Non-aqueous Electrolyte Additive for Lithium Battery Overcharge Safety
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to internal temperature increases from overcharge and short circuits, leading to separator film melting, large short-circuit currents, heat generation, gas emission, and potential fires or explosions, necessitating an improvement in high-temperature and overcharge tolerance.
Innovation Solution
A non-aqueous electrolyte with a meta-stable state nitrogen-containing polymer additive is introduced, which forms a protective film on the positive electrode during overcharge, increasing the decomposition voltage and reaction temperature while reducing reaction heat, thereby enhancing safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the internal temperature of the battery is continuously raised due to overcharge or short circuit, then the separator film melts and breaks causing large short-circuit current, but the battery safety deteriorates with accelerated heating, fire, combustion or explosion
Solution Approach 1:
The patent applies preliminary action by forming a protective film on the positive electrode surface before thermal runaway occurs. The electrolyte additive reacts with the positive electrode material at lower voltages (4.2-4.8V) to create a stable coating that prevents further decomposition at higher temperatures, thereby preventing the cascade of thermal events rather than responding after overheating begins
Solution Approach 2:
The electrolyte additive serves as an intermediary substance between the positive electrode material and the bulk electrolyte. It forms a protective interface layer that mediates the interaction, preventing direct contact and reaction between the electrolyte and positive electrode at high temperatures, thus blocking the thermal runaway pathway
2Reliability
If the decomposition voltage of the electrolyte is increased to improve overcharge tolerance, then the reaction temperature is raised, but the reaction heat increases causing safety issues
Solution Approach 1:
The patent applies parameter changes by modifying the electrolyte composition to include specific additives (0.01-5 wt%) that alter the electrochemical parameters. The additive changes the decomposition voltage from typical values around 4.3V to higher values (4.5-4.8V), simultaneously changing the reaction characteristics to produce less heat during decomposition events
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 non-aqueous electrolyte with the meta-stable state nitrogen-containing polymer additive increases the decomposition voltage, postpones the reaction temperature by 15°C or more, and decreases reaction heat by about 40%, effectively improving battery safety during overcharge and high-temperature events caused by short-circuit currents.
Implementation Method 1
a protective film is formed on a positive electrode surface upon overcharge
Implementation Method 2
The electrolyte additive is a meta-stable state nitrogen-containing polymer
Data Source
AI summary
A non-aqueous electrolyte including a lithium salt, an organic solvent, and an electrolyte additive is provided. The electrolyte additive is a meta-stable state nitrogen-containing polymer formed by reacting Compound (A) and Compound (B). Compound (A) is a monomer having a reactive terminal functional group. Compound (B) is a heterocyclic amino aromatic derivative as an initiator. A molar ratio of Compound (A) to Compound (B) is from 10:1 to 1:10. A lithium secondary battery containing the non-aqueous electrolyte is further provided. The non-aqueous electrolyte of this disclosure has a higher decomposition voltage than a conventional non-aqueous electrolyte, such that the safety of the battery during overcharge or at high temperature caused by short-circuit current is improved.