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Porous spherical core-shell structure silicon-carbon composite material and preparation method thereof and lithium ion battery

A silicon-carbon composite material, porous spherical technology, applied in battery electrodes, secondary batteries, structural parts, etc., can solve problems such as low charging and discharging efficiency, consumption of electrolyte, silicon active material and current collector shedding, etc. The effect of packing and tapping density, improving volume energy density, and novel morphology and structure

Inactive Publication Date: 2019-01-11
桑顿新能源科技(长沙)有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] However, there are two biggest problems with silicon-based anode materials in practical applications: 1. The volume change is as high as 300% during the charging and discharging process. The mechanical force generated by such a huge volume effect makes the silicon material itself pulverize on the one hand. , it is difficult to form a stable SEI film on the surface, thereby continuously consuming the electrolyte, resulting in low charge and discharge efficiency; on the other hand, the silicon active material and the current collector are detached and lose activity, resulting in capacity decay and poor cycle performance
2. Silicon itself is a semiconductor material, and the intrinsic conductivity of the material is low, only 10 -4 The order of S / cm affects the rate performance and capacity of the material
However, this patent uses a hydrothermal method for carbon coating, and the obtained material morphology is random, and it is difficult to obtain a uniform and stable morphology. At the same time, the number of pores formed by this method is small and the pore size is small, and subsequent etching and cleaning are difficult. , the final hydrothermal method requires high temperature and high pressure environment, relatively high requirements on equipment, difficult to continuous production, poor consistency between batches

Method used

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  • Porous spherical core-shell structure silicon-carbon composite material and preparation method thereof and lithium ion battery
  • Porous spherical core-shell structure silicon-carbon composite material and preparation method thereof and lithium ion battery
  • Porous spherical core-shell structure silicon-carbon composite material and preparation method thereof and lithium ion battery

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Embodiment 1

[0045] Such as figure 1 As shown, the preparation method of the silicon-carbon composite material in this embodiment, the steps are as follows:

[0046] S1. Prepare raw materials, take 50g of 100nm nano-silicon powder, and heat it at 400°C for 3 hours in an air atmosphere to obtain Si / SiO with the surface layer oxidized 2 Nanoparticles were added to 100 g of N,N-dimethylformamide (DMF) solution and 0.05 g of sodium dodecylbenzenesulfonate was added for ultrasonic dispersion to obtain a mixed solution 1.

[0047] S2. Add 200g polyacrylonitrile (PAN) to 500g N,N-dimethylformamide (DMF) solution, heat and dissolve at 70°C until it becomes a homogeneous liquid, then add 50g polymethyl methacrylate (PMMA), continue to stir and use Heating with residual heat until completely dissolved to obtain mixed solution 2;

[0048] The mass ratio of nano silicon powder: organic dispersant: polymer 1: polymer 2: solvent is 1:0.001:4:1:12;

[0049] S3. Add the mixed solution 1 of step S1 into...

Embodiment 2

[0052] The preparation method of the silicon-carbon composite material of this embodiment, its steps are as follows:

[0053] S1. Take 40g of 800nm ​​nano-silicon powder and heat it at 600°C for 1h in an air atmosphere to obtain Si / SiO whose surface layer is oxidized 2 Nanoparticles were added to 100 g of tetrahydrofuran solution and 0.05 g of triethylhexyl phosphoric acid was added for ultrasonic dispersion to obtain mixed solution 1.

[0054] S2. Add 200 g of polyvinylidene fluoride to 500 g of tetrahydrofuran solution, heat and dissolve at 100° C. to a homogeneous liquid, then add 30 g of polyethylene glycol, continue stirring and use residual heat to heat until completely dissolved, and obtain mixed solution 2;

[0055] Nano silicon powder: organic dispersant: polymer 1: polymer 2: the mass percentage of solvent is 1: 0.00125: 4: 0.75: 15;

[0056] S3. Add the mixed solution 1 of step S1 into the mixed solution 2 obtained in step S2, fully stir and disperse to obtain the ...

Embodiment 3

[0059] The preparation method of the silicon-carbon composite material of this embodiment, its steps are as follows:

[0060] S1. Take 60g of 20nm nano-silicon powder and heat it at 350°C for 10h in an air atmosphere to obtain Si / SiO whose surface layer is oxidized 2 Nanoparticles were added to 100 g of dimethyl sulfoxide solution and 0.09 g of sodium dodecylbenzenesulfonate was added for ultrasonic dispersion to obtain a mixed solution 1.

[0061] S2. Add 300g of polyamide to 500g of dimethyl sulfoxide solution, heat and dissolve at 60°C until it becomes a homogeneous liquid, then add 60g of ethylene-vinyl acetate copolymer, continue to stir and heat until completely dissolved with residual heat, and obtain mixed solution 2;

[0062] Nano silicon powder: organic dispersant: polymer 1: polymer 2: the mass percentage of solvent is 1:0.0015:5:1:10;

[0063] S3. Add the mixed solution 1 of step S1 into the mixed solution 2 obtained in step S2, fully stir and disperse to obtain t...

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Abstract

The invention relates to a porous spherical core-shell structure silicon-carbon composite material and a preparation method thereof and a lithium ion battery. The method comprises the following stepsof: preparing a mixed solution of Si / SiO2 nanoparticles by S1; S2 preparing a mixed solution 2 of polymer 1 and polymer 2; S3 spray precursor spherical Si / SiO2 / polymer composites; SiO2 / C composites with porous spherical core-shell structure are prepared by sintering Si / SiO2 / C composites and then etching SiO2 layer with strong acid to remove SiO2 layer. In the invention, two polymers with differentthermal decomposition temperatures are firstly heated in air to burn off the polymer with low thermal decomposition temperature to form nano pores, and then high-temperature carbonization is carriedout in an inert gas, which is different from the pores formed by natural carbonization using a single carbon source. The silicon-carbon composite material obtained by the invention is a multi-core shell structure spherical agglomerate, and has obvious nano holes on the surface, small specific surface area and high vibration density. The charge-discharge capacity and cycle performance of the lithium ion battery using the silicon-carbon composite material are obviously improved.

Description

technical field [0001] The invention relates to a silicon-carbon composite material and its preparation method and application, in particular to a silicon-carbon composite material with a porous spherical core-shell structure, its preparation method and a lithium ion battery, belonging to the technical field of lithium ion battery negative electrode material preparation. technical background [0002] With the continuous development of lithium-ion battery technology, there are many kinds of commercial positive electrode materials, but the commercial negative electrode materials still use graphite-like carbon negative electrode materials. Although the volume change of graphite-based materials is small and the structure is stable during charging and discharging, the inherent theoretical specific capacity of graphite is only 372mAh / g. In addition, it is easy to decompose lithium under fast charging and low temperature, which has serious safety problems. To a certain extent, the ...

Claims

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Application Information

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IPC IPC(8): H01M4/36H01M4/38H01M4/583H01M10/0525
CPCH01M4/362H01M4/386H01M4/583H01M10/0525H01M2004/021Y02E60/10
Inventor 陈韬王长伟李东南商士波汪紫煌殷磊彭子良
Owner 桑顿新能源科技(长沙)有限公司
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