Positive Electrode Surface Layer Structure for Battery Cycle Life
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high capacity and stable cycle-life characteristics due to limitations in positive electrode active materials.
Innovation Solution
A positive electrode active material is designed with a core and surface layer, where the core has a first crystalline structure, typically layered, and the surface layer includes a different second crystalline structure, predominantly layered, with a specific volume ratio and thickness to enhance lithium diffusion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-structure positive electrode active material is used, then the manufacturing process is simple, but the capacity and cycle-life characteristics are insufficient
Solution Approach 1:
The positive electrode active material is divided into two distinct parts: a core region with a first crystalline structure and a surface layer with a second crystalline structure. This segmentation allows each region to have optimized properties for different functions, improving overall reliability without requiring complex manufacturing processes
Solution Approach 2:
The patent creates a composite material structure where the core and surface layer have different crystalline structures. This composite approach combines the advantages of different crystal structures to achieve both high capacity and excellent cycle-life characteristics
2Quantity of substance
If a high-capacity positive electrode active material is used, then the energy density increases, but the stability during charging and discharging deteriorates
Solution Approach 1:
Different regions of the positive electrode active material are given different local qualities through distinct crystalline structures. The core region has one crystal structure optimized for capacity, while the surface layer has another structure optimized for stability, allowing both high capacity and structural stability to coexist
Solution Approach 2:
The surface layer with its specific crystalline structure acts as a protective cushion for the core material during charging and discharging cycles. This pre-designed surface layer prevents structural degradation before it can occur, maintaining stability throughout the battery's operational life
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 proposed active material exhibits improved capacity and cycle-life characteristics, particularly at low and high temperatures, making it suitable for high-power batteries.
Implementation Method 1
the surface layer includes the first crystalline structure and a second structure different from the first crystalline structure... exhibits higher capacity and good cycle-life characteristics
Data Source
AI summary
The present invention relates to a positive electrode active material for a rechargeable lithium battery and a rechargeable lithium battery including same, wherein the positive electrode active material comprises a core and a surface layer formed on the surface of the core, the core comprising a first crystalline structure, the surface layer comprising a first crystalline structure and a second crystalline structure different from the first crystalline structure, the first crystalline structure being present more than the second crystalline structure in the surface layer.