Phosphonate Electrolyte Additives for High-Temperature Li-Ion Cycle Life
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Solution Overview
Problem
Lithium secondary batteries experience worsened electrochemical characteristics and performance issues due to solvent decomposition and gas generation during wide temperature use, particularly in high-temperature environments, leading to reduced discharge capacity and cycle life.
Innovation Solution
A nonaqueous electrolytic solution containing a phosphonate with specific alkenyl or alkynyl groups, combined with lithium salts and solvents, forms a strong surface film that prevents solvent decomposition and enhances discharge capacity retention and gas generation prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional nonaqueous electrolytic solution is used in a lithium secondary battery, then the battery can operate in a wide temperature range, but solvent decomposition occurs on the negative electrode surface during charging, generating decomposed products and gases that inhibit electrochemical reactions and worsen cycle properties
Solution Approach 1:
The patent applies preliminary action by introducing a phosphonate compound that proactively forms a protective film on the negative electrode surface before solvent decomposition can occur. This film acts as a barrier that prevents subsequent decomposition reactions, thereby maintaining cycle properties while operating in a wide temperature range.
Solution Approach 2:
The phosphonate compound serves as an intermediary substance between the negative electrode and the nonaqueous solvent. It mediates the interaction by forming a stable interface layer that prevents direct contact and harmful reactions between the solvent and electrode, thus eliminating decomposed products and gases while maintaining electrochemical performance.
2Quantity of substance
If metal lithium or alloy materials are used as negative electrode material to achieve high initial capacity, then capacity is improved, but micronized powdering is promoted during cycles, causing accelerated solvent decomposition and large worsening in battery performance
Solution Approach 1:
The phosphonate compound performs preliminary action by forming a stable protective film on the metal lithium or alloy surface before micronized powdering can occur. This film prevents the mechanical degradation and subsequent solvent decomposition that would otherwise accelerate during cycling, thereby extending cycle life while maintaining high initial capacity.
Solution Approach 2:
The patent converts the potentially harmful effect of using reactive metal lithium or alloy materials into a benefit by using the phosphonate compound to create a stable interface. The reactive materials provide high capacity, while the phosphonate film prevents their degradation, transforming what would be a liability into an advantageous high-capacity, long-cycle-life system.
3Adaptability or versatility
If the negative electrode material is subjected to micronized powdering or decomposed products accumulate, then lithium ion absorption and releasing cannot be smoothly performed, but the battery must maintain electrochemical characteristics in a wide temperature range
Solution Approach 1:
The phosphonate compound performs preliminary action by forming a protective film that prevents micronized powdering and decomposed product accumulation before they can occur. This maintains smooth lithium ion transport pathways while allowing the battery to operate across a wide temperature range without performance degradation.
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 solution improves discharge capacity retention and reduces gas generation in energy storage devices after high-temperature storage, maintaining performance across a wide temperature range.
Implementation Method 1
a solvent in a nonaqueous electrolytic solution is reductively decomposed on a negative electrode surface during charging
Implementation Method 2
a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent
Implementation Method 3
a positive electrode and a negative electrode, each containing a material capable of absorbing and releasing lithium ions
Data Source
AI summary
There is provided a nonaqueous electrolytic solution for an energy storage device which is a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent and contains a phosphonate represented by the following general formula (I), and an energy storage device using the same:wherein, R1 represents an alkenyl group having 2 to 6 carbon atoms or an alkynyl group having 3 to 6 carbon atoms, and R2 and R3 each independently represent an alkynyl group having 3 to 6 carbon atoms.