New energy storage device developed in the United States may fully charge electric vehicles in minutes

According to foreign media reports, researchers at Texas A&M University have developed a new energy storage device based on plants. The device is flexible, lightweight, and cost-effective. In the near future, it can even fully charge electric vehicles in a few minutes.

Image source: TAMU official website

"It has been tricky to apply biomaterials in energy storage devices because it is difficult to control the resulting electrical properties, which can severely affect the device's lifecycle and performance. In addition, manufacturing biomaterials often involves hazardous chemical processing," said lead researcher Dr. Hong Liang. "We have designed an environmentally friendly energy storage device with superior electrical properties that is easy to manufacture, safe, and at a much lower cost."

Energy storage devices generally come in the form of batteries or supercapacitors. Both devices can provide electric current when needed, but there are some fundamental differences. Batteries can store a large amount of charge per unit volume, while supercapacitors can quickly generate a large amount of current in a short period of time. Therefore, supercapacitors can charge devices faster.

The internal structure of a supercapacitor is basically the same as that of a normal capacitor. Both can store charge on metal plates or electrodes. However, unlike normal capacitors, supercapacitors can be made in different sizes and shapes using different designs for different uses. In addition, supercapacitors can also use different electrode materials.

During the research, Liang and his team were attracted to manganese dioxide nanoparticles and used this material to design an electrode for supercapacitors. Liang said: "Manganese dioxide is cheaper, more abundant, and safer than other transition metal oxides, such as ruthenium oxide or zinc oxide, which are widely used to make electrodes. However, an obvious drawback of manganese dioxide is its low electrical conductivity."

Lignin is a natural polymer that binds wood fibers together. Previous studies have shown that combining lignin with metal oxides can improve the electrochemical performance of electrodes. To make the electrodes, the research team treated purified lignin with potassium permanganate, a common disinfectant. Then, high temperature and pressure were applied to initiate an oxidation reaction, causing the potassium permanganate to decompose and deposit manganese dioxide on the lignin. Next, they coated the lignin and manganese dioxide mixture on an aluminum plate to form an environmentally friendly electrode. Finally, the researchers assembled a supercapacitor by sandwiching a gel electrolyte between the lignin-manganese dioxide-aluminum electrode and another electrode made of aluminum and activated carbon.

Tests have shown that the electrochemical properties of this supercapacitor are very stable. In particular, the specific capacitance, which is the ability of the device to store charge, changes very little even after thousands of charge and discharge cycles. It has been observed that when the lignin-manganese dioxide reaches the optimal ratio, the specific capacitance of this supercapacitor can reach more than 900 times that of other supercapacitors. Moreover, these supercapacitors are also very light and flexible, and can be used as structural energy storage components in automobiles, with a wide range of uses.

"In this study, we used a low-cost, sustainable method to create plant-based supercapacitors with excellent electrochemical performance," Liang said. "In the near future, we hope to make our supercapacitors 100 percent environmentally friendly devices by incorporating only green, sustainable ingredients."