Fluoroether Electrolyte Additives for High-Voltage Lithium-Ion Batteries
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Solution Overview
Problem
High-voltage lithium-ion batteries face issues with the decomposition of electrolytes and precipitation of transition metal elements, leading to reduced stability and performance due to increased oxidation activity and interface impedance, especially at high temperatures and low viscosities of additives which hinder electrode wetting.
Innovation Solution
An electrolyte composition including a lithium salt, organic solvent, and additives such as carbonate dimers, carboxylate dimers, sultone dimers, and fluoroethers, which form a stable protection film on the electrode surfaces, improving wetting and maintaining stability at high voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If film forming additives are added to the electrolyte to prevent decomposition at high voltage, then stability is improved, but interface impedance increases and transport kinetic performance deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by introducing fluoroether compounds with specific molecular structures (containing F, O, and C atoms in particular ratios) to modify the film forming mechanism. This allows the formation of stable protective films at high voltage without the excessive interface impedance caused by conventional additives, thus resolving the contradiction between stability and transport performance
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluoroether compounds with traditional carbonate solvents and lithium salts. This composite approach leverages the stability-enhancing properties of fluoroethers while maintaining the good ionic conductivity and wetting properties of conventional solvents, achieving both improved stability and preserved transport performance
2Reliability
If chainlike carbonate dimers, carboxylate dimers, sulfonate dimers or phosphate esters are used to improve high-temperature storage performance and cycle performance, then stability is improved, but viscosity increases and electrode wetting ability deteriorates
Solution Approach 1:
The patent modifies the molecular parameters of the electrolyte components by using fluoroether compounds with specific chain lengths and branching structures. These structural parameters are optimized to reduce viscosity while maintaining film-forming capabilities, thereby improving both wetting ability and cycle performance simultaneously
Solution Approach 2:
The fluoroether compounds act as intermediary substances that facilitate better contact between the electrolyte and electrode surfaces. Their molecular structure serves as a bridge between the conflicting requirements of low viscosity (for wetting) and high stability (for cycle performance), enabling both functions to coexist
3Use of energy by moving object
If high-voltage lithium-ion batteries are developed to increase energy density, then energy density is improved, but electrolyte decomposition and transition metal precipitation increase
Solution Approach 1:
The patent applies preliminary protective action by having the fluoroether compounds form stable protective films on the positive electrode surface before electrolyte decomposition can occur. This pre-formed barrier prevents the harmful electrochemical oxidizing reactions that would otherwise lead to electrolyte decomposition and transition metal precipitation at high voltages
Solution Approach 2:
The patent converts the high oxidation activity of the positive electrode material, which is normally harmful and causes electrolyte decomposition, into a beneficial effect. The fluoroether compounds are specifically designed to be oxidized at high voltages to form stable protective films, thereby utilizing the high voltage condition to create a protective layer rather than allowing direct decomposition of the bulk electrolyte
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 electrolyte composition enhances the cycle performance, rate performance, and service life of lithium-ion batteries by forming a stable film that prevents decomposition, allowing for higher working voltages up to 4.4-5.0V and improved capacity retention.
Implementation Method 1
add into the electrolyte a film forming additive which can form a film at the positive electrode
Implementation Method 2
the electrochemical oxidizing reaction of the non-aqueous electrolyte will readily occur on the surface of the positive electrode
Implementation Method 3
reduction reaction will occur to the transition metal elements in the positive electrode material, such as nickel, cobalt, manganese and so on, and thus such transition metal elements will precipitate out
Implementation Method 4
it is difficult for these materials to wet the electrode plate and separator as a result of too large viscosities thereof
Data Source
AI summary
The present application relates to the technical field of lithium-ion batteries and, specifically, relates to an electrolyte and a lithium-ion battery containing the electrolyte. The electrolyte of the present application includes a lithium salt, an organic solvent and additives, the additives include a fluorinated ether compound and an ester dimer compound, the ester dimer compound includes carbonate dimers, carboxylate dimers and sultone dimers.