Composite conductive agent, lithium ion battery pole pieces and lithium ion battery

Abstract

The invention discloses a novel composite conductive agent, a lithium ion positive pole piece and a lithium ion negative pole piece made of the composite conductive agent, and a lithium ion battery containing the positive pole piece and the negative pole piece. By leading the novel composite conductive agent, the developed pole piece of which the surface has an effective conductive network can be prepared by adding a small amount of conductive agent, so that the prepared lithium ion has excellent rate discharging, low-temperature discharging, high-temperature storage and cyclic properties. The composite conductive agent comprises single-wall or fewer-wall carbon nanotubes and graphene nanosheets, wherein the specific surface area of each single-wall or fewer-wall carbon nanotube is 200 to 1500m<2> / g, the tube diameter is 1 to 10nm, and the tube length is greater than 5mu m; the diameter of each graphene nanosheet is 0.2 to 2mu m, the specific surface area is smaller than 1800m<2> / g, and the thickness is smaller than 2nm.

Description

technical field [0001] The invention belongs to the field of lithium ion batteries, and in particular relates to a composite conductive agent applied to lithium ion batteries and a preparation method thereof, lithium ion positive and negative pole sheets and a preparation method thereof, and a lithium ion battery comprising the above composite conductive agent and pole pieces . Background technique [0002] The positive and negative electrodes of lithium-ion batteries are mainly composed of active materials, conductive agents, thickeners, binders and current collectors. Among them, the positive electrode active material is transition metal oxide or transition metal phosphate, which are semiconductors or insulators with poor conductivity, and a conductive agent must be added to improve the conductivity; the conductivity of the negative electrode active material is slightly better, but after multiple charging During discharge, it will experience periodic expansion and contrac...

AI Technical Summary

Problems solved by technology

Lithium ion intercalation and extraction cause the volume of silicon particles to expand and shrink rapidly, and strong stress causes silicon particles to pulverize. A considerable part of the pulverized silicon powder cannot be in contact with the conductive agent. Lithium in this part of the silicon powder cannot be released during discharge, thus The irreversible capacity caused by the first discharge is very large, which reduces the cycle performance

Using ordinary conductive materials (conductive graphite, conductive carbon black, multi-walled carbon nanotubes, and vapor-grown carbon fibers), it is difficult to form a more developed and effective conductive network even if the amount of use is increased, and it is difficult to give full play to these two new positive and negative electrodes. Excellent performance of materials

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