Composite Silicon Negative Electrode for Lithium-Ion Battery Stability
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Solution Overview
Problem
Conventional silicon-based negative electrode active materials in lithium-ion batteries suffer from high volume expansion during charging and discharging, leading to cracks and deterioration of cycle lifespan characteristics, making it challenging to manufacture batteries with long lifespan and high capacity.
Innovation Solution
A composite negative electrode active material is developed with a core capable of intercalating lithium ions, featuring multiple silicon coating layers of different densities, including high-density and low-density Si layers alternately formed on the surface, which helps absorb volume expansion and prevent cracks, along with an optional carbon coating layer for enhanced electronic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-based negative electrode active material is used to achieve high capacity, then the battery capacity increases significantly, but the volume expansion during charging and discharging causes cracks and deteriorates cycle lifespan characteristics
Solution Approach 1:
The silicon coating layer is divided into multiple sub-layers with different densities (high-density Si layer and low-density Si layer) instead of using a single uniform layer. This segmentation allows each sub-layer to perform specific functions: the high-density layer provides structural integrity while the low-density layer accommodates volume expansion, thereby preventing cracks and improving cycle lifespan while maintaining high capacity
Solution Approach 2:
A composite coating structure is created by combining silicon layers of different densities with a carbon-based core material. This composite structure integrates the high capacity advantage of silicon with the structural stability of carbon, enabling the negative electrode to achieve both high capacity retention and improved cycle lifespan characteristics
2Quantity of substance
If a single-layer silicon coating is applied to increase capacity, then the discharge efficiency improves, but the high-volume expansion rate causes deformation and cracks during cycling
Solution Approach 1:
Different regions of the coating layer are assigned different densities and properties: the high-density Si layer provides structural rigidity and maintains local integrity, while the low-density Si layer provides flexibility to accommodate local volume changes. This local differentiation of properties allows the coating to simultaneously achieve high discharge efficiency and physical stability
Solution Approach 2:
The low-density Si layer is positioned between the core material and the high-density Si layer to act as a cushioning layer that absorbs and distributes the stress from volume expansion before it reaches the outer high-density layer. This beforehand cushioning prevents crack formation and maintains structural integrity during charging and discharging cycles
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 composite negative electrode active material significantly improves the physical stability and cycle lifespan characteristics of lithium-ion batteries by reducing crack formation and maintaining high capacity, as demonstrated by enhanced capacity retention and reduced electrode thickness variation during repeated charging and discharging cycles.
Implementation Method 1
a core capable of intercalating and deintercalating lithium ions
Implementation Method 2
two or more silicon (Si) layers having different densities formed on a surface of the core... helps absorb volume expansion and prevent cracks
Data Source
AI summary
The present invention relates to a negative electrode active material, a method of preparing the same, and a lithium secondary battery including the same. In particular, the present invention relates to a composite negative electrode active material that includes: a core capable of intercalating and deintercalating lithium ions; and a plurality of coating layers comprising two or more Si layers having different densities formed on a surface of the core, and thus has enhanced stability by minimizing the formation of cracks occurring by the repetition of charging and discharging, a method of preparing the same, and a lithium secondary battery including the same and thus exhibiting enhanced lifespan characteristics.