Preparation method of lithium electron composite cathode material

Abstract

The invention discloses a preparation method of a lithium electron composite cathode material. The method comprises that natural graphite, nano silicon, calcined petroleum coke powder, calcined petroleum coke, calcined pitch coke and carbon black are mixed according to weight percentage and blended into a mixture; the mixture is mixed in a dry method to a uniform state, coal tar pitch is added toimplement mixing and pinching, and a composite plastic body wrapped in silicon is formed; the composite plastic body is roasted in a furnace at 800-1150 DEG C to prepare a carbon material; the carbonmaterial is processed at the high temperature of 2100-3100 DEG C in a graphitization furnace to prepare a carbon / graphite / silicon wrapping composite material; and the carbon / graphite / silicon wrappingcomposite material is crushed and spheroidized to obtain spherical or oval carbon / graphite / silicon wrapping cathode powder in the particle size of 5-26 micron, namely, the lithium electron composite cathode material is obtained. The prepared cathode material is high in specific capacity and low charging / discharging potential, includes a stable charging / discharging platform, and has a high compacting performance, high conducting performance, high magnification performance and long circulation performance.

Description

technical field [0001] The invention relates to the technical field of lithium battery materials, in particular to a preparation method of a lithium electron composite negative electrode material. Background technique [0002] With the warming of the global climate and the high price of oil, people are beginning to realize the importance of environmental protection and the seriousness of the energy crisis. In order to reduce the use of fossil fuels, reduce carbon dioxide emissions, and slow down the rate of global warming, governments and companies around the world began to seek new alternative energy sources (such as solar energy and fuel cells) on the one hand, and replaced lead-acid batteries with lithium-ion batteries on the other. , Ni-MH batteries to improve the conversion efficiency of secondary batteries. Up to now, the secondary battery industry has undergone structural changes, and lithium-ion batteries will gradually replace lead-acid batteries and nickel-metal h...

AI Technical Summary

Problems solved by technology

Its disadvantage is that the lithium intercalation potential is too low, and it is prone to lithium precipitation when polarization occurs, resulting in safety problems.

At the same time, its theoretical capacity is too low (372 mAhg -1 ), the rate performance is poor and it is difficult to meet the requirements of electric vehicles and high-capacity power storage for lithium-ion batteries

[0004] Si is a very promising anode material, which has the advantages of the highest theoretical capacity, low discharge voltage (~370 mVvs.Li / Li+), high abundance in the earth's crust, non-toxicity, etc. And there is no solvent co-intercalation problem similar to graphite. At present, the main problems restricting the application of Si as an anode material are as follows: First, Si has a volume expansion of nearly 400% during the alloying process with lithium, which makes the electrode material undergo repeated charging. During the discharge process, due to repeated expansion and contraction, the electrode material is pulverized and separated from the current collector, resulting in a rapid decline in the capacity of the electrode material; second, because of the "volume effect", its SEI film is very unstable. The SEI film formed on the Si surface undergoes a continuous "formation-fragmentation-re-formation at the fresh interface" process, and its SEI film continues to grow and thicken. When the thickness increases to a certain value, lithium ions cannot pass through. And it seriously consumes the lithium ions in the electrolyte, which seriously reduces the cycle stability of the lithium battery; the third is that the conductivity of Si is poor

This is because, as the size of the material decreases, the transport distance of lithium ions becomes less

Moreover, in the problem of poor electron and ion transport ability caused by the poor conductivity of Si, as the specific surface area of ​​the material increases, the material transport along the surface and grain boundary will be greatly enhanced.

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