Dual-Layer Li-Ion Anode with Silicon Oxide for Fast-Charge Stability
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Solution Overview
Problem
Lithium-ion secondary batteries face degradation during quick charging due to over-voltage and lithium metal deposition on the negative electrode, leading to reduced lifespan, and existing materials like graphite and silicon have limitations in capacity and volume change during charge/discharge.
Innovation Solution
A negative electrode with a dual-layer structure, where the lower layer is primarily graphite and the upper layer consists of graphite and silicon oxide with specific sphericity and a linear conductive material, enhancing lithium ion diffusion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If charging is performed at high current density for quick charging, then charging speed is improved, but over-voltage is generated on the negative electrode surface causing lithium metal deposition and electrolyte decomposition which accelerates battery degradation
Solution Approach 1:
The negative electrode uses natural graphite particles with preserved spherical shape and specific size distribution (D50: 15-25 μm) to create non-uniform current distribution that prevents localized over-voltage. The spherical shape and size control the local electrochemical reaction characteristics, distributing lithium ion insertion more evenly across the electrode surface during fast charging.
Solution Approach 2:
The invention changes the physical parameters of graphite particles (sphericity, size distribution, crystallinity) to optimize electrochemical performance. By controlling particle size (D50: 15-25 μm) and maintaining spherical shape, the electrode achieves better lithium ion diffusion kinetics and lower resistance, enabling fast charging without excessive over-voltage generation.
2Quantity of substance
If silicon-based materials are used to increase capacity, then battery capacity is improved, but large volume change occurs during charge/discharge which degrades electrode structure
Solution Approach 1:
The invention uses natural graphite with optimized physical characteristics instead of silicon-based materials. While graphite has lower theoretical capacity than silicon, its dimensional stability during charge/discharge cycles ensures long-term electrode integrity. The focus shifts from maximizing immediate capacity to ensuring sustained performance over the battery lifecycle.
3Quantity of substance
If natural graphite is used as negative electrode material, then capacity is provided, but the graphite is deteriorated with ease during charge/discharge cycles
Solution Approach 1:
The invention optimizes specific parameters of natural graphite (particle size D50: 15-25 μm, spherical shape, crystallinity) to enhance cycle stability. These parameter changes reduce mechanical stress during lithium insertion/extraction and minimize electrode deterioration, allowing the use of natural graphite while maintaining long-term reliability.
4Ease of manufacture
If graphite-based materials are used for the negative electrode, then the battery can be manufactured with current technology, but the capacity is limited and deterioration occurs during charge/discharge
Solution Approach 1:
The invention enhances conventional graphite materials by optimizing physical parameters (particle size, sphericity, crystallinity) rather than changing the fundamental material chemistry. This approach maintains compatibility with existing manufacturing processes while achieving improved capacity and cycle stability through careful control of graphite particle characteristics.
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 dual-layer structure improves the battery's life characteristics and enables quick charging without significant degradation, offering a balance between capacity and volume stability.
Implementation Method 1
to provide a high diffusion rate of lithium ions in the active material
Implementation Method 2
to have high reversibility of reaction with lithium ions
Data Source
AI summary
Disclosed is a negative electrode for a lithium-ion secondary battery. The negative electrode includes a negative electrode active material layer, which includes a lower layer portion facing the surface of a current collector and an upper layer portion disposed on the top of the lower layer portion, wherein the upper layer portion includes graphite and silicon oxide as negative electrode active materials, the silicon oxide has a sphericity of 0.4-0.8, and the negative electrode active material layer includes a linear conductive material.