Why is lithium battery a new energy source?

As we all know, the advantage of new energy vehicles is that they are more carbon-efficient than gasoline-fueled vehicles. It uses unconventional vehicle fuel as a power source, such as lithium batteries, hydrogen fuel, and so on. Lithium batteries are also widely used in applications other than new energy vehicles, mobile phones, notebook computers, tablet computers, mobile power supplies, electric bicycles, power tools, and so on.mobile power plant

At present, lithium batteries are used by both the world-renowned Tesla and the well-known mainstream new energy vehicles in China. Lithium batteries used by these new energy vehicle manufacturers can be classified into lithium iron phosphate batteries, ternary lithium batteries (including NCA and NCM), lithium manganate batteries, lithium cobalt oxide batteries, nickel hydrogen batteries, and titanic acid. Lithium battery, etc. Among them, Tesla, Beiqi E200/150, GAC Chuanqi GA5EV, Beijing Benz, Brilliance BMW 5 Series, Weilai Automobile, etc. are all ternary lithium batteries. BYD, which used lithium iron phosphate batteries, also turned to the ternary lithium battery camp.


However, whether it is a ternary lithium battery or a lithium iron phosphate battery, it is impossible to avoid the hidden dangers of inflammable and explosive.


Lithium is the most active metal in the world. Because its chemical properties are too active, when lithium metal is exposed to the air, it will react intensely with oxygen, so it is prone to explosion and burning. In addition, lithium-ion batteries also generate redox reactions during charging and discharging. Explosion and spontaneous combustion are mainly caused by the accumulation of lithium batteries after they are heated, and they are not able to be diffused and released. Simply put, the lithium battery generates a large amount of heat during charging and discharging, which causes the internal temperature of the battery to rise and the temperature between the cells to be uneven, which causes the new energy of the battery to be unstable.

In August of this year, Apple's retail store in Amsterdam, the Netherlands, had to explode the iPad battery and release potentially harmful substances into the air. The retail store had to evacuate the consumers in the store to temporarily close the door. Previously, Samsung, Xiaomi, Huawei, etc. have also been exposed to the spontaneous combustion of mobile phones. Many accidents have shown that when people are not properly charged or the ambient temperature is too high, it is easy to cause spontaneous combustion and explosion of the lithium battery, which has become a heart disease for manufacturers.


Why do you have a lithium battery?


The limitations in battery selection depend to a large extent on the development of the battery itself and commercial conditions. The world's first battery "voltaic stack" was made of zinc plate and tin plate. After that, zinc and copper batteries, wet batteries and dry batteries appeared one after another. Because they will not be missed and easy to carry, the dry battery will be long afterwards. It was widely used in time and was replaced by a rechargeable nickel-iron battery invented by Edison. Finally, lithium cobalt oxide was used as the positive electrode material, and lithium ion battery made of lithium metal as the negative electrode material became the last choice in the market.

Compared to other batteries, lithium batteries have obvious advantages. It has a long service life of more than six years, and the battery is small in size and high in energy density, reaching 460-600Wh/kg, which is 6 to 7 times that of lead-acid batteries. At present, Tesla announced that the 21700 battery system jointly developed with Panasonic has an energy density of 300Wh/kg. At the same time, aluminum batteries have high power endurance. Lithium iron phosphate lithium ion batteries for new energy vehicles can achieve 15-30C charge and discharge capacity, which is convenient for high-intensity start-up and acceleration of automobiles. Lithium batteries have high and low temperature adaptability, are environmentally friendly, and basically do not consume water during production.

In terms of commercial use of batteries, batteries that can be used for large-scale commercial applications are limited by the limitations of volume, weight, energy storage and release capacity, storage time, service life, cost, ease of use, and mass production. For these two reasons, lithium batteries have become the best solution.

Although the properties of the lithium battery itself determine the fate of its "flammable and explosive", it is not completely impossible to reduce risk and safety. Whether it is a mobile phone company or a new energy car company, through a reasonable battery management system and thermal management system, the battery can be safe and there will be no explosion or spontaneous combustion.


How to solve?


The battery will release heat during work, and it will spontaneously ignite and explode if it is too late to release. Therefore, it can be managed by the battery thermal management system. The thermal management system equipped with the new energy vehicle is a subsystem in the battery management system, which enables the battery to be cooled when the temperature is too high, and preheated when the temperature is low, thereby better Tesla's unique battery management system is a typical example of the performance of the battery.

Tesla has equipped its cars with thousands of lithium cobalt oxide batteries to provide kinetic energy. Its 18650 battery life can be recharged more than 1000 times, but due to the large unit density of the battery, the risk of spontaneous combustion and fire is also higher. Tesla uses its battery management system to realize real-time monitoring of various physical parameters of the battery, evaluate battery usage status, and conduct online diagnosis and early warning. It can also perform discharge and pre-charge control, battery balance management and thermal management. . Taking battery thermal management as an example, the temperature rise of the battery is controlled by liquid cooling, ie 50% water + 50% ethylene glycol.

In fact, manufacturers have already realized the limitations of lithium batteries. Fuel cells, graphene batteries, and lithium-air batteries are all in the direction of research and development. Hydrogen fuel cells in fuel cells are the most concerned, and hydrogen energy vehicles, as a branch of new energy vehicles, have also been doing commercial exploration.

In 2008, China's self-developed Volkswagen Passat model was held at the New Energy Vehicle Engineering Center of Tongji University through the restructuring and integration of fuel cell vehicles, and it was put into operation during the Beijing Olympic Games. Today, ten years have passed. In this year's CES Asia in Shanghai, Hyundai Motor exhibited a new generation of hydrogen fuel cell vehicle NEXO. The fuel cell system of this model has an efficiency of 60% and is already at the forefront of the world.

Compared with lithium batteries, fuel cells are safer. Because hydrogen explosions require extremely high concentrations, they often start to burn before the explosion, but they are difficult to explode. Moreover, the density of hydrogen is lower than the density of air, even if the fire is above the gas source, and not like lithium batteries or gasoline, the fuel is at the bottom of the cabin, and the entire vehicle will be quickly scrapped. In addition, the fuel cell has the advantages of high power generation efficiency, low environmental pollution, low noise, high reliability, and easy construction of a battery power station.

Of course, the high cost of fuel cells, transportation, and storage are also insufficiency compared to lithium batteries.


At last


Similarly, 3C digital products such as mobile phones and tablets using lithium batteries, emergency products such as mobile power supplies and emergency starting power supplies for automobiles, all of which have encountered difficulties in spontaneous combustion and explosion problems, let alone new energy vehicles, which must take into account More difficult points. New energy vehicles are the driving force of the times. Its wide-ranging application is undoubted. Although capital and mass production are urgent issues for new energy vehicles, at any time, product safety is the first.

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