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CN-121394496-B - Lithium secondary battery and application

CN121394496BCN 121394496 BCN121394496 BCN 121394496BCN-121394496-B

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium secondary battery and application thereof, wherein the lithium secondary battery comprises a battery pack, the battery pack comprises positive electrodes and negative electrodes which are alternately arranged, the outermost layers of the battery pack are both positive electrodes, and a diaphragm containing electrolyte is arranged between the positive electrodes and the negative electrodes, the positive electrodes comprise lithium iron manganese phosphate positive electrode materials, the electrolyte comprises electrolyte, an organic solvent and an additive, the additive contains tris (trimethylsilane) phosphate, and the mass content of the tris (trimethylsilane) phosphate is 0.5-3wt%. The invention greatly improves the cycle stability of the battery and obviously prolongs the cycle life of the lithium secondary battery of the lithium manganese iron phosphate anode material.

Inventors

  • LIN KAIRUI
  • XU ZHI

Assignees

  • 福建新峰二维材料科技有限公司

Dates

Publication Date
20260505
Application Date
20251222

Claims (10)

  1. 1. A lithium secondary battery is characterized by comprising a battery pack and a battery shell, wherein the battery pack is arranged in the battery shell, the battery pack comprises positive electrodes and negative electrodes which are alternately arranged, the outermost layers of the battery pack are positive electrodes, a diaphragm containing electrolyte is arranged between the positive electrodes and the negative electrodes, the positive electrodes comprise lithium manganese iron phosphate positive electrode materials, the electrolyte comprises electrolyte, an organic solvent and an additive, the additive contains tris (trimethylsilane) phosphate, the mass content of the tris (trimethylsilane) phosphate is 0.5-3wt%, the organic solvent comprises cyclic carbonate and/or chain carbonate, the cyclic carbonate comprises at least one of ethylene carbonate, propylene carbonate and butylene carbonate, the chain carbonate comprises at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate and ethylene propyl carbonate, the tris (trimethylsilane) phosphate is subjected to oxidative decomposition to form a thin and compact protective film, and the protective film and the organic solvent has a high direct contact potential with the battery shell.
  2. 2. The lithium secondary battery according to claim 1, wherein the additive further comprises vinylene carbonate.
  3. 3. The lithium secondary battery according to claim 2, wherein the mass ratio of vinylene carbonate to tris (trimethylsilane) phosphate is (0.5-2): 1.
  4. 4. The lithium secondary battery according to claim 2, wherein the mass content of vinylene carbonate in the electrolyte is 0.25-6wt%.
  5. 5. The lithium secondary battery according to claim 1, wherein the electrolyte comprises lithium hexafluorophosphate, and a mass ratio of lithium hexafluorophosphate to tris (trimethylsilane) phosphate is (5-35): 1.
  6. 6. The lithium secondary battery according to claim 5, wherein the mass of the lithium hexafluorophosphate is 10 to 17wt% of the total mass of the electrolyte.
  7. 7. The lithium secondary battery according to claim 1, wherein when the organic solvent comprises a cyclic carbonate and a chain carbonate, the mass ratio of the cyclic carbonate to the chain carbonate is (0.5-5): 1.
  8. 8. The lithium secondary battery according to claim 1, wherein the lithium secondary battery further comprises at least one of the following structures: the first structure, the positive electrode and the negative electrode are sheet electrodes, and/or the battery pack is a laminated structure formed by the positive electrode, the negative electrode and the diaphragm; the second structure and the negative electrode comprise a negative electrode active material, and the negative electrode active material comprises at least one of carbon, silicon carbon and silicon negative electrode.
  9. 9. The lithium secondary battery according to claim 1, wherein the lithium iron manganese phosphate positive electrode material comprises a lithium iron manganese phosphate matrix and a carbon coating layer coated on the surface of the lithium iron manganese phosphate matrix, wherein the lithium iron manganese phosphate matrix has a chemical formula of Li a Fe x Mn y M j PO q , wherein M comprises at least one of Al, mg, cu, co, ni, nb, V, ti, la, a is more than or equal to 0.8 and less than or equal to 1.2, x is more than or equal to 0.1 and less than or equal to 0.9, y is more than or equal to 0 and less than or equal to 0.9, j is more than or equal to 0 and less than or equal to 0.1,4 and q is more than or equal to 0.5-3% of the total mass of the lithium iron manganese phosphate positive electrode material.
  10. 10. An electric device, characterized in that it comprises the lithium secondary battery according to any one of claims 1 to 9.

Description

Lithium secondary battery and application Technical Field The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium secondary battery and application thereof. Background In the field of lithium secondary batteries, lithium iron manganese phosphate (LMFP) is considered a promising cathode material due to its high voltage plateau, good thermal stability and cost effectiveness. However, lithium secondary batteries of lithium iron manganese phosphate cathode materials often face problems of insufficient cycle life and cycle stability during cycling, which limits their wide use in long-life applications. Although the existing technology can realize the basic functions of a lithium secondary battery of a lithium iron manganese phosphate cathode material, there are some problems and disadvantages. Firstly, the lack of effective additives in the traditional electrolyte can not effectively inhibit side reactions of the battery in the circulating process, so that the battery performance is rapidly attenuated. Secondly, the potential of the positive electrode material cannot be fully utilized by the existing battery structure, and the cycle stability of the battery is limited. In addition, the existing technical schemes have poor performance under high temperature and high voltage conditions, and are difficult to meet the increasing requirements of high-performance batteries. Therefore, a battery structure is developed to improve the cycle life and the cycle stability of the lithium secondary battery of the lithium manganese iron phosphate anode material, and the lithium secondary battery has important practical significance and application value. It should be noted that this section of the disclosure only provides a background related to the present disclosure, and does not necessarily constitute prior art or known technology. Disclosure of Invention The invention aims to overcome the defects of low cycle life and poor cycle stability of a lithium secondary battery of a lithium iron manganese phosphate anode material in the prior art, and provides a lithium secondary battery and application thereof. In order to achieve the above object, according to a first aspect, the present invention provides a lithium secondary battery comprising a battery pack including positive and negative electrodes alternately arranged, and an outermost layer of the battery pack being both positive electrodes, and a separator containing an electrolyte disposed between the positive and negative electrodes, wherein the positive electrode comprises a lithium manganese iron phosphate positive electrode material, the electrolyte comprises an electrolyte, an organic solvent, and an additive, wherein the additive contains tris (trimethylsilane) phosphate, and the mass content of the tris (trimethylsilane) phosphate is 0.5 to 3wt%. In some preferred embodiments of the invention, the additive further comprises vinylene carbonate. In some preferred embodiments of the invention, the mass ratio of vinylene carbonate to tris (trimethylsilane) phosphate is (0.5-2): 1. In some preferred embodiments of the invention, the mass content of vinylene carbonate in the electrolyte is 0.25-6wt%. In some preferred embodiments of the invention, the electrolyte comprises lithium hexafluorophosphate, the mass ratio of lithium hexafluorophosphate to tris (trimethylsilane) phosphate being (5-35): 1. In some preferred embodiments of the invention, the mass of lithium hexafluorophosphate is 10wt% to 17wt% of the total mass of the electrolyte. In some preferred embodiments of the invention, the organic solvent comprises a cyclic carbonate and/or a chain carbonate, wherein, The cyclic carbonate comprises at least one of ethylene carbonate, propylene carbonate and butylene carbonate, and the chain carbonate comprises at least one of dimethyl carbonate, diethyl carbonate, methylethyl carbonate, dipropyl carbonate, methylpropyl carbonate and ethylpropyl carbonate; And/or, when the organic solvent comprises a cyclic carbonate and a chain carbonate, the mass ratio of the cyclic carbonate to the chain carbonate is (0.5-5): 1. In some preferred embodiments of the present invention, the lithium secondary battery further comprises at least one of the following structures: the first structure, the positive electrode and the negative electrode are sheet electrodes, and/or the battery pack is a laminated structure formed by the positive electrode, the negative electrode and the diaphragm; the second structure and the negative electrode comprise a negative electrode active material, wherein the negative electrode active material comprises at least one of carbon, silicon carbon and a silicon negative electrode; The third structure of the lithium secondary battery also comprises a battery shell, and the battery pack is arranged in the battery shell. The lithium manganese iron phosphate anode material comprises a lithium manganese iron phos