Positive electrode active material composition, positive electrode sheet, battery, and power using device

Abstract

The present application provides a positive electrode active material composition, a positive electrode sheet, a battery and a power device. The positive electrode active material composition of the present application comprises a first positive electrode active material and a second positive electrode active material; wherein the first positive electrode active material comprises an inner core Li a A b Mn f B 1‑f P 1‑d R d O 4‑n D n and a coating layer covering the inner core, and the second positive electrode active material comprises a compound LiNi x Co y M 1‑x‑y O2, and satisfies: 0.018m+0.003f≤z≤0.02m+0.02f.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a positive electrode active material composition, a positive electrode sheet, a battery and a power utilization device. BACKGROUND

[0002] In recent years, with the application range of secondary batteries becoming more and more extensive, secondary batteries are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Due to the great development of secondary batteries, it is currently urgent to improve the storage performance of the battery while improving the cycle performance of the battery. SUMMARY

[0003] The present application is made in view of the above-mentioned problems, and aims to provide a positive electrode active material composition, a positive electrode sheet, a battery and a power utilization device. The use of the positive electrode active material composition of the present application is conducive to improving the storage performance of the battery, while helping to inhibit the dissolution of Mn 2+ ions and improve the cycle performance of the battery.

[0004] To achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode active material composition, comprising a first positive electrode active material and a second positive electrode active material; wherein,

[0005] The first positive electrode active material comprises a core and a coating layer coating the core, the coating layer comprises one or more of pyrophosphate, phosphate and carbon, and the core comprises a compound Li a A b Mn f B 1-f P 1-d R d O 4-n D n , wherein,

[0006] A comprises one or more elements of Zn, Al, Na, K, Mg, Nb, Mo and W;

[0007] B comprises one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, and can optionally comprise one or more elements of Fe, Ti, V, Ni, Co and Mg;

[0008] R comprises one or more elements of B (boron), S, Si and N;

[0009] D comprises one or more elements of S, F, Cl and Br;

[0010] a is 0.9 to 1.1, optionally 0.977 to 1; b is 0 to 0.1, optionally 0 to 0.001; f is 0.1 to 0.999, optionally 0.1 to 0.9; d is 0 to 0.1, optionally 0 to 0.001 or 0.001 to 0.1; n is 0 to 0.1, optionally 0 to 0.001 or 0.001 to 0.1;

[0011] The second positive electrode active material includes a compound LiNi x Co y M 1-x-y O2, wherein M includes one or more elements of Al, Mn, Mg, Nb, Ti and Ba; 0.5≤x≤0.69; 0

[0012] and satisfies:

[0013] 0.018m+0.003f≤z≤0.02m+0.02f

[0014] wherein,

[0015] m represents the mass percentage of the first positive electrode active material in the positive electrode active material composition;

[0016] z represents the ratio of the coating layer thickness of the first positive electrode active material to the Dv50 particle size.

[0017] The lithium manganese iron phosphate material has a high voltage platform and energy density, but the lithium manganese iron phosphate material is almost an insulator, which affects the exertion of the electrochemical performance of the material, and the Jahn-Teller effect of Mn 3+ ions is easy to cause lattice distortion, and Mn 2+ ions are easy to damage the negative electrode SEI film, resulting in a decrease in the cycle performance of the battery. The coated lithium manganese iron phosphate is beneficial to improve the electronic conductivity of the material and inhibit the dissolution of Mn 2+ ions, but the inventors of the present application found that the existing coated lithium manganese iron phosphate is easy to react with the electrolyte during the high SOC storage stage, resulting in deterioration of the storage performance of the battery.

[0018] Therefore, the present application combines the first positive electrode active material and the second positive electrode active material, and limits the relationship between the ratio of the coating layer thickness of the first positive electrode active material to the Dv50 particle size, the proportion of the first positive electrode active material and the Mn content. On the one hand, since the second positive electrode active material with good conductivity is used, the ratio of the coating layer thickness of the first positive electrode active material to the Dv50 particle size can be appropriately reduced to reduce the reaction of the coating layer with the electrolyte during the high SOC storage stage, thereby improving the storage performance of the battery; on the other hand, the ratio of the coating layer thickness of the first positive electrode active material to the Dv50 particle size cannot be too low, otherwise it cannot inhibit the dissolution of Mn 2+The ion leaching leads to the decrease of the cycle performance of the battery.

[0019] In any embodiment, the coating layer of the first positive electrode active material has a thickness of 2-15 nm, which can be 5-11 nm. In this way, the reaction of the first positive electrode active material with the electrolyte during the high SOC storage stage is further inhibited, and the storage performance of the battery is improved. 2+ The ion leaching leads to the decrease of the cycle performance of the battery.

[0020] In any embodiment, the Dv50 particle size of the first positive electrode active material is 400-1600 nm, which can be 420-730 nm. In this way, the conductivity of the first positive electrode active material is improved.

[0021] In any embodiment, f is 0.3-0.8. In this way, the voltage plateau of the first positive electrode active material is improved, and the defects in the material are reduced, the occurrence of side reactions is reduced, and the cycle performance and conductivity of the battery are improved.

[0022] In any embodiment, the coating layer of the first positive electrode active material comprises carbon.

[0023] In any embodiment, m is 30%-80%. In this way, the electrical performance and cost benefit of the battery are comprehensively improved.

[0024] The second aspect of the present application also provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode active material composition of the first aspect of the present application.

[0025] In this way, the use of the positive electrode sheet of the present application is beneficial to inhibit the reaction of the positive electrode active material with the electrolyte during the high SOC storage stage, thereby improving the storage performance of the battery, and inhibiting the leaching of Mn 2+ The ion leaching leads to the decrease of the cycle performance of the battery.

[0026] The third aspect of the present application also provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material; and at least one positive electrode film layer has a multi-layer structure, and at least one positive electrode film layer having a multi-layer structure comprises a first positive electrode active material and a second positive electrode active material in different layers, respectively, and the first positive electrode active material and the second positive electrode active material are as described in the first aspect of the present application.

[0027] And meet:

[0028] 0.018m’+0.003f≤z≤0.02m’+0.02f

[0029] Wherein,

[0030] m’ represents the mass percentage of the first positive electrode active material in the positive electrode active material.

[0031] z represents the ratio of the coating layer thickness of the first positive electrode active material to the Dv50 particle size;

[0032] Optionally, m' is 30%-80%.

[0033] Therefore, the positive electrode sheet of the present application is beneficial to inhibit the reaction of the positive electrode active material with the electrolyte during the high SOC storage stage, thereby improving the storage performance of the battery, and inhibiting the dissolution of Mn 2+ ions, thereby improving the cycle performance of the battery.

[0034] The fourth aspect of the present application provides a battery comprising the positive electrode active material composition of the first aspect of the present application, the positive electrode sheet of the second aspect of the present application, or the positive electrode sheet of the third aspect of the present application.

[0035] In the present application, the battery includes but is not limited to a secondary battery, a battery module, and a battery pack.

[0036] The fifth aspect of the present application provides a power utilization device comprising the positive electrode active material composition of the first aspect of the present application, the positive electrode sheet of the second aspect of the present application, the positive electrode sheet of the third aspect of the present application, or the battery of the fourth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0038] Figure 2 is a schematic diagram of a secondary battery according to an embodiment of the present application. Figure 1

[0039] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0040] Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0041] Figure 5 is a schematic diagram of a battery pack according to an embodiment of the present application. Figure 4

[0042] Figure 6 is a schematic diagram of a power utilization device using a secondary battery according to an embodiment of the present application as a power source.

[0043] BRIEF DESCRIPTION OF DRAWINGS

[0044] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0045] ​​Hereinafter, specific embodiments of the positive electrode active material composition, the positive electrode sheet, the secondary battery, the battery module, the battery pack, and the power using device of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0046] The ranges disclosed herein are defined by their lower and upper limits, given that the range is defined by selecting a lower limit and an upper limit, the selected lower and upper limits define the boundaries of the particular range. Ranges defined by the endpoints can include the endpoints, or can not include the endpoints, and can be freely combined in any manner. For example, if a range of 60-120 and a range of 80-110 are listed, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing each and every integer between the number "a" and the number "b", wherein "a" and "b" are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand way of describing those numerical combinations. Also, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0047] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0048] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0049] If not specifically stated, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, a method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, a method further comprising step (c) means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0050] If not specifically stated, "comprising" and "including" mentioned in the present application means open or closed. For example, "comprising" and "including" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0051] If not specifically stated, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any one of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0052] If not specifically stated, in the present application, the term "Dv50 particle size" refers to the particle size that reaches 50% of the volume accumulation from the small particle size side in the volume-based particle size distribution.

[0053] [Secondary battery]

[0054] A secondary battery, also known as a rechargeable battery or a storage battery, refers to a battery that can continue to be used by activating active materials through charging after the battery is discharged.

[0055] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the charging and discharging process of the battery, active ions (e.g., lithium ions) are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and mainly functions to prevent short circuiting between the positive and negative electrodes, while allowing the active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, and mainly functions to conduct the active ions.

[0056] [Positive active material composition]

[0057] One embodiment of the present application provides a positive active material composition comprising a first positive active material and a second positive active material; wherein,

[0058] The first positive electrode active material includes an inner core and a coating layer coating the inner core, the coating layer including one or more of pyrophosphate, phosphate and carbon, and the inner core including a compound Li a A b Mn f B 1-f P 1-d R d O 4-n D n wherein,

[0059] A includes one or more elements of Zn, Al, Na, K, Mg, Nb, Mo and W;

[0060] B includes one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, and optionally one or more elements of Fe, Ti, V, Ni, Co and Mg;

[0061] R includes one or more elements of B (boron), S, Si and N;

[0062] D includes one or more elements of S, F, Cl and Br;

[0063] a is 0.9 to 1.1, optionally 0.977 to 1, for example 0.9, 0.93, 0.95, 0.98, 1, 1.1 and ranges formed by any of the above values; b is 0 to 0.1, optionally 0 to 0.001, for example 0, 0.001, 0.002, 0.005, 0.007, 0.01, 0.03, 0.05, 0.07, 0.09, 0.1 and ranges formed by any of the above values; f is 0.1 to 0.999, optionally 0.1 to 0.9, for example 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.98, 0.999 and ranges formed by any of the above values; d is 0 to 0.1, optionally 0 to 0.001 or 0.001 to 0.1, for example 0, 0.001, 0.002, 0.005, 0.007, 0.01, 0.03, 0.05, 0.07, 0.09, 0.1 and ranges formed by any of the above values; n is 0 to 0.1, optionally 0 to 0.001 or 0.001 to 0.1, for example 0, 0.001, 0.002, 0.005, 0.007, 0.01, 0.03, 0.05, 0.07, 0.09, 0.1 and ranges formed by any of the above values;

[0064] The second positive electrode active material includes a compound LiNi x Co y M 1-x-yO2, wherein M comprises one or more elements of Al, Mn, Mg, Nb, Ti and Ba; 0.5≤x≤0.69, for example x is 0.52, 0.55, 0.57, 0.58, 0.6, 0.63, 0.64, 0.66, 0.69 and a range consisting of any of the above values; 0<y<0.31, for example y is 0.001, 0.003, 0.005, 0.01, 0.02, 0.03, 0.05, 0.07, 0.1, 0.13, 0.15, 0.17, 0.2, 0.22, 0.25, 0.27, 0.28, 0.3 and a range consisting of any of the above values;

[0065] and satisfies:

[0066] 0.018m+0.003f≤z≤0.02m+0.02f

[0067] wherein,

[0068] m represents the mass percentage of the first positive electrode active material in the positive electrode active material composition;

[0069] z represents the ratio of the coating layer thickness of the first positive electrode active material to the Dv50 particle size;

[0070] f is the core compound Li a A b Mn f B 1-f P 1-d R d O 4-n D n in the first positive electrode active material.

[0071] The lithium manganese iron phosphate material has a high voltage platform and energy density, but the lithium manganese iron phosphate material is almost an insulator, which affects the exertion of the electrochemical performance of the material, and the Jahn-Teller effect of Mn 3+ ions produced in the material is easy to cause lattice distortion, and the dissolution of Mn 2+ ions is easy to damage the negative electrode SEI film, resulting in a decrease in the cycle performance of the battery. The coated lithium manganese iron phosphate is beneficial to improve the electronic conductivity of the material and inhibit the dissolution of Mn 2+ ions, but the inventors of the present application have found that the existing coated lithium manganese iron phosphate is easy to react with the electrolyte during the high SOC storage stage, resulting in deterioration of the storage performance of the battery.

[0072] Although the mechanism is not clear, the applicant has unexpectedly found that the present application combines the first positive electrode active material and the second positive electrode active material, and limits the relationship between the ratio of the coating layer thickness and the Dv50 particle size of the first positive electrode active material and the proportion of the first positive electrode active material and the Mn content. Due to the use of the second positive electrode active material with good conductivity, the ratio of the coating layer thickness and the Dv50 particle size of the first positive electrode active material is appropriately reduced, which can reduce the reaction between the coating layer and the electrolyte in the high SOC storage stage, thereby improving the storage performance of the battery; at the same time, the ratio of the coating layer thickness and the Dv50 particle size of the first positive electrode active material cannot be too low, otherwise it cannot play a role in inhibiting the dissolution of Mn 2+ ions, resulting in a decrease in the cycle performance of the battery.

[0073] In some embodiments, the compound Li a A b Mn f B 1-f P 1-d R d O 4-n D n remains electrically neutral.

[0074] In some embodiments, the compound LiNi x Co y M 1-x-y O2 remains electrically neutral.

[0075] In some embodiments, the coating layer thickness of the first positive electrode active material is 2-15 nm, which can be 5-11 nm, for example, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 12 nm, 13 nm, 15 nm and a range consisting of any of the above values. Thereby, the dissolution of Mn 2+ ions is further inhibited, and the cycle performance of the battery is improved.

[0076] In some embodiments, the thickness of the coating layer is determined by conventional methods in the art, for example, it can be determined by FIB, and the specific method can include the following steps: randomly selecting a single particle from the positive electrode active material powder to be measured, cutting a thin slice of about 100 nm thickness from the middle position or the vicinity of the middle position of the selected particle, and then performing TEM test on the thin slice, measuring the thickness of the coating layer, measuring 3-5 positions, and taking the average value.

[0077] In some embodiments, the first positive electrode active material has a Dv50 particle size of 400-1600 nm, optionally 420-730 nm, for example 400 nm, 420 nm, 450 nm, 470 nm, 500 nm, 520 nm, 550 nm, 580 nm, 600 nm, 650 nm, 700 nm, 730 nm, 750 nm, 770 nm, 800 nm, 830 nm, 850 nm, 870 nm, 900 nm, 1000 nm, 1200 nm, 1300 nm, 1500 nm, 1600 nm, and ranges derived from any of the foregoing. This is beneficial for improving the conductivity of the first positive electrode active material.

[0078] In some embodiments, the Dv50 particle size is determined by a method conventional in the art, for example according to the method in the national standard GB / T 19077-2016 “Particle Size Distribution-Laser Diffraction Method”.

[0079] In some embodiments, f is 0.3-0.8. This is beneficial for improving the voltage plateau of the first positive electrode active material, while reducing defects in the material, reducing the occurrence of side reactions, and improving the cycle performance of the battery and the conductivity of the material.

[0080] In some embodiments, the coating layer in the first positive electrode active material comprises carbon.

[0081] In some embodiments, m is 30%-80%, for example 30%, 40%, 50%, 60%, 70%, 80%, and ranges derived from any of the foregoing. This is beneficial for improving the electrical performance and cost-effectiveness of the battery as a whole.

[0082] [Positive electrode sheet]

[0083] One embodiment of the present application provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprising the positive electrode active material composition described previously in the present application.

[0084] Thus, the positive electrode sheet of the present application is beneficial for inhibiting the reaction of the positive electrode active material with the electrolyte during the high SOC storage stage, thereby improving the storage performance of the battery, while inhibiting the dissolution of Mn 2+ ions and improving the cycle performance of the battery.

[0085] Another embodiment of the present application provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material; wherein at least one positive electrode film layer has a multilayer structure, and the at least one positive electrode film layer having a multilayer structure comprises a first positive electrode active material and a second positive electrode active material in different layers, respectively, and the first positive electrode active material and the second positive electrode active material are as described previously.

[0086] and satisfies:

[0087] 0.018m' + 0.003f < z < 0.02m' + 0.02f

[0088] wherein,

[0089] m' represents a mass percentage of the first positive electrode active material in the positive electrode active material;

[0090] z represents a ratio of a cladding layer thickness of the first positive electrode active material to the Dv50 particle size;

[0091] Optionally, m' is 30%-80%, for example, 30%, 40%, 50%, 60%, 70%, 80%, and a range consisting of any of the above values.

[0092] Thus, the positive electrode tab of the present application is beneficial to inhibit the reaction of the positive electrode active material with the electrolyte during the high SOC storage stage, thereby improving the storage performance of the battery, while inhibiting the dissolution of Mn 2+ ions, improving the cycle performance of the battery.

[0093] As an example, the positive current collector has two surfaces opposite in the thickness direction of the positive current collector itself, and the positive film layer is arranged on any one or both of the two opposite surfaces of the positive current collector.

[0094] In some embodiments, the positive current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be adopted. The composite current collector can include a high polymer material base layer and a metal layer formed on at least one surface of the high polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a high polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0095] In some embodiments, the positive electrode sheet can further include other positive electrode active materials known in the art. As an example, the positive electrode active material can include at least one of lithium-containing phosphates of olivine structure, lithium transition metal oxides, and modified compounds of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone only one or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, at least one of lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be referred to as NCM 333 ) and modified compounds thereof, etc. Examples of the lithium-containing phosphates of olivine structure can include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which can also be referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite of lithium manganese phosphate and carbon.

[0096] In some embodiments, the positive electrode film layer can optionally further include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene-fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene-fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0097] In some embodiments, the positive electrode film layer can optionally further include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0098] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-described components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, coating the positive electrode slurry on a positive electrode current collector, and then drying, cold-pressing, etc., to obtain the positive electrode sheet.

[0099] [Negative electrode sheet]

[0100] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0101] As an example, the negative current collector has two surfaces opposite in the thickness direction thereof, and the negative film layer is disposed on either one or both of the two surfaces of the negative current collector.

[0102] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0103] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0104] In some embodiments, the negative film layer can further optionally include a binder. As an example, the binder can 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).

[0105] In some embodiments, the negative film layer can further optionally include a conductive agent. As an example, the conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0106] In some embodiments, the negative film layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0107] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and then drying, cold-pressing, or the like to obtain the negative electrode sheet.

[0108] [Electrolyte]

[0109] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not particularly limited in the present application, and can be selected as needed. For example, the electrolyte can be liquid, gel, or solid.

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

[0111] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

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

[0113] In some embodiments, the electrolyte solution can also optionally include an additive. As an example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0114] [Separator]

[0115] In some embodiments, the secondary battery further includes a separator. The type of separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0116] In some embodiments, the material of the separator film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0117] In some embodiments, the positive electrode tab, the negative electrode tab, and the separator film can be used to form an electrode assembly through a winding process or a stacking process.

[0118] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0119] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, or the like can be listed.

[0120] The shape of the secondary battery is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, Figure 1 is a square structure as an example of a secondary battery 5.

[0121] In some embodiments, referring to Figure 2 , the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator film can be used to form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and a person skilled in the art can select according to the specific actual needs.

[0122] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0123] Figure 3 is a battery module 4 as an example. Referring to Figure 3 , in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0124] Optionally, the battery module 4 can further include a case having an accommodation space, and the plurality of secondary batteries 5 can be accommodated in the accommodation space.

[0125] In some embodiments, the above-described battery module can be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0126] Figure 4 and Figure 5 is a battery pack 1 as an example. Referring to Figure 4 and Figure 5 In the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box can be included. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be provided on the lower box body 3 and form a closed space for accommodating the battery module 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0127] In addition, the present application also provides a power utilization device, which includes at least one of the secondary battery, the battery module, or the battery pack provided by the present application. The secondary battery, the battery module, or the battery pack can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0128] As the power utilization device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirements thereof.

[0129] Figure 6 is a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the power utilization device, the battery pack or the battery module can be used.

[0130] [Embodiment]

[0131] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If the specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0132] Example 1

[0133] (1) First positive electrode active material: carbon-coated LiMn 0.3 Fe 0.7 PO4, purchased from Shenzhen Defang Nanometer Technology Co., Ltd.

[0134] (2) Second positive electrode active material: LiNi 0.8 0Co 0.10 Mn 0.10 O2, purchased from Guangdong Bangpu Cycle Technology Co., Ltd.

[0135] (3) Preparation of positive electrode tab: The first positive electrode active material, the second positive electrode active material, polyvinylidene fluoride (PVDF) and conductive carbon are dissolved in the solvent N-methyl pyrrolidone (NMP) according to the mass ratio of 28.95:67.55:2:1.5, and after being fully stirred and mixed uniformly, a positive electrode slurry with a viscosity of 4000-15000 mPa·S is prepared; the positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and then dried, cold-pressed, and cut to obtain the positive electrode tab.

[0136] (4) Preparation of negative electrode tab: Graphite, sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and conductive carbon are added to a certain amount of deionized water according to a mass ratio of 95:1:2:2, and stirred to form a uniform slurry with a viscosity of 3000-10000 mPa·S. The slurry is coated on a copper foil and dried to form a negative electrode tab.

[0137] (5) Separator: Polyethylene (PE) porous polymer film.

[0138] (6) Preparation of electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0139] (7) Preparation of lithium ion battery:

[0140] The prepared positive electrode tab, negative electrode tab and separator are sequentially placed into a winding device, the positive electrode tab and the negative electrode tab are inserted with the separator in between, and then wound into a square electrode assembly, which is then placed into an aluminum square case. The cell is vacuum dried at >100℃, and then the positive and negative electrode tabs are ultrasonically welded, the positive and negative electrode tabs are located on the same side of the cell, liquid injection, standing, formation, aging, and capacity test are performed to obtain the prepared lithium ion battery.

[0141] Examples 2-15 and Comparative Examples 1-3 have similar lithium ion battery preparation methods as Example 1, and the product parameters are shown in Table 1. Among them:

[0142] m represents the mass percentage of the first positive electrode active material in the two positive electrode active materials; z represents the ratio of the coating layer thickness of the first positive electrode active material to the Dv50 particle size; f represents the f in general formula Li a A b Mn f B 1-f P 1-d R d O 4-n D n in the f.

[0143] In Table 1, the first positive electrode active materials of Examples 1 to 12 are all purchased from Shenzhen Defang Nanometer Technology Co., Ltd.; the second positive electrode active materials of Examples 1 to 15 are all purchased from Guangdong Bangpu Cycle Technology Co., Ltd.

[0144] Method for producing the first positive electrode active material of Example 13

[0145] Preparation of doped manganese oxalate: 1.3 mol of MnSO4·H2O and 0.7 mol of FeSO4·H2O are mixed in a mixer for 6 hours. The mixture is transferred to a reaction kettle, and 10 L of deionized water and 2 mol of biquoxalate (calculated as oxalic acid) are added. The reaction kettle is heated to 80°C, and stirred at a speed of 600 rpm for 6 hours, and the reaction is terminated (no gas bubbles are generated), to obtain a Fe-doped manganese oxalate suspension. The suspension is then filtered, and the filter cake is dried at 120°C, and then ground, to obtain Fe-doped manganese oxalate particles with a median particle size Dv50 of about 100 nm. 50 Preparation of doped manganese oxalate: 1.3 mol of MnSO4·H2O and 0.7 mol of FeSO4·H2O are mixed in a mixer for 6 hours. The mixture is transferred to a reaction kettle, and 10 L of deionized water and 2 mol of biquoxalate (calculated as oxalic acid) are added. The reaction kettle is heated to 80°C, and stirred at a speed of 600 rpm for 6 hours, and the reaction is terminated (no gas bubbles are generated), to obtain a Fe-doped manganese oxalate suspension. The suspension is then filtered, and the filter cake is dried at 120°C, and then ground, to obtain Fe-doped manganese oxalate particles with a median particle size Dv50 of about 100 nm.

[0146] Preparation of doped lithium manganese phosphate: 1 mol of the above manganese oxalate particles, 0.497 mol of lithium carbonate, 0.001 mol of Mo(SO4)3, 0.999 mol of phosphoric acid with a concentration of 85% in aqueous solution, 0.001 mol of H4SiO4, 0.0005 mol of NH4HF2, and 0.005 mol of sucrose are added to 20 L of deionized water. The mixture is transferred to a sand mill for intensive grinding and stirring for 10 hours, to obtain a slurry. The slurry is transferred to a spray drying device for spray drying and granulation, and the drying temperature is set to 250°C, and the drying is performed for 4 hours, to obtain particles. The above powder is sintered at 700°C for 10 hours in a nitrogen (90 vol.%) + hydrogen (10 vol.%) protective atmosphere, to obtain carbon-coated Li 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.001 O 3.999 F 0.001 The positive electrode active material can be detected for element content by inductively coupled plasma emission spectrometry (ICP).

[0147] Method for producing the first positive electrode active material of Example 14

[0148] Except that the amount of high-purity Li2CO3 is changed to 0.4885 mol, Mo(SO4)3 is replaced by MgSO4, the amount of FeSO4-H2O is changed to 0.68 mol, 0.02 mol of Ti(SO4)2 is added in the preparation of doped manganese oxalate, and H4SiO4 is replaced by HNO3, the other preparation method of the first positive electrode active material of Example 13 is the same.

[0149] Method for producing the first positive electrode active material of Example 15

[0150] Except that the amount of high-purity Li2CO3 is changed to 0.496 mol, Mo(SO4)3 is replaced by W(SO4)3, and H4SiO4 is replaced by H2SO4, the other preparation method of the first positive electrode active material of Example 13 is the same.

[0151]

[0152]

[0153] Battery test

[0154] (1) Test of the thickness of the coating layer:

[0155] The thickness of the coating layer is mainly tested by FIB to cut a thin slice of about 100 nm thickness from the middle of a single particle of the positive electrode active material prepared above, and then the thin slice is tested by TEM to obtain a TEM test original picture, and the original picture format (xx.dm3) is saved.

[0156] The original picture obtained by the above TEM test is opened in DigitalMicrograph software, and the coating layer is identified by the lattice spacing and the included angle information, and the thickness of the coating layer is measured.

[0157] The thickness of the selected particle at three positions is measured, and the average value is taken.

[0158] (2) Test of Dv50 particle size:

[0159] According to the method in the national standard GB / T 19077-2016 "Particle size distribution-laser diffraction method", wherein deionized water is used as the solvent, and ultrasonic treatment is performed for 5 minutes before testing.

[0160] (3) Test of Mn elution amount:

[0161] The battery cycled to 80% capacity fade at 45℃ was discharged to cut-off voltage 2.5V at 0.1C rate. Then the battery was disassembled, and the negative electrode sheet was taken out. 30 pieces of circular sheet with unit area (1540.25mm 2 ) were randomly taken from the negative electrode sheet, and inductively coupled plasma emission spectrometry (ICP) was tested by Agilent ICP-OES730. The amount of Mn was calculated according to the ICP results, so as to calculate the dissolution amount of Mn after cycling. The test standard is based on EPA-6010D-2014.

[0162] (4) Test of cycle performance:

[0163] At a constant temperature environment of 25℃, charge at 0.33C to 4.3V, stand for 10min, then discharge at 1C to 2.5V, and the capacity is recorded as D0. Repeat the foregoing process until the capacity decays to 80% of D0, and record the cycle number at this time. Calculate the percentage increase or decrease in cycle number relative to Comparative Example 1.

[0164] (5) Test of storage performance:

[0165] At a constant temperature environment of 25℃, charge the battery at 0.33C to 4.3V, and then discharge at 0.33C to 2.5V to test the discharge capacity D1; store the battery in a constant temperature environment of 60℃, take it out every 30 days for testing, cool the battery to 25℃ each time, charge at 0.33C to 4.3V, and then discharge at 0.33C to 2.5V to test the discharge capacity, until the discharge capacity decays to 80% of D1, and record the storage days at this time. Calculate the percentage increase or decrease in storage days relative to Comparative Example 1.

[0166] The results of (1) to (2) above are shown in Table 1, and the results of (3) to (5) above are shown in Table 2-3.

[0167] Table 2: Mn dissolution amount and cycle performance test results of Example 1-15 and Comparative Example 1-2

[0168] No. Mn elution amount / ppm Cycling performance Example 1 105 16％ Example 2 416 25％ Example 3 348 103％ Example 4 113 46％ Example 5 367 13％ Example 6 324 12％ Example 7 289 65％ Example 8 267 89％ Example 9 313 53％ Example 10 294 84％ Example 11 297 76％ Example 12 285 72％ Example 13 254 89％ Example 14 283 63％ Example 15 267 97％ Comparative Example 1 786 Reference Comparative Example 2 723 -56％

[0169] Table 3: Storage performance test results of Example 1-15 and Comparative Example 1, 3

[0170] No. Storage performance Example 1 3％ Example 2 7％ Example 3 2％ Example 4 8％ Example 5 4％ Example 6 9％ Example 7 11％ Example 8 21％ Example 9 18％ Example 10 3％ Example 11 6％ Example 12 7％ Example 13 13％ Example 14 11％ Example 15 8％ Comparative Example 1 Reference Comparative Example 3 -48％

[0171] From Tables 2-3, it can be seen that:

[0172] Compared with Comparative Examples 1-2, the Mn dissolution amount of the battery of Examples 1-15 of the application is lower, and the cycle performance is higher;

[0173] Compared with Comparative Examples 1 and 3, the storage performance of the batteries of Examples 1-15 is higher.

[0174] Compared with Examples 5-6, the Mn dissolution amount of the batteries of Examples 7-8 is further reduced, and the cycle performance and storage performance are further improved.

[0175] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and playing the same role and effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. Furthermore, within the scope of the gist of the present application, various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other modes constructed by combining part of the constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode active material composition comprising a first positive electrode active material and a second positive electrode active material; wherein, The first positive electrode active material includes an inner core and a coating layer coating the inner core, the coating layer including one or more of pyrophosphate, phosphate, and carbon, the inner core including a compound Li a A b Mn f B 1-f P 1-d R d O 4-n D n wherein, the A comprises one or more elements of Zn, Al, Na, K, Mg, Nb, Mo, and W; the B comprises one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; the R comprises one or more elements of B (boron), S, Si, and N; the D comprises one or more elements of S, F, Cl, and Br; the a is 0.9 to 1.1; the b is 0 to 0.1; the f is 0.1 to 0.999; the d is 0 to 0.1; the n is 0 to 0.1; The second positive electrode active material includes a compound LiNi x Co y M 1-x-y O2, wherein M includes one or more elements of Al, Mn, Mg, Nb, Ti, and Ba; 0.5≤x≤0.69; 0<y<0.

31. and satisfies: 0.018m + 0.003f < z < 0.02m + 0.02f wherein, the m represents a mass percentage of the first positive electrode active material in the positive electrode active material composition; the z represents a ratio of a coating layer thickness to a Dv50 particle diameter of the first positive electrode active material.

2. The positive electrode active material composition according to claim 1, wherein, the B comprises one or more elements of Fe, Ti, V, Ni, Co, and Mg.

3. The positive electrode active material composition according to claim 1, wherein, the a is 0.977 to 1.

4. The positive electrode active material composition according to claim 1, wherein, the b is 0 to 0.

001.

5. The positive electrode active material composition according to claim 1, wherein, the f is 0.1 to 0.

9.

6. The positive electrode active material composition according to claim 1, wherein, the d is 0 to 0.001 or 0.001 to 0.

1.

7. The positive electrode active material composition according to claim 1, wherein, the n is 0 to 0.001 or 0.001 to 0.

1.

8. The positive electrode active material composition according to claim 1, wherein, the coating layer thickness of the first positive electrode active material is 2-15 nm.

9. The positive electrode active material composition according to claim 1, wherein, the coating layer thickness of the first positive electrode active material is 5-11 nm.

10. The positive electrode active material composition according to claim 1, wherein, the Dv50 particle diameter of the first positive electrode active material is 400-1600 nm.

11. The positive electrode active material composition according to claim 1, wherein, the Dv50 particle diameter of the first positive electrode active material is 420-730 nm.

12. The positive electrode active material composition according to claim 1, wherein, the f is 0.3 to 0.

8.

13. The positive electrode active material composition according to claim 1, wherein, the coating layer in the first positive electrode active material comprises carbon.

14. The positive electrode active material composition according to any one of claims 1 to 13, wherein, the m is 30%-80%.

15. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer comprising the positive electrode active material composition of any one of claims 1 to 14.

16. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material; wherein, at least one of the positive electrode film layers has a multi-layer structure, and at least one of the positive electrode film layers having a multi-layer structure respectively comprises a first positive electrode active material and a second positive electrode active material in different layers, the first positive electrode active material and the second positive electrode active material being as described in any one of claims 1 to 13; and satisfies: 0.018m’ + 0.003f < z < 0.02m’ + 0.02f wherein, the m’ represents a mass percentage of the first positive electrode active material in the positive electrode active material; the z represents a ratio of a coating layer thickness to a Dv50 particle diameter of the first positive electrode active material.

17. The positive electrode sheet according to 16, wherein the m’ is 30%-80%.

18. A battery comprising the positive electrode active material composition of any one of claims 1 to 14 or the positive electrode sheet of any one of claims 15 to 17.

19. An electrical device comprising the positive electrode active material composition of any one of claims 1 to 14, the positive electrode web of any one of claims 15 to 17, or the battery of claim 18.

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