Method for preparing lithium ion capacitor using carbon nanotube/urea-formaldehyde resin carbon coated spherical microcrystalline graphite material

Abstract

The invention relates to a method for preparing a lithium ion capacitor using a carbon nanotube / urea-formaldehyde resin carbon coated spherical microcrystalline graphite material. According to the method, the carbon nanotube / urea-formaldehyde resin carbon coated spherical microcrystalline graphite material is adopted as a negative electrode, prepared lithium iron phosphate / expanded microcrystalline graphite / carbon composite material is made into an electrode tab to serve as a positive electrode, a polypropylene diaphragm is clamped between positive and negative electrode tabs, the lithium ioncapacitor is assembled, and lithium nitrate aqueous solution with the concentration of 1 mol / L is injected into the position between the positive and negative electrode tabs to use as electrolyte. According to the method, graphene is replaced by cheap and easy-to-obtain microcrystalline graphite as the raw material of the carbon nanotube / urea-formaldehyde resin carbon coated spherical microcrystalline graphite material, obtained composite material has excellent electrochemistry performance, under the condition that charge-discharge specific capacity does not drop, better circulation stabilityis achieved, economic benefits are high, and the method is suitable for industrialized application.

Description

technical field [0001] The invention relates to the field of lithium-ion batteries, more specifically, to a method for preparing a lithium-ion capacitor using carbon nanotubes / urea-formaldehyde resin carbon-coated spherical microcrystalline graphite materials. Background technique [0002] Lithium-ion battery is a pollution-free green battery successfully developed at the end of the 20th century. Compared with traditional batteries, it has the advantages of high average discharge voltage, relatively large volume capacity and mass capacity, long discharge time, and light weight. Lithium-ion secondary batteries are rapidly marketed under the impetus of carbon materials as negative electrodes. However, while lithium-ion batteries are rapidly being marketed, there are also some problems. Some important indicators such as the discharge capacity, capacity retention rate and cycle life of the battery will drop sharply due to the phenomenon of lithium precipitation. At present, mos...

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Problems solved by technology

In addition, in the cycle process, it is inevitable that electrolyte solvents will be co-embedded between graphite layers. Due to the reduction of organic solvents, gas expansion will occur under high current, resulting in the exfoliation of graphite sheets, resulting in irreversible loss of active materials and solid electrolyte interface film (SEI Membrane) is continuously destroyed and regenerated, resulting in poor cycle life

However, graphite also has problems such as low specific capacity, low initial charge and discharge efficiency, and slow diffusion rate of lithium ions in graphite. Carbon nanotubes, etc.) mechanical compounding, surface oxidation treatment and other means to modify graphite, so that the electrochemical performance of graphite has been effectively improved, but its first reversible specific capacity and cycle stability at high rates still need to be improved.

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