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CN-116581270-B - Manganese and titanium in-situ doped carbon-containing lithium iron phosphate composite material and preparation method and application thereof

CN116581270BCN 116581270 BCN116581270 BCN 116581270BCN-116581270-B

Abstract

The invention provides a manganese and titanium in-situ doped carbon-containing lithium iron phosphate composite material, and a preparation method and application thereof, and belongs to the technical field of anode materials. The invention takes titanium white byproduct ferrous sulfate as a raw material, reduces ferric iron by using a reducing agent, removes part of titanium and other impurities by flocculation after adding alkali to obtain refined ferrous sulfate with certain manganese and titanium content, then adds phosphoric acid and alkali to oxidize to obtain ferric phosphate, finally mixes with a lithium source and a carbon source and calcines to obtain the manganese and titanium in-situ doped carbon-containing lithium iron phosphate composite material. According to the invention, manganese and titanium in the titanium white byproduct ferrous sulfate are not required to be completely removed, the titanium white byproduct ferrous sulfate is used as a doping element to be doped in situ, the preparation process is simpler, the uniform doping of a bulk phase is realized, the manganese and titanium double doping elements have a synergistic effect, and the performance of the composite material is improved. In addition, the carbon source is added to form a carbon material after calcination, so that the conductivity of the composite material is improved, and the electrochemical performance of the composite material is further improved.

Inventors

  • TU JIGUO
  • JIAO SHUQIANG

Assignees

  • 北京科技大学

Dates

Publication Date
20260512
Application Date
20230613

Claims (8)

  1. 1. The preparation method of the manganese and titanium in-situ doped carbon-containing lithium iron phosphate composite material comprises the following steps: (1) Mixing titanium white byproduct ferrous sulfate with water and a reducing agent for reduction reaction to obtain a reducing solution, wherein the mass ratio of the reducing agent to the titanium white byproduct ferrous sulfate is (0.5-2) 100; (2) Mixing the reducing solution obtained in the step (1) with alkali, and performing hydrolysis reaction to obtain a hydrolysis product, wherein the temperature of the hydrolysis reaction is 40-70 ℃, and the time of the hydrolysis reaction is 1-4 hours; (3) Mixing the hydrolysate obtained in the step (2) with a flocculating agent, and performing flocculation reaction to obtain a refined ferrous sulfate solution, wherein the mass content of manganese in the refined ferrous sulfate solution is 0.05-0.5%, and the mass content of titanium in the refined ferrous sulfate solution is 0.04-0.38%; (4) Mixing the refined ferrous sulfate solution obtained in the step (3) with phosphoric acid and alkali, and carrying out precipitation reaction to obtain an intermediate product; (5) Mixing the intermediate product obtained in the step (4) with an oxidant and an acid, and carrying out an oxidation reaction to obtain a precursor; (6) And (3) mixing the precursor obtained in the step (5) with a lithium source and a carbon source, and calcining to obtain the manganese and titanium in-situ doped carbon-containing lithium iron phosphate composite material.
  2. 2. The method according to claim 1, wherein the ratio of the amount of the phosphoric acid to the amount of the ferrous ion in the purified ferrous sulfate solution in the step (4) is 1 to 1.2:1.
  3. 3. The method according to claim 1, wherein the precipitation reaction time in the step (4) is 0.5 to 2 hours.
  4. 4. The method according to claim 1, wherein the ratio of the amount of the oxidizing agent in the step (5) to the amount of the iron in the intermediate product is (1.2 to 2.5): 1.
  5. 5. The preparation method according to claim 1, wherein the mass ratio of the carbon source to the precursor in the step (6) is (7-9.5): 100.
  6. 6. The method according to claim 1, wherein the ratio of the amount of lithium in the lithium source to the amount of iron in the precursor in step (6) is 1.02 to 1.1:1.
  7. 7. The manganese-titanium in-situ doped carbon-containing lithium iron phosphate composite material prepared by the preparation method of any one of claims 1-6.
  8. 8. The use of the manganese-titanium in-situ doped carbonaceous lithium iron phosphate composite material as a positive electrode material of a lithium ion battery according to claim 7.

Description

Manganese and titanium in-situ doped carbon-containing lithium iron phosphate composite material and preparation method and application thereof Technical Field The invention relates to the technical field of positive electrode materials, in particular to a manganese-titanium in-situ doped carbon-containing lithium iron phosphate composite material, and a preparation method and application thereof. Background The lithium iron phosphate anode material is the most suitable energy storage type lithium ion battery anode material at present because of the advantages of no rare resources such as cobalt, nickel and the like, long cycle life, good safety and the like. In order to prepare the lithium iron phosphate positive electrode material with excellent performance, in addition to strict control of production process and equipment, strict requirements are also imposed on the purity of raw materials, such as battery-grade lithium salt, phosphoric acid, high-purity iron source and the like. Millions of tons of byproduct ferrous sulfate are generated in the production process of titanium dioxide by the sulfuric acid method in China each year, and the ferrous sulfate contains a plurality of impurities, so that the existence of the impurities is widely considered to influence the structure and the characteristics of ferric phosphate, and further influence the performance of a battery. In order to synthesize the battery-grade anhydrous ferric phosphate, complex and complicated and high-cost procedures are required to remove impurities in raw materials, and high-temperature calcination is required to remove crystal water in ferric sulfate. On the other hand, in order to improve the performance of lithium iron phosphate, the incorporation of bulk doping elements into the crystal lattice of lithium iron phosphate during the subsequent synthesis process is an important method for improving ion transport characteristics. Although the production and doping processes of lithium iron phosphate are mature, and the conversion of titanium white byproduct ferrous sulfate to prepare lithium iron phosphate electrode materials is more, the conventional method is that impurities in the byproduct ferrous sulfate are removed, then high-temperature calcination and dehydration are carried out, and doping elements are added, so that the preparation method is complex and the uniformity of the materials is still to be improved. Therefore, how to simplify the process and improve the performance of lithium iron phosphate has become a problem in the prior art. Disclosure of Invention The invention aims to provide a manganese-titanium in-situ doped carbon-containing lithium iron phosphate composite material, and a preparation method and application thereof. The preparation method provided by the invention is simple in process, and the prepared manganese-titanium in-situ doped carbon-containing lithium iron phosphate composite material has excellent electrochemical performance. In order to achieve the above object, the present invention provides the following technical solutions: The invention provides a preparation method of a manganese-titanium in-situ doped carbon-containing lithium iron phosphate composite material, which comprises the following steps: (1) Mixing titanium white byproduct ferrous sulfate with water and a reducing agent for reduction reaction to obtain a reducing solution; (2) Mixing the reducing solution obtained in the step (1) with alkali, and carrying out hydrolysis reaction to obtain a hydrolysis product; (3) Mixing the hydrolysate obtained in the step (2) with a flocculating agent, and performing flocculation reaction to obtain a refined ferrous sulfate solution, wherein the mass content of manganese in the refined ferrous sulfate solution is 0.05-0.5%, and the mass content of titanium in the refined ferrous sulfate solution is 0.04-0.38%; (4) Mixing the refined ferrous sulfate solution obtained in the step (3) with phosphoric acid and alkali, and carrying out precipitation reaction to obtain an intermediate product; (5) Mixing the intermediate product obtained in the step (4) with an oxidant and an acid, and carrying out an oxidation reaction to obtain a precursor; (6) And (3) mixing the precursor obtained in the step (5) with a lithium source and a carbon source, and calcining to obtain the manganese and titanium in-situ doped carbon-containing lithium iron phosphate composite material. Preferably, in the step (1), the mass ratio of the reducing agent to the titanium white byproduct ferrous sulfate is (0.5-2) 100. Preferably, the hydrolysis reaction temperature in the step (2) is 40-70 ℃, and the hydrolysis reaction time is 1-4 hours. Preferably, the ratio of the amount of phosphoric acid in the step (4) to the amount of ferrous ion in the purified ferrous sulfate solution is (1-1.2): 1. Preferably, the time of the precipitation reaction in the step (4) is 0.5-2 hours. Preferably, the ratio of the oxidant in the step (5