Gradient High-Nickel Single-Crystal Cathode for Capacity and Thermal Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ternary positive electrode materials face a contradiction between high specific capacity and thermal stability due to the valence change of Ni during charging/discharging, leading to safety hazards, and existing methods for gradient concentration materials 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, where the surface atomic ratios of Mn and Co are increased relative to the bulk, and a method involving precursor mixing, sintering, and secondary coating with Mn and Co-containing powders to achieve high capacity and 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 increased proportion of trivalent ions and reduced Co/Mn elements
Solution Approach 1:
The patent applies gradient concentration distribution where the surface layer has different composition (lower Ni, higher Co and Mn) compared to the bulk (high Ni content). This local quality variation allows the bulk to provide high capacity while the surface provides thermal stability and safety during charging/discharging cycles.
2Reliability
If gradient concentration positive electrode materials are constructed by coating surface with middle/low-nickel cladding layer, then thermal stability is improved, but manufacturing complexity increases and large-scale production becomes difficult
Solution Approach 1:
The gradient concentration is built into the precursor particles before the main sintering process. By controlling the precursor composition and using a one-step sintering method, the gradient structure is formed preliminarily, avoiding the need for subsequent complex coating operations and enabling large-scale production.
Solution Approach 2:
The patent combines the gradient concentration design with a one-step sintering process, merging what would traditionally be separate steps (precursor preparation and coating) into a single integrated manufacturing process, thereby simplifying production.
3Quantity of substance
If gradient concentration method is used to create high-nickel polycrystalline materials, then capacity and stability are improved, but the method cannot be extended to single crystal materials due to solid-phase diffusion during high-temperature sintering
Solution Approach 1:
The patent optimizes sintering parameters (temperature, time, atmosphere) to control the degree of solid-phase diffusion. By carefully adjusting these parameters, the gradient concentration is preserved during sintering, enabling the production of single crystal materials with gradient composition rather than uniform composition.
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 material with enhanced thermal stability, reduced gas production, and improved kinetic performance, suitable for large-scale production and single crystal forms, while maintaining high specific capacity and cycle stability.
Implementation Method 1
heating the mixture A in an air or oxygen atmosphere, wherein the mixture A is held at 700～1,100℃ for 4-15 hours
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
Figure 1
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.