In 2017, the lithium battery industry will continue to heat up, and what are the most popular lithium battery materials? This article is dedicated to the inventory of the most popular lithium battery materials in 2017, as follows:
1, graphene
In the past two years, graphene-related "industry" is also in full swing in China. The application of graphene in the lithium battery industry has attracted much attention. What is graphene? Graphene is a planar film made of carbon atoms with sp2 hybrid orbital into a hexagonal honeycomb lattice, with a two-dimensional material with a carbon atom thickness. Graphene is currently the thinnest but hardest nanomaterial in the world. It is almost completely transparent and absorbs only 2.3% of light; the thermal conductivity is as high as 5300W/m ̇K, higher than that of carbon nanotubes and diamond, and its electron mobility exceeds at room temperature. 15000cm2/V ̇s, which is higher than carbon nanotubes or silicon crystals, and has a resistivity of only about 10-8 俜m, which is lower than copper or silver, and is the material with the lowest resistivity in the world.
Graphene mainly has the following production methods: mechanical stripping, chemical vapor deposition (CVD), oxidation-reduction, solvent stripping, solvothermal, high temperature reduction, photoreduction, epitaxial crystal growth, microwave, arc Law, electrochemical method, etc.
The current term "graphene battery" is very hot. At present, almost all commercial lithium-ion batteries use graphite-based anode materials. Previously, Huawei announced a major research breakthrough in the field of lithium-ion batteries, the industry's first high-temperature long-life graphene-based lithium-ion battery. The experimental results show that the new high temperature resistant technology based on graphene can increase the upper limit temperature of lithium ion battery by 10 and the service life is twice that of ordinary lithium ion battery. It is foreseeable that graphene will remain a hot material in the lithium battery industry in 2017.
2, silicon negative
With the rapid development of electronic technology and the rapid spread of electric vehicles , the demand for high-energy lithium-ion batteries is becoming more and more intense, while the traditional graphite material has a theoretical specific capacity of only 372 mAh/g, which is far from satisfying the high ratio. The demand for lithium-ion batteries, under the stimulation of huge market demand, various new anode materials have begun to appear, such as silicon-based anode materials, tin-based anode materials, nitrogen-doped porous graphite materials and transition metal sulfide anodes ( For example, MoS2), among the many new anode materials, the current technology is relatively mature silicon-based anode materials, and has now achieved small-scale commercial applications.
In fact, high voltage, polymer, silicon negative electrode are all lithium batteries , silicon negative electrode is just a new technology, most of the current lithium batteries are based on carbon-based materials, but due to this carbon-based The reversible capacity of the negative electrode of the material is only 372 mAh / g, which severely limits the development of lithium ion batteries in the future, so it is necessary to develop the next generation lithium ion battery anode material. In the course of the research, the researchers found that a silicon element (Li22Si5) has a capacity of 4200 mAh/g, which is an excellent material for developing high-capacity batteries. Moreover, the battery made of such a negative electrode material has almost no capacity attenuation during use, and is more beneficial to improve the service life of the battery. In addition, silicon is abundant in reserves and low in cost on the earth, so it is a very promising negative electrode material for lithium ion batteries.
3, aluminum foil coated carbon
Carbon coated aluminum foil is a new type of battery cathode substrate. Compared with traditional aluminum foil, carbon coated aluminum foil has the advantages of good electrical conductivity, small internal resistance, strong mechanical properties and good toughness, which can avoid short circuit caused by burrs and improve adhesion of electrode materials. Large battery discharge capacity and extended lithium ion battery life.
Xuefeng Tong and others of the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences have developed a dual-ion battery based on a carbon-coated aluminum foil negative electrode, in which the aluminum foil is used not only as a current collector but also as a negative electrode material. Compared with graphite materials, Al has a higher theoretical specific capacity. When forming a LiAl structure, the specific capacity can reach 993 mAh/g. When Li9Al4 is formed, the specific capacity reaches 2235 mAh/g, and the voltage platform is only 0.19-0.45 V vs. Li+/Li has a smaller volume expansion than silicon material. When Li9Al4 is formed, the volume expansion is only 97%, and the Al material also has good electrical conductivity, easy processing and low cost, but the Al negative electrode is currently There is still a need to increase its cycle life.
The preparation process of carbon coated porous aluminum anode is relatively simple. Firstly, the aluminum foil is treated by electrolysis, and then a layer of PAN material is coated on the surface. After low temperature curing and high temperature carbonization, a layer can be formed on the aluminum foil. The carbon layer can repeat the PAN treatment process to increase the carbon content. The study found that the carbon content of the primary carbon coating is about 1.5%, the carbon content of the two carbon coatings is about 2.8%, and the carbon content of the three carbon coatings is about 4. %.
4, ceramic mixed rubber diaphragm
Since the material of the lithium battery is an important factor affecting its safety performance, in order to ensure the safety of the lithium battery, the selection of a safer diaphragm has become one of the considerations of many enterprises.
Ceramic diaphragms are coated with nanoscale ceramic particles on a separator. Its role is mainly to improve the heat shrinkage of the diaphragm and prevent the membrane from shrinking and causing a large area short circuit. In addition, the thermal conductivity of the ceramic is low, preventing some thermal runaway points in the battery from expanding to form an overall thermal runaway. Generally, it can withstand high temperatures at around 200 °C. The market for ceramic coating is mainly high voltage batteries and power batteries. There are two development directions: one is coated with alumina, LG is used for representative, and dip-coated; the other is a layer of aramid on the surface, represented by Japanese Teijin.
In the future, ceramic separators will have a wide range of applications. It is an important means to solve the safety problem of lithium batteries , and is also a direction for the development of lithium battery separators in the future.
5, aramid coated diaphragm
With the promotion of lithium batteries in energy storage, new energy vehicles, and electric bicycles, the diaphragm market has grown rapidly, and the penetration of ternary materials has increased the demand for ceramic coated diaphragms. For the separator, whether it is a high-temperature resin such as PI, TPX or aramid, or a non-woven fabric and a paper separator, the electrospinning technology will replace the existing diaphragm technology. The aramid coated diaphragm absorbs liquid and has strong liquid retention performance. It can increase the capacity and be thinner and lighter. Under the premise of not affecting safety, it can be made thinner and lighter to meet the compact and miniature high-capacity battery. A new material diaphragm with stronger ionic conductivity. In addition, the aramid coated diaphragm solves the problem of no deformation at high temperature, avoids the occurrence of short circuit, low self-discharge, can reduce the capacity loss caused by micro short circuit, high rate performance, electrolyte wetting performance, and improved cycle performance.
6, CNT
The full name of CNT in English is Carbon Nanotube. The Chinese name is carbon nanotubes, which, like diamond, graphite, and fullerenes, is an allotrope of carbon. It is a tubular carbon molecule in which each carbon atom on the tube is sp2 hybridized and bonded to each other by a carbon-carbon sigma bond to form a hexagonal honeycomb structure as a skeleton of the carbon nanotube.
Carbon nanotubes were discovered in January 1991 by a physicist from the NEC laboratory in Tsukuba, Japan, using high-resolution transmission electron microscopy from carbon fiber produced by the arc method. It is a tubular carbon molecule in which each carbon atom on the tube is sp2 hybridized and bonded to each other by a carbon-carbon sigma bond to form a hexagonal honeycomb structure as a skeleton of the carbon nanotube. A pair of p electrons that do not participate in hybridization on each carbon atom form a conjugated π electron cloud across the entire carbon nanotube. According to the number of layers of the tube, it is divided into single-walled carbon nanotubes and multi-walled carbon nanotubes. The radial direction of the tube is very thin, only the nanometer scale, tens of thousands of carbon nanotubes together and only one hair is wide, and the name of the carbon nanotubes comes from it. In the axial direction, it can be as long as several tens to hundreds of micrometers.
As a high-quality nano material, since the structure of carbon nanotubes is the same as that of graphite, it has good electrical properties. Carbon nanotubes have extraordinary strength, thermal conductivity, and magnetic reluctance, and their properties change with the structure, from insulator to semiconductor, from semiconductor to metal; the magnetic flux of metal-conducting carbon nanotubes is quantum. In fact, it shows the Akhanov-Bohm effect (AB effect).
7, high voltage positive
The research and development of lithium battery cathode materials has always been one of the most important areas of lithium battery research. How to develop lithium battery cathode materials is also a topic of great concern to everyone. To increase the energy density, there are two main ways to increase the electrode material capacity or increase the battery operating voltage. If you can combine high voltage and high capacity, it would be better. In fact, this is the mainstream of the current development of lithium battery cathode materials, such as high voltage high pressure lithium cobalt oxide, high voltage ternary materials, etc. .
8, NCA
The ternary material is lithium nickel cobalt manganese oxide Li(NiCoMn)O2, a ternary composite positive electrode material precursor product, which is made of nickel salt, cobalt salt and manganese salt. The ratio of nickel cobalt to manganese can be adjusted according to actual needs. The battery in which the element material is used as the positive electrode is safer than the lithium cobaltate battery .
At present, more and more electric logistics vehicles use ternary material batteries, mainly due to the ternary cathode material NCA.
It has the advantages of high energy density, long cycle life, low cost, and light weight of the whole vehicle, which can effectively solve the "last mile" problem of urban logistics, and thus trigger the transformation of electric logistics vehicles from lithium iron phosphate to ternary technology. the trend of.
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