Hollow Cathode Active Material for Cycle Life and Rate Capability
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Solution Overview
Problem
Current positive electrode active materials in secondary batteries suffer from poor cycle performance and rate capability, despite advancements in materials like nickel-rich ternary materials, due to cation mixing and interface reactions leading to impedance increase.
Innovation Solution
A positive electrode active material with a hollow structure, characterized by an inner diameter of 0.3 μm-5 μm, and specific compositional and structural parameters, including Dv50/(d1+d2)≤4, porosity of 0-20%, and specific surface area of 0.4 m2/g-1.4 m2/g, is developed to stabilize the structure and enhance lithium-ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive electrode active materials are used, then the battery can achieve basic energy storage, but the cycle performance and rate capability are poor
Solution Approach 1:
The patent applies porous hollow spherical structures as the positive electrode active material framework. The hollow spherical morphology with controlled pore sizes (0.3-5 μm inner diameter) provides numerous three-dimensional pore passages that enlarge the contact area between the material and electrolytic solution, shorten lithium-ion migration distance, and reduce internal resistance. This porous structure simultaneously improves cycle performance by buffering volume changes and enhances rate capability by facilitating rapid ion transport.
Solution Approach 2:
The patent optimizes specific parameters of the hollow spherical structure including inner diameter (0.3-5 μm), outer wall thickness (3-10 μm), porosity (0-20%), and specific surface area (0.4-1.4 m²/g). By controlling these parameters within specific ranges, the material achieves optimal balance between structural stability for cycle performance and ion transport efficiency for rate capability.
2Productivity
If the contact area between positive electrode active material and electrolytic solution is enlarged, then the rate capability improves, but the internal resistance may increase
Solution Approach 1:
The hollow spherical structure with controlled porosity (0-20%) creates an optimal balance between contact area and resistance. The three-dimensional pore passages enlarge the effective contact area between material and electrolytic solution, facilitating rapid lithium-ion transport and improving rate capability. Simultaneously, the controlled porosity prevents excessive internal resistance by maintaining structural integrity and optimal ion transport pathways.
Solution Approach 2:
The patent transitions from conventional two-dimensional surface contact to three-dimensional pore passage networks within the hollow spherical structure. This dimensional transformation creates numerous interconnected pathways for lithium-ion transport, enlarging the effective contact area while maintaining short migration distances and reducing internal resistance through optimized spatial architecture.
3Reliability
If the hollow structure is used to buffer volume change, then the cycle performance improves, but the energy density may decrease
Solution Approach 1:
The hollow spherical structure with optimized porosity (0-20%) buffers volume changes during charging and discharging cycles, maintaining structural stability and improving cycle performance. The controlled porosity ensures that the hollow structure provides sufficient mechanical flexibility for volume expansion/contraction while minimizing the empty space to preserve energy density.
Solution Approach 2:
The patent optimizes the ratio of inner diameter (0.3-5 μm) to outer wall thickness (3-10 μm) to balance volume buffering capacity with material utilization. By controlling these dimensional parameters, the hollow structure achieves optimal protection against volume-induced degradation while maximizing the amount of active material per unit volume, thereby maintaining high energy density.
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 hollow structure buffers volume change, increases lithium-ion active sites, and reduces internal resistance, resulting in improved cycle performance, discharge capacity, and energy density, while maintaining excellent rate capability.
Implementation Method 1
the presence of the hollow structure can buffer the volume change of the positive electrode active material during the charging and discharging processes, thereby stabilizing the structure
Implementation Method 2
the positive electrode active material with the hollow structure contains numerous three-dimensional pore passages, which enlarge the contact area between the material and the electrolytic solution, shorten the lithium-ion migration distance
Data Source
AI summary
The present application provides a positive electrode active material, a preparation method therefor, a secondary battery, and an electrical apparatus. The chemical formula of the positive electrode active material is LiaNixCoyM1−x−yO2, where M comprises one or more of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg and Nb, 0.55≤x≤1.0, 0≤y≤0.45, 0.8≤a≤1.2, the positive electrode active material being a hollow structure, and the inner diameter d1 of the hollow structure being 0.3 μm-5 μm.