Lithium ion secondary battery

Abstract

The invention discloses a lithium ion secondary battery. The lithium ion secondary battery comprises a positive pole piece, a negative pole piece, an isolating membrane and an electrolyte, wherein thepositive pole piece comprises a positive current collector and a positive active material layer which is arranged on the surface of the positive current collector and contains a positive active material, and the negative pole piece comprises a negative current collector and a negative active material layer which is arranged on the surface of the negative current collector and contains a negativeactive material; wherein the positive electrode active substance comprises lithium iron phosphate, and the negative electrode active substance comprises graphite; wherein the positive current collector and / or the negative current collector are / is a composite current collector, and the composite current collector comprises an organic support layer and a conductive layer arranged on at least one surface of the organic support layer. The lithium ion secondary battery provided by the invention has good low-temperature performance.

Description

technical field [0001] The invention belongs to the technical field of electrochemical devices, in particular to a lithium ion secondary battery. Background technique [0002] Lithium-ion secondary batteries have high charge and discharge performance, no memory effect, and are environmentally friendly, and are widely used in electric vehicles and consumer electronics products. Lithium iron phosphate is one of the most commonly used positive electrode active materials for power batteries due to its high cycle life, good safety, and high temperature resistance. However, lithium-ion secondary batteries using lithium iron phosphate usually face the problem of poor low-temperature performance, which cannot meet the application requirements of batteries in low-temperature environments. Contents of the invention [0003] An embodiment of the present invention provides a lithium ion secondary battery, aiming at improving the low-temperature performance of the lithium ion secondar...

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Problems solved by technology

[0005] In the lithium ion secondary battery provided by the embodiment of the present invention, the positive electrode active material includes lithium iron phosphate, the negative electrode active material includes graphite, and the positive electrode current collector and / or the negative electrode current collector is a composite current collector, and the composite current collector includes an organic support layer and The conductive layer arranged on at least one surface of the organic support layer, since the organic support layer of the composite current collector adopts organic materials, compared with the traditional metal current collector, the thermal conductivity of the composite current collector of the present invention is smaller, and the heat insulation The heat preservation performance is good, so when the battery works in a low temperature environment, it is less affected by the ambient temperature, and the heat generated by the battery itself will not dissipate quickly, which is conducive to the lithium-ion secondary battery in a low temperature environment can also maintain power. Suitable working temperature inside the core, thus improving the disadvantage of poor kinetic performance of lithium iron phosphate battery at low temperature, so that lithium iron phosphate battery has good low-temperature electrochemical performance and safety performance

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