Dual-Coated High-Nickel Cathode for Structural and Thermal Stability
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Solution Overview
Problem
Existing high-capacity lithium secondary battery positive electrode active materials, such as LiNiO2, suffer from structural collapse during charging and discharging and have low thermal stability, making them unsuitable for commercial use due to oxidation number issues.
Innovation Solution
A lithium nickel-based positive electrode active material with a core containing at least 80 mol% Ni, coated with a first layer of Group 5 and Group 6 elements and sulfur, and a second needle-like layer of B, LiOH, Li2CO3, and Li2SO4, which improves electrochemical stability and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiNiO2 is used as positive electrode active material to achieve high capacity, then battery capacity is improved, but structural collapse occurs during charging and discharging and thermal stability is low
Solution Approach 1:
The patent applies composite materials by creating a core-shell structure where the core is LiNi0.8Co0.1Mn0.1O2 (high-capacity nickel-based compound) and the shell is a protective coating layer. This composite structure allows the high-capacity core material to function while the protective shell prevents structural collapse and improves thermal stability, thus resolving the contradiction between high capacity and structural reliability.
Solution Approach 2:
The patent applies local quality by modifying only the surface region of the positive electrode active material through coating, rather than changing the bulk composition. The coating layer is applied locally on the surface of the LiNi0.8Co0.1Mn0.1O2 particles to provide protection against structural collapse and thermal degradation, while the high-capacity core material remains intact in its bulk form.
2Quantity of substance
If LiNiO2 is used to achieve high capacity, then battery capacity is improved, but thermal stability is low due to oxidation number problem
Solution Approach 1:
The protective coating shell forms a composite structure that acts as a thermal barrier between the high-capacity LiNi0.8Co0.1Mn0.1O2 core and the external environment. This composite material approach allows the core to maintain high capacity while the shell provides thermal stability by preventing oxidation and stabilizing the surface at elevated temperatures.
Solution Approach 2:
The coating layer is applied beforehand to the surface of the LiNi0.8Co0.1Mn0.1O2 particles to provide preemptive protection against thermal degradation and oxidation. This prior cushioning prevents direct exposure of the high-capacity material to thermal stress, thereby maintaining both high capacity and thermal stability during battery operation.
3Quantity of substance
If high-nickel content material is used to improve capacity, then battery capacity is improved, but structural collapse occurs during charging and discharging
Solution Approach 1:
The core-shell composite structure protects the high-nickel-content LiNi0.8Co0.1Mn0.1O2 core from structural collapse during charging and discharging. The protective shell maintains structural integrity by preventing Jahn-Teller distortion and phase transitions that would otherwise occur in high-nickel materials under electrochemical cycling conditions.
Solution Approach 2:
The coating is applied locally on the surface of the high-nickel material particles to provide targeted structural support where it is most needed during electrochemical cycling. This local modification stabilizes the surface structure without altering the high-capacity bulk composition, allowing the material to maintain both high capacity and structural stability.
Data Source
AI summary
It relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same, wherein the positive electrode active material for lithium secondary battery, comprising: a core containing a lithium nickel-based compound having a Ni content of 80 mol % or more; and a coating material positioned on at least a portion of the core surface; wherein, the coating material includes a first coating material containing at least one of group 5 elements and group 6 elements; and S; and a second coating material including B, LiOH, Li2CO3 and Li2SO4, and the second coating material is a needle-like material.