Is it possible to quickly charge without deteriorating battery performance?


 

The next day I forgot to charge my smartphone while I was sleeping, the quick charging became very desperate. By the way, did you know that frequent quick charging decreases battery performance?


What is rapid charging?


​Sometimes I see the phrase 10 minutes to quickly charge my smartphone on the street. Quick charging can cut the time it normally takes to charge by more than half. In the case of electric vehicles, it takes 6 hours to charge slowly, but a technology that can quickly charge in about 30 minutes is emerging.


Quick charging is a method of charging by passing a larger current than the standard current. In other words, it allows more current to flow and fills up quickly. Most smartphone fast charging technologies currently on the market use a method of charging by increasing the charging voltage from 5V to 9V. Quick charging has the advantage of being able to recharge quickly, but it also has the disadvantage that it puts a strain on the performance of the battery.


Battery fire or rapid charging?


​At present, the lithium-ion battery is the most widely used battery for smartphones, electric vehicles, and ESSs. Lithium-ion batteries are charged by storing lithium ions in the positive electrode (+) and moving to the negative electrode (-) through the electrolyte, and generating energy by moving the lithium ions stored in the negative electrode to the positive electrode. During charging, the faster lithium ions move to the negative electrode and are stored, the shorter the charging time. In this process, graphite, which has a small change in crystal structure, is mainly applied as a negative electrode material.


However, in the case of existing lithium-ion batteries, when rapidly charged, there is a high possibility that lithium will precipitate on the surface of the negative electrode made of graphite. Deposition means that lithium ions dissolved in a liquid cannot be inserted into the graphite crystal due to an electrochemical reduction reaction and change back to a lithium solid on the graphite surface. If you charge or overcharge at low temperatures, this is most likely to happen.


​When lithium is deposited in this way, the separation membrane physically preventing the anode and the cathode from meeting is pierced, and there is a problem of ignition when a short occurs inside. This is why it is said that it is better not to charge quickly unless it is in a hurry.


Scientists' efforts for a better future!


​A quick charge can cause the above problems, so we are experiencing the inconvenience of charging our smartphones during a long period of sleep. If you solve these problems, you will be able to live a more convenient electric life. Especially in the case of electric cars, if they can be charged as fast as the gasoline car's fueling speed, it will become a more popular means of transportation.


​What are many scientists working on for a better future?


In order to solve the problem, methods such as changing the charging protocol from the constant current charging method to the pulse charging method or designing with a slightly lowered electrode density have been carried out. However, it is important to have a high energy density in order to have a small size and high capacity, and there was no material technology capable of charging rapidly while having a high energy density.


Then, the Korea Electrotechnical Research Institute (KERI), a government-funded research institute under the Ministry of Science and ICT, recently developed a technology that has high energy density and does not affect the life or safety of the battery even if it is rapidly charged. It is also getting a lot of attention, such as being published in the international academic journal Nature Communications. It is a technology that improves performance by coating a metal phosphide catalyst on the surface of graphite particles. In particular, the application of this technology reduces the possibility of lithium precipitation during rapid charging, which can significantly reduce the possibility of ignition of the battery.


What kind of future will unfold in the future?


Starting from Japan's export regulations in July 2019, it became important to become independent of the subsidiary (materials, parts, equipment). If this technology is transferred to a domestic secondary battery material company or manufacturer, it is expected to lead to an effect that can replace artificial graphite materials that have been imported depending on Japan or China.


In addition, the reason why many people hesitate to purchase electric vehicles is probably due to charging problems and the risk of fire. If a gasoline car can be charged as quickly as refueling, the popularization of electric cars will be a matter of time. If this technology is applied, it is expected that the charging time of electric vehicles can be reduced to 10 minutes. You can also expect safety by reducing the risk of fire from the battery.

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