Li-ion (Lithium-ion) is a battery technology that is commonly used on most rechargeable mobile devices such as phones, laptops, smart watches … until the vehicle runs. electricity. Although possessing many advantages such as low production costs, high energy storage, multiple discharge times, but Li-ion batteries have a high risk of fire and explosion as well as concerns of environmental pollution, mainly coming from chemical activities for making batteries. Therefore, leading experts are still looking for replacement materials that make the battery safer, more efficient, and cheaper.
Basically all chemical batteries are made of basic components including 2 electrodes and electrolytes. In a Li-ion battery, the anode is made of common Lithium (Li +) compounds. Lithium Cobalt Oxide (LiCoO2) or Lithium Iron Phosphate (LiFePO4) and cathode are usually made of graphite (Graphite). The electrolyte is of various types depending on the type of battery, such as a Li-Po battery (Lithium-Ion Polymer) using a flexible polymer electrolyte instead of a liquid like regular Li-ion. This electric layer is like thin flexible plastic sheets placed between anode and minus, so the Li-Po battery has a great advantage that it is easy to design thin, bend and compact for use on a variety of small devices.
So how does the Lithium-ion battery work?
Li + has 1 electron in the outer layer and it tends to give away this electron, because of this characteristic Lithium is a highly activated metal, released into water that reacts immediately or even in the air. And for Lithium to be more stable, Lithium batteries are used in Lithium batteries as mentioned above as LiCoO2 or LiFeO4. In a Lithium battery cell, an electrolyte is used to only let Li + ions pass and prevent electrons. When the battery is charged, the voltage causes Lithium's electrons to separate from the anode, passing the external circuit to the cathode while the Li + ions pass through the electrolyte to the cathode. The cathode is made of graphite with a multi-layer structure, the chemical bond is quite loose, so Li + and electrons can easily stick and save. When Li + and electron ions cling to the cathode, the battery is fully charged, the rest of the anode is the oxide structure and the lack of Li + ions makes the structure unstable.
When discharging, for example, if you get a light bulb connected to the two battery ends for easy visualization, the Li + ion wants to return to its original stable state. So the Li + ion moves from the cathode back to the anode through the electrolyte and to balance the charge, the electrons also move along, but instead of going through the electrolyte, they pass through the wire, brightening the light bulb. and return to the positive. The fact that the two electrodes of the battery also has a separating membrane (separator) to prevent the electrolyte from drying out, the diaphragm will not allow electrons to pass through to avoid short circuit causing explosion of batteries. .
Li-ion batteries can be recharged multiple times with less wear and tear and high energy density, but when heated, components inside the Li-ion battery expand more than other battery technologies. . Because the Li-ion battery is always closed, it is subject to expansion pressure. Looking back at the Galaxy Note 7 battery explosion, Samsung tried to design a slim battery for this device while increasing the energy density. Consequently, internal electrodes and insulation do not have enough safety gaps. Each charge, the battery expands a little and the internal electrodes are bent causing short circuits due to contact with each other. In addition, Li-ion batteries can also explode because of external influences, such as close contact with heat, shock due to physical breakage, which damage the separating membranes; overcharge …
Another drawback of Li-ion batteries is environmental pollution. As mentioned above, Li-ion batteries are considered as an environmentally friendly energy source, used for everything from phones to electric vehicles, but chemical extraction such as Lithium and graphite makes Li-ion batteries No longer environmentally friendly. Under the explosion of electric vehicles, Cairn Energy Research Advisors' research projects believe that Lithium industry will grow nearly 8 times in the next decade and the price of this material has also increased. double from 2016 to 2018.
Mining chemicals such as lithium, graphite as well as minerals for Li-ion battery production are polluting water, air and soil. So the Li-ion battery itself is causing real environmental risks. This status can only be improved if technology changes. Here are a few potential alternatives to compounds being used in Li-ion batteries:
Sodium is abundant in seawater, almost an endless resource and does not require a lot of extraction and extraction. The problem is that you are not simply replacing Lithium with sodium. Sodium has a larger ion size than Lithium so it cannot lie between layers in the carbon network of cathodes which are made of graphite. Also sodium has a lower energy density than Lithium. However, researchers at Birmingham University have solved this problem by replacing phosphorus (Phosphorous) for graphite at the cathode and the ability to carry charged particles is 7 times more than graphite with the same volume.
Fluoride batteries are 8 times more durable than Lithium batteries, but it is easy to say, difficult because Fluoride is an anion (F-) – a negatively charged ion, which provides a high energy density but negative charge is also The reason it reacts and is difficult to stabilize. Last December, a group of researchers from Caltech, JPL, Lawrence Berkeley National Laboratory and Honda Research Institute created a liquid electrolyte named bis (2,2,2-trifluoroethyl). ether (BTFE) and it has been able to stabilize fluoride and cause fluoride to function normally at room temperature.
Magnesium is not only more popular than Lithium but it does not cause dendrit – thin conductive fibers that form inside Lithium batteries cause battery cells to reduce their lifespan and cause short-circuit, explosion of batteries. For decades, magnesium batteries have not been comparable to Lithium batteries in terms of capacity and energy storage. But at the end of last year, researchers from the University of Houston and Toyota's research institute discovered chloride (chloride) – the chemical commonly used as an electrolyte in magnesium batteries is the cause of the effect. battery capacity. They replaced it with a non-chloride electrolyte, cathode made of organic polymer and magnesium anodes, so they had an unprecedented battery density, power and stability. This old magnesium battery.
Aluminum batteries are considered safer, more environmentally friendly than Li-ion batteries with aluminum anodes and graphite cathodes. Much research has been done to turn aluminum batteries into a perfect alternative to Lithium batteries, such as scientists at Victoria University, Wellington and Clermont-Ferrand National School of Chemistry, France. A new electrolyte that is considered the key to aluminum batteries can be easily fabricated, low cost and better performance than Lithium batteries.
Meanwhile, researchers at ETH Zurich and Empa, Switzerland used titanium nitride – a ceramic material with a high conductivity as a conductor covering the aluminum anodes from which to resist corrosion of the electrolyte for a long time. As an alternative to graphite as an energy storage medium at cathode, researchers in Switzerland found a new hydrocarbon-based material called polypyrene. Polypyrene has a chain structure with large spaces between molecular chains that can contain a lot of ions.
Although not a complete replacement for Lithium, researchers at the University of Texas have sought to make Lithium batteries more efficient and safe for the environment. According to them, Lithium-sulfur batteries (Li-S batteries) are cheaper, lighter, and double the energy density of traditional Lithium-ion batteries, but sulfur has poor electrical conductivity, the electrode is saved. Fluorescent easily during charging. From there, they sought to reinforce sulfur by adding molybdenum to sulfur, resulting in the sulfur electrode becoming better and more stable.
Researchers at Central Florida University are seeking to develop batteries that use sulfide electrodes instead of graphite in Lithium batteries. The cathode of this type of battery is made of nickel sulfide (nickel sulfide – NiS) and iron sulfide (FeS2), combined with the properties of both, the electrode has better conductivity, stable temperature. High and low fabrication costs. Combined with Lithium, the battery will be much more durable, namely the discharge cycle can be up to 1000 times without wear and tear.