High-Ni Cathode Material Microstructure for Crack-Resistant Cycling
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Solution Overview
Problem
Conventional high-Ni positive electrode active materials in lithium secondary batteries suffer from structural degradation, cracks, and increased resistance due to volume changes during charge and discharge, limiting capacity retention and conductivity.
Innovation Solution
A nickel-based lithium composite transition metal oxide with optimized crystallite size and reduced strain is achieved by controlling sintering conditions, ensuring 80 nm ≤ crystallite size FWHM ≤ 150 nm and Δsize (crystallite size IB - crystallite size FWHM) ≤ 20, minimizing cracks and enhancing structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content is increased to improve capacity characteristics, then capacity increases, but surface instability and structural degradation occur during charge and discharge
Solution Approach 1:
The patent optimizes the nickel content parameter within a specific range (0.6 ≤ 1-(x+y+z) ≤ 0.8) rather than maximizing it, and simultaneously controls crystallite size parameters (80-150 nm) and strain (Δsize ≤ 20) to achieve a balance between capacity and structural stability. This parameter optimization approach resolves the contradiction by finding the optimal operating point rather than extreme values.
Solution Approach 2:
The patent uses composite transition metal oxides with multiple elements (Ni, Co, Mn, Al, and other dopants) where each element contributes different properties. The composite structure allows nickel to provide high capacity while other elements stabilize the crystal structure and reduce strain, resolving the contradiction between nickel content and surface stability.
2Quantity of substance
If nickel content is increased to achieve higher capacity, then capacity increases, but volume changes in unit cell cause cracks during charge and discharge
Solution Approach 1:
The patent严格控制 crystallite size (80-150 nm) and strain (Δsize ≤ 20) parameters to minimize volume changes during charge and discharge cycles. By optimizing these microstructural parameters alongside composition, the material maintains structural integrity while achieving high nickel content and capacity.
Solution Approach 2:
The patent introduces dopant elements at specific lattice positions to locally strengthen the crystal structure and accommodate volume changes. The non-uniform distribution of different elements creates local regions with enhanced structural stability that prevent crack formation while maintaining overall high nickel content.
3Reliability
If coating or doping is applied to prevent cracks, then structural stability improves, but additional cost is incurred and uniform coating/doping is difficult to achieve
Solution Approach 1:
The patent combines composition optimization and microstructure control into a single integrated material design approach. By simultaneously optimizing nickel content, dopant composition, crystallite size, and strain parameters, the patent achieves structural stability without requiring separate coating or doping process steps, thereby reducing process complexity while maintaining reliability.
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 effectively minimizes cracks, increases capacity retention, and suppresses resistance increase in the positive electrode active material, improving the battery's performance and cycle life.
Implementation Method 1
electrical energy is produced by oxidation and reduction reactions when the lithium ions are intercalated/deintercalated into/from the positive electrode and the negative electrode
Implementation Method 2
A nickel-based lithium composite transition metal oxide with optimized crystallite size and reduced strain is achieved by controlling sintering conditions
Data Source
Figure 1
AI summary
The present invention provides a positive electrode active material for a secondary battery which includes a nickel-based lithium composite transition metal oxide including nickel (Ni), wherein the lithium composite transition metal oxide satisfies Equation 1 and Equation 2 below. 80nm≤crystallitesizeFWHM≤150nm ΔsizecrystallitesizeIB−crystallitesizeFWHM≤20 wherein, in Equation 1 and Equation 2, crystallite sizeFWHM is a crystallite size obtained by calculating from X-ray diffraction (XRD) data using a full width at half maximum (FWHM) method, and crystallite sizeIB is a crystallite size obtained by calculating from XRD data using an integral breadth (IB) method.