Core-Shell Cathode Material for High-Nickel Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high nickel content with improved capacity, cycle characteristics, thermal stability, and maintaining a stable structure at high voltages, particularly in maintaining the microstructure and lifespan during long cycles.
Innovation Solution
A positive active material is developed with a layered structure, incorporating lithium, nickel, cobalt, manganese, and tungsten, where the spinel structure is formed on the surface of primary particles before initial charging, and the doping element content is optimized to enhance lattice parameters and BET specific surface area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content is used in the positive active material, then discharge capacity is improved, but thermal stability and structural stability deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the central core region contains high nickel content (Ni≥85 mol%) for high capacity, while the outer shell region contains lower nickel content and protective elements (Co, Mn, W) for stability. This spatial differentiation of composition allows simultaneous achievement of high discharge capacity and thermal/structural stability.
Solution Approach 2:
The patent uses composite materials by combining multiple metal elements (Ni, Co, Mn, W) in a layered composite structure. The core region is rich in Ni for capacity, while the shell region contains protective elements that form a stable structure, creating a composite material that exhibits both high capacity and improved stability properties.
2Quantity of substance
If high nickel content is used, then capacity is improved, but cycle characteristics worsen
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the central core region contains high nickel content (Ni≥85 mol%) for high capacity, while the outer shell region contains lower nickel content and protective elements (Co, Mn, W) for stability. This spatial differentiation of composition allows simultaneous achievement of high discharge capacity and thermal/structural stability.
Solution Approach 2:
The patent applies preliminary action by pre-forming the protective shell structure around the high-nickel core before the battery undergoes cycling. The shell acts as a pre-established protective barrier that prevents degradation of the high-nickel core during subsequent charge-discharge cycles, thereby improving cycle characteristics.
3Quantity of substance
If high voltage charging is applied, then capacity is improved, but microstructure stability and lifespan deteriorate
Solution Approach 1:
The patent applies preliminary action by pre-forming the protective shell structure around the high-nickel core before the battery undergoes cycling. The shell acts as a pre-established protective barrier that prevents degradation of the high-nickel core during subsequent charge-discharge cycles, thereby improving cycle characteristics.
Solution Approach 2:
The patent applies beforehand cushioning by incorporating a protective shell layer that cushions and absorbs the mechanical stress and structural degradation caused by high-voltage charging. This protective layer prevents micro-crack formation and maintains microstructure stability during high-voltage operation.
4Quantity of substance
If nickel content is increased, then discharge capacity is improved, but micro-crack formation increases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the central core region contains high nickel content (Ni≥85 mol%) for high capacity, while the outer shell region contains lower nickel content and protective elements (Co, Mn, W) for stability. This spatial differentiation of composition allows simultaneous achievement of high discharge capacity and thermal/structural stability.
Solution Approach 2:
The patent applies beforehand cushioning by incorporating a protective shell layer that cushions and absorbs the mechanical stress and structural degradation caused by high-voltage charging. This protective layer prevents micro-crack formation and maintains microstructure stability during high-voltage operation.
Data Source
AI summary
Provided is a positive active material for a lithium secondary battery, the positive active material including: a secondary particle comprising a group of a plurality of primary particles, in which the primary particles comprise first primary particles provided on a surface portion of the secondary particle and each having a spinel structure at an end thereof, and the primary particle is made of lithium (Li), nickel (Ni), manganese (Mn), and tungsten (W) which is a doping element.