Mixed Cathode Material for Uniform LFP-Ternary Electrode Coating
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Solution Overview
Problem
Lithium-ion batteries face issues with agglomeration and uneven distribution of mixed positive electrode materials, leading to unstable performance and poor electrochemical properties, particularly when combining lithium iron phosphate and ternary systems.
Innovation Solution
A mixed positive electrode material is developed, comprising secondary particles of lithium iron phosphate with controlled specific surface area, particle size distribution, and resistivity, which are uniformly distributed on the electrode plate to enhance miscibility and processing feasibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiCoO2 is used as the positive electrode material to achieve high output, then the battery capacity increases, but the material decomposes at high potentials leading to reduced stability and safety
Solution Approach 1:
The patent uses a core-shell composite structure where LiCoO2 core particles are coated with a Li-rich layered oxide shell. This composite structure allows the inner LiCoO2 to provide high capacity while the outer Li-rich shell prevents direct contact between LiCoO2 and electrolyte, preventing decomposition and improving stability. The composite material combines the advantages of both materials to resolve the contradiction between high capacity and stability.
Solution Approach 2:
The Li-rich layered oxide acts as an intermediary protective layer between LiCoO2 and the electrolyte. This intermediate shell prevents harmful direct interactions while allowing beneficial ionic transport, thus protecting the LiCoO2 core from decomposition at high potentials while maintaining electrochemical performance.
2Quantity of substance
If LiCoO2 is used as the positive electrode material to achieve high output, then the battery capacity increases, but the material reacts with electrolyte leading to gas generation and safety issues
Solution Approach 1:
The Li-rich layered oxide shell forms a protective composite structure that prevents direct reaction between LiCoO2 and electrolyte. This composite design eliminates the harmful gas-generating reactions while preserving the high capacity characteristics of LiCoO2.
Solution Approach 2:
The Li-rich layered oxide serves as an intermediary barrier that prevents harmful reactions between LiCoO2 and electrolyte. This intermediate layer blocks the direct contact that would otherwise lead to gas generation and safety issues, while still permitting necessary ionic transport for high capacity operation.
3Reliability
If Li-rich layered oxide is used as the positive electrode material to improve stability, then the material stability increases, but the initial charge capacity is lost
Solution Approach 1:
The electrode material is segmented into a core-shell structure where the LiCoO2 core provides high capacity and the Li-rich shell provides stability. This segmentation allows each component to perform its optimal function without compromising the other, resolving the contradiction between initial capacity and stability.
Solution Approach 2:
The composite structure combines LiCoO2 (high capacity) with Li-rich layered oxide (high stability) in a core-shell configuration. The inner core maximizes initial charge capacity while the outer shell ensures material stability, achieving both objectives simultaneously rather than sacrificing one for the other.
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 improves the electrochemical performance and energy density of lithium-ion batteries by preventing agglomeration, ensuring uniform distribution, and optimizing the electrode material's properties.
Implementation Method 1
the positive electrode active material particles have a core-shell structure, in which an inner core is made of LiCoO2 and an outer shell is made of Li-rich layered oxide that differs from the LiCoO2 in a composition ratio of Li to O
Implementation Method 2
When a LiCoO2 positive electrode is used, there is a high risk of causing active oxygen to be generated and a battery internal pressure to increase due to a reaction with an electrolyte
Implementation Method 3
the material has an initial charge capacity of 2.4 mAh or more per g and has excellent cycle characteristics
Data Source
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AI summary
This application provides a mixed positive electrode material, a positive electrode plate and a preparation method thereof, a battery, and an apparatus. The mixed positive electrode material of this application includes a mixed component consisting of a material of lithium iron phosphate chemical system and a material of ternary chemical system, where the material of lithium iron phosphate chemical system is secondary particles with an average specific surface area within 10 m2/g. In the mixed positive electrode material of this application, the introduction of lithium iron phosphate secondary particles having a low specific surface area improves ease of processing of the mixed positive electrode material, making a slurry less prone to agglomeration and the two materials highly miscible. When the positive electrode plate is prepared by using the mixed positive electrode material of this application, uniform distribution of the positive electrode material on the positive electrode plate can be effectively improved, which helps uniform distribution of electrode plate resistance, thereby improving electrochemical performance of batteries.