Dual-Layer Silicon Negative Electrode for Capacity and Cycle Life
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Solution Overview
Problem
Lithium secondary batteries face rapid capacity decrease due to volume expansion and contraction of silicon-based negative electrode active materials, particularly in silicon-based electrodes, which affects their lifespan and performance.
Innovation Solution
A negative electrode for secondary batteries is designed with a dual-layer structure, where a first silicon-based active material layer with a low silicon content is combined with a thicker second layer containing a higher percentage of silicon-based active material, along with carbon-based materials and conductive components, to enhance capacity and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to increase capacity, then energy density is improved, but volume expansion and contraction occur during charging and discharging, leading to rapid capacity decrease and reduced cycle life
Solution Approach 1:
The negative electrode active material layer is divided into two distinct layers: a first layer with low silicon-based active material content (5 wt% or less) and a second layer with high silicon-based active material content. This segmentation allows the electrode to benefit from high capacity while the first layer buffers volume changes, improving cycle stability.
Solution Approach 2:
Different regions of the negative electrode are assigned different compositions tailored to their specific functions. The first layer near the current collector has low silicon content to provide structural stability and accommodate volume expansion, while the second layer has high silicon content to maximize capacity. This local differentiation resolves the contradiction between energy density and cycle life.
2Quantity of substance
If high silicon-based active material content is used in the negative electrode, then capacity increases, but volume change during charging and discharging becomes more severe, reducing electrode stability
Solution Approach 1:
The negative electrode is segmented into two layers with different silicon-based active material contents. The first layer (low silicon content ≤5 wt%) acts as a stable foundation that minimizes volume change, while the second layer (high silicon content) provides high capacity. This segmentation allows the electrode to achieve high capacity without suffering from severe volume expansion.
Solution Approach 2:
The negative electrode uses a composite structure combining two types of active material layers with different compositions. The first layer uses materials with low silicon content for stability, while the second layer uses materials with high silicon content for capacity. This composite approach enables the electrode to simultaneously achieve both stability and high capacity.
3Ease of manufacture
If a single-layer structure with high silicon content is used, then manufacturing is simple, but the electrode cannot maintain electrical conductivity during volume changes, reducing long-term performance
Solution Approach 1:
The negative electrode is divided into two layers with different silicon-based active material contents. The first layer with low silicon content maintains structural integrity and electrical conductivity during volume changes, while the second layer provides high capacity. This segmentation ensures the electrode maintains conductivity during cycling, improving long-term performance.
Solution Approach 2:
The first layer is specifically designed with low silicon-based active material content (≤5 wt%) to provide a stable, conductive foundation that accommodates volume changes. This local quality enhancement ensures electrical conductivity is maintained during charging and discharging, improving long-term performance.
Data Source
AI summary
A negative electrode for secondary batteries according to an embodiment of the present disclosure may include: a negative electrode current collector; a first negative electrode active material layer formed on at least one surface of the negative electrode current collector and including a first silicon-based negative electrode active material; and a second negative electrode active material layer formed on the first negative electrode active material, including a second silicon-based negative electrode active material, and having a greater thickness than that of the first negative electrode active material layer, wherein the first silicon-based negative electrode active material may be included in a specific content, and the content of the first silicon-based negative electrode material in the first negative electrode active material layer and the content of the second silicon-based negative electrode active material in the second negative electrode active material layer may satisfy specific relationships.