A battery

Abstract

The present invention provides a battery, comprising a positive electrode plate, a negative electrode plate, an electrolyte and a separator; the positive electrode plate comprises a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector; the negative electrode plate comprises a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector; the battery satisfies 0.45 ≤ 1000×(25p1 2 + 16p2 2 )×p3 / (c×t) ≤ 0.6. Compared with the prior art, by reasonably matching the positive electrode coating surface density, the coating porosities of the positive and negative electrodes, the separator porosity and the separator thickness, the battery prepared by the present invention has excellent energy density and can provide high-power output performance, meeting the usage requirements of EVTOL.

Description

Technical Field

[0001] The present invention belongs to the technical field of ion batteries, and particularly relates to a battery. Background Art

[0002] Electric vertical take-off and landing aircraft (EVTOL) has attracted wide attention due to its advantages such as low energy consumption, no pollution, low noise, and high comfort. It can be applied to various scenarios such as regional passenger transportation, freight transportation, and emergency medical treatment, and has a broad market.

[0003] One of the main challenges of current EVTOL is battery technology. During the vertical take-off and landing and long-distance flight of the aircraft, extremely high requirements are placed on the energy density and power performance of the battery. In view of this, providing a battery with high energy density and high power performance is a necessary condition for promoting the development of EVTOL. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a battery with high energy density and high power performance.

[0005] The present invention provides a battery, comprising a positive electrode plate, a negative electrode plate, an electrolyte, and a separator;

[0006] The positive electrode plate includes a positive current collector and a positive active material layer provided on at least one surface of the positive current collector;

[0007] The negative electrode plate includes a negative current collector and a negative active material layer provided on at least one surface of the negative current collector;

[0008] The battery satisfies 0.45 ≤ 1000×(25p1 2 +16p2 2 )×p3 / (c×t) ≤ 0.6;

[0009] Wherein, p1 is the porosity of the positive active material layer; p2 is the porosity of the negative active material layer; p3 is the porosity of the separator; c is the single-sided surface density of the positive active material layer, with the unit of g / m 2 ; t is the thickness of the separator, with the unit of μm.

[0010] Preferably, the porosity p1 of the positive active material layer is 24% - 29%.

[0011] Preferably, the porosity p2 of the negative active material layer is 25% - 33%.

[0012] Preferably, the porosity p3 of the separator is 42% - 48%.

[0013] Preferably, the single-sided surface density c of the positive active material layer is 150 - 200 g / m 2。

[0014] Preferably, the thickness t of the separator is 14 to 18 μm.

[0015] Preferably, the positive electrode active material layer includes a positive electrode active material; the mass of the positive electrode active material is 94% to 98% of the mass of the positive electrode active material layer;

[0016] The negative electrode active material layer includes a negative electrode active material; the mass of the negative electrode active material is 92% to 97% of the mass of the negative electrode active material layer.

[0017] Preferably, the positive electrode active material is selected from LiNi x Co y Mn 1-x-y O2 ternary material, where x is greater than 0.7;

[0018] The negative electrode active material is selected from silicon-based materials and / or graphite.

[0019] Preferably, the separator is selected from polyethylene, polypropylene or polyethylene / polypropylene separator;

[0020] The electrolyte includes a lithium salt and a solvent;

[0021] The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium trifluoromethanesulfonate, lithium difluoro(oxalato)borate, lithium difluorophosphate, 4,5-dicyano-2-trifluoromethylimidazole lithium, lithium difluorodioxalate phosphate and lithium tetrafluorooxalate phosphate;

[0022] The solvent is selected from one or more of 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, methyl propionate, ethyl propionate, propyl acetate and propyl propionate.

[0023] Preferably, the concentration of the lithium salt in the electrolyte is 0.1 to 6 mol / L.

[0024] The present invention provides a battery, comprising a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator; 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; the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector; the battery satisfies 0.45 ≤ 1000×(25p1 2 +16p2 2)×p3 / (c×t) ≤ 0.6; where p1 is the porosity of the positive electrode active material layer; p2 is the porosity of the negative electrode active material layer; p3 is the porosity of the separator; c is the single-sided areal density of the positive electrode active material layer, in g / m 2 ; t is the thickness of the separator, in μm. Compared with the prior art, by reasonably matching the areal density of the positive electrode coating, the coating porosities of the positive and negative electrodes, the porosity of the separator, and the thickness of the separator, the battery prepared by the present invention has excellent energy density and can provide high-power output performance, meeting the usage requirements of EVTOL. Detailed Embodiments

[0025] The technical solutions in the embodiments 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 a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0026] The present invention discovers that for a battery, the porosity of the positive electrode active material layer, the porosity of the separator, and the thickness of the separator all have a great influence on the power performance and energy density of the battery. Based on this, the present invention provides a battery, including a positive electrode plate, a negative electrode plate, an electrolyte, and a separator; the positive electrode plate 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; the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector; the battery satisfies 0.45 ≤ 1000×(25p1 2 +16p2 2 )×p3 / (c×t) ≤ 0.6; where p1 is the porosity of the positive electrode active material layer; p2 is the porosity of the negative electrode active material layer; p3 is the porosity of the separator; c is the single-sided areal density of the positive electrode active material layer, in g / m 2 ; t is the thickness of the separator, in μm.

[0027] When designing the battery cell, the porosity of the positive electrode active material layer, the porosity of the negative electrode active material layer, the porosity of the separator, and the areal density of the positive electrode active material layer all affect the energy density and power performance of the battery cell. However, their influences have certain limitations and correlations. Only when the formula 0.45 ≤ 1000×(25p1 2 +16p2 2 )×p3 / (c×t) ≤ 0.6 is satisfied can the battery cell have both power performance and energy density. Guided by the above formula, a large number of DOE tests can be avoided, saving the time and cost of battery research and development, and enabling the designed battery to have excellent power performance and energy density.

[0028] In the present invention, 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.

[0029] The positive electrode current collector can be a positive electrode current collector well-known to those skilled in the art without any special limitation. In the present invention, it is preferably aluminum foil, carbon-coated aluminum foil or nickel mesh; the thickness of the positive electrode current collector is preferably 3 to 50 μm, more preferably 5 to 30 μm, still more preferably 5 to 20 μm, and most preferably 8 to 11 μm.

[0030] A positive electrode active material layer is disposed on the positive electrode current collector; the positive electrode active material layer can be disposed on one surface of the positive electrode current collector, or both surfaces can be provided with the positive electrode active material layer without any special limitation; the positive electrode active material layer includes positive electrode active material; the mass of the positive electrode active material is preferably 94% to 98% of the mass of the positive electrode active material layer, more preferably 96% to 97%; the positive electrode active material is preferably one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and lithium-containing phosphate with olivine structure, more preferably LiNi x Co y Mn 1-x-y O2 ternary material, where x is greater than 0.7; in the present invention, the specific x is 0.8 to 0.9; specifically, y is greater than 0 and less than 0.3, further specifically, y is greater than 0 and less than 0.2, and still further specifically, y is 0.05 to 0.1; the true density of the positive electrode active material is preferably 4.5 to 5.0 g / cm 3 , more preferably 4.6 to 4.9 g / cm 3 , still more preferably 4.7 to 4.8 g / cm 3 ; the positive electrode active material layer preferably further includes a positive electrode conductive agent; the mass of the positive electrode conductive agent is preferably 1% to 2% of the mass of the positive electrode active material layer; the positive electrode conductive agent can be a conductive agent well-known to those skilled in the art without any special limitation. In the present invention, it is preferably one or more of conductive graphite, conductive carbon black, conductive carbon fiber, carbon nanotube and graphene; the true density of the positive electrode conductive agent is preferably 1.5 to 2.0 g / cm 3 , more preferably 1.6 to 1.9 g / cm 3 , still more preferably 1.7 to 1.8 g / cm 3; The positive electrode active material layer preferably further includes a positive electrode binder; the mass of the positive electrode binder is preferably 0.8% to 2% of the mass of the positive electrode active material layer, more preferably 0.8% to 1.5%, and still more preferably 1% to 1.2%; the positive electrode binder can be any binder well-known to those skilled in the art without special limitations. In the present invention, it is preferably one or more of chitosan, xanthan gum, gellan gum, arabic gum, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, polymethacrylyl, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, polyacrylamide, styrene-butadiene rubber, sodium alginate, polyethylene glycol, guar gum, guar gum polymer and guar gum copolymer; the true density of the positive electrode binder is preferably 1.5 to 2.0 g / cm 3 , more preferably 1.6 to 1.9 g / cm 3 , still more preferably 1.7 to 1.8 g / cm 3 , most preferably 1.75 to 1.77 g / cm 3 .

[0031] During battery charge and discharge, lithium ions are deintercalated and intercalated between the positive electrode materials. The deintercalation and intercalation processes of lithium ions are closely related to the porosity of the positive electrode plate. On the one hand, when the porosity of the positive electrode active material layer decreases, the electron conductive network in the electrode is improved and the internal resistance decreases. However, if the porosity is too low, the liquid absorption performance will decrease, the electrochemical reaction interface will decrease, and the ion transport channels will be blocked, resulting in poor power performance of the battery; on the other hand, when the porosity of the positive electrode active material layer increases, the wettability of the electrolyte is good, the ion channels increase, which helps to improve the ion transport rate. However, if the porosity is too high, the conductive network of the electrode plate will become worse, the internal resistance of the battery will increase, and in addition, too high porosity will also lead to a decrease in energy density. Therefore, in the present invention, the porosity p1 of the positive electrode active material layer is preferably 24% to 29%, more preferably 24.2% to 28.8%, and still more preferably 24.41% to 28.73%; when the porosity of the positive electrode active material layer meets the above value range, it can effectively ensure that the power performance and energy density of the battery meet the requirements. In some embodiments provided by the present invention, the porosity p1 of the positive electrode active material layer is specifically 26.57%, 28.73% or 24.41%.

[0032] When the areal density of the electrode plate is lower, the contact resistance decreases, the ion transport distance is also shortened, and at the same time, the SEI film formed during formation is thin and stable, which will reduce the lithium ion migration resistance and improve the power performance of the battery cell. However, if the areal density is too low, the proportion of the current collector in the electrode plate increases, which will cause the energy density of the lithium ion battery to be too low. Controlling the areal density within a suitable range can improve the power performance of the battery and ensure that the energy density of the battery will not be too low. Therefore, in the present invention, the single-sided areal density c of the positive electrode active material layer is preferably 150 to 200 g / m 2; In some embodiments provided by the present invention, the single-sided surface density c of the positive electrode active material layer is specifically 175 g / m 2 , 150 g / m 2 or 200 g / m 2 .

[0033] In the present invention, the porosity of the positive electrode active material layer can be adjusted by controlling the compaction density of the electrode sheet and the true density of the material. In this application, the porosity of the electrode sheet has the meaning well-known in the art and can be measured by methods known in the art. Specifically, the porosity values in the embodiments of the present invention are all measured by the cetane adsorption method, and the specific test method refers to the national standard GB / T 33052-2016; the compaction density of the positive electrode active material layer is preferably 3.3-3.5 g / cm 3 ; In the embodiments provided by the present invention, the compaction density of the positive electrode active material layer is specifically 3.4 g / cm 3 , 3.3 g / cm 3 or 3.5 g / cm 3 .

[0034] In the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector.

[0035] The negative electrode current collector can be a negative electrode current collector well-known to those skilled in the art without special limitations. In the present invention, it is preferably copper foil; the thickness of the negative electrode current collector is preferably 3-50 μm, more preferably 4-30 μm, still more preferably 4-20 μm, and most preferably 4.5-8 μm.

[0036] A negative electrode active material layer is provided on the negative electrode current collector; a negative electrode active material layer is provided on one surface of the negative electrode current collector, or negative electrode active material layers can be provided on both surfaces without special limitations; the negative electrode active material layer includes negative electrode active material; the mass of the negative electrode active material is 94%-98% of the mass of the negative electrode active material layer, more preferably 95%-98%, still more preferably 96%-97%, and most preferably 96.5%; the negative electrode active material can be a negative electrode active material well-known to those skilled in the art without special limitations. In the present invention, it is preferably one or more of silicon-based materials, graphite, soft carbon, hard carbon, carbon fiber and mesophase carbon microspheres, more preferably silicon-based materials and / or graphite; the true density of the negative electrode active material is preferably 2-2.5 g / cm 3 , more preferably 2.1-2.2 g / cm 3 , still more preferably 2.23 g / cm 3; The negative electrode active material layer preferably further includes a negative electrode conductive agent; the mass of the negative electrode conductive agent is preferably 0.2% to 10% of the mass of the negative electrode active material layer, more preferably 0.5% to 8%, still more preferably 0.8% to 5%, and most preferably 1% to 3%; the negative electrode conductive agent is preferably one or more of conductive graphite, conductive carbon black, conductive carbon fiber, carbon nanotube, and graphene; the true density of the negative electrode conductive agent is preferably 1.5 to 2.0 g / cm 3 , more preferably 1.6 to 1.9 g / cm 3 , still more preferably 1.7 to 1.8 g / cm 3 ; The negative electrode active material layer preferably further includes a negative electrode binder; the negative electrode binder is preferably 0.3% to 10% of the mass of the negative electrode active material layer, more preferably 0.5% to 8%, still more preferably 1% to 5%, and most preferably 2% to 4%; the negative electrode binder is preferably one or more of chitosan, xanthan gum, gellan gum, arabic gum, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, polymethacrylamide, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, polyacrylamide, styrene-butadiene rubber, sodium alginate, polyethylene glycol, guar gum, guar gum polymer, and guar gum copolymer; the true density of the negative electrode binder is preferably 1.2 to 2.0 g / cm 3 , more preferably 1.2 to 1.8 g / cm 3 , still more preferably 1.26 to 1.6 g / cm 3 ; The single-sided surface density of the negative electrode active material layer is preferably 100 to 130 g / m 2 , more preferably 105 to 125 g / m 2 , still more preferably 110 to 120 g / m 2 , most preferably 110 to 115 g / m 2 ; In some embodiments provided by the present invention, the single-sided surface density of the negative electrode active material layer is specifically 112 g / m 2 .

[0037] Similar to the porosity of the above-mentioned positive electrode active material layer, the porosity of the negative electrode active material layer also affects the power performance and energy density of the battery; in the present invention, the porosity p2 of the negative electrode active material layer is preferably 25% to 33%, more preferably 25.5% to 32.6%, still more preferably 25.58% to 32.56%; when the porosity of the negative electrode active material layer meets the above-mentioned value range, the power performance and energy density of the battery can be effectively guaranteed; in some embodiments provided by the present invention, the porosity of the negative electrode active material layer is specifically 32.56%, 30.23%, 27.91%, or 25.58%.

[0038] In the present invention, the porosity of the negative electrode active material layer can be adjusted by the true density of the materials used and the tap density of the negative electrode active material layer; the tap density of the negative electrode active material layer is preferably 1.48-1.63 g / cm 3 ; in the embodiments provided by the present invention, the tap density of the positive electrode active material layer is specifically 1.48 g / cm 3 , 1.53 g / cm 3 , 1.58 g / cm 3 or 1.63 g / cm 3 .

[0039] The conduction ability of electrolyte cations in the separator is directly related to the overall performance of the lithium battery. The porosity of the separator directly affects the conduction ability of electrolyte cations. The larger the porosity, the better the liquid absorption performance of the separator, the more perfect the ion transport channels, the stronger the ion conduction ability, and the better the power performance. However, if the porosity is too large, the separator is easily pierced by foreign objects or electrolyte metal dendrites, causing internal short circuit of the battery and thus triggering safety hazards. Controlling the porosity of the separator within a suitable range can improve the power performance on the premise of ensuring safety performance. Therefore, in the present invention, the porosity p3 of the separator is preferably 42%-48%; in some embodiments provided by the present invention, the porosity p3 of the separator is specifically 45%, 42% or 48%.

[0040] The thickness of the separator directly affects the transport distance of lithium ions. The thinner the separator, the shorter the transport distance of lithium ions, which will reduce the migration resistance of lithium ions and improve the power performance. In addition, the thinner the separator, the more space can be left for the active material of the electrode in the battery cell, thereby increasing the power density; however, if the separator is too thin, the mechanical strength of the separator will be greatly reduced, affecting the safety performance of the battery cell. Therefore, controlling the thickness of the separator within a suitable range can ensure safety performance while improving power performance and energy density. Therefore, in the present invention, the thickness t of the separator is preferably 14-18 μm; in some embodiments provided by the present invention, the thickness t of the separator is specifically 16 μm, 14 μm or 18 μm.

[0041] In the present invention, the type of the separator may be any separator well-known to those skilled in the art, without any special limitation. In the present invention, it is preferably one or more of polyethylene, polypropylene, polyacrylonitrile, polyacrylonitrile fiber, polyamic acid, polyimide, polyamide, polydopamine, polyarylethersulfone, polyvinylidene fluoride, polyethylene oxide, polyethylene terephthalate, polyester, non-woven fabric film and cellulose paper-based separator film, and more preferably polyethylene, polypropylene or polyethylene / polypropylene separator; in the present invention, the polymer separator may be a single-layer film, a double-layer film or a multi-layer film, without any special limitation; in another specific embodiment provided by the present invention, the polymer separator may further include a coating layer; the thickness of the coating layer is preferably 1-8 μm; the coating layer preferably includes one or more of aluminum oxide, titanium dioxide, zirconium oxide, barium titanate, yttrium-doped zirconium oxide, gadolinium-doped cerium oxide, lithium metaaluminate, lithium lanthanum titanate, lithium aluminum titanium phosphate, lithium lanthanum zirconate and lithium lanthanum tantalum zirconate.

[0042] According to the present invention, the electrolyte may be any electrolyte well-known to those skilled in the art, without any special limitation. In the present invention, the electrolyte preferably includes an electrolyte salt and a solvent; the electrolyte salt is preferably a lithium salt or a sodium salt; the lithium salt is preferably one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium trifluoromethanesulfonate, lithium difluoroborate oxalate, lithium difluorophosphate, lithium 4,5-dicyano-2-(trifluoromethyl)imidazole, lithium difluorodioxalate phosphate and lithium tetrafluorooxalate phosphate; the solvent is preferably one or more of 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, methyl propionate, ethyl propionate, propyl acetate and propyl propionate; the concentration of the lithium salt in the electrolyte is preferably 0.1-6 mol / L, more preferably 0.5-4 mol / L, still more preferably 1-3 mol / L, and most preferably 1-2 mol / L; in the examples provided by the present invention, the concentration of the electrolyte salt in the electrolyte is specifically 1.2 mol / L.

[0043] According to the present invention, the battery preferably further includes a housing; the positive electrode, negative electrode, electrolyte and separator are all disposed within the housing.

[0044] In the present invention, the battery can be prepared into batteries with different structures according to the needs, without any special limitation. In the present invention, it preferably includes but is not limited to square shell batteries, cylindrical batteries or soft-pack batteries.

[0045] In the present invention, the battery can be selected as a wound type or a stacked type according to the situation, and the manufacturing method is not limited.

[0046] In the present invention, the battery is preferably a lithium battery.

[0047] By reasonably matching the surface density of the positive electrode coating, the coating porosities of the positive and negative electrodes, the porosity of the separator, and the thickness of the separator, the prepared battery has excellent energy density and can provide high-power output performance, meeting the usage requirements of EVTOL.

[0048] To further illustrate the present invention, a battery provided by the present invention will be described in detail below in conjunction with embodiments.

[0049] All reagents used in the following examples are commercially available.

[0050] Example 1

[0051] Preparation of the positive electrode sheet: The positive electrode active material is selected as lithium nickel cobalt manganese oxide (LiNi 3 Co x Co y Mn 1-x-y O2 ternary material, x = 0.8, y = 0.1), the conductive agent is selected as SP with a true density of 1.8 g / cm 3 and carbon nanotubes with a true density of 1.8 g / cm 3 (the mass ratio of SP to carbon nanotubes is 1.3:0.7), the binder is selected as PVDF5130 with a true density of 1.77 g / cm 3 The positive electrode current collector is selected as 10-μm aluminum foil. After mixing the positive electrode active material, the conductive agent, and the binder in a ratio of 97:2:1, NMP is added and stirred into a uniformly mixed and stable positive electrode slurry. The solid content of the positive electrode slurry is 75%. The positive electrode slurry is uniformly coated on the positive electrode current collector, and the coating surface density c is 175 g / m 2 , and after drying and cold pressing, a positive electrode sheet is obtained. The selected compaction density is 3.4 g / cm 3 , and the porosity p1 of the positive electrode active material layer is 26.57% through the true density and compaction density of the material;

[0052] Preparation of the negative electrode sheet: The negative electrode active material is selected as graphite with a true density of 2.23 g / cm 3 The conductive agent is selected as SP with a true density of 1.8 g / cm 3 The binder is selected as CMC with a true density of 1.6 g / cm 3 and SBR with a true density of 1.26 g / cm 3 . The negative electrode current collector is selected as 6-μm copper foil. After mixing the negative electrode active material, the conductive agent, CMC, and SBR in a ratio of 96.5:1:1:1.5, deionized water is added and stirred into a uniformly mixed and stable negative electrode slurry. The solid content of the negative electrode slurry is 50%. The negative electrode slurry is uniformly coated on the negative electrode current collector, and the coating surface density is 112 g / m 2, after drying and cold pressing, the negative electrode sheet is obtained. The selected compaction density is 1.48 g / cm 3 , and the porosity p2 of the negative electrode active material layer is obtained as 32.56% through the true density and compaction density of the material;

[0053] Selection of separator: A polypropylene film is selected as the separator base film, and PVDF ceramics are coated on one side with a coating thickness of 3 μm. The porosity p3 of the separator is 45%, and the thickness t is 16 μm.

[0054] During the cell assembly process, the positive electrode sheet, separator, negative electrode sheet, and separator are arranged in sequence, and the winding method is selected for assembly.

[0055] Preparation of electrolyte: LiPF6 is selected and dissolved in a solvent with a volume ratio of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate of 1:1:1, with a concentration of 1.2 mol / L.

[0056] The electrolyte is injected into the dry cell. After soaking for 24 h, formation is carried out at 45°C. The formation process: charge at 0.05C to 3.4V, and then charge at 0.2C to 3.75V; after aging at room temperature for 24 hours, the cell production is completed.

[0057] Taking Example 1 as a reference, Examples 2-9 and Comparative Examples 1-8 are prepared again.

[0058] Example 2

[0059] For Example 2, other conditions are the same as those in Example 1, except for the porosity of the negative electrode active material layer. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative electrode active material layer is obtained as 30.23%.

[0060] Example 3

[0061] For Example 3, other conditions are the same as those in Example 1, except for the porosity of the negative electrode active material layer. Without changing the negative electrode material, by adjusting the compaction density to 1.58 g / cm 3 , the porosity p2 of the negative electrode active material layer is obtained as 27.91%.

[0062] Example 4

[0063] For Example 4, other conditions are the same as those in Example 1, except for the porosities of the positive and negative electrode active material layers. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative electrode active material layer is obtained as 30.23%; without changing the positive electrode material, by adjusting the compaction density to 3.3 g / cm 3 , the porosity p1 of the positive electrode is obtained as 28.73%.

[0064] Example 5

[0065] In Example 5, other conditions are the same as those in Example 1, except for the porosity of the positive and negative active material layers. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 30.23%; without changing the positive electrode material, by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 24.41%.

[0066] Example 6

[0067] In Example 6, other conditions are the same as those in Example 1, except for the porosity of the positive and negative active material layers and the positive electrode surface density. Without changing the negative electrode material, by adjusting the compaction density to 1.63 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 25.58%; without changing the positive electrode material, changing the coating weight, and adjusting the coating surface density c to 150 g / m 2 , by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 24.41%.

[0068] Example 7

[0069] In Example 7, other conditions are the same as those in Example 1, except for the porosity of the positive and negative active material layers and the positive electrode surface density. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 30.23%; without changing the positive electrode material, changing the coating weight, and adjusting the coating surface density c to 200 g / m 2 , by adjusting the compaction density to 3.3 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 28.73%.

[0070] Example 8

[0071] In Example 8, other conditions are the same as those in Example 1, except for the porosity of the positive and negative active material layers, the porosity of the separator, and the thickness. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 30.23%; without changing the positive electrode material, by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 24.41%, and a separator with a porosity p3 of 48% and a thickness t of 18 μm is selected.

[0072] Example 9

[0073] Example 9 is the same as Example 1 in other conditions, except for the porosity of the positive and negative active material layers, the porosity and thickness of the separator. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 30.23%; without changing the positive electrode material, by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 24.41%, and the separator with a porosity p3 of 42% and a thickness t of 14 μm is selected.

[0074] Comparative Example 1

[0075] Comparative Example 1 is the same as Example 1 in other conditions, except for the porosity of the positive and negative active material layers and the positive electrode surface density. Without changing the negative electrode material, by adjusting the compaction density to 1.33 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 39.53%; without changing the positive electrode material, by changing the coating weight, the coating surface density c is adjusted to 140 g / m 2 , and by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 24.41%.

[0076] Comparative Example 2

[0077] Comparative Example 2 is the same as Example 1 in other conditions, except for the porosity of the positive and negative active material layers and the positive electrode surface density. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 30.23%; without changing the positive electrode material, by changing the coating weight, the coating surface density c is adjusted to 220 g / m 2 , and by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 24.41%.

[0078] Comparative Example 3

[0079] Comparative Example 3 is the same as Example 1 in other conditions, except for the porosity of the positive and negative active material layers. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 30.23%; without changing the positive electrode material, by adjusting the compaction density to 2.9 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 37.37%.

[0080] Comparative Example 4

[0081] For Comparative Example 4, other conditions are the same as those in Example 1, except for the porosity of the positive and negative active material layers. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 30.23%; without changing the positive electrode material, by adjusting the compaction density to 3.74 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 19.22%.

[0082] Comparative Example 5

[0083] For Comparative Example 5, other conditions are the same as those in Example 1, except for the porosity of the positive and negative active material layers and the separator thickness. Without changing the negative electrode material, by adjusting the compaction density to 1.29 g / cm 3 , the porosity p2 of the negative pore active material layer is obtained as 41.19%; without changing the positive electrode material, by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 24.41%, and the separator thickness t of 18 μm is selected.

[0084] Comparative Example 6

[0085] For Comparative Example 6, other conditions are the same as those in Example 1, except for the porosity of the positive and negative active material layers and the separator thickness. Without changing the negative electrode material, by adjusting the compaction density to 1.69 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 23.26%; without changing the positive electrode material, by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 24.41%, and the separator thickness t of 18 μm is selected.

[0086] Comparative Example 7

[0087] For Comparative Example 7, other conditions are the same as those in Example 1, except for the porosity of the positive and negative active material layers and the separator thickness. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3 , the porosity p2 of the negative active material layer is obtained as 30.23%; without changing the positive electrode material, by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive active material layer is obtained as 24.41%, and the separator thickness t of 20 μm is selected.

[0088] Comparative Example 8

[0089] For Comparative Example 8, other conditions are the same as those in Example 1, except for the porosity of the positive and negative active material layers and the separator thickness. Without changing the negative electrode material, by adjusting the compaction density to 1.53 g / cm 3, the porosity p2 of the negative electrode active material layer is obtained as 30.23%; without changing the positive electrode material, by adjusting the compaction density to 3.5 g / cm 3 , the porosity p1 of the positive electrode active material layer is obtained as 24.41%, and the separator porosity p3 of 38% and thickness t of 18 μm are selected.

[0090] The batteries prepared in Examples 1-9 and Comparative Examples 1-8 were tested for energy density and rate discharge capacity retention rate, and the results are shown in Table 1. Among them, the energy density was measured under the conditions of 25 °C and 1C; the rate discharge capacity retention rate was the ratio of the discharge capacities measured at 5C and 0.33C after being fully charged at 25 °C, and the higher the retention rate, the better the power performance.

[0091] Table 1 Specific parameters and performance test results of lithium-ion batteries

[0092]

[0093]

[0094] As can be seen from Table 1, Examples 1-9 are preferred solutions. The porosity p1 of the positive electrode active material layer, the porosity p2 of the negative electrode active material layer, the porosity p3 of the separator, the single-sided surface density c of the positive electrode active material layer, and the separator thickness t satisfy 1000×(25p1 2 +16p2 2 )×p3 / (c×t) requirements, and both the energy density and power performance are excellent. In Comparative Example 1, the surface density of the positive electrode active material layer is too low, resulting in too low energy density; in Comparative Example 2, the surface density is too high and does not satisfy 0.45 ≤ 1000*(25p1 2 +16p2 2 )*p3 / (c*t) ≤ 0.6, and its contact resistance is too large, the ion transport distance increases, resulting in poor power performance. In Comparative Example 3, the porosity of the positive electrode is too high, and in Comparative Example 5, the porosity of the negative electrode is too high, and both do not satisfy 0.45 ≤ 1000×(25p1 2 +16p2 2 )×p3 / (c×t) ≤ 0.6, which will lead to a poor conductive network of the electrode sheet and an increase in the internal resistance of the battery, affecting the power performance; in Comparative Example 4, the porosity of the positive electrode is too low, and in Comparative Example 6, the porosity of the negative electrode is too low, and both do not satisfy 0.45 ≤ 1000×(25p1 2 +16p2 2 )×p3 / (c×t) ≤ 0.6, both will lead to a decrease in the liquid absorption performance, a reduction in the electrochemical reaction interface, and a blockage of the ion transport channel, making the power performance of the battery poor; in Comparative Example 7, the separator thickness is too large and does not satisfy 0.45 ≤ 1000×(25p1 2 +16p2 2)×p3 / (c×t) ≤ 0.6, increasing the ion transport distance results in poor power performance; in Comparative Example 8, the porosity of the separator is too low and does not meet 0.45 ≤ 1000×(25p1 2 + 16p2 2 )×p3 / (c×t) ≤ 0.6, the separator has poor liquid absorption performance, insufficient ion transport channels, and poor ion conduction ability, resulting in poor power performance.

[0095] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. However, the present invention is not limited thereto. Those skilled in the art can understand that within the scope of the technical concept of the present invention, the technical solutions of the present invention can be modified, or some technical features can be combined in any other way. These modifications or combinations do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present invention, and should be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A battery, characterized in that, It includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator; The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector; The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector; The battery satisfies 0.45 ≤ 1000×(25p1 2 + 16p2 2 )×p3 / (c×t) ≤ 0.6; wherein, p1 is the porosity of the positive electrode active material layer; p2 is the porosity of the negative electrode active material layer; p3 is the porosity of the separator; c is the areal density per side of the positive electrode active material layer, with the unit of g / m 2 ; t is the thickness of the separator, with the unit of μm; The porosity p1 of the positive electrode active material layer is 24% - 29%; The porosity p2 of the negative electrode active material layer is 25% - 33%; The porosity p3 of the separator is 42% - 48%; The single-sided surface density c of the positive electrode active material layer is 150 to 200 g / m 2 ; The tap density of the positive electrode active material layer is 3.3 to 3.5 g / cm 3 ; The thickness t of the separator is 14 - 18 μm; The positive electrode active material is selected from LiNi x Co y Mn 1-x-y O2 ternary material, where x is greater than 0.7; The true density of the positive electrode active material is 4.5 to 5.0 g / cm 3 ; The negative electrode active material is selected from silicon-based materials and / or graphite; The true density of the negative electrode active material is 2 to 2.5 g / cm 3 ; The single-sided areal density of the negative electrode active material layer is 100 to 130 g / m 2 ; The tap density of the negative electrode active material layer is 1.48 to 1.63 g / cm 3 .

2. The battery according to claim 1, wherein The positive electrode active material layer includes a positive electrode active material; the mass of the positive electrode active material is 94% - 98% of the mass of the positive electrode active material layer; The negative electrode active material layer includes a negative electrode active material; the mass of the negative electrode active material is 92% - 97% of the mass of the negative electrode active material layer.

3. The battery according to claim 1, characterized in that, The separator is selected from polyethylene, polypropylene or polyethylene / polypropylene separator; The electrolyte includes a lithium salt and a solvent; The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium trifluoromethanesulfonate, lithium difluorobis(oxalato)phosphate, lithium difluorophosphate, 4,5-dicyano-2-(trifluoromethyl)imidazole lithium, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate; The solvent is selected from one or more of 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, methyl propionate, ethyl propionate, propyl acetate and propyl propionate.

4. The battery according to claim 3, wherein, The concentration of the lithium salt in the electrolyte is 0.1 - 6 mol / L.

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