Lithium Nickel Composite Oxide Coating for Structural Stability
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Solution Overview
Problem
High nickel content in lithium composite metal oxides for lithium batteries leads to structural instability due to the formation of NiO, which reacts with the electrolyte, reducing battery capacity and lifespan.
Innovation Solution
A positive active material with an island-type discontinuous coating layer of olivine-type phosphate compounds, such as LiFePO4, is applied to a lithium nickel composite oxide core, inhibiting side reactions with the electrolyte and enhancing structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amount of nickel in lithium composite metal oxide is increased to increase battery capacity, then battery capacity is improved, but structural stability of the positive active material degrades due to formation of NiO impurity
Solution Approach 1:
A coating layer comprising amorphous aluminum oxide or aluminum hydroxide is formed on the surface of the lithium nickel composite oxide particles. This coating layer acts as an intermediary barrier that prevents direct contact between NiO impurity and the electrolyte, thereby maintaining structural stability while allowing high nickel content (70-85 mole %) to be used for increased battery capacity
Solution Approach 2:
The coating layer is applied specifically to the surface region of the lithium nickel composite oxide particles where NiO impurity forms. This localized treatment addresses the harmful effects at the particle surface without altering the bulk composition and high nickel content, thus preserving both capacity and stability
2Quantity of substance
If the amount of nickel in lithium composite metal oxide is increased to increase battery capacity, then battery capacity is improved, but charge and discharge efficiency and lifespan properties decrease due to structural instability
Solution Approach 1:
The amorphous aluminum oxide or aluminum hydroxide coating layer serves as a protective intermediary that maintains structural integrity during charge and discharge cycles. This enables high nickel content materials to achieve both high capacity and reliable long-term performance by preventing electrolyte-induced degradation
Solution Approach 2:
The coating layer is formed in advance on the lithium nickel composite oxide particles before battery assembly. This preliminary protective action prevents structural degradation during subsequent charge and discharge operations, ensuring both efficiency and lifespan properties are maintained from the first cycle
3Quantity of substance
If NiO impurity is formed due to high nickel content, then battery capacity increases, but thermal stability of the positive active material degrades
Solution Approach 1:
The amorphous aluminum oxide or aluminum hydroxide coating layer acts as a thermal barrier that isolates the NiO impurity from the electrolyte. This intermediary protection maintains thermal stability even when high nickel content leads to NiO formation, allowing capacity enhancement without compromising safety
Data Source
AI summary
Provided is a positive active material, a positive electrode including the positive active material, a lithium battery, and a manufacturing method of the same. The positive active material includes a core including a lithium nickel composite oxide and a coating layer formed on the core. The coating layer improves structural stability of the positive active material. Accordingly, lifespan properties of a lithium battery including the positive active material may be improved.