Graphite Negative Electrode Aspect Ratio and Unsaturated Cyclic Carbonate
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Solution Overview
Problem
Conventional nonaqueous electrolyte energy storage devices, particularly those using graphite as a negative active material, face challenges in maintaining high power characteristics over long-term use due to deterioration of the electrode materials.
Innovation Solution
The use of a nonaqueous electrolyte energy storage device with a negative electrode containing a solid graphite particle of specific aspect ratio and an appropriate amount of unsaturated cyclic carbonate, which forms a uniform film on the graphite surface to enhance durability and power characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If graphite is used as a negative active material in conventional nonaqueous electrolyte energy storage devices, then high energy density is achieved, but power characteristics deteriorate with long-term use
Solution Approach 1:
The patent changes the physical and chemical parameters of the graphite particles by controlling their aspect ratio to be 5 or less and using solid graphite particles, which fundamentally alters how the electrolyte interacts with the graphite surface. This parameter change enables the formation of a stable SEI film that prevents further deterioration, thus maintaining power characteristics while preserving high energy density
Solution Approach 2:
The patent creates a composite structure where solid graphite particles with controlled aspect ratios are combined with a specifically formulated nonaqueous electrolyte containing unsaturated cyclic carbonate. This composite approach allows the electrolyte to form a protective interface layer on the graphite surface, solving the durability issue while maintaining the high energy density benefit of graphite
2Reliability
If unsaturated cyclic carbonate is added to the nonaqueous electrolyte to improve durability, then power characteristics are maintained, but excessive film formation occurs on the graphite surface
Solution Approach 1:
The patent precisely controls the concentration parameter of unsaturated cyclic carbonate in the electrolyte and matches it with graphite particles of specific aspect ratio (5 or less). This parameter optimization ensures that enough electrolyte is present to form a complete protective film without excess that would lead to thick, harmful film formation, thus balancing durability improvement with minimal substance consumption
Solution Approach 2:
The patent promotes the formation of a stable solid electrolyte interface (SEI) film that acts as a protective copy or replica layer on the graphite surface. This SEI film replicates the ideal interface structure that prevents further electrolyte decomposition and graphite degradation, allowing the system to maintain stable performance without continuous consumption of unsaturated cyclic carbonate
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 results in a nonaqueous electrolyte energy storage device with improved power characteristics that are maintained even after long-term use, as the solid graphite particles with low aspect ratios and optimal unsaturated cyclic carbonate amounts prevent excessive film formation and edge surface exposure.
Implementation Method 1
the unsaturated cyclic carbonate may be decomposed during initial charge-discharge to form a film on the particle surface of the negative active material
Data Source
AI summary
A nonaqueous electrolyte energy storage device according to one aspect of the present invention is a nonaqueous electrolyte energy storage device including: a negative electrode including a negative electrode material layer; and a nonaqueous electrolyte containing an unsaturated cyclic carbonate, in which the negative electrode material layer contains a solid graphite particle with an aspect ratio of 1 or more and 5 or less, and the amount of substance of the unsaturated cyclic carbonate with respect to a surface area of the negative active material layer is 0.03 mmol/m2 or more and 0.08 mmol/m2 or less.