Due to global warming, energy conservation and carbon reduction, along with the imminent depletion of oil, the world is at a critical stage of energy transformation. Across the world countries are vigorously promoting the green energy industry to help cope with the ensuing energy problems. With a consumer electronics boom, lithium-ion batteries have been widely used in many portable products, and now the electric vehicle industry has become part of the current development. The government has announced the goal of banning the sale of gasoline-powered motorcycles and fuel-powered cars for electric ones by 2035 and 2040, which is expected to improve air pollution and further drive the growth of demand for vehicle power batteries. Professor His-sheng Teng's research team has devoted many years to energy research; lithium batteries, super capacitors and photocatalytic water splitting, hoping to contribute more to the energy industry.
The four core materials of lithium-ion batteries are cathode material, anode material, electrolyte and isolation film. These affect the efficiency and endurance of batteries. The main function of the electrolyte is to provide current paths in the form of ions inside the batteries; it must have high ion transmission rates and not react with the electrodes. At present, the commercially available lithium-ion battery is based mainly on liquid electrolytes, but it is prone to leakage. This leads to corrosion, or melting of the separator due to high temperature factors, which will result in a short circuit and potential explosion of lithium-ion batteries. If a solid-state electrolyte based on a polymer or inorganic materials is used, it does not contain volatile and flammable organic solvents, nor does it need to use a separator, it can greatly improve the safety of the battery, and can be manufactured into any shape according to the appearance of the product. Our team, by keeping tabs on this key development trend, developed high potential and high safety solid electrolytes, and discussed in depth the interface characteristics between solid electrolytes and electrodes and the lithium-ion transfer mechanism. Furthermore, a collaboration with the lithium battery laboratory of the NCKU Fire Protection and Safety Research Center allowed us to test the production of soft pack batteries. In the future, it will become the core technology for manufacturers for energy transfer technology, and will drive independent technology development of lithium-ion battery industry to effectively save cost, manpower and time of developing lithium-ion battery materials.
In the development of electric vehicles, in addition to lithium batteries as the main energy supply, super capacitors have attracted increasing attention from the industry. A super capacitor (SC) is a high-capacity capacitor that can provide a physical secondary power supply with a strong pulse power. Its principle is to form a double charge layer by physical adsorption and desorption on the surface of electrodes through ions in the electrolyte. and then store the charge; hence they are also known as electric double‐layer capacitors. Super capacitors have the following advantages: high power density, excellent long-term performance, high-speed charging and discharging. However, because their storage mechanism does not involve chemical reactions, even if they have high power density, their energy density is lower than that of lithium batteries. Regarding its application in the electric vehicle industry, because of its high power density, it can be used to meet the requirement for instantaneous high current output of the motor when the electric vehicle starts, accelerates and brakes to recover kinetic energy. If super capacitors are used in conjunction with lithium batteries, the loss of battery life caused by high current discharge can be reduced and the battery life prolonged effectively. Super capacitors currently on the market are mostly based on liquid electrolytes. Given the leakage of liquid electrolytes, Professor His-sheng Teng's research team has been devoted to developing polymer gel solid electrolytes coupled with organic phase electrolytes to prevent leakage and enlarge the potential window of the super capacitor. The formula for calculating the energy density shows that enlarging the potential window can increase the energy density of super capacitors. In addition to polymer gel solid-state electrolytes, our team has been committed to the study of lithium-ion capacitors, which combines the strength of lithium-ion batteries (with a high energy density) and super capacitors (with a high power density), and created a new energy storage system with great potential for development.
In addition to lithium-ion batteries and super capacitors, solar energy is considered to be an ideal renewable and clean energy source. However, since the amount of sunlight reaching the planet varies depending on location, season and time, solar energy needs to be converted and stored in an economical and environmentally friendly way. A potential energy carrier, hydrogen has the advantage of high energy density, far exceeding the energy density of gasoline and coal. It has no carbon emission, but a useful by-product of water produced by combustion and is easy to transport. The research team used a rich material, graphene oxide quantum dots, to break water down into hydrogen and oxygen through sunlight. Various surface engineering strategies, such as surface morphology control, surface modification, surface junction and catalyst loading, have been developed by Professor Teng's team to produce more effective water decomposition. This technology customizes the properties of graphene oxide quantum dots and makes them more attractive for hydrogen generation.