Segmented Lithium Battery Negative Electrode for Volume Expansion
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Solution Overview
Problem
Conventional lithium secondary batteries face issues with structural degradation due to volumetric expansion and increased resistance in high-loading/high-density electrodes, which affect the cycle life and lithium ion mobility.
Innovation Solution
A negative electrode structure with alternating concave and non-concave portions in the second active material layer, filled with a conductive layer, and a carbon-based first layer for stability, enhances lithium ion diffusion and buffers volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity negative electrode active material (silicon, tin, etc.) is used to increase energy density, then the theoretical maximum capacity increases significantly, but the electrode undergoes repeated substantial expansion and contraction leading to structural degradation and reduced cycle life
Solution Approach 1:
The negative electrode active material layer is divided into multiple layers with different materials (carbon-based layer, silicon-based layer, tin-based layer, etc.). Each layer is segmented into plurality of regions arranged in a specific pattern, allowing high-capacity materials to be distributed in controlled amounts rather than concentrated, thereby reducing overall volumetric expansion while maintaining high capacity.
Solution Approach 2:
Different regions of the negative electrode active material layer have different compositions and functions. High-capacity materials (silicon, tin) are placed in specific regions where their expansion can be managed, while carbon-based materials are placed in other regions to provide structural stability. This local differentiation allows each material to perform its optimal function while mitigating the harmful effects of expansion.
2Quantity of substance
If high-loading and high-density electrodes are developed to meet high-energy density specifications, then the energy density increases, but the resistance increases due to larger pore resistance and longer lithium-ion migration paths
Solution Approach 1:
The electrode structure is segmented into multiple layers and plurality of regions, creating a hierarchical architecture that reduces the average migration distance for lithium ions. The multiple layers provide multiple pathways for ion transport, effectively reducing the overall resistance despite high loading density.
Solution Approach 2:
The invention transitions from a conventional planar electrode structure to a multi-layered three-dimensional architecture. By stacking multiple layers with alternating high-capacity and carbon-based materials, the design creates vertical and horizontal pathways for lithium ion migration, effectively reducing the migration path length and resistance while maintaining high 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 structured electrode improves structural stability and reduces resistance, maintaining high-loading performance with enhanced lithium ion mobility and cycle life.
Implementation Method 1
silicon and its alloys have the problem of repeated substantial expansion (up to 4 times) and contraction during charging and discharging
Implementation Method 2
high-loading/high-density electrodes face the problem of increased resistance due to larger pore resistance and longer lithium-ion migration paths, which slow down the diffusion of lithium ions within the electrode
Implementation Method 3
conventional lithium secondary batteries primarily use carbon-based compounds as the negative electrode active material, which can reversibly intercalate and deintercalate lithium ions while maintaining structural and electrical properties
Data Source
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AI summary
Disclosed herein relates to a negative electrode for a lithium secondary battery. According to exemplary embodiments, a negative electrode is provided. The negative electrode includes: a current collector; a first negative electrode active material layer; and a second negative electrode active material layer. The second negative electrode active material layer includes a plurality of concave portions indented toward the first negative electrode active material layer and a plurality of non-concave portions, the plurality of the concave portions and the plurality of the non-concave portions are alternately arranged in a horizontal direction, and a surface of the second negative electrode active material layer has a pattern formed by a plurality of steps.