Silicon/graphite composite anode material and preparation method thereof

A negative electrode material and graphite technology, which is applied in the field of silicon/graphite composite negative electrode material and its preparation, can solve the problems of unstable SEI film and low coulombic efficiency of negative electrode materials, so as to avoid thickness growth, improve coulombic efficiency and cycle stability, The effect of improving stability

Active Publication Date: 2015-01-28
CHERY AUTOMOBILE CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] In the cycle process, the anode materials provided by the prior art tend to form an unstable and gradually thickened SEI film, resulting in low Coulombic efficiency of the anode materials

Method used

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  • Silicon/graphite composite anode material and preparation method thereof

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preparation example Construction

[0030] On the one hand, an embodiment of the present invention provides a method for preparing a silicon / graphite composite negative electrode material, the method comprising the following steps:

[0031] Step 101, putting the mixture of elemental silicon particles and graphite in a ball mill for ball milling to obtain a ball milled product.

[0032] In the embodiment of the present invention, graphite with a small specific surface area is selected as a material for buffering the volume effect of silicon. Through ball milling, the silicon particles are nano-dispersed in the graphite sheet structure and are in contact with the graphite sheet structure. Therefore, the lamellar structure of graphite and the gaps between nano-dispersed silicon particles can provide a large number of channels for lithium ions, increase the insertion position of lithium ions, so as to achieve the purpose of buffering the volume effect of silicon materials and effectively improve the preparation. Cy...

Embodiment 1

[0059] This embodiment provides a silicon / graphite composite negative electrode material, the preparation steps of which are as follows:

[0060] Mix 1.0 g of silicon powder (150 nm in particle size) and 4.0 g of artificial graphite (10 μm in particle size), put them into a planetary ball mill, and ball mill at 300 rpm for 4 hours to obtain a ball milled product. The ball-milled product was put into a mixed solution consisting of 10ml of ammonia (25% mass fraction), 10ml of hydrogen peroxide (30% mass fraction) and 50ml of water, heated to boiling, and stirred for 30min in a boiling state. Then the ball-milled product was taken out, washed with water, filtered and vacuum-dried at 80° C. for 12 hours to obtain a dry product. Add 4.0 g of the dried product to an absolute ethanol solution containing 0.06 g of a silane coupling agent (γ-glycidyl etheroxypropyltrimethylsilane) (wherein the mass of absolute ethanol is 20 g), at 50° C. Heat and stir for 30min. Then, slowly add 5 g ...

Embodiment 2

[0065] This embodiment provides a silicon / graphite composite negative electrode material, the preparation steps of which are as follows:

[0066] Mix 1.0 g of silicon powder (with a particle size of 5 μm) and 10.0 g of natural graphite (with a particle size of 25 μm), put them into a planetary ball mill, and ball mill at 400 rpm for 16 hours to obtain a ball milled product. 10g of this ball mill product was put into a mixed solution consisting of 20ml of ammonia (25% mass fraction), 20ml of hydrogen peroxide (30% mass fraction) and 100ml of water, heated to boiling, and stirred for 60min in a boiling state. Then the ball-milled product was taken out, washed with water, filtered and vacuum-dried at 120° C. for 2 hours to obtain a dried product. Add 8.0 g of this dry product to an absolute ethanol solution containing 0.008 g of a silane coupling agent (3-(N,N-dimethylaminopropyl)-aminopropylmethyldimethoxysilane) (wherein, The mass of absolute ethanol is 40 g), heated and stirr...

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Abstract

The invention discloses a silicon / graphite composite anode material and a preparation method thereof, belonging to the field of a lithium ion battery anode material. The method comprises the following steps: ball milling the mixture of monomer silicon particles and graphite by utilizing a ball mill to obtain a ball mill product; carrying out surface hydroxylation treatment on the ball mill product, so that the surface of each monomer silicon particle in the ball mill product is combined with a hydroxyl to obtain a hydroxylation product; processing the hydroxylation product by utilizing a silane coupling agent, so that organic functional groups in the silane coupling agent modify the monomer silicon particle surface in the hydroxylation product to obtain the silicon / graphite composite anode material. In the primary cycling process of the anode material, an SEI membrane formed on the surface of the silicon particle is intersected with the organic functional groups on the surface of the silicon particles, so that the stability of the SEI membrane is improved, the thickness increment of the SEI membrane is avoided, and the coulombic efficiency and cycling stability of the prepared anode material can be effectively improved.

Description

technical field [0001] The invention relates to the field of negative electrode materials for lithium ion batteries, in particular to a silicon / graphite composite negative electrode material and a preparation method thereof. Background technique [0002] Lithium battery (that is, lithium ion battery) is a rechargeable battery that uses carbon active material as the negative electrode and a lithium-containing compound as the positive electrode. The charging and discharging process is the intercalation and deintercalation process of lithium ions: when charging, lithium ions are deintercalated from the positive electrode, pass through the electrolyte and separator, and embed in the negative electrode. The more lithium ions are embedded in the negative electrode, the higher the specific charge capacity of the battery On the contrary, during discharge, lithium ions are deintercalated from the negative electrode, pass through the electrolyte and separator, and intercalate into the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M4/133H01M4/134H01M4/38H01M4/583
CPCH01M4/133H01M4/134H01M4/386H01M4/583Y02E60/10
Inventor 赵志刚刘三兵海滨
Owner CHERY AUTOMOBILE CO LTD
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