Layered Positive Electrode Structure for High-Energy Lithium Batteries
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density, high average voltage, and excellent lifetime while maintaining economic viability.
Innovation Solution
A positive electrode for rechargeable lithium batteries is designed with a layered structure comprising a first particle with an olivine structure and a second particle with a layered structure, where the second particle has a greater average particle diameter, and a functional additive with a lower weight ratio in the second layer, enhancing the battery's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-layer positive electrode active material layer is used, then the manufacturing process is simple, but the energy density and lifetime performance are insufficient
Solution Approach 1:
The positive electrode active material layer is divided into two distinct layers: a first layer containing olivine-structured particles (LiMn1-x-yFexB1yPO4) and a second layer containing layered-structured particles (LiNi0.8Co0.1Mn0.1O2). This segmentation allows each layer to contribute different functional properties - the olivine layer provides structural stability and safety while the layered layer provides high capacity, thereby achieving high energy density and excellent lifetime without requiring complex multi-component formulations in a single layer.
Solution Approach 2:
The patent employs a composite electrode structure combining two different crystal structures (olivine and layered) in separate layers. The olivine-structured LiMn1-x-yFexB1yPO4 particles provide thermal stability and structural integrity, while the layered LiNi0.8Co0.1Mn0.1O2 particles provide high specific capacity. This composite approach enables the electrode to simultaneously achieve high energy density, long cycle life, and safety.
2Productivity
If high nickel content layered structure material is used, then the energy density is improved, but the structural stability and lifetime deteriorate
Solution Approach 1:
By separating the high-nickel layered material into a distinct second layer and placing it adjacent to (but not mixed with) the olivine-structured first layer, the patent isolates the high-capacity material from direct contact with the electrolyte and from mechanical stress during cycling. The olivine layer acts as a protective buffer that maintains overall structural stability while allowing the layered layer to deliver high energy density.
Solution Approach 2:
The patent creates a composite electrode where the olivine-structured LiMn1-x-yFexB1yPO4 (with inherent structural stability) is combined with layered LiNi0.8Co0.1Mn0.1O2 (with high capacity). The olivine phase serves as a structurally stable framework that compensates for the inherent instability of high-nickel layered materials, enabling the system to achieve both high energy density and long cycle life.
3Reliability
If olivine structure material is used, then the structural stability is improved, but the energy density and average voltage deteriorate
Solution Approach 1:
The patent divides the electrode into two layers with the olivine-structured material forming the first layer that provides structural stability and safety, while the layered-structured material forms the second layer that contributes high capacity. This segmentation allows the olivine layer to be optimized for stability (with appropriate thickness and composition) without compromising the overall energy density, as the layered layer compensates with high specific capacity.
Solution Approach 2:
The patent creates a composite electrode system where the olivine-structured LiMn1-x-yFexB1yPO4 particles are combined with layered LiNi0.8Co0.1Mn0.1O2 particles in a layered configuration. The olivine phase contributes structural stability, safety, and moderate capacity, while the layered phase contributes high specific capacity. The synergistic combination achieves energy density and average voltage that exceed those of pure olivine materials while maintaining excellent structural stability and long cycle life.
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 design achieves high energy density, high average voltage, and improved lifetime with economic efficiency by optimizing the electrode structure and additive composition.
Implementation Method 1
produce electrical energy from redox reactions that take place as lithium ions are intercalated into or deintercalated from the positive electrode and the negative electrode
Data Source
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AI summary
Provided are a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same, and for example, a positive electrode for a rechargeable lithium battery, 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 particle having an olivine structure, and a second particle having a layered structure, and the second positive electrode active material layer includes a third particle having an olivine structure. The first particle and the third particle are each in the form of a single particle, and the second particle has a greater average particle diameter than each of the first particle and the third particle.