Method for preparing Si/C composite cathode material of lithium ion battery

A technology for lithium-ion batteries and negative electrode materials, applied in battery electrodes, circuits, electrical components, etc., can solve the problems of limiting the large-scale practical application of silicon-based materials, material morphology changes, and poor cycle performance, and achieve good cycle stability. And the effect of rate performance, cohesion enhancement and excellent performance

Active Publication Date: 2013-05-01
CENT SOUTH UNIV
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  • Abstract
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Problems solved by technology

However, pure silicon materials have very significant volume expansion (>300%) during the process of high lithium intercalation, the electrode materials will gradually pulverize, the alloy structure is destroyed, and the separation between silicon particles and the conductive network occurs, causing serious morphological changes in the material. , the internal resistance of the electrode increases, the capacity decreases, and the cycle performance deteriorates, which limits the large-scale practical application of silicon-based materials.

Method used

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  • Method for preparing Si/C composite cathode material of lithium ion battery
  • Method for preparing Si/C composite cathode material of lithium ion battery
  • Method for preparing Si/C composite cathode material of lithium ion battery

Examples

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Embodiment 1

[0031] Dissolve the phenolic resin (calculated according to the content of pyrolytic carbon in the composite material after sintering) in an appropriate amount of absolute ethanol, then add an appropriate proportion of nano-silica powder and graphite to the solution, stir for 2 hours, and mix the solution evenly at 80 Evaporate and solidify at ℃. After the solvent is completely volatilized, a bulk precursor will be obtained. After drying, it will be calcined at 800℃ for 2 hours under the protection of high-purity argon, and then cooled with the furnace to obtain a Si / C composite material. Mix the synthesized Si / C composite material, conductive carbon black (SuperP) and binder (PVDF) at a mass ratio of 8:1:1, add N-methylpyrrolidone (NMP) to make a slurry, and coat it evenly On the copper foil, dry at 120°C to prepare a negative electrode sheet with Φ=14mm, heat treatment at 230°C for 3 hours under the protection of high-purity argon, and cool down with the furnace to obtain the...

Embodiment 2

[0035]Dissolve glucose (calculated according to the content of pyrolytic carbon in the composite material after sintering) in an appropriate amount of deionized water, use hexadecyl ammonium bromide as a dispersant, and then add an appropriate proportion of nano-silica powder and graphite to the solution. After stirring for 2 hours, the uniformly dispersed suspension was spray-dried at 170-200°C to obtain the composite material precursor. The obtained precursor was calcined at 800° C. for 2 h under the protection of high-purity argon, and cooled with the furnace to obtain a Si / C composite material. The synthesized Si / C composite material, conductive carbon black (Super P) and binder (PVDF) were uniformly mixed at a mass ratio of 8:1:1, and NMP was added to make a slurry, which was evenly coated on copper foil. Dry at 120°C to prepare a negative electrode sheet with Φ=14mm, heat treatment at 230°C for 3 hours under the protection of high-purity argon, and cool in the furnace to...

Embodiment 3

[0037] Add pure nano-silica powder to 2% hydrogen fluoride aqueous solution, add an appropriate amount of silver nitrate at the same time, stir evenly, transfer it to a centrifuge tube for ultrasonic dispersion, and then collect the silicon powder by high-speed centrifugation, and then use absolute ethanol Wash the collected silicon powder several times with deionized water, so that the nano-silicon is separated from the migration solvent, and after vacuum drying, the etching-treated nano-silicon is obtained. Comparison of morphology before and after nano-silicon etching figure 2 shown. Dissolve citric acid (calculated according to the pyrolytic carbon content in the composite material after sintering) in an appropriate amount of deionized water, use absolute ethanol as a dispersant, and then add an appropriate proportion of etched nano-silicon powder and graphite to the solution , magnetically stirred for 2 hours, mixed evenly, and the uniformly dispersed suspension was spr...

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Abstract

The invention discloses a method for preparing a Si / C composite cathode material of a lithium ion battery. The method is characterized in that through a liquid phase solidification-high temperature pyrolysis-low temperature treatment combined method, the Si / C composite cathode material having good cycling stability and good rate capability is prepared. Concretely, the method comprises the following steps of uniformly dispersing a silicon source (before or after etching) and graphite in an appropriate solvent in the presence of a second-type additive with control of a temperature to obtain a solid precursor after the solvent is volatilized completely, transferring the solid precursor into a protective atmosphere, carrying out pyrolysis at a high temperature so that the carbon source is pyrolyzed into amorphous carbon and forms a coating layer, carrying out furnace cooling to obtain the Si / C composite cathode material, uniformly mixing the Si / C composite cathode material, a conductive agent and a binder, coating the mixture on a pole piece, carrying out drying, carrying out low-temperature treatment, and carrying out an electrochemical performance test. The method is simple and feasible and has a high practical degree. The Si / C composite cathode material prepared by the method has a high capacity and good cycling stability and a good rate capability after the low-temperature treatment.

Description

technical field [0001] The invention belongs to the field of lithium-ion battery materials and preparation methods thereof, and relates to a lithium-ion battery silicon-carbon composite negative electrode material and a preparation method thereof. Background technique [0002] Lithium-ion batteries are widely used in various portable electronic devices and electric vehicles due to their inherent advantages, such as portability, high capacity, and small size. At present, commercial lithium-ion secondary batteries generally use various carbon materials as negative electrodes, mainly graphitized carbon and amorphous carbon, such as natural graphite, modified graphite, graphitized mesocarbon microspheres, soft carbon (such as coke) and some hard carbon etc. However, such materials have low specific capacity (such as graphite theoretical capacity 372mAh g -1 ), prone to organic solvent co-intercalation and other shortcomings, and cannot meet the needs of high energy density bat...

Claims

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Application Information

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IPC IPC(8): H01M4/38H01M4/583
CPCY02E60/12Y02E60/10
Inventor 王志兴苏明如郭华军李新海黄思林甘雷彭文杰张云河胡启阳
Owner CENT SOUTH UNIV
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