On October 23, 2018, Samsung announced the use of graphene batteries on its official Weibo. The battery is said to fully charge the phone in less than 12 minutes without the need for the most VOOC fast-filled heads on the market. Prior to this, Huawei announced that Huawei's Mate20X uses graphene liquid cooling technology. By carrying a layer of graphene heat-dissipating film, the rapid cooling performance of the mobile phone has been greatly improved. Even if it runs for a long time, it can also make the body. keep cool".
In recent years, mobile phones have become the most important necessities for many people, and why do mobile phone manufacturers favor graphene materials and frequently carry out research around graphene? How far is the mobile phone that really carries the graphene "black technology" away from us?
"Black material" was born "black technology"
Carbon is an important constituent of everything in nature and a major element of living organisms. Graphite and diamond are two typical elemental carbons. They are also the first three-dimensional crystal structures of two carbons known as natural ores.
In the 1980s, nanomaterials and technology were greatly developed. Nano-carbon materials have also entered the historical arena since this period. In 1991, a one-dimensional tubular nanostructure—a carbon nanotube—cured from a graphite layer was discovered. In 2004, graphene appeared in the “family spectrum†of carbon materials. Every new carbon material has not only brought new research directions to the scientific community, but also injected innovation into the industry.
As the name suggests, graphene has a certain relationship with graphite. Take the most common pencil in everyday life as an example. When writing with a pencil, the black handwriting left on the paper contains countless small graphite particles. It is clear under the microscope that these small particles are actually composed of graphite flakes. As the thickness of the sheet is gradually reduced, the graphite will transition to another crystal structure of carbon: graphene. In simple terms, graphene is a single-layer graphite layer that is the basic building block of graphite.
The "black material" graphene born out of black graphite is undoubtedly the most popular "star" in the scientific community in the past ten years, and the "black technology" born from graphene is also endless. We have heard about the concept of “graphene mobile phone†and “graphene battery†more than once. Some of them are merchant hype, and some are genuine new technologies. We can't simply think of graphene as an adjective. In fact, the correct way to interpret these concepts is: "mobile phones with new graphene-related technologies on some components" and "graphene used in a certain structure." Materials to enhance the performance of the battery." In order to allow more readers and consumers to have a correct understanding of “graphene†materials, we will use the part of the mobile phone that may be applied to graphene technology as an example to gradually uncover the mystery of graphene. Veil, to show you the specific technical application that graphene is likely to achieve in the future.
Graphene and lithium ion batteries
The research of lithium-ion battery originated in the 1970s. The early lithium battery used metal lithium as the negative electrode material. Due to some problems in the process of charging and discharging, it could not be completely solved, and its safety and cycle performance have not been satisfactory. Until around 1990, Sony developed a lithium-ion battery with carbon as the negative electrode and lithium reversible insertion or deintercalation. The lithium-ion battery was widely promoted. Lithium-ion batteries are an ideal green power source because of their high energy density, high voltage, small self-discharge effect, excellent cycle performance and environmental friendliness.
Graphite is an excellent anode material for lithium ion batteries. Graphite has good electrical conductivity and high cleanliness. The lamellar structure facilitates the intercalation and deintercalation of lithium, and the potential of lithium atoms remains substantially unchanged after being embedded in graphite. It has been found that when the graphite layers are "spreaded", the graphite changes from a two-dimensional layered structure to a three-dimensional bulk structure. Due to some characteristics of the material structure, the lithium storage capacity is significantly improved, that is, By assembling equal-quality graphene into a more disordered and more "chaotic" structure, the capacity of the lithium-ion battery can be improved, and the cycle stability of the lithium-ion battery can be improved, thereby making the battery life longer.
In addition to being a negative electrode material for lithium ion batteries, graphene can also be added as a conductive filler in the positive electrode material to improve the conductivity and cycle stability of the positive electrode. In general, the application of graphene to lithium ion batteries is an inevitable development trend in the future.
Graphene and flexible display
Graphene has good electrical conductivity, chemical stability and excellent light transmittance. The light transmittance of graphene maintains a uniform distribution throughout the visible spectrum. Compared to the traditional transparent electrode material indium tin oxide, the potential advantage is very significant. On the other hand, since graphene has flexibility, it can be processed onto a flexible touch panel by a transfer method. Graphene, which combines two excellent properties, is undoubtedly a popular candidate for flexible touch displays in the future.
Researchers at the University of Manchester have used graphene films as transparent electrodes in liquid crystal devices and achieved good results. The introduction of graphene into the LED device can improve the light transmission characteristics of the electrode, reduce the resistance, and improve the reliability of the device. Among the OLED devices that are known as the best image quality and highest resolution, due to the high strength, high conductivity, flexible touch and transparency of graphene, related manufacturers are working hard to make OLED and graphene join forces. Show the field to open up new horizons.
Graphene and heat dissipation
The heat dissipation of electronic products is a key factor affecting the power consumption and longevity of electronic products. Electronic devices with poor heat dissipation often have problems in miniaturization and performance, and their reliability is not satisfactory. In the past few generations of smartphones, mobile phone manufacturers mainly use a large metal backplane to limit the maximum operating temperature to achieve temperature control of the mobile phone. However, this is in line with consumers’ pursuit of lightweight and high performance of mobile phones. Running in the opposite direction.
Low-dimensional carbon nanomaterials, such as graphene and carbon nanotubes, have high thermal conductivity and average free path, have high thermal conductivity, and are used as high-efficiency heat-dissipating materials due to their stability at high temperatures. The heat dissipation capacity is four times higher than that of ordinary aluminum alloy.
Graphene and acoustics
Speakers and earphones on mobile phones are sounding devices. Sounding devices are electronic devices that convert electrical signals into acoustic signals. The earliest sounding devices can be traced back to the phonographs invented by Edison in 1877. The existing sounding devices are various, and can be classified into electromagnetic sounding, capacitive sounding, and piezoelectric sounding according to the working principle, and the working essence thereof is to promote the sound of the air fluctuation by the vibration of the film structure.
The diaphragm material of the conventional sounding device is mainly a plastic diaphragm, which has the advantages of high plasticity, easy processing, low cost, but poor rigidity and easy to cause distortion. Carbon materials, including carbon nanotubes, graphene and carbon fibers, are easy to process into a film structure, but also have the characteristics of light weight, good rigidity, small distortion, and large internal resistance. At present, earphones using carbon materials as diaphragms are generally sold at a high price, and are favored in the earphone fever circle. With the continuous decline in the cost of carbon material synthesis in the future, it is highly likely to replace the plastic diaphragm and become the main force in the mass market.
In addition to the traditional vocalization field, carbon materials represented by graphene can be used for thermoelectric sound generation because of their superior thermal properties to plastic materials. Unlike traditional vocalization technology, thermoelectric vocalization works by converting the input alternating current into periodically fluctuating Joule heat, which causes the air to contract and expand to produce sound waves. However, the main bottleneck of this technology is that it has high power consumption and does not have the characteristics of energy saving.
Based on the excellent thermal properties and lightness and flexibility of graphene, graphene can be used to make fully flexible ultra-thin transparent graphene headphones. Compared with the most popular AirPods wireless in-ear headphones, graphene headphones not only have more Good flexibility to fit the ear, but also biocompatible, without any negative impact on the human body. For some specific people who need to wear headphones for work or talk for a long time, or to pursue fashionable urban young people, or even hearing impaired people who need hearing aids, a graphene-based fully flexible headset is of great significance.
Graphene and silicon processors
If the phone is likened to the human body, then the battery is like the human digestive system, responsible for providing energy; the display is like a human appearance; the heat sink is like a person's blood circulation; the acoustic component is like a human sensory system; the processor is quite In the human brain, it is the most core component.
At present, silicon, as the leading material in two major fields of information technology and energy, still plays an irreplaceable role. Integrated circuit chips based on single crystal silicon are the foundation of today's high-tech industry. As Moore's Law no longer applies to the current silicon-based transistor device change, people are looking for new materials that can replace it. As the same element of silicon in the periodic table, carbon has the performance comparable to or better than silicon. The appearance of graphene was once considered as the "savior" in the field of electronic information technology, and it is the continuation of "Moore's Law". Not the only one.
At present, silicon-based processors have reached new heights and process technology has broken through to 7 nanometers. Carbon materials can already be implemented in the laboratory with a 1 nanometer processor. Of course, there is still a long way to go from the lab to the production line, but it is foreseeable that there will be a day when mobile phones are equipped with carbon-based processors.
There is no doubt that these graphene “black technologies†are getting closer and closer to our daily life, and there is so much potential application space on just one smartphone. I believe that in the near future, it will enter our lives and integrate into our lives.
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