Double-Layer Positive Electrode for Battery Bondability and Capacity
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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, leading to reduced performance and lifetime.
Innovation Solution
A positive electrode structure comprising a double-layered active material configuration with olivine structured compounds and layered compounds, utilizing specific weight ratios of functional additives and conductive materials to enhance bondability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single-layer active material structure is used, then the device complexity is low, but the capacity and energy density are insufficient
Solution Approach 1:
The positive electrode is divided into two distinct active material layers: a first active material layer containing olivine structured compounds (LiFePO4) and a second active material layer containing layered compounds (LiCoO2). This segmentation allows each layer to contribute different functional properties, with the olivine layer providing structural stability and the layered layer providing high capacity, thereby resolving the contradiction between capacity and structural simplicity.
Solution Approach 2:
The patent employs a composite electrode structure where two different active materials with complementary properties are combined in a layered configuration. The olivine structured compound provides excellent structural stability and long cycle life, while the layered compound contributes high specific capacity. This composite approach enables the electrode to achieve both high capacity and improved reliability without excessive complexity.
2Strength
If high amounts of binder are used, then the bondability between current collector and active material is improved, but the energy density and capacity are reduced
Solution Approach 1:
The patent applies different binder amounts to different layers of the active material. The first active material layer (olivine structured) uses a first binder with a specific amount, while the second active material layer (layered compound) uses a second binder with a different amount. This local differentiation allows optimization of bondability in each layer without uniformly increasing binder content throughout the electrode, thereby maintaining energy density while ensuring adequate adhesion.
Solution Approach 2:
The patent optimizes the binder content parameter in each layer to achieve the desired bondability. By carefully controlling the amount of binder in the first and second active material layers, the patent achieves sufficient adhesion between the active materials and current collector without excessive binder content that would reduce the active material proportion and lower capacity.
3Reliability
If conductive materials are increased to improve conductivity, then the electrical conductivity is improved, but the energy density is reduced
Solution Approach 1:
The patent incorporates conductive materials locally within each active material layer rather than uniformly distributing them throughout the electrode. The first conductive material is added to the first active material layer and the second conductive material to the second active material layer. This localized approach ensures adequate electrical conductivity for electron transport while minimizing the overall proportion of non-active conductive material, thereby preserving energy density.
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 electrode design improves capacity and lifetime characteristics by enhancing the bondability and conductivity between the current collector and the active materials, resulting in improved performance of rechargeable lithium batteries.
Implementation Method 1
each including an active material that allows intercalation and deintercalation of lithium ions
Implementation Method 2
The batteries produce electrical energy from redox reactions that take place as lithium ions are intercalated into or deintercalated from the positive electrode and the negative electrode
Data Source
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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 first particles that are an olivine structured compound, 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 an olivine structured compound, a second conductive material, and a second binder. The first particles are in the form of a single particle, and the third particles are in the form of secondary particles. The first binder and the first conductive material constitute a first functional additive, the second binder and the second conductive material constitute a second functional additive, and a ratio of a weight ratio of the second functional additive in the second active material layer to a weight ratio of the first functional additive in the first active material layer is about 1.0 to about 2.03.