Battery cell, battery device, electric device, and energy storage device

Abstract

A battery cell, a battery device, an electric device, and an energy storage device. A positive electrode sheet of the battery cell comprises a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises first-type particles and second-type, the primary particle size of the first-type particles being greater than 180 nm and less than 900 nm, the primary particle size of the second-type particles being greater than or equal to 900 nm and less than or equal to 5 μm, and the average molar proportion of Mn in the second-type particles being less than an average molar proportion of Mn in the first-type particles. An electrolyte of the battery cell comprises an organic solvent, an electrolyte salt, and a first additive, wherein the first additive comprises one or more compounds having the structures represented by Formula I.

Description

Battery cells, battery packs, electrical devices, and energy storage devices Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a battery cell, battery device, power supply device, and energy storage 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 rapid development of electric vehicles and mobile electronic devices, the requirements for energy density and storage performance of battery cells are becoming increasingly stringent. How to maintain high energy density while simultaneously improving battery storage performance is a pressing technical challenge in current battery cell applications. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell with high energy density and excellent storage performance.

[0005] The first aspect of this application provides a battery cell comprising a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrodes. The positive electrode comprises a positive current collector and a positive electrode film layer disposed on at least one side of the current collector. The positive electrode film layer comprises a first type of particles and a second type of particles, both comprising lithium transition metal phosphate materials. The first type of particles has a primary particle size greater than 180 nm and less than 900 nm, and the second type of particles has a primary particle size greater than or equal to 900 nm and less than or equal to 5 μm. The average molar percentage of Mn in the second type of particles is less than the average molar percentage of Mn in the first type of particles. The molar percentage of Mn refers to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe. The electrolyte comprises an organic solvent, an electrolyte salt, and a first additive, wherein the first additive comprises one or more of the structures shown in Formula I.

[0006] R1, R2, R3, R4, R5, and R6 each independently include one or more of hydrogen, halogen, substituted or unsubstituted C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 alkoxy, C2-C6 alkenyl, C2-C6 alkynyl, cyano, fluorosulfonic acid, and C1-C6 alkylsulfonic acid, and at least one of R1, R2, R3, R4, R5, and R6 contains fluorine.

[0007] This application's embodiments improve the battery's energy density and rate performance by controlling the average Mn molar percentage of large-diameter particles to be lower than the average Mn molar percentage of relatively small-diameter particles. Simultaneously, by adding a first additive to the electrolyte, the impact of Mn dissolution from small-diameter particles with a relatively high Mn molar percentage on the SEI film is reduced, minimizing active lithium loss and improving the battery's storage performance and capacity. Through the synergistic design of the positive electrode active material and the electrolyte, the battery's energy density, capacity, and storage performance are improved.

[0008] In any embodiment, R1, R2, R3, R4, R5, and R6 each independently include one or more of hydrogen, halogen, substituted or unsubstituted C1-C4 alkyl, C1-C4 fluoroalkyl, C1-C4 alkoxy, C2-C4 alkenyl, C2-C4 alkynyl, cyano, fluorosulfonic acid, and C1-C4 alkylsulfonic acid, and at least one of R1, R2, R3, R4, R5, and R6 is fluorine.

[0009] In any embodiment, R1, R2, R3, R4, R5, and R6 each independently include one or more of hydrogen atoms and fluorine atoms, and at least one of R1, R2, R3, R4, R5, and R6 is fluorine.

[0010] Compared to long-chain substituents, short-chain substituents exhibit higher migration rates and interfacial affinity, enabling them to accumulate more rapidly and directionally at the electrode interface. The first additive with the aforementioned structure helps form a dense SEI film rich in LiF components and possessing excellent mechanical strength. This further reduces the damage to the SEI film caused by Mn leached from the first and / or second types of particles, minimizing lithium consumption during SEI film reconstruction and improving the battery's storage performance and capacity.

[0011] When fluorine atoms are directly bonded to the benzene ring, their extremely high electronegativity endows the molecule with a stronger electron-withdrawing ability, making it more prone to redox reactions at the electrode interface compared to fluorinated alkyl and fluorosulfonic acid groups. This facilitates the efficient construction of a stable SEI film. Furthermore, these fluorine-containing additives are more likely to generate LiF components during film formation. The resulting LiF-rich SEI film can significantly reduce the damage to the SEI film caused by Mn dissolved from first-type and / or second-type particles. On the other hand, it can effectively suppress the consumption of active lithium caused by SEI film reconstruction, thereby improving the battery's storage performance and capacity.

[0012] In any embodiment, the first additive includes One or more of them.

[0013] The first additive is within the above range, which facilitates the rapid formation of a dense SEI film rich in LiF components and with excellent mechanical strength, reduces the damage to the SEI film caused by Mn dissolved from the first type of particles and / or the second type of particles, reduces lithium consumption caused by rebuilding the SEI film, and improves the storage performance and capacity of the battery.

[0014] In any embodiment, the first additive includes One or more of them.

[0015] The first additive is within the above-mentioned range. It has a strong electron-withdrawing effect and high reactivity, and can easily and quickly form a dense SEI film rich in LiF components and with excellent mechanical strength. It reduces the damage of Mn dissolved from the first type of particles and / or the second type of particles to the SEI film, reduces the lithium consumption caused by rebuilding the SEI film, and improves the storage performance and capacity of the battery.

[0016] In any embodiment, the mass content of the first additive is 0.1%-10% based on the total mass of the electrolyte.

[0017] Controlling the mass content of the first additive in the electrolyte within the above-mentioned range is beneficial for improving the battery's storage performance while maintaining good capacity.

[0018] In any embodiment, the mass content of the first additive is 0.1%-5% based on the total mass of the electrolyte, and optionally 0.5%-2%.

[0019] By controlling the mass content of the first additive in the electrolyte within a suitable range, the first additive can achieve the purpose of generating a dense SEI film, reducing the impact of Mn dissolution on the SEI film, improving the storage performance and capacity of the battery, and also avoiding the adverse effects of excessively high content of the first additive on the ionic conductivity and viscosity of the electrolyte.

[0020] In any embodiment, the electrolyte further includes a second additive, which includes one or more of vinylene carbonate, fluorovinyl carbonate, succinate, adiponitrile, vinyl sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphate, and may be selected as one or more of vinyl sulfate and vinylene carbonate.

[0021] Adding a second additive to the electrolyte can simultaneously oxidize and decompose the electrolyte on the basis of the film formed by the first additive, which is conducive to the formation of a denser and more resilient SEI film. This reduces the damage to the SEI film caused by Mn dissolved from the first and / or second types of particles, and reduces the lithium consumption caused by rebuilding the SEI film, thereby improving the battery's capacity and storage performance.

[0022] In any embodiment, based on the total mass of the electrolyte, the mass content of the second additive is 0.1%-10%, optionally 0.1%-5%, and further optionally 0.5%-1%.

[0023] Controlling the mass content of the second additive in the electrolyte within a suitable range is beneficial for forming a denser and more resilient SEI, reducing the damage of Mn dissolved from the first and / or second types of particles to the SEI film, reducing the loss of active lithium, and enabling the battery to achieve a good balance between storage performance and capacity.

[0024] In any embodiment, the organic solvent includes carbonate solvents, which include one or more of ethylene carbonate, propylene carbonate, butene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0025] Electrolytes containing carbonate solvents have good viscosity, dissociation rate and conductivity, which are beneficial for comprehensively improving the fast charging performance of batteries.

[0026] In any embodiment, the organic solvent further includes a carboxylic acid ester solvent, which includes one or more of methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, and ethyl butyrate.

[0027] Electrolytes containing carboxylic acid ester solvents possess suitable viscosity, conductivity, and good dissociation rate and wettability, which is beneficial for improving the fast charging performance of batteries.

[0028] In any embodiment, based on the total mass of organic solvents in the electrolyte, the mass content of the carbonate solvent is 50%-100%, and the mass content of the carboxylic acid ester solvent is 0%-50%.

[0029] When the mass content of carbonate solvents and carboxylic acid ester solvents is within the above range, the electrolyte exhibits good conductivity, wettability, and chemical stability, which is beneficial for improving the fast-charging performance of the battery.

[0030] In any embodiment, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium difluorodioxalate phosphate (LiODFP), and lithium dioxalate borate (LiBOB).

[0031] In any embodiment, the concentration of the electrolyte salt is 0.8 mol / L to 1.2 mol / L.

[0032] In any embodiment, the average molar percentage of Mn in the first type of particles is 0.4-0.9, and can be optionally 0.5-0.9.

[0033] By controlling the average Mn molar ratio of the first type of particles within a suitable range, the first type of particles can have a high plateau capacity while also ensuring that the first type of particles have a certain conductivity. This is conducive to the first type of particles exerting their specific capacity and plateau capacity, achieving the purpose of providing capacity by the first type of particles, and improving the energy density of the battery.

[0034] In any embodiment, the average value of the Mn molar ratio of the second type of particles is 0-0.6, optionally 0-0.5, more preferably 0-0.1, and even more preferably 0.

[0035] Controlling the average molar ratio of Mn in the second type of particles within a suitable range can improve the conductivity of the second type of particles, enhance the overall conductivity of the material, and improve the rate performance of the battery.

[0036] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles is 0%-50%, optionally 0%-30%, more preferably 0%-10%, and even more preferably 0%.

[0037] Controlling the molar percentage of Mn in the second type of particles within a suitable range can further improve the conductivity of the second type of particles, alleviate the discharge polarization of the second type of particles, and help to further improve the rate performance of the battery. At the same time, it is beneficial to concentrate sufficient manganese elements in the first type of particles with small primary particle size, so that the first type of particles contribute more plateau capacity, improve the energy density of the battery, and is suitable for high-rate and high-energy-density batteries.

[0038] In any embodiment, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 20%-95%, optionally 20%-80%, more preferably 40%-60%, and / or the area ratio of the second type of particles is 5%-80%, optionally 15%-80%, more preferably 25%-60%.

[0039] When the area ratio of the first type of particles and the second type of particles is within a suitable range, it is possible to achieve particle size distribution, improve the powder compaction density of the material and the compaction density of the electrode sheet, and at the same time, it can give full play to the purpose of providing platform capacity for the first type of particles with relatively high manganese content, and also reduce the impact of the large-diameter second type of particles on the conductivity of the material, which is conducive to obtaining batteries with high energy density and excellent rate performance.

[0040] In any embodiment, the positive electrode film layer includes a third type of particles, the third type of particles including the lithium-containing transition metal phosphate material, the primary particle size of the third type of particles being greater than or equal to 50 nm and less than or equal to 180 nm, wherein, based on the total area of ​​the primary particles of the positive electrode film layer, the area ratio of the third type of particles is greater than or equal to 5% and less than or equal to 30%.

[0041] The third type of particles with a smaller primary particle size and appropriate area ratio can fill the pores between the first and second types of particles, making the material more tightly packed and further improving the powder compaction density of the material, which is beneficial for obtaining high energy density batteries.

[0042] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0%-12%, optionally 0%-8%, more preferably 0%-6%, and even more preferably 0%.

[0043] By controlling the molar percentage of Mn in the third type of particles within a suitable range, the possibility of side reactions between the third type of particles and the electrolyte and the occurrence of manganese dissolution can be reduced, thereby improving the cycle performance and storage performance of the battery, extending the battery's lifespan, and making the battery suitable for application scenarios with higher requirements for cycle performance and / or storage performance.

[0044] In any embodiment, the average Mn molar ratio of the third type of particles is 0-0.6, optionally 0-0.4, more preferably 0-0.2, and even more preferably 0.

[0045] Controlling the average molar ratio of Mn in the third type of particles within a suitable range can reduce the possibility of side reactions between the third type of particles and the electrolyte, as well as the occurrence of manganese dissolution, thereby improving the battery's capacity and storage performance.

[0046] In any embodiment, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 45%-85%, the area ratio of the second type of particles is 10%-40%, and the area ratio of the third type of particles is 5%-15%.

[0047] By controlling the area ratio of particles of different sizes within a suitable range, the contribution of the first type of particles with high manganese content to the energy density can be achieved. At the same time, the impact of the second type of large-diameter particles on the rate performance of the battery and the impact of the third type of small-diameter particles on the storage performance of the battery can be reduced. The battery can achieve a balance of high energy density, good storage performance and rate performance.

[0048] In any embodiment, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 45%-85%, the average molar ratio of Mn in the first type of particles is 0.5-0.9, and based on the total mass of the electrolyte, the mass content of the first additive is 0.1%-5%, and the mass content of the second additive is 0.1%-3%.

[0049] The battery structure described above can maintain good energy density while also taking into account battery capacity and storage performance.

[0050] In any embodiment, the general formula of the lithium-containing transition metal phosphate material of the first type of particles includes Li m1 Fe x1 Mn r1 P y1 O j1 Q1 q1 Wherein, 0.95≤m1≤1.15, x1>0, r1>0, 0.9≤x1+r1≤1, 0.95≤y1≤1, 3.5≤j1≤4, 0≤q1≤0.1, and Q1 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br; and / or, the general formula of the lithium-containing transition metal phosphate material of the second type of particles includes Li m2 Fe x2 Mn r2 P y2 O j2 Q2 q2 Wherein, 0.95≤m2≤1.15, x2>0, r2≥0, 0.9≤x2+r2≤1, 0.95≤y2≤1, 3.5≤j2≤4, 0≤q2≤0.1, and Q2 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

[0051] In any embodiment, the general formula of the lithium-containing transition metal phosphate material of the third type of particles includes Li m3 Fe x3 Mn r3 P y3 O j3 Q1 q3Wherein, 0.95≤m3≤1.15, x3>0, r3≥0, 0.9≤x3+r3≤1, 0.95≤y3≤1, 3.5≤j3≤4, 0≤q3≤0.1, and Q3 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

[0052] By selecting appropriate modifying elements Q1, Q2, and Q3, the lattice change rate of the material during lithium insertion / extraction can be improved, the structural stability of the material can be enhanced, the dissolution of manganese can be reduced, and the oxygen activity on the particle surface can be decreased, thereby increasing the energy density of the battery and reducing the interfacial side reactions between the material and the electrolyte during use, thus improving the capacity and storage performance of the material.

[0053] In any embodiment, the compaction density of the positive electrode sheet is 2.25 g / cm³. 3 -2.75g / cm 3 .

[0054] A compaction density of the positive electrode sheet within a suitable range is beneficial to improving the volumetric energy density of the battery.

[0055] In any embodiment, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which comprises one or more of the following: natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, ferric oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, sodium titanate, and sodium terephthalate.

[0056] A second aspect of this application provides a battery device comprising the battery cell provided in the first aspect of this application.

[0057] A third aspect of this application provides an electrical device, which includes the battery device provided in the second aspect of this application.

[0058] A fourth aspect of this application provides an energy storage device, which includes the battery device provided in the second aspect of this application. Attached Figure Description

[0059] Figure 1 is a longitudinal cross-sectional schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0060] Figure 2 is a transmission electron microscope image of the particles in the positive electrode film layer in Embodiment 1 of this application;

[0061] Figure 3 is a schematic diagram of a battery cell according to an embodiment of this application;

[0062] Figure 4 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 3;

[0063] Figure 5 is a schematic diagram of a battery module according to an embodiment of this application;

[0064] Figure 6 is a schematic diagram of a battery pack according to an embodiment of this application;

[0065] Figure 7 is an exploded view of the battery pack of one embodiment of this application shown in Figure 6;

[0066] Figure 8 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.

[0067] Reference numerals: 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 10 Positive electrode sheet; 110 Positive current collector; 120 Positive electrode film; 1210 Type I particles; 1220 Type II particles. Detailed Implementation

[0068] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, battery device, power consumption device, and energy storage 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.

[0069] 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.

[0070] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0071] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0072] 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 method may also include step (c), indicating 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.

[0073] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0074] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0075] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

[0076] The battery mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0077] A battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging. A battery cell can be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited to this. Figure 3 shows a cuboid battery cell 5 as an example.

[0078] A single battery cell includes electrode components and an electrolyte.

[0079] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0080] In some embodiments, as shown in FIG4, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. Electrode assemblies 52 are encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be adjusted as needed.

[0081] Electrode assemblies typically include positive and negative electrodes. The negative electrode is the electrode that absorbs or lithiates lithium ions during charging and releases or delithiates lithium during discharging. The positive electrode is the electrode that absorbs or delithiates lithium ions during charging and absorbs or lithiates lithium during discharging.

[0082] When there are multiple battery cells, they are connected in series, parallel, or mixed via a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, they are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed within the housing. In some embodiments, the housing can be part of the vehicle's chassis structure. For example, a portion of the housing can be at least part of the vehicle's floor, or a portion of the housing can be at least part of the vehicle's crossbeams and longitudinal beams.

[0083] In some implementations, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0084] In some implementations, individual battery cells can be assembled into a battery module. The number of battery cells in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 5 is a schematic diagram of a battery module 4 as an example. As shown in Figure 5, 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 arbitrary manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0085] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0086] 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 adjusted according to the application and capacity of the battery pack.

[0087] Figures 6 and 7 are schematic diagrams of a battery pack 1 as an example. As shown in Figures 6 and 7, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

[0088] The positive electrode active material is one of the decisive factors in the performance of a single battery cell. Lithium manganese iron phosphate (LMP), as a novel material further developed from lithium iron phosphate, combines the advantages of manganese and iron, offering two voltage plateaus at 4.1V and 3.4V, respectively, providing a certain platform capacity. However, in current research and applications, LMP still suffers from low compaction density and has not yet demonstrated the potential advantage of high energy density. Furthermore, the trivalent manganese ions in LMP exhibit the Jan Taylor effect, transforming into tetravalent manganese ions. These highly reactive tetravalent manganese ions readily react with the electrolyte to transform into divalent manganese ions. These divalent manganese ions further dissolve in the electrolyte and are reduced and precipitated at the negative electrode, damaging the SEI film. This results in more active lithium being consumed during SEI film repair, thus affecting the battery's storage life and capacity. Therefore, obtaining high energy density batteries while simultaneously maintaining good storage performance and capacity has become a key research focus.

[0089] Based on this, this application proposes a battery cell, which includes a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the current collector. The positive electrode film layer includes a first type of particles and a second type of particles, both of which are lithium-containing transition metal phosphate materials. The first type of particles has a primary particle size greater than 180 nm and less than 900 nm, and the second type of particles has a primary particle size greater than or equal to 900 nm and less than or equal to 5 μm. The average molar percentage of Mn in the second type of particles is less than the average molar percentage of Mn in the first type of particles. The molar percentage of Mn refers to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe. The electrolyte includes an organic solvent, an electrolyte salt, and a first additive, wherein the first additive includes one or more of the structures shown in Formula I.

[0090] R1, R2, R3, R4, R5, and R6 each independently include one or more of hydrogen, halogen, substituted or unsubstituted C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 alkoxy, C2-C6 alkenyl, C2-C6 alkynyl, cyano, fluorosulfonic acid, and C1-C6 alkylsulfonic acid, and at least one of R1, R2, R3, R4, R5, and R6 contains fluorine.

[0091] As shown in Figure 1, the positive electrode 10 includes a positive current collector 110 and a positive electrode film 120 disposed on at least one side of the positive current collector. The positive electrode film includes first type particles 1210 and second type particles 1220.

[0092] In this paper, the term "primary particle size" refers to the particle size of a primary particle.

[0093] Lithium-containing transition metal phosphates refer to phosphate materials containing lithium and transition metal elements, and can be detected by any method known in the art. For example, they can be detected by combining X-ray diffraction (XRD) with energy dispersive spectroscopy (EDS) or inductively coupled plasma mass spectrometry (ICP-MS). As examples, lithium-containing transition metal phosphates include, but are not limited to, lithium iron phosphate, lithium manganese iron phosphate, and their doped materials.

[0094] Primary particles refer to individual particles that can be distinguished after being identified by general-purpose software (e.g., SpectrumSee; Avizo 3D) in transmission electron microscopy (TEM) images, and / or individual particles that can be distinguished after manual identification or manual-assisted calibration. Specifically, in this paper, to identify primary particles, the particles contained in the positive electrode film were enriched and / or dispersed, and then imaged under a TEM. The resulting images can be directly identified using software (based on parameters such as grayscale and / or contrast / brightness), and the individual particles that are distinguished after identification are primary particles. Alternatively, the images can be directly identified manually, and the individual particles that are distinguished after identification are primary particles. Another method is to directly identify the images using a combination of software and manual calibration, and the individual particles that are identified and confirmed to be distinguishable are primary particles. More specifically, particles that form independent, clearly distinguishable boundaries in the TEM field of view can be directly identified as individual particles through software or manual identification. However, some particles, although dispersed, exhibit a certain degree of adhesion and stacking in the TEM field of view. For particles that are stuck together or stacked, those identified as individual particles by software (based on parameters such as grayscale / contrast / brightness) are counted as first-order particles. For more precise analysis, for particles that are stuck together or stacked to some extent under a transmission electron microscope (TEM) field of view, after being identified as individual particles by software based on parameters such as grayscale / contrast / brightness, potentially misidentified particles are manually calibrated according to certain rules. The calibrated, distinguishable individual particles are then counted as first-order particles. If there are inconsistencies in the manual calibration results, 3, 5, or 7 people, unaware of each other's knowledge of the same imaging result, can individually calibrate according to the rules illustrated below. The results are then statistically calculated, and the result obtained in this way is counted as the number of first-order particles. The following example, using the transmission electron microscope (TEM) image of the positive electrode film layer in Example 1 (Figure 2), further illustrates the distinction during the primary particle number and area counting process. Figure 2-a is the original TEM image, Figure 2-b is the software-recognized image, and Figure 2-c is an example of software and / or manual identification of independent particles, adhered particles, and stacked particles in Figure 2-a. Particles 1 and 2 are distinguishable independent particles, designated as primary particles 1 and 2, respectively. Particles 3 and 4 in Figure 2-c are adhered; particles 5, 6, and 7 are also adhered, and after software or manual identification, they are determined to be primary particles 3, 4, 5, 6, and 7, respectively. Particles 8 and 9, which are stacked together, are ultimately identified as primary particles 8 and 9, rather than being classified as a single particle. Figure 2-d is another example of software and / or manual identification of the stacked particles in Figure 2-a, where the stacked particles 10-14 are ultimately identified as primary particles 10, 11, 12, 13 and primary particle 14, instead of identifying the entire stack of particles as a single particle.When selecting the field of view for transmission electron microscopy, the field of view in which the number of stacked particles accounts for less than 20% of the total number of particles (individual particles, adherent particles, and the total number of stacked particles) can be selected for statistical analysis. Alternatively, the field of view in which the number of stacked particles accounts for less than 15% of the total number of particles (individual particles, adherent particles, and the total number of stacked particles) can be selected for statistical analysis. Furthermore, the field of view in which the number of stacked particles accounts for less than 10% of the total number of particles (individual particles, adherent particles, and the total number of stacked particles) can be selected for statistical analysis.

[0095] The average value of the Mn molar ratio of the first type of particles and the average value of the Mn molar ratio of the second type of particles can be tested using methods and equipment known in the art, for example as follows: Disassemble the battery to obtain the positive electrode sheet, peel off the positive electrode film layer of the positive electrode sheet, thoroughly wash the positive electrode film layer with acetone to remove the binder and dispersant in the positive electrode film layer, filter and dry to obtain powder. Take 0.05g of the uniformly mixed powder and dissolve it in 40ml of anhydrous ethanol. Then add an appropriate amount of dispersant and stir until a suspension is obtained. Take 2ml of the suspension and 2ml of anhydrous ethanol and mix them together. Then sonicate the mixture at a power of 480W for 5min. Take an appropriate amount of the middle layer suspension for transmission electron microscopy (TEM). According to the definition of primary particles mentioned above, calculate the projection area of ​​each primary particle in the TEM image, which is the cross-sectional area S of the primary particle. Use the equivalent circle method to obtain the equivalent circle diameter of the primary particle, which is the primary particle diameter d. In the above statistical process of primary particles and their primary particle diameters, primary particles with a primary particle diameter less than 50nm and greater than 5μm are not included in the statistical range (i.e., primary particles with a primary particle diameter greater than or equal to 50nm and less than or equal to 5μm are considered valid particles). Simultaneously, EDS point scanning can be used to test the molar content of Mn and Fe in each effective particle in the transmission electron microscope (TEM) image. This allows calculation of the molar percentage of Mn (X) in each effective particle (the molar percentage of Mn refers to the content of the number of moles of Mn relative to the total number of moles of Mn and Fe). The test point is the middle of the transmission surface of each particle. Multiple TEM and EDS tests are performed in different test areas, testing the cross-sectional area S, primary particle size d, and molar percentage of Mn X of at least 500 effective particles. The obtained effective particles are then numbered from smallest to largest primary particle size as 1, 2, 3, 4, 5…n, for a total of n particles. The m-th particle has a primary diameter less than or equal to 180 nm, the (m+1)-th particle has a primary diameter greater than 180 nm, the (k-1)-th particle has a primary diameter less than 900 nm, and the k-th particle has a primary diameter greater than or equal to 900 nm. Therefore, particles (m+1) to (k-1)-th are classified as Class I particles, and particles (k-n)-th are classified as Class II particles. When the primary diameter of particle number 1 is greater than 180 nm, i.e., particles numbered 1 to (k-1)-th are Class I particles, and particles (k-n)-th are Class II particles, m is 0. The formula for calculating the average molar percentage of Mn in Class I particles is:

[0096] The formula for calculating the average molar percentage of Mn in the second type of particles is as follows:

[0097] Where Xi represents the molar percentage of Mn in particle i, and Si represents the cross-sectional area of ​​particle i.

[0098] The types and quality of organic solvents, electrolyte salts, and additives 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 gas chromatography, ion chromatography, gas chromatography-mass spectrometry, liquid chromatography, ultraviolet spectrophotometry, and ultraviolet-visible spectrophotometry. Exemplarily, 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 current chromatogram of each organic compound is obtained. The peak positions in the chromatogram 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.

[0099] In this article, the term "C" 1- "C6 alkyl" refers to an unbranched or branched alkyl group having 1 to 6 carbon atoms, including but not limited to one or more of the following: methyl, ethyl, n-propyl, 1-methylethyl (isopropyl), n-butyl, n-pentyl, and n-hexyl.

[0100] In this article, the term "C" 1- "C6 fluoroalkyl" refers to an unbranched or branched alkyl group having 1-6 carbon atoms, in which at least one hydrogen atom is replaced by a fluorine atom.

[0101] In this article, when the aforementioned C 1- When a C6 alkyl group contains an oxygen atom, it can be C6. 1- C6 alkoxy groups, including but not limited to: methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, cyclopentoxy, and cyclohexyloxy.

[0102] In this document, the term "C2-C6 alkenyl" can refer to cyclic alkenyl or chain alkenyl. Chain alkenyl can be linear or branched, including but not limited to: vinyl, allyl, isopropenyl, pentenyl, and cyclohexenyl.

[0103] In this document, the term "C2-C6 alkynyl" can refer to either cyclic alkynyl or chain alkynyl. Chain alkynyl can be either straight-chain or branched, including but not limited to: ethynyl, propynyl, isopropynyl, pentylyl, and cyclohexynyl.

[0104] In this article, the term "cyano" refers to -CN.

[0105] In this paper, the term "fluorosulfonic acid group" refers to a group in which the hydroxyl group (-SO3H) is replaced by a fluorine atom, with the structural formula -SO2F.

[0106] In this paper, the term "C1-C6 alkyl sulfonate group" refers to a group in which the hydroxyl group (-SO3H) is replaced by a C1-C6 alkyl group, with the structural formula -SO2R', where R' is a C1-C6 alkyl group.

[0107] The positive electrode active material comprises two types of particles with different primary particle sizes. This allows the particles of different sizes to work together to fill gaps, resulting in a denser particle packing and increased electrode compaction density, thereby improving the battery's energy density. However, the second type of particles has a relatively large primary particle size, which lengthens the migration path of lithium ions within the particles. This leads to increased discharge polarization and decreased specific capacity in the second type of particles, affecting the material's specific capacity utilization and kinetic performance, and consequently, the battery's energy density and rate performance. The molar ratio of Mn in the particles affects their conductivity. This application improves the conductivity of the second type of particles with larger primary particle sizes by controlling the average Mn molar ratio of the second type of particles to be lower than the average Mn molar ratio of the first type of particles with smaller primary particle sizes. This alleviates the discharge polarization of the second type of particles, which is beneficial for the material's specific capacity utilization and kinetic performance, thus improving the battery's energy density and rate performance. Simultaneously, the relatively high Mn molar ratio in the first type of particles with smaller primary particle sizes can maintain good conductivity while increasing the plateau capacity of the first type of particles, which is beneficial for improving the battery's energy density.

[0108] However, as mentioned earlier, lithium manganese iron phosphate exhibits Mn leaching, which damages the SEI film, harms the active lithium, and affects the battery's storage performance and capacity. Addressing Mn leaching by adjusting the particle size and molar percentage of the active material requires a lower Mn molar percentage in the primary particle type (smaller particles) compared to the primary particle type (larger particles), contradicting the previously discussed methods for improving energy density and rate performance. Based on this, this application starts with the electrolyte and adds a first additive with large π bonds to the electrolyte. This additive interacts with the negative electrode active material (e.g., graphite, silicon-carbon mixture, etc.) in a π-π manner, thereby enriching itself on the surface of the negative electrode active material. This helps to form a dense SEI film containing LiF with high mechanical strength after the negative electrode is reduced and decomposed. It reduces the damage to the SEI film caused by Mn dissolved from the first and / or second types of particles, reduces the lithium consumption caused by rebuilding the SEI film, and improves the storage performance and capacity of the battery. At the same time, because the first additive containing large π bonds interacts with the negative electrode active material in a π-π manner, it improves the wettability of the electrolyte to the negative electrode side, improves the interfacial contact between the electrolyte and the negative electrode active material, reduces interfacial impedance, and is beneficial to improving the kinetic performance of the battery.

[0109] In summary, this application improves the energy density and rate performance of the battery by controlling the average Mn molar ratio of large-diameter particles to be lower than the average Mn molar ratio of relatively small-diameter particles. Simultaneously, by adding a first additive to the electrolyte, the impact of Mn dissolution from small-diameter particles with a relatively high Mn molar ratio on the SEI film is reduced, minimizing active lithium loss and improving the battery's storage performance and capacity. Through the synergistic design of the positive electrode active material and the electrolyte, the energy density, capacity, and storage performance of the battery are improved.

[0110] In some embodiments, R1, R2, R3, R4, R5, and R6 each independently include one or more of hydrogen, halogen, substituted or unsubstituted C1-C4 alkyl, C1-C4 fluoroalkyl, C1-C4 alkoxy, C2-C4 alkenyl, C2-C4 alkynyl, cyano, fluorosulfonic acid, and C1-C4 alkylsulfonic acid, and at least one of R1, R2, R3, R4, R5, and R6 is fluorine.

[0111] In some embodiments, R1, R2, R3, R4, R5, and R6 each independently include one or more of hydrogen atoms and fluorine atoms, and at least one of R1, R2, R3, R4, R5, and R6 is fluorine.

[0112] Compared to long-chain substituents, short-chain substituents exhibit higher migration rates and interfacial affinity, enabling them to accumulate more rapidly and directionally at the electrode interface. The first additive with the aforementioned structure helps form a dense SEI film rich in LiF components and possessing excellent mechanical strength. This further reduces the damage to the SEI film caused by Mn leached from the first and / or second types of particles, minimizing lithium consumption during SEI film reconstruction and improving the battery's storage performance and capacity.

[0113] When fluorine atoms are directly bonded to the benzene ring, their extremely high electronegativity endows the molecule with a stronger electron-withdrawing ability, making it more prone to redox reactions at the electrode interface compared to fluorinated alkyl and fluorosulfonic acid groups. This facilitates the efficient construction of a stable SEI film. Furthermore, these fluorine-containing additives are more likely to generate LiF components during film formation. The resulting LiF-rich SEI film can significantly reduce the damage to the SEI film caused by Mn dissolved from first-type and / or second-type particles. On the other hand, it can effectively suppress the consumption of active lithium caused by SEI film reconstruction, thereby improving the battery's storage performance and capacity.

[0114] In some embodiments, the first additive includes One or more of them.

[0115] The first additive is within the above range, which facilitates the rapid formation of a dense SEI film rich in LiF components and with excellent mechanical strength, reduces the damage to the SEI film caused by Mn dissolved from the first type of particles and / or the second type of particles, reduces lithium consumption caused by rebuilding the SEI film, and improves the storage performance and capacity of the battery.

[0116] In some embodiments, the first additive includes One or more of them.

[0117] The first additive is within the above-mentioned range. It has a strong electron-withdrawing effect and high reactivity, and can easily and quickly form a dense SEI film rich in LiF components and with excellent mechanical strength. It reduces the damage of Mn dissolved from the first type of particles and / or the second type of particles to the SEI film, reduces the lithium consumption caused by rebuilding the SEI film, and improves the storage performance and capacity of the battery.

[0118] In some embodiments, the mass content of the first additive is 0.1%-10% based on the total mass of the electrolyte.

[0119] Based on the total mass of the electrolyte, the mass content of the first 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 organic solvents, electrolyte salts, and additives 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 membrane, the mass content of the additive in the electrolyte may be slightly lower than the initial mass content of the additive added to the electrolyte.

[0120] In some embodiments, based on the total mass of the electrolyte, the mass content of the first additive can be selected as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value range between the two.

[0121] Controlling the mass content of the first additive in the electrolyte within the above-mentioned range is beneficial for improving the battery's storage performance while maintaining good capacity.

[0122] In some embodiments, the mass content of the first additive is 0.1%-5% based on the total mass of the electrolyte, optionally 0.5%-2%.

[0123] Excessive amounts of the first additive can negatively affect the ion migration rate and viscosity of the electrolyte, thus deteriorating its kinetic properties.

[0124] By controlling the mass content of the first additive in the electrolyte within a suitable range, the first additive can achieve the purpose of generating a dense SEI film, reducing the impact of Mn dissolution on the SEI film, improving the storage performance and capacity of the battery, and also avoiding the adverse effects of excessively high content of the first additive on the ionic conductivity and viscosity of the electrolyte.

[0125] This helps reduce the impedance of the positive electrode side and the separator, enabling the battery to further improve its storage performance and capacity while maintaining good kinetic performance.

[0126] In some embodiments, the electrolyte further includes a second additive, which includes one or more of vinylene carbonate, fluorovinyl carbonate, succinate, adiponitrile, vinyl sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphate, and may be selected from one or more of vinyl sulfate and vinylene carbonate.

[0127] Adding a second additive to the electrolyte can simultaneously oxidize and decompose the electrolyte on the basis of the film formed by the first additive, which is conducive to the formation of a denser and more resilient SEI film. This reduces the damage to the SEI film caused by Mn dissolved from the first and / or second types of particles, and reduces the lithium consumption caused by rebuilding the SEI film, thereby improving the battery's capacity and storage performance.

[0128] In some embodiments, the mass content of the second additive is 0.1%-10% based on the total mass of the electrolyte, optionally 0.1%-5%, and further optionally 0.5%-1%.

[0129] The mass content of the second additive in the electrolyte can be obtained by referring to the mass content test of the first additive in the electrolyte mentioned above. It should be understood that, since the additive in the electrolyte will be consumed during formation and cycling to generate relevant components in the SEI film, the mass content of the additive in the electrolyte may be slightly lower than the initial mass content of the additive added to the electrolyte.

[0130] In some embodiments, based on the total mass of the electrolyte, the mass content of the second additive can be selected as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value range between the two.

[0131] Controlling the mass content of the second additive in the electrolyte within a suitable range is beneficial for forming a denser and more resilient SEI, reducing the damage of Mn dissolved from the first and / or second types of particles to the SEI film, reducing the loss of active lithium, and enabling the battery to achieve a good balance between storage performance and capacity.

[0132] In some embodiments, the organic solvent includes carbonate solvents, which include one or more of ethylene carbonate, propylene carbonate, butene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0133] Electrolytes containing carbonate solvents have good viscosity, dissociation rate and conductivity, which are beneficial for comprehensively improving the fast charging performance of batteries.

[0134] In some embodiments, the organic solvent further includes carboxylic acid ester solvents, including one or more of methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, and ethyl butyrate.

[0135] Electrolytes containing carboxylic acid ester solvents possess suitable viscosity, conductivity, and good dissociation rate and wettability, which is beneficial for improving the fast charging performance of batteries.

[0136] In some embodiments, the carbonate solvent content is 50%-100% and the carboxylic acid ester solvent content is 0%-50% based on the total mass of organic solvents in the electrolyte.

[0137] In some embodiments, the mass content of the carbonate solvent can be selected as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or any range between the two, based on the total mass of the organic solvent in the electrolyte.

[0138] In some embodiments, the mass content of the carboxylic acid ester solvent can be selected as 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any range between the two, based on the total mass of the organic solvent in the electrolyte.

[0139] When the mass content of carbonate solvents and carboxylic acid ester solvents is within the above range, the electrolyte exhibits good conductivity, wettability, and chemical stability, which is beneficial for improving the fast-charging performance of the battery.

[0140] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium difluorodioxalate phosphate (LiODFP), and lithium dioxalate borate (LiBOB).

[0141] In some embodiments, the concentration of the electrolyte salt is 0.8 mol / L to 1.2 mol / L.

[0142] In some embodiments, the concentration of the electrolyte salt can be selected as 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, or any value range between the two.

[0143] In some implementations, the average molar percentage of Mn in the first type of particles is 0.4-0.9, and optionally 0.5-0.9.

[0144] In some embodiments, the average value of the molar percentage of Mn in the first type of particles can be selected as 0.4, 0.45, 0.50, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or any value range between the two.

[0145] By controlling the average Mn molar ratio of the first type of particles within a suitable range, the first type of particles can have a high plateau capacity while also ensuring that the first type of particles have a certain conductivity. This is conducive to the first type of particles exerting their specific capacity and plateau capacity, achieving the purpose of providing capacity by the first type of particles, and improving the energy density of the battery.

[0146] In some embodiments, the average Mn molar ratio of the second type of particles is 0-0.6, optionally 0-0.5, more preferably 0-0.1, and even more preferably 0.

[0147] In some embodiments, the average value of the Mn molar ratio of the second type of particles can be selected as 0, 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.6, or any value range between the two.

[0148] Controlling the average molar ratio of Mn in the second type of particles within a suitable range can improve the conductivity of the second type of particles, enhance the overall conductivity of the material, and improve the rate performance of the battery.

[0149] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles is 0%-50%, optionally 0%-30%, more preferably 0%-10%, and even more preferably 0%.

[0150] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles can be selected as 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.75%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or 13%. 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or any range of two.

[0151] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the secondary particles can be tested using methods and equipment known in the art, as exemplified below: Referring to the aforementioned test method for averaging the Mn molar percentage of the secondary particles, the cross-sectional area S and the molar percentage X of Mn for each particle are determined.

[0152] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the formula for calculating the molar percentage of Mn in the secondary particles is as follows:

[0153] Where Xi and Xj represent the molar percentage of Mn in particles numbered i and j, respectively, and Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0154] Controlling the molar percentage of Mn in the second type of particles within a suitable range can further improve the conductivity of the second type of particles, alleviate the discharge polarization of the second type of particles, and help to further improve the rate performance of the battery. At the same time, it is beneficial to concentrate sufficient manganese elements in the first type of particles with small primary particle size, so that the first type of particles contribute more plateau capacity, improve the energy density of the battery, and is suitable for high-rate and high-energy-density batteries.

[0155] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the first type of particles is 20%-95%, optionally 20%-80%, more preferably 40%-60%, and / or the area ratio of the second type of particles is 5%-80%, optionally 15%-80%, more preferably 25%-60%.

[0156] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the first type of particles can be selected as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any value range between the two.

[0157] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the second type of particles can be selected as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any value range between the two.

[0158] The method for testing the area ratio of the first type of particles and the area ratio of the second type of particles can be performed using methods and equipment known in the art, as exemplified below: Referring to the aforementioned method for testing the average value of the Mn molar ratio of the second type of particles, the cross-sectional area S of each particle is determined.

[0159] The formula for calculating the area ratio of the first type of particles is:

[0160] The formula for calculating the area ratio of the second type of particles is:

[0161] Where Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0162] When the area ratio of the first type of particles and the second type of particles is within a suitable range, it is possible to achieve particle size distribution, improve the powder compaction density of the material and the compaction density of the electrode sheet, and at the same time, it can give full play to the purpose of providing platform capacity for the first type of particles with relatively high manganese content, and also reduce the impact of the large-diameter second type of particles on the conductivity of the material, which is conducive to obtaining batteries with high energy density and excellent rate performance.

[0163] In some embodiments, the positive electrode film layer includes a third type of particles, which includes the lithium-containing transition metal phosphate material. The primary particle size of the third type of particles is greater than or equal to 50 nm and less than or equal to 180 nm. The area of ​​the third type of particles accounts for more than or equal to 5% and less than or equal to 30% based on the total area of ​​the primary particles of the positive electrode film layer.

[0164] In this paper, the third type of particle is a primary particle.

[0165] The determination of the third type of particles and the test method for their area proportion can be carried out using methods and equipment known in the art, as exemplified below: Referring to the aforementioned test method for the average value of the Mn molar proportion of the second type of particles, the first to the mth particles are defined as the third type of particles. The formula for calculating the area proportion of the third type of particles is then:

[0166] Where Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0167] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the third type of particles can be selected as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any value range between the two.

[0168] The third type of particles with a smaller primary particle size and appropriate area ratio can fill the pores between the first and second types of particles, making the material more tightly packed and further improving the powder compaction density of the material, which is beneficial for obtaining high energy density batteries.

[0169] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0%-12%, optionally 0%-8%, more preferably 0%-6%, and even more preferably 0%.

[0170] By controlling the molar percentage of Mn in the third type of particles within a suitable range, the possibility of side reactions between the third type of particles and the electrolyte and the occurrence of manganese dissolution can be reduced, thereby improving the cycle performance and storage performance of the battery, extending the battery's lifespan, and making the battery suitable for application scenarios with higher requirements for cycle performance and / or storage performance.

[0171] In some embodiments, the average molar percentage of Mn in the third type of particles is less than the average molar percentage of Mn in the first type of particles.

[0172] The test method for the average Mn molar ratio of the third type of particles is the same as the test method for the average Mn molar ratio of the second type of particles.

[0173] The formula for calculating the average molar percentage of Mn in the third type of particles is as follows:

[0174] Where Xi represents the molar percentage of Mn in particle i, and Si represents the cross-sectional area of ​​particle i.

[0175] As mentioned above, ultra-small particle size type III particles can further improve the powder compaction density of materials. However, ultra-small particle size type III particles have a large specific surface area and significantly increased surface activity. They are more likely to come into contact with electrolyte and undergo side reactions, exacerbating manganese dissolution and thus affecting the storage performance and capacity of the battery.

[0176] By controlling the average Mn molar ratio of the third type of particles to be less than the average Mn molar ratio of the first type of particles, it is beneficial to reduce the side reactions between the third type of particles and the electrolyte and the degree of manganese dissolution. This not only improves the energy density of the battery, but also improves the battery capacity and storage performance, and extends the battery's lifespan.

[0177] In some embodiments, the average Mn molar percentage of the third type of particles is 0-0.6, optionally 0-0.4, more preferably 0-0.2, and even more preferably 0.

[0178] In some embodiments, the average value of the Mn molar ratio of the third type of particles can be selected as 0, 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.6, or any value range between the two.

[0179] Controlling the average molar ratio of Mn in the third type of particles within a suitable range can reduce the possibility of side reactions between the third type of particles and the electrolyte, as well as the occurrence of manganese dissolution, thereby improving the battery's capacity and storage performance.

[0180] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the first type of particles is 45%-85%, the area ratio of the second type of particles is 10%-40%, and the area ratio of the third type of particles is 5%-15%.

[0181] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the first type of particles can be selected as 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or any value range between the two.

[0182] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the second type of particles can be selected as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or any value range between the two.

[0183] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the third type of particles can be selected as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any value range between the two.

[0184] By controlling the area ratio of particles of different sizes within a suitable range, the contribution of the first type of particles with high manganese content to the energy density can be achieved. At the same time, the impact of the second type of large-diameter particles on the rate performance of the battery and the impact of the third type of small-diameter particles on the storage performance of the battery can be reduced. The battery can achieve a balance of high energy density, good storage performance and rate performance.

[0185] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 45%-85%, the average molar ratio of Mn in the first type of particles is 0.5-0.9, and based on the total mass of the electrolyte, the mass content of the first additive is 0.1%-5%, and the mass content of the second additive is 0.1%-3%.

[0186] The battery structure described above can maintain good energy density while also taking into account battery capacity and storage performance.

[0187] In some embodiments, the general formula of the lithium-containing transition metal phosphate material of the first type of particles includes Li m1 Fe x1Mn r1 P y1 O j1 Q1 q1 Wherein, 0.95≤m1≤1.15, x1>0, r1>0, 0.9≤x1+r1≤1, 0.95≤y1≤1, 3.5≤j1≤4, 0≤q1≤0.1, and Q1 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br; and / or, the general formula of the lithium-containing transition metal phosphate material of the second type of particles includes Li m2 Fe x2 Mn r2 P y2 O j2 Q2 q2 Wherein, 0.95≤m2≤1.15, x2>0, r2≥0, 0.9≤x2+r2≤1, 0.95≤y2≤1, 3.5≤j2≤4, 0≤q2≤0.1, and Q2 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

[0188] In some embodiments, the general formula of the lithium-containing transition metal phosphate material of the third type of particles includes Li m3 Fe x3 Mn r3 P y3 O j3 Q1 q3 Wherein, 0.95≤m3≤1.15, x3>0, r3≥0, 0.9≤x3+r3≤1, 0.95≤y3≤1, 3.5≤j3≤4, 0≤q3≤0.1, and Q3 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

[0189] In some implementations, m1, m2 and m3 can each independently be 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, 1.15 or any range between two of them.

[0190] In some implementations, x1+r1, x2+r2 and x3+r3 can each independently be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0 or any range between two of them.

[0191] In some implementations, y1, y2, and y3 can each independently be a range of values ​​from 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, to any two of these values.

[0192] In some implementations, j1, j2, and j3 can each independently be a range of values ​​from 3.5, 3.6, 3.7, 3.8, 3.9, 4, to any two of them.

[0193] In some implementations, q1, q2, and q3 can each independently be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any value range between two of them.

[0194] By selecting appropriate modifying elements Q1, Q2, and Q3, the lattice change rate of the material during lithium insertion / extraction can be improved, the structural stability of the material can be enhanced, the dissolution of manganese can be reduced, and the oxygen activity on the particle surface can be decreased, thereby increasing the energy density of the battery and reducing the interfacial side reactions between the material and the electrolyte during use, thus improving the capacity and storage performance of the material.

[0195] In this paper, the modifying elements Q1, Q2, and Q3 can exist in the lithium-containing transition metal phosphate material as doping elements, or in the coating layer of the material as coating elements.

[0196] In some embodiments, the compaction density of the positive electrode sheet is 2.25 g / cm³. 3 -2.75g / cm 3 .

[0197] The compaction density of the positive electrode sheet can be tested using methods known in the art. As an example, a positive electrode sheet test sample with area S is weighed using an electronic balance, and the weight is denoted as W. The thickness T of the positive electrode sheet is measured using a micrometer. Then, the compaction density of the positive electrode sheet is PD = W / (T × S).

[0198] In some embodiments, the compaction density of the positive electrode sheet is 2.25 g / cm³. 3 2.3g / cm 3 2.35g / cm 3 2.4g / cm 3 2.45g / cm 3 2.5g / cm 3 2.55g / cm 3 2.6g / cm 3 2.65g / cm 3 2.7g / cm 3 2.75g / cm 3Or the range of values ​​between any two.

[0199] A compaction density of the positive electrode sheet within a suitable range is beneficial to improving the volumetric energy density of the battery.

[0200] In some implementations, as an example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0201] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. This application does not impose any particular limitation on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, conductive polymers, metal powders, and carbon nanofibers.

[0202] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose any particular limitation on the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0203] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. An example of a metal material may be at least one selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. An example of a polymer substrate may be at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0204] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0205] [Negative electrode plate]

[0206] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0207] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0208] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which comprises one or more of the following: natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, ferric oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, sodium titanate, and sodium terephthalate.

[0209] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0210] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0211] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0212] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0213] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0214] A second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0215] In addition, this application also provides an electrical device that uses a battery as a power source, the electrical device including at least one of the battery cell, battery module, or battery pack provided in 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.

[0216] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0217] Figure 8 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.

[0218] 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.

[0219] This application also provides an energy storage device that uses a battery as a power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system.

[0220] Example

[0221] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0222] Table 1. Relevant parameters and sources of lithium-containing transition metal phosphate materials.

[0223] I. Preparation Method

[0224] Example 1

[0225] (1) Preparation of positive electrode sheet

[0226] LiFe 0.37 Mn0.62 Ti 0.005 PO4, LiFe 0.99 Ti 0.005 PO4 (BP-LFP-01) was mixed at a mass ratio of 70%:30% to obtain a positive electrode active material. The above-mentioned mixed positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride were mixed at a weight percentage of 96:1.5:2.5 and N-methylpyrrolidone was added. After thorough mixing, stirring, and dispersion, a positive electrode slurry was prepared.

[0227] Adjust the viscosity of the thoroughly mixed slurry to 8000 mPa·s-20000 mPa·s until the slurry does not separate into layers. Then, use a double-sided, double-control coating device to apply the slurry at a rate of 420 mg / 1540 mm. 2 The coating is applied to the surface of the substrate aluminum foil, and then dried, cold-pressed, slit, and sheeted to finally obtain the positive electrode sheet.

[0228] Particle size was statistically analyzed in the cross-section of the positive electrode sheet. Particles with a primary diameter greater than 180 nm and less than 900 nm were classified as Class I particles, particles with a primary diameter greater than or equal to 900 nm and less than or equal to 5 μm were classified as Class II particles, and particles with a primary diameter between 50 nm and 180 nm were classified as Class III particles. The average area ratio and Mn molar ratio of each type of particle were characterized according to the characterization method described in the paper.

[0229] (2) Preparation of negative electrode sheet

[0230] Artificial graphite, conductive carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed evenly in a weight percentage of 95:1.0:2.0:2.0, and deionized water was added. After stirring and dispersing, a negative electrode slurry was obtained. The negative electrode slurry was then mixed at a concentration of 211 mg / 1540 mm. 2 The negative electrode sheet is obtained by coating the copper foil substrate, drying, cold pressing, slitting, and sheet forming.

[0231] (3) Separating membrane

[0232] Polypropylene film is used as the separator.

[0233] (4) Electrolyte

[0234] In an argon-atmospheric glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed thoroughly in a mass ratio of 30:50:20, and then the first and second additives are added. The first additive includes fluorobenzene, as shown in Formula II:

[0235] The second additive includes vinyl sulfate (DTD), and based on the total mass of the electrolyte, the mass content of fluorobenzene is 2% and the mass content of DTD is 1%.

[0236] After mixing thoroughly, LiPF6 is added to dissolve it in the organic solvent, so that the concentration of the electrolyte is 1 mol / L. The mixture is stirred evenly to obtain the electrolyte of Example 1.

[0237] (5) Battery fabrication:

[0238] The positive electrode, separator, and negative electrode are stacked in sequence. The separator must be able to isolate the positive and negative electrodes. The bare cell is obtained by winding. The bare cell is placed in the outer packaging, electrolyte is injected, and it goes through processes such as encapsulation, formation, and degassing to finally obtain a lithium-ion battery.

[0239] The preparation methods of Examples 2-12 are basically the same as those of Example 1, except that the corresponding parameters of the electrolyte are adjusted, as shown in Table 2.

[0240] In Example 2, the type of the first additive was adjusted to 1,3,5-trifluorobenzene.

[0241] In Example 3, the type of the first additive was adjusted to hexafluorobenzene.

[0242] In Example 4, the type of the first additive was adjusted to 1,4-difluorobenzene.

[0243] In Example 5, the type of the first additive was adjusted to fluoroanisole.

[0244] In Example 6, the mass content of the first additive was adjusted to 0.5%, based on the total mass of the electrolyte.

[0245] In Example 7, the mass content of the first additive was adjusted to 10%, based on the total mass of the electrolyte.

[0246] In Example 8, the mass content of the first additive was adjusted to 0.1%, based on the total mass of the electrolyte.

[0247] In Example 9, the type of the second additive was adjusted to vinylene carbonate (VC).

[0248] In Example 10, the mass content of the second additive was adjusted to 0.5%, based on the total mass of the electrolyte.

[0249] In Example 11, the mass content of the second additive was adjusted to 0.1%, based on the total mass of the electrolyte.

[0250] No second additive was added in Example 12.

[0251] The preparation methods of Examples 13-15 are basically the same as those of Example 1, except that the preparation method of the positive electrode sheet is adjusted, as shown in Tables 2 and 3.

[0252] Example 13

[0253] (1) Preparation of positive electrode sheet

[0254] LiFe 0.37 Mn 0.62 Ti 0.005 PO4, LiFe 0.7 Mn 0.29 Ti 0.005 PO4 is mixed at a mass ratio of 70%:30% to obtain a positive electrode active material. The above-mentioned mixed positive electrode active material, conductive agent conductive carbon black, and binder polyvinylidene fluoride are mixed at a weight percentage of 96:1.5:2.5 and N-methylpyrrolidone is added. After thorough mixing, stirring, and dispersion, a positive electrode slurry is prepared.

[0255] Example 14

[0256] (1) Preparation of positive electrode sheet

[0257] LiFe 0.37 Mn 0.62 Ti 0.005 PO4, LiFe 0.7 Mn 0.29 Ti 0.005 The positive electrode active material is obtained by mixing the above-mentioned mixed positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride at a weight percentage of 96:1.5:2.5, and N-methylpyrrolidone is added. After thorough mixing, stirring, and dispersion, a positive electrode slurry is prepared.

[0258] Example 15

[0259] (1) Preparation of positive electrode sheet

[0260] LiFe 0.37 Mn 0.62 Ti 0.005 PO4, LiFe 0.7 Mn 0.29 Ti 0.005 LiFe 0.99 Ti 0.005 PO4 (BP-LFP-02) was mixed in a mass ratio of 70%:20%:10% to obtain a positive electrode active material. The above-mentioned mixed positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride were mixed in a weight percentage of 96:1.5:2.5 and N-methylpyrrolidone was added. After thorough mixing, stirring, and dispersion, a positive electrode slurry was prepared.

[0261] The preparation methods of Examples 16-17 are basically the same as those of Example 1, except that the preparation method of the positive electrode sheet is adjusted, as shown in Tables 2 and 3.

[0262] Example 16

[0263] (1) Preparation of positive electrode sheet

[0264] LiFe 0.37 Mn 0.62 Ti 0.005 PO4, LiFe 0.7 Mn 0.29 Ti 0.005 LiFe 0.91 Mn 0.08 Ti 0.0 05 PO4 was mixed in a mass ratio of 70%:20%:10% to obtain a positive electrode active material. The above-mentioned mixed positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride were mixed in a weight percentage of 96:1.5:2.5 and N-methylpyrrolidone was added. After thorough mixing, stirring, and dispersion, a positive electrode slurry was prepared.

[0265] Example 17

[0266] (1) Preparation of positive electrode sheet

[0267] LiFe 0.37 Mn 0.62 Ti 0.005 PO4, LiFe 0.7 Mn 0.29 Ti 0.005 LiFe 0.70 Mn 0.29 Ti 0.0 05 PO4 was mixed in a mass ratio of 70%:20%:10% to obtain a positive electrode active material. The above-mentioned mixed positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride were mixed in a weight percentage of 96:1.5:2.5 and N-methylpyrrolidone was added. After thorough mixing, stirring, and dispersion, a positive electrode slurry was prepared.

[0268] The preparation methods of Examples 18-19 are basically the same as those of Example 15, except that the corresponding parameters of the electrolyte are adjusted, as shown in Tables 2 and 3.

[0269] In Example 18, the type of the first additive was adjusted to 1,4-difluorobenzene.

[0270] In Example 19, the type of the first additive was adjusted to fluoroanisole.

[0271] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the corresponding parameters of the electrolyte are adjusted, as shown in Table 2.

[0272] In Comparative Example 1, neither the first nor the second additive was added.

[0273] Comparative Example 2

[0274] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that the preparation method of the positive electrode sheet and the corresponding parameters of the electrolyte are adjusted, as shown in Table 2.

[0275] Comparative Example 2

[0276] (1) Preparation of positive electrode sheet

[0277] LiFe 0.37 Mn 0.62 Ti 0.005 PO4, LiFe 0.41 Mn 0.58 Ti 0.005 PO4 is mixed at a mass ratio of 70%:30% to obtain a positive electrode active material. The above-mentioned mixed positive electrode active material, conductive agent conductive carbon black, and binder polyvinylidene fluoride are mixed at a weight percentage of 96:1.5:2.5 and N-methylpyrrolidone is added. After thorough mixing, stirring, and dispersion, a positive electrode slurry is prepared.

[0278] II. Testing Methods

[0279] 1. Discharge specific capacity in the first week

[0280] After formation, the cell is first charged at a constant current of 0.1C to 4.15V at room temperature, then charged at a constant voltage of 4.15V to a current of 0.02C, and then discharged at a constant current of 0.1C to 2.0V. The capacity C0 released at this time is recorded as the first cycle discharge capacity.

[0281] 2. Storage performance

[0282] Place the battery in a 60℃ oven and let it stand for 2 hours until the battery temperature reaches 60℃. Then, discharge the battery at a constant current of 1 / 3C to 2.0V. After standing for 5 minutes, charge the battery at a constant current of 1 / 3C to 4.15V, and then charge it at a constant voltage of 4.15V to a current of 0.05C. After standing for 5 minutes, discharge the battery at a constant current of 1 / 3C to 2.0V. This is one charge-discharge cycle. Record the discharge capacity C1 of the first cycle. Then, fully charge the battery and place it in a 60℃ environment. Periodically take out the battery and test the remaining capacity at 60℃ until the discharge capacity of the individual battery cells decays to 80%. Record the storage time at this point.

[0283] 3. Volumetric energy density

[0284] Battery cell capacity test: The battery cell was left to stand at 60℃ for 2 hours to ensure the temperature of the battery cell was 60℃. Then the battery was discharged at 1 / 3C constant current to 2.0V. After standing for 5 minutes, the battery cell was charged at 1 / 3C constant current to 4.15V. The constant voltage charging at 4.15V continued until the current was 0.05C. After standing for 5 minutes, the battery cell was discharged at 1 / 3 constant current to 2.0V. The total discharge capacity C0 and the total discharge energy E0 of the battery cell were recorded. The unit of total discharge energy is Wh.

[0285] Battery cell volume measurement: Use calipers to measure the length, width, and height of the battery's outer surface, and calculate the cell volume V0 in liters (L).

[0286] Volumetric energy density calculation: The volumetric energy density of a battery cell is calculated as follows: Discharge energy of a single battery cell E0 / Battery volume V0.

[0287] III. Test Results

[0288] Table 2

[0289] The positive electrode film layer in Examples 1-19 of this application includes a first type of particles and a second type of particles, wherein the primary particle size of the first type of particles is greater than 180 nm and less than 900 nm, the primary particle size of the second type of particles is greater than or equal to 900 nm and less than or equal to 5 μm, and the average molar percentage of Mn in the second type of particles is less than the average molar percentage of Mn in the first type of particles; and the electrolyte includes a first additive with the structure shown in the following formula:

[0290] As can be seen from the comparison between the examples and the comparative examples, by controlling the average value of the Mn molar ratio of the second type of particles to be less than the average value of the Mn molar ratio of the first type of particles, and by adding a first additive to the electrolyte, the battery can reduce the impact of Mn dissolution from small-diameter particles with a relatively high Mn molar ratio on the SEI film while maintaining a high volumetric energy density, thereby reducing the loss of active lithium and improving the battery's storage performance and capacity.

[0291] As can be seen from the comparison between Example 5 and Examples 1-4, the first additive includes (Fluorobenzene) (1,4-Difluorobenzene) (1,3,5-Trifluorobenzene) One or more of (hexafluorobenzene) can help to further improve the capacity and storage performance of the battery while maintaining good energy density.

[0292] As can be seen from Examples 1, 6, 7 and 8, based on the total mass of the electrolyte, the mass content of the first additive is 0.1%-10%, and the battery has good energy density, capacity and storage performance.

[0293] A comparison of Examples 7 and 8 with Examples 1 and 6 shows that, based on the total mass of the electrolyte, when the mass content of the first additive is 0.5%-2%, the battery has good energy density, further improving the battery capacity and storage performance.

[0294] As can be seen from the comparison between Examples 1 and 9 and Example 12, the electrolyte also includes a second additive of vinylene carbonate or vinyl sulfate, which gives the battery good energy density, further improving the battery capacity and storage performance.

[0295] As can be seen from the comparison between Example 11 and Examples 1 and 10, based on the total mass of the electrolyte, the mass content of the second additive is 0.5%-1%, and the battery has good energy density, further improving the battery capacity and storage performance.

[0296] As can be seen from the comparison between Example 14 and Example 13, controlling the area ratio of the first type of particles to 40%-60% and the area ratio of the second type of particles to 25%-60% can further improve the storage performance of the battery, while also ensuring that the battery has a high energy density.

[0297] As can be seen from the comparison between Example 13 and Example 1, controlling the average molar ratio of Mn in the second type of particles to 0.1-0.3 can further improve the energy density of the battery.

[0298] Table 3

[0299] As can be seen from the comparison between Examples 15-19 and Example 1, the positive electrode film layer also contains a third type of particles with a primary particle size of 50nm-180nm, and the area ratio of the third type of particles is greater than or equal to 5% and less than or equal to 30%, which can further improve the energy density of the battery.

[0300] A comparison of Examples 15-16 and Example 17 shows that controlling the molar ratio of Mn in the third type of particles to 0-0.2 can further improve the storage performance of the battery while maintaining its good energy density.

[0301] As can be seen from the comparison between Example 16 and Examples 15 and 17, controlling the molar ratio of Mn in the third type of particles to 0.1-0.2 can further improve the energy density of the battery.

[0302] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. 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, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, It includes a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a first type of particles and a second type of particles, wherein the first type of particles and the second type of particles include lithium transition metal phosphate materials. The first type of particles has a primary particle size greater than 180 nm and less than 900 nm, while the second type of particles has a primary particle size greater than or equal to 900 nm and less than or equal to 5 μm. The average value of the Mn molar percentage of the second type of particles is less than the average value of the Mn molar percentage of the first type of particles, wherein the Mn molar percentage refers to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe. The electrolyte comprises an organic solvent, an electrolyte salt, and a first additive, wherein the first additive comprises one or more of the structures shown in Formula I: R1, R2, R3, R4, R5, and R6 each independently include one or more of hydrogen, halogen, substituted or unsubstituted C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 alkoxy, C2-C6 alkenyl, C2-C6 alkynyl, cyano, fluorosulfonic acid, and C1-C6 alkylsulfonic acid, and at least one of R1, R2, R3, R4, R5, and R6 contains fluorine.

2. The battery cell according to claim 1, characterized in that, R1, R2, R3, R4, R5, and R6 each independently include one or more of hydrogen, halogen, substituted or unsubstituted C1-C4 alkyl, C1-C4 fluoroalkyl, C1-C4 alkoxy, C2-C4 alkenyl, C2-C4 alkynyl, cyano, fluorosulfonic acid, and C1-C4 alkylsulfonic acid, and at least one of R1, R2, R3, R4, R5, and R6 is fluorine.

3. The battery cell according to claim 1 or 2, characterized in that, R1, R2, R3, R4, R5, and R6 each independently include one or more of hydrogen atoms and fluorine atoms, and at least one of R1, R2, R3, R4, R5, and R6 is fluorine.

4. The battery cell according to claim 1, characterized in that, The first additive includes One or more of them.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The first additive includes One or more of them.

6. The battery cell according to any one of claims 1 to 5, characterized in that, Based on the total mass of the electrolyte, the mass content of the first additive is 0.1%-10%.

7. The battery cell according to any one of claims 1 to 6, characterized in that, Based on the total mass of the electrolyte, the mass content of the first additive is 0.1%-5%, optionally 0.5%-2%.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The electrolyte further includes a second additive, which includes one or more of vinylene carbonate, fluorovinyl carbonate, succinate, adiponitrile, vinyl sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphate, and may be selected from one or more of vinyl sulfate and vinylene carbonate.

9. The battery cell according to claim 8, characterized in that, Based on the total mass of the electrolyte, the mass content of the second additive is 0.1%-10%, optionally 0.1%-5%, and further optionally 0.5%-1%.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The organic solvent includes carbonate solvents, which include one or more of ethylene carbonate, propylene carbonate, butene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The organic solvent also includes carboxylic acid ester solvents, which include one or more of methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, and ethyl butyrate.

12. The battery cell according to any one of claims 10 to 11, characterized in that, Based on the total mass of organic solvents in the electrolyte, the mass content of the carbonate solvent is 50%-100%, and the mass content of the carboxylic acid ester solvent is 0%-50%.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium difluorodioxalate phosphate (LiODFP), and lithium dioxalate borate (LiBOB).

14. The battery cell according to any one of claims 1 to 13, characterized in that, The concentration of the electrolyte salt is 0.8 mol / L to 1.2 mol / L.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The average molar ratio of Mn in the first type of particles is 0.4-0.9, and can be selected as 0.5-0.

9.

16. The battery cell according to any one of claims 1 to 15, characterized in that, The average molar percentage of Mn in the second type of particles is 0-0.6, which can be selected as 0-0.5, more preferably 0-0.1, and even more preferably 0.

17. The battery cell according to any one of claims 1 to 16, characterized in that, Based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the second type of particles is 0%-50%, optionally 0%-30%, more preferably 0%-10%, and even more preferably 0%.

18. The battery cell according to any one of claims 1 to 17, characterized in that, Based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 20%-95%, optionally 20%-80%, more preferably 40%-60%, and / or the area ratio of the second type of particles is 5%-80%, optionally 15%-80%, more preferably 25%-60%.

19. The battery cell according to any one of claims 1 to 18, characterized in that, The positive electrode film layer includes a third type of particles, which includes the lithium-containing transition metal phosphate material. The primary particle size of the third type of particles is greater than or equal to 50 nm and less than or equal to 180 nm. Based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the third type of particles is greater than or equal to 5% and less than or equal to 30%.

20. The battery cell according to claim 19, characterized in that, Based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0%-12%, optionally 0%-8%, more preferably 0%-6%, and even more preferably 0%.

21. The battery cell according to claim 19 or 20, characterized in that, The average Mn molar ratio of the third type of particles is 0-0.6, optionally 0-0.4, more preferably 0-0.2, and even more preferably 0.

22. The battery cell according to any one of claims 19 to 21, characterized in that, Based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the first type of particles is 45%-85%, the area ratio of the second type of particles is 10%-40%, and the area ratio of the third type of particles is 5%-15%.

23. The battery cell according to any one of claims 1 to 22, characterized in that, Based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 45%-85%, the average molar ratio of Mn in the first type of particles is 0.5-0.9, and based on the total mass of the electrolyte, the mass content of the first additive is 0.1%-5%, and the mass content of the second additive is 0.1%-3%.

24. The battery cell according to any one of claims 1 to 23, characterized in that, The general formula of the lithium-containing transition metal phosphate material of the first type of particles includes Li m1 Fe x1 Mn r1 P y1 O j1 Q1 q1 Wherein, 0.95≤m1≤1.15, x1>0, r1>0, 0.9≤x1+r1≤1, 0.95≤y1≤1, 3.5≤j1≤4, 0≤q1≤0.1, and Q1 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br; and / or, The general formula for the lithium-containing transition metal phosphate materials of the second type of particles includes Li m2 Fe x2 Mn r2 P y2 O j2 Q2 q2 Wherein, 0.95≤m2≤1.15, x2>0, r2≥0, 0.9≤x2+r2≤1, 0.95≤y2≤1, 3.5≤j2≤4, 0≤q2≤0.1, and Q2 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

25. The battery cell according to any one of claims 20 to 24, characterized in that, The general formula of the lithium-containing transition metal phosphate material of the third type of particles includes Li m3 Fe x3 Mn r3 P y3 O j3 Q1 q3 Wherein, 0.95≤m3≤1.15, x3>0, r3≥0, 0.9≤x3+r3≤1, 0.95≤y3≤1, 3.5≤j3≤4, 0≤q3≤0.1, and Q3 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

26. The battery cell according to any one of claims 1 to 25, characterized in that, The compaction density of the positive electrode sheet is 2.25 g / cm³. 3 -2.75g / cm 3 .

27. The battery cell according to any one of claims 1 to 26, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes one or more of the following: natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, ferric oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, sodium titanate, and sodium terephthalate.

28. A battery device, characterized in that, The battery device includes the battery cell of any one of claims 1 to 27, and the battery device includes at least one of battery module, battery pack, and energy storage battery.

29. An electrical appliance, characterized in that, Includes the battery device of claim 28, the battery device being used to provide electrical energy.

30. An energy storage device, characterized in that, Includes the battery device of claim 28, the battery device being used for storing electrical energy.

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