Positive Electrode Active Mass Layer for High-Rate Lithium Batteries
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high rate characteristics and cycle-life performance, particularly in applications requiring rapid input and output capabilities and long-lasting capacity, such as in vehicles for idle stop-start systems.
Innovation Solution
A positive electrode for rechargeable lithium batteries is designed with a specific active mass layer composition and structure, comprising a composite oxide, activated carbon, conductive material, and binder, optimized in density and thickness to achieve rapid input and output characteristics and extended cycle life, using a current collector made of Al and an electrolyte with an organic solvent and lithium salt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the positive active mass layer uses conventional composition and structure, then the battery structure is simple and easy to manufacture, but the high rate characteristics and cycle-life performance are insufficient
Solution Approach 1:
The positive active mass layer is constructed as a composite material system comprising positive active material particles (such as LiCoO2, LiMn2O4, or LiNi1-x-yCoxMnyO2), conductive material particles (such as acetylene black or carbon nanotubes), and binder particles (such as polyvinylidene fluoride or carboxymethyl cellulose). This composite structure synergistically improves cycle-life characteristics while maintaining manageable manufacturing complexity through standardized component ratios.
2Quantity of substance
If the positive active mass layer is optimized for high capacity, then the energy density increases, but the rapid input and output capabilities deteriorate
Solution Approach 1:
The positive active mass layer is designed with non-uniform local composition: regions with higher positive active material content provide high capacity, while regions with optimized conductive material and binder distribution ensure rapid ion and electron transport. This local quality variation allows simultaneous achievement of high energy density and rapid input-output capabilities.
Solution Approach 2:
The invention optimizes specific parameters including the weight ratio of positive active material to conductive material to binder (typically 80:5:15 or similar ratios), particle size distribution (0.1-10 μm for active material, 0.01-1 μm for conductive material), and layer thickness (10-50 μm). These parameter changes enable the layer to achieve both high capacity and rapid response characteristics.
3Quantity of substance
If the positive active mass layer thickness is increased for higher capacity, then the energy density improves, but the high rate discharge performance decreases
Solution Approach 1:
The positive active mass layer is designed with a porous structure having controlled porosity (30-70%) and pore size distribution (0.1-10 μm). This porous architecture increases the effective surface area for lithium ion insertion/extraction, allowing higher active material content while maintaining short ion transport paths. The porous structure enables both high capacity and rapid ion transport by providing multiple parallel pathways for ion diffusion.
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 optimized positive electrode provides rechargeable lithium batteries with rapid high-rate input and output capabilities and improved cycle-life characteristics, suitable for vehicle applications, enhancing both capacity and performance.
Implementation Method 1
generate electrical energy by oxidation and reduction reactions when lithium ions are intercalated/deintercalated in the positive electrode and negative electrode
Implementation Method 2
a positive active mass layer formed on the current collector. The positive active mass layer consists of a positive active material, activated carbon, a conductive material, and a binder
Implementation Method 3
an electrolyte including an organic solvent and a lithium salt
Data Source
Figure 1
Figure 2
AI summary
A positive electrode according to one embodiment of the present invention includes a current collector, and a positive active mass layer formed on the current collector, including a positive active material, active carbon, a conductive material, and a binder, wherein a ratio of the active mass density of the positive active mass layer and the thickness of the positive active mass layer fulfills the condition: 0.09≤active mass density of the active mass layerg/cc/thickness of the active mass layerµm≤0.3.