Scientists use "silicon" as the negative electrode of the battery to increase the range of electric vehicles by 10 times

    Researchers at the University of Waterloo collaborated with General Motors' Global Research and Development Center to study the heat treatment technology of battery silicon negative electrodes to solve the problem of excessive volume shrinkage and expansion rate of silicon negative electrodes during charging and discharging.

    Researchers at the University of Waterloo have developed a new generation of battery technology that can produce stable, small-volume, long-lasting batteries. In addition to being convenient for installation in small wearable devices, they can also be used in electric vehicles. Chen Zhongwei (sound) is a chemical engineer professor at the University of Waterloo and the head of the entire project. The research conducted by a team of graduate students led by him is said to greatly improve the performance and service life of batteries, far surpassing the lithium-ion batteries on the market. This research result has been published in the journal Nature Communications.

Chen Zhongwei (second from left) and team members

    How did the researchers manage to reduce the size of the battery while ensuring long battery life? The answer is that they used silicon as the negative electrode material of the battery and solved the material's drawbacks.

    As we all know, graphite has been used as negative electrode material in lithium-ion batteries for a long time. However, with the improvement of battery technology, the material itself has gradually become a bottleneck in the development of battery performance. Because the energy storage capacity of graphite has reached its upper limit, research institutions have begun to search for new negative electrode materials, and one of the attempts is to use silicon as the negative electrode of the battery.

    Theoretically, the specific capacity of silicon materials is much greater than that of graphite materials. The specific capacity value directly reflects the amount of electricity that can be released by the battery per unit weight. Currently, the negative electrode active material widely used in commercial lithium-ion batteries is graphite, with a specific capacity of about 360mAh/g. The theoretical specific capacity of the silicon material selected by the University of Waterloo reaches 4200mAh/g, which is more than 10 times that of graphite. Chen Zhongwei said that this means that an electric car can have a single charge range of up to 500 kilometers, and it is smaller and lighter than the current electric car battery, which can reduce the weight of the car body.

    However, there are many attempts to use silicon as anode material for batteries. The reason why it has not been widely used so far is due to some technical difficulties. We know that the cathode material of the battery is also closely related to the safety of the battery, and the shortcomings of silicon anode material are that it has poor safety and great volume changes during charging and discharging. With each charge and discharge, the volume shrinkage and expansion rate of silicon material is as high as 300%. Every increase and decrease in volume will form cracks, reduce the performance of the battery, cause a short circuit, and eventually cause the battery to stop working.

    This is also the problem that researchers at the University of Waterloo are focusing on in the process of developing batteries using silicon materials. Professor Chen's team worked with GM's Global Research Center to develop a heat treatment technology for silicon material electrodes that can minimize the volume expansion during charging, thereby improving the performance of the battery and the process of lithium-ion battery charge and discharge cycles. This heat treatment technology creates a unique structure of silicon negative electrodes, which can increase the charge and discharge cycles to 2,000 times as the battery energy capacity increases.

   Silicon anode battery is one of Professor Chen's research topics. He said that this battery technology has the possibility of commercial mass production, and the research team hopes to see the new battery enter the market before next year. The main projects of his team include the development of a new generation of clean and sustainable energy technologies using unique nanomaterials. In addition, they also focus on metal air batteries, lithium sulfur batteries and various types of flow batteries.