Nickel-Rich Cathode Crystallite Control for Crack-Resistant Cycling
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Solution Overview
Problem
Nickel-based lithium composite transition metal oxides with high nickel content suffer from structural degradation and increased resistance due to volume changes during charge and discharge, leading to cracks and reduced capacity retention in lithium secondary batteries.
Innovation Solution
Optimizing the crystallite size and reducing strain in the positive electrode active material by controlling the sintering conditions to satisfy specific size and strain equations, ensuring crystallite sizes between 80 nm and 150 nm and a strain difference of 20 nm or less, thereby minimizing cracks and enhancing cycle capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content is increased to improve capacity characteristics, then capacity increases, but surface stability deteriorates and structural degradation occurs during charge and discharge
Solution Approach 1:
The patent optimizes the crystallite size parameter to a specific range (80-150 nm) to resolve the contradiction between high nickel content and surface stability. By controlling the crystallite size within this range, the material maintains both high capacity from high nickel content and improved surface stability, preventing structural degradation during charge-discharge cycles.
2Quantity of substance
If high nickel content is increased to achieve higher capacity, then capacity increases, but volume changes in unit cell increase causing cracks
Solution Approach 1:
The patent controls the crystallite size parameter within 80-150 nm to minimize volume changes in the unit cell during lithium insertion/extraction. This parameter optimization reduces the expansion-contraction stress that causes cracks, thereby maintaining structural integrity while achieving high capacity through high nickel content.
3Reliability
If coating or doping is applied to prevent cracks, then crack resistance improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and addresses the root cause of cracking by optimizing the intrinsic crystallite size parameter of the active material itself, rather than adding external coating or doping layers. This approach prevents cracks through proper material design while avoiding the additional complexity and cost of post-synthesis modification processes.
4Reliability
If crystallite size is optimized to minimize cracks, then capacity retention increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes a specific crystallite size range (80-150 nm) that balances capacity retention with manufacturability. This parameter window is wide enough to allow reasonable manufacturing tolerance while still providing the benefits of minimized volume change and improved capacity retention, avoiding overly stringent precision requirements.
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 approach effectively minimizes cracks, increases capacity retention, and suppresses resistance increase rates in nickel-based lithium composite transition metal oxide positive electrodes, improving the performance and longevity of lithium secondary batteries.
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
active materials capable of intercalating and deintercalating lithium ions
Data Source
AI summary
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 below80 nm≤crystallite sizeFWHM≤150 nm [Equation 1]Δsize(|crystallite sizeIB−crystallite sizeFWHM|)≤20 [Equation 2]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.