LiF-Coated High-Nickel Cathode for Resistance Reduction
Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high-temperature stability and discharge capacity due to residual lithium on the surface of cathode active materials, leading to deteriorated charge/discharge characteristics when nickel content is increased, as it results in increased resistance and lithium leakage.
Innovation Solution
A composite cathode active material is developed with a lithium metal oxide core coated with a LiF layer, which includes a significant amount of nickel and optionally a carbonaceous material, reducing resistance and side reactions with the electrolyte solution, thereby enhancing stability and discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amount of nickel in the cathode active material is increased to increase capacity, then the discharge capacity is improved, but the resistance increases and charge/discharge characteristics deteriorate
Solution Approach 1:
A coating layer comprising LiF and a carbonaceous material is applied on the surface of the cathode active material. This coating layer acts as an intermediary that reduces resistance between the high-nickel cathode material and the electrolyte solution, thereby improving charge/discharge characteristics while maintaining high discharge capacity.
Solution Approach 2:
The cathode active material is designed as a composite structure with a core comprising lithium metal oxide containing nickel and a coating layer comprising LiF and a carbonaceous material. This composite structure combines the high capacity benefits of high-nickel content with the low resistance properties of the carbonaceous material coating.
2Stability of the object's composition
If the cathode active material is rinsed to reduce residual lithium on the surface, then high-temperature stability is improved, but lithium inside the material leaks out and charge/discharge characteristics deteriorate
Solution Approach 1:
The coating layer comprising LiF and a carbonaceous material serves as a protective intermediary layer that prevents direct contact between residual lithium on the cathode active material surface and the electrolyte solution. This eliminates the need for rinsing while preventing lithium leakage, thereby maintaining both high-temperature stability and charge/discharge characteristics.
3Reliability
If a coating layer is applied to reduce resistance, then charge/discharge characteristics are improved, but the device complexity increases
Solution Approach 1:
The coating layer utilizes materials (LiF and carbonaceous material) that can be applied in controlled thicknesses (e.g., 1-100 nm) to optimize electrical conductivity without significantly increasing structural complexity. The specific composition ratios and thickness parameters are tuned to achieve the desired resistance reduction 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 composite cathode active material improves charge/discharge characteristics and high-temperature stability by reducing resistance and suppressing lithium leakage, resulting in increased discharge capacity and prolonged battery lifespan.
Implementation Method 1
a resistance of the composite cathode active material is lower than that of the core
Implementation Method 2
reducing resistance and side reactions with the electrolyte solution
Data Source
AI summary
A composite cathode active material, a cathode including the composite cathode active material, and a lithium battery including the cathode are provided. The composite cathode active material includes a core including a lithium metal oxide and a coating layer on the core, wherein the lithium metal oxide includes two or more transition metals including nickel (Ni), an amount of Ni within one mole of the two or more transition metals included in the lithium metal oxide is about 0.65 mol or greater, the coating layer includes LiF, and a resistance of the composite cathode active material is lower than that of the core.