Positive electrode active material and method for producing the same, positive electrode piece, battery and electric device

Abstract

The present disclosure provides a positive electrode active material and a method for producing the same, a positive electrode piece, a battery, and an electric device, the positive electrode active material including a core and a carbon coating layer covering at least a part of the surface of the core, wherein the carbon coating layer is formed of sp 3 Hybridized carbon atoms and sp 2 The molar ratio of hybridized carbon atoms is greater than or equal to 0.5.

Description

[Technical Field]

[0001] This application relates to the field of batteries, and more particularly to positive electrode active materials and methods for making the same, positive electrode strips, batteries, and electrical devices. [Background technology]

[0002] In recent years, with the development of lithium ion battery technology, lithium ion batteries are widely used not only in energy storage power systems such as hydroelectric power plants, thermal power plants, wind power plants, and solar power plants, but also in many fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. At present, lithium ion batteries still have many challenges to be solved in terms of industrialized production and application. Summary of the Invention

[0003] In one aspect of the present application, the present application provides a polymeric nanoparticle having a core and a carbon coating layer covering at least a part of the surface of the core, wherein the carbon coating layer is formed of sp 2 Hybridized carbon atoms and sp 3 The present invention discloses a positive electrode active material having a molar ratio of hybridized carbon atoms of 0.5 or more, which can reduce the water absorption of the positive electrode active material.

[0004] According to an embodiment of the present application, the core comprises a phosphate, preferably at least one of lithium manganese phosphate, lithium iron phosphate, and lithium manganese iron phosphate, whereby a carbon coating is applied to the surface of the core material to enhance its electrical conductivity and optimize the performance of the battery using the core material.

[0005] According to an embodiment of the present application, the core comprises LiMPO4, and the M element comprises Mn and non-Mn elements, whereby the surface of the core material is coated with carbon to enhance its electrical conductivity and optimize the performance of the battery using the core material.

[0006] According to an embodiment of the present application, the non-Mn element includes one or both of a first doping element and a second doping element, and the first doping element is manganese site doped and the second doping element is phosphorus site doped, thereby improving the cycle stability of the positive electrode active material.

[0007] According to an embodiment of the present application, the first doping element includes one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and preferably includes at least two of Fe, Ti, V, Ni, Co, and Mg, thereby further increasing the gram capacity of the positive electrode active material.

[0008] According to an embodiment of the present application, the second doping element includes one or more elements of B (boron), S, Si, and N. This can further increase the gram capacity of the positive electrode active material.

[0009] According to an embodiment of the present application, the core is Li 1+x Mn 1-y A y P 1-z R z O4, where x is any value within the range of -0.100 to 0.100, y is any value within the range of 0.001 to 0.500, and z is any value within the range of 0.001 to 0.100, and the A includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and the R includes one or more elements selected from B (boron), S, Si, and N. This can improve the structural stability and capacity utilization rate of the positive electrode active material.

[0010] According to an embodiment of the present application, the core is Li 1+x C m Mn 1-y A y P 1-z R z O 4-n D nwherein x is any value within the range of -0.100 to 0.100, y is any value within the range of 0.001 to 0.500, z is any value within the range of 0.001 to 0.100, n is any value within the range of 0.001 to 0.1, and m is any value within the range of 0.9 to 1.1; C includes one or more elements of Zn, Al, Na, K, Mg, Nb, Mo, and W; A includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; R includes one or more elements of B (boron), S, Si, and N; and D includes one or more elements of S, F, Cl, and Br. This can further increase the gram capacity and compaction density of the positive electrode active material.

[0011] According to an embodiment of the present application, in the carbon coating layer, sp 2 Hybridized carbon atoms and sp 3 The molar ratio of hybridized carbon atoms is 0.8 or more, which can improve the structural order of the carbon coating layer, make the structure of the carbon coating layer more compact, reduce the pores on the carbon coating layer, and further reduce the water absorption of the positive electrode active material.

[0012] According to the embodiment of the present application, the thickness of the carbon coating layer is 10 nm or less, and preferably 4 nm to 8 nm, thereby reducing the water absorption and improving the conductivity of the positive electrode active material.

[0013] According to the embodiment of the present application, the carbon content of the positive electrode active material is 3 wt% or less, and preferably 1 wt% to 2.5 wt% of the carbon content of the positive electrode active material, so that the positive electrode active material has both good electrical conductivity and low water absorption.

[0014] According to the present embodiment, the specific surface area of ​​the positive electrode active material is 25 m 2 / g or less, and preferably, the specific surface area of ​​the positive electrode active material is 18 m 2This allows the positive electrode active material to have high electrical conductivity, high gram capacity, and low water absorption.

[0015] According to the embodiment of the present application, the average particle size of the positive electrode active material is 2 μm or less, and preferably 0.5 μm to 1.5 μm, which can increase the lithium ion migration rate of the positive electrode active material and increase the gram capacity of the positive electrode active material.

[0016] According to the embodiment of the present application, the powder resistivity of the positive electrode active material is 200 Ω cm or less, and preferably 100 Ω cm or less, so that the provision of the carbon coating layer can further improve the conductivity of the positive electrode active material while maintaining low water absorption.

[0017] In another aspect, the present application discloses a method for producing a positive electrode active material, the method including providing a core and forming a carbon coating layer on at least a portion of the surface of the core, thereby enabling the positive electrode active material to be obtained in a relatively simple manner, and the method has all the characteristics and advantages of the positive electrode active material, and therefore a description thereof will be omitted here.

[0018] According to an embodiment of the present application, forming a carbon coating layer on at least a portion of the core includes forming a pre-coated carbon coating layer on the core using a carbon source to obtain a pre-coated cathode active material, and sintering the pre-coated cathode active material in an inert gas atmosphere to form the carbon coating layer, thereby obtaining the cathode active material, where the carbon source includes a first carbon source and a second carbon source. This allows a carbon coating layer with a relatively high degree of graphitization to be formed on the core surface.

[0019] According to an embodiment of the present application, forming a carbon coating layer on at least a portion of the core includes mixing the core with the first carbon source and performing a first sintering process to obtain a first coated cathode active material, and mixing the first coated cathode active material with the second carbon source and performing a second sintering process to obtain the cathode active material, thereby forming a carbon coating layer with a relatively high degree of graphitization on the core surface.

[0020] According to an embodiment of the present application, the first carbon source includes at least one of polyvinyl alcohol, polyethylene glycol, and citric acid, and the second carbon source includes at least one of starch, sucrose, and glucose, thereby forming a carbon coating layer with a relatively high degree of graphitization on the core surface.

[0021] According to the examples of the present application, when the first carbon source is a polymer, the molecular weight of the first carbon source is 1000 or more, and preferably, the molecular weight of the first carbon source is 2000 to 5000. This makes it possible to obtain a carbon coating layer with a relatively high degree of graphitization.

[0022] According to an embodiment of the present application, the sintering temperature is 650°C to 800°C, and the sintering time is 6 hours to 12 hours, which allows a carbon coating layer with a relatively high degree of graphitization to be formed on the core surface.

[0023] According to an embodiment of the present application, the temperature of the first sintering treatment is 350°C to 800°C, and the time of the first sintering treatment is 6 hours to 12 hours, thereby forming a carbon coating layer with a relatively high degree of graphitization on the core surface.

[0024] According to an embodiment of the present application, the temperature of the second sintering treatment is 650°C to 850°C, and the time of the second sintering treatment is 6 hours to 24 hours, thereby forming a carbon coating layer with a relatively high degree of graphitization on the core surface.

[0025] In another aspect, the present application discloses a cathode piece including a cathode current collector and a cathode active material layer located on one side of the cathode current collector and including the cathode active material and / or the cathode active material produced by the method described above, thereby providing the cathode piece with all the features and advantages of the cathode active material, which will not be described further herein.

[0026] In another aspect, the present application discloses a battery including the above-described positive electrode piece, whereby the battery has all of the features and advantages of the above-described positive electrode piece, which are not described herein.

[0027] In another aspect, the present application discloses an electrical device including the battery described above, whereby the electrical device has all the features and advantages of the battery described above, which are not described here. [Brief explanation of the drawings]

[0028] The above and / or additional aspects and advantages of the present application will become more apparent and understandable from the following detailed description of the embodiments with reference to the accompanying drawings. [Figure 1] 1 is a structural schematic diagram of a positive electrode piece according to an embodiment of the present application; [Figure 2] 1 is a schematic diagram of a battery according to an embodiment of the present application. [Figure 3] FIG. 3 is an exploded view of the battery shown in FIG. 2 according to an embodiment of the present application. [Figure 4] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 5] 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Figure 6] FIG. 6 is an exploded view of the battery pack according to the embodiment of the present application shown in FIG. 5. [Figure 7] 1 is a schematic diagram of an electrical device that uses a battery as a power source according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0029] Examples of the present disclosure will be described in detail below. The examples described below are illustrative and are intended to explain the present disclosure only, and should not be understood as limiting the present disclosure. If no specific techniques or conditions are described in the examples, they will be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0030] In one aspect of the present application, the present application provides a polymerizable composition comprising a core and a carbon coating layer covering at least a part of the surface of the core, wherein the carbon coating layer is formed of sp 2 Hybridized carbon atoms and sp 3 The present invention discloses a positive electrode active material in which the molar ratio of hybridized carbon atoms is 0.5 or more. 2 Hybridized carbon atoms and sp 3 When the hybridized carbon atoms are within the above range, the pore structure of the carbon coating layer becomes relatively dense, which significantly reduces the water absorption capacity of the carbon coating layer, and further reduces the water absorption of the positive electrode active material, thereby improving the safety performance and cycle performance of the battery.

[0031] For ease of understanding, the following will explain the principle behind the positive electrode active material according to the present application having the above-mentioned beneficial effects.

[0032] Lithium-ion batteries are highly sensitive to moisture because their potential is significantly higher than the stable voltage range of water. Even trace amounts of moisture can have a significant impact on the performance of lithium-ion batteries, so the moisture content in materials must be strictly controlled throughout the entire production process. For example, during battery production, the electrode pieces must be dried after applying the current collector, the electrode pieces must be dried after cold pressing, and the battery core must be dried after winding. Furthermore, environmental moisture must be strictly controlled throughout the entire battery production process. Drying treatments and environmental moisture control during battery production consume a large amount of energy and complicate the battery production process flow.

[0033] In this application, the inventors discovered that forming a carbon coating layer on the core surface to improve the conductivity of the core can improve the conductivity of the positive electrode active material. Furthermore, when the carbon coating layer of the positive electrode active material is made porous, the porous carbon coating structure accelerates the absorption and retention of moisture by the positive electrode active material, thereby enhancing both the water absorption and water retention capabilities of the positive electrode active material. As a result, water absorption occurs during both storage and processing of the positive electrode active material, ultimately resulting in a high water content in the positive electrode active material. When the water content in the battery is high, the lithium salt in the electrolyte decomposes, significantly reducing the battery's cycle performance.

[0034] Furthermore, the inventors have found that simply increasing the temperature or extending the drying time in the drying process to remove as much moisture as possible from the positive electrode active material can result in problems such as excessive energy consumption and a significant increase in the process time. Furthermore, the inventors have found that prolonged high-temperature drying can adversely affect other assemblies in the battery core, such as the separator assembly, causing aging and failure, leading to a significant increase in manufacturing costs. Based on the above theoretical analysis and experimental investigation, the inventors have found that by improving the pore state of the carbon coating layer of the positive electrode active material, the water absorption of the positive electrode active material can be effectively reduced without excessively increasing the process flow or improving the process environment. Specifically, the inventors have found that the sp in the carbon coating layer on the core surface can be effectively reduced. 2 Hybridized carbon atoms and sp 3 It has been found that when the molar ratio of hybridized carbon atoms is 0.5 or more, the structural order of the carbon coating layer of the positive electrode active material is improved, and the pore structure of the carbon coating layer has high density and a small pore size distribution range, making it difficult for external moisture to enter the pores of the carbon coating layer during the battery manufacturing process, effectively reducing the water absorption and water retention of the positive electrode active material, improving the safety and cycle performance of the battery, effectively saving energy consumption in the drying process, and significantly reducing production costs.

[0035] According to some embodiments of the present application, the type of core is not particularly limited. For example, the core may include a phosphate. Preferably, the phosphate may include at least one of lithium manganese phosphate, lithium iron phosphate, and lithium manganese iron phosphate. Lithium manganese phosphate, lithium iron phosphate, and lithium manganese iron phosphate have high gram capacities and low raw material costs. When the positive electrode active material is applied to a battery, an electrochemical reaction occurs, requiring the participation of electrons. Therefore, a material with excellent electrical conductivity can be used to increase electron transport between particles and between different positions within the particle. Coating the surface of the phosphate core with a carbon layer can provide a positive electrode active material that combines low cost, high gram capacity, and high electrical conductivity, thereby optimizing the performance of a battery using the positive electrode active material.

[0036] According to some embodiments of the present application, the type of the core is not particularly limited. For example, the core may include LiMPO4, and the M element may include Mn and a non-Mn element. Preferably, the non-Mn element may include one or both of a first doping element and a second doping element, where the first doping element is manganese site doped and the second doping element is phosphorus site doped. The first doping element and the second doping element effectively reduce manganese elution, further reducing manganese ions migrating to the negative electrode and reducing electrolyte consumption due to SEI film decomposition, thereby improving the cycle performance and safety performance of the secondary battery. They also promote the adjustment of Mn-O bonds, reduce the barrier to lithium ion migration, promote lithium ion migration, and improve the rate performance of the battery.

[0037] According to some embodiments of the present application, the type of the first doping element is not particularly limited. For example, the first doping element may include one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge. Preferably, the first doping element may include at least two of Fe, Ti, V, Ni, Co, and Mg. The first doping element can further reduce the crystal lattice change rate of the positive electrode active material, reduce the surface activity of the material, and suppress Mn dissolution and interfacial side reactions between the positive electrode active material and the electrolyte. Doping with two or more metals within the above ranges is advantageous in enhancing the doping effect, further reducing surface oxygen activity, and suppressing manganese dissolution. In addition, doping with multiple elements enhances the synergistic effect between the elements, increasing battery capacity while simultaneously reducing the crystal lattice change rate of the material and improving the dynamic performance of the battery.

[0038] According to some embodiments of the present application, the type of the second doping element is not particularly limited. For example, the second doping element may include one or more of B (boron), S, Si, and N. The second doping element can increase the rate of change of the Mn-O bond, improve the barrier to small polarons in the cathode active material, and enhance electronic conductivity. Furthermore, doping with the second element can reduce the concentration of antisite defects in the material, improve the kinetic performance and gram capacity of the material, and further change the morphology of the material to increase the packing density of the material.

[0039] According to some embodiments of the present application, the type of the core is not particularly limited. For example, the core may be Li 1+x Mn 1-y A y P 1-z R zO4, where x is any value between -0.100 and 0.100, y is any value between 0.001 and 0.500, and z is any value between 0.001 and 0.100. A includes one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge. R includes one or more elements selected from the group consisting of B (boron), S, Si, and N. The manganese site doping element A, selected from the above elements, contributes to reducing the crystal lattice change rate of the lithium manganese phosphate during the lithium delithiation process, improving the structural stability of the positive electrode active material, significantly reducing manganese leaching, and reducing oxygen activity on the particle surface. The phosphite doping element R, selected from the above elements, also contributes to changing the difficulty of the Mn-O bond length, improving electronic conductivity, reducing the barrier to lithium ion migration, facilitating lithium ion migration, and improving the rate performance of secondary batteries. If the value of x is too small, the lithium content of the entire core will decrease, affecting the utilization rate of the gram capacity of the positive electrode active material. The value of y limits the total amount of all doping elements. If y is too small, i.e., the doping amount is too low, the doping elements will not be effective. If y exceeds 0.5, the Mn content in the system will be low, affecting the voltage platform of the positive electrode active material. Since the R element is doped at the P site and the PO tetrahedron is relatively stable, if the value of z is too large, the stability of the positive electrode active material will be affected. Therefore, when x, y, and z are selected within the above ranges, the positive electrode active material can have excellent performance.

[0040] Unless otherwise specified, when a doping site in the core formula has two or more elements, the above-mentioned limits on the numerical ranges of x, y, z, or m not only limit the stoichiometric number of each element at that site, but also limit the sum of the stoichiometric numbers of each element at that site. For example, if the chemical formula is Li 1+x Mn 1-y A y P 1-z R zIn the case of a compound in which A is two or more elements A1, A2...An, the stoichiometric numbers y1, y2...yn of A1, A2...An must each fall within the range of values ​​of y defined herein, and the sum of y1, y2...yn must also fall within this range. Similarly, when R is two or more elements, the limitations on the range of values ​​of the stoichiometric numbers of R defined herein also have the same meaning as above.

[0041] According to some embodiments of the present application, the type of the core is not particularly limited. For example, the core may be Li 1+x C m Mn 1-y A y P 1-z R z O 4-n D nThe value of x is influenced by the valence states of A and R, y, and z to ensure that the entire system remains electrically neutral. If the value of x is too small, the lithium content of the entire core system will decrease, affecting the utilization rate of the gram capacity of the material. The value of y limits the total amount of all doped elements. If y is too small, the doped elements will not be effective. If y exceeds 0.5, the Mn content in the system will be relatively low, affecting the voltage platform of the material. The R element is doped at the P site, and the PO tetrahedron is relatively stable. However, if the z value is too large, it will affect the stability of the material. Therefore, the z value is limited to 0.001-0.100. More specifically, x is any value within the range of -0.100 to 0.100, y is any value within the range of 0.001 to 0.500, z is any value within the range of 0.001 to 0.100, n is any value within the range of 0.001 to 0.1, and m is any value within the range of 0.9 to 1.1. For example, 1+x is selected from the range of 0.9 to 1.1, such as 0.97, 0.977, 0.984, 0.988, 0.99, 0.991, 0.992, 0.993, 0.994, 0.995, 0.996, 0.997, 0.998, 1.01, x is selected from the range of 0.001 to 0.1, such as 0.001, 0.005, and y is selected from 0.001, 0.005, 0.02, 0.05, 0.1, 0. z is selected from the range of 0.001 to 0.5, such as 0.15, 0.2, 0.25, 0.3, 0.34, 0.345, 0.349, 0.35, 0.4; z is selected from the range of 0.001 to 0.1, such as 0.001, 0.005, 0.08, 0.1; n is selected from the range of 0.001 to 0.1, such as 0.001, 0.005, 0.08, 0.1; and the positive electrode active material is electrically neutral. C includes one or more elements of Zn, Al, Na, K, Mg, Nb, Mo, and W; A includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; R includes one or more elements of B (boron), S, Si, and N; and D includes one or more elements of S, F, Cl, and Br.By simultaneously doping the Li site, Mn site, P site, and O site of the compound with specific elements in specific amounts, it is possible to obtain obviously improved rate performance, while at the same time significantly reducing the dissolution of the doped elements at the Mn and Mn sites, thereby obtaining significantly improved cycle performance and / or high-temperature stability, and also increasing the gram capacity and packed density of the positive electrode active material.

[0042] According to some embodiments of the present application, the carbon structure and properties of the carbon coating layer can be measured by Raman spectroscopy. Specifically, the Raman spectrum of the positive electrode active material is first measured, and the Raman spectrum is separated into peaks to obtain the I g / I d (where I d sp 3 is the peak intensity of the hybridized carbon atom, and I g isp 2 The peak intensity of the hybridized carbon atoms is the sp 2 Hybridized carbon atom peak height and sp 3 The ratio of the peak heights of the hybridized carbon atoms is obtained, and the sp 2 Hybridized carbon and sp 3 The molar ratio of sp in the carbon coating layer of the positive electrode active material is 2 Hybridized carbon atoms and sp 3 The molar ratio of hybridized carbon atoms is not particularly limited, and for example, 2 Hybridized carbon atoms and sp 3 The molar ratio of hybridized carbon atoms is 0.5 or more, and preferably, the sp 2 Hybridized carbon atoms and sp 3 The molar ratio of hybridized carbon atoms is 0.8 or more. 2 Hybridized carbon atoms and sp 3 When the molar ratio of hybridized carbon atoms is within the above range, the degree of graphitization of the carbon coating layer on the core surface becomes higher, the structure of the carbon coating layer becomes denser, and the water absorption of the carbon coating layer is reduced. This not only reduces the water absorption of the carbon coating layer, but also realizes excellent conductivity of the carbon coating layer, ensures the passage of lithium ions, and contributes to improving the cycle performance and safety performance of the positive electrode active material. 2 Hybridized carbon atoms and sp3 When the molar ratio of hybridized carbon atoms is less than 0.5, the amorphous sp 3 The carbon coating layer has a relatively porous structure, which is disadvantageous in reducing the water absorption of the carbon coating layer and also leads to poor electrical conductivity of the carbon coating layer.

[0043] According to some embodiments of the present application, the thickness of the carbon coating layer is not particularly limited. For example, the thickness of the carbon coating layer may be 10 nm, preferably 4 nm to 8 nm. Simply forming a thin carbon coating layer on the core surface can effectively improve the conductivity of the positive electrode active material and the pressing performance when using the positive electrode active material to manufacture battery pole pieces. A carbon coating layer thicker than 10 nm is likely to form with large voids, increasing the likelihood of the carbon coating layer absorbing and retaining water. A carbon coating layer that is too thick can affect the core lithium ion insertion and extraction and significantly reduce the gram capacity of the positive electrode active material. The thickness of the carbon coating layer is measured using the following method: A thin slice approximately 100 nm thick is cut from the center of a single particle of the positive electrode active material using an FIB. TEM examination is performed on the thin slice to obtain an original TEM image, which is then stored in original format (xx.dm3). The original image obtained from the above TEM test is opened in Digital Micrograph software, and the carbon coating layer is identified based on the crystal lattice spacing and angle information, and the thickness of the carbon coating layer is measured. The thickness is measured at three positions on the selected particle and the average value is taken.

[0044] According to some embodiments of the present application, the mass fraction of carbon in the positive electrode active material is not particularly limited. For example, the total mass of the core and the carbon coating layer may be 3 wt% or less, preferably 1 wt% to 2.5 wt%. When the mass fraction of carbon in the positive electrode active material is 3 wt% or less, the carbon content in the positive electrode active material is appropriate, improving the conductivity of the positive electrode active material, enhancing interparticle electron transport, and facilitating lithium ion migration. Furthermore, excessive carbon content does not adversely affect the gram capacity of the positive electrode active material. When the mass fraction of carbon in the positive electrode active material exceeds 3 wt%, it is difficult to form a carbon coating layer with a relatively high degree of graphitization on the core surface, and a carbon coating layer containing large voids is more likely to form, increasing the likelihood of the carbon coating layer absorbing and retaining water. The mass fraction of carbon in the positive electrode active material is measured using the following method. Turn on all power switches of the carbon and sulfur analyzer, and while holding down the "zero" button, open the oxygen valve of the carbon and sulfur analyzer and adjust the oxygen to a pressure of 0.02-0.04 MPa. Turn on the "front oxygen sensor" and "rear control sensor" and adjust the flow meter to maintain a flow rate of approximately 100 L / h. Add silicon molybdenum powder (0.3 g), weighed sample (250 mg), tin particles (0.3 g), and pure iron (1 g) to the crucible in this order, then close the crucible. Click the "Test" button to start the test. When the test is complete, the test results will be automatically displayed. Record the resulting carbon content.

[0045] According to some embodiments of the present application, the specific surface area of ​​the positive electrode active material is not particularly limited. For example, the specific surface area of ​​the positive electrode active material is 25 m 2 / g or less, and preferably, the specific surface area of ​​the positive electrode active material is 18 m 2 / g or less. When the specific surface area of ​​the positive electrode active material is within the above range, the pore structure of the carbon coating layer is relatively dense and the moisture absorption ability is weak, so the positive electrode active material can have high conductivity, high gram capacity, and low water absorption. When the specific surface area of ​​the positive electrode active material is 25 m 2If the specific surface area exceeds 1 / g, the positive electrode active material will have too large a specific surface area, which will result in strong water absorption and reduced battery cycle performance. The specific surface area of ​​the positive electrode active material is measured using the following method: Using the US-made Gemini VII 2390 Micro Multi-Depot fully automatic specific surface area and void analyzer, approximately 7g of sample is taken, placed in a 9cc long tube with a bulb, and degassed at 150°C for 15 minutes. The BET data is then obtained using this instrument.

[0046] According to some embodiments of the present application, the particle size of the positive electrode active material is not particularly limited. For example, the average particle size of the positive electrode active material may be 2 μm or less, and preferably, the average particle size of the positive electrode active material may be 0.5 μm to 1.5 μm. When the particle size of the positive electrode active material is within the above range, the particle size of the positive electrode active material becomes small, the lithium ion migration rate increases, and the gram capacity of the positive electrode active material can be effectively increased. The average particle size of the positive electrode active material is measured according to the following method: Equipment model: Malvern 3000 (MasterSizer 3000) laser particle size analyzer, standard process: GB / T19077-2016 / ISO13320:2009. Specific test process: Take an appropriate amount of sample to be tested (sample concentration should be 8-12% light blocking), add 20mL of deionized water, and apply external ultrasound for 5 minutes (53KHz / 120W) to ensure the sample is completely dispersed, then measure according to GB / T19077-2016 / ISO13320:2009 standards.

[0047] According to some embodiments of the present application, at least a portion of the surface of the core is coated with a porous carbon, e.g., a porous carbon layer, which can significantly improve the conductivity of the positive electrode active material. For example, the powder resistivity of the phosphate core positive electrode active material with a carbon coating layer on its surface can be 200 Ω·cm or less, preferably 100 Ω·cm or less. A low powder resistivity can effectively reduce the interfacial resistance between the positive electrode active materials and further reduce energy dissipation due to the internal resistance of the positive electrode active material. The powder resistivity of the positive electrode active material is measured using the following method: The powder resistivity is measured using an INITIAL ENERGY SCIENCE & TECHNOLOGY PRCD1000 device. The device is powered on, the test software is opened, the powder required for the test is weighed on a balance, the powder is pressed into a flake using a jig, the flake is placed in the device, the test parameters are set, the test pressure is 5 T, the dwell time is 5 s, and the test is performed. After the test is completed, the test results are displayed and recorded.

[0048] Regardless of whether words such as "about" or "approximately" are used in this application, all numbers disclosed herein are approximate values. Each numerical value may have an error of less than 10%, or an error of 1%, 2%, 3%, 4%, or 5%, which is considered reasonable by a person skilled in the art.

[0049] In another aspect, the present application discloses a method for producing a positive electrode active material, which allows the positive electrode active material to be obtained in a relatively simple manner, and thus has all the properties and advantages of the positive electrode active material, and therefore the description thereof is omitted here. Specifically, the method for producing a positive electrode active material includes the following steps:

[0050] S100: Provide the core According to some embodiments of the present application, in this step, a core of a positive electrode active material is provided. The type of the core of the positive electrode active material is not particularly limited. For example, the core can be selected from a positive electrode active material with a high gram capacity. For example, the core can be selected from a phosphate positive electrode active material such as lithium manganese phosphate, lithium iron phosphate, and lithium manganese iron phosphate. The core can also be selected from at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and a lithium-rich manganese-based solid solution. A carbon coating layer can be formed on the surface of the core to further improve the conductivity of the positive electrode active material, resulting in a positive electrode active material with both a high gram capacity and excellent cycle performance.

[0051] S200: Forming a carbon coating layer on at least a part of the surface of the core According to some embodiments of the present application, this step includes forming a carbon coating layer on at least a portion of the surface of the core.

[0052] S211: Form a preliminary carbon coating layer on the core surface using a carbon source According to some embodiments of the present application, in this step, a pre-carbon coating layer is formed on the core surface to obtain a pre-coated positive electrode active material. The method for forming the pre-carbon coating layer on the core surface is not particularly limited. For example, the carbon source and the core can be placed in the same reaction vessel and reacted with the carbon source on the core surface by hydrothermal treatment to form a carbon coating layer on the core surface. Alternatively, the carbon source and the core can be placed in a ball mill such as a sand mill and mechanically mixed to form a carbon coating layer on the core surface. According to another embodiment of the present application, the carbon source includes a first carbon source and a second carbon source, the first carbon source including at least one of polyvinyl alcohol, polyethylene glycol, and citric acid, and the second carbon source including at least one of starch, sucrose, and glucose. Preferably, the molecular weight of the first carbon source is 1,000 or more, more preferably, the molecular weight of the first carbon source may be 2,000 to 5,000. Therefore, ball milling can form a preliminary carbon coating layer that is uniformly distributed on the core surface and has a relatively consistent thickness, and also contributes to the formation of a dense and uniform pore structure in the carbon coating layer after sintering.

[0053] In the description of this application, "A and / or B" includes any one of the following situations: A alone, B alone, and A and B, where A and B are used only as examples, and refer to any technical feature connected by "and / or" in this application.

[0054] S212: Sintering the pre-coated positive electrode active material under an inert gas atmosphere According to some embodiments of the present application, in this step, the pre-coated positive electrode active material is sintered to obtain a positive electrode active material. The sintering should be performed in an inert atmosphere to prevent oxidation of the carbon source, which would prevent the formation of a carbon coating layer with a relatively high degree of graphitization. The type of inert gas is not particularly limited, and for example, the inert gas can include at least one of nitrogen and helium. The sintering conditions are not particularly limited, and for example, the sintering temperature may be 650°C to 800°C, and the sintering time may be 6 hours to 12 hours. This allows a carbon coating layer with a relatively high degree of graphitization to be formed on the core surface. The inventors have found that as the sintering temperature increases, the degree of graphitization of carbon in the carbon coating layer also increases. By controlling the maximum sintering temperature, the graphitization degree of the carbon coating layer can be effectively controlled, and the carbon coating layer thus formed has a dense pore structure and excellent electrical conductivity.

[0055] According to another embodiment of the present invention, this step includes forming a carbon coating layer on at least a part of the surface of the core.

[0056] S221: Mixing the core and the first carbon source and performing a first sintering process According to some embodiments of the present application, in this step, a first carbon coating layer is formed on the core surface using a first carbon source to obtain a first coated positive electrode active material. The type of the first carbon source is not particularly limited, and for example, the first carbon source may include at least one of polyvinyl alcohol, polyethylene glycol (PEG), and citric acid. Specifically, when the first carbon source is a polymer, the molecular weight of the first carbon source may be 1,000 or more, preferably 2,000 to 5,000. More specifically, the first carbon source may be polyethylene glycol with a molecular weight of 2,000 to 4,000.

[0057] According to some embodiments of the present application, the conditions for the first sintering process are not particularly limited. For example, the temperature for the first sintering process may be 350°C to 800°C, and the time for the first sintering process may be 6 hours to 12 hours, thereby finally forming a carbon coating layer with a relatively high degree of graphitization on the core surface.

[0058] S222: Mixing the first coated positive electrode active material and the second carbon source and performing a second sintering process. According to some embodiments of the present application, in this step, a positive electrode active material is obtained by a second sintering process. The type of the second carbon source is not particularly limited, and for example, the second carbon source may include at least one of starch, sucrose, and glucose. Preferably, the second carbon source may be glucose.

[0059] According to some embodiments of the present application, the first coated positive electrode active material and the second carbon source are mixed by adding the second carbon source to a selectable solvent and dissolving it at 20 to 60°C, then adding the first coated positive electrode active material to the solvent containing the second carbon source, followed by grinding and mixing for 6 to 24 hours to obtain a mixed solution, which is then dried and used in the second sintering process.

[0060] According to some embodiments of the present application, the conditions of the second sintering treatment are not particularly limited. For example, the temperature of the second sintering treatment may be 650°C to 850°C, and the time of the second sintering treatment may be 6 hours to 24 hours, thereby forming sp 2 Hybridized carbon atoms and sp 3 A carbon coating layer can be formed in which the molar ratio of hybridized carbon atoms is 0.5 or greater.

[0061] In another aspect of the present application, referring to FIG. 1 , the present application discloses a positive electrode piece 10 including a positive electrode current collector 11 and a positive electrode active material layer 12 located on one side of the positive electrode current collector 11 and including the above-described positive electrode active material. This allows the positive electrode piece to have all the features and advantages of the above-described positive electrode active material, and further description thereof will be omitted. For example, the positive electrode current collector 11 has two opposing surfaces in its thickness direction, and the positive electrode active material layer 12 is disposed on either or both of the two opposing surfaces of the positive electrode current collector 11.

[0062] According to some embodiments of the present application, the positive electrode pieces can be manufactured by the following method: The components for manufacturing the positive electrode pieces, such as the positive electrode active material, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, which is then applied onto a positive electrode current collector, and the positive electrode pieces are obtained through processes such as drying and cold pressing.

[0063] According to some embodiments of the present application, the adhesive is a polymer having the main functions of adhering and maintaining the positive electrode active material, strengthening the contact between the positive electrode active material and the conductive agent and between the positive electrode active material and the current collector, and simultaneously stabilizing the structure of the pole piece. According to other embodiments of the present application, the type of adhesive is not particularly limited, and for example, the adhesive may include at least one of polyvinylidene fluoride and polyacrylonitrile.

[0064] In another aspect, the present application discloses a battery including the above-described positive electrode piece. This battery thus possesses all of the features and advantages of the above-described positive electrode piece, and further description is omitted here. A battery typically includes a positive electrode piece, a negative electrode piece, an electrolyte, and a separator film. During the charge and discharge process of the battery, active ions are inserted and removed between the positive and negative electrode pieces. The electrolyte serves to conduct ions between the positive and negative electrode pieces. The separator film, located between the positive and negative electrode pieces, primarily serves to prevent short-circuiting between the positive and negative electrodes while allowing ions to pass through.

[0065] According to some embodiments of the present application, the shape of the battery is not particularly limited and may be cylindrical, polygonal, or any other shape. For example, FIG. 2 illustrates a polygonal battery 5 as an example. Specifically, referring to FIG. 3, the outer packaging may include a casing 51 and a cover plate 53. The casing 51 includes a base plate and a side plate connected to the base plate, and the base plate and side plate surround and form a storage chamber. The casing 51 has an opening communicating with the storage chamber, and the cover plate 53 can cover the opening and seal the storage chamber. The positive electrode pieces, negative electrode pieces, and separator film may be formed into an electrode assembly 52 by a winding or lamination process. The electrode assembly 52 is sealed in the storage chamber. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the battery 5 may be one or more, and those skilled in the art can select the number according to specific actual needs.

[0066] According to some embodiments of the present application, batteries may be assembled into a battery module. The number of batteries included in a battery module may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery module. FIG. 4 shows a battery module 4 as an example. Referring to FIG. 4, in the battery module 4, the plurality of batteries 5 may be arranged in sequence along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of batteries 5 may be fastened with fastening members. The battery module 4 may further include an outer case having an accommodation space for accommodating the plurality of batteries 5.

[0067] In this description, "plurality" means two or more than two.

[0068] According to some embodiments of the present application, the battery modules may be assembled into a battery pack. The battery pack may include one or more battery modules, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery pack. FIGS. 5 and 6 show a battery pack 1 as an example. Referring to FIGS. 5 and 6, the battery pack 1 may include a battery box and multiple battery modules 4 installed in the battery box. The battery box includes an upper case 2 and a lower case 3, and the upper case 2 is attached to the lower case 3 as a cover, forming a sealed space for accommodating the battery modules 4. Multiple battery modules 4 may be installed arbitrarily in the battery box.

[0069] In another aspect, the present application discloses an electric device including the battery described above. This electric device thus has all the features and advantages of the battery described above, and further description is omitted here. The battery, battery module, or battery pack can be used as a power source for the electric device or as an energy storage unit for the electric device. The electric device includes, 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. The electric device can select a battery, battery module, or battery pack according to its needs.

[0070] According to some embodiments of the present application, Fig. 7 illustrates an example of an electric device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A battery pack or a battery module can be used to meet the high power and high energy density needs of the battery of the electric device.

[0071] According to some embodiments of the present application, the electrical device may be a mobile phone, a tablet, a laptop, etc. The device is usually required to be light and thin and can use a battery as a power source.

[0072] The present invention will be described below with specific examples. For illustrative purposes, the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention. Unless specific techniques or conditions are described in the examples, they are carried out in accordance with the techniques or conditions described in the technical literature or in accordance with the product instructions. Unless the manufacturer of the reagents or equipment used is specified, they may be ordinary commercially available products.

[0073] Example 1: Step S1: 689.6 g of manganese carbonate, 455.27 g of ferrous carbonate, 4.65 g of cobalt sulfate, and 4.87 g of vanadium dichloride were added to a mixer and thoroughly mixed for 6 hours. The resulting mixture was then transferred to a reactor, and 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added. The mixture was heated to 80°C and thoroughly stirred at 500 rpm for 6 hours until the reaction was complete and no more bubbles were generated, resulting in a manganese oxalate suspension co-doped with Fe, Co, and V. The suspension was then filtered, dried at 120°C, and sand-milled to obtain manganese oxalate particles co-doped with Fe, Co, V, and S with a particle size of 100 nm.

[0074] Step S2: 1793.1 g of manganese oxalate produced in step S1, 368.3 g of lithium carbonate, 1146.6 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid were added to 20 L of deionized water, thoroughly stirred, and allowed to react uniformly at 80°C for 10 hours to obtain a slurry. The slurry was transferred to a spray dryer and spray-dried and granulated to obtain a powder material. The powder material was sintered in a tunnel kiln at 700°C for 4 hours in a protective atmosphere (90% nitrogen, 10% hydrogen) to obtain the core Li of the positive electrode active material. 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P0.997 S 0.003 Got O4.

[0075] Step S3: PEG-1000 was selected as the first carbon source. 58.2 g of PEG-1000 was dissolved in 500 g of deionized water and stirred to obtain an aqueous solution. 1571.9 g of the core material was added to the solution and stirred for 6 hours until the mixture was homogeneous. After spray drying, the solution was subjected to a first sintering process at 600°C for 9 hours. This produced a first coated cathode active material.

[0076] Step S4: Glucose was selected as the second carbon source. 37.3 g of glucose was dissolved in 500 g of deionized water and stirred to obtain a glucose aqueous solution. 1603.3 g of the first coated positive electrode active material obtained in step S3 was added to the glucose solution and stirred for 6 hours until the mixture was homogeneous. After spray drying, the mixture was subjected to a second sintering process at 750°C for 20 hours. This produced a positive electrode active material.

[0077] Examples 2 to 20 and Comparative Examples 1 to 3 are the same as Example 1 except for the selection of the carbon source and the temperature of the sintering treatment. See Table 1 for details.

[0078] [Table 1]

[0079] For illustrative purposes, PEG-1000 refers to polyethylene glycol having a molecular weight of 900 to 1100, PEG-1500 refers to polyethylene glycol having a molecular weight of 1350 to 1650, PEG-2000 refers to polyethylene glycol having a molecular weight of 1800 to 2200, PEG-3000 refers to polyethylene glycol having a molecular weight of 2700 to 3300, PEG-4000 refers to polyethylene glycol having a molecular weight of 3500 to 4400, PEG-6000 refers to polyethylene glycol having a molecular weight of 5500 to 7000, PEG-8000 refers to polyethylene glycol having a molecular weight of 7200 to 8800, PEG-10000 refers to polyethylene glycol having a molecular weight of 8500 to 11500, and PEG-20000 refers to polyethylene glycol having a molecular weight of 19000 to 21000.

[0080] The following tests were carried out on the positive electrode active materials of Examples 1 to 11 and Comparative Examples 1 to 3. The test results are shown in Table 2.

[0081] 1. Measurement of the hybridization of carbon atoms in the carbon coating layer: This test is carried out by Raman spectroscopy. By splitting the peaks of the Raman spectrum, I g / I d where I d sp 3 is the peak intensity of hybridized carbon, and I g isp 2 This is the peak intensity of the hybrid carbon, and the molar ratio of the two was confirmed.

[0082] 2. Measurement of the carbon coating layer thickness: To measure the thickness of the carbon coating layer, a thin slice approximately 100 nm thick was cut from the center of a single particle of the above-prepared positive electrode active material using an FIB. The slice was then subjected to TEM testing to obtain an original TEM image, which was saved in original image format (xx.dm3). The original image obtained from the above TEM test was opened in Digital Micrograph software, and the carbon coating layer was identified based on the crystal lattice spacing and angle information, and the thickness of the carbon coating layer was measured. The thickness was measured at three positions on the selected particle and the average value was calculated.

[0083] 3. Measurement of carbon element content in positive electrode active material: Turn on all power switches of the carbon and sulfur analyzer, hold down the "zero" button, open the oxygen valve of the carbon and sulfur analyzer, and adjust the oxygen pressure to 0.02-0.04 MPa. Turn on the "front oxygen sensor" and "rear control sensor" and adjust the flow meter to approximately 100 L / h. Add silicon molybdenum powder (0.3 g), weighed sample (250 mg), tin particles (0.3 g), and pure iron (1 g) to the crucible in this order, and close the crucible. Click the "Test" button to start the test. When the test is complete, the test results will be automatically displayed, and the resulting carbon content should be recorded.

[0084] 4. Measurement of the specific surface area of ​​the positive electrode active material: Using the American micro-multi-depot fully automatic specific surface area and void analyzer Gemini VII 2390, approximately 7 g of the positive electrode active material sample was taken, placed in a 9 cc long tube with a spherical part, and degassed at 150 °C for 15 minutes, and then measured with this instrument to obtain the BET data.

[0085] 5. Measurement of the average particle size of the positive electrode active material: Equipment model: Malvern 3000 (MasterSizer3000) laser particle size analyzer, standard process: GB / T19077-2016 / ISO13320:2009. Specific test process: Take an appropriate amount of sample to be tested (sample concentration should be 8-12% opacity), add 20mL of deionized water, and simultaneously apply external ultrasound (53KHz / 120W) for 5 minutes to ensure the sample is completely dispersed, then measure according to GB / T19077-2016 / ISO13320:2009.

[0086] 6. Measurement of powder resistivity of positive electrode active material: Use INITIAL ENERGY SCIENCE & TECHNOLOGY's PRCD1000 device to measure the powder resistivity. Turn on the device, open the test software, weigh out the powder required for the test on a balance, use a jig to press the powder into a thin piece, place the thin piece into the device, set the test parameters, set the test pressure to 5t, set the dwell time to 5s, click to test, and when the test is finished, the test results will be displayed and recorded.

[0087] 7. Measurement of water absorption of positive electrode active material: 5 g of positive electrode active material sample was taken and dried by heating at 110°C for 12 hours. The sample was then placed in a vial and placed in the automatic sampling system of the Karl Fischer instrument. During the test, the vial containing the sample was heated to 250°C and dried gas was passed through it. The gas in the vial was purged into a titration cup to perform absorption titration. The result was converted into the water content of the solid sample.

[0088] 8. Measurement of gram capacity of positive electrode active material: (1) Preparation of button battery: The prepared positive electrode active material, polyvinylidene fluoride (PVDF), and acetylene black were added to N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5, and stirred in a drying chamber to form a slurry. The slurry was applied to aluminum foil, dried, and cold pressed to form a positive electrode piece. The application amount was 0.2 g / cm. 2 and the compression density is 2.0 g / cm 3 The lithium pieces were used as the negative electrode, and a solution of 1 mol / L LiPF6 mixed with ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1 was used as the electrolyte. Together with the positive electrode pieces prepared above, they were assembled into a button battery in a coin-shaped assembly box.

[0089] (2) Measurement of the initial gram capacity of the button battery: The button battery was charged from 2.5 V to 4.3 V at 0.1 C up to 4.3 V, then charged at a constant voltage of 4.3 V until the current was 0.05 mA or less, allowed to stand for 5 minutes, and then discharged at 0.1 C down to 2.0 V. The discharge capacity at this time was the initial gram capacity, which was taken as the gram capacity of the positive electrode active material.

[0090] The positive electrode active materials of Examples 1 to 11 and Comparative Examples 1 to 3 were used to manufacture full batteries, respectively, and the manufacturing process of the full batteries was as follows.

[0091] The positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive were mixed uniformly in a weight ratio of 92:2.5:5.5 in an N-methylpyrrolidone solvent system, and then coated on aluminum foil, dried, and cold pressed to obtain a positive electrode piece. The coating amount was 0.4 g / cm. 2 and the compression density is 2.4 g / cm 3 is.

[0092] The negative electrode active materials, artificial graphite and hard carbon, the conductive agent acetylene black, the adhesive styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC), were mixed uniformly in deionized water in a weight ratio of 90:5:2:2:1, and then coated on copper foil, dried, and cold pressed to obtain negative electrode pieces. The coating amount was 0.2 g / cm. 2 and the compression density is 1.7 g / cm 3 is.

[0093] A porous polyethylene (PE) polymer film was used as a separator film, and the positive electrode, separator film, and negative electrode pieces were stacked in this order, with the separator film between the positive and negative electrodes to act as an insulator, and then wound up to obtain a bare cell. The bare cell was placed inside a housing, and the electrolyte was injected and sealed to obtain a full battery.

[0094] A cycle performance test was conducted on all the batteries of Examples 1 to 11 and Comparative Examples 1 to 3. The cycle performance test for all the batteries was as follows. In a constant temperature environment of 45°C, all the batteries were charged from 2.5 V to 4.3 V at 1 C up to 4.3 V, and then charged at a constant voltage until the current at 4.3 V became 0.05 mA or less. After leaving the batteries to stand for 5 minutes, they were discharged at 1 C down to 2.5 V, and the discharge capacity at this time was recorded as D0. The above charge / discharge cycle was repeated until the discharge capacity decreased to 80% of D0. The number of cycles of the battery at this point was recorded. The test results are shown in Table 2.

[0095] [Table 2]

[0096] Test results showed that sp in the carbon coating layer of the positive electrode active material 2 Hybridized carbon and sp 3 When the molar ratio of the hybrid carbon is less than 0.5, the water absorption of the positive electrode active material is significantly improved, and all of them are above 890 ppm. Accordingly, the content is too high, which causes the decomposition of the lithium salt in the battery electrolyte, and the cycle performance of the battery is significantly reduced.

[0097] It should be understood that in the above examples and comparative examples, the same core was selected for the subsequent preparation of the positive electrode active material in order to control variables. That is, the selection of the core material is exemplary, and the relevant features of the carbon coating layer of the positive electrode active material herein can be combined with other core materials in an appropriate manner. For example, the types of core materials may include at least one of lithium manganese phosphate, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminum oxide, and a lithium-rich manganese-based solid solution. Forming the carbon coating layer on the core surface further improves the conductivity of the positive electrode active material, resulting in a positive electrode active material that combines high gram capacity and excellent cycle performance.

[0098] Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. All patents and publications pertaining to this application are incorporated herein by reference in their entirety. The terms "comprises" or "including" are open-ended, i.e., include the subject matter specified in this application but do not exclude other aspects.

[0099] In the description herein, the reference terms "one embodiment," "another embodiment," and the like mean that the specific feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. In the description herein, the descriptive expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, a person skilled in the art may combine different embodiments or examples and features of different embodiments or examples described herein without mutually contradicting each other. It should also be noted that the terms "first" and "second" used herein are merely for descriptive purposes and should not be understood as indicating or implying relative importance or the quantity of the technical features indicated.

[0100] Although the embodiments of the present application have been shown and described above, the above embodiments are illustrative and should not be understood as limiting the present application, and it will be understood that those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present application. [Explanation of symbols]

[0101] 1 battery pack 2 Upper case 3 Lower case 4 Battery Module 5 batteries 10 Positive electrode piece 11 Positive electrode current collector 12 Positive electrode active material layer 51 Casing 52 Electrode Assembly 53 Top cover assembly

Claims

1. A positive electrode active material, The core and a carbon coating layer covering at least a portion of the surface of the core; In the carbon coating layer, sp ２ Hybridized carbon atoms and sp ３ the molar ratio of hybridized carbon atoms is 0.5 or more; Positive electrode active material.

2. the core comprises a phosphate, preferably the phosphate comprises at least one of lithium manganese phosphate, lithium iron phosphate, and lithium manganese iron phosphate; The positive electrode active material of claim 1 .

3. The core is LiMPO ４ wherein the M element includes a Mn element and a non-Mn element. The positive electrode active material of claim 1 .

4. The non-Mn element includes one or both of a first doping element and a second doping element, the first doping element is manganese site doping, and the second doping element is phosphorus site doping; The positive electrode active material of claim 3 .

5. the first doping element comprises one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, preferably the first doping element comprises at least two of Fe, Ti, V, Ni, Co and Mg; The positive electrode active material of claim 4.

6. The second doping element includes one or more elements of B (boron), S, Si, and N; The positive electrode active material of claim 4.

7. The core is Li １＋ｘ Mn １－ｙ A ｙ P １－ｚ R ｚ O ４ wherein x is an arbitrary value within a range of -0.100 to 0.100, y is an arbitrary value within a range of 0.001 to 0.500, z is an arbitrary value within a range of 0.001 to 0.100, A includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and R includes one or more elements of B (boron), S, Si, and N. The positive electrode active material according to any one of claims 3 to 6.

8. The core is Li １＋ｘ C ｍ Mn １－ｙ A ｙ P １－ｚ R ｚ O ４－ｎ D ｎ wherein x is an arbitrary value within a range of -0.100 to 0.100, y is an arbitrary value within a range of 0.001 to 0.500, z is an arbitrary value within a range of 0.001 to 0.100, n is an arbitrary value within a range of 0.001 to 0.1, and m is an arbitrary value within a range of 0.9 to 1.1; C includes one or more elements of Zn, Al, Na, K, Mg, Nb, Mo, and W; A includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; R includes one or more elements of B (boron), S, Si, and N; and D includes one or more elements of S, F, Cl, and Br. The positive electrode active material according to any one of claims 3 to 6.

9. In the carbon coating layer, sp ２ Hybridized carbon atoms and sp ３ the molar ratio of hybridized carbon atoms is 0.8 or more; The positive electrode active material according to any one of claims 1 to 8.

10. The thickness of the carbon coating layer is 10 nm or less, and preferably, the thickness of the carbon coating layer is 4 nm to 8 nm. The positive electrode active material according to any one of claims 1 to 9.

11. In the positive electrode active material, the content of carbon element is 3 wt % or less, and preferably, in the positive electrode active material, the content of carbon element is 1 wt % to 2.5 wt %. The positive electrode active material according to any one of claims 1 to 10.

12. The specific surface area of ​​the positive electrode active material is 25 m ２ / g or less, and preferably the specific surface area of ​​the positive electrode active material is 18 m ２ / g or less, The positive electrode active material according to any one of claims 1 to 11.

13. The average particle size of the positive electrode active material is 2 μm or less, and preferably, the average particle size of the positive electrode active material is 0.5 μm to 1.5 μm. The positive electrode active material according to any one of claims 1 to 12.

14. The powder resistivity of the positive electrode active material is 200 Ω cm or less, and preferably, the powder resistivity of the positive electrode active material is 100 Ω cm or less. The positive electrode active material according to any one of claims 1 to 13.

15. Providing a core and forming a carbon coating layer on at least a part of the surface of the core, wherein the carbon coating layer is ２ Hybridized carbon atoms and sp ３ Produce a positive electrode active material, wherein the molar ratio of hybridized carbon atoms is 0.5 or more; method.

16. forming a carbon coating layer on at least a portion of the surface of the core includes: forming a pre-coated carbon coating layer on the surface of the core using a carbon source to obtain a pre-coated positive electrode active material; and sintering the pre-coated positive electrode active material to form the carbon coating layer, thereby obtaining the positive electrode active material, wherein the carbon source includes a first carbon source and a second carbon source; 16. The method of claim 15.

17. forming a carbon coating layer on at least a portion of the surface of the core includes: mixing the core with the first carbon source and performing a first sintering process to obtain a first coated positive electrode active material; and mixing the first coated positive electrode active material with the second carbon source and performing a second sintering process to obtain the positive electrode active material.

16. The method of claim 15.

18. the first carbon source comprises at least one of polyvinyl alcohol, polyethylene glycol, and citric acid, and the second carbon source comprises at least one of starch, sucrose, and glucose; 18. The method of claim 16 or 17.

19. When the first carbon source is a polymer, the molecular weight of the first carbon source is 1000 or more, preferably 2000 to 5000. The method according to any one of claims 16 to 18.

20. The sintering temperature is 650°C to 800°C, and the sintering time is 6 hours to 12 hours.

20. The method of claim 16, 18 or 19.

21. The temperature of the first sintering treatment is 350°C to 800°C, and the time of the first sintering treatment is 6 hours to 12 hours. The method according to any one of claims 17 to 19.

22. The temperature of the second sintering treatment is 650°C to 850°C, and the time of the second sintering treatment is 6 hours to 24 hours. The method according to any one of claims 17 to 19.

23. a positive electrode current collector; and a positive electrode active material layer located on one side of the positive electrode current collector, the positive electrode active material layer comprising the positive electrode active material according to any one of claims 1 to 14 and / or the positive electrode active material produced by the method according to any one of claims 15 to 22. Positive electrode piece.

24. 24. A cathode piece according to claim 23, battery.

25. 25. A battery comprising the battery of claim 24. Electrical equipment.

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