Lithium-Ion Cathode Material Crack Suppression via Crystallite Control
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Solution Overview
Problem
Existing cathode active materials for lithium-ion batteries suffer from crack generation during charge-discharge cycles, leading to increased internal resistance and capacity deterioration due to insufficient crystallite size and non-uniform incorporation of vanadium and boron, requiring multiple calcination steps and restricting production efficiency.
Innovation Solution
A cathode active material with a composition of LixNi1-yMyOα, where M is selected from Ti, Cr, Mn, Fe, Co, Cu, Al, Sn, Mg, and Zr, with a controlled crystallite size of 870 Å or more and a unit lattice volume of 101.70 Å3 or less, achieved by optimizing calcination conditions and composition, reducing crack generation and enhancing cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vanadium and/or boron are added to the cathode active material to improve cycle characteristics, then crack suppression is enhanced, but the material requires multiple calcination steps and cannot be incorporated into the crystal structure, reducing production efficiency
Solution Approach 1:
The patent applies preliminary action by pre-forming the lithium-transition metal composite oxide with controlled crystallite size and lattice distortion before adding vanadium and/or boron. This preliminary preparation ensures the base structure is optimized for crack suppression, allowing the subsequent addition of V/B elements to further enhance cycle characteristics without requiring multiple calcination steps.
Solution Approach 2:
The patent merges the functions of multiple additives (vanadium and boron) into a single composition formula LiXMYOZ-δ. By combining these elements in specific molar ratios ((V+B)/M=0.001 to 0.05), the patent achieves synergistic effects for crack suppression and cycle characteristic improvement while maintaining a single-phase compound structure that can be produced in one calcination step.
2Length of stationary object
If vanadium or boron is added in an amount exceeding a certain ratio to achieve sufficient crystallite size, then crystallite size increases, but the composition deviates from optimal stoichiometry and may affect material performance
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molar ratio of vanadium and boron to transition metal elements within the range (V+B)/M=0.001 to 0.05. This parameter optimization allows the crystallite size to reach 450 Å or more while maintaining the stability of the lithium-transition metal composite oxide composition and avoiding stoichiometric deviations that would affect material performance.
3Reliability
If the crystallite size is increased to reduce crack area, then crack suppression improves, but the production process becomes more complex and time-consuming
Solution Approach 1:
The patent applies parameter changes by controlling the crystallite size to be 450 Å or more through optimization of the composition formula and single-step calcination process. This parameter control achieves effective crack suppression (reduced crack area) while avoiding complex multi-step production processes, as the desired crystallite size is achieved directly through the optimized composition and one calcination step.
Data Source
AI summary
A cathode active material for lithium-ion battery is provided, which provides good battery characteristics such as cycle characteristics. The cathode active material for lithium-ion battery is expressed by the composition formula: LixNi1-yMyOα, wherein M is one or more selected from Ti, Cr, Mn, Fe, Co, Cu, Al, Sn, Mg and Zr; 0.9≦x≦1.2; 0<y≦0.5; and 2.0≦α≦2.2, wherein the crystallite size obtained by analyzing the XRD pattern is 870 Å or more and the unit lattice volume is 101.70 Å3 or less.