CN-122000471-A - Stable double-interface electrolyte and preparation method thereof

CN122000471ACN 122000471 ACN122000471 ACN 122000471ACN-122000471-A

Abstract

The invention relates to the technical field of lithium metal batteries, in particular to a stable double-interface electrolyte and a preparation method thereof. The stable double-interface electrolyte is prepared by uniformly mixing lithium salt, an organic solvent and a fluorine-containing silicon-based additive, and standing, wherein the fluorine-containing silicon-based additive accounts for 1-5% of the electrolyte by mass, and the fluorine-containing silicon-based additive is a compound with a structure shown in the following formula (I): (I) Wherein X is trimethylsilyl, R is alkyl with 1-4 carbon atoms, and Li + migration number of the stable double-interface electrolyte at 25 ℃ is more than 0.65. The invention solves the contradiction that the conventional additive is difficult to improve the ion transmission and stable interface of the lithium metal battery, overcomes the problem of electrode polarization caused by low migration number of the traditional electrolyte Li + , constructs a firm SEI and CEI composite interface layer, and remarkably improves the cycle stability and safety of the battery.

Inventors

LONG JIANPING
TIAN JINYU
HU ANJUN
LIU QI
LI YUHAN
YANG WEI
DENG YIFAN
JIANG XIANGSONG

Assignees

成都理工大学

Dates

Publication Date: 20260508
Application Date: 20260310

Claims (10)

1. The stable double-interface electrolyte for the lithium metal battery is characterized by being prepared by uniformly mixing lithium salt, an organic solvent and a fluorine-containing silicon-based additive and then standing until a solvation reaction is finished; The fluorine-containing silicon-based additive accounts for 1-5% of the stable double-interface electrolyte by mass, and is a compound with a structure shown in the following formula (I): (I); Wherein X is trimethylsilyl, R is alkyl with 1-4 carbon atoms, and n is natural number 1-4; The stable dual interface electrolyte has a Li + mobility >0.65 at 25 ℃.
2. The stable dual interface electrolyte of claim 1, wherein the fluorine-containing silicon-based additive is ethyl 2, 2-difluoro-2- (trimethylsilyl) acetate (DTAE).
3. The stable dual-interface electrolyte of claim 2, wherein DTAE is added in an amount of 2wt% based on the mass of the stable dual-interface electrolyte.
4. The stable dual-interface electrolyte of claim 1, wherein the organic solvent is a carbonate electrolyte.
5. The stable dual-interface electrolyte of claim 4, wherein the carbonate electrolyte is prepared by mixing ethylene carbonate and diethyl carbonate according to a volume ratio of (0.5-2): 1.
6. The stable dual interface electrolyte of claim 1 wherein the lithium salt is LiPF 6 and the concentration of the lithium salt in the lithium metal battery electrolyte is 1M.
7. The stable dual interface electrolyte of claim 1 wherein the resting temperature is 25-30 ℃ and the time from resting to the end of the solvation reaction is 2-3 hours.
8. The stable dual interface electrolyte of claim 1 wherein the Li + mobility at 25 ℃ is 0.72.
9. A lithium metal battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is the stable double-interface electrolyte according to any one of claims 1 to 8.
10. The lithium metal battery of claim 9, wherein the positive electrode comprises a high nickel layered oxide positive electrode active material.

Description

Stable double-interface electrolyte and preparation method thereof Technical Field The invention relates to the technical field of lithium metal batteries, in particular to a stable double-interface electrolyte and a preparation method thereof, wherein the stable double-interface electrolyte can simultaneously stabilize a high-voltage positive electrode interface and a lithium metal negative electrode interface of a lithium metal battery system. Background Lithium metal anodes are considered as the ultimate anode material for the realization of next generation high energy density batteries due to their extremely high theoretical capacity and lowest electrochemical potential. When matched with a high-capacity high-operating-voltage high-nickel ternary positive electrode, the system is expected to break through the energy density bottleneck of the current lithium ion battery. However, commercial applications of lithium metal batteries suffer from severe electrode double-interface instability problems. On the negative electrode side, the high reactivity of metallic lithium with the electrolyte causes uneven, unstable solid electrolyte interface SEI films to continue to grow, and with electrolyte consumption and lithium dendrite growth, a safety risk is raised. On the positive electrode side, the high-nickel material is easy to generate structural degradation and CEI interface side reaction under high voltage, and the cycle performance attenuation of the lithium metal battery is further aggravated by oxidative decomposition of the conventional electrolyte and trace acid corrosion. Extensive analysis shows that the exacerbation of the above-mentioned interfacial side reactions is closely related to the severe electrode polarization inside the cell. One of the important sources of polarization is that the number of lithium ions migrating in conventional electrolytes is too low. In conventional electrolytes, the lithium ion mobility is typically below 0.4, which means that more than 60% of the current is contributed by anion mobility. In operation of the cell, anions rapidly accumulate near the electrodes to form a space charge layer, resulting in severe concentration polarization. The polarization not only limits the rate capability of the battery, but also forces the battery to operate at a higher overpotential, wherein the high overpotential directly accelerates the growth of lithium dendrites on the negative electrode side of lithium metal, and aggravates the oxidative decomposition of electrolyte at high potential on the positive electrode side. Therefore, increasing the migration number of lithium ions is a core key for alleviating polarization, realizing efficient and stable ion transmission, and further synchronously improving the stability of the positive-negative electrode interface. Currently, to address the challenges described above, researchers have developed a variety of electrolyte engineering strategies, all of which suffer from significant limitations. The high concentration electrolyte can construct stable SEI by forming an anion-dominant solvation structure, effectively inhibit dendrite, has the problems of ion conductivity and viscosity, but has limited substantial improvement of lithium ion migration number, and has limited practicality due to inherent high viscosity, high cost and poor wettability. Local high-concentration electrolyte and weak solvation electrolyte improve physical and chemical properties to a certain extent or realize similar solvation structures under conventional concentration, but respectively face the problems of reduced ion conductivity and high desolvation energy barrier, particularly the migration number of lithium ions is still low, and the problem of the coordination of rapid ion transmission and interface stability of a lithium metal battery cannot be fundamentally solved. While the solid electrolyte which is regarded as the final proposal can radically avoid dendrite penetration, the technical bottlenecks of low ionic conductivity at room temperature, large contact resistance of solid-solid interface and the like are not completely overcome. In the prior art, the modification and stabilization of a single electrode interface of a lithium metal battery are mainly focused. Patent solutions such as publication number CN118572193A, CN116864809A, CN116435594a protect the positive electrode by fluorinated solvents and optimize the negative electrode SEI of lithium metal batteries by additives. However, the dual effective protection of the high voltage positive electrode interface and the high activity lithium metal negative electrode interface of the lithium metal battery is still obviously insufficient, especially the verification under extreme conditions is insufficient. The current situation that the strategies are difficult to be compatible among ionic conductivity, interface stability and comprehensive practical feasibility, and the design thought of the current e