Nickel-Rich Cathode Coating for Faster Lithium Diffusion and Cycle Life
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density, efficient lithium diffusion, and cycle-life due to issues with volume changes and residual lithium, which lead to side reactions and capacity degradation.
Innovation Solution
A positive active material is developed comprising a lithium nickel-based composite oxide with a coating layer of fiber-shaped lithium manganese composite oxide, enhancing lithium diffusion and reducing residual lithium, thereby improving charge and discharge characteristics and cycle-life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lithium nickel-based composite oxide is used as the positive active material, then high energy density is achieved, but volume changes during charge and discharge cause stress and capacity degradation
Solution Approach 1:
The patent uses a composite material structure where plate-shaped primary particles are agglomerated to form secondary particles. This composite structure accommodates volume changes during lithium insertion/extraction, reducing stress and preventing capacity degradation while maintaining high energy density.
Solution Approach 2:
The positive active material is divided into plate-shaped primary particles that agglomerate to form secondary particles. This segmentation allows each primary particle to independently handle volume changes, reducing overall stress on the electrode structure during cycling.
2Ease of manufacture
If the positive active material surface is left uncoated, then manufacturing simplicity is maintained, but residual lithium on the surface causes side reactions with electrolyte
Solution Approach 1:
A coating layer of lithium manganese composite oxide is introduced as an intermediary between the lithium nickel-based composite oxide and the electrolyte. This coating layer prevents direct contact between residual lithium and the electrolyte, suppressing side reactions while maintaining manufacturing feasibility through a single-step coating process.
3Ease of manufacture
If conventional particle structures are used, then manufacturing is simple, but lithium diffusion rates are insufficient for high power performance
Solution Approach 1:
The patent employs plate-shaped primary particles with specific morphology rather than conventional spherical particles. The plate shape provides larger surface area and shorter diffusion paths for lithium ions, significantly improving lithium diffusion rates while maintaining compatibility with existing manufacturing processes.
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 results in improved lithium battery capacity, reduced gas generation, and enhanced phase stability and cycle-life by facilitating smoother lithium ion movement and suppressing side reactions.
Implementation Method 1
improving lithium diffusion (e.g., lithium diffusion rates) during charge and discharge
Implementation Method 2
reducing unreacted residual lithium
Data Source
AI summary
A positive active material for a rechargeable lithium battery includes a lithium nickel-based composite oxide including a secondary particle in which a plurality of plate-shaped primary particles are agglomerated; and a coating layer including a fiber-shaped lithium manganese composite oxide, wherein the fiber-shaped lithium manganese composite oxide is attached to the surface of the lithium nickel-based composite oxide.