Solid Graphite Negative Electrode for Energy Storage
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Solution Overview
Problem
The use of graphite as a negative active material in energy storage devices leads to a significant decrease in capacity retention ratio after high-rate charge-discharge cycles due to inhomogeneous current distribution and expansion, which affects the negative electrode utilization factor.
Innovation Solution
An energy storage device with a negative electrode utilizing solid graphite particles as the main component, having an aspect ratio of 1 to 5 and an average particle size of 5 μm or less, to maintain a high negative electrode utilization factor of 0.65 or more, preventing inhomogeneous current distribution and expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite is used as the negative active material to increase capacity and energy density, then the negative electrode utilization factor increases, but the capacity retention ratio after high-rate charge-discharge cycles significantly decreases
Solution Approach 1:
The invention changes the physical parameters of graphite particles by controlling the aspect ratio to be 1 or more and 5 or less, and controlling the average particle size to be 10 μm or less. These parameter changes optimize the balance between achieving high negative electrode utilization factor (0.65 or more) and maintaining capacity retention ratio after high-rate charge-discharge cycles
Solution Approach 2:
The invention applies local quality control by specifying that solid graphite particles with particular aspect ratios and sizes be used as the main component of the negative active material. This creates localized optimal conditions within the electrode structure that simultaneously achieve high utilization factor and good capacity retention
2Use of energy by moving object
If the negative electrode utilization factor is increased to improve energy density, then more charge is stored per mass of negative active material, but inhomogeneous current distribution and expansion occur during high-rate cycling
Solution Approach 1:
The invention changes the particle morphology parameters of graphite by limiting the aspect ratio to 1-5 and average particle size to 10 μm or less. These parameter changes ensure uniform current distribution during high-rate cycling while maintaining high negative electrode utilization factor (0.65 or more), thereby achieving high energy density without compromising compositional stability
Solution Approach 2:
The invention uses solid graphite particles with specific aspect ratios and sizes as the main component (but not necessarily 100%) of the negative active material. This partial application of optimized graphite particles achieves sufficient energy density improvement while preventing the harmful effects of inhomogeneous current distribution
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 decrease in capacity retention ratio after high-rate charge-discharge cycles, maintaining high energy density and utilization factor.
Implementation Method 1
The nonaqueous electrolyte secondary battery is configured to be charged and discharged by transferring ions between both the electrodes
Data Source
AI summary
An energy storage device according to an aspect of the present invention includes a negative electrode and a positive electrode, the negative electrode includes a negative substrate and a negative active material layer directly or indirectly layered on the negative substrate, the negative active material layer contains a negative active material, the negative active material contains solid graphite particles as a main component, the aspect ratio of the solid graphite particles is 1 or more and 5 or less, and a negative electrode utilization factor that is the proportion of the amount of charge per mass of the negative active material in a full charge state to a theoretical capacity per mass of graphite is 0.65 or more.