Two-Layer Positive Electrode for High-Voltage Lithium Battery Stability
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Solution Overview
Problem
Lithium manganese-based oxides suffer from poor oxidation stability at high voltages, limiting their use in lithium secondary batteries, and existing materials like LiCoO2 have thermal instability and high costs, making them unsuitable for large-scale applications.
Innovation Solution
A positive electrode with a two-layer structure is developed, comprising a first positive electrode active material layer with Li1+aMn2-bM1bO4-cAc and a second layer with Li1+a1Mn z Fe 1-z PO4-yA1y, where M1 and A1 are specific elements, and the layers have different or similar average particle diameters, along with optimized conductive agents and binders, to enhance stability and output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium manganese-based oxide is used as positive electrode active material, then cost is reduced and capacity is improved, but oxidation stability at high voltage deteriorates
Solution Approach 1:
The patent applies composite materials by combining lithium manganese-based oxide (Li1+aMn2-bM1bO4-c) with lithium iron phosphate (Li1+a1MnzFe1-zPO4-yA1y) in a two-layer structure. This composite approach allows the electrode to achieve high capacity from the manganese-based oxide while the iron phosphate component provides oxidation stability at high voltages, resolving the contradiction between capacity improvement and reliability maintenance.
Solution Approach 2:
The patent segments the positive electrode active material layer into two distinct layers: a first layer containing lithium manganese-based oxide for high capacity, and a second layer containing lithium iron phosphate for oxidation stability. This segmentation allows each layer to perform its specific function optimally, with the manganese layer providing capacity and the iron phosphate layer providing stability, thereby resolving the technical contradiction.
2Power
If LiCoO2 is used as positive electrode active material, then operating voltage and capacity characteristics are improved, but thermal stability deteriorates and cost increases
Solution Approach 1:
The patent replaces expensive LiCoO2 with lithium manganese-based oxide and lithium iron phosphate composite materials that are more cost-effective. While the manganese-based oxide has limitations, the composite structure with iron phosphate provides the necessary stability, achieving a balance between cost reduction and performance maintenance.
Solution Approach 2:
The patent uses composite materials (lithium manganese-based oxide + lithium iron phosphate) to replace LiCoO2, maintaining high operating voltage characteristics from the manganese component while adding thermal and structural stability through the iron phosphate component, thereby resolving the contradiction between power and stability.
3Quantity of substance
If lithium manganese-based oxide is used to replace LiCoO2, then cost is reduced, but output characteristics deteriorate
Solution Approach 1:
The patent creates a composite structure combining lithium manganese-based oxide (cost-effective, high capacity) with lithium iron phosphate (good output characteristics). This composite approach maintains cost efficiency from the manganese-based material while improving output characteristics through the iron phosphate component, resolving the contradiction between cost reduction and productivity maintenance.
4Quantity of substance
If single-layer positive electrode active material layer is used, then device complexity is reduced, but cannot simultaneously achieve high capacity and oxidation stability
Solution Approach 1:
The patent segments the positive electrode active material layer into two functional layers: the first layer with lithium manganese-based oxide for high capacity and the second layer with lithium iron phosphate for oxidation stability. This segmentation enables simultaneous achievement of high capacity and oxidation stability, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent uses a composite two-layer structure where each layer contains different materials optimized for specific functions. The first layer provides high capacity through lithium manganese-based oxide, while the second layer provides oxidation stability through lithium iron phosphate, allowing both capacity and stability to be achieved simultaneously.
Data Source
Figure 1~2
AI summary
The present invention relates to a positive electrode including a positive electrode active material layer formed on a positive electrode collector, wherein the positive electrode active material layer has a two-layer structure including a first positive electrode active material layer, which is formed on the positive electrode collector and includes a first positive electrode active material represented by Formula 1 and a second positive electrode active material represented by Formula 2, and a second positive electrode active material layer which is formed on the first positive electrode active material layer and includes a third positive electrode active material represented by Formula 1, wherein an average particle diameter D50 of the third positive electrode active material is the same or different from an average particle diameter D50 of the first positive electrode active material, and a lithium secondary battery including the same.