LiCoO2 Positive Active Material with Spinel Surface for Battery Conductivity
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Solution Overview
Problem
Current rechargeable lithium batteries face challenges in achieving high energy density and cycle-life characteristics due to limitations in the positive active material's structure and interaction with electrolytes, leading to reduced electrical conductivity and capacity.
Innovation Solution
A positive active material for rechargeable lithium batteries is developed, comprising LiCoO2 particles with a layered structure internally and a spinel structure on the surface, manufactured by mixing cobalt and lithium raw materials and heat-treating them under specific temperature conditions to enhance electrical conductivity and minimize pores, thereby improving cycle-life characteristics and rate capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LiCoO2 positive active material is used, then the battery can store energy, but the electrical conductivity is insufficient and cycle-life characteristics are poor
Solution Approach 1:
The patent applies local quality by creating a spinel structure specifically on the surface of the LiCoO2 particles while maintaining the layered structure in the interior. This dual-structure approach allows the surface to provide high electrical conductivity and stability, while the interior maintains high capacity for lithium intercalation, thereby simultaneously improving electrical conductivity and cycle-life characteristics.
Solution Approach 2:
The patent employs composite materials by combining two different crystal structures (layered LiCoO2 and spinel LiCo2O4) within a single particle system. The composite structure leverages the advantages of both phases: the layered structure provides high capacity and the spinel structure provides high conductivity and stability, resolving the contradiction between conductivity and reliability.
2Use of energy by moving object
If the positive active material interacts extensively with electrolytes, then ion exchange can occur, but Li2CO3 forms on the surface reducing capacity
Solution Approach 1:
The spinel surface layer acts as a protective barrier that modifies the local quality of the particle surface. This spinel layer reduces the harmful interaction between the layered LiCoO2 interior and the electrolyte, preventing Li2CO3 formation while still allowing necessary lithium ion transport, thus protecting the high-capacity interior structure.
3Quantity of substance
If high energy density is pursued, then battery capacity increases, but structural stability decreases leading to poor cycle-life
Solution Approach 1:
The composite structure combines the high-capacity layered LiCoO2 phase with the highly stable spinel LiCo2O4 phase. This allows the battery to achieve high energy density from the layered interior while the spinel surface provides structural stability and resistance to degradation, enabling both high capacity and good cycle-life characteristics.
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 approach results in a rechargeable lithium battery with improved cycle-life characteristics and rate capability by increasing electrical conductivity and reducing the amount of Li2CO3 on the surface, leading to enhanced battery performance.
Implementation Method 1
heat-treating the mixture. The heat-treating may include firing the mixture at a first temperature, and, after the firing, maintaining a resultant for a predetermined time at a second temperature lower than the first temperature
Implementation Method 2
firing the mixture at a first temperature
Data Source
AI summary
A positive active material for a rechargeable lithium battery includes a LiCoO2 particle. An interior of the particle has a layered structure and a surface of the particle has a spinel structure.