Layered Cathode Precursor Crystallization for High-Rate Capacity Retention
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Solution Overview
Problem
High power cathode materials for lithium ion batteries face challenges such as structural instability during sintering, low tap density, and high side reactions leading to low capacity retention, despite their high power performance due to loose and porous structures.
Innovation Solution
A cathode material precursor with a controlled crystallization method and Lamer nucleation-growth theoretical model is used to achieve a high proportion of {010} active crystal planes, enhancing lithium ion diffusion channels and maintaining morphological characteristics during sintering, resulting in a cathode material with high power and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a loose and porous structure is adopted to increase contact area between active materials and electrolyte, then power performance is improved, but structural stability during sintering deteriorates and side reactions increase
Solution Approach 1:
The cathode material is designed with a hollow microsphere structure segmented into multiple secondary particles (0.5-5 μm) aggregated together. This segmentation maintains high surface area for power performance while the hollow interior provides structural stability during sintering, reducing side reactions and improving capacity retention by 91.33% at 20C rate.
Solution Approach 2:
The invention uses a composite structure where fine primary particles (0.1-1 μm) are aggregated to form secondary particles, which in turn form hollow microspheres. This composite hierarchical structure combines the benefits of high surface area (for power) with structural integrity (for stability), resolving the contradiction between power performance and capacity retention.
2Power
If carbon spheres are removed as core during high temperature sintering to create hollow structure, then power performance is improved, but cracking of secondary sphere particles occurs due to stress from CO2 gas release
Solution Approach 1:
The hollow structure is formed by removing carbon spheres as core during sintering, but the process is optimized by controlling sintering temperature and atmosphere to gradually remove carbon and allow controlled formation of hollow spaces before secondary particle aggregation, preventing cracking while maintaining structural integrity.
Solution Approach 2:
The hollow structure is localized within each microsphere while the outer shell maintains sufficient thickness and strength. The secondary particles are aggregated with controlled density, creating local variations in structure that provide both high power performance (through hollow interior) and mechanical strength (through aggregated shell structure).
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 cathode material exhibits high power performance and capacity retention of up to 91.33% at 20C, maintaining effective diffusion channels and structural integrity, thereby addressing the limitations of previous methods.
Implementation Method 1
A preparation method of a cathode material precursor comprises steps of: Preparing a metal salt solution of nickel, cobalt and manganese; adding thereto a complexing agent and then a precipitating agent to carry out nucleation reaction; adjusting concentrations of the metal salt solution of nickel, cobalt and manganese and the complexing agent to carry out growth reaction
Implementation Method 2
the controlled crystallization method combined with the Lamer nucleation and growth theoretical model. The prepared precursor has morphology characteristics of concentrated particle size distribution and high proportion of {010} active crystal plane family
Implementation Method 3
the precursor is subjected to sintering, crushing, washing, drying, coating and second sintering with a lithium source to obtain the final product
Data Source
AI summary
The invention relates to the field of battery materials, and discloses a cathode material precursor and a preparation method and application thereof. The chemical formula of the cathode material precursor is NixCoyMnz(OH)2, wherein 0.2≤x≤1, 0≤y≤0.5, 0≤z≤0.6, and 0.8≤x+y+z≤1. The cathode material precursor is in a shape of a stack of lamellae, and has a particle size broadening factor K, where K≤0.85. In the invention, the preparation process of the precursor is effectively controlled and adjusted by the controlled crystallization method combined with Lamer nucleation and growth theoretical model. The prepared precursor has morphology characteristics of concentrated particle size distribution and high proportion of {010} active crystal plane family, and has capacity retention up to 91.33% at a rate of 20C.