Lithium Battery Electrolyte SEI Stability
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Solution Overview
Problem
Conventional lithium batteries face challenges with the stability of the solid electrolyte interface (SEI) layer at high temperatures, leading to reduced lifespan due to irreversible reactions and gas production, which affects the battery's performance and longevity.
Innovation Solution
The use of a disultone-based compound and an oxalate-based compound, such as lithium difluoro(oxalato)borate (LiFOB) or lithium bis(oxalato)borate (LiBOB), in combination with an organic solvent, forms a stable SEI layer that reduces direct current internal resistances and gas generation, enhancing the battery's lifespan and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional additives are used to stabilize the SEI layer, then the SEI layer formation is improved, but the stability of the SEI layer deteriorates at high temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific cyclic carboxylate compound with particular molecular structure characteristics (cyclic structure, carboxylate functional group, specific carbon chain length), which fundamentally alters the SEI layer formation mechanism and composition to achieve high-temperature stability
Solution Approach 2:
The patent creates a composite SEI layer through the synergistic interaction between the cyclic carboxylate compound and other electrolyte components, forming a multi-component protective layer that combines the benefits of different materials to achieve both stability and high-temperature resistance
2Reliability
If LiPF6 is used as the lithium salt, then ion conductivity is improved, but gas production increases due to reactions with the organic solvent
Solution Approach 1:
The cyclic carboxylate compound acts as an intermediary substance that mediates between the lithium salt and organic solvent, forming a protective interface layer that prevents direct harmful reactions while maintaining ion transport, thus eliminating gas production while preserving conductivity
3Reliability
If carbonate-based non-aqueous polar solvent is used, then ion conductivity is improved, but irreversible reactions occur during charging/discharging
Solution Approach 1:
The cyclic carboxylate compound performs preliminary action by forming a stable SEI layer during initial electrolyte decomposition, which then prevents subsequent irreversible reactions between the carbonate solvent and electrode materials during normal charging/discharging cycles, thereby reducing charge loss
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 proposed electrolyte composition improves the thermal stability of the SEI layer, reducing direct current internal resistances and gas production, thereby extending the lithium battery's lifespan and maintaining performance even at elevated temperatures.
Implementation Method 1
A passivation layer, such as a solid electrolyte interface (SEI) layer, is formed on a surface of a negative electrode by the irreversible reaction. The SEI layer reduces or prevents decomposition of an electrolytic solution and serves as an ion tunnel during charging/discharging of the lithium battery.
Implementation Method 2
a lithium battery undergoes an irreversible reaction using an excessive amount of charge during charging/discharging of the battery, due to a side reaction between an electrolytic solution and a negative electrode/positive electrode
Data Source
AI summary
Provided are an electrolyte for a lithium battery and a lithium battery including the electrolyte, wherein the electrolyte includes a disultone-based compound represented by Formula 1; an oxalate-based compound; and an organic solvent:wherein, in Formula 1, A1, A2, A3, and A4 are each independently a substituent-substituted or unsubstituted C1-C5 alkylene group; a carbonyl group; or a sulfinyl group.