LiF-Coated Cathode Material for Low-Gas Lithium-Ion Batteries
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Solution Overview
Problem
Lithium nickel-based composite oxides in rechargeable lithium batteries generate excess gas due to unreacted residual lithium, leading to battery swelling and degradation of cycle-life characteristics.
Innovation Solution
A positive active material comprising a lithium nickel-based composite oxide with a surface-modifying layer of lithium fluoride and a lithium manganese composite oxide, featuring a specific crystal structure and porosity, is developed to reduce residual lithium and enhance lithium diffusion, thereby mitigating gas generation and improving battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If lithium nickel-based composite oxide is used as positive active material, then charge and discharge capacity is improved, but unreacted residual lithium generates gas during high temperature storage causing battery swelling and cycle-life degradation
Solution Approach 1:
The patent removes unreacted residual lithium from the surface of lithium nickel-based composite oxide particles through selective dissolution in water, extracting the harmful component while preserving the functional active material
Solution Approach 2:
The patent creates a composite structure by coating lithium fluoride on the surface of lithium nickel-based composite oxide, forming a protective layer that prevents gas generation while maintaining electrochemical performance
2Quantity of substance
If unreacted residual lithium is present on the surface of positive active material, then gas generation occurs during high temperature storage, but removing residual lithium is necessary to prevent battery swelling
Solution Approach 1:
The patent converts the harmful effect of residual lithium into a beneficial process by using its reactivity with water to selectively dissolve and remove it, transforming a problem into a solution mechanism
Solution Approach 2:
The patent introduces water as an intermediary substance that selectively reacts with and removes residual lithium, and introduces lithium fluoride as a coating material that mediates between the active material and the environment to prevent gas generation
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 solution effectively reduces unreacted residual lithium, suppresses gas generation, and enhances the charge and discharge capacity and cycle-life characteristics of rechargeable lithium batteries, leading to improved stability and efficiency.
Implementation Method 1
a surface-modifying layer including lithium fluoride on the surface of at least one of the lithium nickel-based composite oxide and the lithium manganese composite oxide
Implementation Method 2
improving lithium diffusion (e.g., lithium diffusion rates) during charge and discharge
Data Source
AI summary
A positive active material for a rechargeable lithium battery includes a lithium nickel-based composite oxide and a lithium manganese composite oxide, wherein the positive active material includes a surface-modifying layer including lithium fluoride on the surface of at least one of the lithium nickel-based composite oxide and the lithium manganese composite oxide. The lithium nickel-based composite oxide includes a secondary particle in which a plurality of plate-shaped primary particles are agglomerated, and the secondary particle has a regular array structure in which (003) planes of the plurality of primary particles are aligned or oriented normal to the surface of the secondary particle. The lithium manganese composite oxide is present in two or more types of crystal lattice structures, wherein the positive active material comprises 1,000 ppm or less of unreacted residual lithium at the surface thereof.