Layered Positive Electrode Structure for Fast-Charging Lithium Batteries
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density, high capacity, and rapid charging characteristics while maintaining long lifecycle performance.
Innovation Solution
A positive electrode structure with a two-layer design, comprising a first layer of large secondary particles and a second layer of small single particles, each made of lithium transition metal composite oxides, enhances energy density and output characteristics through optimized particle size and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-layer positive electrode structure is used, then the device complexity is low, but the energy density and output characteristics cannot be simultaneously optimized
Solution Approach 1:
The positive electrode is divided into two distinct layers: a first positive electrode active material layer and a second positive electrode active material layer. Each layer contains different ratios of large-particle and small-particle active materials, allowing independent optimization of energy storage and output characteristics without requiring a single complex multi-component structure.
Solution Approach 2:
The patent introduces a vertical layering dimension to the electrode structure, stacking two functional layers with different particle size compositions. This dimensional approach allows simultaneous optimization of bulk energy density (first layer) and surface output characteristics (second layer) without increasing horizontal structural complexity.
2Productivity
If only large secondary particles are used in the positive electrode, then the energy density is high, but the rapid charging characteristics deteriorate
Solution Approach 1:
The patent applies different particle size compositions to different layers: the first layer uses a higher proportion of large secondary particles (70-95 wt%) for high energy density, while the second layer uses a higher proportion of small particles (50-80 wt%) for rapid charging. This local differentiation allows each layer to optimize for its specific function.
Solution Approach 2:
Each layer is composed of a composite mixture of large secondary particles and small single particles or smaller secondary particles. This composite approach within each layer, combined with the layered structure, enables the electrode to simultaneously achieve high energy density from large particles and rapid charging from small particles.
3Speed
If only small particles are used in the positive electrode, then the rapid charging characteristics are high, but the energy density decreases
Solution Approach 1:
The patent strategically places small particles predominantly in the second layer (50-80 wt% of small particles) to optimize for rapid charging at the electrode surface, while the first layer maintains a higher proportion of large particles (70-95 wt%) to maximize energy density in the bulk structure.
4Productivity
If a two-layer structure with different particle sizes is used, then both energy density and output characteristics are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for particle size distribution in each layer (first layer: 70-95 wt% large particles; second layer: 50-80 wt% small particles) and layer thickness ratios (1:0.5 to 0.5:1). These quantified parameters provide clear manufacturing targets that balance performance optimization with production feasibility.
Data Source
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AI summary
Disclosed are a positive electrode for a rechargeable lithium battery, the positive electrode including a current collector, a first positive electrode active material layer on the current collector, and a second positive electrode active material layer on the first positive electrode active material layer. The first positive electrode active material layer includes a first positive electrode active material including a lithium transition metal composite oxide as secondary particles formed by agglomeration of a plurality of primary particles, and a second positive electrode active material including a lithium transition metal composite oxide as single particles. The second positive electrode active material layer includes a third positive electrode active material including a lithium transition metal composite oxide as secondary particles formed by agglomeration of a plurality of primary particles, and a fourth positive electrode active material including a lithium transition metal composite oxide as secondary particles.