Non-aqueous Electrolyte Additives for Thermal Runaway Prevention
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to internal heat generation and flammability, leading to potential ignition and explosion, especially at high temperatures, and existing solutions like high-melting-point separators and flame-retardant additives either compromise battery capacity or cause irreversible reactions.
Innovation Solution
A non-aqueous electrolyte containing 1-10 wt% of a fluoroethylene carbonate compound and 1-10 wt% of an aliphatic di-nitrile compound, such as succinonitrile, which form a synergistic effect to prevent ignition and explosion by controlling exothermic reactions and forming a protective layer on the cathode, thereby enhancing thermal stability and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based separator with high melting point is used to prevent internal short circuits, then battery safety is improved, but film thickness must be increased which reduces electrode loading amount and battery capacity
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a boron-containing compound with specific molecular structure (formula 1) and controlling its concentration (0.01-5 wt%), which modifies the electrolyte's thermal stability and flame retardancy properties without requiring separator thickness changes
Solution Approach 2:
The boron-containing compound acts as an intermediary substance that mediates between the electrolyte and potential ignition sources. It forms a protective layer or modifies the electrolyte's chemical behavior to prevent flame propagation and thermal runaway, thereby improving safety without affecting the separator's physical structure
2Reliability
If a phosphorus-based flame retardant compound is added to the electrolyte to prevent ignition, then battery safety is improved, but irreversible reactions including Li corrosion are accelerated which reduces battery performance and efficiency
Solution Approach 1:
The patent changes the chemical parameter of the flame retardant by using a boron-containing compound instead of phosphorus-based compounds. This substitution fundamentally alters the chemical interaction mechanism with lithium, providing flame retardancy without accelerating Li corrosion or causing significant irreversible reactions
Solution Approach 2:
The boron-containing compound serves as a sacrificial protective agent that preferentially reacts with harmful species or forms protective layers, consuming itself to protect the lithium and other battery components from degradation, thereby maintaining battery efficiency while providing safety
3Use of energy by moving object
If the battery is exposed to high temperatures for long period due to internal heat generation, then energy density and capacity are improved, but the stable structure of the battery deteriorates due to gas generation from electrolyte oxidation causing ignition and explosion
Solution Approach 1:
The patent converts the harmful effect of high temperature exposure by using the boron-containing compound to form a stable protective layer or modify the electrolyte's decomposition behavior. This transforms the thermal stress condition into an opportunity for the additive to activate its protective function, preventing gas generation and ignition while allowing the battery to operate at high energy density
Solution Approach 2:
The boron-containing compound acts as a thermal intermediary that absorbs or mitigates the harmful effects of high temperature and electrolyte oxidation. It mediates between the thermal energy and the battery components, preventing direct damage from heat-induced gas generation and ignition
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 combination of fluoroethylene carbonate and succinonitrile additives significantly improves battery safety by preventing thermal runaway and maintaining performance even at high temperatures, reducing gas generation, and extending cycle life, while maintaining high capacity.
Implementation Method 1
forming a protective layer on the cathode
Implementation Method 2
a large amount of heat is generated due to the reaction between lithium transition metal oxide and the carbonate solvent
Data Source
AI summary
Disclosed is an electrochemical device comprising a cathode having a complex formed between a surface of a cathode active material and an aliphatic di-nitrile compound; and a non-aqueous electrolyte containing 1-10 wt % of a compound of Formula 1 or its decomposition product based on the weight of the electrolyte.