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

Abstract

The invention relates to a positive electrode active material and a preparation method thereof, a battery and a power utilization device, the positive electrode active material comprises first particles and vanadium oxide particles, and the first particles comprise phosphate particles and carbon layers arranged on at least part of the surfaces of the phosphate particles. The cycle performance of the battery can be improved.

Description

Technical Field

[0001] The present application relates to a positive electrode active material, a preparation method thereof, a battery, and an electrical device. Background Art

[0002] Batteries have characteristics such as high capacity and long life, and thus are widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and electric tools, etc. Due to the great progress in the battery field, higher requirements are put forward for the performance of batteries. As an important component of the battery, the positive electrode active material has a significant impact on the battery performance.

[0003] However, at present, when the positive electrode active material is applied to a battery, the cycle performance of the battery is poor. Summary of the Invention

[0004] The present application provides a positive electrode active material, a preparation method thereof, a battery, and an electrical device, which can improve the cycle performance of the battery.

[0005] 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 part of the surface of the phosphate particles.

[0006] Thus, 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 plays a role in coating the phosphate particles, which can improve the capacity utilization of the phosphate particles. Since the vanadium oxide particles include vanadium oxide particles, they can react with HF, relieve 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 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 use reliability, kinetic performance, and cycle performance of the battery cell.

[0007] In some embodiments, the vanadium oxide particles include V 2 O 5 、V 2 O 4 、V 2 O 3 、VO、V a M b O cat least one of them, where M is a transition metal element, 0 < a ≤ 5, 0 < b ≤ 5, 0 < c ≤ 5; optionally, M includes one or more elements among Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge. The above vanadium oxide particles can react with HF quickly, reducing the risk of side reactions between HF and phosphate particles.

[0008] In some embodiments, the volume average particle size D v 50 of the vanadium oxide particles is from 20 nm to 100 μm, and optionally from 50 nm to 20 μm. 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, improving the tap density of the cathode active material, thereby enhancing 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 vanadium oxide reacting with the electrolyte quickly to consume HF, reducing the risk of HF contacting with phosphate particles, and further enhancing the service reliability and cycle performance of the battery cell, etc.

[0009] In some embodiments, the volume average particle size D v 50 of the first particles is from 50 nm to 20 μm, and optionally from 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, improving the overall tap density of the cathode active material.

[0010] In some embodiments, the volume average particle size D v 50 of the vanadium oxide particles is from 20 nm to 100 nm; the volume average particle size D v 50 of the first particles is from 0.3 μm to 5 μm. 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 voids formed by the accumulation of multiple first particles, thereby improving the tap density of the cathode active material, and thus enhancing the energy density of the battery cell.

[0011] In some embodiments, the volume average particle size D v 50 of the vanadium oxide particles is from 0.5 μm to 20 μm; the volume average particle size D v 50 of the first particles is from 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 voids formed by the accumulation of multiple vanadium oxide particles, thereby improving the tap density of the cathode active material, and thus enhancing the energy density of the battery cell.

[0012] In some embodiments, 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%. When the mass content of the vanadium oxide particles is within the above range, they can fully react with HF in the battery cell, reduce the content of HF, and significantly improve the performance of the battery cell; moreover, the vanadium oxide particles can be combined with the first particles to increase the powder compaction density, which is beneficial to improving the energy density of the battery cell.

[0013] In some embodiments, 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%. When the mass content of the first particles is within the above range, they can act together with the vanadium oxide particles to increase the powder compaction density while improving the specific capacity and structural stability of the positive electrode active material.

[0014] In some embodiments, the phosphate particles include a compound with the molecular formula Li 1+x Mn 1-y A y P 1-z R z Y w where -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. When the above phosphate particles are used in combination with the vanadium oxide particles, the cycle stability of the positive electrode active material can be effectively improved.

[0015] 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.

[0016] In some embodiments, based on the total mass of the first particles, the mass content of the carbon layer is 0.05% to 6%. When the mass content of the carbon layer is within the above range, it can form a good coating effect on the phosphate particles, effectively reduce the risk of side reactions caused by direct contact between the phosphate particles and the electrolyte, reduce the risk of transition metal ion dissolution, and is beneficial to improving the cycle performance and storage performance of the positive electrode active material; moreover, when the mass content of the carbon layer is within the above range, it can effectively improve the overall conductivity of the positive electrode active material, which is beneficial to the performance of the specific capacity of the phosphate particles.

[0017] In some embodiments, the tap density of the positive electrode active material powder is 2.25 g / cm 3 to 2.60 g / cm 3 . When the tap density of the positive electrode active material powder is within the above range, the energy density of the battery cell can be effectively improved.

[0018] Second, embodiments of the present application provide a method for preparing a positive electrode active material, including:

[0019] Providing an organic carbon source to phosphate particles;

[0020] Carrying out carbonization treatment on the organic carbon source to form a carbon layer on at least a part of the surface of the phosphate particles, obtaining first particles;

[0021] Mixing vanadium oxide particles and the first particles to obtain the positive electrode active material.

[0022] Third, embodiments of the present application provide a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector. The positive electrode film layer includes the positive electrode active material according to any one of the embodiments of the first aspect of the present application, or the positive electrode active material prepared by the method according to any one of the embodiments of the second aspect of the present application.

[0023] Fourth, the present application also provides a battery, which includes the positive electrode sheet according to any one of the embodiments of the third aspect of the present application.

[0024] Fifth, the present application also provides an electrical device, which includes the battery according to any one of the embodiments of the fourth aspect of the present application. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the drawings.

[0026] Figure 1 is a schematic diagram of an embodiment of the battery cell of the present application.

[0027] Figure 2 is Figure 1 an exploded schematic diagram of the embodiment of the battery cell.

[0028] Figure 3 is a schematic diagram of an embodiment of the battery module of the present application.

[0029] Figure 4 is a schematic diagram of an embodiment of the battery pack of the present application.

[0030] Figure 5 is Figure 4 An exploded schematic view of an embodiment of the battery pack shown.

[0031] Figure 6 is a schematic view of an embodiment of an electrical device including the battery cell of the present application as a power source.

[0032] The drawings are not necessarily drawn to actual scale.

[0033] The reference numerals are explained as follows:

[0034] 1. Battery pack; 2. Upper box body; 3. Lower box body; 4. Battery module;

[0035] 5. Battery cell; 51. Housing; 52. Electrode assembly;

[0036] 53. Cover plate;

[0037] 6. Electrical device. Specific embodiments

[0038] Hereinafter, embodiments of the positive electrode active material, its preparation method, battery, and electrical device of the present application specifically disclosed will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary details are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent 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 recited in the claims.

[0039] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 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 abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0041] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0042] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, a method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0043] Phosphates have a relatively high theoretical specific capacity, which is beneficial to improving the energy density of a single battery cell. However, due to the poor electronic conductivity of phosphates, it is difficult to fully utilize their capacity, which limits their application. In related technologies, in order to improve the capacity utilization of phosphates, phosphate is usually coated and modified, for example, modified with a carbon coating layer. However, further research has found that the electrolyte contains hydrofluoric acid (HF), and serious side reactions may still occur between HF and phosphates with a carbon coating layer, resulting in the dissolution of transition metal ions in phosphates, such as manganese ions. The dissolved manganese ions migrating to the surface of the negative electrode may be reduced to metallic manganese, and metallic manganese can catalyze the decomposition of the solid electrolyte interphase (SEI) film on the surface of the negative electrode. Part of the by-products of the decomposition are gases, causing the battery to expand and affecting the reliability of the single battery cell. The other part of the by-products is deposited on the surface of the negative electrode, blocking the channels for lithium ions to enter and exit the negative electrode, resulting in an increase in the impedance of the single battery cell and affecting the kinetic performance of the single 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 have an irreversible impact on the capacity retention rate of the battery and deteriorate the cycle performance.

[0044] In view of the above problems, the embodiments of the present application propose 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, and the carbon layer plays a role in coating the phosphate particle, which can improve the capacity utilization of the phosphate particle. Since the vanadium oxide particle includes a vanadium oxide particle, it can react with HF, alleviate the side reaction between the phosphate particle and HF, and reduce the dissolution of transition metal ions. Moreover, the vanadium ions in the vanadium oxide particle 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, kinetic performance, and cycle performance of the single battery cell.

[0045] Next, the technical solutions of the embodiments of the present application will be described in detail.

[0046] Positive electrode active material

[0047] In a first aspect, the embodiments of the present application provide a positive electrode active material.

[0048] The positive electrode active material includes a first particle and a vanadium oxide particle, and the first particle includes a phosphate particle and a carbon layer disposed on at least a part of the surface of the phosphate particle.

[0049] The carbon layer is disposed on at least a part of the surface of the phosphate particles, which can play a good coating and protection role for the phosphate particles; since the carbon layer contains elemental carbon and has excellent electronic conductivity, it is beneficial to improve the overall conductivity of the positive electrode active material and contribute to the capacity performance of the phosphate particles.

[0050] The vanadium oxide particles can reduce the risk of side reactions occurring due to the direct contact between the phosphate particles and the electrolyte; 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 being able to reduce the dissolution of transition metal ions such as manganese ions in the phosphate particles and being beneficial to improving the stability of the structure of the phosphate particles; in addition, since the vanadium ions in the vanadium oxide particles can diffuse to the surface of the negative electrode sheet to participate in the formation of the SEI film, improving the stability of the SEI film, constructing a more stable interface between the electrolyte and the negative electrode sheet, slowing down the decomposition of the electrolyte on the surface of the negative electrode sheet, and reducing the gas generation amount and the impedance in the battery system, thereby being able to improve the usage reliability, kinetic performance, and cycle performance of the battery cell.

[0051] In some embodiments, the vanadium oxide particles include V 2 O 5 、V 2 O 4 、V 2 O 3 、VO、V a M b O c at least one of them, where M is a transition metal element, 0 < a ≤ 5, 0 < b ≤ 5, 0 < c ≤ 5; the above vanadium oxide particles can react with HF quickly, reducing the risk of side reactions between HF and the phosphate particles.

[0052] Optionally, M includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge.

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

[0054] Exemplarily, b can be 1, 2, 3, 4, 5 or a range composed of any two of the above values.

[0055] Exemplarily, c can be 1, 2, 3, 4, 5 or a range composed of any two of the above values.

[0056] Exemplarily, V a M b O c can include VFe 2 O 5 、V 2 TiO4 、VMgO 3 at least one of

[0057] In some embodiments, the volume average particle size D v 50 of the vanadium oxide particles is 20 nm to 100 μm, optionally 20 nm to 20 μm. When the volume average particle size of the vanadium oxide particles is in the above range, it is beneficial to match with the first particles, improve the tap density of the positive electrode active material, and thus improve the energy density of the battery cell. Moreover, when the volume average particle size of the vanadium oxide particles is in the above range, the contact area between the vanadium oxide particles and the electrolyte is relatively large, which is beneficial to the vanadium oxide reacting with the electrolyte quickly to consume HF, reducing the risk of HF contacting the phosphate particles, and thus further improving the service reliability and cycle performance of the battery cell, etc.

[0058] Exemplarily, the volume average particle size D v 50 of the vanadium oxide particles is 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 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, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 68 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm or a range composed of any two of the above values.

[0059] In some embodiments, the volume average particle size D v 50 of the first particles is 50 nm to 20 μm, optionally 50 nm to 5 μm. When the volume average particle size of the first particles is in the above range, it is beneficial to match with the vanadium oxide particles and improve the overall tap density of the positive electrode active material.

[0060] Exemplarily, 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 composed of any two of the above values.

[0061] Optionally, the volume average particle size D v 50 of the vanadium oxide particles is 20 nm to 100 nm; the volume average particle size D vThe volume average particle size D50 of the vanadium oxide particles is from 0.3 μm to 5 μm. When the volume average particle size of the vanadium oxide particles is within the above range and relatively small at the nanometer level, the vanadium oxide particles can be filled in the voids formed by the stacking of multiple first particles, thereby improving the tap density of the positive electrode active material and thus being able to improve the energy density of the battery cell.

[0062] Optionally, the volume average particle size D50 of the vanadium oxide particles v is from 0.5 μm to 20 μm; the volume average particle size D50 of the first particles v is from 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 are filled in the voids formed by the stacking of multiple vanadium oxide particles, thereby improving the tap density of the positive electrode active material and thus being able to improve the energy density of the battery cell.

[0063] In the embodiments of the present application, the volume average particle size D50 of the particles v refers to the particle size corresponding to 50% in the volume distribution. It can be detected by using equipment and methods well-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 fully discharging the fresh battery cell to a 0% state of charge (SOC), the positive electrode plate 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, and the positive electrode active material is retained. After drying the positive electrode active material, according to the test standard GB / T 19077-2016, the volume average particle size Dv50 of the particles is tested by a Mastersizer 2000E laser particle size analyzer. In the embodiments of the present application, the fresh battery cell can be a battery cell just out of the factory (not subjected to charge and discharge cycles after formation), or a battery cell assembled on an electrical device and with less than 10 charge and discharge cycles.

[0064] In some embodiments, based on the total mass of the positive electrode active material, the mass content of the vanadium oxide particles is from 0.05% to 5.00%; optionally from 1% to 3.5%. When the mass content of the vanadium oxide particles is within the above range, it can fully react with HF in the battery cell, reduce the content of HF, and significantly improve the performance of the battery cell; moreover, the vanadium oxide particles can be combined with the first particles to improve the tap density of the powder, which is beneficial to improving the energy density of the battery cell.

[0065] Exemplarily, 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%, 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 composed of any two of the above values.

[0066] In some embodiments, 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%. When the mass content of the first particles is within the above range, it can act together with the vanadium oxide particles to improve the powder compaction density while enhancing the specific capacity performance and structural stability of the positive electrode active material.

[0067] Exemplarily, 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 composed of any two of the above values.

[0068] The phosphate particles may include the element 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 the above range, the vanadium oxide particles can significantly reduce the risk of Mn dissolution and further enhance the structural stability of the phosphate particles.

[0069] Exemplarily, the molar ratio of V to Mn in the positive electrode active material can 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, 0.040:1, 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 composed of any two of the above values.

[0070] In some embodiments, the phosphate particles include a compound with the molecular formula Li 1+x Mn 1-y A y P 1-z R z Y w , where -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. When the above phosphate particles are used in combination with vanadium oxide particles, the cycle stability of the positive electrode active material can be effectively improved.

[0071] Exemplarily, 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 formed by any two of the above values.

[0072] Exemplarily, 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, 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 formed by any two of the above values. Optionally, 0.3 ≤ y ≤ 0.6.

[0073] Exemplarily, 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 formed by any two of the above values.

[0074] Exemplarily, 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 formed by any two of the above values.

[0075] Exemplarily, 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

[0076] During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell discharges to different states. In the enumeration of the positive electrode active material in the embodiments of the present application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change.

[0077] In the enumeration of the positive electrode active material in the embodiments of the present application, the molar content of oxygen O is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will fluctuate.

[0078] In some embodiments, based on the total mass of the first particles, the mass content of the carbon layer is greater than 0 and less than or equal to 6%, optionally 2% to 5%. When the mass content of the carbon layer is within the above range, a good coating effect can be formed on the phosphate particles, the risk of side reactions occurring due to direct contact between the phosphate particles and the electrolyte can be effectively reduced, the risk of transition metal ion dissolution is reduced, which is beneficial to the improvement of the cycling performance and storage performance of the positive electrode active material; moreover, when the mass content of the carbon layer is within the above range, the conductivity of the overall positive electrode active material can be effectively improved, which is beneficial to the exertion of the specific capacity of the phosphate particles.

[0079] Exemplarily, 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 the range composed of any two of the above values.

[0080] In some embodiments, the powder tap density of the positive electrode active material is 2.25 g / cm 3 to 2.60 g / cm 3 , for example, 2.25 g / cm 3 , 2.28 g / cm 3 , 2.30 g / cm 3 , 2.31 g / cm 3 , 2.33 g / cm 3 , 2.35 g / cm 3 , 2.38 g / cm 3 , 2.39 g / cm 3 , 2.4 g / cm 3 , 2.5 g / cm 3 , 2.6 g / cm 3 or the range composed of any two of the above values. When the powder tap density of the positive electrode active material is within the above range, the energy density of the battery cell can be effectively improved.

[0081] In the embodiments of the present application, the powder tap density of the positive electrode active material has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, a certain amount of the positive electrode active material sample prepared above is taken and added to a mold with a bottom area of 1.327 cm 2 in a UTM7305 type electronic pressure testing machine, pressurized to 2000 kg (equivalent to 20000 N), kept under pressure for 30 s, then depressurized, kept for 10 s, and then the powder tap density of the negative electrode active material under the action of 20000 N is recorded and calculated. The test standard is based on GB / T24533-2009.

[0082] Method for preparing positive electrode active material

[0083] In a second aspect, the embodiments of the present application also propose a method for preparing a positive electrode active material. The positive electrode active material of any one of the embodiments in 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 means commonly used in the art.

[0084] The method includes:

[0085] Step S100: Provide an organic carbon source to the phosphate particles;

[0086] Step S200: Carbonize the organic carbon source to form a carbon layer on at least part of the surface of the phosphate particles to obtain first particles;

[0087] Step S300: Mix the vanadium oxide particles and the first particles to obtain the positive electrode active material.

[0088] According to the method of the embodiments of the present application, after the organic carbon source is carbonized, a carbon layer can be formed on the surface of the phosphate particles to form first particles; further, the first particles and the vanadium oxide particles are mixed. 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 and being beneficial to improving the structural stability of the phosphate particles; in addition, since 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, improving the stability of the SEI film, constructing a more stable interface between the electrolyte and the negative electrode plate, slowing down the decomposition of the electrolyte on the surface of the negative electrode plate, reducing the gas generation amount and the impedance in the battery system, and thus improving the use reliability, kinetic performance and cycle performance of the battery cell.

[0089] [Step S100]

[0090] The organic carbon source may be solid particles. The solid organic carbon source can be dissolved in a solvent, and then the organic carbon source dissolved in the solvent and the phosphate particles are mixed. The solvent can be deionized water or the like.

[0091] The phosphate particles may include a compound with the molecular formula Li 1+x Mn 1-y A y P 1-z R z Y w , and the phosphate particles may be commercially available or obtained by synthesis according to the following method.

[0092] In some embodiments, the method for preparing phosphate particles includes:

[0093] Step S110: Dissolve a manganese source and an A source in a solvent, and obtain a metal precursor through drying treatment;

[0094] Step S120: Add the metal precursor, a lithium source, a phosphorus source, and an R source into a solvent, grind and mix them, and then perform spray drying treatment to obtain a phosphate precursor;

[0095] Step S130: Sinter the phosphate precursor to form phosphate particles.

[0096] In step S110,

[0097] In some embodiments, the manganese source may be a manganese-containing substance known in the art and usable for preparing phosphates. For example, the manganese source may include at least one of elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, and manganese carbonate.

[0098] In some embodiments, the A source may include at least one of oxalates, phosphates, acetates, sulfates, citrates, and nitrates.

[0099] In some embodiments, the solvent may include at least one of deionized water and alcohols.

[0100] In step S120,

[0101] 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.

[0102] In some embodiments, the phosphorus source may include at least one of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0103] 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; taking a silicon source as an example, the silicon source may include at least one of silicic acid, metasilicic acid, silicon tetrachloride, silicon dioxide, and tetraethyl orthosilicate. Taking a boron source as an example, the boron source may include at least one of boric acid, ammonium borate, and boron oxide.

[0104] In some embodiments, the solvent may include at least one of deionized water and alcohols.

[0105] In some embodiments, the grinding can be carried out using a sand mill, for example, grinding and stirring in a sand mill for 8 h to 10 h.

[0106] In some embodiments, the process of spray drying granulation can be carried out at 230 °C to 270 °C for 3.5 h to 5 h.

[0107] In step S130,

[0108] The sintering treatment can be carried out in an inert atmosphere, and the inert atmosphere can adopt at least one of nitrogen and argon.

[0109] The sintering temperature can be 650 °C to 750 °C, and the sintering time can be 8 h to 12 h.

[0110] The stoichiometric ratios of the various substances in the above steps can be set according to the chemical formula of the required phosphate particles. The contents of the various elements in the material can be detected by inductively coupled plasma emission spectroscopy (ICP).

[0111] In some embodiments, the organic carbon source may include at least one of saccharide compounds, olefin polymers, polyvinyl alcohol, polyethylene glycol, citric acid, and toluene.

[0112] Exemplarily, the saccharide compound may include at least one of starch, sucrose, and glucose.

[0113] Exemplarily, the olefin polymer may include at least one of polyethylene and polytetrafluoroethylene.

[0114] The above substances can be selected as organic carbon sources such as polyethylene, polytetrafluoroethylene, and toluene. The above substances have relatively low hydroxyl contents, and even no hydroxyl groups. The amount of residual hydroxyl groups after carbonization is relatively small, which is beneficial to improving the electrochemical performance of the cathode active material.

[0115] [Step S200]

[0116] In the process of step S100 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 h to 6 h, the system is subjected to a carbonization treatment; the carbonization treatment process is as follows: the system can be pre-treated at 120 °C to 200 °C for heat treatment and drying for 4 h to 6 h to remove the solvent; then sintered at 650 °C to 750 °C for 8 h to 12 h, and the organic carbon source is carbonized into a carbon layer, and the carbon layer coats at least part of the surface of the phosphate particles.

[0117] [Step S300]

[0118] The first particles and vanadium oxide particles can be mixed and stirred evenly to obtain the positive electrode active material. The vanadium oxide basically does not undergo a chemical reaction before and after mixing.

[0119] In some embodiments, the vanadium oxide particles include V 2 O 5 、V 2 O 4 、V 2 O 3 、VO, V a M b O c and at least one of them, where M is a transition metal element, 0 < a ≤ 5, 0 < b ≤ 5, 0 < c ≤ 5; the above vanadium oxide particles can react with HF quickly, reducing the risk of side reactions between HF and phosphate particles.

[0120] Optionally, M includes one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge.

[0121] Positive electrode sheet

[0122] In a third aspect, an embodiment of the present application provides a positive electrode tab.

[0123] The positive electrode tab 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 including the positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0124] 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 enhancing the electrochemical performance of the positive electrode tab; in addition, since the side reaction between the positive electrode active material and the electrolyte is alleviated, when the positive electrode tab is applied to a battery cell, the expansion rate of the battery cell can be reduced, and the service reliability, kinetic performance, and cycle performance of the battery cell can be improved.

[0125] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. There is no particular limitation on the type of the positive electrode conductive agent in the embodiments of the present application. As an example, the positive electrode conductive agent includes 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, based on the total mass of the positive electrode film layer, the mass percentage content of the positive electrode conductive agent is ≤5%.

[0126] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. There is no particular limitation on the type of the positive electrode binder in the embodiments of the present application. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage content of the positive electrode binder is ≤5%.

[0127] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the 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).

[0128] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive electrode current collector and then drying and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0129] Single battery

[0130] Fourthly, embodiments of the present application also propose a battery cell. The battery cell includes a positive electrode tab as in any one of the embodiments of the third aspect of the present application. Since the positive electrode active material in the positive electrode tab has good conductivity, its capacity utilization is improved, and the electrochemical performance of the positive electrode tab is improved; in addition, since the side reaction between the positive electrode active material and the electrolyte is alleviated, when the positive electrode tab is applied to the battery cell, the expansion rate of the battery cell can be reduced, and the use reliability, kinetic performance, and cycle performance of the battery cell can be improved.

[0131] Negative electrode sheet

[0132] In some embodiments, the battery cell further includes a negative electrode sheet.

[0133] 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 including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0134] The negative electrode active material can be a negative electrode active material known in the art for battery cells. As an example, the negative electrode active material can 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. The silicon-based materials can include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloy materials. The tin-based materials can include at least one of elemental tin, tin oxides, and tin alloy materials.

[0135] In some embodiments, the negative electrode film layer may optionally further include a negative electrode conductive agent. The embodiments of the present application do not particularly limit the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent can 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, based on the total weight of the negative electrode film layer, the mass percentage content of the negative electrode conductive agent is ≤5 wt%.

[0136] In some embodiments, the negative electrode film layer may optionally further include a negative electrode binder. The embodiments of the present application do not particularly limit the type of the negative electrode binder. As an example, the negative electrode binder can include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage content of the negative electrode binder is ≤5 wt%.

[0137] In some embodiments, the negative electrode film layer may optionally further include other additives. As an example, the other additives can include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage content of the other additives is ≤2 wt%.

[0138] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of the 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, copper 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).

[0139] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative electrode current collector and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing negative electrode active materials, optional conductive agents, optional binders, and other optional additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0140] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application embodiment further includes a conductive bottom coating (e.g., composed of a conductive agent and a binder) disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer. In some other embodiments, the negative electrode plate of the present application embodiment further includes a protective layer covering the surface of the negative electrode film layer.

[0141] [Electrolyte solution]

[0142] In some embodiments, the battery cell further includes an electrolyte solution.

[0143] During the charge and discharge process of the battery cell, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte solution plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The type of the electrolyte solution in the present application embodiment is not particularly limited and can be selected according to actual needs.

[0144] The electrolyte solution includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.

[0145] As an example, the electrolyte salt may include but is not limited to lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6)、Lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), at least one of lithium difluoro(dioxalato)phosphate (LiDFOP) and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0146] 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).

[0147] In some embodiments, the electrolyte may also optionally include additives. For example, the additives may include anode film-forming additives, may also include cathode film-forming additives, and may also include additives that can improve certain battery performance, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, additives for improving the low-temperature power performance of the battery, etc.

[0148] [Separator]

[0149] The battery cell further includes a separator.

[0150] In some embodiments, the battery cell also includes a separator. The embodiments of the present application do not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0151] 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 can 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 can be the same or different, without particular limitation.

[0152] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly by a winding process and / or a stacking process.

[0153] In some embodiments, the battery cell may include an outer package. The outer package may be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0154] In some embodiments, the outer package of the battery cell may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package of the battery cell may also be a soft package, such as a pouch-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0155] The embodiments of the present application do not particularly limit the shape of the battery cell, which may be cylindrical, square, or any other shape. As Figure 1 is a battery cell 5 with a square structure as an example.

[0156] In some embodiments, as Figure 2 shown, the outer package may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator may form an electrode assembly 52 through a winding process and / or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 may be one or more, which can be adjusted according to requirements.

[0157] The preparation method of the battery cell according to the embodiments of the present application is well-known. In some embodiments, the positive electrode plate, the separator, the negative electrode plate, and the electrolyte may be assembled to form a battery cell. As an example, the positive electrode plate, the separator, and the negative electrode plate may form an electrode assembly through a winding process and / or a stacking process, the electrode assembly is placed in the outer package, dried and then injected with electrolyte, and after processes such as vacuum packaging, standing, forming, and shaping, a battery cell is obtained.

[0158] In some embodiments of the embodiments of the present application, the battery cells according to the embodiments of the present application may be assembled into a battery module. The number of battery cells included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0159] Figure 3 is a schematic diagram of a battery module 4 as an example. As Figure 3 shown, in the battery module 4, multiple battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the multiple battery cells 5 may be fixed by fasteners.

[0160] Optionally, the battery module 4 may further include a housing having an accommodation space, and a plurality of battery cells 5 are accommodated in the accommodation space.

[0161] In some embodiments, the above battery module may also be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0162] Figure 4 and Figure 5 are schematic diagrams of a battery pack 1 as an example. As Figure 4 and Figure 5 shown, the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0163] Electrical device

[0164] The 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 may be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may 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.

[0165] The electrical device may select battery cells, battery modules or battery packs according to its usage requirements.

[0166] Figure 6 are schematic diagrams of an electrical device 6 as an example. The electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 6 for high power and high energy density, a battery pack or a battery module may be adopted.

[0167] Another example of the electrical device may be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires thinness and lightness, and a battery cell may be used as the power source.

[0168] Example

[0169] The following embodiments more specifically describe the content disclosed in the embodiments of the present application. These embodiments are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the embodiments are all commercially available.

[0170] Example 1

[0171] 1. Preparation of the positive electrode sheet

[0172] The positive electrode sheet includes a positive current collector aluminum foil and a positive electrode film layer. The positive electrode film layer is formed by uniformly coating a positive electrode slurry (solvent: N-methylpyrrolidone NMP) on the surface of the positive current collector aluminum foil, followed by drying and cold pressing. The positive electrode film layer includes a positive active material, a binder polyvinylidene fluoride (PVDF), and acetylene black with a weight ratio of 90:5:5.

[0173] The positive 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 compound with the molecular formula Li 0.994 Mn 0.65 Fe 0.35 Mo 0.001 P 0.999 Si 0.001 O 3.99 9 F 0.001 . The preparation process of the positive active material is as follows:

[0174] Dissolve sucrose in 500 ml of deionized water, then stir and dissolve it fully to obtain a coating solution. Add the phosphate particles to the coating solution, stir and mix them together for 6 hours. After mixing evenly, transfer them to an oven at 150 °C and dry for 6 hours, and then sinter at 700 °C for 10 hours to obtain the first particles;

[0175] Place 100 g of the first particles in a closed reaction chamber, stir and mix them with the vanadium oxide particles, and obtain the final positive active material after reacting for 0.5 h.

[0176] 2. Preparation of the negative electrode sheet

[0177] The negative electrode plate includes a negative current collector copper foil and a negative electrode film layer. The negative electrode film layer is formed by uniformly coating the surface of the negative current collector copper foil with a negative electrode slurry (the solvent is deionized water) and then drying and cold pressing. The negative electrode film layer includes a negative electrode active material, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) with a weight ratio of 95:2:2:1.

[0178] The negative electrode active material includes artificial graphite and hard carbon (mass ratio 90:5).

[0179] 3. Separator

[0180] The separator is a polyethylene film.

[0181] 4. Preparation of electrolyte

[0182] The electrolyte includes organic solvents, lithium salts, and additives. The organic solvents include ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) with a volume ratio of 1:1:1. The lithium salt includes 1 mol / L of LiPF 6 .

[0183] 5. Preparation of battery

[0184] The lithium-ion battery includes an outer packaging case, an electrode assembly, and an electrolyte. The electrode assembly and the electrolyte are disposed inside the outer packaging case. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The electrode assembly is a wound electrode assembly, and the separator is disposed between the positive electrode plate and the negative electrode plate.

[0185] Comparative Example 1

[0186] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 is that the positive electrode plate was prepared using the following steps:

[0187] The positive electrode plate includes a positive current collector aluminum foil and a positive electrode film layer. The positive electrode film layer is formed by uniformly coating the surface of the positive current collector aluminum foil with a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) and then drying and cold pressing. The positive electrode film layer includes a positive electrode active material, binder polyvinylidene fluoride (PVDF), and acetylene black with a weight ratio of 90:5:5.

[0188] The positive electrode active material includes phosphate particles and a carbon layer. The phosphate particles include a compound with the molecular formula Li 0.994 Mn 0.65 Fe 0.35 Mo 0.001 P 0.999 Si 0.001 O 3.999 F 0.001 of the compound. The preparation process of the positive electrode active material is as follows:

[0189] 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 phosphate particles into the coating solution, stir and mix together for 6 hours. After mixing evenly, transfer it to an oven at 150 °C and dry for 6 hours, and then sinter at 700 °C for 10 hours to obtain the positive electrode active material.

[0190] Examples 2-1 to 2-4

[0191] Prepare a lithium-ion battery by a method similar to that of Example 1. Different from Example 1, the content of vanadium oxide is adjusted.

[0192] Examples 3-1 to 3-3

[0193] Prepare a lithium-ion battery by a method similar to that of Example 1. Different from Example 1, the type of vanadium oxide is adjusted.

[0194] Examples 4-1 to 4-7

[0195] Prepare a lithium-ion battery by a method similar to that of Example 1. Different from Example 1, at least one of the particle size of vanadium oxide and the particle size of the first particle is adjusted.

[0196] Examples 5-1 and 5-2

[0197] Prepare a lithium-ion battery by a method similar to that of Example 1. Different from Example 1, the material of the positive electrode active material is adjusted.

[0198] In Example 5-1, the positive electrode active material includes a first particle and vanadium oxide particles. The first particle includes phosphate particles and a carbon layer provided on the surface of the phosphate particles. The phosphate particles include a compound with the molecular formula Li 0.994 Mn 0.5 Fe 0.5 Mo 0.00 1 P 0.999 Si 0.001 O 3.999 F 0.001 .

[0199] In Example 5-2, the positive electrode active material includes a first particle and vanadium oxide particles. The first particle includes phosphate particles and a carbon layer provided on the surface of the phosphate particles. The phosphate particles include a compound with the molecular formula Li 0.994 Mn 0.4 Fe 0.6 Mo 0.00 1 P 0.999 Si 0.001 O 3.999 F0.001 compounds

[0200] Examples 6-1 and 6-2

[0201] 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.

[0202] Performance test

[0203] 1. Preparation of Button Cell

[0204] The positive electrode sheet in Example 1 was used as the positive electrode sheet of the button cell;

[0205] A lithium sheet was used as the negative electrode, and the electrolyte included 1 mol / L of LiPF 6 and an organic solvent. The organic solvent included ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1;

[0206] It was assembled into a button cell with the negative electrode sheet, positive electrode sheet, and electrolyte in a button cell box.

[0207] 2. Measurement Method for Initial Specific Capacity of Button Cell

[0208] In a constant temperature environment of 25 °C, the button cell was charged to 4.3 V at 0.1 C, then charged at a constant voltage of 4.3 V until the current was less than or equal to 0.05 mA, allowed to stand for 5 minutes, and then discharged to 2.0 V at 0.1 C. The discharge capacity at this time was the initial specific capacity, denoted as D0.

[0209] 3. Cycling Performance Test of Lithium-Ion Battery at 45 °C

[0210] In a constant temperature environment of 45 °C, the lithium-ion battery was charged to 4.3 V at 1 C, then charged at a constant voltage of 4.3 V until the current was less than or equal to 0.05 mA. After standing for 5 minutes, it was discharged to 2.5 V at 1 C, and the discharge capacity at this time was recorded as E 0 . The above charge-discharge cycle was repeated until the discharge capacity decreased to 80% of E 0 . The number of cycles passed by the lithium-ion battery at this time was recorded.

[0211] 4. Measurement Method for Dissolution Amount of Mn (and Fe Doped at Mn Site) after Cycling of Lithium-Ion Battery

[0212] At 45 °C, the lithium-ion battery after cycling to a capacity decay of 80% was discharged to the cut-off voltage of 2.0 V at a rate of 0.1 C.

[0213] Then disassemble the lithium-ion battery, take out the negative electrode sheet, and randomly take 30 circular pieces with a unit area of 1540.25 mm 2 ) on the negative electrode sheet, and test the inductively coupled plasma emission spectrum (ICP) with an Agilent ICP-OES730. Calculate the amounts of Fe (if Fe is doped at the Mn site of the positive electrode active material) and Mn based on the ICP results, and thus calculate the dissolution amount of Mn (and Fe doped at the Mn site) after cycling. The test standard is based on EPA-6010D-2014.

[0214] 5. Gas swelling test of lithium-ion battery at 60 °C

[0215] Store lithium-ion batteries with a 100% charged state (SOC) at 60 °C as test samples, and measure the open circuit voltage (OCV) and AC internal resistance (IMP) of the lithium-ion batteries before, during, and after storage to monitor the SOC, and measure the volume of the lithium-ion batteries.

[0216] After storing for every 48 hours, take out the lithium-ion battery, let it stand for 1 hour, then test the open circuit voltage (OCV) and internal resistance (IMP), and measure the battery volume by the drainage method after cooling to room temperature. The drainage method is to first measure the gravity F1 of the battery alone with a balance that automatically performs unit conversion of the dial data, then place the lithium-ion battery completely in deionized water (with a known density of 1 g / cm3), and measure the gravity F2 of the battery at this time. The buoyancy F_float of the battery is F1 - F2. Then, according to Archimedes' principle F_float = ρ × g × V_drain, calculate the battery volume V = (F1 - F2) / (ρ × g).

[0217] Judging from the test results of OCV and IMP, during this test process until the end of storage, the batteries of the examples always maintained an SOC of more than 99%.

[0218] After storing for 30 days, measure the battery volume and calculate the percentage increase in the battery volume after storage relative to the battery volume before storage.

[0219] Test result

[0220] The test results are shown in Table 1 and Table 2.

[0221] Table 1

[0222]

[0223] In Table 1,

[0224] The mass content of vanadium oxide particles is calculated based on the total mass of the positive electrode active material.

[0225] The mass content of the first particles is calculated based on the total mass of the positive electrode active material.

[0226] The mass content of the carbon layer is calculated based on the total mass of the first particles.

[0227] Table 2

[0228]

[0229] As can be seen from Table 1 and Table 2,

[0230] In Comparative Example 1, although the lithium iron phosphate particles were coated and modified with a carbon layer, the modified material still had the risk of side reactions with the electrolyte, resulting in relatively poor performance of the lithium-ion battery.

[0231] In the examples of the present application, the positive active material includes first particles and vanadium oxide particles. The vanadium oxide particles 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 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 service reliability, kinetic performance, and cycle performance of the lithium-ion battery. And in the examples of the present application, the dissolution amounts of Fe and Mn after cycling are less than or equal to 352 ppm. The specific capacity of the positive active material in the coin cell in the examples of the present application is 140 mAh / g to 150 mAh / g.

[0232] Examples 2-1 to 2-4 and Examples 3-1 to 3-3 respectively regulate the addition amount and material of the vanadium oxide, which can further optimize the performance of the lithium-ion battery. Examples 4-1 to 4-7 can further improve the performance of the lithium-ion battery by optimizing the particle size matching of the vanadium oxide particles and the first particles. Examples 5-1 and 5-2 regulate the material of the phosphate, which can further optimize the performance of the lithium-ion battery. Examples 6-1 and 6-2 regulate the addition amount of the carbon layer, which can further optimize the performance of the first particles and improve the performance of the lithium-ion battery.

[0233] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be construed as limitations on the present application, and the embodiments can be changed, substituted, and modified without departing from the spirit, principle, 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 part of the surface of the phosphate particles.

2. The positive electrode active material according to claim 1, wherein, The vanadium oxide particles include V 2 O 5 , V 2 O 4 , V 2 O 3 , VO, V a M b O c and at least one of them, where M is a transition metal element, 0 < a ≤ 5, 0 < b ≤ 5, 0 < c ≤ 5; optionally, M comprises one or more elements selected from 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 from 20 nm to 100 μm, optionally from 20 nm to 20 μm; and / or The volume average particle size D of the first particles v is from 50 nm to 20 μm, and optionally from 50 nm to 5 μm; optionally, The volume average particle size D of the vanadium oxide particles v 50 is 20 nm to 100 nm; the volume average particle size D of the first particles v 50 is 0.3 μm to 5 μm; optionally, The volume average particle size D of the vanadium oxide particles v 50 is from 0.5 μm to 20 μm; the volume average particle size D v 50 of the first particles is from 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 compound with the molecular formula Li 1+x Mn 1-y A y P 1-z R z Y w , where -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, based on the total mass of the first particles, the mass content of the carbon layer is 0.05% to 6%.

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

9. A method for preparing a positive electrode active material, comprising: providing an organic carbon source to phosphate particles; carbonizing the organic carbon source to form a carbon layer on at least a part of the surface of the phosphate particles to obtain first particles; mixing vanadium oxide particles and the first particles to obtain a positive electrode active material.

10. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed 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, it comprises the positive electrode sheet according to claim 10.

12. An electrical device, characterized in that, it comprises the battery according to claim 11.

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