Graphite Anode Electrolyte Design for Capacity Retention
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Solution Overview
Problem
Graphite-based negative active materials in energy storage devices experience non-uniform expansion and contraction during charge-discharge cycles, leading to a decrease in capacity retention rate.
Innovation Solution
Incorporating solid graphite particles with an aspect ratio of 1 to 5 as the main component in the negative electrode and using a nonaqueous electrolyte containing an imide salt with phosphorus or sulfur to form a protective film on the surface of the negative active material, suppressing uneven expansion and contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite is used as negative active material to increase energy density, then energy density is improved, but capacity retention rate after charge-discharge cycles deteriorates due to non-uniform expansion and contraction
Solution Approach 1:
The invention changes the physical and chemical parameters of the electrolyte by introducing specific imide salts containing phosphorus or sulfur. These parameter changes lead to the formation of a protective film on the graphite surface that suppresses non-uniform expansion and contraction during charge-discharge cycles, thereby improving capacity retention rate while maintaining high energy density
Solution Approach 2:
The invention creates a composite structure by forming a protective film on the graphite surface through the interaction between graphite and imide salt additives. This composite material system combines the high capacity of graphite with the protective properties of the imide salt-derived film, resolving the contradiction between energy density and cycle stability
2Manufacturing precision
If graphite particles with certain aspect ratio are used to suppress non-uniform expansion, then manufacturing precision is improved, but device complexity increases due to specific electrolyte composition requirements
Solution Approach 1:
The invention specifies precise parameter ranges for both graphite particle aspect ratio (1 to 5) and imide salt content in the electrolyte. By controlling these parameters within defined ranges, the invention achieves uniform expansion behavior while managing the complexity of electrolyte composition through systematic specification rather than trial-and-error approaches
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 combination enhances the capacity retention rate after charge-discharge cycles by reducing non-uniform expansion and contraction of the negative active material, improving the overall performance of the energy storage device.
Implementation Method 1
the nonaqueous electrolyte contains an imide salt containing phosphorus or sulfur... forming a protective film on the surface of the negative active material
Data Source
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AI summary
One aspect of the present invention is an energy storage device including: a negative electrode containing a negative active material; a positive electrode containing a positive active material; and a nonaqueous electrolyte. The negative active material contains solid graphite particles with an aspect ratio of 1 to 5 as a main component, and the nonaqueous electrolyte contains an imide salt containing phosphorus or sulfur.