SEPARATOR, SECONDARY BATTERY, ELECTROCHEMICAL DEVICE, AND ELECTRIC DEVICE

A separator is provided, including a base film and an organic coating disposed on one surface of the base film. The organic coating contains a first polymer and a second polymer. A melting point T of the first polymer satisfies 60°C ≤ T ≤ 100°C, and a swelling degree D of the second polymer during placement in a solution at 60°C for 24 h satisfies D ≤ 30%. The first polymer maintains the adhesion force requirements during the battery charge-discharge cycling. When the battery generates heat during charging and discharging, the first polymer softens relatively easily, reducing adhesion force, which allows the interface between the separator and the battery electrode plate to open, helping to reduce heat accumulation and improve the safety performance of a hot box of a cell. The second polymer, with a relatively low swelling degree, can maintain the original morphology in the cell, effectively alleviating the issue of the low-melting-point first polymer melting into a film during the hot-pressing process of the cell, thereby improving the cycling performance of the cell. This application further provides a secondary battery, an electrochemical device, and an electric device.