Battery Electrode Bromine Gradient for Low-Temperature Cycle Life
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Solution Overview
Problem
The cycle characteristics of nonaqueous electrolyte secondary batteries deteriorate at low temperatures, despite existing techniques that improve cycle characteristics, further enhancement is needed to effectively suppress this deterioration.
Innovation Solution
An electrode for secondary batteries is designed with a current collector and an active material layer containing a bromine compound, where the active material layer is divided into regions with varying bromine compound content, with a higher content closer to the current collector to maintain fluidity and inhibit charge-discharge reactions at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a decomposition inhibitor is added to the positive electrode layer, then the decomposition of organic electrolyte is suppressed and cycle characteristics are improved, but the fluidity of liquid electrolyte deteriorates at low temperatures
Solution Approach 1:
The patent applies local quality by creating a gradient distribution of the bromine-containing decomposition inhibitor within the active material layer. The inhibitor concentration is highest at the current collector interface and decreases toward the electrode surface, allowing the inhibitor to protect against electrolyte decomposition at the critical interface while maintaining electrolyte fluidity in the bulk electrode region at low temperatures.
Solution Approach 2:
The patent changes the concentration parameter of the decomposition inhibitor spatially within the active material layer. By controlling the inhibitor concentration to be higher near the current collector and lower at the surface, the patent optimizes both the inhibition of electrolyte decomposition and the maintenance of electrolyte fluidity at low temperatures.
2Reliability
If the concentration of decomposition inhibitor at current collector-side surface is increased, then electrolyte decomposition is suppressed, but the harmful effect on low-temperature performance increases
Solution Approach 1:
The patent implements local quality by concentrating the decomposition inhibitor at the current collector-side region of the active material layer rather than uniformly distributing it. This localized concentration strategy provides strong protection against electrolyte decomposition at the current collector interface while minimizing the inhibitor's negative impact on electrolyte fluidity in the electrode bulk, thereby maintaining low-temperature charge-discharge performance.
Solution Approach 2:
The patent segments the active material layer into regions with different inhibitor concentrations. The region near the current collector has high inhibitor concentration for decomposition suppression, while the region toward the surface has lower concentration to maintain fluidity, effectively dividing the functional requirements spatially.
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 effectively suppresses the deterioration of cycle characteristics at low temperatures by ensuring the fluidity of the liquid electrolyte and maintaining high cycle performance.
Implementation Method 1
suppress the oxidative decomposition of liquid electrolyte at the interface with the lithium-transition metal composite oxide
Implementation Method 2
ensuring the fluidity of the liquid electrolyte and maintaining high cycle performance
Data Source
AI summary
The disclosed electrode for a secondary battery includes a current collector, and an active material layer disposed on a surface of the current collector. The active material layer includes at least an active material and an organic compound containing bromine. When the active material layer is divided into a first region and a second region having the same thickness, and the first region is closer to the current collector than the second region, a content A1 by mass of the organic compound relative to the active material in the first region is larger than a content A2 by mass of the organic compound relative to the active material in the second region. According to the present disclosure, the deterioration in cycle characteristics at low temperatures in a secondary battery can be suppressed.