Layered Battery Electrode Structure for Fast Charge and High Capacity
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Solution Overview
Problem
Current methods for fabricating lithium-ion secondary batteries do not adequately achieve high capacity density, rapid charging, and rapid discharging while ensuring safety and reliability, particularly due to insufficient electron and lithium-ion conductive paths in the electrodes.
Innovation Solution
The battery design incorporates a layered structure with distinct active material layers of varying particle diameters and sphericity, where the first layer has a smaller particle diameter than the second layer, and both contain conductive materials and solid electrolytes in specific proportions to enhance electron and lithium-ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single-layer electrode structure is used, then the device complexity is low, but the capacity density and charge-discharge performance are insufficient
Solution Approach 1:
The electrode is divided into multiple layers (first layer and second layer) with different active material particle sizes. The first layer contains smaller particles for rapid charge-discharge, while the second layer contains larger particles for high capacity density. This segmentation allows each layer to specialize in different functions, resolving the contradiction between performance and complexity.
Solution Approach 2:
Different regions of the electrode are assigned different properties: the first layer near the current collector has small particles for electron conduction, while the second layer has larger particles for lithium-ion storage. This local differentiation optimizes both capacity density and charge-discharge performance without requiring complex overall structure.
2Reliability
If conventional slurry coating method is used, then the manufacturing process is simple, but the electron and lithium-ion conductive paths are insufficient
Solution Approach 1:
Conductive materials are pre-mixed with active materials in specific proportions before coating. This preliminary preparation ensures that conductive paths are established during the manufacturing process itself, rather than requiring additional post-processing steps, thus improving reliability without significantly complicating fabrication.
Solution Approach 2:
The electrode uses composite materials combining active materials with conductive materials in specific ratios. This composite approach ensures both electron and lithium-ion conductive paths are built into the electrode structure during manufacturing, improving reliability while maintaining ease of manufacture through a single coating process.
3Speed
If rapid charging is implemented, then the charging speed increases, but the safety and reliability may be compromised
Solution Approach 1:
The invention changes the particle size parameter of active materials in different layers. The first layer uses smaller particles (5-10 μm) that enable rapid ion transport for fast charging, while the second layer uses larger particles (10-20 μm) that maintain structural stability for safety. This parameter differentiation allows rapid charging without compromising reliability.
Data Source
AI summary
Electrodes and a secondary battery having high capacity density and being excellent in terms of rapid charging and rapid discharging are provided. The battery includes a positive electrode and a negative electrode. The positive electrode includes a current collector, a first layer overlapping with the current collector, and a second layer overlapping with the first layer. The first layer contains a first active material with a first particle diameter and the second layer contains a second active material with a second particle diameter. The first particle diameter is smaller than the second particle diameter. It is preferable that the second active material include a surface portion and an inner portion, the surface portion be a region within a depth of 10 nm or less from a surface of the second active material to the inner portion, and that the surface portion and the inner portion be topotaxy.