CN103000901A - Preparation method of high-capacity SiC negative electrode material - Google Patents

Abstract

The invention relates to the preparation of a negative electrode material of a lithium ion battery, and particularly relates to a preparation method of a high-capacity SiC negative electrode material. The method comprises the following steps of: (a) slowly adding a reaction precursor PVC (polyvinyl chloride) into a tetrahydrofuran solvent which is in a continuous stirring state to dissolve the PVC completely so as to obtain a solution; (b) slowly adding Si powder into the solution obtained in the step (a), and blending uniformly; (c) heating the solution obtained in the step (b) to obtain a mixture after the solvent is volatilized completely, and adding the mixture into a quartz reaction device; (d) placing the quartz reaction device into a high-temperature furnace, so as to enable the organic precursor to be pyrolyzed and carbonized; and (e) stopping the reaction to obtain the high-capacity SiC negative electrode material. The method provided by the invention can inhibit the volume change of Si during the deintercalation of lithium by coating a carbon layer on silicon particles, thereby controlling the volume change of an overall electrode within a reasonable range, improving the reversible capacity of the battery and improving the cycle performance.

Description

The preparation method of high power capacity silicon-carbon cathode material

Technical field

The present invention relates to the preparation of lithium ion battery negative material, specifically a kind of preparation method of high power capacity silicon-carbon cathode material.

Background technology

The widely used graphite-like carbon negative pole material of lithium ion battery capacity is lower, generally is no more than 360mAh/g, more and more has been difficult to meet the need of market; And the theoretical lithium storage content 4200mAh/g of silicon class material, and the removal lithium embedded voltage platform is low, becomes gradually desirable negative material study hotspot.But there is change in volume large (volumetric expansion is greater than 400%) in silicon based anode material in charge and discharge process, causes the silicon grain efflorescence of breaking, and breaks away from conductive network, and internal resistance sharply increases, and capacity is decayed rapidly, the defective that cycle performance is poor.

Summary of the invention

Technical problem to be solved by this invention is that the preparation method of the high power capacity silicon-carbon cathode material that a kind of capacity is high, cyclicity is good is provided.

The preparation method of high power capacity silicon-carbon cathode material of the present invention may further comprise the steps:

A. with precursors PVC(polyvinyl chloride) slowly add in the solvents tetrahydrofurane that constantly stirs, PVC is dissolved fully, form solution; Every gram PVC adds the 5-10ml oxolane;

B. silica flour is added slowly in the solution of step a acquisition, mix; The weight ratio of silicon and PVC is 1:3-1:5.5;

C. the solution that step b is obtained is heated to solvent and begins volatilization when constantly stirring, the mixture that obtains after the whole volatilizations of solvent moves in the quartz ampoule reaction unit, has inert gas to make protection gas in this device; Protective gas is the mist of 5% hydrogen and 95% argon gas;

D. the quartz reaction device is transferred in the high temperature furnace, be warming up to temperature with the heating rate of 5 ℃/min and reach 820 ℃, make the organic precursor pyrolysis charring, the reaction time is 6-7 hour; After reaction finished, reaction system was lowered the temperature naturally, continues to pass into protective gas in the whole course of reaction and takes reacting gas out of;

E. reaction finishes namely to obtain required high power capacity silicon-carbon cathode material.

The inventive method is passed through to coat one deck carbon on the silicon powder particle surface, thereby suppresses the change in volume of silicon when removal lithium embedded, and the change in volume of whole electrode is controlled within the zone of reasonableness, has improved the reversible capacity of battery, has improved cycle performance.

Embodiment

The preparation method's of high power capacity silicon-carbon cathode material of the present invention embodiment is as follows:

A. with precursors PVC(polyvinyl chloride) slowly add in the solvents tetrahydrofurane that constantly stirs, PVC is dissolved fully, form solution; Every gram PVC adds the 8ml oxolane;

B. silica flour is added slowly in the solution of step a acquisition, mix; The weight ratio of silicon and PVC is 1:4;

C. the solution that step b is obtained is heated to solvent and begins volatilization when constantly stirring, the mixture that obtains after the whole volatilizations of solvent moves in the quartz ampoule reaction unit, has inert gas to make protection gas in this device; Protective gas is the mist of 5% hydrogen and 95% argon gas;

D. the quartz reaction device is transferred in the high temperature furnace, be warming up to temperature with the heating rate of 5 ℃/min and reach 820 ℃, make the organic precursor pyrolysis charring, the reaction time is 6 hours; After reaction finished, reaction system was lowered the temperature naturally, continues to pass into protective gas in the whole course of reaction and takes reacting gas out of.

E. reaction finishes namely to obtain required high power capacity silicon-carbon cathode material.Material is pulverized in agate grinds, and sieving by 200 mesh standard sieves obtains the material of required particle diameter, for subsequent use.

The high power capacity silicon-carbon cathode material that the inventive method obtains, its testing result is as follows:

1. particle size distribution is apparent in view, and the material particle size size is about 47 ~ 53 μ m.

2. make reference electrode with metal lithium sheet, discharge and recharge first efficient greater than 98%.

3.2.5V detain the about 820mAh/g of the first discharge capacity of electric 0.2C, 50 times charge and discharge cycles also keeps later on more than 88% of first capacity.

Claims (1)

1. the preparation method of a high power capacity silicon-carbon cathode material is characterized in that: may further comprise the steps,

A. precursors PVC is slowly added in the solvents tetrahydrofurane that constantly stirs, PVC is dissolved fully, form solution; Every gram PVC adds the 5-10ml oxolane;

B. silica flour is added slowly in the solution of step a acquisition, mix; The weight ratio of silicon and PVC is 1:3-1:5.5;

C. the solution that step b is obtained is heated to solvent and begins volatilization when constantly stirring, the mixture that obtains after the whole volatilizations of solvent moves in the quartz ampoule reaction unit, has inert gas to make protection gas in this device; Protective gas is the mist of 5% hydrogen and 95% argon gas;

D. the quartz reaction device is transferred in the high temperature furnace, be warming up to temperature with the heating rate of 5 ℃/min and reach 820 ℃, make the organic precursor pyrolysis charring, the reaction time is 6-7 hour; After reaction finished, reaction system was lowered the temperature naturally, continues to pass into protective gas in the whole course of reaction and takes reacting gas out of;

E. reaction finishes namely to obtain required high power capacity silicon-carbon cathode material.