Development of carbon nanotubes and their application in lithium anode

Carbon nanotube, also known as bucky tube, is a kind of one-dimensional carbon nanomaterial with special structure.  The nanotubes themselves are round tubes, similar to the structure of graphene sheets curled up.  Carbon nanotubes (CNTS) have been widely applied in many fields due to their excellent mechanical, electrical, thermal and optical properties.

01 Discovery and development of carbon nanotubes

Carbon nanotubes discovered for the first time in Japan.  In 1991, electron microscopist Lijima at NEC's Basic Research Laboratory in Japan accidentally discovered carbon molecules made of tube-like coaxial nanotubes while examining globular carbon molecules produced in a graphite arc device under a high-resolution transmission electron microscope.  These are Carbon nanotubes, now known as Carbon nanotubes.  

When carbon nanotubes were discovered, they aroused great interest among researchers and have been continuously studied and developed in the following decades.  

In 1993, S. Lijima et al and D. S. Bethune et al reported that carbon nanotubes with only one layer of tube wall can be obtained by adding certain catalyst to graphite electrode by using arc method, namely single-wall carbon nanotubes products.  

In 1996, Showa Denko of Japan built the world's first commercial production of carbon nanotubes factory in Kawasaki, with an annual capacity of 20 tons, marking the beginning of commercial production of carbon nanotubes.  

In 1997, A. C. Dillon et al reported the storage and stabilization of hydrogen molecules in the hollow tubes of single-walled carbon nanotubes, which attracted wide attention.  Related experimental studies and theoretical calculations have also been carried out.  It is speculated that the hydrogen storage capacity of single-walled carbon nanotubes can reach 10% (mass ratio).  In addition, carbon nanotubes could be used to store other gases, such as methane.  

In 2003, Japan'S CNRI company successfully developed carbon nanotubes with a diameter of 0.4nm, making carbon nanotubes developed to the ultra-fine degree.  That same year, Mexican researchers found carbon nanotubes in crude oil samples taken from an oil field in southeastern Mexico.  This is the world's first discovery of natural carbon nanotubes in crude oil.  

In 2007, Japan developed the first technology to directly synthesize a large number of single-layer carbon nanotubes on a large metal plate. 

 

In 2010, researchers from Zhejiang University and university of California, USA successfully synthesized fullerene C90 with the smallest carbon nanotube structure in the world.  

In 2014, researchers at the National Institute of Standards and Technology (NIST) developed a uniform, multi-walled carbon nanotubule-based coating that reduces the flammability of commonly used foam interiors.  Tsinghua University has successfully developed high-performance carbon nanotube wires.  

In 2015, US researchers dramatically increased the processing speed of computer chips by using carbon nanotubes instead of silicon, potentially making 3D chips 1,000 times faster than current chips.  

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Carbon nanotubes, known as "black gold", have been predicted to be one of the wonder materials that will "revolutionise the 21st century".  Carbon nanotubes, known as "universal substrate" for their excellent mechanical, electrical and thermal properties, have great application prospects in structure-function integrated composite materials, battery electrodes, integrated circuits, sensors, electric heaters and other fields.  In the future, it may be extended to conductive plastics, semiconductor devices, lightweight high-strength composite materials, broadband lightweight electromagnetic shielding, impact protection, intelligent devices and other fields, and is expected to bring revolutionary development to these fields.

02 Application of carbon nanotubes in lithium anode

Since the discovery of carbon nanotubes, as a kind of tubular carbon material with one-dimensional nanometer size, it has been applied in many fields with its unique characteristics.  Lithium ion battery is one of the potential applications of carbon nanotubes.  Carbon nanotubes can be directly used as anode materials for lithium-ion batteries.  

Carbon nanotube anode materials are characterized by high battery power and difficulty in crushing.  Their morphology allows them to replace graphite as a cathode material for commercial lithium-ion batteries.  Carbon nanotubes are made up of single or multiple layers of coaxial carbon sheets that "have a graphite-like layer structure".  The sp2 hybrid structure and high aspect ratio of carbon nanotubes bring a series of excellent properties.  This microstructure makes the embedment depth of lithium ion small, short stroke and many embedment positions (cracks and holes in tube and between layers, etc.). Meanwhile, carbon nanotubes have good conductivity and good electron conduction and ion transport capacity, so they are suitable for anode materials of lithium ion batteries.  

The use of carbon nanotubes as anode materials for lithium ion batteries also has disadvantages. First, the irreversible capacity of the first charge and discharge is large, and the efficiency of the first charge and discharge is relatively low.  Second, the cathode of carbon nanotubes lacks stable voltage platform.  Third, potential hysteresis exists in carbon nanotubes.  These problems restrict the application of carbon nanotubes as anode materials for lithium ion batteries.  

At present, the research of carbon nanotubes mainly focuses on the preparation and electrochemical properties of composites, such as the composite of carbon nanotubes with silicon and metal oxides, etc.  In addition, as a new material, carbon nanotubes have many requirements for qualified production, such as diameter, layer number, length, defect degree and electronic characteristics, etc., which are important factors, and their production methods also need to be further improved.  

Carbon nanotubes in li-ion battery cathode large-scale commercial and a certain distance, however, with the deepening of the carbon nanotubes research, especially in the mechanism of carbon nanotubes research and preparation process of ascension, would prompt carbon nanotubes are closer to the business category and its application in the field of lithium ion battery will further expand.