Lithium Battery Electrolyte Additives for Stable SEI and Salt Protection
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Solution Overview
Problem
Existing electrolytes in lithium rechargeable batteries suffer from continuous salt degradation due to oxidative environments, leading to electrode instability and reduced durability, with existing additives failing to effectively suppress solvent decomposition and maintain performance.
Innovation Solution
An electrolyte additive with a specific structure and permittivity range, represented by Chemical Formula 1, is introduced to delay solvent decomposition and increase salt solubility, comprising a fluorine-substituted sulfonyl solvent as the main solvent, forming a stable film to enhance battery durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If perfluorinated cosolvent is used to induce salt-solvent aggregation and suppress decomposition, then salt decomposition is delayed, but lithium metal is continuously consumed to form film
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate additive as an intermediary substance that mediates between the perfluorinated cosolvent and lithium metal. This additive preferentially reacts with lithium metal to form a stable protective film, preventing the perfluorinated cosolvent from continuously consuming lithium metal while maintaining the salt-solvent aggregation effect for suppressing salt decomposition.
Solution Approach 2:
The patent optimizes the concentration ratio of components in the electrolyte system. By controlling the content of fluorinated cyclic carbonate additive (0.1-5 wt%) and perfluorinated cosolvent (5-30 vol%) relative to the main solvent, the system achieves optimal balance between suppressing salt decomposition and minimizing lithium metal consumption, transforming the chemical environment parameters to resolve the contradiction.
2Duration of action of stationary object
If additive is used to delay degradation, then durability is improved, but protective layer instability causes continuous additive consumption and increased electrode resistance
Solution Approach 1:
The fluorinated cyclic carbonate additive exhibits self-service characteristics by forming a stable protective film on the electrode surface that continuously protects the underlying structures. The additive molecules preferentially adsorb and react to form this self-healing protective layer, which automatically replenishes itself during battery operation, reducing the need for continuous additive consumption while maintaining durability.
Solution Approach 2:
The patent creates a composite protective layer structure combining fluorinated cyclic carbonate additive with perfluorinated cosolvent components. This composite film structure leverages the complementary properties of both components: the additive provides stable film formation and the cosolvent provides salt aggregation, resulting in a synergistic protective layer that reduces additive consumption while improving durability.
3Reliability
If perfluorinated solvent is used to suppress decomposition, then salt decomposition is delayed, but it is difficult to maintain agglomeration phenomenon at high temperatures
Solution Approach 1:
The patent applies local quality by creating distinct functional zones within the electrolyte system. The fluorinated cyclic carbonate additive concentrates at the electrode interface to form a stable protective film, while the perfluorinated cosolvent operates in the bulk electrolyte to maintain salt-solvent aggregation. This spatial separation of functions allows each component to optimize its performance at different locations, maintaining agglomeration stability at high temperatures.
Solution Approach 2:
The patent creates a composite electrolyte system combining fluorinated cyclic carbonate additive with perfluorinated cosolvent and main solvent. This composite formulation enhances thermal stability by distributing thermal management functions across multiple components: the additive provides thermally stable film formation while the cosolvent maintains aggregation structure, achieving synergistic thermal stability that neither component could achieve alone.
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 additive effectively delays solvent decomposition, maintains electrode stability, and enhances battery durability by preventing continuous consumption, thereby improving overall performance.
Implementation Method 1
The cosolvent can be included in the electrolyte to implement local overconcentration to delay the decomposition of the solvent
Implementation Method 2
increase the solubility of the salt to include an excess of salt
Implementation Method 3
the aim was to induce salt-solvent aggregation and suppress decomposition of salt and solvent by applying a perfluorinated cosolvent
Implementation Method 4
the perfluorinated solvent continuously consumes lithium metal to form a film by reacting with it
Implementation Method 5
increase the solubility of the salt to include an excess of salt
Data Source
AI summary
An electrolyte additive for a lithium rechargeable battery, having a permittivity of 1.0 F/m or less and represented by the following formula 1 is provided:A is carbon or silicon, and R1 and R2 can be various substituted or unsubstituted alkyl, heteroalkyl, cyclic, or aryl groups. The compound can exhibit a LUMO of −0.6 eV or higher and a HOMO of −6.8 eV or higher. Also provided is an electrolyte containing the additive, a LIFSI salt, and a main solvent comprising either an ether or a fluorine-substituted sulfamoyl, in a ratio of about 0.99:0.01 to about 0.95:0.05. A lithium rechargeable battery incorporating this electrolyte together with positive and negative electrodes and a separator, demonstrates enhanced performance and stability.