Ammonium Azide Electrolyte Additive for Lithium Battery SEI Stability
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Solution Overview
Problem
Lithium secondary batteries face degradation and safety concerns due to the instability of lithium salts at high temperatures, leading to increased interfacial resistance, capacity reduction, and potential swelling, as they are sensitive to moisture and thermal decomposition, which damages the Solid Electrolyte Interphase (SEI) layer.
Innovation Solution
Incorporating a solid salt with an ammonium-based cation and an azide anion into the electrolyte solution, which forms a stable and dense SEI layer, reducing side reactions and maintaining battery performance even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If lithium salt is used as electrolyte, then high energy density and long cycle lifetime are achieved, but thermal decomposition occurs at high temperature generating hydrofluoric acid that damages the battery
Solution Approach 1:
The patent introduces a film-forming additive as an intermediary substance between the lithium salt and the electrode surfaces. This additive preferentially decomposes to form a protective SEI layer that acts as a barrier, preventing direct contact and harmful reactions between the unstable lithium salt and water or electrode materials, thus resolving the thermal stability issue while maintaining the electrochemical benefits of lithium salts
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by adding specific film-forming additives (0.01-5% by weight) to change the decomposition behavior and reaction products. This parameter change transforms the harmful decomposition pathway of lithium salts into a beneficial protective film formation process, improving high-temperature reliability without sacrificing cycle lifetime
2Ease of operation
If conventional electrolyte solution is used, then battery operation is maintained, but SEI layer is damaged at high temperature leading to continuous regeneration and increased resistance
Solution Approach 1:
The patent applies preliminary action by having the film-forming additive decompose first during initial charging cycles to create a stable SEI layer before the battery enters normal operation. This pre-formed protective layer prevents subsequent damage and continuous regeneration that would otherwise occur at high temperatures, ensuring long-term operational stability
Solution Approach 2:
The patent converts the harmful thermal decomposition of the film-forming additive into a beneficial process. The controlled decomposition at elevated temperatures during formation creates a robust SEI layer that is specifically designed to be thermally stable, transforming what could be a harmful side reaction into a protective mechanism that prevents further degradation
3Object-generated harmful factors
If lithium salt decomposes at high temperature, then hydrofluoric acid is generated causing side reactions, but no effective prevention method is provided
Solution Approach 1:
The film-forming additive serves as a sacrificial intermediary that decomposes in place of the lithium salt, forming a protective barrier that prevents the generation of hydrofluoric acid and other harmful byproducts. This intermediary layer blocks the decomposition pathway that would otherwise produce corrosive substances
Solution Approach 2:
The patent converts the potential harm of additive decomposition into a benefit by designing additives that decompose into harmless or beneficial products while forming protective films. The decomposition reactions are engineered to produce stable compounds rather than corrosive hydrofluoric acid, transforming a side reaction into a protective mechanism
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 use of the ammonium-based azide additive enhances the high-temperature storage characteristics of lithium secondary batteries by maintaining capacity retention and discharge capacity, reducing the thickness increase and safety risks associated with battery swelling.
Implementation Method 1
The SEI layer, which may be formed on the surface of the negative electrode by reaction of a polar non-aqueous carbonate solvent with lithium ions of the electrolyte solution during initial charging of a lithium secondary battery, may serve as a protective layer by inhibiting decomposition of the carbonate electrolyte solution
Implementation Method 2
During charging, lithium ions released from the positive active material are intercalated into a negative active material layer. During discharging, the lithium ions released from the negative active material layer are intercalated into the positive active material
Implementation Method 3
The electrolyte solution serves as a migration medium of lithium ions between the negative electrode and the positive electrode
Data Source
AI summary
An electrolyte solution for a lithium secondary battery includes a lithium salt, an organic solvent, and a solid salt as an additive, the solid salt including at least one cation selected from ammonium-based cations and an azide anion (N3—). Using the electrolyte solution including the additive may provide a lithium secondary battery with improved high-temperature retention characteristics.