Battery cell, battery device, electric device

Abstract

Provided are a battery cell, a battery device, and an electric device. The battery cell comprises a positive electrode sheet and an electrolyte; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer located on at least one surface of the positive electrode current collector; the positive electrode active layer comprises a positive electrode active material; the positive electrode active material comprises a lithium-containing phosphate; the single-sided surface density of the positive electrode active layer ranges from 230 mg / 1540.25 mm2 to 400 mg / 1540.25 mm2; the electrolyte comprises a solvent and a lithium-containing electrolyte salt; the solvent comprises a chain carboxylic acid ester and ethylene carbonate; the lithium-containing electrolyte salt comprises one or more of lithium hexafluorophosphate and a fluorine-containing sulfonimide salt; the mass ratio of the lithium-containing electrolyte salt to the ethylene carbonate is 0.29-0.72; and the conductivity of the electrolyte ranges from 13 mS / cm to 20 mS / cm.

Description

Battery cells, battery packs, and electrical devices Technical Field

[0001] This application relates to the field of battery cell technology, and more particularly to a battery cell, a battery device, and an electrical device. Background Technology

[0002] In recent years, battery cells have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] With the market's increasing demands for both extended driving range and efficient charging of electrical devices, higher requirements are being placed on the energy density and fast charging performance of individual battery cells. However, existing technologies struggle to simultaneously improve these performance characteristics, making this a pressing technical problem that needs to be solved in this field.

[0004] Summary of the Invention

[0005] This application is made in view of the above-mentioned issues, and its purpose is to provide a battery cell that has both high energy density and good fast charging performance.

[0006] A first aspect of this application provides a battery cell, including a positive electrode sheet and an electrolyte; the positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, the positive active layer including a positive active material, the positive active material including a lithium phosphate, and the one-sided lateral density of the positive active layer is 230 mg / 1540.25 mm². 2 ~400mg / 1540.25mm 2 The electrolyte comprises a solvent and a lithium-containing electrolyte salt. The solvent includes chain carboxylic acid esters and ethylene carbonate. The lithium-containing electrolyte salt includes one or more of lithium hexafluorophosphate and fluorosulfonyl imide salts. The mass ratio of the lithium-containing electrolyte salt to ethylene carbonate is 0.29-0.72. The conductivity of the electrolyte is 13 mS / cm-20 mS / cm.

[0007] In the electrolyte, ethylene carbonate readily forms a solvation structure with lithium ions in the lithium-containing electrolyte salt, thereby increasing the dissociation rate of lithium ions and anions in the electrolyte salt. However, with the increase of ethylene carbonate content, the electrolyte viscosity also increases, negatively impacting the electrolyte conductivity. Chain-like carboxylic esters, on the other hand, can improve the wettability between the electrolyte and the electrode, enhancing the solid-liquid transport rate of lithium ions between them. The addition of chain-like carboxylic esters also contributes to improving the electrolyte conductivity. Lithium-phosphate cathode electrodes with a single-sided lateral density within the aforementioned range possess both high lithium-ion solid-phase transport rates and high positive electrode active material loading. By combining these electrolytes, the battery cell achieves a matched lithium-ion dissociation rate, lithium-ion liquid-phase transport rate, lithium-ion liquid-solid transport rate, and lithium-ion solid-phase transport rate. Through the synergy between these steps, a balance is achieved between the battery cell's fast-charging performance and energy density.

[0008] In any embodiment, the mass ratio of ethylene carbonate to the chain carboxylic acid ester in the electrolyte is 0.26:1 to 1:1.

[0009] The mass ratio of ethylene carbonate to the chain carboxylic acid ester within the above range ensures that the electrolyte simultaneously possesses suitable viscosity, conductivity, good dissociation rate, and wettability, which is beneficial for improving the fast-charging performance of individual battery cells.

[0010] In any embodiment, the mass content of the chain carboxylic acid ester is 25.5%-63.75% based on the total mass of the electrolyte.

[0011] Electrolytes with a chain carboxylic acid ester content within the above range exhibit good conductivity, wettability, and chemical stability, which is beneficial for the comprehensive improvement of the fast-charging performance and cycle stability of battery cells.

[0012] In any embodiment, the chain carboxylic acid ester has the general structural formula R1-COO-R2, wherein R1 and R2 each independently comprise one or more of C1-C5 alkyl groups and C1-C5 haloalkyl groups.

[0013] In any embodiment, the chain carboxylic acid ester includes one or more of ethyl butyrate, ethyl propionate, ethyl acetate, methyl acetate, and methyl formate.

[0014] In any embodiment, based on the total mass of the electrolyte, the mass content of ethylene carbonate is 17%-34%.

[0015] Electrolytes with ethylene carbonate content within the above range exhibit good viscosity, dissociation rate, and conductivity, which are beneficial for comprehensively improving the fast-charging performance of individual battery cells.

[0016] In any embodiment, the lithium-containing electrolyte salt comprises lithium hexafluorophosphate (LiPF6).

[0017] In any embodiment, the lithium electrolyte salt further includes at least one of the fluorosulfonyl imide salts. Optionally, the fluorosulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide (LiFSI) and lithium bistrifluoromethanesulfonate (LiTFSI).

[0018] Fluorosulfonyl imide salts readily dissociate in electrolyte solvents, which helps improve the conductivity of the electrolyte. Furthermore, fluorosulfonyl imide salts exhibit high chemical stability and are not easily decomposed during cycling, thus reducing the generation of hydrogen fluoride during battery cycling, decreasing the probability of negative electrode side reactions, and improving the cycle stability of individual battery cells.

[0019] In any embodiment, the lithium-containing electrolyte salt comprises lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6), wherein the mass ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate (LiPF6) in the electrolyte is (2-5):10.

[0020] Battery cells with a mass ratio of lithium difluorosulfonyl imide to lithium hexafluorophosphate (LiPF6) in the electrolyte within the above-mentioned range can balance the fast-charging performance and safety performance of the battery cell.

[0021] In any embodiment, the battery cell further includes a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative active layer disposed on at least one side of the negative current collector, the negative active layer including a negative active material, the negative active material having a volume distribution particle size Dv10. 负 The micrometer range is 3.5μm-7.5μm, with an optional range of 4.5μm-6.5μm; Dv99 负 It ranges from 25μm to 35μm.

[0022] Dv10 负 and Dv99 负 The negative electrode active material within the above range includes a certain amount of small particles and large particles, so that the battery cell can improve the lithium-ion transport rate and fast charging performance through small particles, and improve the compaction density of the battery cell electrode through the gradation of large and small particles, thereby improving the energy density of the battery cell and achieving a balance between fast charging performance and energy density.

[0023] In any embodiment, the electrolyte further comprises additives, the additives comprising at least one of carbonate additives, sulfur-containing additives, and lithium salt additives, wherein the lithium salt additives comprise one or more of lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium tetrafluoroborate (LiBF4), and lithium dioxalate borate (LiBOB).

[0024] All of the above additives are film-forming additives, which can preferentially form films on the surface of the negative electrode active layer before the solvent and lithium-containing electrolyte salt in the electrolyte, thereby improving the electrochemical performance of the battery cell.

[0025] The SEI film component formed by carbonate additives is mainly composed of organic components and has excellent toughness, which can improve the cycle stability of battery cells; the SEI film component formed by sulfur-containing additives has excellent thermal and chemical stability, which can make up for the deficiencies of organic components and improve the storage performance of battery cells at high temperatures; lithium salt additives can reduce the problem of insufficient lithium ions at high charging rates and achieve lithium replenishment while improving the stability of the SEI film.

[0026] In any embodiment, the additive comprises at least two of the following: carbonate additives, sulfur-containing additives, and lithium salt additives.

[0027] The performance of battery cells under fast charging conditions is comprehensively improved by the interaction of two or more components in the additive.

[0028] In any embodiment, based on the total mass of the electrolyte, the additive accounts for 1% to 10% of the mass of the electrolyte, optionally 2% to 8%, and more preferably 3.5% to 8%.

[0029] In any embodiment, the carbonate additive includes one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0030] In any embodiment, the sulfur-containing additive includes one or more of vinyl sulfate DTD, 2-vinyl disulfate DTD, butenyl sulfite BS, 1,3-propanesulfonate lactone PS, vinyl sulfite ES, and methylene disulfonate MMDS.

[0031] In any embodiment, the additive includes vinylene carbonate (VC); based on the total mass of the electrolyte, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 9%, optionally 2% to 6%.

[0032] Chain carboxylic esters exhibit high reactivity, improving wettability between the electrolyte and the electrode, and enhancing electrolyte conductivity. However, they can also corrode the solid electrolyte interphase (SEI) membrane. Ethylene carbonate (VC) has a reduction potential similar to that of chain carboxylic esters, which can inhibit their reactivity and improve the cycle life of individual battery cells.

[0033] In any embodiment, the additive includes fluoroethylene carbonate (FEC); based on the total mass of the electrolyte, the mass content of FEC in the electrolyte is 0.1% to 4%, optionally 0.5% to 3%.

[0034] Excessive ethylene carbonate (VC) content leads to increased interfacial impedance and charge transfer impedance, negatively impacting the fast-charging performance of individual cells. Fluorinated ethylene carbonate (FEC) can also form a film on the negative electrode surface at higher potentials with lower interfacial impedance and charge transfer impedance; however, the SEI film formed by FEC has poor high-temperature stability, which is detrimental to the stability of individual cells under high-temperature environments. Adding both ethylene carbonate (VC) and fluoroethylene carbonate (FEC) to the electrolyte effectively balances the fast-charging performance and high-temperature stability of individual cells.

[0035] In any embodiment, the electrolyte comprises vinylene carbonate and fluoroethylene carbonate, wherein the total mass ratio of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) to the mass ratio of the chain carboxylic acid ester is 0.008-0.5.

[0036] Vinylene carbonate (VC) and fluoroethylene carbonate (FEC) work together to improve the corrosion of the SEI film by chain carboxylic acid esters in the electrolyte, effectively balancing the fast-charging performance and storage stability of the battery cell.

[0037] In any embodiment, the conductivity of the electrolyte is 14 mS / cm-20 mS / cm, and can be selected as 15 mS / cm-20 mS / cm.

[0038] Electrolytes with conductivity within the above range can better balance the fast-charging performance and cycle life of individual battery cells.

[0039] In any embodiment, the density of the positive electrode active layer on one side is 280 mg / 1540.25 mm². 2 ~370mg / 1540.25mm 2 .

[0040] A positive electrode active layer with a single-sided density within the above range can more effectively balance the fast-charging performance and energy density of the battery cell.

[0041] In any embodiment, the compaction density of the positive electrode active layer at 100% SOC of the battery cell is 2.50 g / cm³. 3 ~2.80g / cm 3 ; 2.55g / cm³ is optional 3 ~2.68g / cm 3 .

[0042] When a battery cell is at 100% SOC, a positive electrode active layer with a compaction density within the above range can achieve a balance between the fast-charging performance and energy density of the battery cell.

[0043] In any embodiment, the lithium-containing phosphate is a lithium-containing phosphate with an olivine structure, comprising the components shown in Formula I, Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula I,

[0044] Wherein, 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.7≤x1+y1≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, and 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z1≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0045] The lithium phosphate with the above-mentioned components and olivine structure has good structural stability, which can reduce losses during fast charging and improve the cycle stability of battery cells.

[0046] In any embodiment, the positive electrode active material further includes an ion-conducting layer disposed on the surface of the lithium phosphate, the ion-conducting layer comprising carbon elements, wherein the mass percentage of carbon elements is 1% to 2% based on the total mass of the positive electrode active material.

[0047] The aforementioned carbon-containing ion-conducting layer can simultaneously improve the ion conductivity and electrical conductivity of the positive electrode active material, enhance the solid-phase transport rate of ions and electrons, and improve the energy density and fast-charging performance of the battery cell.

[0048] In any embodiment, the ion-conducting layer further comprises a fast ion conductor having a NASICON structure as shown in Formula II.

[0049] Li 3-b2 Fe 2-b2 M2 b2 (PO x2 ) y2 Formula II,

[0050] In Equation II, M2 is selected from one or more of Ti, Zr, Hf, Ge and Sn with a +4 valence, 0≤b2≤1, 3≤x2≤5, and 2≤y2≤4.

[0051] Fast ion conductors with a NASICON structure possess abundant three-dimensional lithium-ion diffusion and transport channels, exhibiting advantages such as high ion conductivity and strong structural stability during multiple lithium delithiation and intercalation processes. Coating the surface of lithium phosphate with a fast ion conductor containing a NASICON structure can significantly improve the lithium-ion transport rate during multiple lithium delithiation / intercalation at the positive electrode, enhance the ionic conductivity of the positive electrode active material, and improve the energy density and fast-charging performance of the corresponding battery cell.

[0052] In any embodiment, the fast ion conductor includes one or more of Li2FeTi(PO4)3, Li2FeZr(PO4)3, and Li2FeSn(PO4)3.

[0053] In any embodiment, the compacted density of the positive electrode active material under a pressure of 30,000 N is greater than or equal to 2.46 g / cm³. 3 The option is 2.46 g / cm³. 3 -2.8g / cm 3 .

[0054] In any embodiment, the volume average particle size of the positive electrode active material satisfies: 1μm≤Dv50 正 ≤2μm, 0.4μm≤Dv10 正 ≤0.7μm.

[0055] The aforementioned positive electrode active material effectively improves the compaction density of the powder and the carrier conduction between positive electrode active materials through particle size gradation, which is beneficial to balancing the energy density and fast charging performance of the battery cell.

[0056] In any embodiment, the powder resistivity R of the positive electrode active material is ≤27.5Ω·cm.

[0057] In any embodiment, the specific surface area S of the positive electrode active material is 5m². 2 / g~18m 2 / g.

[0058] The carbon structure in the positive electrode active layer is highly correlated. Positive electrode active materials with powder resistivity and specific surface area within the above range have both good ion conductivity and electronic conductivity, which is beneficial to improving the fast charging performance of battery cells.

[0059] In any embodiment, the positive electrode active layer includes a lithium replenishing agent, which includes at least one of ternary lithium replenishing materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, and lithium trilithium citrate.

[0060] Adding lithium replenishing agents to the positive electrode active layer can counteract irreversible lithium loss during electrochemical processes, thereby increasing the total capacity and energy density of the battery cell.

[0061] In any embodiment, the general formula of the ternary lithium supplement material is shown in Formula III.

[0062] Li x3 A y3 Ni a3 Co b3 Mn c3 M3(1-a3-b3-c3)Y z3 Formula III

[0063] Wherein, 0≤x³≤2.1, 0≤y³≤2.1, and 0.9≤x³+y³≤2.1; 0≤a³≤1, 0≤b³≤1, 0≤c³≤1, and 0.1≤a³+b³+c³≤1; 1.8≤z³≤3.5; A includes one or more of Na, K, and Mg; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; Y includes one or more of O and F.

[0064] In any embodiment, the lithium supplement agent is added to the positive electrode film layer at a mass content of 0.1% to 10%.

[0065] In any embodiment, the positive electrode includes a positive conductive layer disposed between the positive current collector and the positive active layer, and the thickness of the positive conductive layer is 0.5 μm to 2 μm; and / or the negative electrode includes a negative conductive layer disposed between the negative current collector and the negative active layer, and the thickness of the negative conductive layer is 0.5 μm to 2 μm.

[0066] The addition of a positive electrode conductive layer and / or a negative electrode conductive layer is beneficial to improving the electronic conductivity of the battery cell electrode and thus improving the energy density of the battery cell.

[0067] In any embodiment, the positive electrode conductive layer includes a conductive agent and a first binder, and the negative electrode conductive layer includes a conductive agent and a second binder. The conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Optionally, the conductive agent includes superconducting carbon and carbon nanotubes. The first binder includes a fluorinated binder, and the second binder includes a water-soluble binder.

[0068] In any embodiment, based on the total mass of the positive conductive layer, the mass content of the conductive agent in the positive conductive layer is 30% to 50%, and the mass content of the first binder is 50% to 70%; and / or based on the total mass of the negative conductive layer, the mass content of the conductive agent in the negative conductive layer is 20% to 40%, and the mass content of the second binder is 60% to 80%.

[0069] In any embodiment, the density of the negative electrode active layer on one side is 104 mg / 1540.25 mm². 2 -180mg / 1540.25mm 2 ; 125mg / 1540.25mm is optional. 2 -167mg / 1540.25mm 2 .

[0070] A negative electrode active layer with a single-sided surface density within the above range can cooperate with a positive electrode active layer to achieve a balance between battery cell energy density and fast charging performance.

[0071] In any embodiment, at 100% SOC, the compaction density of the negative electrode active layer is 1.15 g / cm³. 3 ~1.36g / cm 3 ; 1.25g / cm³ is optional 3 ~1.36g / cm 3 .

[0072] In any embodiment, the negative electrode active material includes graphite.

[0073] In any embodiment, the graphite includes composite graphite particles, the composite graphite particles include bulk particles and a coating layer at least partially disposed on the surface of the bulk particles, the bulk particles include artificial graphite, the coating layer includes amorphous carbon, and the composite graphite particles include secondary particles.

[0074] Composite graphite particles, including secondary particles and surface coatings including amorphous carbon, are beneficial for the wetting of electrolyte in the negative electrode active layer of the electrode, which helps to improve the rate performance of the battery cell.

[0075] In any embodiment, based on the total mass of the composite graphite particles, the mass content of amorphous carbon in the coating layer of the composite graphite particles is 2% to 5%.

[0076] When the content of amorphous carbon is within a suitable range, composite graphite materials can have both high specific capacity and high active ion solid-phase transport capability, which is beneficial to improving the fast charging performance of battery cells.

[0077] In any embodiment, the powder resistivity of the negative electrode active material is less than or equal to 0.04 Ω·cm.

[0078] In any embodiment, the compacted density of the negative electrode active material under a pressure of 20000N is 1.5 g / cm³. 3 Up to 1.7 g / cm 3 1.55g / cm³ is an optional value. 3 Up to 1.65 g / cm 3 .

[0079] Anode active materials with a powder compaction density within a suitable range can enable the anode active layer to have a high compaction density, thereby enabling the battery cell to have a high energy density; at the same time, the anode active layer can maintain its original pore structure during cycling, which is beneficial to improving the high-fast charging performance of the battery cell during cycling.

[0080] In any embodiment, the negative electrode active material further includes a silicon-based material, which includes at least one of silicon, silicon oxide, and silicon-carbon composite; based on the total mass of the negative electrode active material, the mass content of silicon element in the silicon-based material is 0.3% to 10%, optionally 1% to 6%.

[0081] The introduction of silicon-based materials is beneficial for improving the energy density of individual battery cells. Silicon-based materials within the aforementioned mass range can balance the energy density and cycle stability of individual battery cells.

[0082] In some embodiments, the charge capacity of the negative electrode active material is from 350 mAh / g to 480 mAh / g.

[0083] Negative electrode active materials with a charge capacity within the above range are beneficial to improving the energy density of battery cells.

[0084] In any embodiment, the negative electrode active layer includes a first negative electrode active material layer disposed on the surface of the negative electrode current collector and a second negative electrode active material layer disposed on the side of the first negative electrode active material layer away from the negative electrode current collector, wherein the second negative electrode active material layer includes composite graphite particles.

[0085] In any embodiment, the first negative electrode active material layer includes one or more of composite graphite particles and natural graphite.

[0086] Placing composite graphite particles close to the electrolyte side can improve the fast-charging performance of individual battery cells while maintaining energy density.

[0087] In any embodiment, the thickness ratio of the second negative electrode active material layer to the thickness of the first negative electrode active material layer is 3:7 to 7:3.

[0088] In any embodiment, the volume average particle size Dv501 of the negative electrode active material in the first negative electrode active material layer is 9.5 μm to 18.5 μm, and can be selected as 9.5 μm to 14.8 μm.

[0089] In any embodiment, the volume average particle size Dv502 of the negative electrode active material in the second negative electrode active layer is 7.8 μm to 14.3 μm, and can be selected as 7.8 μm to 12.8 μm.

[0090] The second negative electrode active material layer disposed on the electrolyte side includes negative electrode active materials with smaller particle size, which can further improve the solid-liquid transport rate of ions in the battery electrode and improve the fast charging performance of the battery cell.

[0091] In any embodiment, the battery cell further includes a separator, the separator comprising a porous base film and a functional layer disposed on at least one side of the porous base film, the thickness of the porous base film being less than or equal to 12 μm, optionally less than or equal to 9 μm.

[0092] In any embodiment, the porosity of the porous base membrane in the isolation membrane is 20%-70%, optionally 35%-60%.

[0093] In any embodiment, the functional layer includes a first functional layer disposed on the negative electrode side of the porous base membrane and a second functional layer disposed on the positive electrode side of the porous base membrane. The first functional layer includes first inorganic particles, and the second functional layer includes composite particles. The composite particles include second inorganic particles and a non-fluoropolymer. The second inorganic particles in the composite particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

[0094] Inorganic particles can improve the heat resistance of the first and second functional layers and enhance the fast-charging performance of individual battery cells.

[0095] In any embodiment, the non-fluoropolymer particles comprise acrylate copolymers.

[0096] In any embodiment, the electrolyte injection coefficient of the battery cell is 2.4 g / Ah-3.1 g / Ah.

[0097] Within the above-mentioned range, the electrolyte injection coefficient can improve the cycle stability of individual battery cells.

[0098] In any embodiment, the battery cell further includes an electrode terminal, and the electrode assembly includes a tab portion, which is directly welded to the electrode terminal.

[0099] In any embodiment, the time for the battery cell to be charged from 10% state of charge (SOC) to 80% state of charge (SOC) at 30°C is 6 min to 15 min.

[0100] This battery cell has excellent fast-charging performance, which can meet the needs of improving the energy replenishment efficiency of electrical devices.

[0101] In any embodiment, the battery cell has a wound structure, the thickness of the positive current collector is less than or equal to 15 μm, and the thickness of the negative current collector is less than or equal to 6 μm.

[0102] The positive electrode current collector and / or negative electrode current collector have a lower thickness, which enables a further increase in the energy density of the battery cell.

[0103] In any embodiment, the volumetric energy density of the battery cell is 400Wh / L to 500Wh / L.

[0104] This battery cell also has high energy density, which can meet the needs of increasing the driving range of electrical devices.

[0105] The second aspect of this application provides a battery device including the battery cell provided in the first aspect of this application, the battery device including at least one of a battery module, a battery pack, and an energy storage battery.

[0106] A third aspect of this application also provides an electrical device, which includes the battery cell provided in the first aspect of this application. Attached Figure Description

[0107] Figure 1 is a schematic diagram of a battery cell according to one embodiment of this application.

[0108] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1.

[0109] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0110] Figure 4 is a schematic diagram of a battery pack according to one embodiment of this application.

[0111] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0112] Figure 6 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0113] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0114] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0115] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0116] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0117] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0118] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0119] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0120] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0121] Fast charging technology aims to shorten the time required for battery charging, primarily by increasing the charging current and charging rate to achieve rapid insertion / extraction of active ions in the active material layer. High-energy-density batteries typically have a high areal density in their active material layer, but this high areal density affects the insertion / extraction rate of active ions within the battery cell, thus reducing the fast-charging performance of the individual cell. Therefore, the fast-charging performance and energy density of a battery cell are often a difficult trade-off to achieve simultaneously.

[0122] Based on this, a first aspect of this application provides a battery cell, including a positive electrode sheet and an electrolyte; the positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, the positive active layer includes a positive active material, the positive active material includes lithium phosphate, and the one-sided lateral density of the positive active layer is 230 mg / 1540.25 mm². 2 ~400mg / 1540.25mm 2 The electrolyte comprises a solvent and a lithium-containing electrolyte salt. The solvent includes chain carboxylic acid esters and ethylene carbonate. The lithium-containing electrolyte salt includes one or more of lithium hexafluorophosphate and fluorosulfonyl imide salts. The mass ratio of the lithium-containing electrolyte salt to ethylene carbonate is 0.29-0.72. The conductivity of the electrolyte is 13 mS / cm-20 mS / cm.

[0123] In this application, "one-sided density of the positive electrode active layer" refers to the mass of the positive electrode active layer per unit area on the current collector side.

[0124] In this application, the unilateral density of the positive electrode active layer can be tested using methods known in the art. For example, a positive electrode sheet coated on one side and cold-pressed (if it is a double-sided coated positive electrode sheet, the positive electrode active layer on one side can be wiped off first) can be cut into small circular pieces with an area of ​​S1, and its mass can be weighed and recorded as M1. Then, the positive electrode film layer of the weighed positive electrode sheet can be wiped off, and the mass of the positive electrode current collector can be weighed and recorded as M0. The unilateral density of the positive electrode sheet = (M1-M0) / S1.

[0125] In some embodiments, the density of the positive electrode active layer on one side can be selected as 230 mg / 1540.25 mm. 2 240mg / 1540.25mm 2 250mg / 1540.25mm 2 260mg / 1540.25mm 2 270mg / 1540.25mm 2 280mg / 1540.25mm 2 290mg / 1540.25mm 2 300mg / 1540.25mm 2 310mg / 1540.25mm 2 325mg / 1540.25mm 2 340mg / 1540.25mm 2 350mg / 1540.25mm 2 360mg / 1540.25mm 2 375mg / 1540.25mm 2 400mg / 1540.25mm 2 Or the range of values ​​between any two.

[0126] Lithium-containing phosphates are active materials with an olivine structure comprising lithium ions and phosphate groups. The types of positive electrode active materials can be tested using any method known in the art. As an example, phase analysis methods such as X-ray diffraction (XRD) combined with elemental analysis methods such as energy dispersive spectroscopy (EDS) can be used for analysis.

[0127] The types and quality of solvents and lithium-containing electrolyte salts in the electrolyte can be obtained by methods known to those skilled in the art. For example, the composition of the electrolyte can be determined by liquid chromatography, ultraviolet spectrophotometry, or ultraviolet-visible spectrophotometry. For instance, a battery cell is disassembled, and free electrolyte is obtained from it. The free electrolyte in the battery cell is diluted 3 to 10 times with acetonitrile to obtain a diluted electrolyte solution to be tested. Using a GC-MS 3100 organic component gas chromatograph, the above diluted electrolyte solution is placed in the instrument for full-scan qualitative analysis. The injection port temperature is 250°C, and the scan range is 35 μm to 270 μm. After the test, a total ion chromatogram of each organic compound is obtained. The peak positions in the chromatograms are compared with the corresponding organic compounds, and the percentage content of each organic compound is calculated based on the peak area. For example, an ion chromatograph (IC) can be used to test the content of inorganic substances in the electrolyte. A quantitative amount of electrolyte (the concentration of the diluent is in the middle of the standard curve) is weighed and diluted to 100 mL with ultrapure water. The ion chromatograph automatically injects the sample for detection and tests the ion chromatogram of inorganic substances. The corresponding inorganic substances are identified by comparing the peak positions in the chromatogram.

[0128] In some embodiments, the mass ratio of lithium electrolyte salt to ethylene carbonate can be selected as 0.29, 0.31, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.72 or any range between the two.

[0129] The conductivity of an electrolyte describes the ability of the positive and negative ions dissociated from the electrolyte solution to conduct electricity through the directional movement of these ions in an electric field. It can be tested using any method known in the art. As an example, approximately 100 mL of electrolyte sample is taken in a dry, clean, corrosion-resistant sample bottle, sealed, and placed in a constant-temperature water bath. The sample is shaken periodically, and the temperature is maintained at 25°C (with a deviation of ±5°C). After the sample temperature stabilizes, its conductivity is tested using a commercially available conductivity meter. The conductivity meter is thoroughly dried with calibration solution, vertically immersed in the liquid to be tested, and the test is started. The test result is recorded after the data has stabilized for at least 10 seconds.

[0130] In some embodiments, the conductivity of the electrolyte can be selected as 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, 17 mS / cm, 18 mS / cm, 19 mS / cm, 20 mS / cm, 21 mS / cm, 22 mS / cm, 23 mS / cm, 24 mS / cm, 25 mS / cm, or any value between the two.

[0131] In the electrolyte, ethylene carbonate readily forms a solvation structure with lithium ions in the lithium-containing electrolyte salt, thereby increasing the dissociation rate of lithium ions and anions in the electrolyte salt. However, with the increase of ethylene carbonate content, the electrolyte viscosity also increases, negatively impacting the electrolyte conductivity. Chain-like carboxylic esters, on the other hand, can improve the wettability between the electrolyte and the electrode, enhancing the solid-liquid transport rate of lithium ions between them. The addition of chain-like carboxylic esters also contributes to improving the electrolyte conductivity. Lithium-phosphate cathode electrodes with a single-sided lateral density within the aforementioned range possess both high lithium-ion solid-phase transport rates and high positive electrode active material loading. By combining these electrolytes, the battery cell achieves a matched lithium-ion dissociation rate, lithium-ion liquid-phase transport rate, lithium-ion liquid-solid transport rate, and lithium-ion solid-phase transport rate. Through the synergy between these steps, a balance is achieved between the battery cell's fast-charging performance and energy density.

[0132] In some embodiments, the mass ratio of ethylene carbonate to the chain carboxylic acid ester in the electrolyte is 0.26:1 to 1:1.

[0133] In some embodiments, the mass ratio of ethylene carbonate to the chain carboxylic acid ester in the electrolyte may be selected as 0.26:1, 0.30:1, 0.36:1, 0.40:1, 0.46:1, 0.50:1, 0.56:1, 0.60:1, 0.66:1, 0.70:1, 0.76:1, 0.80:1, 0.86:1, 0.90:1, 0.96:1, 1:1, or any range between the two.

[0134] The mass ratio of ethylene carbonate to the chain carboxylic acid ester within the above range ensures that the electrolyte simultaneously possesses suitable viscosity, conductivity, good dissociation rate, and wettability, which is beneficial for improving the fast-charging performance of individual battery cells.

[0135] In some embodiments, the chain carboxylic acid ester accounts for 25.5%-63.75% of the total mass of the electrolyte.

[0136] In some embodiments, based on the total mass of the electrolyte, the mass content of the chain carboxylic acid ester can be selected as 25.5%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 63.75%, or any range between the two.

[0137] Electrolytes with a chain carboxylic acid ester content within the above range exhibit good conductivity, wettability, and chemical stability, which is beneficial for the comprehensive improvement of the fast-charging performance and cycle stability of battery cells.

[0138] In some embodiments, the chain carboxylic acid ester has the general structural formula R1-COO-R2, wherein R1 and R2 each independently comprise one or more of C1-C5 alkyl groups and C1-C5 haloalkyl groups.

[0139] "C1-C5 alkyl" refers to unbranched or branched alkyl groups having 1-5 carbon atoms; including but not limited to one or more of methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, and 1-ethylpropyl.

[0140] "C1 to C5 haloalkyl" refers to an unbranched or branched alkyl group having 1 to 5 carbon atoms in which at least one hydrogen atom is replaced by a halogen, including but not limited to one or more of chloroalkyl, bromoalkyl, and iodoalkyl.

[0141] In some embodiments, the chain carboxylic acid ester includes one or more of ethyl butyrate, ethyl propionate, ethyl acetate, methyl acetate, and methyl formate.

[0142] In some embodiments, the mass content of ethylene carbonate is 17%-34% based on the total mass of the electrolyte.

[0143] In some embodiments, based on the total mass of the electrolyte, the mass content of ethylene carbonate can be selected as 17%, 18%, 19%, 20%, 25%, 30%, 34%, or any value range between the two.

[0144] Electrolytes with ethylene carbonate content within the above range exhibit good viscosity, dissociation rate, and conductivity, which are beneficial for comprehensively improving the fast-charging performance of individual battery cells.

[0145] In some embodiments, the lithium-containing electrolyte salt includes lithium hexafluorophosphate (LiPF6).

[0146] In some embodiments, the lithium electrolyte salt further includes at least one of fluorosulfonyl imide salts. Optionally, the fluorosulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide (LiFSI) and lithium bistrifluoromethanesulfonate (LiTFSI).

[0147] Fluorosulfonyl imide salts readily dissociate in electrolyte solvents, which is beneficial for improving electrolyte conductivity. Furthermore, fluorosulfonyl imide salts exhibit high chemical stability and are not prone to decomposition during cycling, reducing hydrogen fluoride generation during battery cycling, decreasing the probability of negative electrode side reactions, and improving the cycle stability of individual battery cells. However, as the temperature of the battery cell increases, fluorosulfonyl imide salts undergo violent decomposition at a certain temperature threshold, releasing a large amount of heat and drastically increasing the risk of thermal runaway. This safety risk is even more pronounced in fast-charging batteries. Although lithium hexafluorophosphate gradually decomposes to produce hydrofluoric acid during secondary cycling, the addition of lithium hexafluorophosphate significantly reduces the risk of thermal runaway in individual battery cells, keeping the risk within a controllable range and improving battery safety.

[0148] In some embodiments, the lithium-containing electrolyte salt comprises lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6), wherein the mass ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate (LiPF6) in the electrolyte is (2-5):10.

[0149] In some embodiments, the mass ratio of lithium difluorosulfonylimide to lithium hexafluorophosphate (LiPF6) in the electrolyte can be selected as 2:10, 3:10, 4:10, 5:10, or any range between the two.

[0150] Battery cells with a mass ratio of lithium difluorosulfonyl imide to lithium hexafluorophosphate (LiPF6) in the electrolyte within the above-mentioned range can balance the fast-charging performance and safety performance of the battery cell.

[0151] In some embodiments, the battery cell further includes a negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative active layer disposed on at least one side of the negative current collector, the negative active layer comprising a negative active material, the negative active material having a volume distribution particle size Dv10. 负 The micrometer range is 3.5μm-7.5μm, with an optional range of 4.5μm-6.5μm; Dv99 负 It ranges from 25μm to 35μm.

[0152] Volume distribution particle size Dv10 of negative electrode active material 负 Dv99 负As is known in the art, these terms represent the particle size corresponding to a cumulative volume distribution percentage of 10% and 99%, respectively, and can be determined using instruments and methods known in the art. For example, they can be conveniently determined using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK. The negative electrode active material can be freshly prepared negative electrode active material or obtained by scraping powder from the negative electrode active layer after disassembling a secondary battery.

[0153] In some embodiments, the volume distribution particle size Dv10 of the negative electrode active material 负 The value can be selected as 3.5μm, 4.5μm, 5.5μm, 6.5μm, 7.5μm or any value range between the two.

[0154] In some embodiments, the volume distribution particle size Dv99 of the negative electrode active material 负 The value can be selected as 25μm, 27μm, 30μm, 32μm, 35μm or any range between the two.

[0155] Dv10 负 and Dv99 负 The negative electrode active material within the above range includes a certain amount of small particles and large particles, so that the battery cell can improve the lithium-ion transport rate and fast charging performance through small particles, and improve the compaction density of the battery cell electrode through the gradation of large and small particles, thereby improving the energy density of the battery cell and achieving a balance between fast charging performance and energy density.

[0156] In some embodiments, the electrolyte further comprises additives, which include at least one of carbonate additives, sulfur-containing additives, and lithium salt additives. The lithium salt additives include one or more of lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium tetrafluoroborate (LiBF4), and lithium dioxalate borate (LiBOB).

[0157] Additives refer to components present in low concentrations in the electrolyte, typically accounting for no more than 10% of the electrolyte's mass. They are characterized by their targeted nature and small dosage, allowing for significant optimization of a specific aspect of battery performance without altering the manufacturing process. The composition of additives can be determined using any method known in the art. For example, the composition of the electrolyte can be measured using liquid chromatography, ultraviolet spectrophotometry, or ultraviolet-visible spectrophotometry. Exemplarily, an ion chromatograph (IC) can be used to test the inorganic content in the electrolyte. A quantitative amount of electrolyte (with a dilution concentration at the midpoint of the standard curve) is weighed, and the volume is adjusted to 100 mL with ultrapure water. The ion chromatogram is automatically injected and detected, and the inorganic ion chromatogram is analyzed. The peak positions are then compared to identify the corresponding inorganic compounds. The above free electrolyte was diluted 3 to 10 times with acetonitrile to obtain the electrolyte dilution to be tested. The electrolyte dilution was placed in a GC-MS 3100 organic component gas chromatograph for full scan qualitative analysis. The injection port temperature was 250℃, and the scan range was 35μm to 270μm. After the test was completed, the total ion chromatogram of each organic compound was obtained. The corresponding organic compound type was determined by comparing the peak positions in the chromatogram.

[0158] All of the above additives are film-forming additives, which can preferentially form films on the surface of the negative electrode active layer before the solvent and lithium-containing electrolyte salt in the electrolyte, thereby improving the electrochemical performance of the battery cell.

[0159] In some embodiments, the additive comprises at least two of the following: carbonate additives, sulfur-containing additives, and lithium salt additives.

[0160] The SEI film component formed by carbonate additives is mainly composed of organic components, which has excellent toughness and can improve the cycle stability of battery cells. The SEI film component formed by sulfur-containing additives has excellent thermal and chemical stability, which can make up for the deficiencies of organic components and improve the storage performance of battery cells at high temperatures. Lithium salt additives can reduce the problem of insufficient lithium ions under high-rate charging speeds, and achieve lithium replenishment while improving the stability of the SEI film. Through the interaction of two or more of these components, the performance of battery cells under fast charging conditions is comprehensively improved.

[0161] In some embodiments, the additive accounts for 1% to 10% of the total mass of the electrolyte, optionally 2% to 8%, and more preferably 3.5% to 8%.

[0162] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the additive in the electrolyte can be selected as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any value range between the two.

[0163] Based on the total mass of the electrolyte, the mass percentage of the additive in the electrolyte can be determined using any method known in the art. For example, the method described above for testing the mass of solvent and lithium-containing electrolyte salt in the electrolyte can be used. It should be understood that, due to the consumption of additives in the electrolyte during formation and cycling, resulting in the formation of components in the SEI film, the mass percentage of the additive in the electrolyte may be slightly lower than the initial mass percentage of the additive added to the electrolyte.

[0164] In some embodiments, the carbonate additive includes one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0165] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butenyl sulfite BS, 1,3-propanesulfonate lactone PS, vinyl sulfite ES, and methylene disulfonate MMDS.

[0166] In some embodiments, the additive includes vinylene carbonate (VC); the mass content of VC in the electrolyte is 0.5% to 9% based on the total mass of the electrolyte, optionally 2% to 6%.

[0167] In some embodiments, based on the total mass of the electrolyte, the mass content percentage of vinylene carbonate (VC) in the electrolyte can be selected as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, or any value range between the two.

[0168] Chain carboxylic esters exhibit high reactivity, improving wettability between the electrolyte and the electrode, and enhancing electrolyte conductivity. However, they can also corrode the solid electrolyte interphase (SEI) membrane. Ethylene carbonate (VC) has a reduction potential similar to that of chain carboxylic esters, which can inhibit their reactivity and improve the cycle life of individual battery cells.

[0169] In some embodiments, the additive includes fluoroethylene carbonate (FEC); based on the total mass of the electrolyte, the mass content of FEC in the electrolyte is 0.1% to 4%, optionally 0.5% to 3%.

[0170] In some embodiments, based on the total mass of the electrolyte, the mass content percentage of fluoroethylene carbonate (FEC) in the electrolyte can be selected as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or any value range between the two.

[0171] Excessive ethylene carbonate (VC) content leads to increased interfacial impedance and charge transfer impedance, negatively impacting the fast-charging performance of individual cells. Fluorinated ethylene carbonate (FEC) can also form a film on the negative electrode surface at higher potentials with lower interfacial impedance and charge transfer impedance; however, the SEI film formed by FEC has poor high-temperature stability, which is detrimental to the stability of individual cells under high-temperature environments. Adding both ethylene carbonate (VC) and fluoroethylene carbonate (FEC) to the electrolyte effectively balances the fast-charging performance and high-temperature stability of individual cells.

[0172] In some embodiments, the electrolyte comprises vinylene carbonate and fluoroethylene carbonate, wherein the total mass ratio of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) to the mass ratio of the chain carboxylic acid ester is 0.008-0.5.

[0173] In some embodiments, the ratio of the total mass of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) in the electrolyte to the mass of the chain carboxylic acid ester can be selected as 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, or any value range between the two.

[0174] Vinylene carbonate (VC) and fluoroethylene carbonate (FEC) work together to improve the corrosion of the SEI film by chain carboxylic acid esters in the electrolyte, effectively balancing the fast-charging performance and storage stability of the battery cell.

[0175] In some embodiments, the conductivity of the electrolyte is 14 mS / cm-20 mS / cm, and optionally 15 mS / cm-20 mS / cm.

[0176] Electrolytes with conductivity within the above range can better balance the fast-charging performance and cycle life of individual battery cells.

[0177] In some embodiments, the one-sided surface density of the positive electrode active layer is 280 mg / 1540.25 mm². 2~370mg / 1540.25mm 2 .

[0178] A positive electrode active layer with a single-sided density within the above range can more effectively balance the fast-charging performance and energy density of the battery cell.

[0179] In some embodiments, the compaction density of the positive electrode active layer at 100% SOC of the battery cell is 2.50 g / cm³. 3 ~2.80g / cm 3 ; 2.55g / cm³ is optional 3 ~2.68g / cm 3 .

[0180] In some embodiments, the compaction density of the positive electrode active layer at 100% SOC of the battery cell can be selected as 2.50 g / cm³. 3 2.55g / cm 3 2.60g / cm 3 2.68g / cm 3 2.70 g / cm 3 2.75g / cm 3 2.80g / cm 3 Or the range of values ​​between any two.

[0181] In this application, the compaction density of the positive electrode active layer at 100% SOC of the battery cell has a meaning known in the art and can be tested using methods known in the art. For example, the battery cell is charged to the cutoff voltage (e.g., 3.65V) at a constant current charging rate of 0.33C, left to stand for 1 minute, and then charged to the cutoff voltage again at a constant current charging rate of 0.1C. At this point, the battery cell is at 100% SOC. Then, the positive electrode is disassembled, and the compaction density of the positive electrode active layer is measured. The compaction density of the positive electrode active layer is the areal density of the positive electrode active layer measured after disassembly divided by the thickness of the positive electrode active layer. The areal density of the positive electrode active layer can be tested using the methods mentioned above. The thickness of the positive electrode active layer has a meaning known in the art and can be tested using methods known in the art, such as using a micrometer (e.g., a Mitutoyo 293-100 model with an accuracy of 0.1μm). It is understood that when the battery cell is at 100% SOC, the compaction density of the positive electrode active layer is different from the design value of the battery cell compaction density. Due to the influence of actual operation, when the battery cell is at 100% SOC, the compaction density of the positive electrode active layer is often slightly lower than the design value of the battery cell compaction density.

[0182] When a battery cell is at 100% SOC, a positive electrode active layer with a compaction density within the above range can achieve a balance between the fast-charging performance and energy density of the battery cell.

[0183] In some embodiments, the lithium-containing phosphate is a lithium-containing phosphate with an olivine structure, comprising components as shown in Formula I, Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula I,

[0184] Wherein, 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.7≤x1+y1≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, and 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z1≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0185] In some implementations, x1 can be selected as 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, or any value range between two of these; y1 can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, or any value range between two of these; x1+y1 can be selected as 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, or any value range between two of these; and a1 can be selected as 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, or any value range between two of these. b1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any value between two of them; a1+b1 can be selected from 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any value between two of them; c1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any value between two of them; z1 can be selected from 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or any value between two of them.

[0186] The lithium phosphate with the above-mentioned components and olivine structure has good structural stability, which can reduce losses during fast charging and improve the cycle stability of battery cells.

[0187] In some embodiments, the positive electrode active material further includes an ion-conducting layer disposed on the surface of the lithium phosphate, the ion-conducting layer comprising carbon elements, wherein the mass percentage of carbon elements is 1% to 2% based on the total mass of the positive electrode active material.

[0188] In some embodiments, the mass percentage of carbon element, based on the total mass of the positive electrode active material, can be selected as 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any value range between the two.

[0189] It should be noted that the ion-conducting layer can be a single-layer structure or a multi-layer structure. That is, the ion-conducting component and the carbon-containing component in the ion-conducting layer can be a mixed phase or be arranged in layers. It is understandable that the ion-conducting layer has a high ion transport rate.

[0190] The aforementioned carbon-containing ion-conducting layer can simultaneously improve the ion conductivity and electrical conductivity of the positive electrode active material, enhance the solid-phase transport rate of ions and electrons, and improve the energy density and fast-charging performance of the battery cell.

[0191] In some embodiments, the ion-conducting layer further comprises a fast ion conductor having a NASICON structure as shown in Formula II.

[0192] Li 3-b2 Fe 2-b2 M2 b2 (PO x2 ) y2 Formula II,

[0193] In Equation II, M2 is selected from one or more of Ti, Zr, Hf, Ge and Sn with a +4 valence, 0≤b2≤1, 3≤x2≤5, and 2≤y2≤4.

[0194] In some implementations, b2 can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or any value range between two of them; x2 can be selected as 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, or any value range between two of them; and y2 can be selected as 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, or any value range between two of them.

[0195] The phase structure in the ion-conducting layer can be characterized by any known method in the art. For example, by characterizing the positive electrode active material by transmission electron microscopy, it can be seen that the ion-conducting layer and the matrix of the positive electrode active material have different phase structures. Combined with diffraction patterns and energy dispersive spectroscopy analysis, the fast ion conductor component of the ion-conducting layer can be determined.

[0196] Fast ion conductors, also known as superionic conductors and solid electrolytes, refer to solids whose ionic conductivity is close to or exceeds that of conductive liquids such as electrolyte solutions or molten salts. Fast ion conductors with a NASICON structure possess abundant three-dimensional lithium-ion diffusion and transport channels, exhibiting advantages such as high ion conductivity and strong structural stability during multiple lithium delithiation and intercalation processes. Coating the surface of lithium phosphate with fast ion conductors containing a NASICON structure can significantly improve the lithium-ion transport rate during multiple lithium delithiation / intercalation at the positive electrode, enhance the ionic conductivity of the positive electrode active material, and improve the energy density and fast-charging performance of the corresponding battery cells.

[0197] In some embodiments, the fast ion conductor includes one or more of Li2FeTi(PO4)3, Li2FeZr(PO4)3, and Li2FeSn(PO4)3.

[0198] In some embodiments, the compacted density of the positive electrode active material at a pressure of 30,000 N is greater than or equal to 2.46 g / cm³. 3 The option is 2.46 g / cm³. 3 -2.8g / cm 3 .

[0199] In this application, the compacted density of the positive electrode active material powder has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined by referring to GB / T 24533-2009 using an electronic pressure testing machine (e.g., a UTM7305 electronic pressure testing machine). An exemplary test method is as follows: Weigh 1g of positive electrode active material powder and add it to a container with a bottom area of ​​1.327cm². 2 In the mold, the pressure is increased to 30000N, held for 30s, then depressurized and held for 10s. The compaction density of the material under 30000N pressure is then recorded and calculated.

[0200] In some embodiments, the compacted density of the positive electrode active material at a pressure of 30,000 N can be selected as 2.46 g / cm³. 3 2.47 g / cm 3 2.48 g / cm 3 2.49 g / cm 3 2.5g / cm 3 2.55g / cm 32.6g / cm 3 2.65g / cm 3 2.7g / cm 3 2.75g / cm 3 2.8g / cm 3 Or the range of values ​​between any two.

[0201] In some embodiments, the volume average particle size of the positive electrode active material satisfies: 1 μm ≤ Dv50 正 ≤2μm, 0.4μm≤Dv10 正 ≤0.7μm.

[0202] In some embodiments, the volume average particle size Dv50 of the positive electrode active material 正 The selectable value is 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, or any value range between two of these. (Dv10) 正 The value can be selected as 0.4μm, 0.5μm, 0.6μm, 0.7μm or any value range between the two.

[0203] Volume average particle size Dv50 of positive electrode active material 正、 Dv10 正 The same test method as that used for the volume average particle size of the negative electrode active material described above can be used.

[0204] The aforementioned positive electrode active material effectively improves the compaction density of the powder and the carrier conduction between positive electrode active materials through particle size gradation, which is beneficial to balancing the energy density and fast charging performance of the battery cell.

[0205] In some embodiments, the powder resistivity R of the positive electrode active material is ≤27.5Ω·cm.

[0206] In this application, the powder resistivity of the positive electrode active material has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be analyzed and tested using a powder resistivity tester (PRCD1100) in accordance with standard GB / T30835-2014.

[0207] In some embodiments, the powder resistivity R of the positive electrode active material can be selected as 1 Ω·cm, 2 Ω·cm, 3 Ω·cm, 4 Ω·cm, 5 Ω·cm, 6 Ω·cm, 7 Ω·cm, 8 Ω·cm, 9 Ω·cm, 10 Ω·cm, 11 Ω·cm, 12 Ω·cm, 13 Ω·cm, 14 Ω·cm, 15 Ω·cm, 16 Ω·cm, 17 Ω·cm, 18 Ω·cm, 19 Ω·cm, 20 Ω·cm, 21 Ω·cm, 22 Ω·cm, 23 Ω·cm, 24 Ω·cm, 25 Ω·cm, 26 Ω·cm, 27 Ω·cm, 27.5 Ω·cm, or any value range between the two.

[0208] In some embodiments, the specific surface area S of the positive electrode active material is 5m². 2 / g~18m 2 / g.

[0209] In this application, the specific surface area of ​​the positive electrode active material has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017, and calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be the Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0210] In some embodiments, the specific surface area S of the positive electrode active material may be selected as 5m². 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g、17m 2 / g、18m 2 / g or any value between the two.

[0211] The resistivity and specific surface area of ​​the positive electrode active material are similar to those of the positive electrode active material for ion conduction.

[0212] The carbon structure in the positive electrode active layer is highly correlated. Positive electrode active materials with powder resistivity and specific surface area within the above range have both good ion conductivity and electronic conductivity, which is beneficial to improving the fast charging performance of battery cells.

[0213] In some embodiments, the positive electrode active layer includes a lithium replenishing agent, which includes at least one of ternary lithium replenishing materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, and lithium trilithium citrate.

[0214] Lithium replenishment agents typically refer to materials that decompose and release active lithium during electrochemical processes to compensate for the irreversible loss of active lithium caused by the growth of the SEI film on the negative electrode. Adding lithium replenishment agents to the positive electrode active layer can counteract the irreversible lithium loss during electrochemical processes, thereby improving the total capacity and energy density of the battery cell.

[0215] Ternary lithium-ion supplementary materials refer to lithium supplementary agents comprising one or more oxides of nickel, cobalt, and manganese. In some embodiments, the general formula of the ternary lithium-ion supplementary material is shown in Formula III.

[0216] Li x3 A y3 Ni a3 Co b3 Mn c3 M3(1-a3-b3-c3)Y z3 Formula III

[0217] Wherein, 0≤x³≤2.1, 0≤y³≤2.1, and 0.9≤x³+y³≤2.1; 0≤a³≤1, 0≤b³≤1, 0≤c³≤1, and 0.1≤a³+b³+c³≤1; 1.8≤z³≤3.5; A includes one or more of Na, K, and Mg; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; Y includes one or more of O and F.

[0218] In some implementations, x3 can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, or any value between two of these. y3 can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, ... The values ​​can be 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, or any range between two of these. Furthermore, x³ + y³ can be selected from 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, or any range between two of these. a³ can be selected from 0, 0.1, 0.2, 0.3. The values ​​b3 and c3 can be 0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or any two of these values. The range of values ​​is defined as follows: a3+b3+c3 can be selected from 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or any two of these values; z3 can be selected from 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5 or any two of these values.

[0219] In some embodiments, the lithium supplement agent is added to the positive electrode film layer at a mass content of 0.1% to 10%.

[0220] In some embodiments, the mass percentage of the lithium replenishing agent added to the positive electrode film can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value range between the two.

[0221] The percentage of lithium replenishing agent by mass content in the positive electrode film is calculated by dividing the mass of lithium replenishing agent by the total mass of the positive electrode film.

[0222] In some embodiments, the positive electrode includes a positive conductive layer disposed between the positive current collector and the positive active layer, and the thickness of the positive conductive layer is 0.5 μm to 2 μm; and / or the negative electrode includes a negative conductive layer disposed between the negative current collector and the negative active layer, and the thickness of the negative conductive layer is 0.5 μm to 2 μm.

[0223] In some embodiments, the thickness of the positive or negative conductive layer can be selected from 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, or any value range between the two.

[0224] The addition of a positive electrode conductive layer and / or a negative electrode conductive layer is beneficial to improving the electronic conductivity of the battery cell electrode and thus improving the energy density of the battery cell.

[0225] In some embodiments, the positive electrode conductive layer includes a conductive agent and a first binder, and the negative electrode conductive layer includes a conductive agent and a second binder. The conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Optionally, the conductive agent includes superconducting carbon and carbon nanotubes. The first binder includes a fluorinated binder, and the second binder includes a water-soluble binder.

[0226] In some embodiments, fluorinated adhesives refer to adhesives that include fluorine, and examples include, but are not limited to, one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0227] In some embodiments, a water-soluble binder refers to a binder that can be dispersed in an aqueous medium, and examples include, but are not limited to, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0228] In some embodiments, based on the total mass of the positive conductive layer, the mass content of the conductive agent in the positive conductive layer is 30% to 50%, and the mass content of the first binder is 50% to 70%; and / or based on the total mass of the negative conductive layer, the mass content of the conductive agent in the negative conductive layer is 20% to 40%, and the mass content of the second binder is 60% to 80%.

[0229] In some embodiments, based on the total mass of the positive conductive layer, the mass content of the conductive agent in the positive conductive layer is 30% to 50%, and the mass content of the first binder is 50% to 70%.

[0230] In some embodiments, based on the total mass of the positive conductive layer, the mass content of the conductive agent in the positive conductive layer can be selected as 30%, 35%, 40%, 45%, 50%, or any value range between the two, and the mass content of the first binder can be selected as 50%, 55%, 60%, 65%, 70%, or any value range between the two.

[0231] In some embodiments, based on the total mass of the negative electrode conductive layer, the mass content of the conductive agent in the negative electrode conductive layer is 20% to 40%, and the mass content of the second binder is 60% to 80%.

[0232] In some embodiments, based on the total mass of the negative electrode conductive layer, the mass content of the conductive agent in the negative electrode conductive layer can be selected as 20%, 25%, 30%, 35%, 40%, or any value range between the two, and the mass content of the first adhesive can be selected as 60%, 65%, 70%, 75%, 80%, or any value range between the two.

[0233] In some embodiments, the one-sided surface density of the negative electrode active layer is 104 mg / 1540.25 mm². 2 -180mg / 1540.25mm 2 ; 125mg / 1540.25mm is optional. 2 -167mg / 1540.25mm 2 .

[0234] The one-sided density of the negative electrode active layer can be tested using a method similar to that used for the one-sided density of the positive electrode active layer described above.

[0235] In some embodiments, the areal density of the negative electrode active layer may be selected as 104 mg / 1540.25 mm². 2 110mg / 1540.25mm 2 115mg / 1540.25mm 2 120mg / 1540.25mm 2 125mg / 1540.25mm 2 130mg / 1540.25mm 2 140mg / 1540.25mm 2 150mg / 1540.25mm 2 160mg / 1540.25mm 2167mg / 1540.25mm 2 170mg / 1540.25mm 2 180mg / 1540.25mm 2 Or the range of values ​​between any two.

[0236] A negative electrode active layer with a single-sided surface density within the above range can cooperate with a positive electrode active layer to achieve a balance between battery cell energy density and fast charging performance.

[0237] In some embodiments, the compaction density of the negative electrode active layer at 100% SOC of the battery cell is 1.15 g / cm³. 3 ~1.36g / cm 3 ; 1.25g / cm³ is optional 3 ~1.36g / cm 3 .

[0238] The compaction density of the negative electrode active layer at 100% SOC of a single battery cell can be tested by referring to the compaction density of the positive electrode active layer at 100% SOC of a single battery cell described above. It is understandable that the compaction density of the negative electrode active layer at 100% SOC differs from the designed compaction density after cold pressing. During charging and discharging, as lithium ions are inserted / extracted from the negative electrode active layer, the negative electrode active layer expands compared to after cold pressing, resulting in a decrease in the compaction density of the negative electrode active layer at 100% SOC compared to the compaction density after cold pressing.

[0239] In some embodiments, the compaction density of the negative electrode active layer at 100% SOC of the battery cell can be selected as 1.15 g / cm³. 3 1.20g / cm 3 1.25g / cm 3 1.30g / cm 3 1.35g / cm 3 1.36 g / cm 3 Or the range of values ​​between any two.

[0240] In some embodiments, the negative electrode active material includes graphite.

[0241] In some embodiments, the graphite includes composite graphite particles, the composite graphite particles including bulk particles and a coating layer at least partially disposed on the surface of the bulk particles, the bulk particles including artificial graphite, the coating layer including amorphous carbon, and the composite graphite particles including secondary particles.

[0242] Secondary particles are particles formed by the aggregation of two or more primary particles.

[0243] Composite graphite particles, including secondary particles and surface coatings including amorphous carbon, are beneficial for the wetting of electrolyte in the negative electrode active layer of the electrode, which helps to improve the rate performance of the battery cell.

[0244] In some embodiments, the composite graphite material further includes a kinetic carbon material.

[0245] In some embodiments, the kinetic carbon material is located between the primary particles of the bulk material. In this case, the bulk particles of the negative electrode active material include artificial graphite primary particles and the kinetic carbon material located between the primary particles.

[0246] In some embodiments, kinetic carbon material is located within the coating layer. In this case, the coating layer comprises both amorphous carbon and kinetic carbon material.

[0247] In some implementations, the kinetic carbon material raw material includes one or more of hard carbon, expanded graphite, and graphene.

[0248] In this article, "kinetic carbon material raw material" and "kinetic carbon material raw material powder" are completely identical in composition. "Kinetic carbon material" refers to the product of "kinetic carbon material raw material" after graphitization and / or carbonization treatment.

[0249] In some embodiments, the interlayer spacing d002 of the crystal plane of the kinetic carbon material raw material (002) is ≥0.3358 nm, and optionally 0.3359 nm to 0.3366 nm.

[0250] The interlayer spacing of the kinetic carbon material raw materials is larger than that of conventional graphite (the interlayer spacing of conventional graphite is 0.335 nm). When the kinetic carbon material obtained from it is uniformly distributed in the bulk particles and / or coating layers of the composite graphite material, it is conducive to the rapid insertion and extraction of active ions, thereby improving the transport performance of active ions and electrons, and thus improving the fast charging performance of the battery cell without causing a large loss of energy density of the battery cell, achieving a balance between fast charging performance and energy density of the battery cell.

[0251] In some embodiments, the mass content of amorphous carbon in the coating layer of the composite graphite particles is 2% to 5% based on the total mass of the composite graphite particles.

[0252] In some embodiments, based on the total mass of the composite graphite particles, the mass content of amorphous carbon in the coating layer of the composite graphite particles can be selected as 2%, 3%, 4%, 5%, or any value range between the two.

[0253] When the content of amorphous carbon is within a suitable range, composite graphite materials can have both high specific capacity and high active ion solid-phase transport capability, which is beneficial to improving the fast charging performance of battery cells.

[0254] In some embodiments, the resistivity of the negative electrode active material powder is less than or equal to 0.04 Ω·cm.

[0255] In some embodiments, the powder resistivity of the negative electrode active material can be selected as 0.01 Ω·cm, 0.02 Ω·cm, 0.03 Ω·cm, 0.04 Ω·cm, or any value range between the two.

[0256] The powder resistivity of the negative electrode active material can be tested by any method known in the art. As an example, the powder resistivity test method for the positive electrode active material described above can be used for testing.

[0257] In some embodiments, the powder compaction density of the negative electrode active material under a pressure of 20000N is 1.5 g / cm³. 3 Up to 1.7 g / cm 3 1.55g / cm³ is an optional value. 3 Up to 1.65 g / cm 3 .

[0258] The compaction density of the negative electrode active material powder under 20,000 N pressure can be tested using any method known in the art. As an example, it can be determined using instruments and methods known in the art. For instance, it can be determined using an electronic pressure testing machine (e.g., a UTM7305 type electronic pressure testing machine) according to GB / T 24533-2009. An exemplary test method is as follows: Weigh 1 g of negative electrode active material powder and add it to a container with a bottom area of ​​1.327 cm². 2 In the mold, the pressure is increased to 20000N, held for 30s, then the pressure is released and held for 10s. The compaction density of the material under 20000N pressure is then recorded and calculated.

[0259] In some embodiments, the powder compaction density of the negative electrode active material under 20000N pressure can be selected as 1.5 g / cm³. 3 1.55g / cm 3 1.6g / cm 3 1.65g / cm 3 1.7g / cm 3 Or the range of values ​​between any two.

[0260] Anode active materials with a powder compaction density within a suitable range can enable the anode active layer to have a high compaction density, thereby enabling the battery cell to have a high energy density; at the same time, the anode active layer can maintain its original pore structure during cycling, which is beneficial to improving the high-fast charging performance of the battery cell during cycling.

[0261] In some embodiments, the negative electrode active material further includes a silicon-based material, which includes at least one of silicon, silicon oxide, and silicon-carbon composite; based on the total mass of the negative electrode active material, the silicon content in the silicon-based material is 0.3% to 10%, optionally 1% to 6%.

[0262] In some embodiments, based on the total mass of the negative electrode active material, the mass content of silicon element in the silicon-based material can be selected as 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value range between the two.

[0263] The introduction of silicon-based materials is beneficial for improving the energy density of individual battery cells. Silicon-based materials within the aforementioned mass range can balance the energy density and cycle stability of individual battery cells.

[0264] In some embodiments, the charge capacity of the negative electrode active material is from 350 mAh / g to 480 mAh / g.

[0265] The specific capacity of the negative electrode active material can be tested using known testing methods. As an example, the test methods for initial coulombic efficiency and initial discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used. The battery cell is disassembled to obtain the negative electrode sheet. A lithium metal sheet is used as the counter electrode, a polyethylene film as the separator, and the electrolyte in the battery cell is used as the electrolyte for the coin cell. The coin cells are assembled into CR2430 type coin cells in an argon-protected glove box. After the obtained coin cells are left to stand for 12 hours, they are discharged at 25°C with a constant current of 0.05C to 0.005V. After standing for 10 minutes, they are discharged again with a constant current of 50μA to 0.005V. After standing for 10 minutes, they are discharged again with a constant current of 10μA to 0.005V. Then, they are charged at a constant current of 0.1C to 2V, and the charging capacity is recorded. The ratio of the charging capacity to the mass of the negative electrode active material is the specific capacity of the material.

[0266] In some embodiments, the charge capacity of the negative electrode active material is 350mAh / g, 360mAh / g, 370mAh / g, 380mAh / g, 390mAh / g, 400mAh / g, 410mAh / g, 420mAh / g, 430mAh / g, 440mAh / g, 450mAh / g, 460mAh / g, 470mAh / g, 480mAh / g, or any value between the two.

[0267] Negative electrode active materials with a charge capacity within the above range are beneficial to improving the energy density of battery cells.

[0268] In some embodiments, the negative electrode active layer includes a first negative electrode active material layer disposed on the surface of the negative electrode current collector and a second negative electrode active material layer disposed on the side of the first negative electrode active material layer away from the negative electrode current collector, wherein the second negative electrode active material layer includes composite graphite particles.

[0269] In some embodiments, the first negative electrode active material layer includes one or more of composite graphite particles and natural graphite.

[0270] Placing composite graphite particles close to the electrolyte side can improve the fast-charging performance of individual battery cells while maintaining energy density.

[0271] In some embodiments, the thickness ratio of the second negative electrode active material layer to the thickness of the first negative electrode active material layer is 3:7 to 7:3.

[0272] In some embodiments, the ratio of the thickness of the second negative electrode active material layer to the thickness of the first negative electrode active material layer can be selected as 3:7, 4:7, 5:7, 6:7, 1:1, 2:1, 7:3 or any range between the two.

[0273] In some embodiments, the volume average particle size Dv501 of the negative electrode active material in the first negative electrode active material layer is 9.5 μm to 18.5 μm, and can be selected as 9.5 μm to 14.8 μm.

[0274] In some embodiments, the volume average particle size Dv501 of the negative electrode active material in the first negative electrode active material layer can be selected as 9.5μm, 9.8μm, 10μm, 10.8μm, 11μm, 11.8μm, 12μm, 12.8μm, 13μm, 13.8μm, 14μm, 14.8μm, 15μm, 15.8μm, 16μm, 16.8μm, 17μm, 17.8μm, 18μm, 18.5μm or any value range between the two.

[0275] In some embodiments, the volume average particle size Dv502 of the negative electrode active material in the second negative electrode active layer is 7.8 μm to 14.3 μm, and can be selected as 7.8 μm to 12.8 μm.

[0276] In some embodiments, the volume average particle size Dv502 of the negative electrode active material in the second negative electrode active material layer can be selected as 7.8 μm, 8 μm, 8.8 μm, 9 μm, 9.8 μm, 10 μm, 10.8 μm, 11 μm, 11.8 μm, 12 μm, 12.8 μm, 13 μm, 13.8 μm, 14 μm, 14.3 μm or any value range between the two.

[0277] The volume average particle sizes Dv501 and Dv502 of the negative electrode active materials in the first and second negative electrode active material layers can be tested using the volume average particle size test method described above.

[0278] The second negative electrode active material layer disposed on the electrolyte side includes negative electrode active materials with smaller particle size, which can further improve the solid-liquid transport rate of ions in the battery electrode and improve the fast charging performance of the battery cell.

[0279] In some embodiments, the battery cell further includes a separator, the separator comprising a porous base film and a functional layer disposed on at least one side of the porous base film, wherein the thickness of the porous base film is less than or equal to 12 μm, and optionally less than or equal to 9 μm.

[0280] In some embodiments, the porous base membrane includes one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The porous base membrane can be a single-layer film or a multi-layer composite film, without particular limitation.

[0281] In some embodiments, the porosity of the porous base membrane in the separator is 20%-70%, optionally 35%-60%.

[0282] In some embodiments, the porosity of the porous base membrane in the isolation membrane can be selected as 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any value range between the two.

[0283] In some embodiments, the functional layer includes a first functional layer disposed on the negative electrode side of the porous base membrane and a second functional layer disposed on the positive electrode side of the porous base membrane. The first functional layer includes first inorganic particles, and the second functional layer includes composite particles. The composite particles include second inorganic particles and a non-fluoropolymer. The second inorganic particles in the composite particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

[0284] In some embodiments, the inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

[0285] Inorganic particles can improve the heat resistance of the first and second functional layers and enhance the fast-charging performance of individual battery cells.

[0286] In some embodiments, the non-fluoropolymer particles comprise acrylate copolymers.

[0287] In some embodiments, the electrolyte injection coefficient of the battery cell is 2.4 g / Ah-3.1 g / Ah.

[0288] The electrolyte filling coefficient of a battery cell refers to the ratio of the mass of electrolyte inside the battery cell to the battery capacity. The electrolyte filling coefficient of a battery cell can be obtained by any method known in the art. For example, the mass of electrolyte in a battery cell can be obtained by the following method: Weigh the battery, and record the mass as M0. Disassemble the battery cell and pour out the free electrolyte. Remove the internal electrode assembly and separate the positive electrode, negative electrode, separator, and mechanical components. Soak the positive electrode, negative electrode, separator, and mechanical components in dimethyl carbonate (DMC) solvent for 24-48 hours, repeating the soaking process at least three times. Place the aforementioned positive electrode, negative electrode, separator, and mechanical components in a 100°C oven for at least 24 hours until completely dried. Weigh the dried positive electrode, negative electrode, separator, and mechanical components, and record the mass as M1. The mass of electrolyte in the battery cell is thus obtained as (M0-M1). The electrolyte filling coefficient is calculated by dividing (M0-M1) by the rated capacity of the battery cell. The rated capacity is the nominal capacity of the battery, or the rated capacity is obtained by charging the battery to 3.65V at a charging rate of 0.33C, then charging it to 0.05C at a constant voltage of 3.65V, letting it stand for 10 minutes, and then discharging it to 2.0V at a discharging rate of 0.33C.

[0289] In some embodiments, the electrolyte injection coefficient of the battery cell can be selected as 2.4 g / Ah, 2.5 g / Ah, 2.6 g / Ah, 2.7 g / Ah, 2.8 g / Ah, 2.9 g / Ah, 3.0 g / Ah, 3.1 g / Ah or any value range between the two.

[0290] Within the above-mentioned range, the electrolyte injection coefficient can improve the cycle stability of individual battery cells.

[0291] In some embodiments, the battery cell further includes electrode terminals, and the electrode assembly includes tabs that are directly welded to the electrode terminals.

[0292] In some embodiments, the battery cell is charged from 10% state of charge (SOC) to 80% state of charge (SOC) at 30°C in 6 to 15 minutes.

[0293] The time it takes for a single battery cell to charge from 10% State of Charge (SOC) to 80% SOC at 30°C can be tested using any method known in the art. As an example, at 30°C, charging can be performed from 10% SOC to 15% SOC at a constant current of 5.0C; from 15% SOC to 20% SOC at a constant current of 5.0C; from 20% SOC to 25% SOC at a constant current of 5.0C; from 25% SOC to 30% SOC at a constant current of 5.0C; from 30% SOC to 35% SOC at a constant current of 5.0C; from 35% SOC to 40% SOC at a constant current of 5.0C; and from 40% SOC at a constant current of 4.6C. Charge to 45% SOC, then charge at a constant current of 4.3C from 45% SOC to 50% SOC, then at a constant current of 4.0C from 50% SOC to 55% SOC, then at a constant current of 3.7C from 55% SOC to 60% SOC, then at a constant current of 3.4C from 60% SOC to 65% SOC, then at a constant current of 3.1C from 65% SOC to 70% SOC, then at a constant current of 2.9C from 70% SOC to 75% SOC, and finally at a constant current of 2.7C from 75% SOC to 80% SOC. Record the total charging time.

[0294] In some embodiments, the time for the battery cell to be charged from 10% state of charge (SOC) to 80% state of charge (SOC) at 30°C can be selected as 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, or any value range between the two.

[0295] This battery cell has excellent fast-charging performance, which can meet the needs of improving the energy replenishment efficiency of electrical devices.

[0296] In some embodiments, the battery cell has a wound structure, the thickness of the positive current collector is less than or equal to 15 μm, and the thickness of the negative current collector is less than or equal to 6 μm.

[0297] The materials for the positive and / or negative current collectors are not particularly limited, as long as they do not cause chemical changes in the battery cell and are conductive. Current collectors include metal foils with a pure metal content of 95% or higher, such as at least one of copper, aluminum, stainless steel, titanium, and nickel foils. They also include alloy foils with at least two main metals, for example, alloy foils made from at least two main elements of copper, aluminum, nickel, titanium, and iron. Furthermore, they can include copper, aluminum-cadmium alloys, iron, or stainless steel with surface treatments using carbon, nickel, titanium, silver, copper, etc. In addition, the bonding force with the negative electrode active material can be enhanced by forming micro-uneven surfaces, and they can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0298] In some embodiments, the thickness of the positive current collector can be selected as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any value range between the two.

[0299] In some implementations, the thickness of the negative electrode current collector can be selected as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm or any value range between the two.

[0300] The positive electrode current collector and / or negative electrode current collector have a lower thickness, which enables a further increase in the energy density of the battery cell.

[0301] In some embodiments, the volumetric energy density of the battery cell is 400Wh / L to 500Wh / L.

[0302] In some embodiments, the volumetric energy density of the battery cell can be selected as 400Wh / L, 410Wh / L, 420Wh / L, 430Wh / L, 440Wh / L, 450Wh / L, 460Wh / L, 470Wh / L, 480Wh / L, 490Wh / L, 500Wh / L, or any value range between the two.

[0303] The volumetric energy density of a single battery cell can be tested using any method known in the art. For example, a single battery cell is placed at 25°C, charged to 3.65V with a constant current of 0.33C, then charged to 0.05C with a constant voltage, and discharged to 2.0V with a constant current of 0.33C. The discharge capacity A0 is recorded at this point, in Ah. The length, width, and height of the single battery cell are measured using calipers (generally calculated based on the battery casing dimensions, excluding the height of the electrode terminals and the insulating film outside the casing). The volumetric energy density V0 of the single battery cell is calculated, in L. The volumetric energy density VED of the single battery cell is calculated as (A0 × discharge plateau voltage) / V0, in Wh / L.

[0304] This battery cell also has high energy density, which can meet the needs of increasing the driving range of electrical devices.

[0305] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0306] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0307] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square battery cell 5 as an example.

[0308] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0309] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0310] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0311] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0312] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0313] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0314] The second aspect of this application provides a battery device including the battery cell provided in the first aspect of this application, the battery device including at least one of a battery module, a battery pack, and an energy storage battery.

[0315] Furthermore, a third aspect of this application provides an electrical device, which includes the battery cell provided in the first aspect of this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0316] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0317] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the individual battery cells, a battery pack or battery module can be used.

[0318] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0319] Example

[0320] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0321] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0322] Example 1

[0323] Preparation of positive electrode sheet

[0324] Lithium iron phosphate (LiFePO4), polyvinylidene fluoride (PVDF), and acetylene black (NMP) were mixed in a ratio of 97:2:1, and then N-methylpyrrolidone (NMP) was added as a solvent and stirred to form a positive electrode slurry. The compacted density of the positive electrode active material powder was 2.53 g / cm³. 3 The volume average particle size Dv50 of the positive electrode active material 正 It is 1.6μm, Dv10 正 It is 0.64 μm.

[0325] The positive electrode conductive layer is formed by uniformly mixing conductive carbon SP, binder polyvinylidene fluoride (PVDF), and solvent N-methylpyrrolidone NMP and then coating it onto the surface of the current collector, with a thickness of 1 μm.

[0326] A positive electrode conductive paste is uniformly coated onto a positive electrode current collector aluminum foil with a thickness of 13 μm. After drying, a positive electrode conductive layer is obtained. Then, a positive electrode paste is uniformly coated onto the positive electrode conductive layer, followed by drying and cold pressing to obtain the positive electrode sheet. The areal density of the positive electrode active layer of the positive electrode sheet is 300 mg / 1540.25 mm². 2 When the battery is charged at a rate of 0.33C to 100% SOC, the compaction density of the positive electrode is 2.63 g / cm³. 3 ;

[0327] Preparation of negative electrode sheet

[0328] Graphite (negative electrode active material), acetylene black (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) were mixed in a mass ratio of 96:1:2:1, and then deionized water was added as a solvent to form a negative electrode slurry. The negative electrode slurry was uniformly coated onto a copper foil current collector, and after drying and cold pressing, a negative electrode sheet was obtained; the thickness of the copper foil current collector was 4.5 μm. The areal density of the negative electrode active layer of the negative electrode sheet was 138 mg / 1540.25 mm². 2 The compaction density of the negative electrode sheet when the battery is charged to 100% SOC at a charging rate of 0.33C is 1.26 g / cm³. 3 The volume distribution particle size Dv50 of the negative electrode active material is 10.5 μm;

[0329] Electrolyte preparation

[0330] In an argon-atmospheric glove box with a water content <10 ppm, ethylene carbonate EC, ethyl methyl carbonate EMC, and ethyl acetate EA were thoroughly mixed at a mass ratio of 35:15:50 to obtain the electrolyte solvent. Lithium hexafluorophosphate (LiPF6) and lithium difluorosulfonyl imide (LiFSI) were slowly added as lithium salts, and the mixture was stirred thoroughly until completely dissolved. After returning to room temperature, the following additives were added sequentially at mass percentages relative to the total electrolyte mass: ethylene carbonate VC (3.5%), fluoroethylene carbonate FEC (1%), 1% 1,3-propylene sulfonate lactone (PS), 0.5% vinyl sulfite (DTD), and 0.5% lithium difluorophosphate (LiPO2F2). The mixture was thoroughly mixed to obtain the electrolyte. Based on the total mass of the electrolyte, the mass percentage of lithium hexafluorophosphate (LiPF6) was 10.5%, the mass percentage of lithium difluorosulfonyl imide (LiFSI) was 4.5%, and the conductivity of the electrolyte was 15.4 mS / cm.

[0331] Preparation of the separating membrane

[0332] The separator includes a base membrane, which is a 7μm polyethylene film layer with a porosity of 42%.

[0333] Preparation of battery cells

[0334] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain a wound electrode assembly. The electrode assembly is then placed in a square aluminum outer casing, dried, and injected with electrolyte. After processes including encapsulation, settling, formation, aging, secondary encapsulation, and capacity testing, a single battery cell is obtained. The electrolyte retention coefficient d3 / A of the single battery cell is 2.9 g / Ah.

[0335] The preparation methods of Examples 2-12 are basically the same as those of Example 1, except that some parameters in the battery cells are adjusted, as shown in Table 1.

[0336] Example 13

[0337] The battery preparation method in Example 13 is basically the same as that in Example 1, except that the negative electrode sheet in Example 13 is double-coated. The specific preparation method of the negative electrode sheet is as follows:

[0338] The negative electrode active material, first graphite, conductive agent, acetylene black, binder, styrene-butadiene rubber, and thickener, sodium carboxymethyl cellulose, are mixed in a mass ratio of 96:0.5:2.5:1. Then, deionized water is added as a solvent and stirred evenly to form the first negative electrode slurry.

[0339] The negative electrode active material, second graphite, conductive agent, acetylene black, binder, styrene-butadiene rubber, and thickener, sodium carboxymethyl cellulose, are mixed in a mass ratio of 96:0.5:2.5:1. Then, deionized water is added as a solvent and stirred evenly to form the second negative electrode slurry.

[0340] A first negative electrode slurry is uniformly coated onto the negative electrode conductive layer of the negative electrode current collector copper foil and dried. A second negative electrode slurry is then coated onto the dried first negative electrode slurry surface. After drying and cold pressing, a negative electrode sheet is obtained. The negative electrode sheet includes a negative electrode current collector and a negative electrode conductive layer and a negative electrode active material layer sequentially disposed on the negative electrode current collector. The negative electrode active material layer includes a first negative electrode active layer and a second negative electrode active layer sequentially disposed on the negative electrode conductive layer.

[0341] Of these, the single-sided coating mass of the negative electrode sheet, based on the total mass of the negative electrode active material layer, is 138 mg / mm². 2 The compaction density of the positive electrode sheet when the battery is charged at a rate of 0.33C to 100% SOC is 1.25 g / cm³. 3 Based on the total mass of the first graphite and the second graphite in the negative electrode active material layer, the mass proportions of the first graphite and the second graphite are 50% and 50%, respectively.

[0342] The preparation methods of Comparative Examples 1-6 are basically the same as those of Example 1, except that some parameters in the battery cells are adjusted.

[0343] Test methods

[0344] (a) The test procedure for the time T for charging a single battery cell from 10% SOC to 80% SOC at 30℃ is as follows:

[0345] Charging from a battery state of 10% SOC at an ambient temperature of 30°C.

[0346] Charge from 10% SOC to 15% SOC at a constant current of 5.0C;

[0347] Charge from 15% SOC to 20% SOC at a constant current of 5.0C;

[0348] Charge from 20% SOC to 25% SOC at a constant current of 5.0C;

[0349] Charge from 25% SOC to 30% SOC at a constant current of 5.0C;

[0350] Charge from 30% SOC to 35% SOC at a constant current of 5.0C;

[0351] Charge from 35% SOC to 40% SOC at a constant current of 5.0C;

[0352] Charge from 40% SOC to 45% SOC at a constant current of 4.6C;

[0353] Charge from 45% SOC to 50% SOC at a constant current of 4.3C;

[0354] Charge from 50% SOC to 55% SOC at a constant current of 4.0C;

[0355] Charge from 55% SOC to 60% SOC at a constant current of 3.7C;

[0356] Charge from 60% SOC to 65% SOC at a constant current of 3.4C;

[0357] Charge from 65% SOC to 70% SOC at a constant current of 3.1C;

[0358] Charge from 70% SOC to 75% SOC at a constant current of 2.9C;

[0359] Charge from 75% SOC to 80% SOC at a constant current of 2.7C;

[0360] Record the total charging time. The time may vary depending on the specific implementation, but can be adjusted by fine-tuning the charging rate.

[0361] (II) Number of cycles at 60℃ to 80% SOH

[0362] At 60℃, charge the battery to 3.65V at a 1C charging rate (the nominal capacity of the battery), then charge it to 0.05C at a constant voltage of 3.65V, let it stand for 10 minutes, and then discharge it to 2.5V at a 1C discharging rate, let it stand for 10 minutes. One charge-discharge cycle is one cycle. The test is stopped when the battery capacity decays to 80% of the initial discharge capacity. This number is recorded as the number of cycles @ 80% SOH.

[0363] (III) DC internal resistance (DCR) test of individual battery cells:

[0364] You can refer to the methods in GB / T 31467 "Performance Test Specification for High-Power Lithium-ion Power Batteries for HEVs".

[0365] For example, at room temperature, charge a single battery cell to 3.65V with a constant current of 0.33C, let it stand for 1 minute, then charge it to 3.65V with a constant current of 0.1C, let it stand for 30 minutes, and then discharge it to 2.0V with a constant current of 0.33C. Record the discharge capacity A0 at this point in Ah. Then charge it to 0.5A0 Ah with a constant current of 0.33C and adjust the SOC to 50%.

[0366] After placing the battery cell at -20℃ for 2 hours, it was discharged at a constant current of 4C for 10 seconds, and ΔU was recorded. 放电 ΔI 放 电 The discharge DCR data of lithium-ion batteries can be calculated using the following formula, R. 放电 =ΔU 放电 / ΔI 放电 ,

[0367] Wherein, ΔU 放电 ΔI represents the voltage change within 10 seconds of the start of discharge.放电 This represents the current value within 10 seconds of the start of discharge. Some parameters of each embodiment and comparative example are shown in Table 1, where all contents are by mass, and the unit for the single-sided coating mass of the positive and negative electrodes is mg / 1540.25mm. 2 .

[0368] In Example 1, the compaction density of the positive electrode active layer of the battery cell at 100% SOC was 2.63 g / cm³. 3 At 100% SOC, the compaction density of the negative electrode active layer in a single battery cell is 1.26 g / cm³. 3 .

[0369] The test results of each embodiment and comparative example are shown in Tables 2 and 3.

[0370] Table 1

[0371] Table 2

[0372] Table 3

[0373] Test Results

[0374] As can be seen from the comparison between the embodiments and comparative examples of this application, the positive electrode active layer includes a positive electrode active material, the positive electrode active material includes lithium phosphate, and the one-sided surface density of the positive electrode active layer is 230 mg / 1540.25 mm². 2 ~400mg / 1540.25mm 2 The electrolyte comprises a solvent and a lithium-containing electrolyte salt. The solvent includes chain carboxylic acid esters and ethylene carbonate. The lithium-containing electrolyte salt includes one or more of lithium hexafluorophosphate and fluorosulfonyl imide salts. The battery cell with a lithium-containing electrolyte salt to ethylene carbonate mass ratio of 0.29-0.72 and an electrolyte conductivity of 13mS / cm-20mS / cm can balance the energy density and fast-charging performance of the battery cell, thereby achieving a comprehensive improvement in battery performance.

[0375] As can be seen from the comparison of Examples 1 and 6-7, based on the total mass of the electrolyte, battery cells with a chain carboxylic acid ester content of 25.5%-63.75% can further ensure cycle stability and improve the overall performance of the battery cells.

[0376] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same essential structure and achieving the same effect as the technical concept within the scope of this disclosure are included in the technical scope of this disclosure. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A battery cell, characterized by, The positive electrode sheet and the electrolyte solution; The positive electrode sheet includes a positive electrode current collector and a positive electrode active layer on at least one surface of the positive electrode current collector, the positive electrode active layer including a positive electrode active material, the positive electrode active material including a lithium-containing phosphate, the single-sided area density of the positive electrode active layer being 230 mg / 1540.25 mm 2 ~ 400 mg / 1540.25 mm 2 ; The electrolyte solution comprises a solvent and a lithium-containing electrolyte salt, the solvent comprises a chain carboxylic ester and ethylene carbonate, the lithium-containing electrolyte salt comprises one or more of lithium hexafluorophosphate, a fluorosulfonylimide salt; wherein the mass ratio of the lithium-containing electrolyte salt to ethylene carbonate is 0.29-0.72; The conductivity of the electrolyte solution is 13 mS / cm-20 mS / cm.

2. The battery cell of claim 1, wherein, In the electrolyte solution, the mass ratio of ethylene carbonate to the chain carboxylic ester is 0.26:1-1:

1.

3. The battery cell according to claim 1 or 2, characterized in that, The mass content of the chain carboxylic ester accounts for 25.5%-63.75% based on the total mass of the electrolyte solution.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The chain carboxylic ester has a general structure of R1-COO-R2, wherein R1 and R2 each independently comprises one or more of C1-C5 alkyl and C1-C5 halogenated alkyl.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The chain carboxylic ester comprises one or more of ethyl butyrate, ethyl propionate, ethyl acetate, methyl acetate, and methyl formate.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The mass content of ethylene carbonate accounts for 17%-34% based on the total mass of the electrolyte solution.

7. The battery cell of any one of claims 1 to 6, wherein, The lithium-containing electrolyte salt comprises lithium hexafluorophosphate.

8. The battery cell of claim 7, wherein, The lithium-containing electrolyte salt further comprises at least one of a fluorosulfonylimide salt, and optionally, the fluorosulfonylimide salt comprises one or more of lithium bisfluorosulfonylimide and lithium bis-trifluoromethylsulfonylimide.

9. The battery cell of any one of claims 1 to 8, wherein, The lithium-containing electrolyte salt comprises lithium bisfluorosulfonylimide and lithium hexafluorophosphate, and the mass ratio of lithium bisfluorosulfonylimide to lithium hexafluorophosphate in the electrolyte solution is (2-5):

10.

10. The battery cell of any one of claims 1 to 9, wherein, The battery cell further comprises a negative electrode tab, the negative electrode tab comprising a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material, the negative electrode active material having a volume distribution particle size Dv10 负 is 3.5 μm-7.5 μm, optionally 4.5 μm-6.5 μm; Dv99 负 is 25 μm-35 μm.

11. The battery cell of any one of claims 1 to 10, wherein, The electrolyte solution further comprises an additive, the additive comprises at least one of a carbonate additive, a sulfur-containing additive, and a lithium salt additive, the lithium salt additive comprises one or more of lithium difluorophosphate, lithium difluoro oxalate borate, lithium tetrafluoroborate, and lithium bis-oxalate borate.

12. The battery cell of any one of claims 1 to 10, wherein, The additive comprises at least two of the carbonate additive, the sulfur-containing additive, and the lithium salt additive.

13. The battery cell according to claim 11 or 12, characterized in that The mass content of the additive in the electrolyte solution accounts for 1%-10% based on the total mass of the electrolyte solution, which is optionally 2%-8%, and further optionally 3.5%-8%.

14. The battery cell of claim 11 or 12, wherein, The carbonate additive comprises one or more of vinylene carbonate and fluorinated vinyl carbonate.

15. The battery cell of any one of claims 11 to 14, wherein, The sulfur-containing additive comprises one or more of vinyl sulfate, bis vinyl sulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methyl methylene disulfonate.

16. The battery cell of any one of claims 11 to 15, wherein, The additive comprises vinylene carbonate, and the mass content of vinylene carbonate in the electrolyte solution accounts for 0.5%-9% based on the total mass of the electrolyte solution, which is optionally 2%-6%.

17. The battery cell of any one of claims 11 to 15, wherein, The additive comprises fluorinated vinyl carbonate, and the mass content of fluorinated vinyl carbonate in the electrolyte solution accounts for 0.1%-4% based on the total mass of the electrolyte solution, which is optionally 0.5%-3%.

18. The battery cell of any one of claims 1-17, wherein, The electrolyte solution comprises vinylene carbonate and fluorinated vinyl carbonate, and the total mass of vinylene carbonate and fluorinated vinyl carbonate accounts for 0.008-0.5 of the mass of the chain carboxylic ester.

19. The battery cell of any one of claims 1-18, wherein, The electrolyte has an electrical conductivity of 14 mS / cm-20 mS / cm, which can be 15 mS / cm-20 mS / cm.

20. The battery cell of any one of claims 1 to 19, the positive electrode active layer having a single-sided areal density of 280 mg / 1540.25 mm 2 - 370 mg / 1540.25 mm 2 .

21. The battery cell of any one of claims 1-20, wherein, The compaction density of the positive electrode active layer is 2.50 g / cm 3 ~ 2.80 g / cm 3 ; and can be 2.55 g / cm 3 ~ 2.68 g / cm 3 .

22. The battery cell of any one of claims 1-21, wherein, The lithium-containing phosphate is a lithium-containing phosphate of olivine structure, including a component as shown in formula I, Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula I, wherein, 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.7≤x1+y1≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, and 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z1≤5; A includes one or more of Na, K, Mg; Me includes one or more of Mn, Fe, Co, Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X includes one or more of S, Si, Cl, B, C, N; Y includes one or more of O, F.

23. The battery cell of claim 22, wherein, The positive electrode active material further includes an ion-conducting layer disposed on the surface of the lithium-containing phosphate, the ion-conducting layer including carbon elements, the mass percentage of the carbon elements being 1%-2% based on the total mass of the positive electrode active material.

24. The battery cell of claim 23, wherein, The ion-conducting layer further comprises a fast ion conductor having a NASICON structure as shown in Formula II, Li 3-b2 Fe 2-b2 M2 b2 (PO x2 ) y2 Formula II, In the formula II, M2 is selected from one or more of +4-valent Ti, Zr, Hf, Ge, and Sn, 0≤b2≤1, 3≤x2≤5, and 2≤y2≤4.

25. The battery cell of claim 24, wherein, The fast ion conductor includes one or more of Li2FeTi(PO4)3, Li2FeZr(PO4)3, and Li2FeSn(PO4)3.

26. The battery cell of any one of claims 1-25, wherein, The positive electrode active material satisfies at least one of the following conditions: (1) the positive electrode active material has a powder compaction density under 30000N pressure of 2.46 g / cm3 or more 3 , optionally 2.46 g / cm3 3 - 2.8 g / cm3 3 ; (2) the volume average particle diameter of the positive electrode active material satisfies: 1 pm ≤ Dv50 正 ≤ 2 pm, 0.4 pm ≤ Dv10 正 ≤ 0.7 pm; (3) the powder resistivity R of the positive electrode active material is ≤27.5 Ω·cm; (4) the specific surface area S of the positive electrode active material is 5 m 2 / g-18 m 2 / g.

27. The battery cell of any one of claims 1-26, wherein, The positive electrode active layer includes a lithium supplementing agent, the lithium supplementing agent including at least one of a ternary lithium supplementing material, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganite, lithium tartrate, and trilithium citrate.

28. The battery cell of claim 27, wherein, The general formula of the ternary lithium supplementing material is shown as formula III, Li x3 A y3 Ni a3 Co b3 Mn c3 M3(1-a3-b3-c3)Y z3 , Formula III wherein, 0≤x3≤2.1, 0≤y3≤2.1, and 0.9≤x3+y3≤2.1; 0≤a3≤1, 0≤b3≤1, 0≤c3≤1, and 0.1≤a3+b3+c3≤1; 1.8≤z3≤3.5; A includes one or more of Na, K, Mg; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y includes one or more of O, F.

29. The battery cell of claim 27 or 28, wherein, The mass content of the lithium supplementing agent in the positive electrode film layer is 0.1%-10%.

30. The battery cell of any one of claims 1-29, wherein, The positive electrode tab comprises a positive electrode conductive layer provided between the positive electrode current collector and the positive electrode active layer, the thickness of the positive electrode conductive layer being 0.5-2 μm; and / or the negative electrode tab comprises a negative electrode conductive layer provided between the negative electrode current collector and the negative electrode active layer, the thickness of the negative electrode conductive layer being 0.5-2 μm.

31. The battery cell of claim 30, wherein, The positive electrode conductive layer comprises a conductive agent and a first binder, the negative electrode conductive layer comprises a conductive agent and a second binder, the conductive agent comprises one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, optionally, the conductive agent comprises super conductive carbon and carbon nanotubes, the first binder comprises a fluorine-containing binder, and the second binder comprises a water-soluble binder.

32. The battery cell of claim 31, wherein, The mass content of the conductive agent in the positive electrode conductive layer is 30-50% based on the total mass of the positive electrode conductive layer, and the mass content of the first binder is 50-70%; and / or The mass content of the conductive agent in the negative electrode conductive layer is 20-40% based on the total mass of the negative electrode conductive layer, and the mass content of the second binder is 60-80%.

33. The battery cell of any one of claims 10-32, wherein, The single side surface density of the negative active layer is 104 mg / 1540.25 mm 2 - 180 mg / 1540.25 mm 2 ; optionally 125 mg / 1540.25 mm 2 - 167 mg / 1540.25 mm 2 .

34. The battery cell of any one of claims 10-33, wherein, The compaction density of the negative active layer of the battery cell is 1.15 g / cm 3 ~ 1.36 g / cm 3 ; and optionally 1.25 g / cm 3 ~ 1.36 g / cm 3 .

35. The battery cell of any one of claims 10-34, wherein, The negative electrode active material comprises graphite.

36. The battery cell of claim 35, wherein, The graphite comprises composite graphite particles, the composite graphite particles comprising a bulk particle and a coating layer at least partially provided on the surface of the bulk particle, the bulk particle comprising artificial graphite, the coating layer comprising amorphous carbon, and the composite graphite particles comprising secondary particles.

37. The battery cell of claim 36, wherein, The mass content of amorphous carbon in the coating layer of the composite graphite particles is 2-5% based on the total mass of the composite graphite particles.

38. The battery cell of claim 36 or 37, wherein, The powder resistivity of the negative electrode active material is less than or equal to 0.04 Ω·cm.

39. The battery cell of any one of claims 36-38, wherein, The powder compaction density of the negative active material under 20000N pressure is 1.5g / cm 3 to 1.7g / cm 3 , optionally 1.55g / cm 3 to 1.65g / cm 3 .

40. The battery cell of any one of claims 10-39, wherein, The negative electrode active material further comprises a silicon-based material, the silicon-based material comprising at least one of silicon, a silicon oxide compound and a silicon-carbon composite; the mass content of silicon in the silicon-based material is 0.3-10% based on the total mass of the negative electrode active material, and optionally 1-6%.

41. The battery cell of any one of claims 10-40, wherein, The charge specific capacity of the negative electrode active material is 350-480 mAh / g.

42. The battery cell of any one of claims 10-41, wherein, The negative electrode active layer comprises a first negative electrode active material layer provided on the surface of the negative electrode current collector and a second negative electrode active material layer provided on the side of the first negative electrode active material layer away from the negative electrode current collector, the second negative electrode active material layer comprising composite graphite particles.

43. The battery cell of claim 42, wherein, The first negative electrode active material layer comprises one or more of composite graphite particles and natural graphite.

44. The battery cell of claim 42, wherein, The ratio of the thickness of the second negative electrode active material layer to the thickness of the first negative electrode active material layer is 3:7-7:

3.

45. The battery cell of any one of claims 42-44, wherein, The volume average particle size Dv501 of the negative electrode active material in the first negative electrode active material layer is 9.5-18.5 μm, and optionally 9.5-14.8 μm.

46. The battery cell of any one of claims 42-45, wherein, The volume average particle size Dv502 of the negative electrode active material in the second negative electrode active material layer is 7.8-14.3 μm, and optionally 7.8-12.8 μm.

47. The battery cell of any one of claims 1-46, wherein, The battery cell further comprises a separator film, the separator film comprises a porous base film and a functional layer provided on at least one side of the porous base film, the thickness of the porous base film is less than or equal to 12 μm, and optionally less than or equal to 9 μm.

48. The battery cell of claim 47, wherein, The porosity of the porous base film in the separator film is 20%-70%, and optionally 35%-60%.

49. The battery cell of either claim 47 or 48, wherein, The functional layer comprises a first functional layer provided on the negative electrode side of the porous base film and a second functional layer provided on the positive electrode side of the porous base film, the first functional layer comprises first inorganic particles, and the second functional layer comprises composite particles, the composite particles comprise second inorganic particles and a non-fluoropolymer, and the second inorganic particles in the composite particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles.

50. The battery cell of claim 49, wherein, The non-fluoropolymer particles comprise an acrylate copolymer.

51. The battery cell of any one of claims 1-50, wherein, The battery cell has a liquid injection coefficient of 2.4 g / Ah-3.1 g / Ah.

52. The battery cell according to any one of claims 1-51, further comprising an electrode terminal, the electrode assembly comprises a tab portion, and the tab portion is directly welded with the electrode terminal.

53. The battery cell of any one of claims 1-52, wherein, The battery cell has a charging time from 10% state of charge (SOC) to 80% state of charge (SOC) at 30°C of 6 min-15 min.

54. The battery cell of any one of claims 1-53, wherein, The battery cell has a winding structure, the thickness of the positive electrode current collector is less than or equal to 15 μm, and the thickness of the negative electrode current collector is less than or equal to 6 μm.

55. The battery cell of any one of claims 1-54, wherein, The battery cell has a volumetric energy density of 400 Wh / L-500 Wh / L.

56. A battery device, comprising: The battery device comprises at least one of a battery module, a battery pack, and an energy storage battery, and comprises the battery cell according to any one of claims 1-55.

57. An electrical device, comprising: The battery cell according to any one of claims 1-56. The battery cell according to any one of claims 1-56.

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