Single-Crystal Ternary Cathode Gradient Structure for High-Ni Stability
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Solution Overview
Problem
Ternary cathode materials with secondary spherical structures suffer from low structural strength, uneven charging and discharging, and high-temperature expansion issues, leading to reduced cycle performance and energy density in lithium-ion batteries.
Innovation Solution
A ternary cathode material with a micron-sized single-crystalline particle structure of LiNi1-x-y-zCoxMnyMzO2, where the molar ratios of elements vary between the central and surface areas, and includes elements like Al, Mg, Ti, Ga, Nb, Zr, W, or Ta, is developed, enhancing structural strength and reducing side reactions through a co-precipitation and sintering method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a secondary spherical structure is used, then the cathode material can be easily manufactured, but the structural strength is low and the structure breaks at high compaction density
Solution Approach 1:
The cathode material is divided into primary particles (5-20 μm) that aggregate to form secondary spherical structures. This segmentation allows the material to maintain ease of manufacture while improving structural strength through the hierarchical architecture, where primary particles serve as building blocks with inherent strength that prevents complete structural failure during compaction.
Solution Approach 2:
The cathode material uses a composite structure combining primary particles with specific crystal phases (R-3m layered structure) and controlled morphology. This composite approach integrates the manufacturability of spherical aggregates with the structural strength of well-defined primary particles, resolving the contradiction between ease of manufacture and structural integrity.
2Ease of manufacture
If a secondary spherical structure is used, then the cathode material can be easily manufactured, but the surface is rough causing locally uneven charging and discharging
Solution Approach 1:
The invention controls the local quality of the cathode material by optimizing the morphology and size distribution of primary particles (5-20 μm) that constitute the secondary spherical structure. This local optimization ensures more uniform surface characteristics at the particle level, leading to more evenly distributed charging and discharging currents while maintaining the overall spherical structure for ease of manufacture.
3Strength
If a single-crystalline particle structure is used, then the structural strength is high and compaction density increases, but the discharge capacity and rate performance are low
Solution Approach 1:
The cathode material adopts a segmented hierarchical structure where primary particles (5-20 μm) with good crystallinity aggregate to form secondary spherical structures. This segmentation enables the material to achieve high compaction density through the ordered arrangement of primary particles while maintaining adequate discharge capacity through the appropriate size and distribution of these segments, avoiding the limitations of both fully single-crystalline and fully aggregated structures.
4Quantity of substance
If high nickel content is used, then the discharge capacity increases, but the surface pH is high causing gelatinization and expansion
Solution Approach 1:
The invention optimizes the local quality of the cathode material by precisely controlling the nickel content and distribution within primary particles (5-20 μm) and their aggregation structure. This local optimization allows high nickel content regions to provide high discharge capacity while the overall structured aggregation and surface characteristics maintain lower effective surface pH, preventing gelatinization and expansion issues.
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 single-crystalline structure increases compaction density, improves thermal stability, and inhibits phase transitions, resulting in enhanced cycle performance, energy density, and reduced side reactions, thereby improving the safety and rate performance of lithium-ion batteries.
Implementation Method 1
formulating a nickel source, a cobalt source, a manganese source, and an M source into a solution A in a first container according to the stoichiometric ratio Ni:Co:Mn:M=a1:x1:y1:z1, and formulating the nickel source, the cobalt source, the manganese source and the M source into a solution B in a second container according to the stoichiometric ratio Ni:Co:Mn:M=a2:x2:y2:z2; pumping the solution A into a reactor containing an alkali solution and undergoing a first co-precipitation reaction; and after the first co-precipitation reaction is completed, pumping the solution B into the reactor containing the alkali solution and undergoing a second co-precipitation reaction to prepare a precursor material
Implementation Method 2
mixing the precursor material with a lithium salt, pre-sintering, and pulverizing to obtain a first material; mixing the first material with a flux, subjecting the material to a primary sintering, pulverizing, washing to remove the flux and drying to obtain a second material; and subjecting the second material to a secondary sintering, cooling, and pulverization to obtain a ternary cathode material of single-crystalline particle structure
Data Source
AI summary
A ternary cathode material, a preparation method thereof, and a lithium ion battery are provided. The ternary cathode material comprises a micron-sized single-crystalline particle structure of LiNi1-x-y-zCoxMnyMzO2, wherein 0.6<1-x-y-z<1.0, 0<x<0.2, 0<y<0.3, and 0<z<0.1; and the single-crystalline particle structure comprises a central area and surface layer area, wherein the molar ratio of elements in the central area meets Ni:Co:Mn:M=a1:x1:y1:z1, and the molar ratio of elements in the surface layer area meets Ni:Co:Mn:M=a2:x2:y2:z2, in which 0.85≤a1<1.0, 0<x1≤0.1, 0<y1≤0.15, 0≤z1≤0.05, 0.3≤a2≤0.7, 0.2≤x2, y2≤0.4, and 0≤z2≤0.05, provided that z1 and z2 are not simultaneously zero, and a1/(a1+x1+y1+z1)>a2/(a2+x2+y2+z2); and M comprises at least one selected from Al, Mg, Ti, Ga, Nb, Zr, W, Mo and Ta.