Silicon Anode CNT Bundle Structure for Conductivity and Cycle Life
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Solution Overview
Problem
Conventional lithium secondary batteries using silicon-based active materials face challenges in maintaining conductivity and life characteristics due to the breakage of single-walled carbon nanotubes from volume expansion and contraction, leading to degraded battery performance.
Innovation Solution
A negative electrode with a carbon nanotube structure formed by bonding 2 to 5,000 single-walled carbon nanotube units side by side, integrated into the negative electrode active material layer using a specific dispersion method with a homogenizer, maintains conductivity and prevents breakage during volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-walled carbon nanotubes are used as conductive agent to improve conductivity, then battery capacity is improved, but the carbon nanotubes break due to volume expansion and contraction of silicon-based active material, degrading battery life
Solution Approach 1:
The patent divides the single-walled carbon nanotubes into bundles of 2 to 5,000 units bonded side by side. This segmentation creates a more robust structure where individual nanotube breakage does not compromise the entire conductive network, as the bundled structure provides redundancy and maintains conductivity pathways even when some units break during silicon-based active material volume changes.
2Quantity of substance
If silicon-based active material is used to improve battery capacity, then energy density increases, but excessive volume expansion occurs during charge and discharge, causing conductive network breakage
Solution Approach 1:
The patent changes the structural parameter of the conductive agent from individual single-walled carbon nanotubes to bundled structures comprising 2 to 5,000 units bonded side by side. This parameter change increases the mechanical strength and volume tolerance of the conductive network, enabling it to withstand the excessive volume expansion of silicon-based active material during battery operation while maintaining electrical conductivity.
3Ease of operation
If conventional dispersion methods are used to prepare conductive agent dispersion, then single-walled carbon nanotubes are completely dispersed, but the resulting conductive network is blocked or reduced during battery operation
Solution Approach 1:
The patent creates a composite conductive structure by bonding multiple single-walled carbon nanotube units (2 to 5,000 units) side by side to form bundled structures. This composite approach combines the dispersibility advantages of individual nanotubes with the mechanical robustness of bundled structures, maintaining both ease of dispersion during manufacturing and reliability of the conductive network during battery operation.
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 carbon nanotube structure forms a robust network that withstands excessive volume changes, enhancing battery capacity and life characteristics by maintaining conductivity and preventing cracks in the electrode.
Implementation Method 1
dispersing the bundle-type single-walled carbon nanotubes by applying a shear force to the mixed solution by a homogenizer
Implementation Method 2
the carbon nanotube structure in which 2 to 5,000 single-walled carbon nanotube units are bonded side by side, maintains conductivity and prevents breakage during volume changes
Data Source
AI summary
A negative electrode includes a negative electrode active material layer, wherein the negative electrode active material layer includes a negative electrode active material and a conductive agent, wherein the negative electrode active material includes a silicon-based active material, the silicon-based active material includes SiOx(0≤x<2), the conductive agent includes a carbon nanotube structure in which 2 to 5,000 single-walled carbon nanotube units are bonded side by side, and the carbon nanotube structure is included in an amount of 0.01 wt % to 1.0 wt % in the negative electrode active material layer. A secondary battery including the negative electrode, and a method of preparing same are also provided.