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Composite lithium manganese silicate cathode material and preparation method thereof

A positive electrode material, lithium manganese silicate technology, applied in the field of positive electrode materials for lithium-ion batteries, can solve the problems of low electronic conductivity, poor structural stability, poor electrochemical performance, etc., and achieve uniform microscopic appearance and good electrochemical performance Effect

Active Publication Date: 2018-05-29
SHENZHEN GRADUATE SCHOOL TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] Aiming at the problems of low electron conductance and poor structural stability of lithium manganese silicate, which lead to poor electrochemical performance, the present invention provides a composite lithium manganese silicate positive electrode material and a preparation method thereof

Method used

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  • Composite lithium manganese silicate cathode material and preparation method thereof
  • Composite lithium manganese silicate cathode material and preparation method thereof
  • Composite lithium manganese silicate cathode material and preparation method thereof

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preparation example Construction

[0033] In one embodiment, a method for preparing a composite lithium manganese silicate positive electrode material, comprising: uniformly mixing reactants other than lithium sources and carbon sources, and performing the first step of carbon coating by hydrothermal reaction to prepare precursors After the hydrothermal reaction, the carbon source is used to carry out the second step of carbon coating on the precursor to obtain an intermediate product; the intermediate product after the second step of carbon coating is mixed with lithium (such as ball milling mixed with lithium), and heat treated A final product is obtained; wherein the reactants other than the lithium source include a manganese source and a silicon source. By introducing two-step carbon coating and doping with equivalent metal ions, Pmn2 uniformly coated with amorphous carbon layer and doped with a small amount of equivalent metal ions is obtained. 1 Orthorhombic lithium manganese silicate nanoparticles have u...

example 1

[0045] Measure and mix absolute ethanol and water with a volume ratio of 5:1, add an appropriate amount of ammonia water to adjust the pH value, add an appropriate amount of starch (10% of the mass of the base material), and add according to the molar ratio of manganese and silicon elements of 1.0:1.0 Manganese acetate and tetraethyl orthosilicate, continuously magnetically stirred for 4 hours until the solution is fully hydrolyzed and mixed evenly. At this time, the mixed solution is dark black. Put it in a hydrothermal reaction kettle and react at 150°C for 24 hours. The second step Carbon coating Ultrasonic dispersion of the hydrothermal precursor, and uniformly added to the fully gelatinized starch sol (20% of the mass of the matrix material), in a water bath at 70 ° C for 4 hours and magnetic stirring until fully mixed, and then the coated Add an appropriate amount of lithium carbonate to the precursor, ball mill for 10 hours at a speed of 450 rpm, and finally dry the mixt...

example 2

[0050] Measure and mix absolute ethanol and water with a volume ratio of 5:1, add an appropriate amount of ammonia water to adjust the pH value, add an appropriate amount of starch (15% of the mass of the base material), and adjust the molar ratio of manganese, silicon, and nickel to 0.95 :1.00:0.05 Add manganese acetate, ethyl orthosilicate, nickel acetate, and continue magnetic stirring for 4 hours until the solution is fully hydrolyzed and mixed evenly. At this time, the mixed solution is dark black. Place it in a hydrothermal reaction kettle at 150°C The second step of carbon coating is to ultrasonically disperse the hydrothermal precursor, and evenly add it to the fully gelatinized starch sol (15% of the mass of the matrix material), and place it in a water bath at 80°C for 2 hours and magnetically stir until fully Mix, then add an appropriate amount of lithium acetate to the coated precursor, ball mill for 8 hours at a speed of 400 rpm, and finally dry the mixture, and ke...

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Abstract

The invention relates to a composite lithium manganese silicate cathode material and a preparation method thereof. The preparation method comprises the steps of uniformly mixing reactants outside a lithium source with a carbon source, and carrying out first-step carbon coating by a hydrothermal reaction so as to prepare a precursor; after the hydrothermal reaction, carrying out second-step carbon coating on the precursor with the carbon source so as to obtain an intermediate product; and carrying out lithium mixing on the intermediate product obtained after the second-step carbon coating, and by heat treatment, obtaining a final product, wherein the reactants apart from the lithium source comprise a manganese source and a silicon source. The polyanionic cathode material has a Pmn21 orthorhombic structure; a chemical formula of the material is Li2Mn1-xMxSiO4 (M=Fe, Cr and Ni, and x is greater than or equal to 0 and smaller than or equal to 0.1); and after carbon coating and equivalent metal ion doping modification, the composite lithium manganese silicate cathode material consists of a base material and amorphous carbon coated on the surface of the base material. By the method disclosed by the invention, the Pmn21 orthorhombic lithium manganese silicate nano particles which are uniformly coated with the amorphous carbon layer and doped with a small number of equivalent metal ions can be obtained, and show uniform micrograph morphology and excellent electrochemical performance.

Description

technical field [0001] The invention relates to a positive electrode material of a lithium ion battery, in particular to a composite lithium manganese silicate positive electrode material and a preparation method thereof. Background technique [0002] Lithium manganese silicate, as a polyanion cathode material for lithium-ion batteries, has become a research hotspot due to its significant advantages such as high theoretical capacity (~333mAh / g), low cost, good thermal stability, and environmental affinity. At the same time, there are also some problems that need to be solved urgently in this material, such as the extremely low electronic conductivity (~10 -16 S cm -1 ); poor cycle stability; low actual discharge capacity and difficulty in synthesizing pure phases. [0003] The crystal structure of lithium manganese silicate contains four different space groups, which are the orthorhombic Pmn2 1 , Pmnb and monoclinic P2 1 / n, Pn. Since the preparation of the monoclinic p...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M4/36H01M4/58H01M4/62H01M10/0525B82Y30/00
CPCB82Y30/00H01M4/366H01M4/5825H01M4/625H01M10/0525Y02E60/10
Inventor 赵世玺邓晖吴霞魏雷
Owner SHENZHEN GRADUATE SCHOOL TSINGHUA UNIV
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