Non-Aqueous Electrolyte Additives for Stable Battery SEI Films
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with increased resistance and reduced life due to continuous electrolyte decomposition at the negative electrode, exacerbated by SEI films rich in organic components that hinder electron conductivity and cause lithium precipitation.
Innovation Solution
A non-aqueous electrolyte containing cyclic sulfate compounds and inorganic additives forms a highly elastic and stable SEI film on the negative electrode, incorporating inorganic components like Li2S, ROSO2Li, carbonate, LiF, borate, and phosphate, enhancing ion conductivity and electron blocking capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte additives are used to form SEI film on negative electrode, then electrolyte decomposition is inhibited, but organic components in SEI film cause electron conductivity issues and lithium precipitation
Solution Approach 1:
The patent changes the chemical composition parameters of the SEI film by introducing inorganic additives (Li2S, ROSO2Li, LiF, borate, phosphate) to replace organic components. This parameter change transforms the SEI film from organic-rich to inorganic-rich composition, thereby improving electron blocking capability and preventing lithium precipitation while maintaining electrolyte stability.
Solution Approach 2:
The patent creates a composite SEI film structure combining multiple inorganic components (Li2S, ROSO2Li, carbonate, LiF, borate, phosphate) with the electrolyte. This composite material approach produces an SEI film with enhanced properties: high ion conductivity from the inorganic components while providing effective electron blocking and preventing the harmful effects of organic-rich SEI films.
2Reliability
If SEI film is formed to protect negative electrode, then electrolyte decomposition is reduced, but film stability deteriorates under volume changes and mechanical stress
Solution Approach 1:
The patent changes the mechanical and chemical parameters of the SEI film by incorporating inorganic components with higher mechanical strength and chemical stability. These inorganic components (particularly LiF, borate, and phosphate) provide structural rigidity and resistance to volume changes, maintaining film stability during battery cycling while preserving the protective function against electrolyte decomposition.
3Reliability
If electrolyte additives are added to form passivation layer, then lithium consumption reaction is inhibited, but battery life deteriorates due to increased impedance
Solution Approach 1:
The patent changes the electrical parameters of the SEI film by replacing organic components with inorganic components that have superior electron blocking properties. The inorganic SEI film maintains low impedance for lithium ion transport while providing excellent electron blocking, thereby inhibiting lithium consumption reactions and extending battery life without causing the impedance increase associated with organic-rich SEI films.
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 SEI film effectively blocks electron decomposition, improving cycling and storage performance, and prolonging battery life by stabilizing the film against volume changes and mechanical stress.
Implementation Method 1
formation of a homogeneous, dense, stable, low-impedance and well-adhesive solid electrolyte interface (SEI) film
Implementation Method 2
continuous reduction of an electrolyte at a negative electrode during charging
Implementation Method 3
The SEI film is a good lithium ion conductor as well as a poor electron conductor, which inhibits continuation of a lithium consumption reaction
Implementation Method 4
forms a highly elastic and stable SEI film on the negative electrode
Data Source
AI summary
A non-aqueous electrolyte solution comprises additives, wherein the additives comprise a first additive and a second additive, the first additive is any one or more cyclic sulfate compounds having a structure represented by general formula (I), and the second additive comprises one or more of lithium monofluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, a compound represented by general formula (II), and fluorosulfonates.