Coated Nickel Cathode Material for High-Temperature Li-Ion Cycling
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving high energy density while maintaining good high-temperature cycling and storage performance due to the poor stability of traditional positive electrode active materials.
Innovation Solution
A nickel-containing lithium transition metal oxide positive electrode active material with a specific chemical formula, including a coating layer of an oxide of element M2, is developed, where M1 is doped uniformly into the lithium transition metal oxide, enhancing specific capacity, mechanical strength, and stability, and M2 forms a protective coating to prevent corrosion by the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel-containing lithium transition metal oxide is used as positive electrode active material, then energy density is improved, but high-temperature cycling performance deteriorates
Solution Approach 1:
The patent uses composite materials by combining nickel-containing lithium transition metal oxide with a protective coating layer comprising oxide of element M2 (such as Al2O3, SiO2, TiO2, or their combinations). This composite structure allows the inner nickel-containing material to provide high energy density while the outer coating layer provides high-temperature stability and prevents degradation, thus resolving the contradiction between energy density and high-temperature cycling performance
Solution Approach 2:
The patent applies local quality by creating a gradient structure where the core region contains nickel-rich lithium transition metal oxide for high capacity, while the surface region contains the protective oxide coating for stability. The coating layer thickness and composition are optimized to provide localized protection at the surface where degradation occurs most, while maintaining the high-capacity bulk material properties
2Stability of the object's composition
If traditional positive electrode active materials are used, then stability is maintained, but energy density is insufficient
Solution Approach 1:
The patent creates a composite structure where the stable oxide coating layer (M2Ox) envelops the high-capacity nickel-containing lithium transition metal oxide core. This allows the system to achieve both high energy density from the nickel-containing material and high stability from the protective coating, overcoming the limitation of traditional materials that prioritize stability over energy density
3Quantity of substance
If M1 is doped into lithium transition metal oxide, then specific capacity is improved, but structural stability deteriorates
Solution Approach 1:
The patent applies local quality by concentrating the M1 doping (which enhances capacity) in the bulk crystal structure while maintaining the surface integrity through the protective oxide coating. The coating layer compensates for the structural instability introduced by doping, allowing high specific capacity without sacrificing structural stability during cycling
Solution Approach 2:
The composite structure of doped lithium transition metal oxide core with oxide coating shell allows the doped core to provide high specific capacity while the undoped or lightly doped coating provides structural stability, resolving the contradiction between capacity enhancement through doping and structural stability
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 significantly improves the energy density, high-temperature storage performance, and high-temperature cycling performance of lithium-ion secondary batteries by increasing the compacted density and structural stability of the positive electrode active material, reducing side reactions and gas production.
Implementation Method 1
M1 is doped uniformly into the lithium transition metal oxide, enhancing specific capacity, mechanical strength, and stability
Implementation Method 2
M2 forms a protective coating to prevent corrosion by the electrolyte
Data Source
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AI summary
This application discloses a positive electrode active material and a preparation method thereof, a positive electrode plate, a lithium-ion secondary battery, and an apparatus containing such lithium-ion secondary battery. The positive electrode active material includes secondary particles and a coating layer applied on an exterior surface of the secondary particle, where the secondary particle includes a lithium transition metal oxide that contains a doping element M1, the coating layer includes an oxide of element M2, M1 is selected from one or more of Si, Ti, Cr, Mo, V, Ge, Se, Zr, Nb, Ru, Rh, Pd, Sb, Te, Ce, and W, and M2 is selected from one or more of Mg, Al, Ca, Ce, Ti, Zr, Zn, Y, and B; a relative deviation of local mass concentration of element M1 in the secondary particle is less than 20%; and the secondary particle from the core to the exterior surface of the particle includes a plurality of layers of primary particles arranged along radial direction of the secondary particle, and the number of primary particles contained in the outermost layer of the plurality of layers ranges from 5 per µm2 to 50 per µm2.