Core-Shell Ternary Cathode Doping for Capacity and Stability
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Solution Overview
Problem
Ternary positive electrode materials face challenges such as low charging and discharging efficiency, low high-temperature storage performance, low electrical conductivity, poor cycle performance, and reduced energy density due to agglomeration, with existing doping methods struggling to achieve high discharging specific capacity and structural stability simultaneously.
Innovation Solution
A ternary positive electrode material is developed with a core-shell structure, where the inner layer is doped with a low-valence metal element (M) like Al, Mg, or Zn, and the outer layer is doped with a high-valence metal element (N) like W, Mo, or Ta, to stabilize the structure and enhance TM-O bond strength, reducing lithium-nickel intermixing and oxygen vacancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If doping elements are introduced to improve structural stability, then structural stability is improved, but discharging specific capacity is reduced
Solution Approach 1:
The patent applies local quality by differentiating doping strategies between the outer layer (high-valence elements for stability) and inner layer (low-valence elements for capacity), allowing each region to have optimized properties for its specific function while maintaining overall structural integrity and performance
Solution Approach 2:
The patent uses composite materials by combining multiple doping elements with different valence states (high-valence W, Mo, Ta in outer layer; low-valence Al, Mg, Zn in inner layer) to create a multi-functional doped ternary material that simultaneously achieves structural stability and high discharging capacity
2Stability of the object's composition
If high-valence metal elements are used for doping, then structural stability is improved, but electronic conductivity is reduced
Solution Approach 1:
The patent places high-valence metal elements (W, Mo, Ta) specifically in the outer layer where their primary function is to strengthen TM-O bonds and stabilize the crystal structure, while low-valence elements in the inner layer maintain electronic conductivity, thus each region optimizes for its primary function
Solution Approach 2:
The combination of high-valence and low-valence doping elements creates a composite doping system where the high-valence elements provide structural stability in the outer layer while low-valence elements in the inner layer preserve electronic conductivity, achieving both properties simultaneously
3Productivity
If lithium-nickel intermixing is reduced through doping, then charging and discharging efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent reduces lithium-nickel intermixing by applying targeted doping at specific locations (outer layer and inner layer with different element types), which prevents cation disordered structure formation more effectively than uniform doping, thereby improving charging and discharging efficiency
Solution Approach 2:
The dual-layer doping strategy with different element combinations creates a composite structure that more effectively suppresses lithium-nickel intermixing and prevents cation disordering, leading to improved electrochemical performance despite the increased manufacturing complexity
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 material exhibits higher initial gram capacity, improved high-temperature cycle performance, and enhanced high-temperature storage performance, with the dual-doping approach outperforming single-element modifications.
Implementation Method 1
Doping is a modification method that introduces other metal or non-metal atoms into the ternary positive electrode material crystal. For lithium composite oxides of nickel, cobalt, and manganese, it mostly refers to the substitution of some atoms of nickel, cobalt, and manganese.
Implementation Method 2
When inequivalent cations are used for doping, the valence state of transition metal ions in the ternary material will increase or decrease. As such, holes or electrons are generated, the energy band structure of the material changes, and the intrinsic electronic conductivity thereof is thereby increased.
Data Source
AI summary
The disclosure relates to the field of lithium-ion batteries and discloses a ternary positive electrode active material in a form of particles, and an area of 1 nm to 1,000 nm in a direction from an outermost surface to a center in a cross-section of each of the particles is defined as an outer layer, and the rest in the cross-section of each of the particles is defined as an inner layer. The inner layer is doped with a first metal element M, the outer layer is doped with a second metal element N, and a valence state of the first metal element M is lower than a valence state of the second metal element N. The center of the ternary active material particles is doped with the first metal element M in a low-valence state.