Positive Electrode Gas Generation for Overcharge Protection
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Solution Overview
Problem
Conventional nonaqueous electrolyte secondary batteries face challenges in maintaining battery performance while ensuring adequate gas generation for timely activation of the current cutoff mechanism during overcharging, as excessive gas generators can impair battery performance, and insufficient gas generation can delay mechanism activation.
Innovation Solution
Incorporating a compound with a saturated cyclic hydrocarbon group, such as cyclohexylbenzene, into the positive electrode active material layer to facilitate gas generation during overcharging, allowing the current cutoff mechanism to operate effectively without the need for a gas generator in the electrolyte, thus maintaining battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of gas generator is increased to ensure adequate gas generation for timely current cutoff mechanism activation, then the reliability of overcharge protection is improved, but the battery performance deteriorates due to increased resistance
Solution Approach 1:
The patent extracts the gas generator function from the electrolyte and relocates it to the positive electrode active material layer. This separation allows the gas generation function to be concentrated in a specific location where it can be more effective at activating the current cutoff mechanism, while reducing the overall amount of gas generator needed in the battery system, thereby maintaining battery performance.
Solution Approach 2:
The patent applies local quality by concentrating the gas generator in the positive electrode active material layer rather than distributing it throughout the electrolyte. This localized placement ensures that gas is generated at the source of overcharge, enabling timely activation of the current cutoff mechanism with a smaller total amount of gas generator, thus resolving the contradiction between protection reliability and battery performance.
2Productivity
If the amount of gas generator is reduced to maintain high battery performance, then the battery performance is improved, but the gas generation during overcharging is diminished causing delay in current cutoff mechanism activation
Solution Approach 1:
The patent implements preliminary action by pre-positioning the gas generator within the positive electrode active material layer structure. This ensures that when overcharging occurs, the gas generator is already in the optimal location to generate gas and activate the current cutoff mechanism, eliminating delays that would occur with reduced gas generator amounts distributed in the electrolyte.
3Reliability
If a gas generator is added to the electrolyte to ensure gas generation during overcharging, then the overcharge protection function is improved, but the battery performance deteriorates due to the gas generator acting as a resistance component
Solution Approach 1:
The patent extracts the gas generator from the electrolyte and relocates it to the positive electrode active material layer. This extraction eliminates the gas generator's negative impact on battery performance while preserving its essential function of generating gas during overcharging to activate the current cutoff mechanism.
Solution Approach 2:
The positive electrode active material layer serves as an intermediary medium that hosts the gas generator. This intermediary placement allows the gas generator to fulfill its protective function while being integrated into the electrode structure rather than floating in the electrolyte, thereby minimizing its impact on battery performance.
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 configuration ensures appropriate operation of the current cutoff mechanism during overcharging while maintaining high battery performance and stability, with the compound generating sufficient gas to activate the mechanism promptly without impairing the conductive material's function.
Implementation Method 1
CHB and BP generate hydrogen gas as a result of being activated by a polymerization reaction during overcharging
Implementation Method 2
the above-mentioned compound is composed so as to allow protons to detach from the above-mentioned saturated cyclic hydrocarbon group when the voltage reaches a predetermined voltage or higher
Data Source
AI summary
Provided is a nonaqueous electrolyte secondary battery that allows a current cutoff mechanism to operate appropriately while maintaining high battery performance. The nonaqueous electrolyte secondary battery according to the present invention includes: a battery assembly provided with a positive electrode having a positive electrode active material layer retained on a positive electrode current collector, a negative electrode and a separator; a battery case housing the electrode assembly together with a nonaqueous electrolyte; and a current cutoff mechanism. The positive electrode active material layer includes a positive electrode active material and a conductive material. A compound containing a saturated cyclic hydrocarbon group is retained in at least a portion of the conductive material. The content of the compound containing a saturated cyclic hydrocarbon group is 0.5% by mass or more based on a value of 100% by mass for the total solid content of the positive electrode active material layer.