CN-121983555-A - Positive electrode active material, preparation method thereof and battery

CN121983555ACN 121983555 ACN121983555 ACN 121983555ACN-121983555-A

Abstract

The application relates to a positive electrode active material, a preparation method thereof and a battery, belonging to the technical field of batteries, wherein V ions in the vanadium iron phosphate lithium active material enter LFP crystal lattice to replace Fe 2+ sites through doping to form crystal lattice defects, and the system spontaneously generates extra free electrons to increase the electron conductivity of the system in order to keep electric neutrality, thereby being beneficial to the rate capability of the system when the system is applied to the battery. Meanwhile, on the basis of doping the V element, the mass content of the ferric phosphide in the vanadium iron phosphate lithium active material is controlled to be less than or equal to 800ppb, so that the probability of side reaction with electrolyte when the vanadium iron phosphate lithium active material is applied to a battery can be reduced, and the cycle performance is facilitated. The vanadium lithium phosphate active material has two particles with specific volume median particle diameters, and can form a better particle size grading relationship, so that the vanadium lithium phosphate active material has higher compaction density, and is beneficial to the volume energy density when the vanadium lithium phosphate active material is applied to a battery.

Inventors

CHEN HAIYANG
PENG JIAN
ZHANG SHUTAO

Assignees

宁波容百新能源科技股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260226

Claims (10)

1. The positive electrode active material is characterized by comprising a vanadium iron phosphate active material, wherein the molar ratio of V element to non-lithium metal element in the vanadium iron phosphate active material is 0.001-0.005:1, the mass content of iron phosphide in the vanadium iron phosphate active material is less than or equal to 800ppb, the vanadium iron phosphate active material comprises first particles and second particles, the volume median particle diameter of the first particles is less than or equal to 2.8 mu m, the volume median particle diameter of the second particles is less than or equal to 0.2 mu m, and the volume median particle diameter of the second particles is less than or equal to 0.8 mu m.
2. The positive electrode active material according to claim 1, wherein the lithium vanadium phosphate-based active material comprises Li a Fe 1-x-y V x M y PO 4 , wherein a is more than or equal to 0.9 and less than or equal to 1.1,0.002 and less than or equal to x is more than or equal to 0.01,0 and less than or equal to 0.098,0.002 and x+y is more than or equal to 0.01, and M comprises at least one of Ti, sn, sb, mo, bi.
3. The positive electrode active material according to claim 1 or 2, wherein the compacted density of the vanadium iron phosphate lithium active material at 3t is not less than 2.7g/cm 3 , and/or The number ratio of the first particles to the second particles is 1:1-6, and optionally, the number ratio of the first particles to the second particles is 1:3-6.
4. The positive electrode active material according to claim 1 or 2, wherein the lithium vanadium phosphate-based active material has a core-shell structure whose inner core includes an active material body, the active material body comprises Li a Fe 1-x- y V x M y PO 4 , wherein a is more than or equal to 0.9 and less than or equal to 1.1,0.002 and less than or equal to 0.01,0, y is more than or equal to 0.098,0.002 and less than or equal to x+y is more than or equal to 0.01, M comprises at least one of Ti, sn, sb, mo, bi, the shell layer comprises a first shell layer and a second shell layer, the first shell layer is arranged between the inner core and the second shell layer, the material of the first shell layer comprises a carbon material, the electronic conductivity of the second shell layer is more than or equal to 1 multiplied by 10 3 S/cm, and the ionic conductivity of the second shell layer is more than or equal to 8 multiplied by 10 -4 S/cm.
5. The positive electrode active material according to claim 4, wherein the material of the second shell layer comprises a highly ion conductive material having an ion conductivity of 1 x 10 -3 S/cm or more and a highly electron conductive material having an electron conductivity of 1 x 10 4 S/cm or more.
6. The positive electrode active material according to claim 5, wherein a mass ratio of the high ion conductive material to the high electron conductive material is 80 to 90:10 to 20; The high-conductivity ionic material comprises at least one of garnet-type solid electrolyte, NASICON-type solid electrolyte or perovskite-type solid electrolyte, optionally the garnet-type solid electrolyte comprises lithium lanthanum zirconium oxide, the NASICON-type solid electrolyte comprises at least one of titanium aluminum lithium phosphate, titanium germanium lithium phosphate or lithium zirconium silicon phosphorus oxide, the perovskite-type solid electrolyte comprises lithium lanthanum titanium oxide, and/or, The high conductivity sub-material comprises TaN x , where x <1.
7. The positive electrode active material according to any one of claims 4 to 6, wherein the thickness of the first shell layer is 3nm to 5nm, and/or, The thickness of the second shell layer is 3 nm-4 nm.
8. A method for preparing a positive electrode active material, comprising: Mixing an iron source, a lithium source, a phosphorus source and a first shell layer source to obtain a sintering precursor, wherein the iron source at least comprises two iron sources; The sintering precursor is subjected to first sintering to obtain an intermediate product, wherein the first sintering comprises primary sintering and secondary sintering, the heat preservation temperature of the primary sintering is 300-450 ℃, and the air pressure of the secondary sintering is 1-5 MPa; and mixing the intermediate product with an additive, and performing second sintering to obtain the anode active material, wherein the additive comprises a first additive and a second additive, the first additive contains chlorine element, the second additive contains vanadium element, and the molar ratio of the vanadium element to the intermediate product in the second additive is 0.001-0.005:1.
9. The method for producing a positive electrode active material according to claim 8, wherein the iron source comprises at least two of iron phosphate, ferrous oxalate, iron oxide, iron hydroxide or iron powder, and/or, The lithium source comprises at least one of lithium carbonate, lithium hydroxide or lithium acetate, and/or, The phosphorus source comprises at least one of ammonium dihydrogen phosphate or phosphoric acid, and/or, The first shell source comprises a carbon source comprising at least one of glucose, fructose, sucrose, citric acid, tartaric acid, ascorbic acid or polyethylene glycol, and/or, The mass of the first shell layer source is 5% -12% of the sum of the mass of the iron source, the mass of the lithium source and the mass of the phosphorus source, and/or, The volume median particle diameter of the sintering precursor is 300 nm-450 nm, and/or, The temperature rising rate of the first-stage sintering is 1-3 ℃ per minute and/or, The heat preservation time of the sintering is 1-3 h, and/or, The atmosphere of the one-stage sintering is at least one of nitrogen atmosphere or inert gas atmosphere, and/or, The air pressure of the first-stage sintering is 0.08-0.12 MPa, and/or, The heat preservation temperature of the two-stage sintering is 700-840 ℃ and/or, The temperature rising rate of the two-stage sintering is 3-5 ℃ per minute and/or, The heat preservation time of the two-stage sintering is 8-12 h, and/or, The first additive comprises at least one of vanadium chloride, titanium chloride, tin chloride, antimony chloride, molybdenum chloride or bismuth chloride, and/or, The second additive comprises vanadium chloride, and/or, The heat preservation temperature of the second sintering is 600-750 ℃ and/or, The temperature rising rate of the second sintering is 2-5 ℃ per minute, and/or, The heat preservation time of the second sintering is 2-8 hours, and/or, The second sintering is preceded by mixing a second shell source, the intermediate product and an additive, wherein the material of the second shell comprises a high-conductivity ionic material and a high-conductivity electronic material, the ionic conductivity of the high-conductivity ionic material is more than or equal to 1 multiplied by 10 - 3 S/cm, the electronic conductivity of the high-conductivity electronic material is more than or equal to 1 multiplied by 10 4 S/cm, and/or And the mass ratio of the second shell layer source to the intermediate product is 1-3:100.
10. A battery comprising a positive electrode sheet including a positive electrode active material layer including a positive electrode active material including the positive electrode active material according to any one of claims 1 to 7 or the positive electrode active material produced by the positive electrode active material production method according to any one of claims 8 to 9.

Description

Positive electrode active material, preparation method thereof and battery Technical Field The application relates to the technical field of batteries, in particular to a positive electrode active material, a preparation method thereof and a battery. Background Lithium vanadium phosphate positive electrode active materials, such as lithium vanadium phosphate (LFVP), have become one of the most important positive electrode materials in the fields of power batteries and energy storage batteries due to their excellent safety, long cycle life and low cost. However, the current lithium vanadium iron phosphate positive electrode active material has difficulty in achieving high electron conductivity, low impurities and high compaction density. Disclosure of Invention The application provides a positive electrode active material which can achieve high electron conductivity, low impurity content and high compaction density. In a first aspect, the embodiment of the application provides a positive electrode active material, which comprises a vanadium iron phosphate active material, wherein the molar ratio of V element to non-lithium metal element in the vanadium iron phosphate active material is 0.001-0.005:1, the mass content of iron phosphide in the vanadium iron phosphate active material is less than or equal to 800ppb, the vanadium iron phosphate active material comprises first particles and second particles, the volume median particle diameter of the first particles is less than or equal to 2.8 μm, and the volume median particle diameter of the second particles is less than or equal to 0.2 μm and less than or equal to 0.8 μm. In the technical scheme of the embodiment of the application, V ions in the lithium vanadium iron phosphate active material enter LFP crystal lattice to replace Fe 2+ sites through doping to form crystal lattice defects, and in order to keep electric neutrality, the system spontaneously generates extra free electrons, so that the electron conductivity of the system is increased, and the system is favorable for the rate capability of the system when the system is applied to batteries. Meanwhile, on the basis of doping the V element, the mass content of the ferric phosphide in the vanadium iron phosphate lithium active material is controlled to be less than or equal to 800ppb, so that the probability of side reaction with electrolyte when the vanadium iron phosphate lithium active material is applied to a battery can be reduced, and the cycle performance is facilitated. The vanadium lithium phosphate active material has two particles with specific volume median particle diameters, and can form a better particle size grading relationship, so that the vanadium lithium phosphate active material has higher compaction density, and is beneficial to the volume energy density when the vanadium lithium phosphate active material is applied to a battery. Finally, the lithium vanadium iron phosphate active material can have high electron conductivity, low impurity and high compaction density, and the battery adopting the lithium vanadium iron phosphate active material as the positive electrode active material can have better multiplying power performance, cycle performance and volume energy density. As an alternative embodiment, the lithium vanadium phosphate-based active material includes Li aFe1-x-yVxMyPO4, wherein, a is more than or equal to 0.9 and less than or equal to 1.1,0.002 and x is more than or equal to 0.9 and less than or equal to x 0.01,0 y is less than or equal to 0.098,0.002 x is less than or equal to +y is less than or equal to 0.01, and M comprises at least one of Ti, sn, sb, mo, bi. In the implementation process, the Li aFe1-x-yVxMyPO4 has better electron conductivity and ion diffusion rate, and is favorable for the rate performance of the battery. As an alternative embodiment, the compacted density of the lithium vanadium iron phosphate active material at 3t is more than or equal to 2.7g/cm 3. In the implementation process, the compaction density of the lithium vanadium iron phosphate active material at 3t is controlled to be more than or equal to 2.7g/cm 3, so that the battery has better volume energy density when the lithium vanadium iron phosphate active material is applied to the battery. As an alternative embodiment, the number ratio of the first particles to the second particles is 1:1-6. In the implementation process, the first particles and the second particles are controlled within a proper amount range, so that the lithium vanadium iron phosphate active material can have higher compaction density. As an alternative embodiment, the number ratio of the first particles to the second particles is 1:3-6. As an alternative implementation mode, the lithium vanadium phosphate active material has a core-shell structure, the core of the core-shell structure comprises an active material body, the active material body comprises Li aFe1-x-yVxMyPO4, a is more than or equal to 0.9 and less