Electrode plate and lithium ion battery

Abstract

The invention relates to an electrode pole piece and a lithium ion battery in the technical field of lithium batteries, the electrode pole piece comprises an electrode pole piece and a diaphragm, the electrode pole piece comprises a current collector and an active material layer at least arranged on one side of the current collector, the electrode pole piece further comprises a functional layer, one side of the functional layer is attached to the active material layer, and the diaphragm is arranged between the active material layer and the functional layer. The other side of the functional layer is attached to the diaphragm, and the functional layer comprises an inorganic solid electrolyte, a polymer and a conductive agent. The functional layer is arranged on the electrode plate, so that the interface stability and the electrochemical working window of the diaphragm and the active substance layer are improved, and the inorganic solid electrolyte, the polymer solid electrolyte and the conductive agent in the functional layer act together, so that the internal resistance of the battery can be reduced, and the lithium ion cycle performance is improved; and thus, the fast charge and high-rate discharge performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to an electrode plate and a lithium ion battery. Background Art

[0002] Since its development, lithium-ion batteries have been increasingly used in various fields such as electric vehicles, consumer electronics, and energy storage. In order to better meet the market demand for fast charging and high-rate discharge of lithium batteries, it is necessary to reduce the internal resistance of lithium batteries.

[0003] For lithium-ion batteries, solid electrolytes have good lithium ion conductivity, chemical stability, electrochemical stability and thermal stability. Therefore, coating the surface of the electrode current collector with a solid electrolyte coating can reduce the internal resistance of the battery and improve the safety of the battery. However, a single solid electrolyte coating only has lithium ion conductivity, and its electronic conductivity is extremely low, which cannot conduct electricity and thus affects the battery's cycle performance.

[0004] Therefore, there is an urgent need for an electrode plate to reduce the internal resistance of the battery, improve the cycle performance of the battery, and further improve the fast charging and high-rate discharge performance of the battery. Summary of the invention

[0005] In order to solve the above problems, the present invention discloses an electrode plate and a lithium-ion battery. The technical solution of the present invention is implemented as follows:

[0006] The first aspect of the present invention discloses a battery cell unit, comprising an electrode plate and a separator, wherein the electrode plate comprises a current collector and an active material layer at least arranged on one side of the current collector, and the electrode plate further comprises a functional layer;

[0007] One side of the functional layer is bonded to the active material layer, and the other side of the functional layer is bonded to the separator;

[0008] The functional layer includes an inorganic solid electrolyte, a polymer and a conductive agent.

[0009] Preferably, the polymer is a polymer solid electrolyte.

[0010] Preferably, the inorganic solid electrolyte includes at least one of a sulfide solid electrolyte, an oxide solid electrolyte and a halide solid electrolyte.

[0011] Preferably, the mass ratio of the inorganic solid electrolyte, the polymer solid electrolyte and the conductive agent is (5%-99%): (1%-94%): (0.01%-10%).

[0012] Preferably, the mass ratio of the polymer solid electrolyte in the functional layer is 50%-90%.

[0013] Preferably, the functional layer is compounded on the active material layer by dry transfer.

[0014] Preferably, the thickness of the functional layer is 0.5 μm to 10 μm.

[0015] Preferably, the electrode plate is a positive electrode plate, the current collector is a positive electrode current collector, and the active material layer includes a positive electrode active material, a conductive agent and a binder.

[0016] Preferably, the electrode plate is a negative electrode plate, the current collector is a negative electrode current collector, and the active material layer includes a negative electrode active material, a conductive agent and a binder.

[0017] The second aspect of the present invention discloses a lithium-ion battery, which includes the battery cell unit as described in the first aspect.

[0018] The present invention improves the interface stability and electrochemical working window between the diaphragm and the active material layer by arranging a functional layer on the electrode plate. The inorganic solid electrolyte, polymer solid electrolyte and conductive agent in the functional layer work together to reduce the internal resistance of the battery, improve the lithium ion cycle performance, and further improve the fast charging and high-rate discharge performance of the battery. At the same time, in the present invention, the functional layer is compounded onto the active material layer by dry transfer, which can avoid the solid electrolyte entering the pores of the active material layer during wet coating, forming a wrap around the active material, resulting in electronic insulation between the active materials, and affecting the electrical performance of the battery. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specific implementation methods are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention and the above description and any variations thereof are intended to cover non-exclusive inclusions.

[0021] In the description of the specific implementation methods of the present invention, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0022] Reference to "embodiments" in the present invention means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present invention may be combined with other embodiments.

[0023] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects before and after are in an "or" relationship.

[0024] Throughout the present invention, numerical values ​​represent approximate measures or limits of ranges to cover minor deviations from given values ​​as well as embodiments with about the values ​​mentioned and embodiments with the exact values ​​mentioned. Except for the working examples provided at the end of the detailed description, all numerical values ​​of parameters (e.g., amounts or conditions) in this specification (including the appended claims) should be understood to be modified by the term "about" in all cases, regardless of whether "about" actually appears before the numerical value. "About" indicates that the stated numerical value allows some minor imprecision (close to the exact value of the value to some extent; approximately or reasonably close to the value; almost). If the imprecision provided by "about" is not otherwise understood in this ordinary sense in the art, "about" as used in the present invention at least indicates the variation that can be produced by the ordinary methods of measuring and using such parameters. For example, "about" may include a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some aspects, optionally less than or equal to 0.1%.

[0025] Additionally, disclosure of ranges includes disclosure of all values ​​within the entire range and further divided ranges, including endpoints and sub-ranges given for such ranges.

[0026] When traditional lithium-ion batteries are working, the internal resistance of the lithium-ion batteries will affect the cycle performance of the lithium-ion batteries, which in turn affects the fast charging and high-rate discharge performance of the batteries.

[0027] In order to solve the above problems, the present invention proposes a technical solution, by setting a functional layer between the active material layer of the electrode plate and the diaphragm, the combined effect of the inorganic solid electrolyte, polymer solid electrolyte and conductive agent therein can reduce the internal resistance of the battery, improve the lithium ion cycle performance, and thereby improve the fast charging and high-rate discharge performance of the battery.

[0028] The first aspect of the present invention discloses a battery cell unit, comprising an electrode plate and a separator, wherein the electrode plate comprises a current collector and an active material layer at least arranged on one side of the current collector, and the electrode plate further comprises a functional layer;

[0029] One side of the functional layer is bonded to the active material layer, and the other side of the functional layer is bonded to the separator;

[0030] The functional layer includes an inorganic solid electrolyte, a polymer and a conductive agent.

[0031] One side of the functional layer is bonded to the active material layer, and the other side is bonded to the diaphragm. The inorganic solid electrolyte and polymer solid electrolyte in the functional layer can improve the electrochemical working window and interface stability between the active material layer and the diaphragm. At the same time, the combined action of the inorganic solid electrolyte, polymer solid electrolyte and conductive agent in the functional layer can reduce the internal resistance of the battery, improve the lithium ion cycle performance, and thereby improve the fast charging and high-rate discharge performance of the battery.

[0032] In specific applications, the conductive agent is selected from one or more of carbon black, carbon nanotubes, carbon fibers, graphene, and metal particles; single-walled carbon nanotubes are preferred, which can be packaged separately or in a dispersed slurry. The use of single-walled carbon nanotubes is easier to help build a conductive network and has a lower cost. The above is only an example and is not a limitation.

[0033] In some embodiments, the polymer is a polymer solid electrolyte.

[0034] The polymer used in this application is a polymer solid electrolyte, which is different from a gel polymer and reduces the possibility of its penetration into the pores of the active material layer, and reduces the possibility of its coating on the active material and thus causing electronic insulation between the active materials. The polymer solid electrolyte can be used as both an electrolyte and a binder, without the need to add additional binders, and can further improve the cycle performance of the battery.

[0035] In specific applications, the polymer solid electrolyte includes at least one of polyacrylic acid, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, and poly(ethylene methyl carbonate).

[0036] As used in the present invention, "at least one" means, in addition to single selection, combinations of two or more are also included.

[0037] In some embodiments, the inorganic solid electrolyte includes at least one of sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes.

[0038] Using an inorganic solid electrolyte compensates for the problem of poor ionic conductivity of the polymer solid electrolyte itself. Compared with the case of simply using a polymer solid electrolyte, it can better improve the cycling performance of the battery. At the same time, the inorganic solid electrolyte has high strength and good thermal stability, which can further improve the mechanical strength and thermal stability of the battery, thereby enhancing the safety performance of the battery.

[0039] In specific applications, the halide solid electrolyte can be selected from: Li 2 CdC l4 、Li 2 MgC l4 、Li 2 Cd I4 、Li 2 ZnI 4 、Li 3 OCl、LiI、Li 5 ZnI 4 、Li 3 OCl 1-x Br x (where 0 < x < 1) and their combinations.

[0040] In specific applications, the sulfide solid electrolyte can be selected from: Li 2 S-P 2 S 5 、Li 2 S-P 2 S 5 -MS x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 3.4 Si 0.4 P 0.6 S 4 、Li 10 GeP 2 S 11.7 O 0.3 、Li 9.6 P 3 S 12 、Li 7 P3 S 11 , Li 9 P 3 S 9 O 3 , Li 10.35 Si 1.35 P 1.65 S 12 , Li 9.81 Sn 0.81 P 2.19 S 12 , Li 10 (Si 0.5 Ge 0.5 ) 2 S 12 、Li(Ge 0.5 Sn 0.5 ) 2 S 12 、Li(Si 0.5 Sn 0.5 )PsS 12 , Li 10 G 2 S 12 (LGPS), Li 6 PS 5 X (wherein X is Cl, Br or I), Li 7 P 2 S 8 I. Li 10.35 Ge 1.35 P 1.65 S 12 , Li 3.25 Ge 0.25 P 0.75 S 4 , Li 10 SnP 2 S 12 , Li 10 SiP 2 S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 , (1-x) P 2 S 5-x Li 2 S (where 0.5≤x≤0.7) and their combinations.

[0041] In specific applications, oxide solid electrolytes include: perovskite type, garnet type, LISICON type, NASICON type. Among them, the perovskite type solid electrolyte material is preferably LLTO (Li0.33 La 0.56 TiO 3 , lithium lanthanum titanate / lithium lanthanum titanate), the garnet-type solid electrolyte material is preferably LLZO (lithium lanthanum zirconium oxide / lithium lanthanum zirconate, Li 7 La 3 Zr 2 O 12 ); NASICON (sodium super ion conductor) type solid electrolyte material is preferably lithium aluminum titanium phosphate LATP (Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 ).

[0042] In some embodiments, the mass ratio of the inorganic solid electrolyte, the polymer solid electrolyte and the conductive agent is (5%-99%): (1%-94%): (0.01%-10%).

[0043] In some preferred embodiments, the mass ratio of the polymer solid electrolyte in the functional layer is 50%-90%.

[0044] The mass ratio of polymer solid electrolyte within this range can improve the adhesion between inorganic solid electrolyte and conductive agent, help better construct a conductive network, and improve the cycle performance of the battery.

[0045] In some embodiments, the functional layer is compounded on the active material layer by dry transfer. Dry transfer can prevent the inorganic solid electrolyte and polymer solid electrolyte in the functional layer from entering the pores of the active material layer during the wet coating process, wrapping the active material, resulting in electronic insulation between the active materials, and affecting the electrical performance of the battery.

[0046] In some embodiments, the thickness of the functional layer is 0.5 μm to 10 μm.

[0047] In specific applications, the thickness of each functional layer can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm. The above values ​​are only examples and are not limiting.

[0048] When the thickness of the functional layer is within this range, the battery can have low impedance, good cycle stability and good rate performance.

[0049] In some embodiments, the electrode plate is a positive electrode plate, the current collector is a positive electrode current collector, and the active material layer includes a positive electrode active material, a conductive agent, and a binder.

[0050] In some embodiments, the electrode plate is a negative electrode, the current collector is a negative electrode current collector, and the active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0051] In the present application, the current collector can be a conventional single-layer foil, or a composite current collector can be used, including aluminum foil, carbon-coated aluminum foil, composite aluminum foil; copper foil, carbon-coated copper foil, composite copper foil, etc., which are only examples and not limitations.

[0052] In specific applications, when the active material is a positive electrode active material, any one or a combination of at least two of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium iron phosphate, lithium titanate or lithium-rich manganese-based materials can be selected. The above are all common positive electrode active materials in the field, which are only examples and not limitations.

[0053] In specific applications, when the active material is a negative electrode active material, it can be selected from any one or a combination of at least two of artificial graphite, natural graphite, microcrystalline graphite, soft carbon and hard carbon. The above are common negative electrode active materials in the art, which are only examples and not limitations.

[0054] In specific applications, the binder includes any one or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, polyvinyl chloride, polystyrene, polyoxymethylene, polycarbonate, polyamide, acrylic plastics, other polyolefins and copolymers thereof, polysulfone, polyphenylene ether or carboxymethyl cellulose, preferably polytetrafluoroethylene or polyvinyl chloride. The above are all common binders in the art, which are only examples and not limitations.

[0055] The second aspect of the present invention discloses a lithium-ion battery, which includes the battery cell unit.

[0056] The embodiments of the present invention will be described in more detail below through examples and comparative examples. It should be noted that the embodiments of the present invention are not limited to these examples.

[0057] Example 1

[0058] 1. Preparation of positive electrode sheet with functional layer (dry transfer):

[0059] 1. The positive electrode active material lithium iron phosphate, the conductive agent superconducting carbon (Super-P), and the binder polyvinylidene fluoride (PVDF) are mixed evenly at a mass ratio of 97:1.5:1.5 to form a positive electrode slurry, and the positive electrode slurry is coated on both surfaces of the current collector aluminum foil, dried at 100°C to form a positive electrode active material layer, and then rolled to obtain a positive electrode sheet containing an active material layer;

[0060] 2. The LLZO inorganic solid electrolyte, the PVDF polymer solid electrolyte and the CNT conductive agent are mixed uniformly in a mass ratio of 45:50:5 to prepare a functional layer slurry, the functional layer slurry is coated on a PET substrate, and a PET substrate containing a functional layer is prepared after drying, wherein the coating speed is 10 m / min;

[0061] 3. The PET substrate containing the functional layer prepared in step 2 passes through the first unwinding shaft and enters between the first hot pressing roller and the second hot pressing roller together with the positive electrode sheet containing the active material layer to be processed from the second unwinding shaft for compounding. The compounded positive electrode sheet is rolled up by the first winding shaft. At this time, a functional layer is formed on the active material layer of the positive electrode sheet, and the PET substrate is recovered from the second winding shaft, wherein the hot pressing temperature is 90°C.

[0062] 4. The positive electrode sheet containing the functional layer obtained in step 3 is trimmed, cut into pieces, and divided into strips, and after being divided into strips, it is used as a positive electrode sheet for a lithium-ion battery.

[0063] 2. Preparation of negative electrode sheet:

[0064] 1. The negative electrode active material graphite, the conductive agent superconducting carbon (Super-P), the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) are prepared into a negative electrode slurry at a mass ratio of 96.5:1.0:1.0:1.5, coated on the current collector copper foil and dried at 90°C to form a negative electrode active material layer, and then rolled to obtain a negative electrode sheet;

[0065] 2. The product prepared in step 1 is trimmed, cut into pieces, and stripped to produce negative electrode sheets for lithium-ion batteries.

[0066] 3. Preparation of electrolyte

[0067] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0068] 4. Preparation of batteries

[0069] The positive electrode sheet and negative electrode sheet prepared above are stacked in order with the separator so that the separator is between the positive and negative electrode sheets, and then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, and after drying, an electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0070] Example 2

[0071] 1. Preparation of negative electrode sheet containing functional layer (dry transfer):

[0072] 1. The negative electrode active material graphite, the conductive agent superconducting carbon (Super-P), the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) are prepared into a negative electrode slurry at a mass ratio of 96.5:1.0:1.0:1.5, coated on the current collector copper foil and dried at 90°C to form a negative electrode active material layer, and then rolled to obtain a negative electrode sheet;

[0073] 2. The LLZO inorganic solid electrolyte, the PVDF polymer solid electrolyte and the CNT conductive agent are mixed uniformly in a mass ratio of 45:50:5 to prepare a functional layer slurry, the functional layer slurry is coated on a PET substrate, and a PET substrate containing a functional layer is prepared after drying, wherein the coating speed is 10 m / min;

[0074] 3. The PET substrate containing the functional layer prepared in step 2 passes through the first unwinding shaft and enters between the first hot pressing roller and the second hot pressing roller together with the negative electrode sheet containing the active material layer to be processed from the second unwinding shaft for compounding. The compounded negative electrode sheet is rolled up by the first winding shaft. At this time, a functional layer is formed on the active material layer of the negative electrode sheet, and the PET substrate is recovered from the second winding shaft, wherein the hot pressing temperature is 90°C.

[0075] 4. The negative electrode sheet containing the functional layer obtained in step 3 is trimmed, cut into pieces, and stripped. After stripping, it is used as the negative electrode sheet of the lithium-ion battery.

[0076] 2. Preparation of positive electrode sheet:

[0077] 1. The positive electrode active material lithium iron phosphate, the conductive agent superconducting carbon (Super-P), and the binder polyvinylidene fluoride (PVDF) are mixed evenly at a mass ratio of 97:1.5:1.5 to form a positive electrode slurry, and the positive electrode slurry is coated on both surfaces of the current collector aluminum foil, dried at 100°C to form a positive electrode active material layer, and then cold pressed to obtain a positive electrode sheet containing an active material layer;

[0078] 2. The product prepared in step 1 is trimmed, cut into pieces, and stripped to produce negative electrode sheets for lithium-ion batteries.

[0079] 3. Preparation of electrolyte

[0080] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0081] 4. Preparation of batteries

[0082] The positive electrode sheet and negative electrode sheet prepared above are stacked in order with the separator so that the separator is between the positive and negative electrode sheets, and then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, and after drying, an electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0083] Comparative Example 1

[0084] Preparation of positive electrode:

[0085] 1. The positive electrode active material lithium iron phosphate, the conductive agent superconducting carbon (Super-P), and the binder polyvinylidene fluoride (PVDF) are mixed evenly at a mass ratio of 97:1.5:1.5 to form a positive electrode slurry, and the positive electrode slurry is coated on both surfaces of the current collector aluminum foil, dried at 100°C to form a positive electrode active material layer, and then cold pressed to obtain a positive electrode sheet containing an active material layer;

[0086] 2. The positive electrode sheet containing the active material layer obtained in step 1 is trimmed, cut into pieces, and divided into strips, and after being divided into strips, it is used as a positive electrode sheet for a lithium-ion battery.

[0087] Preparation of negative electrode sheet:

[0088] 1. The negative electrode active material graphite, the conductive agent superconducting carbon (Super-P), the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) are prepared into a negative electrode slurry at a mass ratio of 96.5:1.0:1.0:1.5, coated on the current collector copper foil and dried at 90°C to form a negative electrode active material layer, and then cold pressed to obtain a negative electrode sheet;

[0089] 2. The product prepared in step 1 is trimmed, cut into pieces, and stripped to produce negative electrode sheets for lithium-ion batteries.

[0090] 3. Preparation of electrolyte

[0091] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0092] 4. Preparation of batteries

[0093] The positive electrode sheet and negative electrode sheet prepared above are stacked in order with the separator so that the separator is between the positive and negative electrode sheets, and then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, and after drying, an electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0094] Comparative Example 2

[0095] 1. Preparation of positive electrode sheet with functional layer (wet coating):

[0096] 1. The positive electrode active material lithium iron phosphate, the conductive agent superconducting carbon (Super-P), and the binder polyvinylidene fluoride (PVDF) are mixed evenly at a mass ratio of 97:1.5:1.5 to form a positive electrode slurry, and the positive electrode slurry is coated on both surfaces of the current collector aluminum foil, dried at 100°C to form a positive electrode active material layer, and then cold pressed to obtain a positive electrode sheet containing an active material layer;

[0097] 2. Dissolve LLZO inorganic solid electrolyte, PVDF polymer solid electrolyte and CNT conductive agent in an organic solvent N, N-dimethylacetamide (DMAC) at a mass ratio of 45:50:5, mix evenly to form a functional layer slurry, apply the functional layer slurry on the surface of the positive electrode active material layer in step 1, and dry at 60° C. to obtain a positive electrode sheet containing a functional layer with a thickness of 5 μm;

[0098] 3. The positive electrode sheet containing the functional layer obtained in step 2 is trimmed, cut into pieces, and divided into strips, and after being divided into strips, it is used as a positive electrode sheet for a lithium-ion battery.

[0099] 2. Preparation of negative electrode sheet:

[0100] 1. The negative electrode active material graphite, the conductive agent superconducting carbon (Super-P), the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) are prepared into a negative electrode slurry at a mass ratio of 96.5:1.0:1.0:1.5, coated on the current collector copper foil and dried at 90°C to form a negative electrode active material layer, and then cold pressed to obtain a negative electrode sheet;

[0101] 2. The product prepared in step 1 is trimmed, cut into pieces, and stripped to produce negative electrode sheets for lithium-ion batteries.

[0102] 3. Preparation of electrolyte

[0103] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0104] 4. Preparation of batteries

[0105] The positive electrode sheet and negative electrode sheet prepared above are stacked in order with the separator so that the separator is between the positive and negative electrode sheets, and then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, and after drying, an electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0106] Comparative Example 3

[0107] 1. Preparation of negative electrode sheet with functional layer (wet coating):

[0108] 1. The negative electrode active material graphite, the conductive agent superconducting carbon (Super-P), the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) are prepared into a negative electrode slurry at a mass ratio of 96.5:1.0:1.0:1.5, coated on the current collector copper foil and dried at 90°C to form a negative electrode active material layer, and then cold pressed to obtain a negative electrode sheet;

[0109] 2. Dissolve LLZO inorganic solid electrolyte, PVDF polymer solid electrolyte and CNT conductive agent in an organic solvent N, N-dimethylacetamide (DMAC) at a mass ratio of 45:50:5, mix them evenly to form a functional layer slurry, apply the functional layer slurry on the surface of the negative electrode active material layer in step 1, and dry them at 60° C. to obtain a negative electrode sheet containing a functional layer with a thickness of 5 μm;

[0110] 3. The negative electrode sheet containing the functional layer obtained in step 2 is trimmed, cut into pieces, and stripped, and after stripping, used as the negative electrode sheet of the lithium-ion battery.

[0111] 2. Preparation of positive electrode sheet:

[0112] 1. The positive electrode active material lithium iron phosphate, the conductive agent superconducting carbon (Super-P), and the binder polyvinylidene fluoride (PVDF) are mixed evenly at a mass ratio of 97:1.5:1.5 to form a positive electrode slurry, and the positive electrode slurry is coated on both surfaces of the current collector aluminum foil, dried at 100°C to form a positive electrode active material layer, and then cold pressed to obtain a positive electrode sheet containing an active material layer;

[0113] 2. The product prepared in step 1 is trimmed, cut into pieces, and stripped to make positive electrode sheets for lithium-ion batteries.

[0114] 3. Preparation of electrolyte

[0115] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0116] 4. Preparation of batteries

[0117] The positive electrode sheet and negative electrode sheet prepared above are stacked in order with the separator so that the separator is between the positive and negative electrode sheets, and then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, and after drying, an electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0118] In order to further demonstrate the technical effect of the present invention, five groups of samples from Examples 1-2 and Comparative Examples 1-3 were used for comparative experiments, with 20 samples in each group, and the experimental results were averaged. The test method is as follows:

[0119] 1. Internal resistance test: obtained through DCR test, 25℃, 3C discharge for 10 seconds.

[0120] 2. Fast charging test:

[0121] ① At room temperature: discharge at 1C current to the discharge end voltage (2.5V), and let stand for 1h;

[0122] ② Then charge it in the standard charging mode, discharge it at 1C current to the discharge end voltage (2.5V), and let it stand for 1 hour;

[0123] ③ Charge at 2C constant current to the charge end voltage; then discharge at 1C to the discharge end voltage (2.5V);

[0124] Charge at 2C constant current and constant voltage to the charge end voltage, then discharge at 1C to the discharge end voltage (2.5V), repeat 10 times, no lithium deposition after fully charged dissection

[0125] standard:

[0126] 3. High rate discharge performance test:

[0127] ① At room temperature: charge with standard charging method, let stand for 0.5h, and discharge at 1C and 3C respectively to the end voltage (2.5V);

[0128] ②Standards:

[0129] 4. Cycle performance test: 1C constant current and constant voltage charge to the upper voltage limit, stand for 1 hour, 1C constant current discharge to the lower voltage limit, stand for 1 hour, cycle 500 times, and calculate the discharge capacity retention rate;

[0130] The test results are shown in the following table:

[0131] sheet:

[0132]

[0133] According to the above table, it can be seen from Examples 1-2 and Comparative Example 1 that setting a functional layer can reduce the internal resistance of a lithium battery, improve the fast charge and high-rate discharge performance of the battery, and improve the lithium ion cycle performance. It can be seen from Examples 1-2 and Comparative Examples 2-3 that using dry transfer to set a functional layer can further improve the battery cycle performance compared to wet coating.

[0134] It should be pointed out that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery cell unit, comprising an electrode plate and a separator, wherein the electrode plate comprises a current collector and an active material layer disposed at least on one side of the current collector, characterized in that: The electrode plate further comprises a functional layer; One side of the functional layer is bonded to the active material layer, and the other side of the functional layer is bonded to the separator; The functional layer includes an inorganic solid electrolyte, a polymer and a conductive agent.

2. A battery cell unit according to claim 1, characterized in that: The polymer is a polymer solid electrolyte.

3. A battery cell unit according to claim 2, characterized in that: The inorganic solid electrolyte includes at least one of a sulfide solid electrolyte, an oxide solid electrolyte and a halide solid electrolyte.

4. A battery cell unit according to claim 2, characterized in that: The mass ratio of the inorganic solid electrolyte, the polymer solid electrolyte and the conductive agent is (5%-99%): (1%-94%): (0.01%-10%).

5. A battery cell unit according to claim 4, characterized in that: The mass ratio of the polymer solid electrolyte in the functional layer is 50%-90%.

6. A battery cell unit according to claim 1, characterized in that: The functional layer is compounded on the active material layer by dry transfer.

7. A battery cell unit according to claim 1, characterized in that: The thickness of the functional layer is 0.5 μm to 10 μm.

8. A battery cell unit according to claim 1, characterized in that: The electrode plate is a positive electrode plate, the current collector is a positive electrode current collector, and the active material layer includes a positive electrode active material, a conductive agent and a binder.

9. A battery cell unit according to claim 1, characterized in that: The electrode plate is a negative electrode plate, the current collector is a negative electrode current collector, and the active material layer includes a negative electrode active material, a conductive agent, and a binder.

10. A lithium-ion battery comprising the battery cell unit according to any one of claims 1 to 9.

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