Silicon-Carbon Anode Composite With Crosslinked CNT Conductive Network
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries face issues with volume expansion and contraction during charging and discharging, leading to electrical short circuits and reduced lifetime and capacity due to the disappearance of charge transfer pathways and lithium ion trapping.
Innovation Solution
A composite negative electrode active material is developed, comprising a silicon-based core particle with an outer carbon coating layer, first single-walled carbon nanotubes protruding from the coating layer, a conductive structure of second single-walled carbon nanotubes spaced apart, and a crosslinking material that connects the nanotubes, forming a stable conductive network to prevent electrical short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to achieve high capacity, then capacity increases, but volume expansion during charging and discharging causes electrical short circuits and reduced lifetime
Solution Approach 1:
The patent embeds conductive structures (including carbon nanotubes and conductive particles) within and around the silicon-based active material particles. The conductive structures form nested layers and networks that maintain electrical pathways even when the silicon particle volume changes during charging and discharging, preventing electrical short circuits while preserving high capacity
Solution Approach 2:
The patent creates a composite structure combining silicon-based active material with conductive materials (carbon nanotubes, conductive particles, and conductive polymers). This composite approach allows the silicon to provide high capacity while the conductive components maintain stable electrical pathways, resolving the contradiction between high capacity and reliability
2Quantity of substance
If silicon-based negative electrode active material undergoes volume expansion during charging, then capacity is achieved, but charge transfer pathways disappear causing electrical short circuits
Solution Approach 1:
The patent pre-establishes a three-dimensional conductive network around and within the silicon particles before electrochemical cycling begins. This preliminary conductive infrastructure remains intact during volume expansion, preventing electrical short circuits while allowing the silicon to achieve its full capacity potential
Solution Approach 2:
The conductive structures (carbon nanotubes, conductive particles, and polymers) act as intermediaries between the silicon-based active material and the current collector. These intermediary components maintain electrical pathways during volume changes, preventing direct electrical short circuits while allowing charge transfer to continue
3Reliability
If conductive structures are added to prevent electrical short circuits, then lifetime characteristics improve, but device complexity increases
Solution Approach 1:
The conductive structures in the patent serve multiple functions simultaneously: they maintain electrical pathways during volume expansion, provide structural support, facilitate charge transfer, and prevent electrical short circuits. This multi-functionality reduces the need for separate components for each function, thereby limiting the increase in device complexity while achieving improved lifetime characteristics
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 material enhances the lifetime characteristics of the negative electrode and secondary battery by preventing electrical short circuits and maintaining stable electrical contact, even during volume changes, thereby improving capacity retention and resistance.
Implementation Method 1
a crosslinking material bonded to the first single-walled carbon nanotube and at least one of the second single-walled carbon nanotubes, wherein the at least one of the second single-walled carbon nanotubes is crosslinked with the first single-walled carbon nanotube by the crosslinking material
Implementation Method 2
first single-walled carbon nanotubes in contact with the outer carbon coating layer, wherein the first single-walled carbon nanotubes protrude from the outer carbon coating layer; a conductive structure spaced apart from the outer carbon coating layer, wherein the conductive structure includes at least one second single-walled carbon nanotubes
Data Source
AI summary
A composite negative electrode active material, which includes: a silicon-based core particle; an outer carbon coating layer positioned on a surface of the silicon-based core particle; first single-walled carbon nanotubes in contact with the outer carbon coating layer, wherein the first single-walled carbon nanotubes protrude from the outer carbon coating layer; a conductive structure spaced apart from the outer carbon coating layer, wherein the conductive structure includes at least one second single-walled carbon nanotubes; and a crosslinking material bonded to the first single-walled carbon nanotube and at least one of the second single-walled carbon nanotubes. The at least one of the second single-walled carbon nanotubes is crosslinked with the first single-walled carbon nanotube by the crosslinking material, and wherein the conductive structure and the first single-walled carbon nanotube are connected to each other.