Composite Negative Electrode Plate for Silicon Expansion Control
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Solution Overview
Problem
The existing secondary batteries using graphite as negative electrode active material face limitations in energy density and cycle life due to the low theoretical lithium intercalation capacity and volume expansion issues with silicon-based materials, which lead to reduced stability and performance.
Innovation Solution
A secondary battery design featuring a composite current collector with a silicon-based active material layer, where the content and brittleness parameter of the current collector are optimized to enhance structural strength, processability, and stability, combined with a protective layer to prevent damage during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used as negative electrode active material to increase theoretical capacity, then energy density is improved, but volume expansion occurs during cycling which reduces cycle performance
Solution Approach 1:
The silicon-based active material is embedded within a three-dimensional porous conductive skeleton structure, creating a nested configuration where the active material is contained within the porous framework. This nesting approach allows the silicon material to expand and contract within the porous structure during cycling, preventing pulverization while maintaining high capacity
Solution Approach 2:
The three-dimensional porous conductive skeleton acts as a flexible buffer structure that can accommodate volume changes of the silicon-based material. The porous framework provides mechanical flexibility and structural integrity, allowing the silicon particles to expand during lithiation without causing catastrophic failure of the electrode structure
2Quantity of substance
If silicon-based materials are used as negative electrode active material to achieve high energy density, then capacity is improved, but pulverization and exfoliation of active material occurs which reduces stability
Solution Approach 1:
The conductive skeleton is designed with locally optimized porous structures that provide different mechanical properties in different regions. The three-dimensional porous network creates localized stress distribution patterns that prevent concentration of mechanical stresses, thereby preventing exfoliation and maintaining structural stability during repeated cycling
Solution Approach 2:
The electrode is constructed as a composite structure combining silicon-based active material with a three-dimensional porous conductive skeleton. This composite architecture integrates the high capacity advantage of silicon with the structural stability and conductivity of the porous skeleton, achieving both high capacity and structural integrity
3Reliability
If traditional graphite is used as negative electrode active material to ensure structural stability, then cycle performance is maintained, but theoretical lithium intercalation capacity is limited to 372 mAh/g
Solution Approach 1:
The invention changes the fundamental parameter of theoretical capacity by replacing graphite with silicon-based materials, achieving a significant increase from 372 mAh/g to over 4000 mAh/g. The porous skeleton structure enables this parameter change to be realized without suffering from the typical volume expansion problems of silicon
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 improves the cycle performance and energy density of the battery by reducing volume expansion and maintaining high structural integrity, thereby extending the battery's lifespan and reliability.
Implementation Method 1
the silicon-based materials will cause a huge volume expansion (about 400%) during cycling process
Implementation Method 2
the theoretical lithium intercalation capacity of graphite itself is relatively low, only 372 mAh/g
Data Source
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AI summary
This application relates to a negative electrode plate, a secondary battery and apparatus thereof. The secondary battery of the present application comprises a negative electrode plate (30), the negative electrode plate (30) comprises a composite current collector (10) and a negative electrode active material layer (20) disposed on at least one surface of the composite current collector (10), the negative electrode active material layer (20) comprises a silicon-based active material, the silicon-based active material accounts for 0.5 wt% to 50 wt% of total mass of the negative electrode active material layer (20), and the composite current collector (10) comprises a polymer support layer (101) and a metal conductive layer (102) disposed on at least one surface of the polymer support layer (101), and the composite current collector (10) has a brittleness parameter C ranging from 0.03 to 0.5. The secondary battery and the negative electrode plate (30) of the present application achieve good coordination between the current collector (10) and the negative electrode active material layer (20), which improves the pulverization and exfoliation problem of the silicon-based negative electrode plate (30) during charging and discharging, thereby obtaining relatively high weight energy density and meanwhile improving cycle life of the secondary battery.