LNMO Cathode Coating With LVPF for HF-Resistant Cycle Life
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Solution Overview
Problem
Conventional lithium nickel manganese oxide positive electrode materials experience capacity decline, rate performance reduction, and shortened cycle life due to surface reactions with HF generated from the electrolyte during high-potential charging and discharging.
Innovation Solution
A high-voltage composite positive electrode material is created by coating lithium vanadium fluorophosphate (LVPF) powders with a tavorite-type structure onto lithium nickel manganese oxide (LNMO) powders using a dry mechanofusion method, optimizing the particle size ratio and mixing conditions to enhance electrical conductivity and surface protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If lithium nickel manganese oxide positive electrode material is used at high potential, then power density is improved, but capacity and cycle life are reduced due to surface reactions with HF
Solution Approach 1:
A lithium phosphate coating layer is applied to the surface of the lithium nickel manganese oxide particles. This coating layer acts as an intermediary barrier between the positive electrode material and the electrolyte, preventing direct contact and harmful surface reactions with HF while allowing lithium ion diffusion. The coating maintains high power density by preserving the high voltage platform while improving cycle life by protecting against electrolyte decomposition and surface damage.
2Power
If lithium nickel manganese oxide positive electrode material is used at high potential, then power density is improved, but rate performance is reduced due to surface reactions with HF
Solution Approach 1:
The lithium phosphate coating serves as a mediator that facilitates rather than hinders lithium ion transport. The coating layer is designed to be ion-conductive, allowing rapid lithium ion diffusion while blocking harmful electrolyte components. This enables the material to maintain excellent rate performance by preventing surface reactions that would otherwise impede ion transport at high rates.
3Ease of manufacture
If conventional lithium nickel manganese oxide is used, then manufacturing cost is reduced by avoiding cobalt, but electrical properties and cycle life are reduced due to surface damage from electrolyte
Solution Approach 1:
The lithium phosphate coating is applied through a simple wet chemical process that is easy to implement in existing manufacturing lines. The coating process uses readily available chemicals and operates under mild conditions, adding minimal complexity to the manufacturing process. This approach maintains the cost advantage of cobalt-free materials while significantly improving cycle life by protecting against electrolyte-induced surface damage.
4Ease of manufacture
If lithium nickel manganese oxide is used, then price is reduced compared to ternary oxides, but capacity and electrical properties are reduced due to HF-induced surface reactions
Solution Approach 1:
The lithium phosphate coating prevents HF-induced surface reactions that would otherwise consume active lithium and reduce capacity. By blocking the harmful interaction between the electrolyte and the positive electrode material surface, the coating preserves the bulk material's electrochemical activity and capacity. The coating itself contributes additional lithium ions to the electrochemical reactions, further enhancing capacity while maintaining the price advantage of cobalt-free composition.
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 material significantly improves the cycle life and capacity retention rate by about 10% at a 1C charge-discharge rate, maintaining good fast charging performance and electrical properties, while preventing electrolyte-induced surface damage.
Implementation Method 1
A high-voltage composite positive electrode material is created by coating lithium vanadium fluorophosphate (LVPF) powders with a tavorite-type structure onto lithium nickel manganese oxide (LNMO) powders using a dry mechanofusion method
Data Source
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AI summary
A high-voltage composite positive electrode material and manufacturing method thereof are disclosed. The high-voltage composite positive electrode material includes lithium nickel manganese oxide (LNMO) powders and lithium vanadium fluorophosphate (LVPF) powders. The LNMO powders have a first average particle diameter. A molar ratio of the LVPF powders to the LNMO powders is equal to or less than 0.5. The LVPF powders have a second average particle diameter. The second average particle diameter is less than one-tenth of the first average particle diameter, and the LVPF powders and the LNMO powders are mixed by a mechanically mixing method, so that the LVPF powders are coated on the surfaces of the LNMO powders to form the high-voltage composite positive electrode material.