Lithium-free negative electrode sheet and preparation method thereof, secondary battery, battery module, battery pack and power-consuming device

Abstract

The present application provides a lithium-free negative electrode plate, comprising a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is disposed on the surface of the negative electrode current collector; the negative electrode active material layer comprises a transition metal salt. After chemical formation, a solid electrolyte interface film rich in transition metal ions can be formed on the surface of the lithium-free negative electrode plate, thereby inhibiting the dissolution of transition metals in the electrolyte and the positive electrode active material, avoiding deterioration of the negative electrode plate, and being used to prepare a secondary battery with a longer cycle life.

Description

Technical Field

[0001] The present application relates to the field of secondary batteries, and specifically to a lithium-free negative electrode plate and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electrical device. Background Art

[0002] Lithium-ion batteries have attracted much attention due to their advantages such as high specific energy, long cycle life, low self-discharge, and good safety. However, during the use of lithium-ion batteries, as the positive electrode active material deteriorates, the transition metal elements contained in the positive electrode active material gradually dissolve and migrate to the interface of the negative electrode plate, causing the negative electrode plate to deteriorate and affecting the cycle life of the battery. Summary of the invention

[0003] Based on the above problems, the present application provides a lithium-free negative electrode plate and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electrical device, so as to improve the cycle life of a traditional secondary battery.

[0004] In one aspect of the present application, a lithium-free negative electrode plate is provided, comprising:

[0005] Anode current collector; and

[0006] A negative electrode active material layer is disposed on the surface of the negative electrode current collector; the negative electrode active material layer comprises a transition metal salt.

[0007] In the lithium-free negative electrode plate of the present application, the negative electrode active material layer contains a transition metal salt. After the secondary battery is formed, a solid electrolyte interface (SEI) film rich in transition metal ions can be formed on the surface of the lithium-free negative electrode plate. The inventors have found that the SEI film rich in transition metal ions can inhibit the dissolution of transition metals in the positive electrode active material, avoid deterioration of the negative electrode plate, and be used to prepare a secondary battery with a longer cycle life.

[0008] In some embodiments, in the transition metal salt, the transition metal element includes at least one of Co, Ni, Mn, Fe, Cu, Zn, Cr, V and Ti.

[0009] In some embodiments, in the negative electrode active material layer, the content of the transition metal element is 10ppm to 850ppm;

[0010] Optionally, in the negative electrode active material layer, the content of the transition metal element is 20ppm to 800ppm;

[0011] Optionally, in the negative electrode active material layer, the content of the transition metal element is 20ppm to 500ppm;

[0012] Optionally, in the negative electrode active material layer, the content of the transition metal element is 20 ppm to 200 ppm.

[0013] Too high or too low a content of transition metal elements is not conducive to improving the cycle life of the secondary battery. When the content of transition metal elements in the negative electrode active material layer is adjusted within the above range, the secondary battery has a better cycle life.

[0014] In some embodiments, the transition metal salt includes at least one of nitrate, oxalate, sulfonate, acetate and carbonate;

[0015] Optionally, the transition metal salt is selected from at least one of nitrates, oxalates, sulfonates and acetates.

[0016] In some embodiments, the distribution depth of the transition metal salt is 10 nm to 100 nm in the direction from the surface of the negative electrode active material layer away from the negative electrode current collector to the negative electrode current collector;

[0017] Optionally, the distribution depth of the transition metal salt is 30 nm to 80 nm.

[0018] The transition metal salt is mainly distributed on the surface of the negative electrode active material layer away from the negative electrode current collector, which is conducive to the formation of a SEI film rich in transition metal ions on the surface of the lithium-free negative electrode plate.

[0019] In some embodiments, the negative electrode active material in the negative electrode active material layer includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase microcarbon beads, silicon-based materials and tin-based materials.

[0020] In a second aspect, the present application also provides a method for preparing a lithium-free negative electrode sheet, comprising the following steps:

[0021] Preparing a negative electrode active material layer on at least one surface of a negative electrode current collector to prepare a lithium-free electrode sheet;

[0022] The lithium-free electrode sheet is immersed in a solution containing a transition metal salt, so that the transition metal salt penetrates into the negative electrode active material layer.

[0023] The above-mentioned preparation method allows the active material layer of the lithium-free negative electrode plate to contain transition metal salts through immersion. The preparation method is simple and easy to implement. After the prepared lithium-free negative electrode plate is subjected to chemical treatment, a SEI film rich in transition metal ions can be formed on the surface, which is beneficial to improving the cycle life of the secondary battery.

[0024] In some embodiments, in the transition metal salt, the transition metal element includes at least one of Co, Ni, Mn, Fe, Cu, Zn, Cr, V and Ti.

[0025] In some embodiments, in the negative electrode active material layer, the content of the transition metal element is 10ppm to 850ppm;

[0026] Optionally, in the negative electrode active material layer, the content of the transition metal element is 20ppm to 800ppm;

[0027] Optionally, in the negative electrode active material layer, the content of the transition metal element is 20ppm to 500ppm;

[0028] Optionally, in the negative electrode active material layer, the content of the transition metal element is 20 ppm to 200 ppm.

[0029] Too high or too low a content of transition metal elements is not conducive to improving the cycle life of the secondary battery. When the content of transition metal elements in the negative electrode active material layer is adjusted within the above range, the secondary battery has a better cycle life.

[0030] In some embodiments, the transition metal salt includes at least one of nitrate, oxalate, sulfonate, acetate and carbonate;

[0031] Optionally, the transition metal salt is selected from at least one of nitrates, oxalates, sulfonates and acetates.

[0032] In some embodiments, the distribution depth of the transition metal salt is 10 nm to 100 nm in the direction from the surface of the negative electrode active material layer away from the negative electrode current collector to the negative electrode current collector;

[0033] Optionally, the distribution depth of the transition metal salt is 30 nm to 80 nm.

[0034] The transition metal salt is mainly distributed on the surface of the negative electrode active material layer away from the negative electrode current collector, which is conducive to the formation of a SEI film rich in transition metal ions on the surface of the lithium-free negative electrode plate.

[0035] In some embodiments, the negative electrode active material in the negative electrode active material layer includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase microcarbon beads, silicon-based materials and tin-based materials.

[0036] In some embodiments, the solvent of the solution is selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl acetate and tetrahydrofuran;

[0037] Optionally, the solvent of the solution is dimethyl carbonate.

[0038] In some embodiments, the mass percentage of the transition metal salt in the solution is 1% to 30%;

[0039] Optionally, the mass percentage of the transition metal salt in the solution is 5% to 10%.

[0040] In some embodiments, the soaking time is 15 min to 180 min.

[0041] In a third aspect, the present application further provides a secondary battery, comprising the above-mentioned lithium-free negative electrode plate or a lithium-free negative electrode plate prepared according to the above-mentioned method for preparing the lithium-free negative electrode plate.

[0042] In some embodiments, the secondary battery further comprises a positive electrode active material; the positive electrode active material contains a transition metal element.

[0043] In some embodiments, the positive electrode active material is selected from Li[Ni x Co y N z M 1-x-y-z ]At least one of O2, LiMn2O4, Li2MnO3·(1-a)LiAO2 and LiFePO4;

[0044] Wherein, N is selected from one of Mn and Al; M is selected from one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti; 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1;

[0045] A is selected from one of Ni, Co and Mn; 0<a<1.

[0046] In some of the embodiments, the transition metal element of the lithium-free negative electrode plate is the same as the transition metal element in the positive electrode active material.

[0047] In some embodiments, the secondary battery further comprises an electrolyte; the electrolyte comprises an additive;

[0048] Optionally, the additive is selected from at least one of vinylene carbonate, vinyl sulfate, lithium bis(oxalatoborate), lithium oxalatodifluoroborate, fluoroethylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate and 1,3-propane sultone.

[0049] In some embodiments, in the electrolyte, the mass percentage of the additive is 0.1% to 5%;

[0050] Optionally, in the electrolyte, the mass percentage of the additive is 0.5% to 2%.

[0051] In a fourth aspect, the present application also provides a battery module, comprising the above-mentioned secondary battery.

[0052] In a fifth aspect, the present application also provides a battery pack, comprising the above-mentioned battery module.

[0053] In a sixth aspect, the present application also provides an electrical device, comprising at least one selected from the above-mentioned secondary battery, the above-mentioned battery module and the above-mentioned battery pack.

[0054] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the optional embodiments below. The accompanying drawings are only used for the purpose of illustrating the optional embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0056] Figure 1 A schematic diagram of a secondary battery according to an embodiment of the present application;

[0057] Figure 2 for Figure 1 An exploded view of a secondary battery according to an embodiment of the present application is shown;

[0058] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0059] Figure 4 A schematic diagram of a battery pack according to an embodiment of the present application;

[0060] Figure 5 for Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0061] Figure 6 A schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source;

[0062] Description of reference numerals:

[0063] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 cover plate; 6 electrical device. DETAILED DESCRIPTION

[0064] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0066] The positive electrode active materials in traditional lithium-ion batteries mostly use ternary materials containing transition metal elements, lithium iron phosphate and lithium iron manganese phosphate. During the use of lithium-ion batteries, as the positive electrode active materials deteriorate, the transition metal ions of the positive electrode active materials are usually dissolved. The inventors of the present application have found that the dissolved transition metal ions are easily deposited on the surface of the negative electrode plate and destroy the SEI film on the surface of the negative electrode plate, thereby causing a large loss of active lithium in the lithium-ion battery and affecting the cycle life of the battery.

[0067] The present application provides a lithium-free negative electrode plate and a preparation method thereof, and a secondary battery, a battery module, a battery pack and an electric device using the lithium-free negative electrode plate. The secondary battery has a long cycle life and is suitable for various electric devices using batteries, such as mobile phones, portable devices, laptop computers, electric vehicles, electric toys, electric tools, electric vehicles, ships and spacecraft, etc. For example, spacecraft include airplanes, rockets, space shuttles and spacecrafts.

[0068] In one embodiment of the present application, a lithium-free negative electrode sheet is provided, comprising a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is disposed on the surface of the negative electrode current collector; the negative electrode active material layer comprises a transition metal salt. As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0069] It can be understood that the lithium-free negative electrode plate provided in the embodiment of the present application does not contain a metallic lithium layer.

[0070] In the lithium-free negative electrode plate of the present application, the negative electrode active material layer contains a transition metal salt. After the secondary battery is formed, a solid electrolyte interface (SEI) film rich in transition metal ions can be formed on the surface of the lithium-free negative electrode plate. The inventors have found that the SEI film rich in transition metal ions can inhibit the dissolution of transition metals in the positive electrode active material, avoid deterioration of the negative electrode plate, and be used to prepare a secondary battery with a longer cycle life.

[0071] Specifically, regarding the content of transition metal elements in the lithium-free negative electrode sheet, the lithium-free negative electrode sheet can be disassembled, one part is subjected to ICP testing to obtain a transition metal ion content of X1ppm, and the other part is immersed in a solution containing transition metal ions for 3 hours, the surface is cleaned with DMC, and an ICP test is performed to obtain a transition metal ion content of X2. If the test X1 is close to X2, it means that the lithium-free negative electrode sheet contains transition metal elements. If X2 / X1≥5, it means that the lithium-free negative electrode sheet does not contain transition metal elements.

[0072] In addition, the lithium-free negative electrode plate can also be tested using a scanning electron microscope-energy dispersive spectrometer (SEM-EDS) in accordance with the GB / T 17359-2012 "Microbeam Analysis Energy Spectrometry Quantitative Analysis" standard to observe the element distribution on the surface of the lithium-free negative electrode plate.

[0073] In some embodiments, in the transition metal salt, the transition metal element includes at least one of Co, Ni, Mn, Fe, Cu, Zn, Cr, V and Ti.

[0074] In some of the embodiments, in the negative electrode active material layer, the content of transition metal elements is 10ppm to 850ppm. If the content of transition metal elements is too low, the content of SEI film on the surface of the lithium-free negative electrode plate is low, and the effect of inhibiting the deposition of transition metal ions on its surface is not obvious; while if the content of transition metal elements is too high, it will affect the cycle life of the secondary battery. Optionally, in the negative electrode active material layer, the content of transition metal elements can be a range consisting of any two of the following numerical combinations: 10ppm, 20ppm, 50ppm, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm or 850ppm. Further, in the negative electrode active material layer, the content of transition metal elements is 20ppm to 500ppm or 20ppm to 200ppm.

[0075] In some embodiments, the transition metal salt includes at least one of nitrate, oxalate, sulfonate, acetate and carbonate. Further, the transition metal salt is selected from at least one of nitrate, oxalate, sulfonate and acetate. Transition metal salts such as nitrate, oxalate, sulfonate and acetate have little effect on the electrochemical performance of the lithium-free negative electrode sheet.

[0076] In the lithium-free negative electrode sheet, the transition metal salt is mainly distributed on the surface of the negative electrode active material layer away from the negative electrode current collector, so as to form a SEI film rich in transition metal ions on the surface of the lithium-free negative electrode sheet. In some embodiments, the distribution depth of the transition metal salt is 10nm to 100nm from the surface of the negative electrode active material layer away from the negative electrode current collector to the negative electrode current collector. Optionally, the distribution depth of the transition metal salt can be a range consisting of any two of the following numerical combinations: 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm. Further, the distribution depth of the transition metal salt is 30nm to 80nm.

[0077] In some of the embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy on a polymer material substrate. The polymer material substrate includes substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0078] In some embodiments, the negative electrode active material in the negative electrode active material layer includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase micro carbon beads, silicon-based materials and tin-based materials.

[0079] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0080] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0081] In some of the embodiments, the negative electrode active material layer may further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0082] Another embodiment of the present application further provides a method for preparing a lithium-free negative electrode sheet, comprising the following steps:

[0083] Preparing a negative electrode active material layer on at least one surface of a negative electrode current collector to prepare a lithium-free electrode sheet;

[0084] The lithium-free electrode sheet is immersed in a solution containing a transition metal salt, so that the transition metal salt penetrates into the negative electrode active material layer.

[0085] The above-mentioned preparation method allows the active material layer of the lithium-free negative electrode plate to contain transition metal salts through immersion. The preparation method is simple and easy to implement. After the prepared lithium-free negative electrode plate is subjected to chemical treatment, a SEI film rich in transition metal ions can be formed on the surface, which is beneficial to improving the cycle life of the secondary battery.

[0086] It can be understood that the above-mentioned lithium-free electrode sheet is a traditional negative electrode sheet. In some embodiments, the above-mentioned lithium-free electrode sheet can be prepared by the following method: the above-mentioned components for preparing the lithium-free negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the lithium-free electrode sheet can be obtained.

[0087] In some embodiments, the solvent of the solution is selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl acetate and tetrahydrofuran. Further, the solvent of the transition metal salt solution is dimethyl carbonate. The transition metal salt solution prepared with a volatile solvent such as dimethyl carbonate can facilitate subsequent drying to remove the solvent.

[0088] In some embodiments, the mass percentage of the transition metal salt in the solution is 1% to 30%. Optionally, the mass percentage of the transition metal salt in the solution can be a range consisting of any two of the following numerical values: 1%, 2%, 4%, 5%, 6%, 8%, 10%, 15%, 20%, 25% or 30%. Further, the mass percentage of the transition metal salt in the solution is 5% to 10%.

[0089] The content of the transition metal salt in the negative electrode active material layer can be controlled by controlling the soaking time. In some embodiments, the soaking time is 15 min to 180 min.

[0090] In addition, the secondary battery, battery module, battery pack, and electric device of the present application will be described below with reference to the drawings as appropriate.

[0091] In one embodiment of the present application, a secondary battery is provided.

[0092] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0093] Negative electrode

[0094] The negative electrode plate adopts the lithium-free negative electrode plate provided in the first aspect of the present application or the lithium-free negative electrode plate prepared according to the preparation method of the second aspect.

[0095] Positive electrode

[0096] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0097] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

[0098] In some of the embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy on a polymer material substrate. The polymer material substrate includes substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0099] In some of the embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art.

[0100] In some embodiments, the secondary battery further comprises a positive electrode active material; the positive electrode active material contains a transition metal element. In some embodiments, the positive electrode active material is selected from Li[Ni x Co y N z M 1-x-y-z ]At least one of O2, LiMn2O4, Li2MnO3·(1-a)LiAO2 and LiFePO4;

[0101] Wherein, N is selected from one of Mn and Al; M is selected from one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti; 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1;

[0102] A is selected from one of Ni, Co and Mn; 0<a<1.

[0103] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0104] In some embodiments, the transition metal element in the positive electrode active material is the same as the transition metal element in the lithium-free negative electrode plate. When the transition metal element in the positive electrode active material is the same as the transition metal element in the lithium-free negative electrode plate, the cycle life of the secondary battery is improved more significantly.

[0105] In some embodiments, the positive electrode active material layer may further include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0106] In some embodiments, the positive electrode active material layer may further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] In some of the embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0108] Electrolytes

[0109] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0110] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0111] In some of the embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate and lithium tetrafluorooxalatophosphate.

[0112] In some of the embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0113] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0114] Optionally, the additive is selected from at least one of vinylene carbonate, vinyl sulfate, lithium bis(oxalatoborate), lithium oxalatodifluoroborate, fluoroethylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate and 1,3-propane sultone.

[0115] In some embodiments, in the electrolyte, the mass percentage of the additive is 0.1% to 5%. Optionally, the mass percentage of the additive can be any range consisting of the following values: 0.1%, 0.2%, 0.5%, 0.8%, 1%, 2%, 3%, 4% or 5%. Further, the mass percentage of the additive is 0.5% to 2%.

[0116] Isolation film

[0117] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0118] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different without particular limitation.

[0119] In some of the embodiments, the positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly by a winding process or a lamination process.

[0120] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0121] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed.

[0122] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 1The secondary battery 5 is a square structure as an example.

[0123] In some of these embodiments, reference Figure 2 , the outer package may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0124] In some of the embodiments, the secondary batteries may be assembled into a battery module. The number of the secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0125] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0126] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0127] In some of the embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. The specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0128] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0129] In addition, the present application also provides an electrical device, which includes at least one of the secondary batteries, battery modules, or battery packs provided in the present application. The secondary batteries, battery modules, or battery packs can be used as power sources for electrical devices, and can also be used as energy storage units for electrical devices. Electrical devices may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited to these. Among them, mobile devices may be, for example, mobile phones, laptop computers, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0130] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0131] Figure 6 The power consumption device 6 is taken as an example. The power consumption device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or a battery module can be used.

[0132] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0133] Example

[0134] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0135] Electrolyte preparation:

[0136] In a glove box filled with argon (water content <10ppm, oxygen content <1ppm), add 2wt% vinylene carbonate (VC) to a non-aqueous organic solvent (EC:EMC=3:7W% / W%) and after mixing evenly, slowly add LiPF6 to the above solution to obtain an electrolyte containing 1mol / L LiPF6.

[0137] Positive electrode preparation:

[0138] The positive electrode active material, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) are prepared into a positive electrode slurry in N-methylpyrrolidone (NMP). 0.5 Co 0.2 Mn0.3 The mass ratio of O2, Super P and PVDF is 95:3:2. The positive electrode slurry is coated on the current collector aluminum foil and dried at 85°C and then cold pressed. Then, after trimming, cutting and striping, it is dried at 85°C under vacuum for 4 hours to make the positive electrode sheet.

[0139] Negative electrode sheet preparation:

[0140] The negative electrode active material graphite is mixed evenly with the conductive agent Super P, the thickener CMC, and the binder styrene-butadiene rubber (SBR) in deionized water to form a negative electrode slurry. The mass ratio of graphite, Super P, CMC and SBR is 94:3:0.5:2.5. The negative electrode slurry is coated on the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut, and striped, and then dried at 120°C vacuum conditions for 12 hours to form a negative electrode sheet. The cold-pressed negative electrode sheet is immersed in a transition metal nitrate solution with a mass concentration of 10% (the solvent is dimethyl carbonate) for 15 minutes to 3 hours (the content of transition metal elements on the negative electrode sheet is adjusted by controlling the immersion time), and dried.

[0141] Specifically, the content of transition metal elements on the negative electrode plate can be tested by the following method: the current collector copper foil of the same batch is pounded into several small discs with a diameter of 12 mm, weighed, and the average mass m1 of the copper foil small discs is calculated; the negative electrode plate to be tested is also pounded into several small discs with a diameter of 12 mm, weighed, and the average mass of the negative electrode small discs is calculated to be m2, m2-m1 is the mass of the negative electrode active material layer, the entire negative electrode plate is subjected to nitric acid acid hydrolysis, and an ICP-AES test is performed (instrument EPA 6010D-20143) to obtain the content of transition metal elements on the negative electrode active material layer.

[0142] Secondary battery preparation:

[0143] A 16μm polyethylene film (PE) is used as a separator. The prepared positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence to obtain a bare cell, and the tabs are welded. The bare cell is placed in an outer package, and the prepared electrolyte is injected into the dried cell. The secondary battery is then packaged, left to stand, formed, shaped, and tested for capacity.

[0144] Embodiment 1:

[0145] In the secondary battery of Example 1, the positive electrode active material is LiMn2O4, the transition metal salt used in the preparation of the negative electrode plate is manganese nitrate, and the manganese content in the negative electrode plate is 10 ppm.

[0146] Embodiment 2~8:

[0147] The difference between Examples 2 to 8 and Example 1 is that the manganese content in the negative electrode plates is different.

[0148] Embodiment 9:

[0149] In the secondary battery of Example 9, the positive electrode active material is Li[Ni 0.5 Co 0.2 Mn 0.3 ]O2, the transition metal salt used in the preparation of the negative electrode is manganese nitrate, and the manganese content in the negative electrode is 100ppm.

[0150] Embodiments 10 to 16:

[0151] The difference between Examples 10 to 16 and Example 9 is that the types of transition metal salts are different.

[0152] Embodiment 17:

[0153] In the secondary battery of Example 17, the positive electrode active material is Li[Ni 0.9 Co 0.1 Mn 0.1 ]O2, the transition metal salt used in the preparation of the negative electrode is nickel nitrate, and the manganese content in the negative electrode is 110ppm.

[0154] Embodiment 18:

[0155] In the secondary battery of Example 18, the positive electrode active material is LiFePO4, the transition metal salt used in the preparation of the negative electrode plate is ferrous nitrate, and the manganese content in the negative electrode plate is 120 ppm.

[0156] Comparative Example 1:

[0157] The difference between Comparative Example 1 and Example 1 is that the negative electrode plate does not contain a transition metal salt.

[0158] Comparative Example 2:

[0159] The difference between Comparative Example 2 and Example 9 is that the negative electrode plate does not contain a transition metal salt.

[0160] Comparative Example 3:

[0161] The difference between Comparative Example 3 and Example 18 is that the negative electrode plate does not contain a transition metal salt.

[0162] The types and contents of transition metal ions of the positive electrode active materials and negative electrode sheets of the secondary batteries of Examples 1 to 18 and Comparative Examples 1 to 3 are recorded in Table 1.

[0163] Table 1 Types and contents of transition metal ions in the positive electrode active materials and lithium-free negative electrode sheets of the secondary batteries of Examples 1 to 18 and Comparative Examples 1 to 3.

[0164]

[0165] Test part:

[0166] Secondary battery cycle performance test

[0167] At 25°C, charge the secondary battery to 4.25V at 0.5C constant current (if the positive electrode is lithium iron phosphate, the charging cut-off voltage is 3.65V), then charge at 4.25V (3.65V for lithium iron phosphate system) constant voltage to a current of 0.05C, and then discharge at 1C constant current to 2.8V. This is a charge and discharge cycle. Taking the capacity of the first discharge as 100%, calculate the capacity retention rate of the secondary battery after 500 cycles. Capacity retention rate of the secondary battery after 500 cycles (%) = discharge capacity of the 500th cycle / capacity of the first discharge × 100%.

[0168] Secondary battery high temperature storage life performance test

[0169] At 25°C, the secondary battery is charged to 4.25V at a constant current of 0.5C, then charged to a current of 0.05C at a constant voltage of 4.25V, allowed to stand for 10 minutes, and then discharged to 2.8V at a constant current of 1C, and the discharge capacity is recorded as D0. The battery is then placed in a constant temperature furnace at 60°C for 60 days, taken out of the furnace, and cooled naturally. When the surface temperature of the battery cell returns to 25°C, it is discharged to 2.8V at a constant current of 1C, allowed to stand for 10 minutes, charged to 4.25V at a constant current of 0.5C, then charged to 0.05C at a constant voltage, allowed to stand for 10 minutes, and discharged to 2.8V at a constant current of 1C, and the discharge capacity is recorded as D1. The reversible capacity retention rate of the battery cell during high temperature storage life = D1 / D0*100%.

[0170] The cycle performance and high temperature storage life data of the secondary battery are recorded in Table 2.

[0171] Table 2 Cycle performance and high temperature storage life of secondary batteries of Examples 1 to 18 and Comparative Examples 1 to 3

[0172]

[0173]

[0174] It can be seen from the relevant data in Table 2 that the capacity retention rate of the secondary batteries of Examples 1 to 18 after 500 cycles at room temperature (25°C) is 90.3% to 98.2%, and the reversible capacity retention rate of the storage life at 60°C is 89.2% to 96.0%. Compared with the secondary batteries of the same system in Comparative Examples 1 to 3 where the negative electrode plates do not contain transition metal salts, the secondary batteries of Examples 1 to 18 have better cycle life and high temperature storage life.

[0175] In the secondary batteries of Examples 1 to 8, the positive electrode active material is LiMn2O4, the transition metal salt in the negative electrode plate is manganese nitrate, and the content of the transition metal element in the negative electrode active material layer in Examples 2 to 5 is 20ppm to 200ppm, and the cycle life and high temperature storage life performance of the secondary batteries are better.

[0176] In the secondary batteries of Examples 9 to 16, the positive electrode active material is Li[Ni 0.5 Co 0.2 Mn 0.3 ]O2, the transition metal elements dissolved from the positive electrode active material are mainly Mn, and a small amount of Co and Ni will also be dissolved. It can be seen from the relevant data of Examples 9 to 12 that the transition metal salts in the negative electrode plates of Examples 9 to 12 are manganese salts, nickel salts, cobalt salts, and ferrous salts, respectively. Relative to the secondary batteries of Examples 10 to 12, the transition metal elements of the negative electrode plates in Example 9 are the same as the main dissolved transition metal elements in the positive electrode active materials, and the cycle performance and high-temperature storage life performance of the secondary battery are better than those of the secondary batteries of Examples 10 to 12. The transition metal elements of the negative electrode plates in Example 12 are different from the transition metal elements in the positive electrode active materials, and the cycle performance and high-temperature storage life performance of the secondary battery are slightly inferior to those of Examples 9 to 11. The transition metal salts in the negative electrode plates of Examples 13 to 16 are sulfonates, oxalates, acetates, and carbonates, respectively. The cycle performance and high-temperature storage life performance of the secondary battery of Example 16 using carbonates are better than those of the secondary batteries of Examples 13 to 15.

[0177] In the secondary battery of Example 17, the positive electrode active material is Li[Ni 0.9 Co 0.1 Mn 0.1 ]O2, the transition metal element dissolved from the positive electrode active material is mainly Ni, and the transition metal salt in the negative electrode plate is nickel salt. The capacity retention rate of the secondary battery of Example 17 after 500 cycles at room temperature (25°C) is 95.3%, and the reversible capacity retention rate of the storage life at 60°C is 94.7%. The secondary battery has good cycle life and high temperature storage life.

[0178] In the secondary battery of Example 18, the positive electrode active material is LiFePO4, and the transition metal salt in the negative electrode plate is ferrous nitrate. The capacity retention rate of the secondary battery of Example 18 after 500 cycles at room temperature (25°C) is 98.2%, and the reversible capacity retention rate of the storage life at 60°C is 96.0%. The secondary battery has good cycle life and high temperature storage life.

[0179] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0180] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solutions of the present application in detail, but cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the protection scope of the attached claims described in the present application. Therefore, the protection scope of the patent of this application shall be based on the contents of the attached claims, and the description and drawings can be used to explain the contents of the claims.

Claims

1. A lithium-free negative electrode plate, characterized in that: include: Anode current collector; and A negative electrode active material layer is disposed on the surface of the negative electrode current collector; the negative electrode active material layer comprises a transition metal salt, and the transition metal salt comprises at least one of nitrate, oxalate, sulfonate, acetate and carbonate.

2. The lithium-free negative electrode plate according to claim 1, characterized in that: In the transition metal salt, the transition metal element includes at least one of Co, Ni, Mn, Fe, Cu, Zn, Cr, V and Ti.

3. The lithium-free negative electrode plate according to claim 2, characterized in that: In the negative electrode active material layer, the content of the transition metal element is 10 ppm to 850 ppm.

4. The lithium-free negative electrode plate according to claim 3, characterized in that: In the negative electrode active material layer, the content of the transition metal element is 20 ppm to 800 ppm.

5. The lithium-free negative electrode sheet according to claim 3, characterized in that: In the negative electrode active material layer, the content of the transition metal element is 20 ppm to 500 ppm.

6. The lithium-free negative electrode plate according to claim 3, characterized in that: In the negative electrode active material layer, the content of the transition metal element is 20 ppm to 200 ppm.

7. The lithium-free negative electrode plate according to claim 1, characterized in that: The transition metal salt is selected from at least one of nitrates, oxalates, sulfonates and acetates.

8. The lithium-free negative electrode sheet according to any one of claims 1 to 7, characterized in that: In a direction from a surface of the negative electrode active material layer away from the negative electrode current collector to the negative electrode current collector, a distribution depth of the transition metal salt is 10 nm to 100 nm.

9. The lithium-free negative electrode plate according to claim 8, characterized in that: The distribution depth of the transition metal salt is 30nm to 80nm.

10. The lithium-free negative electrode sheet according to any one of claims 1 to 7, characterized in that: The negative electrode active material in the negative electrode active material layer includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase micro carbon beads, silicon-based materials and tin-based materials.

11. A method for preparing a lithium-free negative electrode sheet, characterized in that: The following steps are involved: preparing a negative electrode active material layer on at least one surface of a negative electrode current collector to prepare a lithium-free electrode sheet; The lithium-free electrode sheet is immersed in a solution containing a transition metal salt, so that the transition metal salt penetrates into the negative electrode active material layer. The transition metal salt includes at least one of nitrate, oxalate, sulfonate, acetate and carbonate.

12. The method for preparing a lithium-free negative electrode sheet according to claim 11, characterized in that: In the transition metal salt, the transition metal element includes at least one of Co, Ni, Mn, Fe, Cu, Zn, Cr, V and Ti.

13. The method for preparing a lithium-free negative electrode sheet according to claim 12, characterized in that: In the negative electrode active material layer, the content of the transition metal element is 10 ppm to 850 ppm.

14. The method for preparing a lithium-free negative electrode sheet according to claim 13, characterized in that: In the negative electrode active material layer, the content of the transition metal element is 20 ppm to 800 ppm.

15. The method for preparing a lithium-free negative electrode sheet according to claim 13, characterized in that: In the negative electrode active material layer, the content of the transition metal element is 20 ppm to 500 ppm.

16. The method for preparing a lithium-free negative electrode sheet according to claim 13, characterized in that: In the negative electrode active material layer, the content of the transition metal element is 20 ppm to 200 ppm.

17. The method for preparing a lithium-free negative electrode sheet according to claim 11, characterized in that: The transition metal salt is selected from at least one of nitrates, oxalates, sulfonates and acetates.

18. The method for preparing a lithium-free negative electrode sheet according to claim 11, characterized in that: In a direction from a surface of the negative electrode active material layer away from the negative electrode current collector to the negative electrode current collector, a distribution depth of the transition metal salt is 10 nm to 100 nm.

19. The method for preparing a lithium-free negative electrode sheet according to claim 18, characterized in that: The distribution depth of the transition metal salt is 30nm to 80nm.

20. The method for preparing a lithium-free negative electrode sheet according to any one of claims 11 to 19, characterized in that: The solvent of the solution is selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl acetate and tetrahydrofuran.

21. The method for preparing a lithium-free negative electrode sheet according to claim 20, characterized in that: The solvent of the solution is dimethyl carbonate.

22. The method for preparing a lithium-free negative electrode sheet according to any one of claims 11 to 19, characterized in that: The mass percentage of the transition metal salt in the solution is 1% to 30%.

23. The method for preparing a lithium-free negative electrode sheet according to claim 22, characterized in that: The mass percentage of the transition metal salt in the solution is 5% to 10%.

24. The method for preparing a lithium-free negative electrode sheet according to any one of claims 11 to 19, characterized in that: The soaking time is 15min to 180min.

25. A secondary battery, characterized in that: It comprises the lithium-free negative electrode sheet as described in any one of claims 1 to 10 or the lithium-free negative electrode sheet prepared by the method for preparing the lithium-free negative electrode sheet as described in any one of claims 11 to 24.

26. The secondary battery according to claim 25, characterized in that: The secondary battery further includes a positive electrode active material; the positive electrode active material contains a transition metal element.

27. The secondary battery according to claim 26, characterized in that: The positive electrode active material is selected from Li[Ni x Co y N z M 1-x-y-z ]At least one of O2, LiMn2O4, Li2MnO3·(1-a)LiAO2 and LiFePO4; Wherein, N is selected from one of Mn and Al; M is selected from one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti; 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1; A is selected from one of Ni, Co and Mn; 0<a<1.

28. The secondary battery according to claim 26 or 27, characterized in that: The transition metal element of the lithium-free negative electrode plate is the same as the transition metal element in the positive electrode active material.

29. The secondary battery according to any one of claims 25 to 27, characterized in that: The secondary battery further includes an electrolyte; the electrolyte contains an additive.

30. The secondary battery according to claim 29, characterized in that: The additive is selected from at least one of vinylene carbonate, vinyl sulfate, lithium bis(oxalatoborate), lithium oxalatodifluoroborate, fluoroethylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate and 1,3-propane sultone.

31. The secondary battery according to claim 29, characterized in that: In the electrolyte, the mass percentage of the additive is 0.1% to 5%.

32. The secondary battery according to claim 31, characterized in that: In the electrolyte, the mass percentage of the additive is 0.5% to 2%.

33. A battery module, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 25 to 32.

34. A battery pack, characterized in that: Comprising the battery module as claimed in claim 33.

35. An electrical device, characterized in that: The battery comprises at least one selected from the group consisting of the secondary battery according to any one of claims 25 to 32, the battery module according to claim 33, and the battery pack according to claim 34.

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