in claim 8, wherein the positive electrode current collector is a porous body provided on the first main surface, the porous body having a positive electrode porous body and a positive electrode conductive layer provided on the surfaces of the pores of the positive electrode porous body, and the negative electrode current collector is a porous body provided on the second main surface, the porous body having a negative electrode porous body and a negative electrode conductive layer provided on the surfaces of the pores of the negative electrode porous body.

10. A secondary battery as described in claim 9, comprising a plurality of collector assemblies each having the insulating film, the positive electrode collector provided on the first main surface, and the negative electrode collector provided on the second main surface, and further comprising a separator, the separator being laminated between the positive electrode active material layer provided on a first of the collector assemblies and the negative electrode active material layer provided on a second of the collector assemblies.

11. The secondary battery described in claim 9, comprising a plurality of current collector assemblies each having the insulating film, the positive electrode current collector provided on the first principal surface, and the negative electrode current collector provided on the second principal surface, wherein the first current collector assembly and the second current collector assembly are stacked with the positive electrode active material layer or the negative electrode active material layer interposed therebetween.

12. The secondary battery according to claim 8, wherein the positive electrode current collector is a porous plate provided on the insulating film side of the positive electrode active material layer, and the negative electrode current collector is a porous plate provided on the insulating film side of the negative electrode active material layer.

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