Zwitterionic Electrolyte Additives for High-Temperature Li-Ion Cells
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Solution Overview
Problem
Lithium-ion batteries face degradation issues due to the thermal decomposition of lithium salts, leading to the formation of Lewis acids that damage the solid electrolyte interphase (SEI) and increase resistance, especially at high temperatures, which affects their durability and cycle performance.
Innovation Solution
A zwitterionic compound is used as an electrolyte solution additive that scavenges decomposition products and forms a stable film on the electrodes, enhancing ionic conductivity and maintaining SEI integrity, thereby improving high-temperature stability and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as lithium salt to achieve suitable battery characteristics, then battery performance is improved, but thermal decomposition occurs at high temperatures generating Lewis acid that damages SEI and increases resistance
Solution Approach 1:
A zwitterionic compound is introduced as an intermediary substance between the LiPF6 lithium salt and the SEI film. This compound preferentially reacts with the lithium salt decomposition products (Lewis acids like PF5 and HF) to form a protective complex, preventing these harmful substances from attacking and damaging the SEI film. The zwitterionic compound acts as a sacrificial scavenger that protects the critical SEI interface from chemical degradation.
Solution Approach 2:
The invention converts the harmful thermal decomposition reaction of LiPF6 into a beneficial process by directing the decomposition toward forming a zwitterionic compound that actively scavenges decomposition products. The Lewis acid generation is not prevented, but the harmful effect is transformed into a useful scavenging mechanism where the zwitterionic compound binds PF5 and HF, converting these damaging substances into stable complexes that protect the battery system.
2Power
If high temperature operation is performed, then power output is improved, but SEI film degradation and resistance increase occur due to Lewis acid attack
Solution Approach 1:
The zwitterionic compound is pre-introduced into the electrolyte system to perform preliminary protection before high-temperature operation begins. During initial cycles and before significant thermal decomposition occurs, the zwitterionic compound establishes a protective chemical environment by scavenging any early decomposition products and forming a stabilized interface. This preliminary anti-action prevents the cumulative damage that would otherwise occur during sustained high-temperature operation.
3Stability of the object's composition
If transition metal dissolution is suppressed, then electrode stability is improved, but additional measures are needed to maintain SEI passivation ability
Solution Approach 1:
The zwitterionic compound performs multiple functions simultaneously: it scavenges Lewis acid decomposition products (PF5, HF), protects the SEI film from degradation, suppresses transition metal dissolution from the cathode, and maintains overall electrode stability. This single compound addresses multiple degradation pathways that occur during battery operation, providing comprehensive protection without requiring separate additives for each function.
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 suppresses the dissolution of transition metals and scavenges by-products, reducing initial resistance and enhancing the high-temperature durability and cycle performance of lithium secondary batteries.
Implementation Method 1
since a nitrogen atom of the cationic moiety in the molecular structure acts as a Lewis base, it may effectively scavenge a Lewis acid generated as the decomposition product of the lithium salt
Implementation Method 2
a sulfate group (-SO4), as the anionic moiety of the compound represented by Formula 1, may form a stable film on the surface of the positive electrode or negative electrode
Implementation Method 3
it may further improve the ionic conductivity of the non-aqueous electrolyte solution by the zwitterionic structure
Implementation Method 4
it may effectively suppress the dissolution of the transition metal from the positive electrode
Data Source
AI summary
An electrolyte solution additive for a secondary battery, a non-aqueous electrolyte solution including the same, and a lithium secondary battery including the same are disclosed herein. To be specific, the above non-aqueous electrolyte solution includes the electrolyte solution additive comprising the compound represented by Formula 1.