Positive electrode active material and preparation method therefor, battery and electrical apparatus

Abstract

The invention relates to a positive electrode active material and a preparation method therefor, a battery, and an electrical apparatus. The positive electrode active material comprises first particles and vanadium oxide particles. The first particles comprise phosphate particles and a carbon layer arranged on at least part of the surface of the phosphate particles. The cycling performance of the battery can be improved.

Description

Positive electrode active material and preparation method thereof, battery and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311579760.8, filed on November 24, 2023, entitled “Positive Electrode Active Material, Preparation Method Thereof, Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to a positive electrode active material and a preparation method thereof, a battery and an electrical device. Background Art

[0004] Batteries, with their high capacity and long lifespan, are widely used in electronic devices such as mobile phones, laptops, electric bicycles, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy planes, and power tools. Due to the significant progress in the battery field, higher performance requirements are being placed on them. As a key component of batteries, the positive electrode active material has a significant impact on battery performance.

[0005] However, current positive electrode active materials have poor cycle performance when used in batteries.

[0006] Summary of the Invention

[0007] The present application provides a positive electrode active material and a preparation method thereof, a battery and an electrical device, which can improve the cycle performance of the battery.

[0008] In a first aspect, an embodiment of the present application provides a positive electrode active material, which includes first particles and vanadium oxide particles. The first particles include phosphate particles and a carbon layer disposed on at least a portion of the surface of the phosphate particles.

[0009] Therefore, in the embodiment of the present application, the positive electrode active material includes first particles and vanadium oxide particles, the first particles include phosphate particles and a carbon layer, the carbon layer has a coating effect on the phosphate particles, and can improve the capacity of the phosphate particles; because the vanadium oxide particles include vanadium oxide particles, they can react with HF, alleviate the side reaction between the phosphate particles and HF, and reduce the dissolution of transition metal ions; and the vanadium ions in the vanadium oxide particles can diffuse to the surface of the negative electrode plate to participate in the formation of the SEI film, improve the stability of the SEI film, construct a more stable interface between the electrolyte and the negative electrode plate, and slow down the decomposition of the electrolyte on the surface of the negative electrode plate, thereby improving the reliability, dynamic performance and cycle performance of the battery cell.

[0010] In some embodiments, the vanadium oxide particles include V2O5, V2O4, V2O3, VO, V a M b O c At least one of the following: wherein M is a transition metal element, 0 < a ≤ 5, 0 < b ≤ 5, and 0 < c ≤ 5; optionally, M includes one or more of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge. The vanadium oxide particles react rapidly with HF, reducing the risk of side reactions between HF and phosphate particles.

[0011] In some embodiments, the volume average particle size D of the vanadium oxide particles is v 50 is 20nm to 100μm, and can be optionally 50nm to 20μm. When the volume average particle size of the vanadium oxide particles is within the above range, it is beneficial to match with the first particles to increase the compaction density of the positive electrode active material, thereby increasing the energy density of the battery cell. Moreover, when the volume average particle size of the vanadium oxide particles is within the above range, the contact area between the vanadium oxide particles and the electrolyte is relatively large, which is conducive to the rapid reaction of the vanadium oxide with the electrolyte to consume HF, reducing the risk of HF contact with phosphate particles, thereby further improving the reliability and cycle performance of the battery cell.

[0012] In some embodiments, the volume average particle size D of the first particles is v 50 is 50 nm to 20 μm, and can be optionally 100 nm to 5 μm. When the volume average particle size of the first particles is within the above range, it is beneficial to match with the vanadium oxide particles and improve the overall compaction density of the positive electrode active material.

[0013] In some embodiments, the volume average particle size D of the vanadium oxide particles is v 50 is 20nm to 100nm; the volume average particle size D of the first particles v When the volume average particle size of the vanadium oxide particles is within the above range, and the volume average particle size of the vanadium oxide particles is relatively small, at the nanometer level, the vanadium oxide particles can fill the gaps formed by the accumulation of the plurality of first particles, thereby increasing the compaction density of the positive electrode active material and thus increasing the energy density of the battery cell.

[0014] In some embodiments, the volume average particle size D of the vanadium oxide particles is v 50 is 0.5 μm to 20 μm; the volume average particle size D of the first particles v50 is 50 nm to 500 nm. When the volume average particle size of the first particles is within the above range, the volume average particle size of the first particles is relatively small, and the particle size of the vanadium oxide particles is relatively large. The first particles fill the gaps formed by the accumulation of multiple vanadium oxide particles, thereby increasing the compaction density of the positive electrode active material, thereby increasing the energy density of the battery cell.

[0015] In some embodiments, the mass content of the vanadium oxide particles is 0.05% to 5.00% based on the total mass of the positive electrode active material, and optionally 1% to 3.5%. When the mass content of the vanadium oxide particles is within this range, they can fully react with the HF in the battery cell, reducing the HF content and significantly improving the performance of the battery cell. Furthermore, the vanadium oxide particles can be combined with the first particles to increase the compaction density of the powder, which is beneficial for improving the energy density of the battery cell.

[0016] In some embodiments, the mass content of the first particles is 95% to 99.95% (or optionally 96.5% to 99%) based on the total mass of the positive electrode active material. When the mass content of the first particles is within this range, they can work together with the vanadium oxide particles to increase the compaction density of the powder while improving the specific capacity and structural stability of the positive electrode active material.

[0017] In some embodiments, the phosphate particles include a molecular formula of Li 1+x Mn 1-y A y P 1-z R z Y w Compounds wherein -0.1 ≤ x ≤ 0.9, 0 < y < 1, 0 ≤ z ≤ 0.5, and 1.8 ≤ w ≤ 4; A comprises at least one of Fe, Co, Ni, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; R comprises at least one of S, Si, Cl, B, C, and N; and Y comprises at least one of O and F. Optionally, 0.3 ≤ y ≤ 0.6. The above-mentioned phosphate particles, when used in combination with vanadium oxide particles, can effectively improve the cycling stability of the positive electrode active material.

[0018] In some embodiments, the molar ratio of V to Mn in the positive electrode active material is (0.001 to 0.1): 1. When the molar ratio of V to Mn in the positive electrode active material is within the above range, the vanadium oxide particles can significantly reduce the risk of manganese dissolution and further improve the structural stability of the phosphate particles.

[0019] In some embodiments, the carbon layer has a mass content of 0.05% to 6% based on the total mass of the first particle. When the mass content of the carbon layer is within this range, it can effectively coat the phosphate particles, effectively reducing the risk of side reactions caused by direct contact between the phosphate particles and the electrolyte, and reducing the risk of transition metal ion dissolution, which is beneficial for improving the cycle performance and storage performance of the positive electrode active material. Furthermore, when the mass content of the carbon layer is within this range, it can effectively enhance the overall conductivity of the positive electrode active material, which is beneficial for utilizing the specific capacity of the phosphate particles.

[0020] In some embodiments, the powder compaction density of the positive electrode active material is 2.25 g / cm 3 to 2.60g / cm 3 When the compacted density of the positive electrode active material powder is within the above range, the energy density of the battery cell can be effectively improved.

[0021] In a second aspect, an embodiment of the present application provides a method for preparing a positive electrode active material, comprising:

[0022] Provide an organic carbon source to phosphate particles;

[0023] Carbonizing the organic carbon source to form a carbon layer on at least a portion of the surface of the phosphate particles to obtain first particles;

[0024] The vanadium oxide particles and the first particles are mixed to obtain a positive electrode active material.

[0025] In a third aspect, an embodiment of the present application proposes a positive electrode plate, which includes a positive electrode collector and a positive electrode film layer arranged on at least one side of the positive electrode collector, and the positive electrode film layer includes a positive electrode active material as in any embodiment of the first aspect of the present application, or a positive electrode active material prepared by the method of any embodiment of the second aspect of the present application.

[0026] In a fourth aspect, the present application further proposes a battery, comprising a positive electrode plate according to any embodiment of the third aspect of the present application.

[0027] In a fifth aspect, the present application further proposes an electrical device, which includes a battery as in any embodiment of the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0029] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0030] FIG. 2 is an exploded schematic diagram of an embodiment of the battery cell of FIG. 1 .

[0031] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0032] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0033] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0034] FIG6 is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0035] The drawings are not necessarily drawn to scale.

[0036] The accompanying drawings are described as follows: 1. battery pack; 2. upper case; 3. lower case; 4. battery module; 5. battery cell; 51. housing; 52. electrode assembly; 53. cover plate; 6. electrical device. DETAILED DESCRIPTION

[0037] Below, the embodiments of the positive electrode active material and its preparation method, battery and electrical device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0038] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3,4 and 5 are listed, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0040] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0041] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0042] Phosphate has a high theoretical specific capacity, which is beneficial to improving the energy density of battery cells; however, due to the poor electronic conductivity of phosphate, it is difficult to exert its capacity, which limits its application; in related technologies, in order to improve the capacity of phosphate, phosphate is usually coated and modified, such as using a carbon coating for modification, but further research has found that the electrolyte contains hydrofluoric acid HF, HF and phosphate containing a carbon coating may still cause serious side reactions, resulting in the dissolution of transition metal ions in the phosphate, such as manganese ions. The dissolved manganese ions migrate to the surface of the negative electrode and may be reduced to metallic manganese. Metallic manganese can catalyze the decomposition of the solid electrolyte interface (Solid Electrolyte Interphase, SEI) film on the surface of the negative electrode plate. Part of the decomposition byproducts is gas, which causes the battery to swell and affects the reliability of the battery cell; another part of the byproducts is deposited on the surface of the negative electrode plate, blocking the channel for lithium ions to enter and exit the negative electrode plate, resulting in an increase in the impedance of the battery cell and affecting the kinetic performance of the battery cell. Due to the decomposition of the SEI film, the electrolyte and lithium ions in the battery system are continuously consumed to form a new SEI film, which may also cause irreversible effects on the battery's capacity retention rate and deteriorate the cycle performance.

[0043] In view of the above problems, an embodiment of the present application proposes a positive electrode active material, which includes a first particle and a vanadium oxide particle. The first particle includes a phosphate particle and a carbon layer. The carbon layer has a coating effect on the phosphate particles, which can improve the capacity of the phosphate particles. Since the vanadium oxide particles include vanadium oxide particles, they can react with HF, alleviate the side reaction between the phosphate particles and HF, and reduce the dissolution of transition metal ions. Moreover, the vanadium ions in the vanadium oxide particles can diffuse to the surface of the negative electrode to participate in the formation of the SEI film, improve the stability of the SEI film, construct a more stable interface between the electrolyte and the negative electrode, and slow down the decomposition of the electrolyte on the surface of the negative electrode, thereby improving the reliability, dynamic performance and cycle performance of the battery cell.

[0044] Next, the technical solutions of the implementation methods of this application are described in detail.

[0045] positive electrode active material

[0046] In a first aspect, an embodiment of the present application provides a positive electrode active material.

[0047] The positive electrode active material includes first particles and vanadium oxide particles. The first particles include phosphate particles and a carbon layer disposed on at least a portion of the surface of the phosphate particles.

[0048] The carbon layer is disposed on at least a portion of the surface of the phosphate particles, providing excellent coating and protection for the phosphate particles. Because the carbon layer comprises a single carbon element, it has excellent electronic conductivity, which helps enhance the overall conductivity of the positive electrode active material and maximizes the capacity of the phosphate particles.

[0049] Vanadium oxide particles can reduce the risk of side reactions occurring when phosphate particles and the electrolyte come into direct contact; vanadium oxide particles can preferentially react with HF in the electrolyte, further reducing the risk of side reactions between HF and phosphate particles, thereby reducing the dissolution of transition metal ions such as manganese ions in the phosphate particles, which is beneficial to improving the stability of the phosphate particle structure; in addition, since the vanadium ions in the vanadium oxide particles can diffuse to the surface of the negative electrode and participate in the formation of the SEI film, the stability of the SEI film is improved, a more stable interface between the electrolyte and the negative electrode is constructed, the decomposition of the electrolyte on the surface of the negative electrode is slowed down, and the gas production and impedance in the battery system are reduced, thereby improving the reliability, dynamic performance and cycle performance of the battery cell.

[0050] In some embodiments, the vanadium oxide particles include V2O5, V2O4, V2O3, VO, V a M b O c At least one of the following, wherein M is a transition metal element, 0<a≤5, 0<b≤5, 0<c≤5; the above-mentioned vanadium oxide particles can react quickly with HF, reducing the risk of side reactions between HF and phosphate particles.

[0051] Optionally, M includes one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge.

[0052] For example, a can be 1, 2, 3, 4, 5, or a range consisting of any two of the above values.

[0053] Illustratively, b can be 1, 2, 3, 4, 5, or a range consisting of any two of the above values.

[0054] For example, c can be 1, 2, 3, 4, 5, or a range consisting of any two of the above values.

[0055] For example, V a M b O c It may include at least one of VFe2O5, V2TiO4, and VMgO3.

[0056] In some embodiments, the volume average particle size D of the vanadium oxide particles is v50 is 20nm to 100μm, and can be optionally 20nm to 20μm. When the volume average particle size of the vanadium oxide particles is within the above range, it is beneficial to match with the first particles to increase the compaction density of the positive electrode active material, thereby increasing the energy density of the battery cell. Moreover, when the volume average particle size of the vanadium oxide particles is within the above range, the contact area between the vanadium oxide particles and the electrolyte is relatively large, which is conducive to the rapid reaction of the vanadium oxide with the electrolyte to consume HF, reducing the risk of HF contact with phosphate particles, thereby further improving the reliability and cycle performance of the battery cell.

[0057] For example, the volume average particle size D of the vanadium oxide particles is v 50 is 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 68μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm or a range consisting of any two of the above values.

[0058] In some embodiments, the volume average particle size D of the first particles is v 50 is 50 nm to 20 μm, and can be 50 nm to 5 μm. When the volume average particle size of the first particles is within the above range, it is advantageous to match with the vanadium oxide particles and improve the overall compaction density of the positive electrode active material.

[0059] Illustratively, the average particle size of the first particles is 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range consisting of any two of the above values.

[0060] Optionally, the volume average particle size D of the vanadium oxide particles is v 50 is 20nm to 100nm; the volume average particle size D of the first particle v When the volume average particle size of the vanadium oxide particles is within the above range, and the volume average particle size of the vanadium oxide particles is relatively small, at the nanometer level, the vanadium oxide particles can fill the gaps formed by the accumulation of the plurality of first particles, thereby increasing the compaction density of the positive electrode active material and thus increasing the energy density of the battery cell.

[0061] Optionally, the volume average particle size D of the vanadium oxide particles is v 50 is 0.5 μm to 20 μm; the volume average particle size D of the first particle v 50 is 50 nm to 500 nm. When the volume average particle size of the first particles is within the above range, the volume average particle size of the first particles is relatively small, and the particle size of the vanadium oxide particles is relatively large. The first particles fill the gaps formed by the accumulation of multiple vanadium oxide particles, thereby increasing the compaction density of the positive electrode active material, thereby increasing the energy density of the battery cell.

[0062] In the embodiment of the present application, the volume average particle size D v 50 refers to the particle size corresponding to 50% of the volume distribution. It can be tested using equipment and methods known in the art. The positive electrode active material can be taken as a sample, or the positive electrode active material can be taken from a fresh battery cell as a sample. For example, after the fresh battery cell is fully discharged to 0% state of charge (SOC), the positive electrode sheet is disassembled, the positive electrode current collector is removed, and the positive electrode film layer is retained. The positive electrode film layer is immersed in N-methylpyrrolidone (NMP) to wash out the binder in the positive electrode film layer, retaining the positive electrode active material. After the positive electrode active material is dried, the volume average particle size Dv50 of the particles is measured using a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016. In the embodiment of the present application, the fresh battery cell can be a battery cell that has just left the factory (not subjected to charge and discharge cycles after formation), or a battery cell that has been assembled on an electrical device and has been cycled for less than 10 cycles.

[0063] In some embodiments, the mass content of the vanadium oxide particles is 0.05% to 5.00% based on the total mass of the positive electrode active material, and optionally 1% to 3.5%. When the mass content of the vanadium oxide particles is within this range, they can fully react with the HF in the battery cell, reducing the HF content and significantly improving the performance of the battery cell. Furthermore, the vanadium oxide particles can be combined with the first particles to increase the compaction density of the powder, which is beneficial for improving the energy density of the battery cell.

[0064] For example, the mass content of the vanadium oxide particles is 0.05%, 0.06%, 0.08%, 0.1%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95%, 0.98%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 2.9%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 3. %, 1.7%, 1.8%, 1.9%, 1.91%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0% or a range consisting of any two of the above values.

[0065] In some embodiments, the mass content of the first particles is 95% to 99.95% (or optionally 96.5% to 99%) based on the total mass of the positive electrode active material. When the mass content of the first particles is within this range, they can work together with the vanadium oxide particles to increase the compaction density of the powder while improving the specific capacity and structural stability of the positive electrode active material.

[0066] Illustratively, the mass content of the first particles can be 95%, 95.2%, 95.5%, 95.8%, 96.0%, 96.2%, 96.5%, 96.8%, 97.0%, 97.2%, 97.5%, 97.8%, 98.0%, 98.2%, 98.5%, 98.8%, 99.0%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, 99.95% or a range consisting of any two of the above values.

[0067] The phosphate particles may include manganese (Mn). In this case, the molar ratio of V to Mn in the positive electrode active material is (0.001 to 0.1):1. When the molar ratio of V to Mn in the positive electrode active material is within this range, the vanadium oxide particles can significantly reduce the risk of manganese dissolution and further enhance the structural stability of the phosphate particles.

[0068] For example, the molar ratio of V to Mn in the positive electrode active material may be 0.001:1, 0.002:1, 0.003:1, 0.004:1, 0.005:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1, 0.01:1, 0.012:1, 0.015:1, 0.018:1, 0.020:1, 0.022:1, 0.025:1, 0.028:1, 0.030:1, 0.032:1, 0.035:1, 0.038:1, 0.04 0:1, 0.042:1, 0.045:1, 0.048:1, 0.050:1, 0.052:1, 0.055:1, 0.058:1, 0.060:1, 0.061:1, 0.062:1, 0.063:1, 0.064:1, 0.065:1, 0.066:1, 0.067:1, 0.068:1, 0.069:1, 0.070:1, 0.071:1, 0.072:1, 0.073:1, 0.074:1, 0.075:1, 0.076: 1. 0.077:1, 0.078:1, 0.079:1, 0.080:1, 0.081:1, 0.082:1, 0.083:1, 0.084:1, 0.085:1, 0.086:1, 0.087:1, 0.088:1, 0.089:1, 0.090:1, 0.1:1 or a range consisting of any two of the above values.

[0069] In some embodiments, the phosphate particles include a molecular formula of Li 1+x Mn 1-y A y P 1-z R z Y w Compound, -0.1 ≤ x ≤ 0.9, 0 < y < 1, 0 ≤ z ≤ 0.5, 1.8 ≤ w ≤ 4; A comprises at least one of Fe, Co, Ni, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; R comprises at least one of S, Si, Cl, B, C, and N; and Y comprises at least one of O and F. The above-mentioned phosphate particles are used in combination with vanadium oxide particles to effectively improve the cycle stability of the positive electrode active material.

[0070] For example, x can be -0.1, -0.05, 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, or a range consisting of any two of the above values.

[0071] For example, y can be 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, y, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, or a range consisting of any two of the above values. Optionally, 0.3≤y≤0.6.

[0072] Illustratively, z can be 0, 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, or a range consisting of any two of the above values.

[0073] Illustratively, w can be 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, or a range consisting of any two of the above values.

[0074] Illustratively, the phosphate particles include Li 0.994Mn 0.65 Fe 0.35 Mo 0.001 P 0.999 Si 0.001 O 3.999 F 0.001 、Li 0.994 Mn 0.5 Fe 0.5 Mo 0.001 P 0.999 Si 0.001 O 3.999 F 0.001 、Li 0.994 Mn 0.4 Fe 0.6 Mo 0.001 P 0.999 Si 0.001 O 3.999 F 0.001 、Li 0.994 Mn 0.60 Fe 0.4 Mo 0.001 P 0.999 Si 0.001 O 3.999 F 0.001 、Li 0.994 Mn 0.65 Fe 0.35 Mo 0.001 PO 3.999 F 0.001 At least one of .

[0075] During the charge and discharge process, battery cells are accompanied by the deintercalation and deintercalation of active ions, such as Li, and their molar content varies when the battery cells are discharged to different states. The molar content of Li in the examples of positive electrode active materials in the embodiments of this application refers to the material's initial state, i.e., the state before the materials are added. When the positive electrode active material is used in a battery system, the molar content of Li may change after charge and discharge cycles.

[0076] In the examples of the positive electrode active materials in the embodiments of the present application, the molar content of oxygen O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate.

[0077] In some embodiments, the mass content of the carbon layer is greater than 0 and less than or equal to 6%, and can be optionally 2% to 5%, based on the total mass of the first particle. When the mass content of the carbon layer is within the above range, it can effectively coat the phosphate particles, effectively reducing the risk of side reactions caused by direct contact between the phosphate particles and the electrolyte, and reducing the risk of transition metal ion dissolution, which is beneficial for improving the cycling performance and storage performance of the positive electrode active material. Furthermore, when the mass content of the carbon layer is within the above range, it can effectively enhance the overall conductivity of the positive electrode active material, which is beneficial for utilizing the specific capacity of the phosphate particles.

[0078] For example, the mass content of the carbon layer can be 0.05%, 0.06%, 0.08%, 0.1%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95%, 0.98%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7% , 1.8%, 1.9%, 1.91, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6% or a range consisting of any two of the above values.

[0079] In some embodiments, the powder compaction density of the positive electrode active material is 2.25 g / cm 3 to 2.60g / cm 3 , for example, 2.25 g / cm 3 , 2.28g / cm 3 , 2.30g / cm 3 , 2.31g / cm 3 , 2.33g / cm 3 , 2.35g / cm 3 , 2.38g / cm 3 , 2.39g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , 2.6g / cm 3 When the compacted density of the positive electrode active material powder is within the above range, the energy density of the battery cell can be effectively improved.

[0080] In the embodiment of the present application, the powder compaction density of the positive electrode active material is a well-known meaning in the art and can be tested using equipment and methods well-known in the art. For example, a certain amount of the positive electrode active material sample prepared as described above is taken and placed in a UTM7305 electronic pressure testing machine with a bottom area of ​​1.327 cm 2 In a mold, pressurize to 2000 kg (equivalent to 20,000 N), maintain pressure for 30 seconds, then release the pressure and maintain for 10 seconds. The compacted density of the negative electrode active material powder under a force of 20,000 N is recorded and calculated. The test standard is in accordance with GB / T24533-2009.

[0081] Method for preparing positive electrode active material

[0082] In a second aspect, the present application also provides a method for preparing a positive electrode active material. The positive electrode active material of any embodiment of the first aspect of the present application can be prepared by this method. Of course, the positive electrode active material can also be prepared by commonly used methods in the art.

[0083] Methods include:

[0084] Step S100, providing an organic carbon source to phosphate particles;

[0085] Step S200, carbonizing the organic carbon source to form a carbon layer on at least a portion of the surface of the phosphate particles to obtain first particles;

[0086] Step S300 : mixing vanadium oxide particles and first particles to obtain a positive electrode active material.

[0087] According to the method implemented in the embodiment of the present application, the organic carbon source can form a carbon layer coated on the surface of the phosphate particles after carbonization treatment to form a first particle; the first particle is further mixed with the vanadium oxide particles, and the vanadium oxide particles can preferentially react with HF in the electrolyte, further reducing the risk of side reactions between HF and the phosphate particles, thereby reducing the dissolution of transition metal ions such as manganese ions in the phosphate particles, which is beneficial to improving the stability of the phosphate particle structure; in addition, since the vanadium ions in the vanadium oxide particles can diffuse to the surface of the negative electrode and participate in the formation of the SEI film, the stability of the SEI film is improved, a more stable interface between the electrolyte and the negative electrode is constructed, the decomposition of the electrolyte on the surface of the negative electrode is slowed down, and the gas production and the impedance in the battery system are reduced, thereby improving the reliability, dynamic performance and cycle performance of the battery cell.

[0088] [Step S100]

[0089] The organic carbon source may be in the form of solid particles, which may be dissolved in a solvent, and then the organic carbon source dissolved in the solvent is mixed with the phosphate particles. The solvent may be deionized water, for example.

[0090] Phosphate particles may include a molecular formula of Li 1+x Mn 1-y A y P 1-z R z Y w The compound, phosphate particles can be commercially obtained or synthesized according to the following method.

[0091] In some embodiments, a method for preparing phosphate particles comprises:

[0092] Step S110, dissolving the manganese source and the A source in a solvent, and drying the mixture to obtain a metal precursor;

[0093] Step S120, adding a metal precursor, a lithium source, a phosphorus source, and an R source into a solvent, grinding and mixing, and then spray drying to obtain a phosphate precursor;

[0094] Step S130 , sintering the phosphate precursor to form phosphate particles.

[0095] In step S110,

[0096] In some embodiments, the manganese source may be a manganese-containing substance known in the art that can be used to prepare phosphate. For example, the manganese source may include at least one of elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, and manganese carbonate.

[0097] In some embodiments, the source of A may include at least one of oxalate, phosphate, acetate, sulfate, citrate, and nitrate.

[0098] In some embodiments, the solvent may include at least one of deionized water and alcohols.

[0099] In step S120,

[0100] In some embodiments, the lithium source may include at least one of lithium carbonate, lithium acetate, lithium hydroxide, lithium nitrate, lithium sulfate, lithium chloride, lithium oxalate, lithium phosphate, lithium hydrogen phosphate, lithium citrate, lithium silicate, and lithium metaborate.

[0101] In some embodiments, the phosphorus source may include at least one of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0102] In some embodiments, the R source may include at least one of an R-containing acid, an R-containing oxide, and an R-containing organic compound. For example, the silicon source may include at least one of silicic acid, metasilicic acid, silicon tetrachloride, silicon dioxide, and tetraethyl orthosilicate. For example, the boron source may include at least one of boric acid, ammonium borate, and boron oxide.

[0103] In some embodiments, the solvent may include at least one of deionized water and alcohols.

[0104] In some embodiments, the grinding can be performed using a sand mill, for example, grinding and stirring in a sand mill for 8 to 10 hours.

[0105] In some embodiments, the spray drying granulation process can be carried out at 230° C. to 270° C. for 3.5 h to 5 h.

[0106] In step S130,

[0107] The sintering process may be performed in an inert atmosphere, and the inert atmosphere may be at least one of nitrogen and argon.

[0108] The sintering temperature may be 650° C. to 750° C., and the sintering time may be 8 h to 12 h.

[0109] The stoichiometric ratio of each substance in the above steps can be set according to the chemical formula of the desired phosphate particles. The content of each element in the material can be detected by inductively coupled plasma emission spectroscopy (ICP).

[0110] In some embodiments, the organic carbon source may include at least one of a carbohydrate compound, an olefin polymer, polyvinyl alcohol, polyethylene glycol, citric acid, and toluene.

[0111] Illustratively, the carbohydrate compound may include at least one of starch, sucrose, and glucose.

[0112] For example, the olefin polymer may include at least one of polyethylene and polytetrafluoroethylene.

[0113] The above substances can be selected from organic carbon sources such as polyethylene, polytetrafluoroethylene, toluene, etc. The hydroxyl content of the above substances is relatively small, or even contains no hydroxyl groups. The amount of residual hydroxyl groups after carbonization is relatively small, which is beneficial to improving the electrochemical performance of the positive electrode active material.

[0114] [Step S200]

[0115] In step S100, during the process of providing the organic carbon source to the phosphate particles, the organic carbon source and the phosphate particles are mixed. Since the organic carbon source is dissolved in the solvent to form a liquid phase, it can flow and coat the surface of the phosphate particles. After the organic carbon source and the phosphate particles are mixed for 4 to 6 hours, the system is carbonized. The carbonization process is as follows: the system can be pre-heat-treated and dried at 120°C to 200°C for 4 to 6 hours to remove the solvent; then sintered at 650°C to 750°C for 8 to 12 hours, and the organic carbon source is carbonized into a carbon layer, which coats at least part of the surface of the phosphate particles.

[0116] [Step S300]

[0117] The first particles and the vanadium oxide particles can be mixed and stirred evenly to obtain a positive electrode active material. The vanadium oxide does not substantially undergo a chemical reaction before and after mixing.

[0118] In some embodiments, the vanadium oxide particles include V2O5, V2O4, V2O3, VO, V a M b O c At least one of the following, wherein M is a transition metal element, 0<a≤5, 0<b≤5, 0<c≤5; the above-mentioned vanadium oxide particles can react quickly with HF, reducing the risk of side reactions between HF and phosphate particles.

[0119] Optionally, M includes one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge.

[0120] Positive electrode

[0121] In a third aspect, an embodiment of the present application proposes a positive electrode plate.

[0122] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and comprising a positive electrode active material. For example, the positive electrode current collector may have two opposing surfaces in its thickness direction, and the positive electrode film layer may be disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0123] The positive electrode active material may include the positive electrode active material of any embodiment of the first aspect of the present application, or the positive electrode active material obtained by the method of any embodiment of the second aspect of the present application. Since the positive electrode active material has good conductivity, its capacity utilization is improved, which is beneficial to improving the electrochemical performance of the positive electrode plate; in addition, since the side reaction between the positive electrode active material and the electrolyte is alleviated, when the positive electrode plate is applied to the battery cell, the expansion rate of the battery cell can be reduced, and the reliability, dynamic performance and cycle performance of the battery cell can be improved.

[0124] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present embodiments do not particularly limit the type of the positive electrode conductive agent. By way of example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent based on the total mass of the positive electrode film layer is ≤5%.

[0125] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and at least one of fluorine-containing acrylic resins. In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage of the positive electrode binder is ≤5%.

[0126] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0127] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0128] battery cells

[0129] In the fourth aspect, the embodiments of the present application also propose a battery cell, which includes a positive electrode plate as in any embodiment of the third aspect of the present application. Since the positive electrode active material in the positive electrode plate has good conductivity, its capacity is improved and the electrochemical performance of the positive electrode plate is improved; in addition, since the side reaction between the positive electrode active material and the electrolyte is alleviated, when the positive electrode plate is applied to the battery cell, the expansion rate of the battery cell can be reduced, and the reliability, dynamic performance and cycle performance of the battery cell can be improved.

[0130] [Negative electrode]

[0131] In some embodiments, the battery cell further includes a negative electrode plate.

[0132] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0133] The negative electrode active material can be any negative electrode active material known in the art for use in battery cells. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0134] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present embodiments do not particularly limit the type of negative electrode conductive agent. For example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent is ≤5 wt% based on the total weight of the negative electrode film layer.

[0135] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The present application embodiment does not particularly limit the type of negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), a water-soluble unsaturated resin SR-1B, a water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode binder is ≤5 wt% based on the total weight of the negative electrode film layer.

[0136] In some embodiments, the negative electrode film layer may optionally include other additives. For example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, and the like. In some embodiments, the weight percentage of the other additives is ≤ 2 wt % based on the total weight of the negative electrode film layer.

[0137] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0138] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0139] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0140] [Electrolyte]

[0141] In some embodiments, the battery cell further includes an electrolyte.

[0142] During the charge and discharge process of a battery cell, active ions are embedded and released back and forth between the positive and negative electrodes, and the electrolyte conducts the active ions between the positive and negative electrodes. The present application embodiment does not specifically limit the type of electrolyte, and the electrolyte can be selected based on actual needs.

[0143] The electrolyte solution includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected according to actual needs.

[0144] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0145] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene 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), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0146] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0147] [Isolation film]

[0148] The battery cell also includes a separator.

[0149] In some embodiments, the battery cell further includes a separator. The embodiments of the present application have no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0150] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0151] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process and / or a lamination process.

[0152] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0153] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell can also be a soft shell, such as a bag-type soft shell. The soft shell can be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0154] The present invention has no particular restrictions on the shape of the battery cell, which can be cylindrical, square, or any other shape. FIG1 shows a battery cell 5 with a square structure as an example.

[0155] In some embodiments, as shown in FIG2 , the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator may be formed into an electrode assembly 52 through a winding process and / or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be adjusted according to demand.

[0156] The preparation methods of the battery cells of the embodiments of the present application are well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be wound and / or laminated to form an electrode assembly. The electrode assembly is then placed in an outer packaging, dried, and then injected with electrolyte. The battery cell is then vacuum packaged, allowed to stand, formed, and shaped to obtain a battery cell.

[0157] In some embodiments of the present application, the battery cells according to the present application can be assembled into a battery module. The battery module can contain multiple battery cells, and the specific number can be adjusted according to the application and capacity of the battery module.

[0158] Figure 3 is a schematic diagram of an exemplary battery module 4. As shown in Figure 3 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0159] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0160] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0161] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 covers the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0162] Electrical devices

[0163] A fifth aspect of the embodiments of the present application provides an electrical device, which includes at least one of the battery cells, battery modules, or battery packs of the embodiments of the present application. The battery cells, battery modules, or battery packs can be used as power sources for the electrical device, or as energy storage units for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0164] The electrical device can select battery cells, battery modules or battery packs according to its usage requirements.

[0165] FIG6 is a schematic diagram of an exemplary electric device 6. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 6, a battery pack or battery module may be used.

[0166] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0167] Example

[0168] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0169] Example 1

[0170] 1. Preparation of positive electrode sheet

[0171] The positive electrode sheet includes a positive electrode current collector aluminum foil and a positive electrode film layer. The positive electrode film layer includes a film layer formed by uniformly coating the positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on the surface of the positive electrode current collector aluminum foil, drying, and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF), and acetylene black in a weight ratio of 90:5:5.

[0172] The positive electrode active material includes a first particle and a vanadium oxide particle. The first particle includes a phosphate particle and a carbon layer disposed on the surface of the phosphate particle. The phosphate particle includes a molecular formula of Li 0.994 Mn 0.65 Fe 0.35 Mo 0.001 P 0.999 Si 0.001 O 3.999 F 0.001 The preparation process of the positive electrode active material is as follows:

[0173] Sucrose was dissolved in 500 ml of deionized water, and then stirred and fully dissolved to obtain a coating solution. Phosphate particles were added to the coating solution, stirred and mixed for 6 hours. After mixing evenly, the mixture was transferred to a 150° C. oven for drying for 6 hours, and then sintered at 700° C. for 10 hours to obtain first particles.

[0174] 100 g of the first particles were placed in a sealed reaction chamber, stirred and mixed with the vanadium oxide particles, and reacted for 0.5 h to obtain the final positive electrode active material.

[0175] 2. Preparation of negative electrode sheet

[0176] The negative electrode sheet includes a negative electrode current collector copper foil and a negative electrode film layer. The negative electrode film layer includes a film layer formed by evenly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector copper foil, drying, and cold pressing. The negative electrode film layer includes a negative electrode active material, a conductive agent acetylene black, a binder styrene-butadiene rubber (SBR), and a thickener sodium carboxymethyl cellulose (CMC-Na) in a weight ratio of 95:2:2:1.

[0177] The negative electrode active material includes artificial graphite and hard carbon (mass ratio is 90:5).

[0178] 3. Isolation film

[0179] The isolation film is a polyethylene film.

[0180] 4. Preparation of electrolyte

[0181] The electrolyte includes an organic solvent, a lithium salt and an additive. The organic solvent includes ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1, and the lithium salt includes 1 mol / L LiPF6.

[0182] 5. Preparation of batteries

[0183] The lithium-ion battery includes an outer packaging shell, an electrode assembly and an electrolyte. The electrode assembly and the electrolyte are arranged in the outer packaging shell. The electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator. The electrode assembly is a wound electrode assembly, and the separator is arranged between the positive electrode sheet and the negative electrode sheet.

[0184] Comparative Example 1

[0185] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the positive electrode was prepared using the following steps:

[0186] The positive electrode sheet includes a positive electrode current collector aluminum foil and a positive electrode film layer. The positive electrode film layer includes a film layer formed by uniformly coating the positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on the surface of the positive electrode current collector aluminum foil, drying, and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF), and acetylene black in a weight ratio of 90:5:5.

[0187] The positive electrode active material includes phosphate particles and a carbon layer. The phosphate particles include a molecular formula of Li 0.994 Mn 0.65 Fe 0.35 Mo 0.001 P 0.999 Si 0.001 O 3.999 F 0.001 The preparation process of the positive electrode active material is as follows:

[0188] Dissolve 74.6 g of sucrose in 500 ml of deionized water, then stir and fully dissolve to obtain a coating solution. Add the above-mentioned phosphate particles to the coating solution, stir and mix together for 6 hours. After mixing evenly, transfer to a 150°C oven and dry for 6 hours, and then sinter at 700°C for 10 hours to obtain a positive electrode active material.

[0189] Example 2-1 to Example 2-4

[0190] A lithium ion battery was prepared using a method similar to that of Example 1, except that the content of vanadium oxide was adjusted.

[0191] Example 3-1 to Example 3-3

[0192] A lithium-ion battery was prepared using a method similar to that of Example 1, except that the type of vanadium oxide was adjusted.

[0193] Example 4-1 to Example 4-7

[0194] A lithium ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that at least one of the particle size of the vanadium oxide and the particle size of the first particles was adjusted.

[0195] Example 5-1 and Example 5-2

[0196] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the material of the positive electrode active material was adjusted.

[0197] In Example 5-1, the positive electrode active material includes first particles and vanadium oxide particles. The first particles include phosphate particles and a carbon layer disposed on the surface of the phosphate particles. The phosphate particles include a molecular formula of Li 0.994 Mn 0.5 Fe 0.5 Mo 0.001 P 0.999 Si 0.001 O 3.999 F 0.001 of compounds.

[0198] In Example 5-2, the positive electrode active material includes first particles and vanadium oxide particles. The first particles include phosphate particles and a carbon layer disposed on the surface of the phosphate particles. The phosphate particles include a molecular formula of Li 0.994 Mn 0.4 Fe 0.6 Mo 0.001 P 0.999 Si 0.001 O 3.999 F 0.001 of compounds.

[0199] Example 6-1 and Example 6-2

[0200] A lithium ion battery was prepared using a method similar to that of Example 1, except that the content of the carbon layer was adjusted.

[0201] Performance Testing

[0202] 1. Preparation of button batteries

[0203] The positive electrode sheet in Example 1 is used as the positive electrode sheet of the button battery;

[0204] A lithium sheet was used as the negative electrode, and the electrolyte included 1 mol / L LiPF6 and an organic solvent, wherein the organic solvent included ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1.

[0205] It is assembled into a button battery in a button box with the negative electrode sheet, positive electrode sheet and electrolyte.

[0206] 2. Measurement method of initial gram capacity of button battery

[0207] At a constant temperature of 25°C, charge the button battery to 4.3V at 0.1C, then charge it at a constant voltage at 4.3V until the current is less than or equal to 0.05mA, let it stand for 5 minutes, and then discharge it to 2.0V at 0.1C. The discharge capacity at this time is the initial gram capacity, recorded as D0.

[0208] 3. Cycling performance test of lithium-ion batteries at 45°C

[0209] At a constant temperature of 45°C, charge the lithium-ion battery at 1C to 4.3V. Then, charge it at a constant voltage at 4.3V until the current is less than or equal to 0.05mA. Let it rest for 5 minutes, then discharge it at 1C to 2.5V. Record the discharge capacity at this point as E0. Repeat the charge and discharge cycle until the discharge capacity drops to 80% of E0. Record the number of cycles the lithium-ion battery has completed.

[0210] 4. Measurement method of Mn (and Mn-doped Fe) dissolution after lithium-ion battery cycling

[0211] At 45° C., the lithium-ion battery, after being cycled until its capacity decayed to 80%, was discharged at a rate of 0.1 C to a cut-off voltage of 2.0 V.

[0212] Then disassemble the lithium-ion battery, take out the negative electrode sheet, and randomly select 30 unit areas (1540.25mm 2) discs were measured by inductively coupled plasma emission spectroscopy (ICP) using an Agilent ICP-OES730. The amounts of Fe (if Fe is doped at the Mn site of the cathode active material) and Mn were calculated based on the ICP results, thereby estimating the amount of Mn (and Fe doped at the Mn site) released after cycling. This testing was conducted in accordance with EPA-6010D-2014.

[0213] 5. Lithium-ion battery flatulence test at 60°C

[0214] Lithium-ion batteries with 100% state of charge (SOC) were stored at 60°C as test samples. The open circuit voltage (OCV) and AC internal resistance (IMP) of the lithium-ion batteries were measured before, during and after storage to monitor the SOC, and the volume of the lithium-ion batteries was measured.

[0215] After every 48 hours of storage, the lithium-ion battery was removed and allowed to rest for 1 hour before testing the open circuit voltage (OCV) and internal resistance (IMP). After cooling to room temperature, the battery volume was measured using the water displacement method. The water displacement method involves first measuring the battery's gravity, F1, using a balance that automatically converts unit data on the dial. The lithium-ion battery is then completely placed in deionized water (density known to be 1g / cm3) and the battery's gravity, F2, is measured. The buoyancy F of the battery is then calculated as F1-F2 based on Archimedes' principle: F = ρ × g × V_displacement, and the battery volume, V = (F1-F2) / (ρ × g).

[0216] From the OCV and IMP test results, the battery of the embodiment always maintained an SOC of more than 99% during the test until the end of storage.

[0217] After storage for 30 days, the battery volume was measured, and the percentage increase in the battery volume after storage relative to the battery volume before storage was calculated.

[0218] Test results

[0219] The test results are shown in Tables 1 and 2.

[0220] Table 1

[0221] In Table 1,

[0222] The mass content of vanadium oxide particles is calculated based on the total mass of the positive electrode active material.

[0223] The mass content of the first particles is calculated based on the total mass of the positive electrode active material.

[0224] The mass content of the carbon layer is calculated based on the total mass of the first particle.

[0225] Table 2

[0226] From Table 1 and Table 2, we can see that

[0227] Although the lithium iron phosphate particles are coated and modified with a carbon layer in Comparative Example 1, the modified material still has the risk of side reactions with the electrolyte, resulting in relatively poor performance of the lithium-ion battery.

[0228] In the embodiment of the present application, the positive electrode active material includes first particles and vanadium oxide particles. The vanadium oxide particles can react with HF, alleviate the side reaction between phosphate particles and HF, and reduce the dissolution of transition metal ions. Moreover, the vanadium ions in the vanadium oxide particles can diffuse to the surface of the negative electrode plate to participate in the formation of the SEI film, improve the stability of the SEI film, build a more stable electrolyte and negative electrode plate interface, slow down the decomposition of the electrolyte on the surface of the negative electrode plate, thereby improving the reliability, kinetic performance and cycle performance of the lithium-ion battery. In addition, the amount of Fe and Mn dissolved after cycling in the embodiment of the present application is less than or equal to 352ppm. The gram capacity of the positive electrode active material in the button cell in the embodiment of the present application is 140mAh / g to 150mAh / g.

[0229] Examples 2-1 to 2-4 and Examples 3-1 to 3-3 regulate the amount of vanadium oxide added and the material, respectively, to further optimize the performance of the lithium-ion battery. Examples 4-1 to 4-7 further enhance the performance of the lithium-ion battery by optimizing the particle size of the vanadium oxide particles and the first particles. Examples 5-1 and 5-2 regulate the material of the phosphate to further optimize the performance of the lithium-ion battery. Examples 6-1 and 6-2 regulate the amount of carbon layer added to further optimize the performance of the first particles and enhance the performance of the lithium-ion battery.

[0230] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A positive electrode active material, comprising first particles and vanadium oxide particles, wherein the first particles comprise phosphate particles and a carbon layer disposed on at least a portion of the surface of the phosphate particles.

2. The positive electrode active material according to claim 1, wherein The vanadium oxide particles include V2O5, V2O4, V2O3, VO, V a M b O c At least one of the following, wherein M is a transition metal element, 0<a≤5, 0<b≤5, 0<c≤5; Optionally, M includes one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge.

3. The positive electrode active material according to claim 1 or 2, wherein The volume average particle size D of the vanadium oxide particles v 50 is 20 nm to 100 μm, optionally 20 nm to 20 μm; and / or The volume average particle size D of the first particles v 50 is 50nm to 20μm, and can be optionally 50nm to 5μm; Optionally, The volume average particle size D of the vanadium oxide particles v 50 is 20nm to 100nm; the volume average particle size D of the first particles v 50: 0.3 μm to 5 μm; Optionally, The volume average particle size D of the vanadium oxide particles v 50 is 0.5 μm to 20 μm; the volume average particle size D of the first particles v 50 is 50 nm to 500 nm.

4. The positive electrode active material according to any one of claims 1 to 3, wherein Based on the total mass of the positive electrode active material, the mass content of the vanadium oxide particles is 0.05% to 5.00%; optionally 1% to 3.5%; and / or Based on the total mass of the positive electrode active material, the mass content of the first particles is 95% to 99.95%; optionally, 96.5% to 99%.

5. The positive electrode active material according to any one of claims 1 to 4, wherein The phosphate particles include a molecular formula of Li 1+x Mn 1-y A y P 1-z R z Y w A compound, -0.1≤x≤0.9, 0<y<1, 0≤z≤0.5, 1.8≤w≤4; A includes at least one of Fe, Co, Ni, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; R includes at least one of S, Si, Cl, B, C, N; Y includes at least one of O and F; optionally, 0.3≤y≤0.

6.

6. The positive electrode active material according to claim 5, wherein The molar ratio of V to Mn in the positive electrode active material is (0.001 to 0.1):

1.

7. The positive electrode active material according to any one of claims 1 to 6, wherein The carbon layer has a mass content of 0.05% to 6% based on the total mass of the first particle.

8. The positive electrode active material according to any one of claims 1 to 7, wherein The powder compaction density of the positive electrode active material is 2.25 g / cm 3 Up to 2.60g / cm 3 .

9. A method for preparing a positive electrode active material, comprising: Provide an organic carbon source to phosphate particles; Carbonizing the organic carbon source to form a carbon layer on at least a portion of the surface of the phosphate particles to obtain first particles; The vanadium oxide particles and the first particles are mixed to obtain a positive electrode active material.

10. A positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode active material according to any one of claims 1 to 8, or the positive electrode active material prepared by the method according to claim 9.

11. A battery, characterized in that: Comprising the positive electrode sheet as claimed in claim 10.

12. An electrical device, characterized in that: Comprising the battery of claim 11.

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