Dual-Layer Positive Electrode Balancing Capacity and Bondability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density and capacity while maintaining stable bondability between the current collector and the positive electrode active material, which affects the preparation and performance of the electrode plate.
Innovation Solution
A positive electrode structure comprising a current collector with a first active material layer containing olivine structured compounds and a second active material layer with layered compounds, along with specific conductive materials and binders, enhances bondability and improves capacity and lifetime characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer positive electrode structure is used, then the manufacturing process is simple, but the bondability between current collector and active material is insufficient
Solution Approach 1:
The positive electrode is divided into two distinct layers: a first active material layer containing olivine structured compounds (LiFePO4) that provides strong bondability with the current collector, and a second active material layer containing layered compounds (LiCoO2) that provides high capacity. This segmentation allows each layer to specialize in different functions, resolving the contradiction between manufacturing simplicity and bondability.
Solution Approach 2:
The patent uses a composite structure combining two different active materials with complementary properties. The olivine structured LiFePO4 in the first layer ensures strong adhesion to the current collector, while the layered LiCoO2 in the second layer provides high specific capacity. This composite approach enables both good bondability and high performance without complicating the overall manufacturing process.
2Quantity of substance
If high capacity active materials are used, then the energy density increases, but the bondability with current collector deteriorates
Solution Approach 1:
The patent segments the electrode into two layers where the first layer uses olivine structured LiFePO4 that inherently provides strong bondability with the current collector, while the second layer uses layered LiCoO2 that provides high capacity. This segmentation allows high-capacity materials to be used without compromising bondability, as the bonding function is dedicated to the first layer.
Solution Approach 2:
Different regions of the electrode are assigned different materials with locally optimized properties. The first layer near the current collector uses materials optimized for strong adhesion, while the second layer uses materials optimized for high capacity. This local quality differentiation resolves the contradiction between capacity and bondability.
Data Source
AI summary
A positive electrode for a rechargeable lithium battery includes a current collector, a first active material layer on the current collector, and a second active material layer on the first active material layer. The first active material layer includes a first particles that are olivine structured compounds, second particles that are a layered compound, a first conductive material, and a first binder. The second active material layer includes third particles that are olivine structured compounds, a second conductive material, and a second binder. The first particles are in the form of secondary particles in which a plurality of first primary particles are agglomerated, the first particles have an average diameter (D50) of about 3 μm to about 7 μm, and the second particles have an average diameter (D50) of about μ3 m to about 14 μm.