Low-temperature type lithium ion secondary battery

Abstract

The invention discloses a low-temperature type lithium ion secondary battery. The low-temperature type lithium ion secondary battery comprises a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode is prepared from the following components including a positive electrode electroactive substance, a positive electrode conductive agent and a positive electrode adhesive; the positive electrode electroactive substance is spinel type lithium manganate, the positive electrode conductive agent is arbitrary more than two of superconductive carbon black, Super-P, KS-6, VGCF or a carbon nano tube, the positive electrode adhesive is polyvinylidene fluoride; the negative electrode is prepared from the following components including a negative electrode electroactive substance, a negative electrode conductive agent and a negative electrode adhesive; the negative electrode electroactive substance is spinel type lithium titanate, the negative electrode conductive agent is arbitrary one or more of the superconductive carbon black, the Super-P, the VGCF or the carbon nano tube, the negative electrode adhesive is the polyvinylidene fluoride; a solvent of the electrolyte is three or more of DMC, EMC, DEC, PC and EA but at least contains the PC and the EA, a solute of the solvent is lithium hexafluorophosphate, the melting point of the electrolyte is smaller than 40 DEG C below zero, and the viscosity is smaller than 3cP. The low temperature type lithium ion secondary battery can be safely charged under the low-temperature condition and is excellent in the charging and discharging cycle performance at low temperature.

Description

technical field [0001] The invention belongs to the technical field of low-temperature lithium-ion secondary batteries, and relates to a lithium-ion secondary battery, more specifically, to a lithium-ion secondary battery capable of being charged at low temperature and cyclically charged and discharged at low temperature. Background technique [0002] Since lithium-ion secondary batteries were commercialized in the early 1990s, with the continuous emergence of new materials and the gradual application of new technologies, lithium-ion secondary battery technology has made many progresses and its application fields have been further expanded. The main performance is that the energy density and power density are improved, the cycle life is increased, the safety performance is improved, and the low temperature -40°C or even low temperature -50°C has discharge capability. On the other hand, with the expansion of the field of human science and technology research and the change of...

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Problems solved by technology

[0004] But, because the negative electrode of the disclosed lithium ion secondary battery of above-mentioned patent all adopts graphite as electroactive material, because the lithium intercalation potential of graphite is about 0.1 volt, very close to the deposition potential 0 volt of lithium ion (relative to Li / Li + )

At low temperature, the viscosity of the organic electrolyte increases, the migration of lithium ions is difficult, and the polarization increases. If a lithium-ion battery with a lithium-ion graphite negative electrode system is charged at a low temperature, it is easy to cause lithium ions to deposit on the graphite negative electrode, forming Lithium dendrites, which penetrate the separator and short-circuit the battery, cause combustion or explosion, and eventually lead to failure of the lithium-ion battery

The low-temperature cycle charging and discharging working mode of the lithium-ion secondary battery with graphite as the electroactive material of the negative electrode is also impossible due to the problem that lithium ions are deposited into metallic lithium on the negative electrode during low-temperature charging.

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