Gradient High-Nickel Cathode Material for Capacity and Thermal Stability
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Solution Overview
Problem
Ternary positive electrode materials face a trade-off between high specific capacity and thermal stability due to the valence changes of Ni elements during charging/discharging, leading to safety hazards and performance degradation, especially when the material is highly delithiated, and existing methods for enhancing stability are not suitable for large-scale production or single crystal materials.
Innovation Solution
A high-nickel single crystal ternary positive electrode material with a gradient concentration of Ni, Co, and Mn elements, where the surface composition is optimized to increase Mn and Co proportions by ≥7% and ≥5% respectively, and the particle size is maintained between 2.5 μm and 55 μm, along with a specific sintering process involving multiple heating steps and the use of Mn and Co-containing solid powders to form a layered structure, enhancing thermal and kinetic stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni content is increased to obtain higher battery energy density, then specific capacity is improved, but thermal stability deteriorates due to reduced Co/Mn elements and increased trivalent ions
Solution Approach 1:
The patent applies local quality by creating a gradient concentration distribution where the surface region has different compositional characteristics (lower Ni, higher Co/Mn) compared to the bulk (higher Ni). This allows the bulk to provide high capacity while the surface provides thermal stability and safety, resolving the contradiction between specific capacity and thermal stability.
Solution Approach 2:
The patent creates a composite structure with gradient concentration, combining regions of high Ni content (for capacity) and high Co/Mn content (for stability) within a single material phase. This composite approach allows simultaneous optimization of both specific capacity and thermal stability that cannot be achieved with uniform composition.
2Reliability
If gradient concentration coating method is used to improve thermal stability, then oxygen release temperature is increased, but manufacturing complexity increases due to fine control requirements at precursor stage
Solution Approach 1:
The patent implements preliminary action by establishing the gradient concentration distribution during the precursor synthesis stage itself, rather than requiring subsequent complex coating processes. The gradient is formed inherently during material synthesis, simplifying the overall manufacturing process while achieving the desired thermal stability improvement.
3Reliability
If gradient concentration method is applied to enhance stability, then thermal stability is improved, but applicability to single crystal materials is lost because precursors lose concentration differences due to solid-phase diffusion during high-temperature sintering
Solution Approach 1:
The patent applies parameter changes by optimizing the sintering temperature and time parameters to minimize solid-phase diffusion effects. By carefully controlling these thermal parameters, the gradient concentration distribution is preserved during the sintering process, enabling the method to be successfully applied to single crystal material synthesis while maintaining thermal stability improvements.
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 results in a high-safety, high-capacity, and high-thermal stability ternary positive electrode material suitable for large-scale production, reducing gas production and capacity fading during high-temperature storage and cycling, while maintaining excellent kinetic performances and cycle stability.
Implementation Method 1
a specific sintering process involving multiple heating steps
Implementation Method 2
precursors with gradient concentrations will lose concentration differences due to solid-phase diffusion of metal ions during high-temperature sintering
Data Source
AI summary
The present disclosure discloses a high-safety ternary positive electrode material and a method for preparing the same; wherein the ternary positive electrode material has a chemical composition of Lia(NixCoyMn1-x-y)1-bMbO2-cAc, wherein 0.75≤a≤1.2, 0.75≤x<1, 0<y≤0.15, 1−x−y>0, 0≤b≤0.01, 0≤c≤0.2, M is one or more selected from the group consisting of Al, Zr, Ti, Y, Sr, W and Mg, and A is one or more selected from the group consisting of S, F and N; and CMn−(1−x−y)≥0.07; CCo−y≥0.05; 0≤[CMn−(1−x−y)]/(CCo−y)≤2.0. The ternary positive electrode material of the present disclosure is a high-nickel single crystal material with gradient concentration; it has the advantages of high capacity and high thermal stability, and the preparation method is simple, and is suitable for large-scale production.