Composite positive electrode material and preparation method therefor, positive electrode sheet, battery, and electric device

Abstract

The present disclosure relates to the technical field of batteries. The present disclosure provides a composite positive electrode material and a preparation method therefor, and a positive electrode sheet, a battery, and an electric device. The composite positive electrode material comprises a first component and a second component; the first component comprises at least one of LiFePO4, LiCoPO4, LiMnPO4, LiNiPO4, and LiMnxFe1-xPO4, wherein 0.2≤x≤0.8; the second component comprises LiNiyM1 zM2 1-y-zO2, wherein M1 comprises at least one of Co, Al, and Mn, M2 comprises at least one of Co, Al, and Mn, 0<y<1, and 0<z<1; the mass ratio of the first component to the second component is (9-5):(1-5).

Description

Composite cathode materials and their preparation methods, cathode sheets, batteries and electrical devices

[0001] Priority information

[0002] This disclosure claims priority and benefits to patent application No. 2024115521185, filed with the China National Intellectual Property Administration on October 31, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure belongs to the field of battery technology, specifically relating to a composite cathode material and its preparation method, as well as cathode sheets, batteries, and electrical devices. Background Technology

[0004] Electrodeless lithium batteries are a new battery technology that may not directly use traditional negative electrode materials, but they still require a structure or region capable of receiving and releasing lithium ions. By avoiding the direct use of lithium metal, electrodeless lithium batteries greatly simplify the production process and reduce production costs, thus attracting widespread attention as a novel type of battery.

[0005] However, the relevant technologies are limited to research on lithium deposition behavior, improving cycle life and capacity, while there are few reports on how to improve the safety of electrodeless lithium batteries.

[0006] Public content

[0007] This disclosure aims to address, at least to some extent, the safety issues of electrodeless lithium batteries. To this end, one objective of this disclosure is to provide a composite cathode material and its preparation method, as well as a cathode sheet, battery, and electrical device. This composite cathode material exhibits good thermal stability, enabling electrodeless lithium batteries to demonstrate excellent safety performance.

[0008] This disclosure provides a composite cathode material. According to embodiments of this disclosure, the composite cathode material includes a first component and a second component; the first component includes LiFePO4 (lithium iron phosphate), LiCoPO4 (lithium cobalt phosphate), LiMnPO4 (lithium manganese phosphate), LiNiPO4 (lithium nickel phosphate), and LiMn... x Fe 1-x At least one of PO4 (lithium iron manganese phosphate); wherein 0.2 ≤ x ≤ 0.8; the second component includes LiNi y M 1 z M 2 1-y-z O2; where M 1 Including at least one of Co, Al and Mn, M 2It includes at least one of Co, Al, and Mn, where 0 < y < 1 and 0 < z < 1; the mass ratio of the first component to the second component is (9 - 5) : (1 - 5).

[0009] The composite cathode material provided by the embodiments of the present disclosure is conducive to improving the safety of the battery. By mixing the first component with the second component as the main cathode active material, on the one hand, it is conducive to reducing the chance of direct contact between the electrolyte and the main cathode active material (i.e., the second component), improving the structural stability of the main cathode active material; on the other hand, the first component has an olivine structure and relatively high thermal stability, which is conducive to hindering the chain reaction during the thermal runaway of the main cathode active material, thereby improving the safety of battery use. The composite cathode material provided by the embodiments of the present disclosure exhibits good electrochemical performance. In the composite cathode material of the embodiments of the present disclosure, the first component and the second component materials have similar voltage platforms, so the composite cathode material obtained by the compounding of these two components can still maintain a relatively high capacity.

[0010] According to the embodiments of the present disclosure, the above composite cathode material may further include at least one of the following additional technical features:

[0011] In some embodiments, the mass ratio of the first component to the second component is (7 - 5) : (3 - 5).

[0012] In some embodiments, LiNi y M 1 z M 2 1-y-z O2, where M 1 is one of Co, Al, and Mn, M 2 is one of Co, Al, and Mn, and M 1 and M 2 are different.

[0013] In some embodiments, the first component is LiMn x Fe 1-x PO4.

[0014] In some embodiments, the particle size of the first component is smaller than that of the second component.

[0015] The second aspect of the present disclosure provides a positive electrode sheet including the above composite cathode material.

[0016] The positive electrode sheet provided by the present disclosure contains the above composite cathode material and exhibits good electrochemical performance and safety performance.

[0017] In some embodiments, the positive electrode sheet includes a positive electrode current collector and an active material layer, and the active material layer includes the above composite cathode material.

[0018] In some embodiments, the composite cathode material has a mass percentage content of 90wt% to 95wt% in the active material layer.

[0019] A third aspect of this disclosure provides a battery including the aforementioned positive electrode.

[0020] The battery disclosed herein exhibits good safety and high electrochemical performance.

[0021] In some embodiments, the battery further includes a negative electrode plate, which includes a negative current collector.

[0022] In some embodiments, the negative current collector includes at least one of copper foil, porous copper foil, and brass foil.

[0023] In some implementations, the battery is a negative electrode-free lithium battery.

[0024] A fourth aspect of this disclosure provides an electrical device comprising the battery described above.

[0025] Electrical equipment can be electric vehicles, electric motorcycles, electric bicycles, mobile phones, computers, cameras, e-book players, or wearable devices.

[0026] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Detailed Implementation

[0027] The embodiments of this disclosure are described in detail below. The embodiments described below are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure.

[0028] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] In this text, the term "comprising" or "including" is an open expression, that is, it includes the content specified in this disclosure, but does not exclude other aspects.

[0031] In this text, the terms "optionally", "optional" or "option" generally mean that the subsequent events or conditions may or may not occur, and this description includes the cases where the events or conditions occur, as well as the cases where the events or conditions do not occur.

[0032] The solutions of this disclosure will be explained below in conjunction with embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate this disclosure and should not be regarded as limiting the scope of this disclosure. For those not specified in the embodiments in terms of specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0033] The lithium metal-free lithium battery avoids the direct use of a lithium metal anode, greatly simplifies the production process and reduces the production cost, and thus has received extensive attention as a new type of battery. Since the lithium metal-free battery does not have the buffer of the traditional active material layer at the anode, when the battery undergoes thermal runaway, the heat increases rapidly, and there is an easy risk of fire. In the related technologies, the research is limited to aspects such as lithium deposition behavior, improving cycle life and capacity increase, and there are few reports on how to improve the safety of lithium metal-free lithium batteries. The above traditional active materials refer to graphite, hard carbon, silicon-based materials, etc. used in current batteries.

[0034] In a first aspect of an embodiment of this disclosure, a composite cathode material is provided, including a first component and a second component; the first component includes at least one of LiFePO4 (lithium iron phosphate), LiCoPO4 (lithium cobalt phosphate), LiMnPO4 (lithium manganese phosphate), LiNiPO4 (lithium nickel phosphate) and LiMn x Fe 1-x PO4 (lithium manganese iron phosphate); where 0.2 ≤ x ≤ 0.8; the second component includes LiNi y M 1 z M 2 1-y-z O2; where M 1 includes at least one of Co, Al and Mn, M 2 includes at least one of Co, Al and Mn, 0 < y < 1, 0 < z < 1; the mass ratio of the first component to the second component is (9 - 5):(1 - 5).

[0035] The composite cathode material provided by this disclosure improves battery safety. By mixing a first component with a second component, which serves as the primary cathode active material, this disclosure reduces the direct contact between the electrolyte and the primary cathode active material (i.e., the second component), thus improving the structural stability of the primary cathode active material. Furthermore, it helps to prevent chain reactions that occur during thermal runaway of the primary cathode active material, thereby enhancing battery safety. In addition, the first component is entirely composed of olivine, exhibiting high thermal stability, which significantly contributes to the overall safety improvement of the composite cathode material. The primary cathode active material mentioned above refers to cathode active materials commonly used in linear battery systems.

[0036] The composite cathode material provided by this disclosure exhibits excellent electrochemical performance. In the composite cathode material of this disclosure, the first component and the second component have similar voltage plateaus, so the composite cathode material obtained by combining these two components can still maintain a high capacity.

[0037] In this embodiment, the mass ratio of the first component and the second component conforms to the above design, which facilitates separation and barrier functions, promotes uniform dispersion, and effectively prevents chain reactions during battery thermal runaway. Furthermore, in the mass ratio of the first component and the second component, the sum of the first and second terms is 10.

[0038] In this embodiment of the disclosure, the second component includes LiNi. y M 1 z M 2 1-y-z O2; where M 1 and M 2 They can be the same or different.

[0039] If M 1 and M 2 If they are the same, then the second component is a binary material, namely a binary active cathode material.

[0040] If M 1 and M 2 If they are different, then the second component is a ternary material, namely a ternary active cathode material.

[0041] In specific examples, the mass ratio of the first component to the second component is 9:1, 8:2, 7:3, 6:4, 5:5, etc.

[0042] In some embodiments, the mass ratio of the first component to the second component is (7-5):(3-5). Further, the sum of the antecedent and consequent of the mass ratio is 10.

[0043] In this embodiment, the mass ratio of the first component and the second component conforms to the aforementioned range, which is beneficial for further enhancing the separation and barrier effects, effectively preventing chain reactions during thermal runaway. Based on the inherent thermal stability of the first component, adding a larger amount of the first component effectively improves the overall safety of the composite cathode material without affecting the normal use of the battery.

[0044] In some embodiments, the second component is LiNi y M 1 z M 2 1-y-z O2, where M 1 It is one of Co, Al and Mn, M 2 It is one of Co, Al and Mn, and M 1 and M 2 They are not the same.

[0045] As a widely used cathode material, the ternary active cathode material in this embodiment is used in combination with the first component and applied to the battery. It exhibits good electrochemical performance and high safety, and has important market application value.

[0046] In some embodiments, the first component is LiMn x Fe 1-x PO4, where 0.2≤x≤0.8.

[0047] In this embodiment, lithium manganese iron phosphate is used as the first component, which is closer to the voltage platform of the second component ternary active cathode material and has an olivine structure, which is beneficial to obtaining better safety and better electrochemical performance.

[0048] In some embodiments, the particle size of the first component is smaller than that of the second component.

[0049] In this embodiment of the disclosure, by dispersing the smaller particle size of the first component among the larger particle size of the second component, the particles of the second component are effectively dispersed and isolated. On the one hand, this helps to reduce direct contact between the electrolyte and the second component, thereby improving the stability of the second component structure; on the other hand, it effectively prevents the chain reaction that occurs in the second component during thermal runaway, which is beneficial to improving safety.

[0050] In this embodiment of the disclosure, the average particle size of the first component may be greater than the average particle size of the second component, and the average particle size may be expressed as D. 50 express.

[0051] In specific examples, the average particle size of the first component is between 200 nm and 400 nm, and the average particle size of the second component is between 3 μm and 5 μm; or, the average particle size of the first component is 300 nm, and the average particle size of the second component is 5 μm; or, the average particle size of the first component is 100 nm, and the average particle size of the second component is 1 μm, etc.

[0052] In the second aspect of the embodiments of the present disclosure, a preparation method of a composite cathode material is provided, including: physically mixing a first component and a second component to obtain a composite cathode material; the first component includes at least one of LiFePO4, LiCoPO4, LiMnPO4, LiNiPO4, and LiMn x Fe 1-x PO4; where 0.2 ≤ x ≤ 0.8; the second component includes LiNi y M 1 z M 2 1-y-z O2; where M 1 includes at least one of Co, Al, and Mn, M 2 includes at least one of Co, Al, and Mn, 0 < y < 1, 0 < z < 1; the mass ratio of the first component to the second component is (9 - 5):(1 - 5).

[0053] In the embodiments of the present disclosure, the first component is physically mixed with the second component as the cathode active material. On the one hand, it is beneficial to reduce the chance of direct contact between the electrolyte and the cathode active material (i.e., the second component), and improve the structural stability of the cathode active material; on the other hand, it is beneficial to hinder the chain reaction that occurs when the cathode active material is out of control thermally, thereby improving the safety of battery use. In addition, the first component has an olivine structure and has relatively high thermal stability, which plays a very good role in improving the overall safety of the composite cathode material.

[0054] The composite cathode material provided by the embodiments of the present disclosure exhibits good electrochemical performance. In the composite cathode material of the embodiments of the present disclosure, the first component and the second component materials have similar voltage platforms, so the composite cathode material obtained by the compounding of these two components can still maintain a relatively high capacity.

[0055] The preparation method provided by the embodiments of the present disclosure directly physically mixes the first component and the second component, has a simple process, is convenient to operate, has a low production cost, and is conducive to large-scale production.

[0056] In some embodiments, the physical mixing method includes mechanical mixing, solution co-blending, powder mixing, etc., and can be a single physical mixing method or a combination of multiple physical mixing methods.

[0057] In this embodiment, the mass ratio of the first component to the second component is (9-5):(1-5). In specific examples, the mass ratio of the first component to the second component is 9:1, 8:2, 7:3, 6:4, 5:5, etc. In this embodiment, the mass ratio of the first component to the second component conforms to the above design, which is beneficial to fully exert the separation and barrier effects, promote uniform dispersion, and effectively prevent chain reactions during thermal runaway. Further, the sum of the first and second terms of the mass ratio of the first component to the second component is 10.

[0058] In some embodiments, the mass ratio of the first component to the second component is (7-5):(3-5). Further, the sum of the antecedent and consequent of the mass ratio is 10.

[0059] In this embodiment, the mass ratio of the first component and the second component conforms to the aforementioned range, which is beneficial for further enhancing the separation and barrier effects and effectively preventing chain reactions during thermal runaway. Based on the inherent thermal stability of the first component, adding a larger amount of the first component effectively improves the overall safety of the composite cathode material.

[0060] In some implementations, LiNi y M 1 z M 2 1-y-z O2, where M 1 It is one of Co, Al and Mn, M 2 It is one of Co, Al and Mn, and M 1 and M 2 They are not the same.

[0061] In some implementations, LiNi y M 1 z M 2 1-y-z O2, where M 1 It is one of Co, Al and Mn, M 2 It is one of Co, Al and Mn, and M 1 and M 2 Not the same; and / or, the first component is LiMn x Fe 1-x PO4.

[0062] As a widely used cathode material, the ternary active cathode material in this embodiment is used in combination with the first component and applied to the battery. It exhibits good electrochemical performance and high safety, and has important market application value.

[0063] In a specific example, LiNi y M1 z M 2 1-y-z O2, where M 1 It is one of Co, Al and Mn, M 2 It is one of Co, Al and Mn, and M 1 and M 2 They are not the same; and the first component is LiMn. x Fe 1-x PO4.

[0064] In this embodiment, lithium manganese iron phosphate is used as the first component, which is closer to the voltage platform of the second component ternary active cathode material and has an olivine structure, which is beneficial to obtaining better safety and better electrochemical performance.

[0065] A third aspect of this disclosure provides a positive electrode sheet comprising the composite positive electrode material described above, or comprising the composite positive electrode material obtained by the preparation method described above.

[0066] The positive electrode provided in this embodiment contains the above-mentioned composite positive electrode material and exhibits good electrochemical and safety performance.

[0067] In some embodiments, the positive electrode sheet includes a positive current collector and an active material layer, wherein the active material layer includes the composite positive electrode material described above, or the composite positive electrode material obtained by the preparation method described above.

[0068] In this embodiment of the disclosure, the active material layer containing the above-mentioned composite positive electrode material can be combined with the positive electrode current collector to form a positive electrode sheet.

[0069] In some implementations, the positive current collector includes a positive metal current collector.

[0070] Furthermore, the positive electrode metal current collector includes an aluminum foil with a conductive coating on its surface. Even further, the conductive coating is at least one of graphene, acetylene black, and carbon nanotubes, and the thickness of the conductive coating is 2 μm to 5 μm. The base coating on the aluminum foil, besides increasing the conductivity of the positive electrode and improving the battery rate performance, plays a crucial role in this disclosure by acting as a buffer medium to buffer heat dissipation during battery thermal runaway, thereby increasing battery safety performance.

[0071] In some embodiments, the composite cathode material has a mass percentage content of 90wt% to 95wt% in the active material layer.

[0072] In this embodiment of the disclosure, the mass percentage of the composite cathode material in the active material layer is 90wt% to 95wt%, which is beneficial for obtaining a cathode sheet with good electrochemical performance. In specific examples, the mass percentage of the composite cathode material in the active material layer is 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, or 95wt%, etc.

[0073] In some embodiments, the active material layer also includes a binder and a conductive agent.

[0074] Furthermore, the binder has a mass percentage content of 1wt% to 5wt% in the active material layer, and the conductive agent has a mass percentage content of 2wt% to 5wt% in the active material layer.

[0075] Furthermore, the adhesive includes at least one of polytetrafluoroethylene and polyvinylidene fluoride.

[0076] Furthermore, the conductive agent includes at least one of graphene, acetylene black, carbon fiber, and carbon nanotubes.

[0077] A fourth aspect of this disclosure provides a battery including the positive electrode sheet described above.

[0078] The battery provided by the embodiments of this disclosure exhibits good safety and high electrochemical performance.

[0079] In some embodiments, the battery further includes a negative electrode plate, which includes a negative current collector.

[0080] In some implementations, the battery is a negative electrode-free lithium battery.

[0081] In some embodiments, the negative electrode current collector includes at least one of copper foil, porous copper foil, and brass foil. Further, the thickness of the negative electrode current collector is 8 μm to 12 μm.

[0082] In some implementations, the battery is a negative electrode-free lithium battery.

[0083] The battery provided in this embodiment is a negative electrode-free lithium battery. Applying the above-mentioned composite positive electrode material to the negative electrode-free lithium battery can effectively improve its safety performance.

[0084] In electrodeless lithium batteries, there is no conventional negative electrode active material layer (graphite, silicon) on the negative electrode current collector. The negative electrode current collector can be used to accept lithium ions released from the positive electrode active material, thereby achieving energy storage. Therefore, the thickness of the negative electrode current collector not only affects the current conduction of the negative electrode sheet but also the safety of the battery. In this disclosure, regarding the safety of electrodeless lithium batteries, an appropriate current collector thickness is beneficial for balancing resistance and reducing heat dissipation during battery thermal runaway.

[0085] This disclosure applies the aforementioned composite cathode material to a cathode-less lithium battery, exhibiting high safety and further improving capacity and cycle performance. Simultaneously, the simplification of the composite cathode material and cathode-less lithium battery manufacturing process significantly reduces production costs. Therefore, the battery is inexpensive while possessing high capacity, making it suitable for large-scale production.

[0086] The fifth aspect of this disclosure provides an electrical device comprising the battery described above.

[0087] In specific examples, the electrical equipment can be an electric vehicle, an electric motorcycle, an electric bicycle, a mobile phone, a computer, a camera, an e-book player, or a wearable device.

[0088] The present disclosure will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present disclosure in any way.

[0089] Example 1

[0090] This embodiment provides a composite cathode material, the raw materials of which are: 90 wt% lithium iron manganese phosphate (LFMP) and 10 wt% ternary material NCM712 (LiNi). 0.7 Co 0.1 Mn 0.2 O2).

[0091] Example 2

[0092] This embodiment provides a composite cathode material, the raw materials of which are: 80 wt% lithium iron manganese phosphate (LFMP) and 20 wt% ternary material NCM712 (LiNi). 0.7 Co 0.1 Mn 0.2 O2).

[0093] Example 3

[0094] This embodiment provides a composite cathode material, the raw materials of which are: 70 wt% lithium iron manganese phosphate (LFMP) and 30 wt% ternary material NCM712 (LiNi). 0.7 Co 0.1 Mn 0.2 O2).

[0095] Example 4

[0096] This embodiment provides a composite cathode material, the raw materials of which are: 60 wt% lithium iron manganese phosphate (LFMP) and 40 wt% ternary material NCM712 (LiNi). 0.7 Co 0.1 Mn 0.2 O2).

[0097] Example 5

[0098] This embodiment provides a composite cathode material, the raw materials of which are: 50 wt% lithium iron manganese phosphate (LFMP) and 50 wt% ternary material NCM712 (LiNi). 0.7 Co 0.1 Mn 0.2 O2).

[0099] Example 6

[0100] This embodiment provides a composite cathode material, the raw materials of which are: 50 wt% lithium iron phosphate (LFP) and 50 wt% ternary material NCM712 (LiNi). 0.7 Co 0.1 Mn 0.2 O2).

[0101] Example 7

[0102] This embodiment provides a composite cathode material, the raw materials of which are: 50 wt% lithium iron manganese phosphate (LFMP) and 50 wt% binary material NM55 (LiNi). 0.5 Mn 0.5 O2).

[0103] In Examples 1-7 above, the average particle size of the first component is 400 nm, and the average particle size of the second component is 3 μm.

[0104] Comparative Example 1

[0105] This comparative example provides a cathode material, the raw materials of which are: 0 wt% lithium iron manganese phosphate (LFMP) and 100 wt% ternary material NCM712 (LiNi). 0.7 Co 0.1 Mn 0.2 O2), the average particle size of the ternary material is 3μm.

[0106] Comparative Example 2

[0107] This comparative example provides a cathode material, the raw materials being: 100 wt% lithium iron manganese phosphate (LFMP) and 0 wt% ternary material NCM712 (LiNi). 0.7 Co 0.1 Mn 0.2 The average particle size of lithium iron manganese phosphate (O2) is 400 nm.

[0108] Comparative Example 3

[0109] This embodiment provides a composite cathode material, the raw materials of which are: 40 wt% lithium iron manganese phosphate (LFMP) and 60 wt% ternary material NCM712 (LiNi). 0.7 Co0.1 Mn 0.2 The average particle size of lithium iron manganese phosphate (O2) is 400 nm, while the average particle size of ternary materials is 3 μm.

[0110] Application Cases

[0111] This embodiment provides a battery, and the specific preparation method is shown below:

[0112] Positive electrode sheet: Polytetrafluoroethylene (PTFE) binder was dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 1:16 and stirred at 2000 rpm for 2 hours to obtain a slurry with a viscosity of 2500 mPa·s. Graphene, a conductive agent, was then added to the slurry and stirred at 2000 rpm for 2 hours. Next, the positive electrode materials provided in Examples 1-7 and Comparative Examples 1-3 were added and stirred under vacuum at 2000 rpm for 4 hours. NMP was then added and stirred slowly to adjust the slurry viscosity to the required level before vacuum defoaming. The prepared mixed positive electrode slurry was coated onto an aluminum foil with a conductive coating. The carbon coating layer on the conductive aluminum foil was 3 μm thick. After coating, the foil was rolled, slit, and die-cut to obtain positive electrode sheets. The mass ratio of the composite positive electrode material, binder, and conductive agent was 95:2:3.

[0113] Negative electrode current collector: a copper foil current collector with a thickness of 8μm.

[0114] Separator: PE (polyethylene) separator with a thickness of 12μm.

[0115] Battery assembly: The positive electrode sheet, negative current collector, and separator are stacked to form a battery cell. The positive and negative electrode tabs are welded out, and then the battery cell is placed in an aluminum-plastic film. After baking, electrolyte is injected, and after processes such as encapsulation, formation, and capacity testing, a 10Ah soft-pack battery is produced.

[0116] The batteries prepared using the composite cathode materials of Examples 1-7 were named 1#, 2#, 3#, 4#, 5#, 6# and 7# respectively; the batteries prepared using the cathode materials of Comparative Examples 1-3 were named D1#, D2# and D3# respectively.

[0117] Performance testing:

[0118] 1. Testing methods.

[0119] (1) Capacity test method: The battery obtained above was tested at an ambient temperature of 25±3℃. It was charged to 4.3V at 0.2C and then discharged to 2.7V at 0.5C. The average discharge capacity of the positive electrode material in the first three tests was calculated.

[0120] (2) Safety performance test method: According to the national standard GB38031-2020, the above-obtained batteries were tested, and the batteries were charged to 100% SOC for nail penetration, furnace temperature and overcharge tests.

[0121] (3) Cyclic performance test method: Charge to 4.3V with constant current and constant voltage at 0.2C, then discharge at 0.5C, cycle at 80% DOD (depth of discharge), and record the number of cycles of the battery with 80% cycle retention rate.

[0122] 2. Test results.

[0123] The results of capacity testing, cycle testing, and safety performance testing are shown in Table 1.

[0124] Table 1 Performance Test Results

[0125] As shown in Table 1, the composite material prepared by incorporating lithium manganese iron phosphate into ternary materials, when used in batteries, exhibited no thermal runaway in the needle penetration test. Furthermore, the battery surface temperature decreased significantly with increasing manganese iron phosphate ratio. In summary, the incorporation of lithium manganese iron phosphate effectively inhibits the chain reaction that occurs in ternary materials during thermal runaway, improving the overall thermal stability of the mixed cathode material and resulting in excellent safety performance of the electrodeless lithium battery.

[0126] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A composite cathode material, comprising a first component and a second component; The first component includes LiFePO4, LiCoPO4, LiMnPO4, LiNiPO4, and LiMn. x Fe 1-x At least one of PO4; wherein, 0.2≤x≤0.8； The second component includes LiNi y M 1 z M 2 1-y-z O2; where M 1 Including at least one of Co, Al and Mn, M 2 Including at least one of Co, Al and Mn, 0 <y<1,0<z<1; The mass ratio of the first component to the second component is (9-5):(1-5).

2. The composite cathode material according to claim 1, wherein, The mass ratio of the first component to the second component is (7-5):(3-5).

3. The composite cathode material according to claim 1 or 2, wherein, The LiNi y M 1 z M 2 1-y-z O2, where M 1 It is one of Co, Al and Mn, M 2 It is one of Co, Al and Mn, and M 1 and M 2 They are not the same.

4. The composite cathode material according to any one of claims 1 to 3, wherein, The first component is LiMn x Fe 1-x PO4.

5. The composite cathode material according to any one of claims 1 to 4, wherein, The particle size of the first component is smaller than that of the second component.

6. A positive electrode sheet comprising the composite positive electrode material as described in any one of claims 1 to 5.

7. The positive electrode sheet according to claim 6, comprising a positive current collector and an active material layer, wherein the active material layer comprises the composite positive electrode material according to any one of claims 1 to 5.

8. The positive electrode sheet according to claim 7, wherein, The composite cathode material has a mass percentage content of 90wt% to 95wt% in the active material layer.

9. A battery comprising the positive electrode sheet as described in any one of claims 6 to 8.

10. The battery according to claim 9, further comprising a negative electrode sheet, the negative electrode sheet comprising a negative current collector.

11. The battery according to claim 9 or 10, wherein, The negative electrode current collector includes at least one of copper foil, porous copper foil, and brass foil.

12. The battery according to any one of claims 9 to 11, wherein, The battery is a negative electrode-free lithium battery.

13. An electrical device comprising the battery as described in any one of claims 9 to 12.

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