Composite cathode materials and their preparation methods, secondary batteries, battery packs containing the secondary batteries, and electrical devices thereof.

Abstract

This application provides a composite cathode material and its preparation method, a secondary battery, a battery pack comprising the secondary battery, and an electrical device. The composite cathode material includes a lithium-rich metal oxide and a cathode active material covering at least a portion of the surface of the lithium-rich metal oxide, wherein the cathode active material is formed by an in-situ reaction of a cathode active material precursor with a free lithium compound on the surface of the lithium-rich metal oxide.

Description

Technical Field

[0001] This application belongs to the field of energy storage device technology, specifically relating to a composite cathode material and its preparation method, a secondary battery and a battery pack and electrical device containing the secondary battery. Background Technology

[0002] In recent years, with the application and promotion of rechargeable batteries in various electronic products and new energy vehicles, their capacity and cycle life have received increasing attention. However, during the first charge and discharge process of a rechargeable battery, an SEI (solid electrolyte interface) film inevitably forms on the negative electrode, causing the consumption of active ions. The resulting irreversible capacity loss is difficult to eliminate, thus reducing the initial discharge capacity and posing a challenge to improving the cycle life of rechargeable batteries. Summary of the Invention

[0003] The first aspect of this application provides a method for preparing a composite cathode material, which includes the following steps:

[0004] Provide core materials, including lithium-rich metal oxides, the surface of which contains free lithium compounds;

[0005] Provide precursors for positive electrode active materials;

[0006] The positive electrode active material precursor is attached to at least a portion of the surface of the core material;

[0007] A composite cathode material is obtained by reacting a precursor of the cathode active material with a free lithium compound to form a cathode active material on at least a portion of the surface of a lithium-rich metal oxide.

[0008] In the composite cathode material preparation method provided in this application, the cathode active material precursor is generated in situ on the surface of lithium-rich metal oxide to consume free lithium compounds on the surface of lithium-rich metal oxide, thereby reducing the pH value. This avoids the slurry gelation problem caused by the strong alkalinity of lithium-rich metal oxide and improves the processing performance of cathode slurry and cathode film. The outer shell of cathode active material coating is dense and uniform, and has a tight bond with lithium-rich metal oxide, thus providing more effective coating and protection for lithium-rich metal oxide and improving its stability. The cathode active material coating is a good lithium-ion conductor, thus facilitating the extraction of lithium ions from the core lithium-rich metal oxide. Therefore, the core lithium-rich metal oxide can release more active lithium ions, effectively compensating for the active lithium consumption during the formation of the SEI film in the negative electrode. The excess active lithium ions are embedded in the negative electrode, placing the negative electrode active material in a certain lithium-intercalation state, which can alleviate the volume change of the negative electrode active material to a certain extent and can also be used to compensate for the active lithium loss during battery cycling in the middle and later stages of cycling. Therefore, the composite cathode material prepared according to the method of this application can improve the first charge-discharge capacity, first coulombic efficiency and cycle life of the battery.

[0009] In any embodiment of this application, the free lithium compound includes one or more of Li₂O, LiOH, and Li₂CO₃, and the mass percentage of the free lithium compound in the core material, as determined by titration, is 0.5 wt% to 15 wt%, optionally 1 wt% to 10 wt%, and even more optionally 3 wt% to 7 wt%. When the content of the free lithium compound in the core material is within an appropriate range, the initial discharge capacity and cycle life of the secondary battery can be further improved.

[0010] In any embodiment of this application, the mass ratio of the core material to the positive electrode active material precursor is 30:1 to 2:1, optionally 25:1 to 10:1. Maintaining a suitable ratio of core material to positive electrode active material precursor can further improve the initial charge-discharge capacity and cycle life of the secondary battery.

[0011] In any embodiment of this application, the volume average particle size D of the core material v 50 is 1μm to 10μm, optionally 2μm to 8μm, and also optionally 3μm to 6μm. The core material's D... v Within an appropriate range, 50 can further improve the initial charge / discharge capacity and cycle life of secondary batteries.

[0012] In any embodiment of this application, the volume average particle size D of the positive electrode active material precursor is... vThe micrometer diameter (D) of the positive electrode active material precursor is 0.05 μm to 3 μm, optionally 0.05 μm to 1.5 μm, and also optionally 0.1 μm to 1.2 μm. v Within an appropriate range, 50 can further improve the initial charge / discharge capacity and cycle life of secondary batteries.

[0013] In any embodiment of this application, the water content of the core material is ≤500ppm, optionally ≤200ppm. Lower water content in the core material allows it to maintain a higher lithium replenishment capacity, while also facilitating the generation of a high-purity positive electrode active material and uniform coating of lithium-rich metal oxides. Therefore, the secondary battery achieves higher overall performance.

[0014] In any embodiment of this application, the lithium-rich metal oxide is selected from Li2M 1 O2, Li2M 2 O3, Li3M 3 O4, Li5M 4 O4, Li6M 5 One or more of O4, of which M 1 Including one or more of Ni, Co, Fe, Mn, Zn, Mg, Ca, and Cu, M 2 Includes one or more of Mn, Sn, Mo, Ru, and Ir, M 3 Including one or more of V, Nb, Cr, and Mo, M 4 Including one or more of Fe, Cr, V, and Mo, M 5 Including one or more of Co, V, Cr, and Mo, the valence state of each metal element except Li in lithium-rich metal oxides is lower than its highest oxidation state.

[0015] In any embodiment of this application, the lithium-rich metal oxide is selected from Li2NiO2, Li2CuO2, Li2Ni a Cu b M 1-a-b One or more of O2, Li2MnO2, Li3VO4, Li3NbO4, Li5FeO4, and Li6CoO4, optionally selected from Li2NiO2, Li2CuO2, and Li2Ni a Cu b M 1-a-bOne or more of O2, Li5FeO4, and Li6CoO4, wherein 0 < a < 1, 0 < b < 1, and 0.9 < a ​​+ b ≤ 1, and M is selected from one or more of Zn, Sn, Mg, Fe, and Mn; optionally, 0.4 ≤ a ≤ 0.8 and 0.2 ≤ b ≤ 0.6; further optionally, 0.5 ≤ a ≤ 0.7 and 0.3 ≤ b ≤ 0.5. These lithium-rich metal oxides have high capacity, thus further improving the battery's initial charge-discharge capacity, initial coulombic efficiency, and cycle life.

[0016] In any embodiment of this application, the positive electrode active material precursor is selected from one or more of transition metal oxides, transition metal hydroxides, transition metal carbonates, and transition metal phosphates; optionally, the positive electrode active material precursor is selected from Ni. x1 Co y1 Mn z1 (OH)2, Ni x2 Co y2 Al z2 (OH)2, Ni x3 Co y3 Mn z3 CO3, Ni x4 Co y4 Al z4 One or more of CO3 and MPO4, and optionally further selected from Ni x1 Co y1 Mn z1 (OH)2, Ni x2 Co y2 Al z2 One or more of (OH)2 and MPO4, wherein x1+y1+z1=1; x2+y2+z2=1; x3+y3+z3=1; x4+y4+z4=1; M is selected from one or more of Fe, Ni, Co, and Mn.

[0017] In any embodiment of this application, the positive electrode active material precursor is selected from one or more of transition metal oxides, transition metal hydroxides, and transition metal carbonates, and the volume average particle size D of the positive electrode active material precursor is... v 50 is 0.5μm to 1.2μm, and optionally 0.6μm to 1μm.

[0018] In any embodiment of this application, the positive electrode active material precursor is selected from one or more transition metal phosphates, and the volume average particle size D of the positive electrode active material precursor is... v 50 is 0.1μm to 1μm, and optionally 0.4μm to 0.6μm.

[0019] In any embodiment of this application, reacting the positive electrode active material precursor with the free lithium compound includes: heat treatment at 600°C to 800°C for 2 to 8 hours under a protective gas atmosphere.

[0020] A second aspect of this application provides a composite cathode material obtained using the preparation method of the first aspect of this application. The composite cathode material includes a lithium-rich metal oxide and a cathode active material covering at least a portion of the surface of the lithium-rich metal oxide. Using the composite cathode material of this application can improve the initial charge-discharge capacity, initial coulombic efficiency, and cycle life of the battery.

[0021] A third aspect of this application provides a secondary battery, which includes a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on the positive current collector, the positive electrode film layer including at least a first positive electrode material, the first positive electrode material including the composite positive electrode material of this application.

[0022] The secondary battery of this application, due to the use of the composite cathode material of this application, can simultaneously achieve high initial charge-discharge capacity, high initial coulombic efficiency, and long cycle performance.

[0023] In any embodiment of this application, the positive electrode film layer further comprises a second positive electrode material, which includes one or more of lithium transition metal oxides and polyanionic positive electrode materials. In some embodiments, the lithium transition metal oxide may be selected from one or more of lithium cobalt oxide, lithium nickel oxide, layered lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, spinel lithium manganese oxide, spinel lithium nickel manganese oxide, and modified materials thereof. In some embodiments, the polyanionic positive electrode material may be selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium nickel phosphate, lithium manganese iron phosphate, and modified materials thereof. The inclusion of a second positive electrode material in the positive electrode film layer increases the proportion of positive electrode active material in the positive electrode sheet, thus contributing to a higher energy density in the battery.

[0024] A fourth aspect of this application provides a battery pack that includes the secondary battery of this application.

[0025] The fifth aspect of this application provides an electrical device that includes at least one of the secondary batteries or battery packs of this application.

[0026] The battery pack and electrical device of this application include the secondary battery described in this application, and therefore have at least the same or similar technical effects as the secondary battery. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope (SEM) image of a composite cathode material provided in one embodiment of this application.

[0028] Figure 2a This is a SEM image of the cross-section of the composite cathode material provided in Example 3.

[0029] Figure 2b This is a SEM image of the cross-section of the composite cathode material provided in Comparative Example 1.

[0030] Figure 3 This is a schematic diagram of one embodiment of a secondary battery.

[0031] Figure 4 yes Figure 3 The exploded diagram.

[0032] Figure 5 This is a schematic diagram of one embodiment of the battery module.

[0033] Figure 6 This is a schematic diagram of one embodiment of the battery pack.

[0034] Figure 7 yes Figure 6 The exploded diagram.

[0035] Figure 8 This is a schematic diagram of one embodiment of a device that uses a secondary battery as a power source. Detailed Implementation

[0036] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with specific embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of this application.

[0037] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0038] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or several" means two or more.

[0039] In this description, unless otherwise stated, the term "or" is inclusive. That is, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0040] The foregoing description of this invention is not intended to describe every disclosed embodiment or implementation. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0041] To meet the high energy density requirements of rechargeable batteries, lithium replenishment technology can be used to increase the active lithium-ion content and compensate for the loss of active lithium during the initial charge and discharge process. A theoretically feasible cathode lithium replenishment technology involves introducing lithium-rich metal oxides as cathode lithium replenishment materials to prepare a lithium-rich cathode. During battery formation or initial cycling, the cathode lithium replenishment material releases lithium to compensate for the irreversible active lithium loss caused by the formation of the SEI film at the anode.

[0042] However, existing cathode lithium supplementation materials often incorporate excess lithium sources during synthesis to increase their lithium content. This excess lithium source manifests as free lithium compounds such as Li₂O, LiOH, and Li₂CO₃ on the surface of the cathode lithium supplementation material. The presence of these free lithium compounds reduces the stability of the lithium-rich material, decreases the lithium supplementation effect, and also lowers the battery's energy density. Furthermore, the presence of free lithium compounds leads to a generally high pH value (pH > 12) in the lithium supplementation material. During cathode slurry preparation, lithium supplementation materials with a high pH value react with binders (such as polyvinylidene fluoride PVDF), causing the slurry to gel and form a jelly-like consistency. This not only makes the processing of the cathode slurry and cathode film difficult but can also affect the battery's capacity performance and cycle life.

[0043] The inventors further discovered that using carbon coating or atomic layer deposition of inert coating layers (such as Al2O3 layers) can effectively isolate the battery from the external environment. However, the surface coating process is complex, especially the introduction of electrochemically inert coating layers, which hinders the extraction of lithium ions from the internal lithium replenishment material, resulting in limited improvement in battery cycle life and a reduction in battery energy density.

[0044] Through in-depth research, the inventors have provided a scheme to improve the stability and lithium replenishment effect of cathode lithium replenishment materials by utilizing an electrochemically active coating layer. To maximize the improvement effect on cathode lithium replenishment materials, this invention provides a scheme to in-situ coat the surface of the cathode lithium replenishment material with a cathode active material layer. Based on this, the first aspect of this application provides a method for preparing a composite cathode material, comprising the following steps (1) to (4).

[0045] (1) Provide core materials. Core materials include lithium-rich metal oxides, the surface of which contains free lithium compounds.

[0046] (2) Provide precursors for positive electrode active materials.

[0047] (3) Attach the positive electrode active material precursor to at least a portion of the surface of the core material.

[0048] (4) React the positive electrode active material precursor with a free lithium compound to form a positive electrode active material on at least a portion of the surface of a lithium-rich metal oxide to obtain a composite positive electrode material.

[0049] Lithium-rich metal oxides can be placed on the positive electrode as a lithium replenishment material and can provide additional active lithium during the first charge or initial charging of the battery. Lithium-rich metal oxides can also be used to compensate for the irreversible loss of active lithium in the negative electrode caused by the formation of the SEI film.

[0050] The lithium-rich metal oxide can be selected from lithium-rich metal oxides known in the art that can be used for cathode lithium replenishment. During the synthesis of the lithium-rich metal oxide, an excess lithium source is added, and the residual lithium exists on the surface of the lithium-rich metal oxide as free lithium compounds, depending on the degree of reaction with external environmental substances such as CO2 and H2O. Examples of free lithium compounds may include one or more of Li2O, LiOH, and Li2CO3. In some embodiments, the main types of free lithium compounds on the outer layer of the lithium-rich metal oxide are LiOH and Li2CO3, while the main type of free lithium compounds on the inner layer is Li2O.

[0051] Positive electrode active materials refer to the materials in the positive electrode sheet (the electrode sheet with a higher potential in the battery) that participate in the insertion and extraction of active ions during the charging and discharging process of the battery.

[0052] In the method for preparing composite cathode materials provided in this application, free lithium compounds on the surface of lithium-rich metal oxides are cleverly used as lithium sources, and reacted in situ with cathode active material precursors to generate cathode active materials, thereby obtaining composite cathode materials in situ coated with lithium-rich metal oxides.

[0053] The lithium ions released from the lithium-rich metal oxide core during the first charge can compensate for the active lithium consumption during the formation of the SEI film at the negative electrode, improving the battery's initial charge / discharge capacity, initial coulombic efficiency, and cycle life. The positive electrode active material coating the lithium-rich metal oxide acts as a barrier against the external environment, improving the stability of the lithium-rich metal oxide during storage and use, and ensuring its purity and effective lithium replenishment performance. Simultaneously, the positive electrode active material coating layer is a good lithium-ion conductor, thus contributing to improved lithium replenishment efficiency. Furthermore, using a positive electrode active material to coat the lithium-rich metal oxide avoids the introduction of additional inactive materials, thereby enabling the battery to achieve higher energy density.

[0054] Specifically, compared to directly coating the positive electrode active material onto the surface of the core material, the in-situ reaction of the positive electrode active material precursor on the core material surface can form a denser and more uniform positive electrode active material coating layer. Furthermore, the in-situ generated positive electrode active material coating layer has a tighter bond with the core. Therefore, the stability of the composite positive electrode material is further improved, while also exhibiting further enhanced lithium-ion migration performance, thus contributing to higher initial charge-discharge capacity and cycle life. The tight bond between the positive electrode active material coating layer and the core also reduces the risk of coating layer detachment, thereby protecting lithium-rich metal oxides during long-term storage or use, further improving battery cycle life.

[0055] In particular, the in-situ generation of positive electrode active material precursors consumes free lithium compounds on the surface of lithium-rich metal oxides, thereby reducing the pH value. This avoids the slurry gelation problem caused by the strong alkalinity of lithium-rich metal oxides and improves the processing performance of positive electrode slurry and positive electrode film.

[0056] In some embodiments, in step (1), the mass percentage of free lithium compound in the core material is 0.5 wt% to 15 wt%, optionally 1 wt% to 10 wt%, and also optionally 2 wt% to 8 wt%, 3 wt% to 7 wt%, or 4 wt% to 6 wt%. The mass percentage of free lithium compound in the core material is determined by titration. The reagent solution used for titration is, for example, a standard hydrochloric acid solution. An exemplary test method is as follows: 30 g of core material is added to 100 mL of deionized water and stirred at 200 rpm for 30 min to obtain the sample to be tested; the free lithium compound in the sample to be tested is titrated with a standard hydrochloric acid solution, using a composite pH electrode as the indicator electrode, and the titration endpoint is determined by the abrupt change in potential; then the mass percentage of free lithium compound in the core material is calculated.

[0057] It is understandable that when the core material comes into contact with water, the free lithium compound Li₂O within it readily reacts with water to form LiOH. Therefore, the mass percentage of free lithium compound in the core material obtained by titration is calculated using LiOH as the free lithium compound Li₂O.

[0058] The core material contains an appropriate amount of free lithium compounds, which can be fully consumed by the cathode active material precursor, and this also helps to form a uniform cathode active material coating layer on the core surface. Therefore, the stability of the lithium-rich metal oxide is further improved, while its alkalinity is reduced, thus better achieving the lithium replenishment effect. Therefore, composite cathode materials prepared using core materials containing an appropriate amount of free lithium compounds can further improve the battery's initial charge-discharge capacity and cycle life. If necessary, the free lithium compound content in the core material can be adjusted within the required range by adjusting the amount of lithium source added during the preparation of the lithium-rich metal oxide.

[0059] In some embodiments, the water content of the core material is ≤500 ppm, optionally ≤450 ppm, ≤300 ppm, ≤200 ppm, or ≤100 ppm. Free lithium compounds on the surface of the core material readily adsorb moisture from the environment. Lower water content in the core material reduces the phase transition of the lithium-rich metal oxide, thus maintaining a higher lithium replenishment capacity. Simultaneously, reduced water content improves the reaction process between free lithium compounds and the cathode material precursor, facilitating the formation of a high-purity cathode active material and a uniform coating of the lithium-rich metal oxide. This further improves the stability of the lithium-rich metal oxide and increases the capacity of the composite cathode material. Therefore, the secondary battery achieves higher overall performance.

[0060] In this application, the water content of the core material has a meaning known in the art and can be determined using methods known in the art. For example, using a coulometric moisture analyzer of model 831, 10g of the core material is heated at 170°C in a fully automatic Karl Fischer sample heating injector of model 874, while simultaneously using a dry gas flow rate of 40mL / min to purge into a titration cup to titrate the water content for 400s.

[0061] In some implementations, the volume average particle size D of the core material v The particle size of the core material ranges from 1 μm to 10 μm, and optionally from 2 μm to 8 μm, 2 μm to 7 μm, 3 μm to 6 μm, 4 μm to 6 μm, or 4 μm to 5 μm. The smaller the particle size of the core material, the higher its specific surface area, resulting in stronger activity and a larger contact area with the positive electrode active material precursor. Therefore, the reaction between the free lithium compound and the positive electrode active material precursor is more complete. This leads to a higher D... vWithin an appropriate range, 50 can also reduce the self-agglomeration of the core material, further improve the uniformity of the coating of lithium-rich metal oxides on the positive electrode active material, and enable the composite positive electrode material to achieve higher capacity utilization. Therefore, using D v Composite cathode materials made from 50 suitable core materials can further improve the initial charge-discharge capacity and cycle life of batteries.

[0062] In some embodiments, the volume average particle size D of the positive electrode active material precursor is... v 50 has a thickness of 0.05μm to 3μm, and can be selected as 0.05μm to 2μm, 0.05μm to 1.5μm, 0.1μm to 1.5μm, 0.1μm to 1.2μm, 0.2μm to 1.2μm, or 0.2μm to 1μm. The D of the positive electrode active material precursor... v Within a suitable range, 50% of the positive electrode active material precursor and the core material have a larger contact area, and the positive electrode active material precursor itself is less prone to agglomeration. Therefore, using this positive electrode active material precursor can form a uniform positive electrode active material coating layer on the core surface, improving the stability and lithium replenishment performance of the core lithium replenishment material, thereby improving the battery's initial charge-discharge capacity and cycle life.

[0063] In this application, the volume average particle size D of the positive electrode active material precursor and the core material is... v 50 has a meaning known in the art and can be determined using methods known in the art. For example, it can be determined using a laser particle size analyzer (e.g., Malvern Mastersizer 2000E) according to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. Wherein, D v 50 indicates the particle size corresponding to a cumulative volume distribution percentage of 50%.

[0064] In some embodiments, the specific capacity of the core material is ≥300 mAh / g, optionally ≥320 mAh / g, ≥350 mAh / g, ≥390 mAh / g, or ≥400 mAh / g. The specific capacity of the core material is the ratio of the electrical capacity that the core material can release to its mass. A higher specific capacity of the core material means that the composite cathode material prepared from it can provide more active lithium for the formation of the SEI film in the anode, increasing the amount of active lithium and thus improving the overall performance of the battery, such as improving the initial charge-discharge capacity, initial coulombic efficiency, and cycle performance.

[0065] In some implementations, the lithium-rich metal oxide may be selected from Li2M 1 O2, Li2M 2 O3, Li3M 3 O4, Li5M 4 O4, Li6M5 One or more of O4. M 1 M 2 M 3 M 4 M 5 These represent metallic elements. Furthermore, in lithium-rich metal oxides, the valence state of each metallic element except Li is lower than its highest oxidation state.

[0066] In Li2M 1 In O2, M 1 It may include one or more of Ni, Co, Fe, Mn, Zn, Mg, Ca, and Cu. Optionally, M 1 Includes one or more of Ni, Co, Mn, and Cu. Optionally, M 1 This includes one or more of Ni, Cu, and Mn. As an example, Li₂M 1 O2 may include Li2NiO2, Li2MnO2, Li2CuO2, Li2Ni a Cu b M 1-a-b O2, Li2Co d Mn 1-d One or more of O2. Optionally, Li2M 1 O2 includes Li2NiO2, Li2CuO2, and Li2Ni a Cu b M 1-a-b One or more of O2. Optionally, Li2M 1 O2 includes Li2Ni a Cu b M 1-a-b O2. When present, 0 < a < 1, 0 < b < 1, 0.9 < a ​​+ b ≤ 1, and M is selected from one or more of Zn, Sn, Mg, Fe, and Mn. Optionally, 0.1 ≤ a ≤ 0.9, 0.2 ≤ a ≤ 0.8, 0.4 ≤ a ≤ 0.8, 0.4 ≤ a ≤ 0.6, or 0.5 ≤ a ≤ 0.7. Optionally, 0.1 ≤ b ≤ 0.9, 0.2 ≤ b ≤ 0.8, 0.2 ≤ b ≤ 0.6, 0.2 ≤ b ≤ 0.5, or 0.3 ≤ b ≤ 0.5. When present, 0 < d < 1. Optionally, 0.5 ≤ d ≤ 0.8.

[0067] In Li2M 2 In O3, M 2 It may include one or more of Mn, Sn, Mo, Ru, and Ir. Optionally, M 2 It includes one or more of Mn, Mo, and Sn. As an example, Li₂M 2 O3 may include one or more of Li2MnO3 and Li2MoO3.

[0068] In Li3M 3 In O4, M 3 It may include one or more of V, Nb, Cr, and Mo. Optionally, M 3 It includes one or more of V, Nb, and Mo. As an example, Li3M 3 O4 may include one or more of Li3VO4, Li3NbO4, and Li3MoO4. Optionally, Li3M 3 O4 includes one or more of Li3VO4 and Li3NbO4.

[0069] In Li5M 4 In O4, M 4 It may include one or more of Fe, Cr, V, and Mo. Optionally, M 4 This includes one or more of Fe, Cr, and V. As an example, Li5M 4 O4 may include one or more of Li5FeO4, Li5CrO4, and Li5VO4. Optionally, Li5M 4 O4 includes Li5FeO4.

[0070] In Li6M 5 In O4, M 5 It may include one or more of Co, V, Cr, and Mo. Optionally, M 5 This includes one or more of Co, V, and Cr. As an example, Li6M... 5 O4 may include one or more of Li6CoO4, Li6VO4, and Li6CrO4. Optionally, Li6M 5 O4 includes Li6CoO4.

[0071] In some embodiments, the lithium-rich metal oxide may include Li2M 1 O2, Li2M 2 O3, Li5M 4 O4, Li6M 5 One or more of O4. Optionally, lithium-rich metal oxides may include Li2M 1 O2, Li5M 4 O4, Li6M 5 One or more of O4. When present, M 1 M 2 M 4 M 5 As defined in this article.

[0072] Lithium-rich metal oxides have appropriate chemical compositions, which can combine high specific capacity with good stability.

[0073] In some embodiments, lithium-rich metal oxides may include Li₂NiO₂, Li₂CuO₂, Li₂Ni a Cu b M 1-a-b One or more of O2, Li2MnO2, Li3VO4, Li3NbO4, Li5FeO4, and Li6CoO4. Optionally, lithium-rich metal oxides include Li2NiO2, Li2CuO2, and Li2Ni a Cu b M 1-a-b One or more of O2, Li5FeO4, and Li6CoO4. In some embodiments, the lithium-rich metal oxide includes one or more of Li5FeO4 and Li6CoO4. Wherein, a, b, and M are as defined herein.

[0074] In step (2), the positive electrode active material precursor can be a substance known in the art that can react with free lithium compounds to form a positive electrode active material. In some embodiments, the positive electrode active material precursor may be selected from one or more of transition metal oxides, transition metal hydroxides, transition metal carbonates, and transition metal phosphates. In some embodiments, the positive electrode active material precursor may be selected from one or more of transition metal hydroxides, transition metal carbonates, and transition metal phosphates. Examples of transition metals in the positive electrode active material precursor may include one or more of Mn, Fe, Ni, Co, Cr, Ti, Zn, V, Zr, and Ce. In some embodiments, the positive electrode active material precursor may also contain metal elements other than transition metals, such as one or more of Al, Mg, Ca, Ge, and Sn.

[0075] It will be readily understood by those skilled in the art that the positive electrode active materials formed by transition metal oxides, transition metal hydroxides, and transition metal carbonates are the corresponding lithium transition metal oxides. The positive electrode active materials formed by transition metal phosphates are the corresponding lithium transition metal phosphates.

[0076] In some embodiments, the positive electrode active material precursor may be selected from transition metal hydroxides. Examples of transition metal hydroxides may include Ni. x1 Co y1 Mn z1 (OH)2, Ni x2 Co y2 Al z2 One or more of (OH)₂. Accordingly, the formed positive electrode active material may include Li₂. s1 Ni x1 Co y1 Mn z1 O2, Li s2 Nix2 Co y2 Al z2 One or more of O2. x1 + y1 + z1 = 1. That is, 0 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 1, 0 ≤ z1 ≤ 1, and x1 + y1 + z1 = 1. Optionally, 0 < x1 < 1, 0 < y1 < 1, 0 < z1 < 1. Further optionally, 0.3 ≤ x1 ≤ 0.95, 0.5 ≤ x1 ≤ 0.9, or 0.6 ≤ x1 ≤ 0.8. 0.7 ≤ s1 ≤ 1.2. Optionally, 0.8 ≤ s1 ≤ 1.2, 0.9 ≤ s1 ≤ 1.15, 1.0 ≤ s1 ≤ 1.2, or 1.0 ≤ s1 ≤ 1.1. x2 + y2 + z2 = 1. That is, 0 ≤ x2 ≤ 1, 0 ≤ y2 ≤ 1, 0 ≤ z2 < 1, and x2 + y2 + z2 = 1. Optionally, 0 < x² < 1, 0 < y² < 1, 0 < z² < 1. Further optionally, 0.3 ≤ x² ≤ 0.95, 0.5 ≤ x² ≤ 0.9, or 0.6 ≤ x² ≤ 0.85. 0.7 ≤ s² ≤ 1.2. Optionally, 0.8 ≤ s² ≤ 1.2, 0.9 ≤ s² ≤ 1.15, 1.0 ≤ s² ≤ 1.2, or 1.0 ≤ s² ≤ 1.1.

[0077] As an example, transition metal hydroxides may be selected from nickel hydroxide Ni(OH)2, cobalt hydroxide Co(OH)2, manganese hydroxide Mn(OH)2, and nickel-cobalt composite hydroxide Ni. x1 Co y1 (OH)2 (0 < x1 < 1, 0 < y1 < 1, and x1 + y1 = 1), Ni cobalt manganese composite hydroxide Ni x1 Co y1 Mn z1 (OH)2 (0 < x1 < 1, 0 < y1 < 1, 0 < z1 < 1, and x1 + y1 + z1 = 1), Ni cobalt aluminum composite hydroxide Ni x2 Co y2 Al z2 (OH)₂ (0 < x² < 1, 0 < y² < 1, 0 < z² < 1, and x² + y² + z² = 1) is one or more of these. In some embodiments, the transition metal hydroxide is selected from nickel-cobalt-manganese composite hydroxide Ni. x1 Co y1 Mn z1 (OH)2, Ni cobalt aluminum complex hydroxide Ni x2 Co y2 Al z2 One or more of (OH)2. The sintering temperature of the positive electrode active material generated by the reaction of appropriate transition metal hydroxides with free lithium compounds is relatively low, which can reduce the sintering time, and in particular, reduce the volatilization of free lithium compounds during the sintering process, thus helping to improve the purity of the positive electrode active material layer.

[0078] In some embodiments, the positive electrode active material precursor may be selected from a transition metal carbonate. Examples of transition metal carbonates may include Ni. x3 Co y3 Mn z3 CO3, Ni x4 Co y4 Al z4 One or more of CO3. Accordingly, the resulting positive electrode active material may include Li. s3 Ni x3 Co y3 Mn z3 O2, Li s4 Ni x4 Co y4 Al z4 One or more of O2. x³ + y³ + z³ = 3. That is, 0 ≤ x³ ≤ 1, 0 ≤ y³ ≤ 1, 0 ≤ z³ ≤ 1, and x³ + y³ + z³ = 1. Optionally, 0 < x³ < 1, 0 < y³ < 1, 0 < z³ < 1. Further, optionally, 0.3 ≤ x³ ≤ 0.95, 0.5 ≤ x³ ≤ 0.9, or 0.6 ≤ x³ ≤ 0.8. 0.7 ≤ s³ ≤ 1.2. Optionally, 0.8 ≤ s³ ≤ 1.2, 0.9 ≤ s³ ≤ 1.15, 1.0 ≤ s³ ≤ 1.2, or 1.0 ≤ s³ ≤ 1.1. x⁴ + y⁴ + z⁴ = 1. That is, 0 ≤ x⁴ ≤ 1, 0 ≤ y⁴ ≤ 1, 0 ≤ z⁴ < 1, and x⁴ + y⁴ + z⁴ = 1. Optionally, 0 < x⁴ < 1, 0 < y⁴ < 1, 0 < z⁴ < 1. Further optionally, 0.3 ≤ x⁴ ≤ 0.95, 0.5 ≤ x⁴ ≤ 0.9, or 0.6 ≤ x⁴ ≤ 0.85. 0.7 ≤ s⁴ ≤ 1.2. Optionally, 0.8 ≤ s⁴ ≤ 1.2, 0.9 ≤ s⁴ ≤ 1.15, 1.0 ≤ s⁴ ≤ 1.2, or 1.0 ≤ s⁴ ≤ 1.1.

[0079] As an example, transition metal carbonates can be selected from nickel carbonate (NiCO3), cobalt carbonate (CoCO3), manganese carbonate (MnCO3), and nickel-cobalt composite carbonate (Ni). x3 Co y3 CO3 (0 < x3 < 1, 0 < y3 < 1, and x3 + y3 = 1), Ni cobalt manganese composite carbonate Ni x3 Co y3 Mn z3 CO3 (0 < x3 < 1, 0 < y3 < 1, 0 < z3 < 1, and x3 + y3 + z3 = 1), Ni cobalt aluminum composite carbonate Ni x4 Co y4 Al z4 CO3 is selected from one or more of the following: (0 < x4 < 1, 0 < y4 < 1, 0 < z4 < 1, and x4 + y4 + z4 = 1). Optionally, the transition metal carbonate is selected from the nickel-cobalt-manganese composite carbonate Ni.x3 Co y3 Mn z3 CO3, nickel-cobalt-aluminum complex carbonate Ni x4 Co y4 Al z4 One or more of CO3.

[0080] In some embodiments, the positive electrode active material precursor may be selected from a transition metal oxide. Examples of transition metal oxides may include Ni. x5 Co y5 Mn z5 O, Ni x6 Co y6 Al z6 One or more of O. Accordingly, the resulting positive electrode active material may include Li. s5 Ni x5 Co y5 Mn z5 O2, Li s6 Ni x6 Co y6 Al z6 One or more of O2. x5 + y5 + z5 = 1. That is, 0 ≤ x5 ≤ 1, 0 ≤ y5 ≤ 1, 0 ≤ z5 ≤ 1, and x5 + y5 + z5 = 1. Optionally, 0 < x5 < 1, 0 < y5 < 1, 0 < z5 < 1. Further optionally, 0.5 ≤ x5 ≤ 0.95, 0.5 ≤ x5 ≤ 0.9, or 0.6 ≤ x5 ≤ 0.8. 0.7 ≤ s5 ≤ 1.2. Optionally, 0.8 ≤ s5 ≤ 1.2, 0.9 ≤ s5 ≤ 1.15, 1.0 ≤ s5 ≤ 1.2, or 1.0 ≤ s5 ≤ 1.1. x6 + y6 + z6 = 1. That is, 0 ≤ x6 ≤ 1, 0 ≤ y6 ≤ 1, 0 ≤ z6 < 1, and x6 + y6 + z6 = 1. Optionally, 0 < x6 < 1, 0 < y6 < 1, 0 < z6 < 1. Further optionally, 0.3 ≤ x6 ≤ 0.95, 0.5 ≤ x6 ≤ 0.9, or 0.6 ≤ x6 ≤ 0.85. 0.7 ≤ s6 ≤ 1.2. Optionally, 0.8 ≤ s6 ≤ 1.2, 0.9 ≤ s6 ≤ 1.15, 1.0 ≤ s6 ≤ 1.2, or 1.0 ≤ s6 ≤ 1.1.

[0081] As an example, the transition metal oxide can be selected from nickel oxide (NiO), cobalt oxide (CoO), manganese oxide (MnO), and nickel-cobalt composite oxide (Ni). x5 Co y5 O (0 < x5 < 1, 0 < y5 < 1, and x5 + y5 + z5 = 1), Ni cobalt manganese composite oxide x5 Co y5 Mn z5O(0 < x5 < 1, 0 < y5 < 1, 0 < z5 < 1, and x5 + y5 + z5 = 1), Ni cobalt aluminum composite oxide x6 Co y6 Al z6 One or more of the following are selected: O(0 < x6 < 1, 0 < y6 < 1, 0 < z6 < 1, and x6 + y6 + z6 = 1). Optionally, the transition metal oxide is selected from the nickel-cobalt-manganese composite oxide Ni. x5 Co y5 Mn z5 O, Ni cobalt aluminum composite oxide x6 Co y6 Al z6 One or more of O.

[0082] In some embodiments, the positive electrode active material precursor may be selected from a transition metal phosphate. Examples of transition metal phosphates may include MPO4, wherein M is selected from one or more of Fe, Ni, Co, and Mn. Accordingly, the formed positive electrode active material may include Li s7 MPO4. 0.7≤s7≤1.2. Optionally, 0.8≤s7≤1.2, 0.9≤s7≤1.15, 1.0≤s7≤1.2, or 1.0≤s7≤1.1. Appropriate transition metal phosphates react with free lithium compounds to form positive electrode active materials at lower sintering temperatures, thereby reducing sintering time and, in particular, reducing the volatilization of free lithium compounds during sintering, which helps improve the purity of the positive electrode active material layer. In some embodiments, the transition metal phosphate may be selected from FePO4, Fe... u M' 1-u One or more of PO4. 0 < u < 1, optionally 0.1 ≤ u ≤ 0.9, or 0.2 ≤ u ≤ 0.8. M' can be selected from one or more of Mn, Ni, Co, Cr, Ti, V, Ce, and further selected from one or more of Ni, Co, and Mn.

[0083] In some embodiments, the positive electrode active material precursor is selected from transition metal oxides, transition metal hydroxides, transition metal carbonates, CoPO4, NiPO4, MnPO4, FePO4, Fe u M' 1-u One or more of PO4, and lithium-rich metal oxides selected from Li2NiO2, Li2CuO2, and Li2Ni a Cu b M 1-a-bOne or more of O2, Li3VO4, Li3NbO4, Li5FeO4, and Li6CoO4. When present, u, M', a, b, and M are as defined herein. Composite cathode materials obtained by using suitable cathode active material precursors and core materials contribute to achieving higher initial charge / discharge capacity and longer cycle life in batteries. Fe u M' 1- u Specific examples of PO4 include Fe u Mn 1-u PO4.

[0084] Optionally, the lithium-rich metal oxide may be selected from Li2NiO2, Li2CuO2, or Li2Ni a Cu b M 1-a-b One or more of O2, Li5FeO4, and Li6CoO4. Optionally, the lithium-rich metal oxide is selected from one or more of Li5FeO4 and Li6CoO4. Further optionally, the lithium-rich metal oxide is selected from one or more of Li5FeO4 and Li6CoO4.

[0085] Optionally, the positive electrode active material precursor is selected from one or more of transition metal oxides, transition metal hydroxides, and transition metal carbonates. The transition metal oxides, transition metal hydroxides, and transition metal carbonates can be those described herein. In some embodiments, the positive electrode active material precursor can be selected from nickel-cobalt-manganese composite hydroxide Ni... x1 Co y1 Mn z1 (OH)2, Ni cobalt aluminum complex hydroxide Ni x2 Co y2 Al z2 One or more of (OH)2. When present, x1, y1, z1, x2, y2, and z2 are as defined herein. In these embodiments, optionally, the volume average particle size D of the positive electrode active material precursor is... v The thickness of 50 is 0.5μm to 1.2μm, and can also be selected as 0.5μm to 1μm, or 0.6μm to 1μm. The D of the positive electrode active material precursor... v Within an appropriate range, 50 can further improve the battery's initial charge / discharge capacity and cycle life.

[0086] Optionally, the positive electrode active material precursor is selected from one or more transition metal phosphates. Transition metal phosphates can be those described herein. In some embodiments, the positive electrode active material precursor is selected from CoPO4, NiPO4, MnPO4, FePO4, Fe... u M' 1-uOne or more of PO4. Where present, u and M' are as defined herein. In these embodiments, optionally, the D of the positive electrode active material precursor... v The micrometer size (D50) is 0.1 μm to 1 μm, and optionally 0.2 μm to 0.8 μm, 0.3 μm to 0.7 μm, or 0.4 μm to 0.6 μm. The D50 of the positive electrode active material precursor... v Within an appropriate range, 50 can further improve the battery's initial charge / discharge capacity and cycle life.

[0087] In some embodiments, the mass ratio of the core material to the positive electrode active material precursor is 30:1 to 2:1, optionally 30:1 to 5:1, 25:1 to 10:1, 25:1 to 15:1, 20:1 to 5:1, 20:1 to 10:1, or 20:1 to 15:1. Within an appropriate range, this mass ratio achieves both good coating and protection of the core by the positive electrode active material layer, and also ensures high purity of the positive electrode active material layer. Therefore, the composite positive electrode active material exhibits high stability and reversible capacity, thereby improving the initial charge-discharge capacity and cycle performance of batteries using it.

[0088] In step (3), any known means in the art can be used to attach the positive electrode active material precursor to at least a portion of the surface of the core material. As an example, a mechanical fusion machine can be used for mechanical fusion attachment. Mechanical fusion allows for rapid and efficient uniform mixing of the positive electrode active material precursor and the core material, resulting in better uniformity and consistency of the positive electrode active material precursor's surface attachment to the core material. The positive electrode active material precursor and the core material can form a uniform and robust attachment through chemical bonding and / or physical bonding (e.g., intermolecular forces).

[0089] Optionally, in the mechanical fusion process, high-speed fusion can be performed at a rotation speed of 200 rpm to 1000 rpm for 1 hour to 10 hours, allowing the positive electrode active material precursor to adhere to the surface of the core material. Optionally, the rotation speed is 300 rpm to 800 rpm. Optionally, the fusion time is 2 hours to 6 hours. Fusion can be performed at room temperature, such as 20°C to 30°C, or even 25°C.

[0090] In step (4), any known means in the art can be used to react the positive electrode active material precursor with the free lithium compound in the core material to form the positive electrode active material, thereby obtaining the composite positive electrode material. In some embodiments, the positive electrode active material precursor can be reacted with the free lithium compound at 600℃~1000℃ for 2h~12h under a protective gas atmosphere to form the positive electrode active material. In some embodiments, the heat treatment temperature can be selected as 600℃~800℃, 600℃~700℃, or 650℃~750℃. The heat treatment time can be selected as 2h~10h, 2h~8h, 4h~8h, or 4h~6h. Suitable sintering conditions help the positive electrode active material to uniformly and effectively coat the core lithium supplementation material, and can also improve the crystallinity of the positive electrode active material, thereby further improving the reversible capacity and cycle stability of the composite positive electrode material. The aforementioned protective gas can be selected from one or more of nitrogen, argon, and hydrogen / argon mixture.

[0091] Next, this application provides a composite cathode material. The composite cathode material includes a lithium-rich metal oxide and a cathode active material covering at least a portion of the surface of the lithium-rich metal oxide. The cathode active material is formed by an in-situ reaction of a cathode active material precursor with a free lithium compound on the surface of the lithium-rich metal oxide.

[0092] In the composite cathode material provided in this application, the lithium ions released from the lithium-rich metal oxide core during the first charge can compensate for the active lithium consumption during the formation of the SEI film on the negative electrode, thereby improving the battery's first charge-discharge capacity, first coulombic efficiency, and cycle life. The outer shell of the cathode active material coats the lithium-rich metal oxide, effectively isolating it from the external environment, improving its stability during storage and use, and ensuring its purity and effective lithium replenishment performance. Simultaneously, the cathode active material coating layer is a good lithium-ion conductor, providing excellent lithium-ion diffusion channels during battery charge-discharge, thus contributing to improved lithium replenishment efficiency. The composite cathode material improves the capacity utilization of the lithium-rich metal oxide, allowing it to release more active lithium. Excess active lithium is embedded in the negative electrode, placing the negative electrode active material in a certain lithium-intercalation state, which can mitigate volume changes in the negative electrode active material to some extent. Therefore, the risk of negative electrode active material cracking or powder shedding is reduced, while maintaining good electrolyte wettability and liquid retention. Furthermore, this portion of active lithium can be used to compensate for the loss of active lithium during battery cycling in the middle and later stages of the cycle. Therefore, the composite cathode material using this application can have a further extended cycle life.

[0093] Using positive electrode active materials to coat lithium-rich metal oxides can avoid the introduction of additional inactive materials, which helps to achieve higher energy density in the battery.

[0094] Specifically, the in-situ reaction of the cathode active material precursor on the surface of lithium-rich metal oxide can form a dense and uniform cathode active material coating layer. Furthermore, the in-situ formed cathode active material coating layer has a tighter bond with the lithium-rich metal oxide. Therefore, the stability of the composite cathode material is further improved, while also exhibiting further enhanced lithium-ion migration performance, thus contributing to higher initial charge-discharge capacity and cycle life. The tight bond between the cathode active material coating layer and the lithium-rich metal oxide also reduces the risk of coating detachment, thereby protecting the lithium-rich metal oxide during long-term storage or use, and further improving battery cycle life.

[0095] In particular, the in-situ generation of positive electrode active material precursors consumes free lithium compounds on the surface of lithium-rich metal oxides, thereby reducing the pH value. This avoids the slurry gelation problem caused by the strong alkalinity of lithium-rich metal oxides and improves the processing performance of positive electrode slurry and positive electrode film.

[0096] In some embodiments, the positive electrode active material in the composite cathode material is distributed as independent particles on the surface of the lithium-rich metal oxide. The morphology of the composite cathode material can be observed using a scanning electron microscope (e.g., SIGMA 300). Figure 1 This is an SEM image of a composite cathode material as an example. Figure 2a This is a SEM image of a cross-section of a composite cathode material as an example. The cross-section of the composite cathode material can be obtained using an ion polisher (e.g., an argon ion cross-section polisher, such as the IB-19500CP). As can be seen from the image, the composite cathode material consists of a core particle with a large number of cathode active material particles coated on its surface.

[0097] In this application, when the positive electrode active material is distributed in the form of independent particles on the surface of the lithium-rich metal oxide, the positive electrode active material on the surface of the composite positive electrode material can form an effective physical barrier, avoiding direct contact between the lithium-rich metal oxide and the electrolyte, reducing the occurrence of side reactions, and thus further improving the electrochemical stability of the lithium-rich metal oxide. The particulate positive electrode active material can also better exert its high-capacity characteristics. Therefore, batteries using this composite positive electrode material can achieve higher energy density and cycle performance.

[0098] In some embodiments, the coating rate of the positive electrode active material on the lithium-rich metal oxide surface is ≥60%. Further alternatively, it is ≥70%, ≥80%, ≥90%, ≥95%, or 100%. In this application, when the coating rate of the positive electrode active material on the lithium-rich metal oxide surface is within a large range, the sensitivity of the composite positive electrode material to the external environment (especially humidity) can be further reduced, effectively improving the gelation problem of the composite positive electrode material during the preparation of the positive electrode slurry, and improving the processability of the composite positive electrode material in battery applications.

[0099] Optionally, the core lithium-rich metal oxide and the outer shell positive electrode active material can be bonded together through chemical bonding and physical bonding (e.g., intermolecular forces). In some embodiments, in the composite positive electrode material, the positive electrode active material particles are tightly attached to the surface of the lithium-rich metal oxide through chemical bonding between the lithium-rich metal oxide and the positive electrode active material, thus resulting in high microstructural stability and electrochemical stability of the composite positive electrode material. Therefore, batteries using this composite positive electrode material can achieve good long-term cycle performance.

[0100] It is understood that composite cathode materials can be prepared using the methods described in this application and obtain corresponding beneficial effects.

[0101] This application also provides a secondary battery, which includes a positive electrode sheet, comprising any one or more composite positive electrode materials of this application. The secondary battery of this application can simultaneously achieve high initial charge-discharge capacity, high energy density, and long cycle life.

[0102] A secondary battery also includes a negative electrode and an electrolyte. During the charging and discharging process, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor of ions between the positive and negative electrodes.

[0103] [Positive electrode plate]

[0104] This application provides a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on the positive current collector. As an example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is laminated on either or both of the two opposite surfaces of the positive current collector.

[0105] The positive electrode film layer includes at least a first positive electrode material, which includes any one or more composite positive electrode materials of this application. In some embodiments, the first positive electrode material is any one or more composite positive electrode materials of this application.

[0106] In some embodiments, the positive electrode film layer further comprises a second positive electrode material. The second positive electrode material can be an active material known in the art that can be used as a positive electrode in a secondary battery. As an example, the second positive electrode material may include one or more of lithium transition metal oxides and polyanionic positive electrode materials. Optionally, the lithium transition metal oxide is selected from lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), layered lithium manganese oxide (such as LiMnO2), and lithium nickel cobalt manganese oxide (such as LiNiO2). α 1Co β1 Mn 1-α1-β1 O2, where 0 < α1 < 1, 0 < β1 < 1, lithium nickel cobalt aluminum oxide (such as LiNi) α2 Co β2 Al 1-α2-β2 O2, where 0 < α2 < 1, 0 < β2 < 1), spinel lithium manganese oxide (such as LiMn2O4), spinel lithium nickel manganese oxide (such as LiNi 0.5 Mn 1.5 O4) and one or more of their modified materials. Optionally, the polyanionic cathode material is selected from lithium iron phosphate (such as LiFePO4), lithium manganese phosphate (such as LiMnPO4), lithium cobalt phosphate (such as LiCoPO4), lithium nickel phosphate (such as LiNiPO4), and lithium manganese iron phosphate (such as LiFe) γ Mn 1-γ PO4 (where 0 < γ < 1) and one or more of their modified materials. A second positive electrode material is also included in the positive electrode film layer, which can increase the proportion of positive electrode active material in the positive electrode sheet, thus helping the battery to achieve a higher energy density. The aforementioned modified materials can be coating modifications and / or doping modifications.

[0107] In some embodiments, based on the total weight of the first and second positive electrode materials, the mass percentage of the first positive electrode material in the positive electrode film can be selected from 5% to 100%, and may also be 5% to 50%, 10% to 40%, 15% to 35%, 10% to 25%, or 20% to 30%, etc. Containing an appropriate amount of the first positive electrode material in the positive electrode film allows the battery to better balance higher energy density and cycle life.

[0108] The positive electrode film typically also includes an optional binder and an optional conductive agent. Generally, a first positive electrode material, along with an optional second positive electrode material, an optional conductive agent, and an optional binder, are dispersed in a solvent and stirred until homogeneous to form a positive electrode slurry. This slurry is then dried and cold-pressed to form the positive electrode film. The solvent can be N-methylpyrrolidone (NMP).

[0109] The binder can stably bond the positive electrode material and optionally the conductive agent to the positive electrode current collector. In some embodiments, the binder for the positive electrode film layer may be selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and modified polymers thereof.

[0110] Conductive agents can improve the electronic conductivity of the positive electrode film. In some embodiments, the conductive agent of the positive electrode film can be selected from one or more of superconducting carbon, carbon black (such as Super P, acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] The positive current collector can be made of a material with good conductivity and mechanical strength. As an example, aluminum foil can be used as the positive current collector.

[0112] [Negative electrode plate]

[0113] The negative electrode sheet of this application includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. As an example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is laminated on either or both of the two opposite surfaces of the negative current collector.

[0114] In the negative electrode sheet of this application, the negative electrode film layer typically comprises a negative electrode material and optionally a binder, optionally a conductive agent, and other optional additives. It is usually formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry coating is typically formed by dispersing the negative electrode material, optionally a conductive agent, optionally a binder, and optionally additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water.

[0115] In some embodiments, the negative electrode material may be selected from one or more of artificial graphite, natural graphite, silicon-based materials, and tin-based materials. Optionally, the negative electrode active material includes one or more of artificial graphite and natural graphite. Further optionally, the negative electrode active material includes artificial graphite.

[0116] In some embodiments, the conductive agent may include one or more of superconducting carbon, carbon black (e.g., Super P, acetylene black, Ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0117] In some embodiments, the adhesive may include one or more of styrene-butadiene rubber (SBR), waterborne acrylic resin, polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0118] In some embodiments, other optional additives include thickeners (e.g., sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, etc.

[0119] The negative electrode current collector can be made of a material with good conductivity and mechanical strength, serving both as a conductor and a current collector. In some embodiments, the negative electrode current collector can be made of copper foil.

[0120] [Electrolytes]

[0121] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be selected from electrolyte solutions. The electrolyte solution includes an electrolyte salt and a solvent.

[0122] In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0123] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0124] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature performance, etc.

[0125] [Isolation membrane]

[0126] The separator is disposed between the positive and negative electrode plates, serving as a barrier. The secondary battery of this application does not have particular limitations on the type of separator; any known porous separator used in secondary batteries can be selected. For example, the separator can be selected from one or more of the following: glass fiber film, non-woven fabric film, polyethylene film, polypropylene film, polyvinylidene fluoride film, and multilayer composite films containing one or more of these materials.

[0127] Positive electrode, negative electrode, and separator can be stacked or wound to form an electrode assembly, with the separator positioned between the positive and negative electrode to provide isolation. The electrode assembly is then placed in an outer package, filled with electrolyte, and sealed to obtain a secondary battery.

[0128] The outer packaging of a secondary battery is used to encapsulate the electrode assembly and electrolyte. In some embodiments, the outer packaging of the secondary battery can be a rigid shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0129] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. Figure 3 This is an example of a square-structured secondary battery 5.

[0130] In some embodiments, refer to Figure 4 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. Electrode assemblies 52 are encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assemblies 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be adjusted according to requirements.

[0131] In some embodiments, secondary batteries can be assembled into battery packs. Examples of battery packs include battery modules, battery packs, etc. A battery module can be assembled from multiple secondary batteries. The number of secondary batteries contained in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. A battery pack can be assembled from multiple secondary batteries or battery modules. The number of secondary batteries or battery modules contained in a battery pack can be adjusted according to the application and capacity of the battery pack.

[0132] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple secondary batteries 5 can be secured with fasteners. Optionally, battery module 4 may also include a housing with a receiving space to accommodate the multiple secondary batteries 5.

[0133] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0134] This application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack described in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0135] The electrical device can be equipped with a secondary battery, battery module, or battery pack according to its usage requirements.

[0136] Figure 8 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density in its secondary batteries, a battery pack or battery module can be used.

[0137] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0138] Example

[0139] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0140] Example 1

[0141] Preparation of lithium-ion secondary batteries:

[0142] Preparation of composite cathode materials

[0143] The core material is a lithium-rich metal oxide, Li₂Ni, whose surface contains free lithium compounds (mainly Li₂O, LiOH, and Li₂CO₃). 0.6 Cu 0.4 O2. The mass percentage of free lithium compounds in the core material is 1 wt%. The D of the core material... v 50 represents 5μm. The precursor for the positive electrode active material is FePO4 (iron phosphate, abbreviated as FP), D v 50 represents 0.5 μm. Mechanical fusion coating was performed using a mechanical fusion machine: the core material and the positive electrode active material precursor FP were added to the mechanical fusion machine at a mass ratio of 20:1 and fused at high speed at 400 rpm for 4 hours, allowing FP to adhere to the surface of the core material. Under a nitrogen atmosphere, sintering was carried out at 700℃ for 6 hours, allowing FP to react in situ with free lithium compounds to form the positive electrode active material lithium iron phosphate (LiFePO4) (abbreviated as LFP) on the surface of the lithium-rich metal oxide, thus obtaining the composite positive electrode material.

[0144] Preparation of positive electrode sheet

[0145] The composite positive electrode material prepared above, conductive carbon black (Super P), and binder PVDF were dispersed in NMP solvent at a mass ratio of 97:2:1 and thoroughly mixed to obtain a positive electrode slurry. The positive electrode slurry was coated onto two opposite surfaces of a positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained. The areal density of the positive electrode film was 18 mg / cm³. 2 The compacted density is 2.45 g / cm³. 3 .

[0146] Preparation of negative electrode sheet

[0147] Artificial graphite (negative electrode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) were dispersed in deionized water at a mass ratio of 96:1.5:1.5:1.0. After thorough mixing, a negative electrode slurry was obtained. This slurry was then coated onto the two opposite surfaces of a copper foil current collector. After drying and cold pressing, a negative electrode sheet was obtained. The areal density of the negative electrode film was 8.0 mg / cm³. 2 The compacted density is 1.65 g / cm³. 3 .

[0148] Preparation of electrolyte

[0149] Ethyl carbonate (EC) and ethyl methyl carbonate (EMC) were mixed evenly at a mass ratio of 30:70 to obtain an organic solvent; lithium salt LiPF6 was then dissolved in the organic solvent and mixed evenly to obtain an electrolyte, wherein the concentration of LiPF6 was 1 mol / L.

[0150] Preparation of secondary batteries

[0151] The positive electrode sheet, the porous polyethylene (PE) separator, and the negative electrode sheet are stacked in sequence and then wound to obtain an electrode assembly. The electrode assembly is then placed in an outer package, injected with electrolyte, and sealed to obtain a secondary battery.

[0152] Examples 2-24

[0153] The preparation of the secondary battery is similar to that in Example 1, except that the relevant parameters in the preparation of the composite cathode material are adjusted, as detailed in Table 1.

[0154] Comparative Example 1

[0155] Preparation of composite cathode materials

[0156] The core material is the same as in Example 3. The positive electrode active material is LiFePO4 (lithium iron phosphate, abbreviated as LFP), D v 50 represents 0.5 μm. Mechanical fusion coating was performed using a mechanical fusion machine: the core material and the positive electrode active material LFP were added to the mechanical fusion machine at a mass ratio of 20:1 and fused at a high speed of 400 rpm for 4 hours, so that LFP was coated on the surface of the core material to obtain a composite positive electrode material.

[0157] The remaining preparation process of the secondary battery is the same as in Example 1.

[0158] Figure 2a These are cross-sectional SEM images of the composite cathode material from Example 3. Figure 2bThis is a cross-sectional SEM image of the composite cathode material in Comparative Example 1. The larger particles in the image are lithium-rich metal oxides, specifically Li₂Ni₃. 0.6 Cu 0.4 O2, the smaller particles on the outer shell are the positive electrode active material LFP. As can be seen from the figure, in Example 3, the composite positive electrode material obtained using the in-situ coating method according to this application contains Li2Ni... 0.6 Cu 0.4 The LFP coating layer on the surface of O2 particles is more uniform and dense, and Li2Ni 0.6 Cu 0.4 The O2 particles are more tightly bonded to the LFP coating.

[0159] Examples 25-29

[0160] The preparation of the secondary battery is similar to that in Example 1, except that the positive electrode active material precursor is Ni. 0.8 Co 0.1 Mn 0.1 (OH)2 (abbreviated as NCMOH) reacts with free lithium compounds in the core material to form the positive electrode active material LiNi. 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as LNCMO); the areal density of the positive electrode film is 19.5 mg / cm³. 2 The compacted density is 3.4 g / cm³. 3 The areal density of the negative electrode film is 10.8 mg / cm³. 2 The compacted density is 1.65 g / cm³. 3 For other differences, please refer to Table 1.

[0161] Comparative Example 2

[0162] The preparation of the secondary battery is similar to that of Comparative Example 1, except that the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2 (LNCMO), D v 50 is 0.8μm; for the other differences, please refer to Table 1.

[0163] Performance testing of secondary batteries:

[0164] At 25℃, the secondary battery is charged at a constant current rate of 1C to the upper limit cutoff voltage, and then charged at a constant voltage until the current reaches 0.05C. The charging capacity at this point is recorded as the first charge capacity. Next, it is discharged at a constant current rate of 1C to the lower limit cutoff voltage, and then allowed to stand for 5 minutes. This completes one charge-discharge cycle, and the discharge capacity at this point is recorded as the first discharge capacity. The battery is then subjected to charge-discharge tests using the above method, and the discharge capacity of each cycle is recorded until the battery's capacity retention rate decreases to 80%. The number of cycles at this point is the cycle life.

[0165] Initial discharge capacity (mAh / g) = First discharge capacity / Mass of composite cathode material in the battery

[0166] During testing, when the positive electrode active material was LFP, the charge / discharge voltage range of the secondary battery was 2.5V to 3.65V; when the positive electrode active material was LNCMO, the charge / discharge voltage range of the secondary battery was 2.8V to 4.25V.

[0167] Table 1

[0168]

[0169] Note: Unless otherwise specified, in Table 1, the mass percentage refers to the mass percentage of free lithium compounds in the core material; the mass ratio is the mass ratio of the core material to the coating raw material; and the coating raw material is the material used to coat the core material in the mechanical fusion coating step. In Examples 1-30, the coating raw material is the positive electrode active material precursor; in Comparative Example 1, the coating raw material is the positive electrode active material LFP; and in Comparative Example 2, the coating raw material is the positive electrode active material LNCMO.

[0170] This application utilizes free lithium compounds on the surface of lithium-rich metal oxides as a lithium source, which react in situ with a precursor of the positive electrode active material to generate the positive electrode active material, thereby obtaining a composite positive electrode material in situ coated with lithium-rich metal oxides. As shown in Table 1, compared to the composite positive electrode material obtained by directly coating the core material with the positive electrode active material in the comparative example, the composite positive electrode material of this application enables the secondary battery to achieve higher initial discharge capacity and longer cycle life.

[0171] The results of Examples 1-5 show that when the content of free lithium compounds in the core material is within an appropriate range, the initial discharge capacity and cycle life of the secondary battery can be further improved.

[0172] As can be seen from the results of Examples 3, 6-13, when the particle size distribution of the core material or positive electrode active material precursor is within an appropriate range, the initial discharge capacity and cycle life of the secondary battery can be further improved.

[0173] As can be seen from the results of Examples 3, 14-17, when the ratio of the core material and the positive electrode active material precursor is within an appropriate range, the initial discharge capacity and cycle life of the secondary battery can be further improved.

[0174] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a composite cathode material, comprising the following steps: A core material is provided, the core material comprising a lithium-rich metal oxide, the surface of which contains a free lithium compound; Provide precursors for positive electrode active materials; The positive electrode active material precursor is attached to at least a portion of the surface of the core material; The positive electrode active material precursor is reacted with the free lithium compound to form a positive electrode active material on at least a portion of the surface of the lithium-rich metal oxide, thereby obtaining the composite positive electrode material; The free lithium compound includes one or more of Li₂O, LiOH, and Li₂CO₃, and the mass percentage of the free lithium compound in the core material, as determined by titration, is 0.5 wt% to 15 wt%. The lithium-rich metal oxide is selected from Li2M. 1 O2, Li2M 2 O3, Li3M 3 O4, Li5M 4 O4, Li6M 5 One or more of O4, among which M 1 Including one or more of Ni, Co, Fe, Mn, Zn, Mg, Ca, and Cu, M 2 Including one or more of Mn, Sn, Mo, Ru, and Ir, M 3 Including one or more of V, Nb, Cr, and Mo, M 4 Including one or more of Fe, Cr, V, and Mo, M 5 Including one or more of Co, V, Cr, and Mo, In the lithium-rich metal oxide, the valence state of each metal element except Li is lower than its highest oxidation state; The positive electrode active material precursor is selected from Ni x1 Co y1 Mn z1 (OH)2, Ni x2 Co y2 Al z2 (OH)2, Ni x3 Co y3 Mn z3 CO3, Ni x4 Co y4 Al z4 One or more of CO3 and MPO4; wherein, x1+y1+z1=1; x2+y2+z2=1; x3+y3+z3=1; x4+y4+z4=1.

2. The method according to claim 1, wherein, The mass percentage of the free lithium compound in the core material, as determined by titration, is 1 wt% to 10 wt%.

3. The method according to claim 2, wherein, The mass percentage of the free lithium compound in the core material, as determined by titration, is 3 wt% to 7 wt%.

4. The method according to any one of claims 1-3, wherein, The mass ratio of the core material to the positive electrode active material precursor is 30:1 to 2:

1.

5. The method according to claim 4, wherein, The mass ratio of the core material to the positive electrode active material precursor is 25:1 to 10:

1.

6. The method according to claim 1, wherein, The volume average particle size D of the core material v 50 represents 1μm to 10μm.

7. The method according to claim 6, wherein, The volume average particle size D of the core material v 50 is 2μm~8μm.

8. The method according to claim 7, wherein, The volume average particle size D of the core material v 50 is 3μm~6μm.

9. The method according to claim 1, wherein, The volume average particle size D of the positive electrode active material precursor v 50 ranges from 0.05μm to 3μm.

10. The method according to claim 9, wherein, The volume average particle size D of the positive electrode active material precursor v 50 ranges from 0.05μm to 1.5μm.

11. The method according to claim 10, wherein, The volume average particle size D of the positive electrode active material precursor v 50 ranges from 0.1μm to 1.2μm.

12. The method according to claim 1, wherein, The water content of the core material is ≤500ppm.

13. The method according to claim 12, wherein, The water content of the core material is ≤200ppm.

14. The method according to claim 1, wherein, The lithium-rich metal oxide is selected from Li2NiO2, Li2CuO2, and Li2Ni a Cu b M 1-a-b One or more of O2, Li2MnO2, Li3VO4, Li3NbO4, Li5FeO4, and Li6CoO4, wherein 0 < a < 1, 0 < b < 1, and 0.9 < a ​​+ b ≤ 1, and M is selected from one or more of Zn, Sn, Mg, Fe, and Mn.

15. The method according to claim 14, wherein, The lithium-rich metal oxide is selected from Li2NiO2, Li2CuO2, and Li2Ni a Cu b M 1-a-b One or more of O2, Li5FeO4, and Li6CoO4.

16. The method of claim 14, wherein, 0.4≤a≤0.8, 0.2≤b≤0.

6.

17. The method according to claim 16, wherein, 0.5≤a≤0.7, 0.3≤b≤0.

5.

18. The method according to claim 1, wherein, The positive electrode active material precursor is selected from Ni x1 Co y1 Mn z1 (OH)2, Ni x2 Co y2 Al z2 One or more of (OH)2 and MPO4.

19. The method according to claim 1, wherein, The positive electrode active material precursor is selected from one or more of transition metal oxides, transition metal hydroxides, and transition metal carbonates. The volume average particle size D of the positive electrode active material precursor is... v 50 ranges from 0.5μm to 1.2μm; or, The positive electrode active material precursor is selected from one or more transition metal phosphates, and the volume average particle size D of the positive electrode active material precursor is selected from one or more transition metal phosphates. v 50 represents 0.1μm to 1μm.

20. The method according to claim 19, wherein, The positive electrode active material precursor is selected from one or more of transition metal oxides, transition metal hydroxides, and transition metal carbonates. The volume average particle size D of the positive electrode active material precursor is... v 50 is 0.6μm~1μm.

21. The method according to claim 20, wherein, The positive electrode active material precursor is selected from one or more transition metal phosphates, and the volume average particle size D of the positive electrode active material precursor is selected from one or more transition metal phosphates. v 50 is 0.4μm~0.6μm.

22. The method according to claim 1, wherein, The reaction of the positive electrode active material precursor with the free lithium compound includes: heat treatment at 600℃~800℃ for 2h~8h under a protective gas atmosphere.

23. A composite cathode material prepared by the method according to any one of claims 1-22.

24. A secondary battery, comprising a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer disposed on the positive current collector, the positive electrode film layer comprising at least a first positive electrode material, the first positive electrode material comprising the composite positive electrode material according to claim 23.

25. The secondary battery according to claim 24, wherein, The positive electrode film layer further includes a second positive electrode material, which includes one or more of lithium transition metal oxides and polyanionic positive electrode materials.

26. The secondary battery according to claim 25, wherein, The lithium transition metal oxide is selected from one or more of lithium cobalt oxide, lithium nickel oxide, layered lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, spinel lithium manganese oxide, spinel lithium nickel manganese oxide, and their modified materials.

27. The secondary battery according to claim 25, wherein, The polyanionic cathode material is selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium nickel phosphate, lithium manganese iron phosphate, and their modified materials.

28. A battery pack comprising a secondary battery according to any one of claims 24-27.

29. An electrical device comprising a secondary battery according to any one of claims 24-27, or a battery pack according to claim 28.

Images