Double-Layer Lithium Battery Anode for Density-Porosity Balance
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in achieving high capacity, reliability, and rate capability due to limitations in anode active material structure and porosity, which affect the battery's performance and lifespan.
Innovation Solution
The anode for lithium secondary batteries incorporates a double-layered anode active material structure with two types of anode active materials having different hardness, where the lower layer has a higher amount of a second anode active material with a secondary particle structure, and the upper layer has a higher amount of a first anode active material with a single-particle shape, optimizing the density and porosity to enhance capacity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the anode active material layer uses a single-layer structure with uniform composition, then the manufacturing process is simple, but the battery capacity and rate capability are limited
Solution Approach 1:
The anode active material layer is divided into two distinct layers: a lower layer with higher second anode active material content and an upper layer with higher first anode active material content. This segmentation allows each layer to contribute differently to battery performance, achieving high capacity and rate capability while managing structural complexity through functional differentiation.
Solution Approach 2:
Different regions of the anode active material layer are assigned different compositions and properties. The lower layer contains more second anode active material for high capacity, while the upper layer contains more first anode active material for rate capability. This local quality variation optimizes performance across different operational requirements.
2Quantity of substance
If the anode active material layer has high density, then the battery capacity improves, but the porosity decreases affecting lithium ion transport
Solution Approach 1:
The anode active material layer is designed with controlled porosity (0.27 mL/g or more) to maintain lithium ion transport pathways while achieving high density. The porous structure allows efficient ion diffusion throughout the material, ensuring reliability in lithium ion transport even at high active material density.
Solution Approach 2:
The anode active material layer combines two different anode active materials with complementary properties. This composite structure achieves high overall density while maintaining adequate porosity for ion transport, as each material contributes different characteristics that balance density and transport requirements.
3Speed
If the anode active material layer has high microporosity, then the lithium ion diffusion is fast improving rate capability, but the density decreases reducing battery capacity
Solution Approach 1:
The anode is segmented into two layers with different microporosity characteristics. The lower layer has higher density with moderate porosity for capacity, while the upper layer has optimized porosity for fast lithium ion diffusion. This segmentation allows the battery to achieve both high rate capability and high capacity without compromising either property.
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
This configuration results in improved anode density, reduced micro-pore ratio, and enhanced battery capacity, lifespan, and rate capability, as demonstrated by increased effective porosity and reduced microporosity, leading to better overall battery performance.
Implementation Method 1
The anode active material may include a material capable of intercalating and de-intercalating lithium ions
Implementation Method 2
A total intrusion amount of mercury to pores having a diameter of 3 nm to 10 μm in the anode active material layer measured by a mercury porosimeter is 0.27 ml/g or more
Data Source
AI summary
An anode for a lithium secondary battery includes an anode current collector, and an anode active material layer formed on the anode current collector. The anode active material layer including a lower anode active material layer formed on the anode current collector and an upper anode active material layer formed on the lower anode active material layer. Each of the lower anode active material layer and the upper anode active material layer includes a first anode active material and a second anode active material having a hardness less than that of the first anode active material. A total intrusion amount of mercury to pores having a diameter of 3 nm to 10 μm in the anode active material layer measured by a mercury porosimeter is 0.27 ml/g or more.