Radial Dopant Gradient in Lithium Spinel Cathode Particles
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Solution Overview
Problem
Lithium-ion batteries face challenges with high degradation and capacity fading, particularly in maintaining high energy density and stability during cycling.
Innovation Solution
A lithium positive electrode active material with a chemical composition of Li x Ni y Mn 2-y-z1-z2 D1 z1 D2 z2 O 4, where D1 is non-uniformly distributed and D2 is uniformly distributed along the radial axis of the material particles, utilizing specific dopants like Co, Cu, Ti, Zn, and Fe to reduce degradation while maintaining capacity, with a process involving heating to control dopant distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dopant is added to reduce degradation, then stability is improved, but capacity is reduced
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of dopant M in the lithium composite metal oxide particles, where the dopant concentration is higher at the surface and decreases toward the center. This spatial variation in dopant distribution allows the surface regions to provide stabilization while the interior regions maintain higher capacity, resolving the contradiction between stability improvement and capacity reduction.
2Quantity of substance
If high nickel content is used to increase capacity, then energy density is improved, but degradation increases
Solution Approach 1:
The patent uses local quality by concentrating the stabilizing dopant M primarily in the surface regions of the particles, where it can protect the high-nickel interior from degradation without significantly reducing the overall capacity. The surface acts as a protective shell that allows the high-capacity nickel-rich core to function effectively.
Solution Approach 2:
The patent creates a composite structure where lithium composite metal oxide particles containing high nickel content are combined with dopant M that has different physical and chemical properties. This composite approach allows the material to simultaneously achieve high capacity from the nickel-rich composition and improved stability from the dopant, resolving the contradiction between energy density and degradation.
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 reduced capacity fading, maintaining high capacity similar to undoped LNMO, with less than 2% fading at room temperature and 55°C, and achieving high tap density and stability, enhancing energy density and electrochemical performance.
Implementation Method 1
the distribution of dopant D1 is non-uniform along a radial axis of the material particles and wherein the distribution of the dopant D2 is uniform along the radial axis of the material particles
Data Source
AI summary
The invention relates to a lithium positive electrode active material comprising at least 95 wt% spinel having a chemical composition of LixNiyMn2-y-z1-z2D1z1D2z2O4, wherein 0.9≤ x ≤ 1.1, 0.4≤y≤0.5, 0.005 ≤ z1 ≤ 0.2, 0 ≤ z2 ≤ 0.2, wherein D1 and D2 are dopants chosen between the following elements: Co, Cu, Ti, Zn, Mg, Fe or combinations thereof. D1 and D2 are different dopants, and the lithium positive electrode active material is a powder composed of material particles, wherein the distribution of dopant D1 is non-uniform along a radial axis of the material particles and the distribution of the dopant D2 is substantially uniform along the radial axis of the material particles. The invention also relates to a process for preparing the lithium positive electrode active material of the invention and a secondary battery comprising the lithium positive electrode active material of the invention.