Lithium-ion Battery Negative Electrode Graphite Structure Optimization
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Solution Overview
Problem
Lithium-ion secondary batteries face severe capacity deterioration during charging/discharging cycles when using constant-voltage charging, and they struggle to achieve high volume energy density while maintaining rapid charging capabilities.
Innovation Solution
The battery design incorporates a negative electrode active material with a graphite structure, supported at 2.0 to 4.0 mg/cm2 on a collector, and a positive electrode active material supported at 4.0 to 7.0 mg/cm2, with a specific X-ray diffraction peak ratio, to facilitate efficient lithium ion intercalation and prevent capacity degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If constant-voltage charging is performed to simplify charger circuits and reduce cost, then charging efficiency is improved, but a very large charging current flows at the initial stage causing negative electrode active material to fail to completely intercalate with lithium ions, leading to dendrite deposition and severe capacitance deterioration
Solution Approach 1:
The patent changes the physical-chemical parameters of the negative electrode active material by controlling the graphite crystal structure (specifically the P101/P100 peak intensity ratio in XRD patterns) and the supported amount of carbon material (2.0 to 4.0 mg/cm²). These parameter changes enable the material to handle large charging currents during constant-voltage charging without causing incomplete intercalation or dendrite deposition, thus resolving the contradiction between simplified charging and battery reliability.
2Reliability
If the supported amount of negative electrode active material is reduced to prevent capacity deterioration during constant-voltage charging, then capacitance stability is improved, but volume energy density decreases
Solution Approach 1:
The patent optimizes the supported amount of carbon material to a specific range (2.0 to 4.0 mg/cm²) and controls the graphite crystal structure (P101/P100 ratio of 2.0 to 2.8). This parameter optimization allows sufficient carbon material to be present for high volume energy density while the improved intercalation characteristics prevent capacity deterioration during constant-voltage charging, resolving the contradiction between capacitance stability and energy density.
3Speed
If constant-current charging is used to achieve rapid charging, then charging speed is improved, but charging efficiency deteriorates under IR drop and polarization when charging voltage approaches full-charge voltage, resulting in short charging amount
Solution Approach 1:
The patent changes the parameters of the negative electrode active material (graphite structure with controlled P101/P100 ratio and optimized supported amount) to improve lithium ion intercalation efficiency. This enables the battery to accept higher charging currents even at higher voltages without severe polarization effects, allowing constant-current rapid charging to maintain both high charging speed and high charging amount that would otherwise be lost to efficiency deterioration.
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 reduces capacity deterioration and achieves sufficient volume energy density, enabling rapid charging while maintaining battery performance over cycles.
Implementation Method 1
there may occur a problem of a negative electrode active material failing to completely intercalate with lithium ions
Data Source
AI summary
A lithium-ion secondary battery device comprises a positive electrode collector having a surface formed with a positive electrode active material layer containing a positive electrode active material; a negative electrode collector having a surface formed with a negative electrode active material layer containing a negative electrode active material; an electrically insulating porous separator; and an electrolyte containing a lithium salt and being in contact with the positive electrode active material layer, negative electrode active material layer, and separator. The negative electrode active material is a carbon material having a graphite structure. The amount of the carbon material supported by the negative electrode active material layer is 2.0 to 4.0 mg/cm2. The graphite structure in an X-ray diffraction pattern of the carbon material exhibits a peak intensity P101 of (101) plane and a peak intensity P100 of (100) plane having a ratio (P101/P100) of 2.0 to 2.8 therebetween.