Non-Aqueous Electrolyte Additive for Stable High-Voltage Li-Ion SEI
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Solution Overview
Problem
Lithium secondary batteries face issues with electrode degradation due to side reactions and electrolyte deterioration, leading to metal ion elution, SEI passivation loss, and swelling, especially at high temperatures, affecting stability and performance.
Innovation Solution
Incorporating a cyclic phosphate-based additive in the non-aqueous electrolyte that forms a flexible and strong SEI film on the negative electrode, suppressing interfacial reactions and enhancing stability through poly-phosphoesterification and LiF formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high voltage and high energy density positive electrode active materials are used to increase battery capacity, then battery capacity and output are improved, but electrode surface film deteriorates and transition metal ions elute due to side reactions
Solution Approach 1:
The patent introduces a specific electrolyte additive (cyclic carboxylate compound with formula (1)) as an intermediary substance that mediates between the positive electrode and electrolyte. This additive preferentially reacts to form a protective interface film, preventing direct contact and harmful reactions between the high-voltage positive electrode and the bulk electrolyte, thereby suppressing transition metal ion elution while maintaining high capacity operation
2Use of energy by moving object
If the battery is driven at high voltage to increase capacity, then energy density is improved, but the film on electrode surface deteriorates due to side reactions
Solution Approach 1:
The patent applies preliminary action by having the cyclic carboxylate additive react first during initial charging cycles to form a stable protective film on the positive electrode surface before the battery is put into normal high-voltage operation. This pre-formed film acts as a barrier that prevents subsequent degradation during high-voltage charging and discharging cycles
3Adaptability or versatility
If the battery is exposed to high temperatures, then operational flexibility is improved, but deterioration is accelerated and gas is generated causing swelling
Solution Approach 1:
The patent converts the harmful effect of high temperature into a beneficial outcome by designing the cyclic carboxylate additive to undergo exothermic decomposition reactions at elevated temperatures that produce protective species. These decomposition products reinforce the SEI film and consume excess energy, transforming the thermal stress that would normally accelerate degradation into a mechanism that enhances thermal stability and prevents swelling
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 improves high-temperature cycle and storage characteristics by forming a stable electrode-electrolyte interface with low resistance, resulting in enhanced lithium secondary battery performance.
Implementation Method 1
when the negative electrode SEI layer is formed, a ring opening reaction proceeds, resulting in poly-phosphoesterification
Implementation Method 2
a ring opening reaction proceeds, resulting in poly-phosphoesterification
Implementation Method 3
-CF 3 at the terminal is easily reduced to the form of LiF
Data Source
AI summary
The present invention provides a non-aqueous electrolyte comprising an additive, represented by chemical formula 1, for a non-aqueous electrolyte. In chemical formula 1, A may be a cyclic phosphate group having 2 or 3 carbon atoms; R may be an alkylene or alkenylene group having 1 to 5 carbon atoms; and X may be a perfluoroalkyl group having 1 to 5 carbon atoms.