Layered Positive Electrode Materials for High-Density Li-Ion Batteries
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Solution Overview
Problem
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 olivine-based particle and a second spinel-based particle, each with specific elemental compositions and structures, enhancing energy density and voltage while maintaining durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-type 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 positive electrode is divided into two distinct layers: a first positive electrode active material layer containing olivine-based lithium compound particles, and a second positive electrode active material layer containing spinel-based lithium compound particles. This segmentation allows each layer to contribute different electrochemical properties, enabling simultaneous optimization of energy density and average voltage without excessive complexity.
Solution Approach 2:
The patent employs a composite structure combining two different lithium compound materials (olivine-based and spinel-based) with distinct crystal structures and electrochemical characteristics. This composite approach leverages the high capacity of olivine materials and the high voltage stability of spinel materials to achieve superior overall performance.
2Use of energy by moving object
If high-capacity materials are used to increase energy density, then the battery capacity improves, but the lifetime and stability deteriorate
Solution Approach 1:
Different regions of the positive electrode are assigned different material compositions tailored to specific functional requirements. The first layer uses olivine-based materials for high capacity, while the second layer uses spinel-based materials for structural stability and long-cycle life. This local differentiation of material properties resolves the contradiction between energy density and lifetime.
Solution Approach 2:
The dual-layer structure acts as a protective strategy where the spinel-based second layer provides structural stability and prevents degradation of the high-capacity olivine-based first layer during cycling, thereby cushioning against capacity fade and extending battery lifetime beforehand.
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 layered structure provides a positive electrode with high energy density, high average voltage, and improved lifetime, addressing the economic and performance demands of modern battery applications.
Implementation Method 1
The batteries produce electrical energy from redox reactions that take place as lithium ions are intercalated into the positive electrode and/or deintercalated from the negative electrode during the discharge process
Data Source
AI summary
A positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the positive electrode are provided. The positive electrode includes 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 active material layer includes a first particle represented by Formula 1 and having the form of a single particle, and a second particle represented by Formula 2. The second positive electrode active material layer includes a third particle represented by Formula 3 and having the form of a single particle. The first particle is present in a greater content (e.g., amount) than the second particle.