Secondary Battery Redox Shuttle Gas Evolution Overcharge Protection
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Solution Overview
Problem
In electric automobiles and large-scale power storage facilities, the high cost and inefficiency of using protection circuits for each battery, combined with the risk of thermal runaway due to redox shuttle agents, pose challenges in safely managing overcharge conditions and preventing short circuits.
Innovation Solution
A secondary battery design incorporating a redox shuttle agent and an organic solvent with a boiling point of 125° C or less, along with a separator made of aramid fiber or polyimide microporous structures, generates bubbles to block ion conduction and increase internal resistance during overcharge, preventing thermal runaway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection circuit is provided for each battery, then battery safety during overcharge is improved, but manufacturing cost and system complexity increase significantly
Solution Approach 1:
The battery system performs its own protection function through intrinsic mechanisms: the redox shuttle agent automatically triggers heat generation and gas evolution when overcharge voltage is detected, and the gas-filled separator passively blocks ion conduction pathways, eliminating the need for external electronic protection circuits
Solution Approach 2:
The invention replaces electronic protection circuits with a chemical-mechanical protection mechanism involving redox reactions, gas evolution, and physical blocking by the separator, thereby simplifying the system while maintaining safety functionality
2Reliability
If a low melting point separator is used, then ion conduction is facilitated under normal conditions, but the separator may melt during thermal runaway causing short circuit
Solution Approach 1:
The gas evolution mechanism activates before thermal runaway occurs, filling the separator pores with gas to block ion conduction pathways and prevent the separator from melting and causing short circuit during subsequent thermal events
Solution Approach 2:
The evolved gas acts as an intermediary substance that fills the separator pores and blocks ion conduction, preventing direct contact between electrodes and avoiding short circuit even when the separator is exposed to high temperatures
3Stability of the object's composition
If a high heat resistant separator is used, then thermal stability is improved, but electrolysis of the electrolytic solution may occur at elevated temperatures
Solution Approach 1:
The redox shuttle agent triggers gas evolution at moderate temperatures before electrolysis can occur, blocking ion conduction pathways and preventing electrolysis of the electrolytic solution even when high heat resistant separators are present
4Reliability
If the redox shuttle agent operates at high potential, then overcharge protection is achieved, but heat generation increases causing temperature rise
Solution Approach 1:
The heat generated by the redox shuttle agent during overcharge protection is converted into a beneficial effect by triggering gas evolution from the electrolytic solution, which then blocks ion conduction pathways and prevents thermal runaway, thereby transforming the harmful heat into a protective mechanism
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
This design effectively stops the battery function before thermal runaway occurs, ensuring safety by blocking ion conduction and maintaining insulation between electrodes, even under abnormal heat conditions.
Implementation Method 1
the electrolytic solution contains a redox shuttle agent and an organic solvent having a boiling point of 125° C. or less
Implementation Method 2
the redox shuttle agent generates heat during operation
Implementation Method 3
when a large charging current is applied in the fully charged state, the heat radiation cannot catch up and the temperature of battery due to the heat generation of the redox shuttle agent rises significantly
Implementation Method 4
the separator comprises aramid fiber assembly, aramid micropore structure, polyimide microporous structure or polyphenylenesulfide microporous structure
Data Source
AI summary
Provided is a secondary battery which uses a heat generating reaction of the redox shuttle agent to achieve stopping a function of the battery by blocking ion conduction and rapidly increasing an internal resistance by means of volatilized non-aqueous solvent when an abnormality such as overcharge occurs. A secondary battery 1 comprises a battery element comprising a positive electrode 11, a negative electrode 12, a separator 13, and an electrolytic solution, and a casing sealing the battery element. The electrolytic solution comprises a redox shuttle agent and an organic solvent having a boiling point of 125° C. or less. The separator 13 comprises aramid fiber assembly, aramid microporous structure, polyimide microporous structure or polyphenylenesulfide microporous structure, and polyphenylenesulfide, and has an average void size of 0.1 μm or more.