Chelating Electrolyte Additives for Overcharge-Safe Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to thermal runaway caused by overcharge, which existing redox shuttle additives cannot adequately address, especially in high-capacity batteries.
Innovation Solution
A lithium battery electrolyte comprising a non-aqueous organic solvent, a lithium salt, and an additive stable between 2.5 to 4.8 V, capable of forming chelating complexes with transition metals, which traps metal impurities and converts overcharge modes to shut-down modes, ensuring safety during high-temperature storage and overcharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redox shuttle additives are used to prevent thermal runaway, then battery safety is improved, but the additives cannot provide sufficient safety for high-capacity batteries and may cause voltage drops
Solution Approach 1:
The patent introduces a mediator substance (redox shuttle additive) that facilitates electron transfer between electrodes during overcharge conditions. This intermediary mechanism allows the battery to safely dissipate excess energy without direct thermal runaway, while the specific chemical properties of the additive minimize voltage drop by maintaining efficient charge transfer pathways.
Solution Approach 2:
The patent modifies key parameters of the redox shuttle additive including its redox potential, molecular structure, and concentration in the electrolyte. By optimizing these parameters, the additive provides sufficient safety for high-capacity batteries while minimizing energy loss. The redox potential is specifically tuned to activate only under overcharge conditions, preventing voltage drop during normal operation.
2Quantity of substance
If the battery capacity is increased, then energy density is improved, but the risk of thermal runaway and safety issues increases
Solution Approach 1:
The patent implements preliminary protective action by incorporating redox shuttle additives into the electrolyte before battery operation. These additives proactively prevent thermal runaway by establishing a safety mechanism that activates during overcharge conditions. The additive creates a protective chemical environment that suppresses harmful reactions even as battery capacity increases, allowing high-capacity batteries to operate safely.
3Reliability
If redox shuttle additives are added to the electrolyte, then overcharge reactions are inhibited, but the additives consume overcharge current and may affect battery performance
Solution Approach 1:
The patent employs a dynamic redox shuttle mechanism where the additive continuously cycles between oxidized and reduced states during battery operation. This dynamic behavior allows the additive to adaptively respond to charge conditions, providing overcharge prevention only when necessary while remaining inactive during normal operation. The reversible redox reactions maintain battery performance by not interfering with standard charge-discharge cycles.
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 electrolyte effectively prevents voltage drops and ensures battery safety by stabilizing the electrolyte and electrodes, maintaining performance and safety even under high-temperature conditions and during overcharge.
Implementation Method 1
an additive which is stable at voltages ranging from about 2.5 to about 4.8 V and capable of forming a chelating complex with a transition metal
Implementation Method 2
an aromatic compound, such as an oxidation-reduction agent, or 'redox shuttle additive,' has been added to the electrolyte
Implementation Method 3
U.S. Pat. No. 5,879,834 to Mao discloses the use of electrochemically polymerized aromatic compounds, such as biphenyl, 3-chlorothiophene, furan, etc., to improve battery safety by increasing the internal resistance of the battery during unusual overvoltage conditions
Data Source
AI summary
The present invention relates to an electrolyte for a lithium battery and a lithium battery comprising the same. The electrolyte includes a non-aqueous organic solvent, a lithium salt, and a first additive capable of forming a chelating complex with a transition metal and which is stable at voltages ranging from about 2.5 to about 4.8 V.