Carbon-Nanofiber Graphite Anode for Fast-Charging Battery Life
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Solution Overview
Problem
Natural graphite-based negative electrodes in secondary batteries face issues with rapid charging performance and lifespan due to internal voids, stress generation, and excessive side reactions with electrolytes, leading to degraded high-temperature storage and cycle performance.
Innovation Solution
A negative electrode active material with a core of natural graphite and an amorphous carbon layer, coated with carbon nanofibers, is used, optimizing particle size and surface functional groups to enhance lithium ion mobility and reduce internal pore volume, thereby improving battery lifespan and rapid charging capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural graphite is used as negative electrode active material, then battery capacity is increased, but rapid charging performance is deteriorated due to internal voids causing stress and lithium ion diffusion resistance
Solution Approach 1:
The patent uses a composite structure where natural graphite particles are coated with amorphous carbon material. This composite approach combines the high capacity advantage of natural graphite with the smooth surface and low resistance properties of amorphous carbon, resolving the contradiction between capacity and rapid charging performance
Solution Approach 2:
The patent controls the oxygen content of the amorphous carbon coating within a specific range (1.0-5.0 wt%) to optimize both capacity retention and lithium ion diffusion. By adjusting the chemical composition parameters of the coating layer, the material achieves both high capacity and rapid charging capabilities
2Quantity of substance
If natural graphite with internal voids is used, then battery capacity is increased, but side reaction with electrolyte is excessively generated causing gas generation and degraded lifespan
Solution Approach 1:
The amorphous carbon coating layer acts as an intermediary between the natural graphite and the electrolyte. This intermediate layer prevents direct contact and excessive side reactions between the graphite and electrolyte, reducing gas generation and improving battery lifespan while preserving the high capacity benefits
Solution Approach 2:
The patent specifically controls the oxygen content parameter of the amorphous carbon coating to be within 1.0-5.0 wt%. This parameter optimization creates a coating that is sufficiently reactive to prevent electrolyte decomposition but stable enough to maintain structural integrity, thereby extending battery lifespan
3Ease of manufacture
If natural graphite is used without treatment, then manufacturing simplicity is maintained, but lithium ion diffusion resistance is increased during charging and discharging
Solution Approach 1:
The amorphous carbon coating serves as a mediator that facilitates lithium ion diffusion. The coating's layered structure and controlled oxygen content create low-resistance pathways for lithium ions to move in and out of the graphite particles, significantly improving diffusion rate while maintaining manufacturing simplicity
Solution Approach 2:
By controlling the oxygen content parameter of the amorphous carbon coating within 1.0-5.0 wt%, the patent optimizes the coating's conductivity and ion transport properties. This parameter control enables rapid lithium ion diffusion without requiring complex manufacturing processes
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 solution effectively suppresses electrolyte side reactions, reduces volume expansion, and enhances lithium ion mobility, resulting in improved battery lifespan and rapid charging performance.
Implementation Method 1
the negative electrode active material comprises 1,500 ppm wt % to 2,000 ppm wt % of oxygen, 200 ppm wt % to 300 ppm wt % of nitrogen, and 200 ppm wt % to 300 ppm wt % of hydrogen as measured by an ONH analysis method
Implementation Method 2
improving the rapid charging performance of the battery by increasing the mobility of lithium ions
Data Source
AI summary
A negative electrode including a negative electrode active material layer including a negative electrode active material, wherein the negative electrode active material includes a core and a coating layer disposed on the core. The core includes natural graphite and an amorphous carbon layer on the natural graphite, wherein the natural graphite has an average particle diameter, D50, of 10 μm to 14 μm.ONH The negative electrode active material includes 1,500 ppm wt % to 2,000 ppm wt % of oxygen, 200 ppm wt % to 300 ppm wt % of nitrogen, and 200 ppm wt % to 300 ppm wt % of hydrogen as measured by an ONH analysis, and the coating layer includes carbon nanofibers.