Positive electrode active material and preparation method thereof, positive plate, battery, battery pack and electric equipment

Abstract

The embodiment of the invention provides a positive active material and a preparation method thereof, a positive plate, a battery, a battery pack and electric equipment. The positive electrode active material comprises a lithium manganese iron phosphate core, the lithium manganese iron phosphate core comprises an element M, and the element M is gradually reduced from the inside to the outside of the lithium manganese iron phosphate core; and the element M comprises one or more of Mg, Zn, Ca, Al, Sr, Co, Ni and Cr. The positive electrode active material disclosed by the embodiment of the invention has relatively good conductivity and stability, and the rate capability and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a positive electrode active material and its preparation method, a positive electrode sheet, a battery, a battery pack, and electrical equipment. Background Technology

[0002] Lithium-ion batteries, as high-energy-density energy storage devices, are widely used in new energy vehicles, energy storage systems, consumer electronics (such as smartphones and laptops), and aerospace. Therefore, LMFP is considered one of the candidates for the next generation of high-energy-density lithium-ion battery cathode materials.

[0003] Lithium iron phosphate (LiFePO4, LFP) has become an important choice for cathode active materials in lithium batteries due to its stable olivine-type structure, long cycle life, high thermal safety, and low cost. However, traditional LFP materials have a low specific capacity (approximately 170 mAh / g) and poor conductivity, limiting their application in high-power demand scenarios. Lithium manganese iron phosphate (LMFP), by introducing Mn (partially replacing Fe), can significantly improve its operating voltage while maintaining structural stability, thereby significantly increasing the battery's energy density. However, the conductivity of LFP materials remains poor, and manganese dissolves during battery cycling, causing the structure of the cathode active material to collapse and deteriorating the battery's cycle life.

[0004] Therefore, there is an urgent need for a lithium manganese iron phosphate material with high conductivity and stability to improve the rate performance and cycle performance of batteries. Summary of the Invention

[0005] This invention provides a positive electrode active material and its preparation method, a positive electrode sheet, a battery, a battery pack, and an electrical device. The positive electrode active material has high conductivity and stability, and can improve the rate performance and cycle performance of the battery.

[0006] This invention provides a positive electrode active material comprising a lithium manganese iron phosphate core, wherein the lithium manganese iron phosphate core includes an element M, and the element M decreases from the center of the lithium manganese iron phosphate core to the outside.

[0007] The element M includes one or more of the following: Mg, Zn, Ca, Al, Sr, Co, Ni, and Cr.

[0008] In some embodiments of the present invention, the lithium manganese iron phosphate core includes LiMn 1-x Fe x M y PO4;

[0009] Where 1-x>0, x>0; y>0.

[0010] In some embodiments of the present invention, the resistivity of the positive electrode active material is 20 Ω·cm to 100 Ω·cm.

[0011] In some embodiments of the present invention, the lithium manganese iron phosphate core further includes a Q element, wherein the Q element includes one or more elements selected from Ti, Zr, V, W, and Nb;

[0012] Wherein, the atomic percentage z of the Q element and the total atomic weight of Fe and Mn elements in the lithium manganese iron phosphate core is 0.1at% ≤ z ≤ 0.5at%;

[0013] And / or, 0.2≤x≤0.7, 0<y≤0.02.

[0014] In some embodiments of the present invention, at least a portion of the surface of the lithium manganese iron phosphate core is provided with a coating layer, the coating layer comprising a carbon material.

[0015] In some embodiments of the present invention, the resistivity of the positive electrode active material is 20 Ω·cm to 100 Ω·cm;

[0016] And / or, the thickness of the coating layer is 1 nm to 10 nm;

[0017] And / or, the coating layer further includes an ion-conducting material dispersed in the carbon material.

[0018] In some embodiments of the present invention, the ion conductor material increases in a direction away from the coating layer and away from the lithium manganese iron phosphate core;

[0019] And / or, the ion conductor material accounts for 1.0 wt% to 2.0 wt% of the mass of the positive electrode active material;

[0020] And / or, the ionic conductor material includes one or more of lithium lanthanum titanate, lithium lanthanum zirconate, lithium titanium aluminum phosphate, and lithium germanium aluminum phosphate;

[0021] And / or, the carbon material accounts for 1.0 wt% to 2.0 wt% of the mass of the positive electrode active material;

[0022] And / or, the carbon material includes one or more of graphite, amorphous carbon, carbon nanotubes, and graphene;

[0023] And / or, the thickness of the coating layer is 3nm~8nm.

[0024] This invention also provides a method for preparing the positive electrode active material as described above, comprising the following steps:

[0025] The positive electrode active material is obtained by sequentially subjecting a raw material system including lithium source, manganese source, iron source, phosphorus source and M source to a first heating reaction and calcination treatment.

[0026] The M source includes one or more elements selected from Mg, Zn, Ca, Al, Sr, Co, Ni, and Cr.

[0027] In some embodiments of the present invention, after the first heating reaction, a second heating reaction is further performed on a second reaction system comprising the product of the first heating reaction and a Q source;

[0028] The second reaction system also includes a coating agent;

[0029] And / or, the second reaction system further includes a precipitant;

[0030] And / or, the raw material system may also include a pH adjuster.

[0031] In some embodiments of the present invention, the coating agent includes at least one of a carbon source and an ion conductor material;

[0032] And / or, the reaction temperature of the first heating reaction is 140℃~170℃, the reaction time is 2h~8h, and the pH is 5.5~6.5;

[0033] And / or, the reaction temperature of the second heating reaction is 170℃~200℃, and the reaction time is 4h~10h;

[0034] And / or, the calcination treatment includes a first calcination treatment and a second calcination treatment, wherein the first calcination treatment has a treatment temperature of 300℃~500℃, a treatment time of 0.5h~3h, and a heating rate of 2℃ / min~10℃ / min; the second calcination treatment has a treatment temperature of 600℃~800℃, and a treatment time of 2h~8h;

[0035] And / or, the pH adjuster includes at least one of ammonia and citric acid;

[0036] And / or, the precipitant includes at least one of urea and hexamethylenetetramine;

[0037] And / or, the ion conductor raw material includes one or more of zirconium citrate, titanium oxalate, zirconium oxynitrate, aluminum sol, and aluminum isopropoxide;

[0038] And / or, the M source includes one or more of magnesium sulfate, magnesium acetate, and zinc sulfate;

[0039] And / or, the Q source includes one or more of ammonium metavanadate, sodium tungstate, niobium oxalate, zirconium oxychloride, and titanium oxysulfate.

[0040] The present invention also provides a positive electrode sheet, comprising the positive electrode active material as described above, or the positive electrode active material prepared by the method described above.

[0041] This invention provides a positive electrode active material and its preparation method, a positive electrode sheet, a battery, a battery pack, and an electrical device. The positive electrode active material uses element M, a low-valence metal element, in its lithium manganese iron phosphate core for doping. The content of element M decreases from the center of the lithium manganese iron phosphate core to the outside, which can stabilize the crystal lattice of the positive electrode active material and make the positive electrode active material have good conductivity, thereby improving the cycle performance and rate performance of the battery. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] Currently, conventional lithium manganese iron phosphate materials have poor conductivity and stability, which can worsen the cycle life of batteries.

[0044] The inventors attempted to coat the surface of LMFP particles with a carbon layer (such as graphene, carbon nanotubes, or amorphous carbon) or an ion-conducting layer (such as Li3PO4 or Al2O3) to improve electronic conductivity, hinder the dissolution of manganese ions, and reduce side reactions in the battery. However, the carbon layer is easily damaged during battery cycling, failing to effectively solve the aforementioned problems.

[0045] Therefore, the inventors aimed to improve the rate performance and cycle performance of the battery by taking into account both the conductivity and stability of lithium manganese iron phosphate material.

[0046] Based on this, embodiments of the present invention provide a positive electrode active material, including a lithium manganese iron phosphate core, the lithium manganese iron phosphate core including an element M, the element M decreasing from the center of the lithium manganese iron phosphate core to the outside; the element M includes one or more elements selected from Mg, Zn, Ca, Al, Sr, Co, Ni, and Cr.

[0047] The positive electrode active material of this invention has high conductivity and stability, which can improve the rate performance and cycle performance of the battery.

[0048] The inventors analyzed that the positive electrode active material of the present invention can improve the rate performance and cycle performance of the battery because: the positive electrode active material of the present invention includes a lithium manganese iron phosphate core, which can give the positive electrode active material a high energy density, which is beneficial to improving the first efficiency of the battery; at the same time, the lithium manganese iron phosphate core of the present invention includes element M, which includes one or more elements selected from Mg, Zn, Ca, Al, Sr, Co, Ni, and Cr. The valence state of the above elements is relatively low, which can stabilize the lattice stability of the lithium manganese iron phosphate core, thereby improving the stability of the positive electrode active material, which is beneficial to improving the first efficiency of the battery, and thus improving the cycle performance of the battery; since the conductivity of the positive electrode active material is worse near the center, in the present invention, the element M decreases from the center of the lithium manganese iron phosphate core to the outside, which can generate vacancies or change its band structure in the lattice of the positive electrode active material, especially in the center of the positive electrode active material, thereby increasing the electron carrier concentration and enhancing the openness of the lithium ion diffusion channel, enhancing the conductivity of the positive electrode active material, and thus improving the rate performance of the battery.

[0049] The embodiments of the present invention can use conventional testing methods and instruments in the art to test the above-described structure and composition of the positive electrode active material, such as EDS and XPS. In specific implementation, the battery can be completely discharged and disassembled to separate the positive electrode sheet. Then, the cross-section of the positive electrode sheet can be obtained using FIB for EDS or XPS testing to obtain the structure and composition of the positive electrode active material.

[0050] In some embodiments of the present invention, the lithium manganese iron phosphate core includes LiMn 1-x Fe x M y PO4; where 1-x>0, x>0; y>0, can further improve the conductivity and stability of the positive electrode active material, thereby better improving the rate performance and cycle performance of the battery.

[0051] In some embodiments of the present invention, the lithium manganese iron phosphate core further includes a Q element, which includes one or more elements selected from Ti, Zr, V, W, and Nb. This can further improve the conductivity and stability of the positive electrode active material, thereby better improving the rate performance and cycle performance of the battery.

[0052] In some embodiments, the atomic percentage z of Q element to the total atomic weight of Fe and Mn in the lithium manganese iron phosphate core is 0.1 at% ≤ z ≤ 0.5 at%, which can further improve the conductivity and stability of the positive electrode active material, thereby better improving the rate performance and cycle performance of the battery. For example, the atomic percentage z of Q element to the total atomic weight of Fe and Mn in the lithium manganese iron phosphate core is, for example, 0.1 at%, 0.2 at%, 0.4 at%, 0.5 at%, or any combination thereof. In the embodiments of the present invention, the atomic percentage z of Q element to the total atomic weight of Fe and Mn in the lithium manganese iron phosphate core can be tested by conventional testing methods and instruments in the art, such as ICP and XPS.

[0053] In some embodiments, 0.2≤x≤0.7 and 0<y≤0.02 can further improve the conductivity and stability of the positive electrode active material, thereby better improving the rate performance and cycle performance of the battery.

[0054] In some embodiments of the present invention, at least a portion of the surface of the lithium manganese iron phosphate core is provided with a coating layer, the coating layer comprising carbon material, which can better improve the conductivity and stability of the battery, thereby further improving the stability and conductivity of the battery.

[0055] In some embodiments of the present invention, when the battery has the above-described structure, the resistivity of the positive electrode active material is 20 Ω·cm to 100 Ω·cm, which can better improve the rate performance and cycle performance of the battery. The resistivity of the positive electrode active material can be tested using conventional testing methods and instruments in the art, for example, it can be measured using a powder resistivity meter. In specific testing, the battery can be completely discharged and disassembled to separate the positive electrode sheet. The positive electrode sheet is then vacuum dried at 50°C to 80°C for 6 to 24 hours to remove residual electrolyte. Subsequently, the dried positive electrode sheet is placed in a solvent (the solvent can be selected according to the type of binder; for example, if the binder is PVDF, the solvent can be anhydrous N-methyl-2-pyrrolidone (NMP)). The solvent is added at a solid-liquid mass-volume ratio of 1g:(10mL to 50mL), and the mixture is stirred at 60°C to 80°C and subjected to ultrasonic treatment for 2 to 6 hours to completely peel off the binder-containing positive electrode active material layer from the aluminum current collector. The resulting suspension is centrifuged or filtered to collect the solid precipitate, and then washed with anhydrous ethanol and acetone 2 to 5 times each to remove NMP and residual binder. The washed mixed powder is redispersed in deionized water or ethanol to prepare a suspension with a concentration of 0.5wt% to 5wt%. Gradient centrifugation is then performed: first, centrifugation at 2000rpm to 4000rpm for 5 to 10 minutes, discarding the supernatant to remove light conductive carbon components; then, centrifugation of the precipitate at 6000rpm to 10000rpm for 10 to 20 minutes, collecting the dense precipitate at the bottom, which mainly consists of the positive electrode active material; repeating the above centrifugation steps 1 to 2 times to improve purity; finally, the obtained precipitate is vacuum dried at 50°C to 70°C for 4 to 12 hours until constant weight, obtaining the positive electrode active material sample for testing. The resistivity of the positive electrode active material can be obtained by performing powder resistivity testing on the sample. Alternatively, the powder resistivity of the positive electrode active material can be directly tested in this embodiment of the invention. Specifically, the positive electrode active material powder of this embodiment can be dried in a vacuum oven at 80°C for 24 hours to completely remove adsorbed water. Weigh 0.5 g of dried powder and place it into a cylindrical PTFE mold with a diameter of 10 mm. Using a hydraulic tablet press, apply an axial pressure of 30 MPa to the powder and hold for 60 seconds to form a dense, disc-shaped preform. Transfer the mold containing the powder preform to a test fixture connected to a digital source meter. Under a constant temperature of 25°C, apply a constant DC current of 10 mA using the four-terminal method, measure the voltage drop across the preform, and calculate the resistance value R. After depressurization, measure the actual thickness L of the preform. Calculate the compacted resistivity ρ of the powder using the formula ρ = R × (πd² / 4) / L. Repeat the test three times for each sample, and take the average value.

[0056] In some embodiments, the thickness of the coating layer is 1 nm to 10 nm, which is beneficial for improving the conductivity of the positive electrode active material and thus improving the rate performance of the battery. For example, the thickness of the coating layer is, for example, a range of 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 10 nm, or any combination thereof. The thickness of the coating layer can be tested using conventional testing methods and instruments in the art, such as SEM. Specifically, the battery can be fully discharged and disassembled to separate the positive electrode sheet. Then, a cross-section of the positive electrode sheet can be obtained using FIB for SEM testing. By statistically analyzing the cross-sections of the positive electrode active material in the field of view, the thickness of the coating layer can be obtained. When the thickness of the coating layer is uneven, the average thickness from multiple fields of view is taken as the thickness of the coating layer.

[0057] In some embodiments, the coating layer further includes an ion-conducting material dispersed in the carbon material, which can better improve the conductivity and stability of the battery, thereby further improving the battery's stability, conductivity and initial efficiency.

[0058] In some embodiments, when the ion conductor material increases in the direction away from the lithium manganese iron phosphate core from the coating layer, the conductivity and stability of the battery can be better improved, thereby further improving the battery's stability, conductivity and initial efficiency.

[0059] In some embodiments, the ionic conductor material accounts for 1.0 wt% to 2.0 wt% of the positive electrode active material by mass, which can better improve the conductivity of the positive electrode active material, and thus better improve its rate performance. For example, the mass percentage of the ionic conductor material in the positive electrode active material is, for example, 1.0 wt%, 1.5 wt%, 2.0 wt%, or any combination thereof. Embodiments of the present invention can be tested using conventional testing methods and instruments in the art, such as inductively coupled plasma mass spectrometry (ICP-MS) to determine the content of [labeled elements, such as La] in the sample, and according to the [ionic conductor chemical formula, such as Li7La3Zr2O]... 12 The stoichiometric ratio was calculated from the chemical composition.

[0060] In some embodiments, the ion conductor material includes one or more of lithium lanthanum titanate, lithium lanthanum zirconate, lithium titanium aluminum phosphate, and lithium germanium aluminum phosphate, which can better improve the conductivity of the positive electrode active material, thereby better improving the rate performance of the battery. Specifically, the specific compositions of lithium lanthanum titanate, lithium lanthanum zirconate, lithium titanium aluminum phosphate, and lithium germanium aluminum phosphate are as follows: LLTO (lithium lanthanum titanate, Li...) 0.33 La 0.56 TiO3), LLZO (lithium lanthanum zirconate, Li7La3Zr2O) 12 LATP (lithium aluminum titanium phosphate, Li1) .3Al 0.3 Ti 1.7 (PO4)3), LAGP (lithium aluminum germanium phosphate, Li 1.5 Al 0.5 Ge 1.5 (PO4)3).

[0061] In some embodiments of the present invention, the mass percentage of carbon material in the positive electrode active material is 1.0 wt% to 2.0 wt%, which is beneficial for further improving the energy density, stability, conductivity, and first-time efficiency of the battery. For example, the mass percentage of carbon material in the positive electrode active material may be 1.0 wt%, 1.5 wt%, 2.0 wt%, or any combination thereof. Embodiments of the present invention can test the mass percentage of carbon material in the positive electrode active material using conventional testing methods and instruments in the art, such as high-frequency combustion-infrared absorption method. Specifically, the following method can be used: Approximately 50 mg of the sample to be tested (the aforementioned positive electrode active material) is accurately weighed, uniformly mixed with 1.5 g of tungsten granule flux, and placed in a ceramic crucible. Under a pure oxygen atmosphere, the sample is burned in a high-frequency induction furnace at a temperature exceeding 1500°C, so that the carbon elements in the sample are completely converted into carbon dioxide. After purification, the concentration of carbon dioxide in the generated gas is detected by an infrared detector, and the total carbon mass percentage (wt%) in the sample is calculated accordingly. Before testing, the instrument was calibrated using standard samples, and the blank value of the flux was measured and deducted.

[0062] In some embodiments, the carbon material includes at least one of graphite and amorphous carbon, which can better improve the conductivity of the positive electrode active material, thereby better improving the rate performance of the battery.

[0063] In some embodiments, the thickness of the coating layer is 3 nm to 8 nm, which is beneficial for improving the conductivity of the positive electrode active material, thereby improving the rate performance of the battery. For example, the thickness of the coating layer is, for instance, a range of 3 nm, 4 nm, 5 nm, 8 nm, or any combination thereof.

[0064] This invention also provides a method for preparing the above-mentioned positive electrode active material, comprising the following steps:

[0065] The positive electrode active material is obtained by sequentially subjecting a raw material system including lithium source, manganese source, iron source, phosphorus source and M source to a first heating reaction and calcination treatment; the M source includes one or more elements selected from Mg, Zn, Ca, Al, Sr, Co, Ni and Cr.

[0066] The present invention provides a method for preparing the aforementioned positive electrode active material, which comprises a lithium manganese iron phosphate core. The lithium manganese iron phosphate core includes an element M, with the M element decreasing in value from the center outwards. The M element includes one or more elements selected from Mg, Zn, Ca, Al, Sr, Co, Ni, and Cr. This method allows for the preparation of a positive electrode active material with good stability and conductivity, which is beneficial for improving the cycle performance and rate performance of the battery.

[0067] In detail, the present invention first introduces low-valence metal ions (i.e., metal ions corresponding to element M, including ions corresponding to one or more of Mg, Zn, Ca, Sr, Co, Ni, and Cr) into the preparation process described above. This avoids high-valence ions inhibiting the nucleation of lithium manganese iron phosphate crystal lattice. The metal ions corresponding to element M can be doped into the lithium manganese iron phosphate crystal lattice after its main crystal lattice has been formed, which is beneficial to the stable formation of the lithium manganese iron phosphate crystal structure and improves the stability of the positive electrode active material. In addition, in the above preparation method, the concentration of element M is high at the beginning of the hydrothermal reaction and decreases at the end of the reaction. This results in a higher concentration of element M closer to the center of the lithium manganese iron phosphate core, ultimately forming a distribution pattern of element M that decreases from the center to the outside in the lithium manganese iron phosphate core, thus improving the conductivity of the positive electrode active material.

[0068] The present invention does not impose any special limitations on the selection of lithium source, manganese source, iron source, and phosphorus source, and can use commercially available products or raw materials synthesized by conventional synthesis methods in the art.

[0069] In some embodiments, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium oxalate, which is beneficial to further improve the preparation efficiency of the positive electrode active material, and can prepare a positive electrode active material with better stability and conductivity, which is beneficial to better improve the cycle performance and rate performance of the battery.

[0070] In some embodiments, the phosphorus source includes one or more of phosphoric acid, ammonium dihydrogen phosphate, sodium phosphate, sodium dihydrogen phosphate, and ammonium phosphate, which is beneficial to further improve the preparation efficiency of the positive electrode active material, and can prepare a positive electrode active material with better stability and conductivity, which is beneficial to better improve the cycle performance and rate performance of the battery.

[0071] In some embodiments, the manganese source includes one or more of manganese oxalate, manganese carbonate, manganese sulfate, and manganese acetate, which is beneficial to further improve the preparation efficiency of the positive electrode active material. It can prepare a positive electrode active material with better stability and conductivity, which is beneficial to better improve the cycle performance and rate performance of the battery.

[0072] In some embodiments, the iron source includes one or more of ferrous oxalate, ferrous nitrate, and ferrous sulfate, which is beneficial to further improve the preparation efficiency of the positive electrode active material, and can prepare a positive electrode active material with better stability and conductivity, which is beneficial to better improve the cycle performance and rate performance of the battery.

[0073] In some embodiments of the present invention, after the first heating reaction, a second heating reaction is further performed on a second reaction system comprising the product of the first heating reaction and the Q source. Through the above steps, the embodiments of the present invention can further dope the lithium manganese iron phosphate core with Q element, thereby further reducing the impact on the lithium manganese iron phosphate lattice and further improving the stability and conductivity of the positive electrode active material. Specifically, the Q element includes one or more elements selected from Ti, Zr, V, W, and Nb.

[0074] In this embodiment of the invention, the mass ratio of Q element in the positive electrode active material can be controlled by controlling the mass ratio or molar ratio of Q source in the second reaction system.

[0075] In some embodiments of the present invention, the second reaction system further includes a coating agent, which can form a coating layer on at least a portion of the surface of the lithium manganese iron phosphate core, thereby further improving the stability and conductivity of the positive electrode active material.

[0076] In some embodiments, the second reaction system further includes a precipitant, which is beneficial to further improve the preparation efficiency of the positive electrode active material.

[0077] In some embodiments, the raw material system further includes a pH adjuster, which is beneficial to further improve the preparation efficiency of the positive electrode active material. The embodiments of the present invention, through a two-stage heating reaction, can better achieve lattice doping of lithium manganese iron phosphate material and coating of the lithium manganese iron phosphate core, resulting in a more stable structure and conductivity of the positive electrode active material, and further improving industrial economics.

[0078] The coating agent in this embodiment of the invention includes at least one of a carbon source and an ion conductor raw material, which can further improve the coating effect of the positive electrode active material, and thus further improve the conductivity of the positive electrode active material.

[0079] Specifically, the coating agent in this embodiment of the invention may include only a carbon source, only an ion-conducting raw material, or both a carbon source and an ion-conducting raw material. The carbon source can form a carbon layer on at least a portion of the surface of the lithium manganese iron phosphate core. The coating agent, by including both a carbon source and an ion-conducting raw material, allows the ion-conducting material (generated after a second heating reaction) to be dispersed within the carbon material. In some embodiments, the ion-conducting material increases in size from the coating layer away from the lithium manganese iron phosphate core, which can be achieved by controlling the pH of the reaction. Specifically, as the pH continues to rise to near neutral, the ion-conducting material gradually becomes unstable and decomposes, hydrolyzing to generate an amorphous compound (the ion-conducting material), thus increasing the ion-conducting material from the coating layer away from the lithium manganese iron phosphate core.

[0080] In some embodiments, the reaction temperature of the first heating reaction is 140°C to 170°C, the reaction time is 2 hours to 8 hours, and the pH is 5.5 to 6.5, which is beneficial for further improving the preparation efficiency of the positive electrode active material. For example, the reaction temperature of the first heating reaction is, for example, a range of 140°C, 150°C, 160°C, 170°C, or any combination thereof; the reaction time of the first heating reaction is, for example, a range of 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or any combination thereof; and the pH of the first heating reaction is, for example, a range of 5.5, 6, 6.5, or any combination thereof.

[0081] In some embodiments, the reaction temperature of the second heating reaction is 170°C to 200°C, and the reaction time is 4h to 10h, which is beneficial to further improve the preparation efficiency of the positive electrode active material. For example, the reaction temperature of the second heating reaction is, for example, a range of 170°C, 180°C, 190°C, 200°C, or any combination thereof; the reaction time of the first heating reaction is, for example, a range of 4h, 5h, 6h, 7h, 8h, 9h, 10h, or any combination thereof.

[0082] In some embodiments, the calcination treatment includes a first calcination treatment and a second calcination treatment. The first calcination treatment is performed at a temperature of 300°C to 500°C for 0.5 h to 3 h for 0.5 h and at a heating rate of 2°C / min to 10°C / min. The second calcination treatment is performed at a temperature of 600°C to 800°C for 2 h to 8 h for 2 h, which is beneficial to further improve the preparation efficiency of the positive electrode active material. For example, the processing temperature of the first calcination treatment is, for example, a range of 300°C, 400°C, 500°C, or any combination thereof; the processing time of the first calcination treatment is, for example, a range of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, or any combination thereof; the heating rate of the first calcination treatment is, for example, a range of 2°C / min, 4°C / min, 6°C / min, 8°C / min, 10°C / min, or any combination thereof; the processing temperature of the second calcination treatment is, for example, a range of 600°C, 700°C, 800°C, or any combination thereof; and the processing time of the second calcination treatment is, for example, a range of 2h, 4h, 6h, 8h, or any combination thereof.

[0083] In some embodiments, the pH adjuster includes at least one of ammonia and citric acid, which is beneficial to further improve the preparation efficiency of the positive electrode active material.

[0084] In some embodiments, the precipitant includes at least one of urea and hexamethylenetetramine, which is beneficial to further improve the preparation efficiency of the positive electrode active material.

[0085] In some embodiments, the ion conductor raw materials include one or more of zirconium citrate, titanium oxalate, zirconium oxynitrate, and aluminum sol / aluminum isopropoxide, which is beneficial to further improve the preparation efficiency of the positive electrode active material.

[0086] In some embodiments, the M source includes one or more of magnesium sulfate, magnesium acetate, and zinc sulfate, which is beneficial to further improve the preparation efficiency of the positive electrode active material.

[0087] In some embodiments, the Q source includes one or more of ammonium metavanadate, sodium tungstate, niobium oxalate, zirconium oxychloride, and titanium oxysulfate, which is beneficial to further improve the preparation efficiency of the positive electrode active material.

[0088] In some embodiments, the carbon source may include one or more of ascorbic acid, glucose, citric acid, sucrose, polyethylene glycol, and acetylene black, which is beneficial to further improve the preparation efficiency of the positive electrode active material.

[0089] In some embodiments, an antioxidant, such as ascorbic acid, may be added to the above-described raw material system. That is, ascorbic acid can simultaneously provide a carbon source and have an antioxidant effect.

[0090] This invention also provides a positive electrode sheet, which includes a positive electrode active material layer comprising the aforementioned positive electrode active material. The positive electrode sheet has advantages corresponding to the aforementioned positive electrode active material, which will not be elaborated upon here.

[0091] In some embodiments of the present invention, the product of the second heating reaction is further cooled, filtered, washed, and dried after the second heating reaction to obtain a precursor material. The precursor material is then ground and passed through a 100-mesh sieve, and then calcined.

[0092] In some embodiments of the present invention, the first heating reaction and the second heating reaction can be carried out in a solvent, which may include at least one of water and diethylene glycol.

[0093] This invention also provides a battery comprising the aforementioned positive electrode sheet. The battery provided by this invention has advantages corresponding to the aforementioned positive electrode active material, which will not be elaborated upon here.

[0094] The battery in this embodiment of the invention can be a lithium-ion battery (such as a lithium-ion power battery).

[0095] Generally, a battery includes an electrolyte, a battery cell, and a casing that encapsulates the battery cell. The electrolyte is injected into the battery cell inside the casing. The battery cell includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrode. The battery cell can be a stacked cell, meaning it is composed of alternating layers of positive electrode, separator, and negative electrode; or it can be a wound cell, meaning it is composed of stacked positive electrode, separator, and negative electrode, which are then wound together.

[0096] Specifically, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side surface of the positive current collector. Specifically, the positive active material layer can be provided on one side surface in the thickness direction of the positive current collector, or positive active material layers can be provided on both opposite sides surface in the thickness direction of the positive current collector.

[0097] Specifically, when the battery in this embodiment of the invention is a lithium-ion battery, the positive electrode active material layer may include a positive electrode active material, a conductive agent, and a binder. In the positive electrode active material layer, the mass percentage of the positive electrode active material may be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any two of these ranges. The mass fraction of the conductive agent may be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any two of these ranges. The mass fraction of the binder may be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any two of these ranges.

[0098] In this embodiment of the invention, the conductive agent in the positive electrode active material layer can be a conventional conductive material in the art. For example, the conductive agent in the positive electrode active material layer may include one or more of conductive carbon black, conductive graphite, carbon nanotubes (CNTs), carbon fibers, graphene, acetylene black, and Ketjen black.

[0099] In this embodiment of the invention, the binder in the positive electrode active material layer can be a conventional binder in the art. For example, the binder in the positive electrode active material layer may include one or more of the following: polyvinylidene fluoride (PVDF), polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, etc.

[0100] The embodiments of the present invention may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0101] In the embodiments of the present invention, unless otherwise specified, the coating, drying, rolling and other processes involved are all conventional operations in the art, and the equipment used can be conventional equipment in the art, and there are no special restrictions on them.

[0102] In this embodiment of the invention, the positive electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the positive electrode active material layer, such as the positive electrode active material, conductive agent, and binder, can be dispersed in a solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry. This slurry is then coated onto the surface of the positive electrode current collector, and after drying, rolling, and other processes, the positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method, and are not particularly limited thereto.

[0103] Specifically, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side surface of the negative electrode current collector. Specifically, the negative electrode active material layer can be provided on one side surface of the negative electrode current collector, or negative electrode active material layers can be provided on both opposite sides of the negative electrode current collector in the thickness direction.

[0104] Specifically, the negative electrode active material layer may include a negative electrode active material, a conductive agent, and a binder, all of which can be conventional materials in the art. For example, the negative electrode active material may include one or more of natural graphite, artificial graphite, petroleum coke, and silicon carbide materials; the conductive agent may include one or more of conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber; and the binder may include one or more of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0105] The embodiments of the present invention may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors include copper foil.

[0106] In this embodiment of the invention, the negative electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the negative electrode active material layer, such as the negative electrode active material, conductive agent, and binder, can be dispersed in a solvent, such as water, to prepare a negative electrode slurry. This slurry is then coated onto the surface of the negative electrode current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing negative electrode sheets using the coating method, and are not particularly limited thereto.

[0107] The electrolyte in this embodiment of the invention can be a conventional electrolyte in the art. For example, the electrolyte is a non-aqueous electrolyte, which may specifically include organic solvents, additives and electrolyte salts. Organic solvents include one or more of ethylene carbonate (EC), diethyl carbonate (DEC) and propylene carbonate (PC). Additives include, for example, fluoroethylene carbonate (FEC) and vinylene carbonate (VC). Electrolyte salts may include lithium salts, such as lithium hexafluorophosphate (LiPF6), but are not limited thereto.

[0108] In this embodiment of the invention, the separator is used to separate the positive and negative electrode plates, preventing short circuits caused by contact between them. Conventional separators in the art can be used in this embodiment, and there are no particular limitations. For example, the separator material can be one or more of the following: high-density polyethylene, ultra-high-density polyethylene, low-density polyethylene, linear low-density polyethylene, high-density polypropylene, ultra-high-density polypropylene, polyimide, and polyvinylidene fluoride.

[0109] In this embodiment of the invention, the battery cell can be packaged using conventional housing materials in the art, such as flexible packaging materials like aluminum-plastic film, but is not limited thereto.

[0110] The embodiments of the present invention can assemble components such as positive electrode, separator and negative electrode into a battery using conventional methods in the art. For example, positive electrode, separator and negative electrode can be stacked in an alternating manner to obtain a stacked cell (or wound into a wound cell); then the cell is placed in a casing (outer packaging) and after conventional processes such as electrolyte injection (i.e., injection of electrolyte) and encapsulation, the battery is obtained.

[0111] This invention also provides a battery pack including the battery described above. This battery pack has advantages corresponding to the positive electrode active material described above, which will not be elaborated further.

[0112] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0113] This invention also provides an electrical device, including the battery or battery pack described above. This electrical device has advantages corresponding to the positive electrode active material described above, which will not be elaborated further.

[0114] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0115] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0116] Example 1

[0117] The positive electrode active material in this embodiment is prepared by the following method:

[0118] 1) Solution preparation:

[0119] Solution A (lithium source and phosphorus source): Lithium hydroxide and phosphoric acid are dissolved in a mixed solvent (pure water + diethylene glycol).

[0120] Solution B (M source and Q source): Dissolve ferrous sulfate, manganese sulfate, magnesium sulfate (M source), and a small amount of ascorbic acid (antioxidant) in pure water.

[0121] Solution C (pH adjuster): Diluted ammonia solution or citric acid solution.

[0122] Solution D (Q source and carbon source): Ammonium metavanadate (Q source) and water-soluble organic carbon source (glucose + ascorbic acid) are dissolved in deionized water.

[0123] Solution E (Ionic conductor raw material and precipitant): The ionic conductor raw material (specifically zirconium citrate) and the precipitant (specifically urea) are dissolved in deionized water.

[0124] 2) Reaction:

[0125] Under continuous N2 protection and stirring, solution B was slowly added to solution A via a peristaltic pump, while solution C was added dropwise simultaneously, precisely stabilizing the pH of the system between 5.5 and 6.5. After the addition was complete, the mixture was stirred for 10 minutes. This slurry was then transferred to a hydrothermal reactor, and the temperature was increased at a rate of 10°C / min, with a first heating reaction at 160°C for 3 hours. After the first heating reaction, the temperature was lowered and the pressure was released. Subsequently, solutions D and E were added to the reactor sequentially via a peristaltic pump, and a second heating reaction was carried out at 180°C for 5 hours. After the second heating reaction, the mixture was cooled, filtered, washed, and dried to obtain the precursor material. The precursor material was then ground and passed through a 100-mesh sieve, followed by a one-step heat treatment in a tube furnace under N2 atmosphere: a first calcination treatment was performed at 450°C at a rate of 5°C / min for 1 hour, followed by a second calcination treatment at 720°C for 5 hours, yielding the positive electrode active material.

[0126] In the positive electrode active material prepared in the embodiments of the present invention, the carbon material is amorphous carbon, and the ion conductor material is uniformly dispersed in the coating layer.

[0127] Example 2

[0128] This embodiment is basically the same as Embodiment 1, except that the amount of magnesium sulfate added in this embodiment is different from that in Embodiment 1.

[0129] Example 3

[0130] This embodiment is basically the same as Embodiment 1, except that the amount of ion conductor raw material added in this embodiment is different from that in Embodiment 1.

[0131] Examples 4-6 are basically the same as Example 1, except that the amounts of ferrous sulfate, manganese sulfate, and magnesium sulfate are different.

[0132] Example 7

[0133] This embodiment is basically the same as Embodiment 1, except that the Q source in this embodiment is titanium oxysulfate and the ion conductor material is aluminum isopropoxide.

[0134] Example 8

[0135] This embodiment is basically the same as Embodiment 1, except that the Q source in this embodiment is sodium tungstate and the ion conductor material is titanium oxalate.

[0136] Examples 9-12 are basically the same as Example 1, except that the amount of Q source used is different from that in Example 1.

[0137] Examples 13-14 are basically the same as Example 1, except that the amount of carbon source used is different from that in Example 1.

[0138] Example 15

[0139] This embodiment is basically the same as Embodiment 1, except that the preparation method of the positive electrode active material in this embodiment does not include Q source and ion conductor raw material, and the prepared positive electrode active material does not include Q element and ion conductor material.

[0140] Example 16

[0141] This embodiment is basically the same as Embodiment 1, except that no ion conductor raw material is added in the preparation method of the positive electrode active material in this embodiment, and the positive electrode active material obtained does not include ion conductor material.

[0142] Comparative Example 1

[0143] The difference between this comparative example and Example 1 is that in this comparative example, solutions A, B, C, D, and E were directly mixed and then subjected to a hydrothermal reaction at 180°C for 5 hours. In the prepared positive electrode active material, element M is uniformly dispersed in the lithium manganese iron phosphate core.

[0144] Comparative Example 2

[0145] The difference between this comparative example and Example 1 is that the preparation method of the positive electrode active material in this example does not include the M source, and the prepared positive electrode active material does not contain the M element.

[0146] Comparative Example 3

[0147] In the preparation process of the positive electrode active material in this comparative example, solutions B and D were not added, meaning that the prepared positive electrode active material only included lithium manganese iron phosphate material and a carbon coating layer covering the lithium manganese iron phosphate material.

[0148] The composition of the lithium manganese iron phosphate core (referred to as lithium manganese iron phosphate core in the table), Q element, atomic ratio z of Q element and the total atomic weight of Fe and Mn in the lithium manganese iron phosphate core (referred to as atomic ratio of Q element in the table), mass ratio of carbon material in the positive electrode active material (referred to as mass ratio of carbon material in the table), mass ratio of ion conductor material in the positive electrode active material (referred to as mass ratio of ion conductor material in the table), thickness of the coating layer, and ion conductor material are shown in Table 1.

[0149]

[0150] " / " indicates that the substance is not present.

[0151] Test case

[0152] Battery Assembly: After fabricating the positive electrode active materials from the above embodiments and comparative examples into positive electrode sheets, they are assembled with negative electrode sheets, electrolytes, and separators according to the following method to obtain a lithium-ion battery. The method includes:

[0153] 1) The positive electrode active materials from the examples and comparative examples were mixed with conductive carbon black and PVDF at a weight ratio of 96%:2%:2%, respectively, and dispersed to obtain a positive electrode slurry. This slurry was coated onto an aluminum foil current collector, with a positive electrode areal density of 4.12 g / cm³. 3 The positive electrode sheet is prepared by rolling.

[0154] 2) Artificial graphite, styrene-diene rubber (SBR), sodium carboxymethyl cellulose, and conductive carbon black are mixed in a weight ratio of 94%:3%:2%:1%. The mixture is dispersed in water and then mixed using a double planetary mixing process to obtain a negative electrode slurry. This slurry is coated onto a copper current collector, followed by rolling and drying to obtain the negative electrode sheet.

[0155] 3) Assemble the positive electrode, negative electrode, and separator into a lithium-ion battery and inject a non-aqueous electrolyte. The electrolyte is prepared by mixing ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC) in a mass ratio of 2:5:3. Then, add 5% fluoroethylene carbonate (FEC) and 13% lithium hexafluorophosphate (LiPF6) by mass, along with additives vinylene carbonate (VC, 1%) and lithium difluorooxalate borate (LiDFOB, 1%). The additive content accounts for 2% of the total electrolyte content.

[0156] Discharge specific capacity test and charge specific capacity test: After each battery was left to stand at 25℃ for 4 hours, the first charge-discharge capacity test was performed. The test conditions were: charging at 0.1C to 4.55V, constant voltage charging to 0.025C cutoff, standing for 3 minutes, and then discharging at 0.1C to 3.0V. The charge-discharge curves were obtained, and the first charge specific capacity C0 and the first discharge specific capacity D0 at 4.4~4.55V were recorded respectively. The first coulombic efficiency was calculated according to D0 / C0. The test results are shown in Table 2.

[0157] Capacity retention test: The capacity retention of each battery was tested. The specific test method was as follows: at 25℃, the battery was charged at a constant current rate of 1C to 4.50V, then charged at a constant voltage rate of 0.05C to 4.50V, and then discharged at a discharge rate of 1C to 3.0V. This charge-discharge cycle was repeated 300 times. The discharge capacity Q1 at the first cycle and the discharge capacity Q300 at the 300th cycle were measured. After fully charging the battery, the cells were removed and left to stand at room temperature for 3 hours. The full-charge thickness D1 was then measured.

[0158] The capacity retention rate Q after 300 cycles is calculated using the following formula.

[0159] Capacity retention rate Q = Q300 / Q1 × 100%. Test results are shown in Table 2.

[0160] Electrochemical impedance spectroscopy (EIS) testing: The batteries from the above examples and comparative examples were tested using an electrochemical workstation (CHI760E). Specifically, the batteries were connected to the workstation with the positive electrode (WE) as the working electrode and the negative electrode (CE) as the counter electrode and reference electrode (RE). Operating parameters were set, including frequency range (100 kHz - 0.1 Hz) and amplitude (10 mV). The test was run, and an appropriate circuit model was selected to perform equivalent circuit fitting on the test data. The ohmic resistance (R) was then read. Ω ) and charge transfer impedance (R ct Total battery impedance = R Ω + R ct The test results are shown in Table 2.

[0161] 1C Rate Capacity Test: The battery was charged and discharged at 25℃ using a battery charge / discharge tester. The charge / discharge regime was as follows: 0.2C constant current charging to 4.25V, then switching to 4.25V constant voltage charging until the current decreased to 0.02C, followed by a 5-minute rest period, and finally 0.2C constant current discharging to 2.5V. The discharge capacity Q was recorded. 0.2c After resting for 5 minutes, charge with a constant current of 0.2C to 4.25V, then switch to a constant voltage of 4.25V and charge until the current decreases to 0.02C. After resting for 5 minutes, discharge with a constant current of 1C to 2.5V, and record the discharge capacity Q. 1cThe capacity retention rate can be calculated using the following formula:

[0162] 1C discharge rate capacity retention rate = Q 1c / Q 0.2c ×100%. The test results are shown in Table 2.

[0163]

[0164] As shown in Table 2, compared with the comparative example, the embodiments of the present invention effectively improve the first efficiency, capacity retention rate and rate performance of the battery by doping the lithium manganese iron phosphate core with element M and making the element M decrease from the center of the lithium manganese iron phosphate core to the outside.

[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode active material, characterized in that, It includes a lithium manganese iron phosphate core, wherein the lithium manganese iron phosphate core includes an element M, and the element M decreases from the center of the lithium manganese iron phosphate core to the outside; The element M includes one or more of the following: Mg, Zn, Ca, Al, Sr, Co, Ni, and Cr.

2. The positive electrode active material according to claim 1, characterized in that, The lithium manganese iron phosphate core includes LiMn. 1- x Fe x M y PO4; Where 1-x>0, x>0; y>0.

3. The positive electrode active material according to claim 1 or 2, characterized in that, The lithium manganese iron phosphate core also includes a Q element, which includes one or more elements selected from Ti, Zr, V, W, and Nb. Wherein, the atomic percentage z of the Q element and the total atomic weight of Fe and Mn elements in the lithium manganese iron phosphate core is 0.1at% ≤ z ≤ 0.5at%; And / or, 0.2≤x≤0.7, 0<y≤0.

02.

4. The positive electrode active material according to claim 1 or 2, characterized in that, At least a portion of the surface of the lithium manganese iron phosphate core is provided with a coating layer, the coating layer comprising a carbon material.

5. The positive electrode active material according to claim 4, characterized in that, The resistivity of the positive electrode active material is 20 Ω·cm to 100 Ω·cm; And / or, the thickness of the coating layer is 1 nm to 10 nm; And / or, the coating layer further includes an ion-conducting material dispersed in the carbon material.

6. The positive electrode active material according to claim 5, characterized in that, The ion conductor material increases in size from the coating layer away from the lithium manganese iron phosphate core; And / or, the ion conductor material accounts for 1.0 wt% to 2.0 wt% of the mass of the positive electrode active material; And / or, the ionic conductor material includes one or more of lithium lanthanum titanate, lithium lanthanum zirconate, lithium titanium aluminum phosphate, and lithium germanium aluminum phosphate; And / or, the carbon material accounts for 1.0 wt% to 2.0 wt% of the mass of the positive electrode active material; And / or, the carbon material includes one or more of graphite, amorphous carbon, carbon nanotubes, and graphene; And / or, the thickness of the coating layer is 3nm~8nm.

7. A method for preparing the positive electrode active material according to any one of claims 1-6, characterized in that, Includes the following steps: The positive electrode active material is obtained by sequentially subjecting a raw material system including lithium source, manganese source, iron source, phosphorus source and M source to a first heating reaction and calcination treatment. The M source includes one or more elements selected from Mg, Zn, Ca, Al, Sr, Co, Ni, and Cr.

8. The method for preparing the positive electrode active material according to claim 7, characterized in that, After the first heating reaction, the process further includes subjecting a second reaction system, which includes the product of the first heating reaction and the Q source, to a second heating reaction. The second reaction system also includes a coating agent; And / or, the second reaction system further includes a precipitant; And / or, the raw material system may also include a pH adjuster.

9. The method for preparing the positive electrode active material according to claim 8, characterized in that, The coating agent includes at least one of a carbon source and an ion conductor material; And / or, the reaction temperature of the first heating reaction is 140℃~170℃, the reaction time is 2h~8h, and the pH is 5.5~6.5; And / or, the reaction temperature of the second heating reaction is 170℃~200℃, and the reaction time is 4h~10h; And / or, the calcination treatment includes a first calcination treatment and a second calcination treatment, wherein the first calcination treatment has a treatment temperature of 300℃~500℃, a treatment time of 0.5h~3h, and a heating rate of 2℃ / min~10℃ / min; the second calcination treatment has a treatment temperature of 600℃~800℃, and a treatment time of 2h~8h; And / or, the pH adjuster includes at least one of ammonia and citric acid; And / or, the precipitant includes at least one of urea and hexamethylenetetramine; And / or, the ion conductor raw material includes one or more of zirconium citrate, titanium oxalate, zirconium oxynitrate, aluminum sol, and aluminum isopropoxide; And / or, the M source includes one or more of magnesium sulfate, magnesium acetate, and zinc sulfate; And / or, the Q source includes one or more of ammonium metavanadate, sodium tungstate, niobium oxalate, zirconium oxychloride, and titanium oxysulfate.

10. A positive electrode plate, characterized in that, This includes the positive electrode active material according to any one of claims 1-6, or the positive electrode active material prepared by the method according to any one of claims 7-9.

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