Electrolyte Additives for Stable SEI Film in Li-Ion Batteries
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Solution Overview
Problem
Lithium-ion batteries face issues with the formation of a thick and unstable Solid Electrolyte Interphase (SEI) film, leading to lithium precipitation and reduced battery capacity due to varying quality and resistance of the SEI film, which is influenced by additives and their amounts in the electrolyte.
Innovation Solution
An electrolyte composition including an organic solvent, a lithium salt, and additives such as cyanosulfone compounds and lithium fluorophosphate, which form a passive film on the electrode surface, suppressing reactions and improving film resistance, thereby enhancing cycle and storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte additives are used, then SEI film formation occurs, but the SEI film becomes thick and unstable leading to lithium precipitation and reduced battery capacity
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing specific cyanosulfone compounds (with R1 groups including halogen, alkyl, alkenyl, aryl, heteroaryl, and their substituted derivatives) in combination with lithium fluorophosphate compounds. This parameter change transforms the SEI film properties from thick and unstable to compact and stable, preventing lithium precipitation while maintaining reliable battery operation.
Solution Approach 2:
The patent employs a composite additive system combining cyanosulfone compounds and lithium fluorophosphate compounds in the electrolyte. This composite approach creates a synergistic effect where the combination of these two compound types produces a SEI film with superior stability and compactness compared to single additives, effectively preventing lithium precipitation and improving battery reliability.
2Reliability
If SEI film resistance is increased to improve stability, then lithium ion transport is blocked, but if resistance is decreased then film stability is compromised
Solution Approach 1:
The patent optimizes the concentration parameters of cyanosulfone compounds (0.01-5 wt%, preferably 0.1-2 wt%) and lithium fluorophosphate compounds (0.01-5 wt%, preferably 0.1-2 wt%) in the electrolyte. This precise parameter control enables the formation of an SEI film with balanced properties: sufficiently compact for stability while maintaining adequate lithium ion transport efficiency, avoiding both blockage and excessive resistance.
Solution Approach 2:
The patent creates a SEI film with non-uniform local composition and structure through the synergistic action of cyanosulfone and lithium fluorophosphate compounds. The film exhibits different properties at different locations: regions with appropriate resistance for stability coexist with regions that facilitate lithium ion transport, achieving overall balance between stability and ion transport efficiency.
3Productivity
If cycling is performed at high voltage to increase energy density, then SEI film degradation accelerates, but if voltage is limited then energy density is reduced
Solution Approach 1:
The patent modifies the electrolyte composition parameters by adding cyanosulfone compounds and lithium fluorophosphate compounds, which fundamentally changes the SEI film formation mechanism. This enables the battery to operate at high voltages (4.2V or higher) without severe SEI film degradation, achieving both high energy density and good cycle performance that would normally be contradictory.
Solution Approach 2:
The cyanosulfone and lithium fluorophosphate compounds act as intermediary substances that mediate between the high voltage stress and the SEI film stability. These additives form protective components in the SEI film that serve as intermediaries, shielding the electrode from high voltage degradation while allowing high voltage operation for increased energy density.
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 synergistic effect of cyanosulfone and lithium fluorophosphate compounds in the electrolyte significantly improves the cycle and storage performance of lithium-ion batteries, especially at high voltages and elevated temperatures, by forming a compact and stable SEI film.
Implementation Method 1
the additive comprises a cyanosulfone compound and a lithium fluorophosphate compound, wherein the cyanosulfone compound and the lithium fluorophosphate compound form a passive film on a surface of an electrode plate
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 comprises an organic solvent, a lithium salt and an additive, wherein the additive contains a cyanosulfone compound and a lithium fluorophosphate compound. When the electrolyte contains both the cyanosulfone compound and the lithium fluorophosphate at the same time, the cyanosulfone compound will form a passive film on the surface of the electrode of a high-voltage battery, so as to effectively suppress reaction between the electrolyte and the electrode, further, the lithium fluorophosphate can effectively suppress the decomposition of the lithium salt and improve the film resistance of the electrode. Under the synergistic effect of the two, the cycle performance of the lithium-ion battery is greatly improved, and the storage performance of the electrolyte is also significantly improved.