Multilayer silicon/graphene composite lithium battery positive electrode material and preparation method thereof

Abstract

The invention belongs to the technical field of energy materials, provides a multilayer silicon / graphene composite lithium battery positive electrode material and a preparation method thereof, and aims to overcome the defects that a silicon cathode has an intense volume effect in the electrochemical lithium storage process, a stable surface solid electrolyte membrane is hard to form and the electric circulation performance is poor as the intrinsic conductivity of the silicon cathode self is low. The multilayer silicon / graphene composite lithium battery positive electrode material provided by the invention comprises foamed nickel, graphene layers and silicon layers, wherein the graphene layers and the silicon layers are arranged on the foamed nickel alternatively; the most top layer is a graphene layer. As a multilayer 'graphene / silicon / graphene'sandwich structure is formed, and silicon powder is wrapped in a layer manner by virtue of high mechanical properties and high conductivity of the graphene, great volume change of the silicon powder in the charge / discharge process can be effectively inhibited, a stable SEI (Solid Electrolyte Interface) membrane can be formed, and the multiplying power property and the circulation stability are improved on premise that a high specific capacity of silicon is maintained; meanwhile, the preparation method of the material is simple in process, low in cost and good in repeatability.

Description

technical field [0001] The invention belongs to the technical field of energy materials, and relates to a lithium battery negative electrode material and a preparation method thereof, in particular to a nickel foam collector multilayer silicon / graphene composite lithium battery negative electrode material and a preparation method thereof. Background technique [0002] The development of green energy technology and low-carbon economy has put forward higher and higher requirements for the next generation of high-performance lithium-ion batteries. In terms of anode materials, the current commercial lithium-ion batteries mainly use graphite-based carbon anode materials; however, graphite The theoretical specific capacity is only 372mAh g -1 , and the potential platform of lithium intercalation is close to metal lithium, and the phenomenon of "lithium separation" is prone to occur during fast charging or low-temperature charging, causing potential safety hazards; materials to re...

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Problems solved by technology

[0002] The development of green energy technology and low-carbon economy has put forward higher and higher requirements for the next generation of high-performance lithium-ion batteries. In terms of anode materials, the current commercial lithium-ion batteries mainly use graphite-based carbon anode materials; however, graphite The theoretical specific capacity is only 372mAh g -1 , and the potential platform of lithium intercalation is close to metal lithium, and the phenomenon of "lithium separation" is prone to occur during fast charging or low-temperature charging, causing potential safety hazards; materials to replace graphite-like carbon anodes

[0003] Among various anode materials, silicon has attracted the attention of more and more researchers with its obvious advantages and potential. The theoretical lithium storage capacity of silicon is as high as 4200mAh g -1 , more than 10 times the capacity of graphite, and has the highest capacity among elements that can be alloyed to store lithium; the voltage platform of silicon is slightly higher than that of graphite, and it is difficult to cause the phenomenon of "lithium precipitation" on the surface during charging, and its safety performance is better than that of graphite negative electrode material; in addition, silicon is one of the most abundant elements in the earth’s crust, with a wide range of sources, low price, and suitable for industrial production; however, there are still many problems with silicon as the negative electrode of the next generation lithium-ion battery: first, in the electrochemical storage of lithium In the process, silicon atoms combine with lithium atoms to obtain Li 4.4 In the silicon alloy phase, the volume expansion of the material reaches more than 300%. The mechanical force generated by the huge volume effect will gradually separate the electrode active material from the current collector and the silicon active phase itself will also be pulverized, thus losing the connection with the current collector. The electrical contact of the fluid causes a rapid decline in the cycle performance of the electrode; second, silicon itself is a semiconductor material with a low intrinsic conductivity of only 6.7·10 -4 S cm -1 , it is necessary to add a conductive agent to improve the electronic conductance of the electrode; third, the LiPF in the existing electrolyte 6 Decomposition produces a small amount of HF that corrodes silicon, causing the capacity of the silicon-based negative electrode to fade, and, due to its severe volume effect, silicon in conventional LiPF 6 It is difficult to form a stable surface solid electrolyte (SEI) film in the electrolyte. Along with the destruction of the electrode structure, new SEI films are continuously formed on the newly exposed silicon surface, resulting in reduced charge and discharge efficiency and increased capacity fading

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