High-Ni Cathode Interface Coating for Cycle Stability
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Solution Overview
Problem
Lithium-transition metal composite oxides with high Ni content experience capacity reduction due to unstable surface layers, leading to material degradation and reduced cycle characteristics in non-aqueous electrolyte secondary batteries.
Innovation Solution
A positive electrode active material comprising lithium-transition metal composite oxide with a layered structure and high Ni content, where a compound represented by the formula AxByOz (with A being Ca or Sr and B being W, Mo, Ti, Si, Nb, or Zr) is adhered to the interfaces between primary particles within the secondary particles, enhancing surface protection and cycle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high Ni content is used in lithium-transition metal composite oxide to increase capacity, then the battery capacity is improved, but the surface layer becomes unstable and erodes during charging and discharging, leading to capacity reduction
Solution Approach 1:
The patent introduces an intermediary substance (coating layer or surface modification agent) that mediates between the high-Ni active material and the electrolyte. This intermediary protects the unstable surface layer while allowing ionic transport, thereby maintaining high capacity without surface erosion. The coating acts as a buffer that prevents direct contact between the reactive Ni-rich surface and the electrolyte, solving the stability problem while preserving capacity.
Solution Approach 2:
The patent creates a composite structure by combining high-Ni lithium-transition metal composite oxide with stabilizing materials (such as ceramic coatings or surface-modified layers). This composite approach allows the core high-Ni material to provide capacity while the outer stabilizing layer provides surface protection and structural integrity during cycling, thus resolving the contradiction between capacity and stability.
2Use of energy by moving object
If high Ni content is used to achieve high capacity, then energy density is improved, but material degradation occurs due to surface erosion, reducing cycle characteristics
Solution Approach 1:
The patent applies beforehand cushioning by pre-coating or pre-modifying the surface of the high-Ni active material before battery assembly. This protective layer is applied in advance to cushion against the mechanical and chemical stresses that will occur during subsequent charging and discharging cycles, preventing surface erosion and maintaining structural integrity throughout the battery's operational life, thus preserving both energy density and cycle characteristics.
Solution Approach 2:
The patent employs parameter changes by modifying surface properties (such as surface area, porosity, or chemical composition) through coating or surface treatment. These parameter changes create a surface layer with different properties than the bulk material, providing enhanced stability and resistance to erosion while maintaining the high-capacity characteristics of the underlying high-Ni composite oxide, thereby improving cycle life without sacrificing energy density.
Data Source
AI summary
A positive electrode active material for non-aqueous electrolyte secondary batteries according to an example embodiment of the present invention comprises a lithium transition metal composite oxide having a layered structure and containing not less than 75 mol % of Ni with respect to the total molar quantity of elements excluding Li and O. The lithium transition metal composite oxide is of secondary particles obtained by aggregation of primary particles. A compound represented by the general formula AxByOz (where 1≤x≤2, 1≤y≤5, 4≤z≤9, A is at least one element selected from among Ca and Sr, and B is at least one element selected from among W, Mo, Ti, Si, Nb, and Zr) is adhered at at least the interface between primary particles inside the secondary particles.