Ternary positive electrode active material and lithium-ion battery having same
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Solution Overview
Problem
Ternary positive electrode materials in lithium-ion batteries face challenges such as low charging and discharging efficiency, poor high-temperature storage performance, low electrical conductivity, and reduced energy density due to agglomeration, requiring effective doping strategies to enhance structural stability and specific capacity.
Innovation Solution
A ternary positive electrode active material is developed with a specific doping approach where the inner layer is doped with a low-valence metal element (e.g., Na, K, Mg, Al, Zn, Cu, Ca) and the outer layer with a high-valence metal element (e.g., W, Ta, Nb, Mo, Tc, Ru, Rh, Sb), optimizing the valence states and content to stabilize the structure and enhance TM-O bond strength, thereby improving lithium-nickel intermixing and oxygen vacancy suppression.
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 specific capacity decreases
Solution Approach 1:
The patent applies local quality by implementing dual-layer doping where the inner layer contains first doping elements (Li, Al, Fe, Cr, Ce, Mg) and the outer layer contains second doping elements (F, Si, W, Mo, Nb, Ta). This spatial differentiation allows the inner layer to focus on structural stability while the outer layer optimizes electrochemical performance, resolving the contradiction between structural stability and specific capacity
Solution Approach 2:
The patent uses composite materials by combining multiple doping elements in a layered structure within the ternary positive electrode material. The composite doping strategy with different element combinations in inner and outer layers creates synergistic effects that simultaneously improve structural stability and maintain high specific capacity, overcoming the trade-off between these two properties
2Reliability
If doping amount is increased to enhance electronic conductivity, then electronic conductivity is improved, but structural stability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the doping amounts of different elements in different layers. The first doping elements are controlled at 0.01-0.10 mol ratio and second doping elements at 0.001-0.05 mol ratio, optimizing the balance between electronic conductivity enhancement and structural stability maintenance
3Quantity of substance
If high-valence elements are used for doping to increase energy density, then energy density is improved, but high-temperature storage performance deteriorates
Solution Approach 1:
The patent applies local quality by placing high-valence second doping elements (F, Si, W, Mo, Nb, Ta) specifically in the outer layer where they can enhance energy density through valence state adjustment, while the inner layer with first doping elements maintains structural stability for high-temperature performance
Solution Approach 2:
The patent uses beforehand cushioning by introducing doping elements that preemptively stabilize the crystal structure against thermal degradation. The dual-layer doping creates a protective effect that cushions the material from high-temperature stress while maintaining 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
This approach results in higher initial gram capacity and improved high-temperature cycle and storage performance, balancing structural stability and specific capacity, outperforming single-element doping 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
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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.