CN-118289724-B - Preparation method of phosphoric acid pretreatment and ion doping co-modified lithium iron phosphate positive electrode material

CN118289724BCN 118289724 BCN118289724 BCN 118289724BCN-118289724-B

Abstract

The invention provides a preparation method of a co-modified lithium iron phosphate positive electrode material through phosphoric acid pretreatment and ion doping, which comprises the steps of mixing a lithium source, an iron source, a phosphorus source, a carbon source, a titanium source and a vanadium source with water as a solvent, sanding, taking out slurry after sanding, spray drying the slurry to obtain a yellow material, calcining the yellow material in an inert atmosphere for the first time to obtain a lithium iron phosphate precursor, ageing the lithium iron phosphate precursor in a phosphoric acid solution, filtering and drying to obtain black powder, and carrying out secondary calcination on the obtained black powder in the inert atmosphere to obtain the lithium iron phosphate positive electrode material. The lithium iron phosphate precursor is dispersed in the phosphoric acid solution with a certain concentration, so that certain defects are generated on the surface of the acidified precursor, the growth of particles is facilitated after secondary calcination, the compaction density is improved, meanwhile, residual phosphate is adhered to the surface of the precursor and permeates into the surface layer, the diffusion of lithium ions among the particles can be promoted, and the transmission of lithium ions and electrons among the particles is promoted.

Inventors

JIANG NINGBO
DONG QIAOQIAO
FAN SHITAO
ZHENG LEI
CHENG YALI
LIU CHANG
MA HUIJUAN
ZHANG CHI
HU ZHENGLEI
JIANG TAO
Zhang Tianzhuang

Assignees

湖北兴发化工集团股份有限公司

Dates

Publication Date: 20260508
Application Date: 20240321

Claims (5)

1. The preparation method of the co-modified lithium iron phosphate positive electrode material through phosphoric acid pretreatment and ion doping is characterized by comprising the following steps of: Mixing a lithium source, an iron source, a phosphorus source, a carbon source, a titanium source and a vanadium source by using water as a solvent, and then sanding, wherein the lithium source, the carbon source, the titanium source, the vanadium source and the iron source are fed according to the molar ratio of lithium to carbon to titanium to vanadium to iron=1.02-1.06:0.3-0.5:0.008-0.03:0.001-0.006:1; step (2), sand grinding to a certain particle size and then taking out the slurry; step (3), spray drying the slurry obtained in the step (2) to obtain yellow materials; The yellow material in the step (3) is calcined for the first time in inert atmosphere to obtain a lithium iron phosphate precursor; Placing the lithium iron phosphate precursor in the step (4) into a phosphoric acid solution with a certain concentration according to a certain proportion, aging for a certain time, performing suction filtration, and drying to obtain black powder, wherein the concentration of phosphoric acid is 50% -75%, and the quality of the added lithium iron phosphate precursor is controlled according to the solid content of 20% -60%; And (6) carrying out secondary calcination on the black powder obtained in the step (5) in an inert atmosphere to obtain the lithium iron phosphate anode material.
2. The method for preparing a co-modified lithium iron phosphate positive electrode material by phosphoric acid pretreatment and ion doping according to claim 1, wherein the iron source used in the step (2) is one of ferrous sulfate, ferrous oxalate, ferrous chloride and ferric phosphate; the lithium source is one of lithium hydroxide, lithium carbonate, lithium bicarbonate and lithium dihydrogen phosphate; the carbon source is one of glucose, sucrose, fructose, polyethylene glycol and tannic acid; The titanium source is one or more of titanium dioxide and tetrabutyl titanate; The vanadium source is one or more of ammonium metavanadate, vanadium pentoxide and vanadyl oxalate.
3. The method for preparing the co-modified lithium iron phosphate positive electrode material by phosphoric acid pretreatment and ion doping according to claim 1, wherein the particle size D50 in the step (2) is 300-500nm.
4. The method for preparing the co-modified lithium iron phosphate positive electrode material by phosphoric acid pretreatment and ion doping according to claim 1, wherein the calcining condition in the step (4) is 300-400 ℃, the heating rate is 2-5 ℃ per minute, the heat preservation time is 1-2h, and the protective gas is one of N 2 and Ar.
5. The method for preparing the co-modified lithium iron phosphate positive electrode material by phosphoric acid pretreatment and ion doping according to claim 1, wherein in the step (6), the calcining temperature is 600-800 ℃, the heating rate is 2-5 ℃ per minute, the heat preservation time is 7-10h, and the inert atmosphere is one of N 2 and Ar.

Description

Preparation method of phosphoric acid pretreatment and ion doping co-modified lithium iron phosphate positive electrode material Technical Field The invention relates to a lithium ion battery positive electrode material and a preparation method thereof in the field of electrochemical energy storage, in particular to a phosphoric acid pretreatment and ion doping co-modified lithium iron phosphate positive electrode material and a preparation method thereof. Background Lithium iron phosphate (LiFePO 4) is widely used in portable electronic equipment and new energy automobiles due to the advantages of high safety, long cycle life, environmental protection, low preparation cost and the like, however, the defect of too low intrinsic conductivity of the lithium iron phosphate is always limiting the further development of the lithium iron phosphate, and the current application of wide carbon coating is to coat the surface of lithium iron phosphate particles by means of a conductive carbon layer so as to improve the electronic conductivity of the material, but the carbon coating is not beneficial to the passage of ions and cannot improve the ionic conductivity of the material. The Chinese patent No. CN111403710A discloses a preparation method of an aluminum trifluoride (AlF 3) coated ternary doped lithium manganate positive electrode material, wherein the aluminum trifluoride (AlF 3) can effectively relieve capacity attenuation after coating, prevent electrolyte corrosion and reduce manganese ion dissolution, and the Chinese patent No. CN107591532B coats nickel cobalt lithium manganate positive electrode material with silver and aluminum fluoride in a double-layer manner, wherein the inner shell is aluminum fluoride, the outer shell is silver, and the electronic conductivity and the ionic conductivity of the material can be simultaneously improved, but the cost of the silver is higher, and the preparation process is complex. Disclosure of Invention The invention aims to improve the compacted density and the electrical conductivity of lithium iron phosphate. According to the method, the ion diffusion rate in the lithium iron phosphate is improved through doping of two metal ions, the compaction density of the material is improved through phosphoric acid pretreatment, and the method is simple in process flow, environment-friendly in synthetic material and easy to industrially develop. The method for solving the problems is realized by the following technical scheme: putting a lithium source, an iron source, a phosphorus source, a carbon source, a titanium source and a vanadium source into a sand mill by taking deionized water as a solvent for sand milling; step (2), sand grinding to a certain particle size and then taking out the slurry; step (3), spray drying the slurry obtained in the step (2) to obtain yellow materials; Step (4), placing the yellow material in the step (3) into an inert atmosphere tube furnace for primary calcination to obtain a lithium iron phosphate precursor; Placing the lithium iron phosphate precursor in the step (4) into phosphoric acid solution for aging for a certain time, and performing suction filtration and drying to obtain black powder; And (6) carrying out secondary calcination on the black powder obtained in the step (5) in an inert atmosphere to obtain the lithium iron phosphate anode material. Specifically, the iron source used in the step (1) is one or more of ferrous sulfate, ferrous oxalate, ferrous chloride and ferric phosphate; specifically, the lithium source used in the step (1) is one of lithium hydroxide, lithium carbonate, lithium bicarbonate and lithium dihydrogen phosphate, and the lithium is fed according to the ratio of lithium to iron=1.02-1.06:1; Specifically, in the step (1), the carbon source is one or more of glucose, sucrose, fructose, polyethylene glycol and tannic acid, and the feeding is carried out according to the carbon content of iron=0.3-0.5:1; specifically, in the step (1), the titanium source is one or more of titanium dioxide and tetrabutyl titanate, and the titanium is fed according to the molar ratio of iron=0.008-0.03:1; Specifically, in the step (1), the vanadium source is one or more of ammonium metavanadate, vanadium pentoxide and vanadyl oxalate, and the feeding is carried out according to the molar ratio of vanadium to iron=0.001-0.006:1; Specifically, deionized water in the step (1) is added according to the solid content of 35% -50%. Specifically, in the step (2), the particle size D50 is 300-500nm. Specifically, the drying temperature in the step (3) is 75-85 ℃. Specifically, in the step (4), the calcining condition is 300-400 ℃, the heating rate is 2-5 ℃ per minute, the heat preservation time is 1-2h, and the protective gas is one of N 2 and Ar. Specifically, the phosphoric acid concentration in the step (5) is 50% -75%, and 85% phosphoric acid is mixed with a certain amount of water to prepare the lithium iron phosphate precursor; specifi