CN-122025796-A - Lithium-rich manganese-based lithium ion battery electrolyte and preparation method thereof

Abstract

The invention discloses a lithium-rich manganese-based lithium ion battery electrolyte and a preparation method thereof, wherein the lithium-rich manganese-based lithium ion battery electrolyte comprises, by mass, 1-3% of an additive, 11-15% of lithium salt, 0.5-5% of a film forming agent, 1-2% of a gassing inhibitor and the balance of an organic solvent. The invention introduces an additive with a fluorine-containing cyclic phosphate structure, effectively stabilizes the interface between the lithium-rich manganese-based electrode and electrolyte, inhibits the damage of a layered structure under high-temperature and high-pressure circulation, adds a film forming agent and a gas production inhibitor, cooperates with the fluorine-containing cyclic phosphate to slow down the structural phase change of the lithium-rich manganese-based positive electrode, inhibits the gas production of the electrolyte in the high-temperature circulation process, reduces the volume expansion of a battery in the circulation process, and adopts the combination of lithium hexafluorophosphate and lithium difluorosulfimide to improve the thermal stability and the high-pressure stability of the electrolyte and effectively stabilizes the lithium-rich manganese-based electrode.

Inventors

• SHAO JUNHUA
• ZHANG XIAOXU
• ZHANG LIJUAN
• LI HAIJIE
• SHI JUNFENG
• SHI YINGFEI
• Tong Denghui
• QIN JIAN
• WANG YAZHOU
• PANG XINRU
• SHENG ZHIYUAN
• YAN ZHEN
• XIAO WENGUI

Assignees

• 湖南法恩莱特新能源科技有限公司

Dates

Publication Date

20260512

Application Date

20260206

Claims (10)

1. 1. The lithium-rich manganese-based lithium ion battery electrolyte is characterized by comprising, by mass, 1-3% of an additive, 11-15% of lithium salt, 0.5-5% of a film forming agent, 1-2% of a gassing inhibitor and the balance of an organic solvent.
2. 2. The lithium-rich manganese-based lithium ion battery electrolyte according to claim 1, wherein the additive is a fluorine-containing cyclic phosphate compound.
3. 3. The lithium-rich manganese-based lithium ion battery electrolyte according to claim 2, wherein the fluorine-containing cyclic phosphate compound is 2-trifluoroethoxy-2-oxo-1, 3, 2-dioxaphospholane.
4. 4. The lithium-rich manganese-based lithium ion battery electrolyte according to claim 2 or 3, wherein the mass percentage of the fluorine-containing cyclic phosphate compound in the electrolyte is 1-2%.
5. 5. The lithium-rich manganese-based lithium ion battery electrolyte of claim 1, wherein the lithium salt comprises at least one of lithium hexafluorophosphate or lithium bis-fluorosulfonyl imide.
6. 6. The lithium-rich manganese-based lithium ion battery electrolyte according to claim 1 or 5, wherein the lithium salt is a complex of lithium hexafluorophosphate and lithium difluorosulfimide.
7. 7. The lithium-rich manganese-based lithium ion battery electrolyte according to claim 1, wherein the film forming agent is fluoroethylene carbonate.
8. 8. The lithium-rich manganese-based lithium ion battery electrolyte according to claim 1, wherein the gassing inhibitor is 1, 3-propane sultone.
9. 9. The lithium-rich manganese-based lithium ion battery electrolyte according to claim 1, wherein the organic solvent comprises at least one of ethylene carbonate, dimethyl carbonate, and ethylmethyl carbonate.
10. 10. A method for preparing the lithium-rich manganese-based lithium ion battery electrolyte according to claim 1, which is characterized by comprising the steps of weighing lithium salt with corresponding mass fraction, dissolving in an organic solvent, stirring to form a uniform solution, adding an additive and a film forming agent into the solution respectively, and stirring to dissolve the additive and the film forming agent to obtain the electrolyte.

Description

Lithium-rich manganese-based lithium ion battery electrolyte and preparation method thereof Technical Field The invention relates to a battery electrolyte and a preparation method thereof, in particular to a lithium-rich manganese-based lithium ion battery electrolyte and a preparation method thereof. Background The lithium-rich manganese-based positive electrode material has a unique two-layer lattice mixed structure, so that the lithium-rich manganese-based positive electrode material has the advantages of high specific capacity (more than 250 mAh.g -1) and high working voltage, the theoretical energy density is obviously superior to that of the traditional lithium ion battery, and the urgent requirements of the fields of electric automobiles, large-scale energy storage and the like on the high-energy-density battery are hopefully met. As the "blood" of lithium-rich manganese-based lithium ion batteries, conventional combinations of conventional lithium salts and organic solvents are currently used as electrolytes, however, the system still faces multiple challenges in practical applications. Firstly, as the layered structure rich in lithium and manganese is easy to break in the circulation process, lattice oxygen release causes irreversible phase change of the layered structure to spinel/rock salt phase, cell parameter distortion causes interlayer distance shrinkage, transition metal ion migration and damage of a lithium deintercalation channel, active material loss aggravates electrode/electrolyte interface side reaction, and finally voltage attenuation, capacity rapid decay and circulation stability deterioration are shown, and capacity retention rate is obviously reduced after multiple charge and discharge. In addition, the safety of the battery has hidden trouble, and particularly under the high-temperature condition, electrolyte is easy to decompose and gas is produced, so that the internal pressure of the battery is increased, and even thermal runaway is induced. CN113078357a discloses a nonaqueous electrolyte for a high-voltage lithium ion battery and a lithium ion battery, and an interface reaction of the electrolyte for the lithium manganate battery is inhibited by adding a cyclic phosphate compound, but although an electrolyte capable of improving high-voltage stability is provided for the lithium manganate battery, the instability of a lithium-rich manganese-based layered structure is not explored, and the lithium manganate itself with a spinel structure is more stable, so that the obtained conclusion has limited significance for developing and optimizing the lithium-rich manganese-based electrolyte. Disclosure of Invention The invention aims to provide the lithium-rich manganese-based lithium ion battery electrolyte which can effectively stabilize the lithium-rich manganese-based electrode and inhibit side reactions of an electrode/electrolyte interface, and the other aim of the invention is to provide a preparation method of the electrolyte. The lithium-rich manganese-based lithium ion battery electrolyte comprises, by mass, 1-3% of an additive, 11-15% of lithium salt, 0.5-5% of a film forming agent, 1-2% of a gassing inhibitor and the balance of an organic solvent. The additive is a fluorine-containing cyclic phosphate compound, has a higher HOMO energy level, can form a passivation film at the positive electrode interface in preference to a solvent, and can inhibit oxidative decomposition of electrolyte at the positive electrode interface under high pressure. Preferably, the fluorine-containing cyclic phosphate compound is 2-trifluoroethoxy-2-oxo-1, 3, 2-dioxaphospholane (TFEOP), and the structure is as follows: , The P=O group in the molecule can carry out nucleophilic substitution reaction with oxygen atoms on the surface of the lithium-rich manganese-based material to form chemical bonding, then a ring-shaped structure (phospholane) in the molecule can carry out ring-opening polymerization reaction at an electrode/electrolyte interface to generate a compact polymer passivation film, and the passivation film has inorganic-organic composite characteristics because the passivation film contains P-O bonds and fluorinated groups, can inhibit transition metal dissolution and electrolyte oxidative decomposition, blocks direct contact of the electrolyte and an active material, prevents lattice oxygen release of the lithium-rich manganese-based material under high voltage, and slows down structural phase change and capacity attenuation. Preferably, the mass percentage of the fluorine-containing cyclic phosphate compound in the electrolyte is 1-2%, and when the fluorine-containing cyclic phosphate compound is excessive, an excessively thick fluorine-containing passivation film is generated at the interface of the electrolyte and the electrode to prevent migration of lithium ions, so that the impedance is increased. The lithium salt comprises at least one of lithium hexafluorophosphate (LiPF 6) or