Dual-Particle Positive Electrode Material for Voltage-Stable Li Batteries
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density, high operating voltage, and high conductivity, as well as low-temperature performance.
Innovation Solution
A positive electrode active material comprising first and second particles with specific chemical compositions and particle diameters, along with a conductive material and binder, is used to enhance the performance of rechargeable lithium batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single-type positive electrode active material is used, then the electrode structure is simple, but the energy density and conductivity are insufficient
Solution Approach 1:
The patent uses a composite positive electrode active material consisting of LiFePO4 particles (first particles) and Li2MnO3 particles (second particles). This composite structure combines the advantages of both materials: LiFePO4 provides structural stability and safety, while Li2MnO3 contributes to high voltage and high capacity, thereby achieving high energy density without excessive structural complexity
Solution Approach 2:
The positive electrode active material is segmented into two distinct particle types with different functions and size ranges. The first particles (LiFePO4) have a diameter of 3-10 μm and provide stable lithium ion insertion/extraction, while the second particles (Li2MnO3) have a diameter of 1-3 μm and provide high voltage output. This segmentation allows each particle type to optimize its performance contribution
2Power
If high voltage materials are used to increase operating voltage, then the energy density improves, but the structural stability deteriorates
Solution Approach 1:
The patent creates a composite system where Li2MnO3 particles (providing high voltage of 4.0-4.3V vs. Li/Li+) are combined with LiFePO4 particles (providing structural stability). The LiFePO4 phase acts as a stable matrix that maintains structural integrity during cycling, while the Li2MnO3 phase contributes high voltage and capacity, resolving the contradiction between voltage and stability
Solution Approach 2:
Different regions of the positive electrode have different material compositions optimized for different functions. The Li2MnO3 particles are distributed within the LiFePO4 matrix, creating local high-voltage zones surrounded by stable LiFePO4 regions. This local quality differentiation allows high voltage operation without compromising overall structural stability
3Reliability
If particle size is reduced to improve conductivity, then the conductivity improves, but the energy density decreases
Solution Approach 1:
The patent segments the positive electrode active material into two particle size ranges: 3-10 μm for LiFePO4 particles and 1-3 μm for Li2MnO3 particles. This segmentation strategy allows smaller particles (improving conductivity) to be used for the high-voltage Li2MnO3 phase, while larger LiFePO4 particles maintain structural stability and contribute to energy density through their high volumetric capacity
Solution Approach 2:
The composite structure combines particles of different sizes and compositions, where the smaller Li2MnO3 particles (1-3 μm) provide high conductivity and voltage, while the larger LiFePO4 particles (3-10 μm) provide structural framework and volumetric energy density. The synergistic interaction between these differently sized particles resolves the conductivity-energy density contradiction
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 solution results in rechargeable lithium batteries with improved energy density, operating voltage, and low-temperature properties, while maintaining structural stability and conductivity.
Implementation Method 1
These batteries may produce electrical energy through oxidation and reduction reactions during the intercalation and deintercalation of lithium ions at the positive electrode and negative electrode
Data Source
AI summary
A positive electrode active material for a rechargeable battery, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode active material are provided. The positive electrode active material includes first particles including a compound of Chemical Formula 1 and having a first average particle diameter, and second particles including a compound of Chemical Formula 2 and having a second average particle diameter that is greater than the first average particle diameter. The content (e.g., amount) of the first particles is greater than the content (e.g., amount) of the second particles, and wherein the positive electrode active material includes manganese (Mn) and cobalt (Co), and a ratio of the Mn content (e.g., amount) to the Co content (e.g., amount) in the positive electrode active material is about 7:1 to about 12:1.