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CN-121983640-A - Needled-preventing lithium ion battery and preparation method thereof

CN121983640ACN 121983640 ACN121983640 ACN 121983640ACN-121983640-A

Abstract

The lithium ion battery has the technical field of lithium ion batteries, and is characterized in that an anode is compounded by adopting LMFP and NCM according to a ratio of 6:4, a cathode is compounded by adopting primary and secondary artificial graphite according to a ratio of 7:3, an electrolyte is matched with a compound lithium salt and a compound additive by using a specific proportion solvent, and the key technological parameters of a pole piece and an N/P ratio are optimized.

Inventors

  • CAO ZHIMING
  • LI JUNHAO
  • QIU BAOCHENG
  • TANG ZHENGGUO
  • XU LIANG
  • LIANG FENG
  • WANG ZISHI
  • HOU JUNJUN
  • ZHOU SHUPING
  • MA LINZHI
  • ZHANG XIAOWEI

Assignees

  • 河南福森储能科技有限公司
  • 河南福森新能源科技有限公司

Dates

Publication Date
20260505
Application Date
20260226

Claims (10)

  1. 1. The anti-needling lithium ion battery comprises a positive plate, a negative plate, a diaphragm and electrolyte, and is characterized in that positive active substances of the positive plate are a composite system of lithium iron manganese phosphate and lithium nickel cobalt manganese oxide, negative active substances of the negative plate are a composite system of primary particle artificial graphite and secondary particle artificial graphite, the diaphragm is a ceramic coating diaphragm of a polyethylene microporous membrane base film, the electrolyte comprises a mixed solvent of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate, a composite lithium salt and a composite additive, the composite additive at least comprises a flame retardant, a film forming additive and a lithium salt additive, wherein the mass ratio of the lithium iron manganese phosphate to the lithium nickel cobalt manganese oxide is 6:4, the mass ratio of the primary particle artificial graphite to the secondary particle artificial graphite is 7:3, and the volume ratio of the mixed solvent is ethylene carbonate to methyl ethyl carbonate to dimethyl carbonate=2:3:5.
  2. 2. The lithium ion battery according to claim 1, wherein the positive plate comprises 96.3% of positive electrode active material, 1.5% of conductive agent SP, 2% of binder polyvinylidene fluoride and 0.2% of dispersing agent according to mass percentage, the positive plate has an areal density of 370+/-5 g/m 2 , a compacted density of 2.75+/-0.05 g/cm 3 , the molar ratio of Mn to Fe in lithium manganese iron phosphate is 6:4, the molar ratio of Ni to Co to Mn in lithium nickel cobalt manganese oxide is 5:2:3, and the molar ratio of Ni is less than or equal to 60%.
  3. 3. The lithium ion battery according to claim 1, wherein the negative plate comprises 96 mass percent of negative active material, 0.5 mass percent of conductive agent SP, 1.5 mass percent of thickener sodium carboxymethylcellulose, 2 mass percent of binder styrene-butadiene rubber, the surface density of the negative plate is 176+/-3 g/m 2 , the compaction density is 1.6+/-0.05 g/cm 3 , the raw materials of the primary particle artificial graphite and the secondary particle artificial graphite are one or a mixture of petroleum coke and needle coke, the particle size D50 of the primary particle artificial graphite is 10-15 mu m, and the particle size D50 of the secondary particle artificial graphite is 20-25 mu m.
  4. 4. The lithium ion battery of claim 1, wherein the separator has a polyethylene microporous membrane base film thickness of 12 μm, a porosity of 39±2%, and a ceramic coated material of Al 2 O 3 or γ -AlOOH, and a coating thickness of 2-3 μm.
  5. 5. The lithium ion battery of claim 1, wherein the composite lithium salt of the electrolyte is a combination of lithium hexafluorophosphate and lithium difluorosulfimide, wherein the concentration of the lithium hexafluorophosphate is 1mol/L, and the addition amount of the lithium difluorosulfimide is 1.5 wt%.
  6. 6. The lithium ion battery of claim 5, wherein the film forming additive in the composite additive comprises fluoroethylene carbonate, ethylene sulfate, vinylene carbonate and 1, 3-propane sultone.
  7. 7. The lithium ion battery of claim 6, wherein the flame retardant in the composite additive is ethoxy pentafluoroethylene triphosphazene, and the addition amount of the flame retardant is 5-10 wt%.
  8. 8. A method for preparing the needling-preventing lithium ion battery as defined in any one of claims 1 to 7, comprising the steps of: (1) Preparing a positive plate, namely mixing a positive active material, a conductive agent, a binder and a dispersing agent according to a formula, adding a solvent, stirring and pulping, coating the mixture on an aluminum foil current collector, and baking, rolling, slitting and welding the electrode lugs to obtain the positive plate; (2) The preparation of the negative plate comprises the steps of mixing a negative active material, a conductive agent, a thickening agent and a binder according to a formula, adding a solvent, stirring and pulping, coating the mixture on a copper foil current collector, and baking, rolling, slitting and welding the electrode lugs to obtain the negative plate; (3) Winding the battery cell, namely stacking and winding the positive plate, the diaphragm and the negative plate at one time to form a cylindrical battery cell; (4) The battery core after winding is put into a steel shell, and the pole lug and the pole post of the steel shell are fixed through spot welding; (5) Baking, namely vacuum baking the battery cells filled in the steel shell, wherein the moisture content of the battery cells is controlled to be less than or equal to 150 ppm; (6) Injecting electrolyte into the battery cell under a dry environment, and standing to fill the electrolyte; (7) And (3) sealing and forming, namely sealing the battery cell, and then forming according to a preset process to obtain the needling-preventing lithium ion battery.
  9. 9. The preparation method of the water treatment agent of claim 8, wherein the solvent in the step (1) is N-methylpyrrolidone, the solid-liquid mass ratio is 1 (0.8-1.2), the stirring speed is 800-1200 rpm, the stirring time is 2-3 h, the solvent in the step (2) is deionized water, the solid-liquid mass ratio is 1 (1.0-1.5), the stirring speed is 600-1000 rpm, and the stirring time is 3-4 h.
  10. 10. The preparation method of the glass fiber reinforced plastic composite material, according to claim 8, wherein the baking temperature in the step (1) is 120-140 ℃, the baking time is 4-6 h ℃, the baking temperature in the step (2) is 80-100 ℃, the baking time is 6-8 h, the vacuum baking temperature in the step (5) is 120+/-5 ℃, the vacuum degree is less than or equal to minus 0.095 MPa, and the baking time is 8-12 h.

Description

Needled-preventing lithium ion battery and preparation method thereof Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery with excellent anti-needling safety performance and a preparation process thereof. Background The lithium ion battery has become a core energy storage device in the field of new energy sources by virtue of the advantages of high energy density, long cycle life and the like, and as one of important test methods for evaluating the safety of the lithium ion battery, the lithium battery needling test can effectively evaluate the performance of the battery under extreme conditions, namely when the battery is punctured by external force, the internal positive and negative electrodes are directly contacted to cause short circuit, and severe heat release is accompanied, so that electrolyte burning, battery firing and even explosion can be caused, and serious threat is brought to the safety of users. In the prior art, the needling safety performance of the lithium battery is mainly improved by adopting lithium iron phosphate (LFP) as an anode active material, wherein the olivine has a stable structure and high oxygen release temperature, the needling passing rate can reach more than 80 percent, but the energy density is only 140-160 Wh/kg, the requirements of a new energy automobile on the endurance mileage are difficult to meet, and the energy density can be improved to more than 200 Wh/kg by adopting nickel cobalt lithium manganate (NCM) as an anode material, but the material has strong chemical activity and low oxygen release temperature, is easy to generate thermal runaway during needling, and has the passing rate less than 20 percent. Some manufacturers try to dope a small amount of lithium iron phosphate in an NCM system, but the voltage platform difference of the two is obvious, and the lithium iron phosphate is 3.2V/NCM 3.6V, so that the SOC (state of charge) control is difficult in the charge and discharge process, the capacity attenuation is fast in the circulation process, and the practical application effect is poor. In the aspect of electrolyte, in the prior art, a carbonate mixed solvent such as EC/DMC/EMC is mostly adopted, and then a single film forming additive such as VC is matched, so that the flash point of the solvent is low, the solvent is easy to ignite during needle punching short circuit, the solid electrolyte interface film SEI film formed by the film forming additive is insufficient in high temperature resistance, and is easy to crack at high temperature, continuous side reaction of the electrolyte and an electrode is caused, and the thermal runaway risk is increased. Therefore, developing a lithium ion battery which not only maintains high energy density, but also can effectively improve needling safety becomes a technical problem to be solved urgently in the industry. Disclosure of Invention In order to solve the defects in the prior art, the invention provides an anti-needling lithium ion battery and a preparation method thereof, and the cooperative improvement of energy density and needling safety is realized. The technical problems to be solved by the invention are realized by the following technical scheme: The invention discloses an anti-needling lithium ion battery, which comprises a positive plate, a negative plate, a diaphragm and an electrolyte, wherein positive active substances of the positive plate are a composite system of lithium iron manganese phosphate (LMFP) and lithium nickel cobalt manganese oxide (NCM), negative active substances of the negative plate are a composite system of primary particle artificial graphite and secondary particle artificial graphite, the diaphragm is a ceramic coating diaphragm of a polyethylene microporous membrane base membrane, the electrolyte comprises a mixed solvent of Ethylene Carbonate (EC), methyl ethyl carbonate (EMC) and dimethyl carbonate (DMC), a composite lithium salt and a composite additive, the composite additive at least comprises a flame retardant, a film forming additive and a lithium salt additive, wherein the mass ratio of lithium iron manganese phosphate to lithium nickel cobalt manganese oxide is 6:4, the mass ratio of primary particle artificial graphite to secondary particle artificial graphite is 7:3, and the volume ratio of the mixed solvent is ethylene carbonate to methyl ethyl carbonate to dimethyl carbonate=2:3:5. The positive plate comprises 96.3 mass percent of positive electrode active substance, 1.5 mass percent of conductive agent SP, 2 mass percent of binder polyvinylidene fluoride (PVDF) and 0.2 mass percent of dispersing agent, wherein the surface density of the positive plate is 370+/-5 g/m 2, and the compaction density is 2.75+/-0.05 g/cm 3. Further, the molar ratio of Mn to Fe in the lithium manganese iron phosphate is 6:4, the molar ratio of Ni to Co to Mn in the lithium nickel cobalt manganese oxide is 5:2:3,