Carbon nanotube/graphene/silicon composite lithium battery negative electrode material and preparation method thereof

Abstract

The invention belongs to the technical field of energy materials, and provides a carbon nanotube / graphene / silicon composite lithium battery negative electrode material and a preparation method thereof, which are used to overcome the severe volume effect of the silicon negative electrode in the electrochemical lithium storage process and the difficulty in forming a stable lithium battery. The surface solid electrolyte membrane and its low intrinsic conductivity lead to its poor electrical cycling performance. The invention comprises nickel foam, and graphene layers and silicon blended carbon nanotube layers arranged alternately on the nickel foam, and the topmost layer is a graphene layer, and a thick graphene protective layer is also covered on the topmost graphene layer . The invention adopts the multi-layer structure of graphene layer alternating silicon / carbon nanotube composite layer, utilizes the high mechanical properties and high conductivity of graphene and carbon nanotube to carry out three-dimensional compounding of silicon powder, and maintains the premise of high specific capacity of silicon The negative electrode rate and cycle performance are greatly improved, and at the same time, the preparation method has the advantages of simple process, low cost and good repeatability.

Description

technical field [0001] The invention belongs to the technical field of energy materials and relates to a lithium battery negative electrode material, in particular to a carbon nanotube / graphene / silicon composite lithium battery negative electrode material and a preparation method thereof. Background technique [0002] Nowadays, with the development and progress of modern society, the supply and utilization of energy are indispensable. Worldwide energy shortage has become one of the urgent problems to be solved in the 21st century. For this reason, many researchers have been working on finding other green energy sources that can replace non-renewable fossil fuels, such as solar energy, wind energy, hydropower and so on. Unlike traditional fossil fuels, most of these green energy sources have uncontrollable and intermittent problems, so the storage and utilization of these energy sources will increase the cost; this also makes researchers pay attention to new energy storage sy...

AI Technical Summary

Problems solved by technology

However, if it is to be applied in the field of large-scale high-power systems such as plug-in hybrid electric vehicles (PHEV) or plug-in electric vehicles (PEV), the performance requirements for lithium-ion batteries have also been greatly improved, especially in terms of energy density. In terms of cycle life and safety issues, the materials and systems of lithium-ion batteries have yet to be further developed and improved.

Among various non-carbon anode materials, silicon has attracted the attention of more and more researchers with its unique 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, the voltage platform of silicon is slightly higher than that of graphite, 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 anode materials; in addition, silicon is one of the most abundant elements in the earth's crust. Wide range of sources and low price; however, there are still many problems with silicon as the negative electrode of next-generation lithium-ion batteries: First, in the process of electrochemical lithium storage, silicon atoms combine with lithium atoms to obtain Li 4.4 In the Si alloy phase, the volume expansion of the material reaches more than 300%. The mechanical force generated by the huge volume effect will gradually disengage 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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