Improved technology for electric vehicle batteries

Tesla Model S is the new darling of the electric car industry, but it has recently experienced three consecutive fires(including 60 kilowatt-hours and 85 kilowatt-hours of both battery versions), and the detailed cause of the fire is still under investigation.

Thanks to new technologies and the use of lightweight materials, the battery pack in ModelS takes only 4.4 seconds to accelerate from 0-60 mph. Due to the active nature of these materials, lithium batteries in the car need to have complete protection measures. The lithium battery pack in the car weighs 500 pounds and is located on the chassis of the vehicle. It is the same width as the wheelbase and is slightly shorter than the wheelbase. The actual physical size of the battery pack is 2.7 meters long, 1.5 meters wide and 0.1 meters to 0.18 meters thick. The thicker part of 0.18 meters is due to the superposition of two battery modules. This physical size refers to the overall size of the battery pack, including the upper and lower, left and right, and front and rear packaging panels. The structure of this battery pack is a universal design. In addition to the 18650 type cell, other eligible cells can also be installed. In addition, the battery pack is designed to be sealed and isolated from the air. Most of the material used is aluminum or aluminum alloy. It can be said that the battery is not only an energy center, but also part of the ModelS chassis. Its strong shell can play a good role in supporting the vehicle.

But even then it caught fire, which is why researchers need to speed up the development of a new generation of electric-vehicle battery technology.

This summer, the US Department of Energy's Advanced Research Program, APRA-E, invested $36 million to help researchers lay a solid foundation for developing next-generation battery designs. These include 22 technology projects, all of which aim to make electric vehicles more efficient and less costly.

Nickel hydride battery: from hybrid to pure electric car

One of the many battery researchers, Michael Felcenko, a chemical engineer at BASF, was funded by APRA-E to try to extend the nickel-zinc battery technology originally used in hybrid cars to pure electric vehicles.

In general, nickel-metal hydride batteries have an energy density of 1 kWh / kg. To apply it to pure electric vehicles, BASF must increase the energy density of nickel-metal hydride batteries to 30-50 kilowatt-hours per kilogram. The key to the success of this application is whether it can increase the energy density of nickel-metal hydride batteries to the desired value and reduce costs.

One possible way to achieve this goal is to replace the rare earth elements needed in the battery. The rare earth element is a collective name. There are 17 kinds of elements in this group. The reason why the rare earth element is called is not because of its small reserves, but because it is mainly present in mines and will cost a lot of money during the development process. In traditional nickel-metal hydride batteries, more than 50 % of the energy is generated by the reaction of rare earth elements. However, the storage performance of such elements is poor.

In order to solve this problem, BASF tried to use low-cost metal hydrogenated alloys. Professor Fetcenko believes that this material can improve the chemical properties of nickel-metal hydrogen batteries and reduce their cost. However, for pure electric vehicles, light improvements in the chemical properties of nickel-metal hydrogen batteries are not enough to replace lithium batteries because lithium batteries also have a crucial feature -- light weight or low density.

Zinc-Air Battery: From hearing aids to cars

Zinc-air batteries will lead the next generation of electric-vehicle battery technology, according to EnZincc, a Californian company. Michael Burz, head of the company's research team, said the next generation of electric car batteries should have three components: high performance, safety and low cost. He and his team are trying to change the design schema/architecture of the battery to achieve these three points.

He pointed out that the structure of the battery has not changed for more than 100 years, and people still have not been able to think outside the box. The so-called battery architecture includes three elements: positive, negative, and electrolyte. The positive pole releases electrons and the negative pole receives electrons. The positive and negative poles are separated by the electrolyte, which acts as a medium for the free flow of ions.

In lithium ion batteries, lithium ions move negatively to carbon-based compounds from the positive electrode of lithium oxide and use organic electrolytes. Zinc-air batteries are different. The positive electrode uses carbon to absorb oxygen in the air, and the negative electrode is a zinc alloy. Zinc is also a benign substance, and its by-product in batteries is zinc oxide, which is the main component of sunscreen.

Through the above methods, Zinc air batteries can achieve three characteristics: high efficiency, low cost and safety.

In that case, why not popularize the technology now? That's zinc-air batteries that can't be recharged. This is why it is currently only used in small devices such as hearing aids. In order to allow zinc air batteries to be charged, EnZinc has developed a new plan to place ordinary oxygen and zinc metal in alkaline electrolytes, generating current through the oxidation reaction of zinc, and after recharging, oxygen and zinc can be regenerated. So the cycle goes on and on, increasing the energy density of the battery.

New approach: battery weight loss

There are many directions for the development of electric vehicle batteries. Some researchers focus on improving their energy density and performance, while others focus on reducing the weight of batteries. For example, Professor Gabriel Veith of Oak Ridge National Laboratory in the United States and his team are studying how to reduce the weight of battery protection systems.

Gabriel Veith is a material scientist who hopes to develop a lightweight electrolyte material that functions as a battery safety system.

Veith explained: "When an electric vehicle crashes, the material undergoes phase transitions that make it difficult to penetrate. "This trait may be able to solve the problem of the recent Tesla battery fire. The problem for the team at present is to increase the response performance of the material. Veith said: "If the phase transition occurs only five minutes after the collision of the electric car, then this will not make any sense. "

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