Cathode Particle Morphology for Low-Temperature Li-Ion Rate Performance
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Solution Overview
Problem
Existing lithium-ion battery positive electrode active materials require optimization to enhance rate performance, particularly at low temperatures, due to limitations in transmission efficiency and stability of the crystal structure during high-rate cycling.
Innovation Solution
The use of a positive electrode material layer with specific particle size and shape distributions, where the average ratio of minimum to maximum inscribed circle radii (Rc/Ri) ranges from 1 to 3, and a controlled distribution of first and second particles, along with the inclusion of metal elements and optimized electrolyte compositions, such as linear and cyclic carbonates, to improve lithium ion transmission and reduce interface side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional positive electrode active materials are used, then the battery can operate normally, but the rate performance at low temperature is poor due to low lithium ion transmission efficiency
Solution Approach 1:
The patent changes the geometric parameters of positive electrode active material particles by controlling the Rc/Ri ratio within 1-3. This parameter optimization improves lithium ion transmission efficiency by creating favorable diffusion paths while maintaining structural stability during high-rate cycling, thereby enhancing rate performance at low temperatures without sacrificing reliability
Solution Approach 2:
The patent employs composite positive electrode active materials with specific particle morphology characteristics (Rc/Ri ratio control) to combine the advantages of high capacity with improved ion transmission. The composite structure enables better kinetic performance for lithium ion intercalation and deintercalation, resolving the contradiction between transmission efficiency and low-temperature rate performance
2Speed
If the positive electrode active material particle size is reduced to improve transmission efficiency, then lithium ion transmission improves, but the crystal structure stability during high rate cycling deteriorates
Solution Approach 1:
The patent optimizes the geometric parameters of positive electrode active material particles by controlling the Rc/Ri ratio within 1-3. This parameter control allows the material to achieve both high lithium ion transmission efficiency and stable crystal structure during high-rate cycling, resolving the contradiction between transmission speed and structural stability
Solution Approach 2:
The patent utilizes the geometric characteristics of particles by controlling the ratio of minimum circumscribed circle radius to maximum inscribed circle radius. This approach leverages the curvature and shape factors to optimize both ion transmission paths and structural integrity, achieving improved transmission efficiency while maintaining crystal structure stability
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
This configuration enhances the transmission efficiency of lithium ions, stabilizes the crystal structure, and significantly improves the rate and cycling performance of lithium-ion batteries at both room temperature and low temperatures.
Implementation Method 1
effectively improves kinetic performance of intercalation and deintercalation of lithium ions of the positive electrode active material
Implementation Method 2
transformation efficiency of lithium ions during charging and discharging can be effectively increased
Data Source
AI summary
An electrochemical apparatus includes a positive electrode plate, where the positive electrode plate includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, and in a cross-sectional scanning electron microscope image of the positive electrode material layer, a minimum circumscribed circle radius of the profile of a positive electrode active material particle with an area greater than 5 μm2 is Rc, and a maximum inscribed circle radius of the profile of the positive electrode active material particle with an area greater than 5 μm2 is Ri, satisfying 1<average value of Rc/Ri≤3. The positive electrode active material in the positive electrode material layer satisfies 1<average value of Rc/Ri≤3.