Non-Aqueous Electrolyte Composition for Fast-Charging Li-Ion Batteries
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Solution Overview
Problem
Existing lithium-ion batteries face challenges in achieving high energy density while maintaining good cycle performance and fast charging capabilities due to issues such as side reactions at high voltages, electrolyte decomposition, and increased internal resistance.
Innovation Solution
A non-aqueous electrolyte comprising a carboxylate solvent with a specific additive, represented by formula 1, is used to form a stable passivation film on electrodes, controlling the mass percentage contents of the additive, carboxylate, and electrolyte salt to enhance ion conductivity and reduce internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods (ammonium fluorosulfonate mixed with lithium hydroxide aqueous solution) are used to produce lithium fluorosulfonate, then lithium fluorosulfonate can be obtained, but the production process becomes complex and contamination with ammonia occurs
Solution Approach 1:
The invention extracts and eliminates the problematic intermediate step involving ammonium fluorosulfonate and cation exchange. Instead of using the conventional two-step process (forming ammonium salt then exchanging cations), the patent directly synthesizes lithium fluorosulfonate by reacting fluorosulfonic acid with lithium salt in non-aqueous solvent, removing the source of ammonia contamination and process complexity
Solution Approach 2:
The invention introduces a non-aqueous solvent as an intermediary medium to enable direct reaction between fluorosulfonic acid and lithium salt. This intermediary allows the reaction to proceed without forming the problematic ammonium intermediate, achieving both simplification and high purity
2Productivity
If LiClO4 is used as electrolyte, then electrolyte can be provided, but active oxygen is formed due to decomposition at electropositive potential which attacks the solvent and accelerates decomposition
Solution Approach 1:
The invention changes the chemical composition parameter of the electrolyte from LiClO4 to lithium fluorosulfonate (LiFSO3). This parameter change fundamentally alters the decomposition behavior at electropositive potentials, preventing the formation of active oxygen while maintaining high discharge capacity and improving battery performance
3Productivity
If CF3SO3Li, LiBF4 or LiPF6 are used as electrolyte, then electrolyte can be provided, but fluorine is formed due to decomposition at electropositive potential which attacks the solvent and accelerates decomposition
Solution Approach 1:
The invention changes the electrolyte composition from fluorine-containing salts (CF3SO3Li, LiBF4, LiPF6) to lithium fluorosulfonate. Although lithium fluorosulfonate contains fluorine in its structure, the fluorine is bonded in a stable configuration that prevents decomposition and release of free fluorine at electropositive potentials, thereby eliminating solvent attack while maintaining high productivity
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 solution improves the fast charging performance and cycle life of lithium-ion batteries by inhibiting electrolyte decomposition and reducing impedance, ensuring stable operation under high compaction and voltage conditions.
Implementation Method 1
A method involving the reaction of fluorosulfonic acid with a specific lithium salt in a non-aqueous solvent to produce high-purity lithium fluorosulfonate
Implementation Method 2
non-aqueous electrolytic solution containing lithium fluorosulfonate
Data Source
AI summary
In order to overcome the problem of an existing secondary battery being difficult to achieve a balance among energy density, cycle performance and fast charging performance, the present invention provides a non-aqueous electrolyte solution, which comprises an electrolyte salt, a non-aqueous organic solvent and an additive, wherein the non-aqueous organic solvent comprises a carboxylic ester; the additive comprises a compound as represented by structural formula 1: Formula I, where n is 0 or 1, A is selected from C or O, X is selected from II or III, R1 and R2 are each independently selected from H, IV or V, R1 and R2 are not selected from H at the same time, and X, R1 and R2 at least contain one sulfur atom; and the non-aqueous electrolyte solution satisfies the following conditions: 0.02 ≤ an/m ≤ 9, 0.01% ≤ a ≤ 5%, 5% ≤ m ≤ 70%, and 8% ≤ n ≤ 25%. Moreover, the present invention further discloses a secondary battery comprising the above non-aqueous electrolyte solution. According to the non-aqueous electrolyte solution provided in the present invention, the internal resistance of the battery is effectively reduced and the fast charging performance and the cycling performance of the battery are improved by limiting the content relation of the compound as represented by structural formula 1, the carboxylic ester and the electrolyte salt.