Lithium-ion Battery Cathode Coating for High-Voltage Stability
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Solution Overview
Problem
High-voltage lithium-ion batteries face challenges in high-temperature performance due to electrolyte decomposition and metal ion dissolution, which deteriorate battery performance, and existing solutions like phosphate ester compounds either improve high-temperature performance at the expense of low-temperature performance or are inefficient in industrial production.
Innovation Solution
A lithium-ion battery design featuring a cathode with specific metal oxide or fluoride coatings and an anode with unsaturated phosphate ester compounds, which form a polymer film to reduce impedance and enhance both high-temperature and low-temperature performance by suppressing electrolyte decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the charging voltage of lithium-ion batteries is increased to achieve higher energy density, then the energy density is improved, but the dissolution of metal ions of the cathode material increases, leading to catalysis of electrolyte decomposition and destruction of the passivation film on the anode
Solution Approach 1:
The cathode surface is pre-coated with a protective layer containing metal oxide and/or metal fluoride particles before battery operation. This preliminary coating prevents metal ion dissolution and electrolyte decomposition from the outset, allowing the battery to operate at high charging voltages (above 4.3V) without suffering the typical degradation effects. The coating acts as a barrier that maintains anode passivation film integrity even under high-voltage conditions.
Solution Approach 2:
The inorganic coating layer serves as an intermediary between the cathode active material and the electrolyte. This intermediate layer prevents direct contact and harmful interactions between the cathode material and electrolyte, thereby suppressing metal ion dissolution and electrolyte decomposition while allowing lithium ion transport. The coating mediates the high-voltage operation by isolating the reactive cathode surface from the electrolyte.
2Temperature
If phosphate ester compound containing a triple bond is used as additive to improve high-temperature performance, then the high-temperature performance is significantly improved, but the low-temperature discharge performance is significantly lowered
Solution Approach 1:
The invention uses a composite coating system combining inorganic particles (metal oxide and/or metal fluoride) with an organic binder. The inorganic particles provide high-temperature stability and suppress electrolyte decomposition, while the organic binder ensures proper adhesion and flexibility. This composite structure achieves both high-temperature performance improvement and maintains low-temperature discharge performance, overcoming the limitations of pure phosphate ester additives.
3Temperature
If inorganic particles are coated on the cathode active material to improve high-temperature performance, then the high-temperature performance is improved, but the extent of improvement is insufficient for high-voltage batteries
Solution Approach 1:
The invention optimizes the coating parameters by controlling the content of inorganic particles (0.1-5 wt%, preferably 0.5-3 wt%) and selecting specific metal oxides and metal fluorides. This parameter optimization enhances the high-temperature performance to a level sufficient for high-voltage batteries (charging voltage > 4.3V), overcoming the insufficient improvement provided by conventional coating methods. The precise control of coating composition and amount enables the coating to effectively suppress electrolyte decomposition even at high voltages.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The battery achieves improved high-temperature cycling and storage performance while maintaining low-temperature discharge efficiency, with the unsaturated phosphate ester compound forming a stable polymer film that adheres firmly to the cathode surface, reducing impedance and preventing electrolyte decomposition.
Implementation Method 1
the unsaturated phosphate ester compound forming a stable polymer film that adheres firmly to the cathode surface
Implementation Method 2
Coating the cathode active material with inorganic particles is a common method for improving the high-temperature performance of high-voltage batteries
Data Source
AI summary
A lithium-ion battery, comprising a cathode, an anode, and a non-aqueous electrolyte; the cathode comprises a cathode active material and a metal oxide and/or metal fluoride coating which covers the surface of the cathode active material; the cathode active material is at least one of materials illustrated in general formula I or II: formula I: LixNiyM1-yO2, wherein 0.5≤x≤1.2, 0.5≤y≤1, and M is selected from at least one of Co, Mn, Al, Ti, Fe, Zn, Zr, Cr, and formula II: LikCozL1-zO2, wherein 0.5≤k≤1.2, 0.5<z≤1, and L is selected from at least one of Ni, Mn, Al, Ti, Fe, Zn, Zr, Cr; the anode comprises an anode active material, which is selected from at least one of graphite or silicon-containing carbon material; and the non-aqueous electrolyte contains at least one of unsaturated phosphate compounds. According to the lithium-ion battery, the charge cut-off voltage of the lithium-ion battery reaches 4.3 V or more by means of a synergistic effect of the unsaturated phosphate compounds and the coating at the surface of the cathode active material.