Conductive adhesive, cylindrical lithium ion secondary battery and preparation method of cylindrical lithium ion secondary battery

Abstract

The invention belongs to the field of energy storage batteries, and particularly relates to a conductive adhesive, a cylindrical lithium ion secondary battery and a preparation method of the cylindrical lithium ion secondary battery. The conductive adhesive is prepared from raw materials including silicone rubber, polyvinylidene fluoride, an inorganic conductive agent and an initiator, and the mass ratio of the silicone rubber to the polyvinylidene fluoride to the inorganic conductive agent to the initiator is (20-40): (20-40): (25-50): (0.01-1). The invention discloses a cylindrical lithium ion secondary battery which comprises a shell with an opening at the upper end, a pole group is arranged in the shell, a cover cap arranged at an opening in the upper end of the shell in a sealed mode,and a current collecting disc is arranged between the positive electrode end of the pole group and the cover cap, the negative electrode end of the pole group is bonded with the lower end of the shell through the conductive adhesive, and the positive electrode end of the pole group is bonded with the current collecting disc through the conductive adhesive. The battery provided by the invention has excellent power performance and heat dissipation performance, and meanwhile, the battery is reliable in structure and low in short-circuit rate.

Description

technical field [0001] The invention belongs to the field of energy storage batteries, and in particular relates to a conductive glue, a cylindrical lithium-ion secondary battery and a preparation method thereof. Background technique [0002] In the 21st century, it has become a trend for electric vehicles to replace fuel vehicles, and lithium-ion secondary batteries are an important part of electric vehicles. Electric vehicles can be divided into pure electric vehicles, plug-in hybrid electric vehicles, 48V micro-hybrid electric vehicles, etc. Among them, plug-in hybrid electric vehicles, especially 48V micro-hybrid electric vehicles, have very high requirements on the pulse charge and discharge rate of the battery. The pulse charge rate requires 20-35C, the pulse discharge rate requires 30-50C, and the single battery capacity requires 8Ah -20Ah. [0003] According to the packaging process, lithium-ion secondary batteries can be divided into cylindrical batteries, square ...

AI Technical Summary

Problems solved by technology

This method has the following defects: First, in the process of kneading the aluminum foil of the positive electrode current collector and the copper foil of the negative electrode current collector, a certain amount of metal dust is easy to be generated, which may lead to micro-short circuit self-discharge of the battery, and severe dust punctures the diaphragm, and the positive and negative electrodes Short circuit, the battery catches fire and explodes; Second, when the current collecting plate and the end face of the electrode group are welded, due to the characteristics of laser welding, the welding between the current collecting plate and the end face of the electrode group can only be local spot welding, resulting in uneven distribution of current on the current collecting plate average, which affects the power performance and heat dissipation performance of the battery; third, because the area of ​​the end-face current collector empty foil is large, the coating area of ​​the active material is reduced, and the energy density of the battery is reduced; The spot welding process is connected to the bottom of the steel shell, and the contact resistance is relatively large. For a charge and discharge current above 50A, a large amount of heat is generated instantaneously. The local temperature is much higher than the safe temperature of the battery at 80°C, and the SEI film of the negative electrode of the battery will decompose and electrolyze. Side reactions such as liquid decomposition and positive electrode active material decomposition occur, and the battery temperature will further rise, which may easily cause safety problems such as thermal runaway

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