Secondary battery and terminal

Abstract

The invention provides a secondary battery. The secondary battery comprises at least one battery unit assembly, each battery unit assembly comprises a positive pole piece, a negative pole piece and a diaphragm arranged between the positive pole piece and the negative pole piece, and each of the positive pole piece and the negative pole piece comprises a current collector and an active material layer arranged on the current collector; and the elongation rate of the diaphragm is greater than 100%, the elongation rate of the diaphragm comprises the elongation rate along the length direction and / or the elongation rate along the width direction, the ratio of the elongation rate of the diaphragm to the thickness of the active material layer of the positive pole piece and / or the negative pole piece is 3.0-8. 0 % / [mu]m, and the ratio of the elongation of the diaphragm to the elongation of the current collector of the positive pole piece and / or the negative pole piece is greater than or equal to 60. The secondary battery provided by the embodiment of the invention has high safety performance on the basis of considering high energy density. The embodiment of the invention also provides a terminal comprising the secondary battery.

Description

technical field [0001] The present application relates to the technical field of secondary batteries, in particular to a secondary battery and a terminal. Background technique [0002] With the development of the Internet and the popularization of portable mobile electronic devices, people have higher and higher requirements for the battery life and fast charging capacity of lithium secondary batteries, but there are also more and more battery thermal runaway accidents. A large number of studies and analyzes have found that the internal short circuit caused by the mechanical abuse of the secondary battery (such as nailing, bending, foreign matter extrusion, etc.) is one of the main reasons for its thermal runaway. When the secondary battery is damaged by mechanical external force, such as needle-shaped conductors or other foreign matter pierced, the current collector and active material layer are destroyed, debris is generated, and direct contact short circuit occurs. At the...

AI Technical Summary

Problems solved by technology

Among them, since the short-circuit resistance of the positive electrode current collector (aluminum foil) and the negative electrode active material layer are relatively close to the internal resistance of the battery, the short-circuit point generates the largest heat power at this time, and the temperature rises rapidly. The temperature rise causes SEI to decompose and the diaphragm shrinks and melts, resulting in battery Highest risk of thermal runaway

At the same time, since secondary batteries are usually composed of battery cell components (positive electrode current collector-positive electrode active material layer-separator-negative electrode active material layer-negative electrode current collector) by stacking or winding, in the process of foreign matter penetrating until the battery is pierced In the process, all kinds of debris generated by destruction are often in random contact, and internal short circuits are more likely to occur. At the same time, the heat release of internal short circuits can easily trigger thermal runaway chain reactions.

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