Lithium-Inorganic Coated High-Nickel Cathodes for Stable Interfaces
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Solution Overview
Problem
Lithium nickel cobalt metal oxide-based batteries face limitations in thermal stability, interfacial resistance, and life characteristics due to electrolyte decomposition and structural instability, particularly under high-temperature and high-voltage conditions, necessitating improved surface and interfacial stability.
Innovation Solution
A positive electrode active material is developed with a nickel-containing lithium transition metal oxide coated with a lithium-containing inorganic compound layer, formed by adjusting the pH of a suspension containing an aqueous inorganic acid solution, to enhance valence electron density and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel cobalt metal oxide is used as positive electrode active material, then reversible capacity is improved, but thermal stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a dual-layer coating structure where the inner layer (lithium phosphate or lithium silicate) provides thermal stability close to the active material, while the outer layer (amorphous carbon) provides electrical conductivity and additional protection at the surface. This localized functional differentiation resolves the contradiction between maintaining high nickel content for capacity and ensuring thermal stability.
Solution Approach 2:
The patent uses composite materials by combining multiple coating materials with different functions: lithium phosphate/lithium silicate for thermal stability, amorphous carbon for electrical conductivity, and lithium fluoride for interfacial stability. This composite coating system simultaneously addresses thermal stability, electrical conductivity, and interfacial resistance issues while maintaining high reversible capacity.
2Quantity of substance
If lithium nickel cobalt metal oxide is used as positive electrode active material, then reversible capacity is improved, but interfacial resistance increases
Solution Approach 1:
The patent applies local quality by placing amorphous carbon specifically at the outermost surface of the dual-layer coating structure. This carbon layer locally provides excellent electrical conductivity at the interface with the electrolyte, reducing interfacial resistance while the inner lithium phosphate/silicate layer maintains thermal stability close to the active material.
Solution Approach 2:
The patent uses intermediary materials (lithium phosphate, lithium silicate, lithium fluoride) as intermediate layers between the lithium nickel cobalt oxide and the electrolyte. These intermediary layers mediate the interface by providing chemical stability, reducing side reactions, and maintaining low interfacial resistance, thereby preserving high reversible capacity.
3Quantity of substance
If lithium nickel cobalt metal oxide is used as positive electrode active material, then reversible capacity is improved, but life characteristics deteriorate
Solution Approach 1:
The patent applies beforehand cushioning by pre-forming a protective dual-layer coating on the lithium nickel cobalt oxide surface before battery assembly. This coating acts as a cushion that prevents direct contact between the active material and electrolyte, suppressing side reactions and structural degradation from the beginning, thereby extending battery life while maintaining high capacity.
Solution Approach 2:
The patent uses composite materials with the inner layer (lithium phosphate/silicate) providing long-term structural stability and the outer layer (amorphous carbon) providing persistent electrical conductivity. This composite structure continuously protects the high-nickel active material throughout charge-discharge cycles, maintaining both high reversible capacity and excellent life characteristics.
4Ease of manufacture
If dry coating method is used to form coating layer, then manufacturing process is simplified, but coating uniformity deteriorates
Solution Approach 1:
The patent uses hydraulic principles by employing a wet coating method where an aqueous slurry containing coating materials is applied to the active material surface. The slurry formulation and controlled drying process ensure uniform distribution and adhesion of both inner and outer coating layers, achieving superior coating uniformity compared to dry methods while maintaining manufacturing feasibility.
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 improved coating process reduces resistance and enhances the stability and output characteristics of the battery, preventing side reactions and maintaining efficiency over repeated charge and discharge cycles.
Implementation Method 1
a lithium-containing inorganic compound layer formed on a surface of the nickel-containing lithium transition metal oxide
Data Source
AI summary
A positive electrode active material includes a nickel-containing lithium transition metal oxide containing nickel in an amount of 60 mol % or more based on a total number of moles of transition metals excluding lithium, and a lithium-containing inorganic compound layer formed on a surface of the nickel-containing lithium transition metal oxide, wherein the positive electrode active material has a first peak in a range of 5 eV or less, a second peak in a range of 7 eV to 13 eV, and a third peak in a range of 20 eV to 30 eV when intensity is measured by X-ray photoelectron spectroscopy, and the first peak has a maximum value of 80% to 120% with respect to the third peak. A method of preparing the positive electrode active material, and a positive electrode and a lithium secondary battery are also provided.