Lithium ferrous silicate anode material coated with crystalline carbon and preparation method thereof

A technology of lithium ferrous silicate and positive electrode materials, which is applied in the direction of battery electrodes, structural parts, electrical components, etc., can solve the problems of reducing the volumetric energy density of positive electrode materials, low tap density of products, and poor particle contact performance. Improved electrochemical performance, fine grain size, and high powder purity

Inactive Publication Date: 2011-10-05
TIANJIN UNIV
5 Cites 19 Cited by

AI-Extracted Technical Summary

Problems solved by technology

Although Chinese patent 101841016A uses crystalline carbon nanotubes as a carbon source to obtain crystalline carbon-coated Li 2 FeSiO 4 powder, but because carbon nanotubes and precursors are only mechanically mixed, the tap density of the product is not high, carbon and Li 2 FeS...
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Abstract

The invention relates to a high-purity lithium ferrous silicate anode material coated with crystalline carbon and a preparation method thereof. In the lithium ferrous silicate anode material coated with the crystalline carbon, the particle diameter of powder is 50-350 nm, and the initial discharge capacity of the anode material at the rate of C/16 is 125.7-150.3 mAhg<-1>, the weight percent of carbon is 5-15 percent by weight; a Li2FeSiO4 precursor is prepared by using a sol-gel method which comprises the following steps of: with ascorbic acids as reductants and carbon sources, catalyzing by Fe(NO3)3 while reducing ferric ions to form crystalline graphite; and uniformly coating on surfaces of Li2FeSiO4 particles, thus, the electrical property of the Li2FeSiO4/C anode material is effectively improved. Taking a carbon coating amount of 10.1 percent by weight as an example, the synthesized powder has high purity and is free of impurity phases; the initial discharge capacity at the rate of C/16 is 150.3 mAhg<-1>; and after circulation forty times, the specific ratio is 137.2 mAhg<-1>, which embodies better rate performance and better circulation performance.

Application Domain

Technology Topic

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  • Lithium ferrous silicate anode material coated with crystalline carbon and preparation method thereof
  • Lithium ferrous silicate anode material coated with crystalline carbon and preparation method thereof
  • Lithium ferrous silicate anode material coated with crystalline carbon and preparation method thereof

Examples

  • Experimental program(5)

Example Embodiment

[0022] Example 1:
[0023] Using lithium acetate dihydrate, ferric nitrate, and ethyl orthosilicate as raw materials, weigh the corresponding substances according to the molar ratio of the substances to make the molar ratio of Li:Fe:Si 2:1:1, and measure 1.8ml of ethyl orthosilicate Ester was added to 15ml of ethanol with constant stirring, 0.32ml of acetic acid was added dropwise, 1.640g of lithium acetate was accurately weighed and added to the above mixed solution, after dissolution, 3.256g of ferric nitrate was added, 1.057g of ascorbic acid was mixed into a saturated aqueous solution and added dropwise to In the above-mentioned mixed solution, the mixed solution is transferred to a reaction kettle and reacted at 120°C for 20 hours to obtain a gel mixture, which is then dried in a drying box at 60°C to obtain a dry gel. The dry gel is crushed, pressed into tablets, in N 2 Under the protection of the atmosphere, calcined at 650°C for 10 hours to obtain carbon-coated lithium iron silicate powder. Li 2 FeSiO 4 The XRD pattern of /C is as figure 1 As shown, the characteristic peak of XRD and standard Li 2 FeSiO 4 The diffraction peaks of the powder XRD pattern correspond. Among them, the peak near 26.5° is the diffraction peak of graphite (PDF# 65-6212), indicating that the coated carbon is crystalline graphite. Synthetic powder Li 2 FeSiO 4 /C looks like figure 2 As shown, the particle size is between 50 and 120 nm, and the carbon content is 10.1 wt.%. Li 2 FeSiO 4 The cycle curve of /C composite material is as Figure 5 As shown, under the C/16 rate, the initial discharge capacity is 150.3mAhg -1 After 40 cycles, the specific capacity is 137.2mAhg -1.

Example Embodiment

[0024] Example 2:
[0025] Using lithium acetate, ferric nitrate, and ethyl orthosilicate as raw materials, weigh the corresponding substances according to the molar ratio of the substances so that the molar ratio of Li:Fe:Si is 2:1:1, measure 1.8ml of ethyl orthosilicate and add In 10ml of ethanol with constant stirring, add 0.32ml of acetic acid dropwise, accurately weigh 1.640g of lithium acetate and add to the above mixture, after dissolution, add 3.256g of ferric nitrate, and 0.700g of ascorbic acid into a saturated aqueous solution, and add dropwise to the above mixture In the solution, the mixed solution is transferred to the reaction kettle and reacted at 120°C for 5 hours to obtain a gel mixture, which is then dried in a drying box at 60°C to obtain a dry gel. The dry gel is crushed, pressed into tablets, in N 2 Under the protection of the atmosphere, it was calcined at 650°C for 7 hours to obtain carbon-coated lithium iron silicate powder. Synthetic powder Li 2 FeSiO 4 The microstructure of /C is as image 3 As shown, the carbon content is 5.3 wt.%, and the particle size is between 70 and 150 nm. The charge-discharge test was carried out under the same conditions as in Example 1, and the initial discharge capacity was 125.7mAhg under C/16 rate -1.

Example Embodiment

[0026] Example 3:
[0027] Using lithium acetate dihydrate, ferric nitrate, and ethyl orthosilicate as raw materials, weigh the corresponding substances according to the molar ratio of the substances to make the molar ratio of Li:Fe:Si 2:1:1, and measure 1.8ml of ethyl orthosilicate The ester was added to 18ml of ethanol and kept stirring, 0.32ml of acetic acid was added dropwise, 1.640g of lithium acetate was accurately weighed and added to the above mixture, after dissolution, 3.256g of ferric nitrate was added, and 1.929g of ascorbic acid was mixed into a saturated aqueous solution and added dropwise to In the above-mentioned mixed solution, the mixed solution is transferred to a reaction kettle and reacted at 180°C for 5 hours to obtain a gel mixture, which is then dried in a drying box at 60°C to obtain a dry gel. The dry gel is crushed, pressed into tablets, in N 2 Under the protection of the atmosphere, calcined at 750°C for 10 hours to obtain carbon-coated lithium iron silicate powder. Synthetic Li 2 FeSiO 4 /C powder is assembled into a battery, and its AC impedance spectrum is as Figure 4 As shown, when the test frequency range is 0.1 Hz to 100 kHz and the test temperature is 25°C, the charge transfer resistance Rct is 255Ω. In this composite material, the carbon content is 14.6% by weight, and the particle size is between 100 and 200 nm. The charge and discharge test is carried out under the same conditions as in Example 1. The initial discharge capacity is 135.9mAhg at C/16 rate. -1.
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PUM

PropertyMeasurementUnit
Particle size50.0 ~ 350.0nm
Particle size70.0 ~ 150.0nm
tensileMPa
Particle sizePa
strength10

Description & Claims & Application Information

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