Rock Salt Coating for LiCoO2 Cathodes Above 4.2 V
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Solution Overview
Problem
Lithium rechargeable batteries face challenges in achieving high capacity and power while maintaining stability, particularly when the charge voltage exceeds 4.2 V, leading to instability in the LiCoO2 crystal structure and elution of Co3+ ions.
Innovation Solution
A positive electrode active material is developed by modifying the surface of lithium cobalt oxide (LiCoO2) doped with aluminum (Al) to have a rock salt crystal structure, incorporating a cobalt-based compound with a rock salt crystal structure as a coating layer, which enhances surface stability and prevents Co elution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge voltage is increased above 4.2 V to achieve high capacity and power, then the battery capacity and power are improved, but the LiCoO2 crystal structure becomes unstable and Co3+ ions are eluted
Solution Approach 1:
A coating layer containing a cobalt-based compound with rock salt crystal structure is formed on the surface of LiCoO2 particles before battery assembly. This preliminary surface modification prevents Co3+ ion elution when high charge voltages above 4.2V are applied, enabling high capacity and power without compromising structural stability.
Solution Approach 2:
The positive electrode active material is designed as a composite structure combining LiCoO2 core particles with a coating layer of cobalt-based compound having rock salt crystal structure. This composite material approach allows the battery to achieve high capacity and power while maintaining crystal structure stability at elevated charge voltages.
2Power
If the charge voltage is increased above 4.2 V to achieve high capacity and power, then the battery capacity and power are improved, but Co3+ ions are eluted and side reactions with electrolyte occur
Solution Approach 1:
The coating layer of cobalt-based compound with rock salt crystal structure transforms the harmful effect of Co3+ ion elution into a beneficial protective barrier. This coating prevents direct contact between LiCoO2 and electrolyte, eliminating side reactions while enabling high power operation at charge voltages above 4.2V.
Solution Approach 2:
The coating layer acts as an intermediary substance between LiCoO2 and the electrolyte. It mediates the interaction by preventing Co3+ ion elution and blocking side reactions, allowing the battery to operate at high power without the harmful effects of ion elution and electrolyte degradation.
3Stability of the object's composition
If aluminum doping is applied to LiCoO2 to stabilize crystal structure, then the crystal structure stability is improved, but the surface modification complexity increases
Solution Approach 1:
The invention combines aluminum doping within the LiCoO2 crystal lattice with surface coating of cobalt-based compound in a single integrated process. This merging of bulk modification and surface coating simplifies the overall manufacturing complexity while achieving both crystal structure stability and prevention of Co3+ ion elution.
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 modified positive electrode active material effectively maintains surface structure stability even at high charge voltages, significantly reducing Co elution and improving battery performance, thereby enabling lithium rechargeable batteries to achieve high capacity, high power, and stability.
Implementation Method 1
a coating layer positioned on a surface of the core particle and containing a cobalt (Co)-based compound having a rock salt crystal structure
Data Source
AI summary
A surface of a LiCoO2-based positive electrode active material to have a rock salt crystal structure is provided. Specifically, a positive electrode active material for a lithium rechargeable battery is provided, including: a core particle containing lithium cobalt oxide doped with aluminum (Al); and a coating layer positioned on a surface of the core particle and containing a cobalt (Co)-based compound having a rock salt crystal structure. A method of producing the positive electrode active material is also provided using a solid-phase method. The positive electrode active material can be applied to a positive electrode, lithium rechargeable battery, battery module, battery pack, and the like.