Layered-Olivine Cathode Structure for High-Voltage Li-Ion 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 active material comprising a combination of olivine-structured and layered-structured lithium compounds, with specific chemical formulations and particle sizes, is used to enhance energy density and voltage while improving electrode stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single positive electrode active material is used, then the electrode structure is simple, but the energy density and average voltage cannot be simultaneously optimized
Solution Approach 1:
The patent combines two different positive electrode active materials (olivine-structured LiMnFePO4 and layered LiNiCoMnO2) into a single electrode structure. This merging allows the electrode to simultaneously achieve high energy density from the layered material and high average voltage from the olivine material, resolving the contradiction between structural simplicity and energy performance optimization.
Solution Approach 2:
The patent uses a composite material system consisting of olivine-structured LiMnFePO4 and layered LiNiCoMnO2 particles in specific size ratios. This composite approach enables the electrode to achieve both high energy density and high average voltage by leveraging the complementary properties of the two materials while maintaining a relatively simple two-layer electrode structure.
2Use of energy by moving object
If high-nickel layered material is used to increase energy density, then the energy density improves, but the electrode stability and lifetime deteriorate
Solution Approach 1:
The patent applies local quality by controlling the particle size of different materials in different regions of the electrode. The layered LiNiCoMnO2 particles are made smaller (average diameter 3-6 μm) to improve stability, while the olivine LiMnFePO4 particles are larger (average diameter 6-12 μm). This local size optimization allows high energy density from the nickel-based material while maintaining electrode stability through controlled particle dimensions.
Solution Approach 2:
The composite material system combines high-nickel layered LiNiCoMnO2 (providing high energy density) with olivine-structured LiMnFePO4 (providing structural stability). The synergistic combination allows the electrode to achieve high energy density while the olivine component contributes to overall electrode stability and lifetime, resolving the contradiction between energy density and reliability.
3Power
If olivine-structured LiMnFePO4 with high average voltage is used, then the average voltage improves, but the energy density decreases
Solution Approach 1:
The patent merges olivine-structured LiMnFePO4 (high average voltage material) with layered LiNiCoMnO2 (high capacity material) in a composite electrode. This combination allows the electrode to achieve high average voltage from the olivine component while simultaneously achieving high energy density from the layered component, resolving the contradiction between voltage and energy density.
Solution Approach 2:
The patent optimizes the particle size parameters of both materials to balance voltage and energy density. By controlling the layered LiNiCoMnO2 particles to be smaller (3-6 μm) and olivine LiMnFePO4 particles to be larger (6-12 μm), the electrode achieves both high average voltage and high energy density through parameter optimization.
4Reliability
If particle size is reduced to improve conductivity, then the conductivity improves, but the manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by assigning different particle size ranges to different materials based on their specific functions. The layered LiNiCoMnO2 particles are controlled to be smaller (3-6 μm) to maximize conductivity and electrochemical activity, while the olivine LiMnFePO4 particles are larger (6-12 μm) for structural stability. This differentiated size control optimizes conductivity without requiring complex manufacturing processes.
Solution Approach 2:
The patent uses parameter changes by establishing specific particle size ranges for each material component. By controlling the particle size parameters within defined ranges rather than requiring precise dimensional control, the patent improves conductivity while keeping the manufacturing process relatively simple and scalable.
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 proposed electrode material achieves high energy density, high average voltage, and extended battery life, addressing the limitations of existing technologies in rechargeable lithium batteries.
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
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 is a single particle, the third particle is in the form of a secondary particle in which a plurality of third primary particles are aggregated, and the second particle has a greater average particle diameter than each of the first particle and the third particle. Also disclosed is a rechargeable lithium battery including the same.