Global future trends: green energy storage industry
世界未來趨勢:綠色儲能產業
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          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.

          由於全球暖化、節能減碳以及石油即將耗盡等議題,全球正處於能源轉型的關鍵時期,世界各國都正在極力推展綠能產業,以因應接踵而來的能源問題。隨著3C科技產業的蓬勃發展,鋰離子電池已大量運用在許多可攜式產品上,而電動車產業也成為當前世界發展的主流之一。政府宣示2035年新售機車全面電動化,2040年新售汽車面電動化的目標,期能改善空污問題,預計將進一步帶動車用動力電池之需求成長。鄧熙聖教授所帶領的研究團隊投入鋰電池、超級電容器以及光觸媒分解水等能研究方面研究多年,期望能對能源產業有更多貢獻。

          組成鋰離子電池的四大核心材料為正極材料、負極材料、電解液及隔離膜,它們也影響了電池的效能和續航力,其中電解液的主要功能是在電池內部以離子的型態提供電流的通路,須具備高離子傳輸率及不易與電極發生反應等特性。目前市售鋰離子電池主要是採用液態電解質為主,但其易有洩漏導致腐蝕問題,或因高溫因素導致隔離膜融化,進而使鋰離子電池短路而爆炸;若使用以高分子材料或無機材料為主的固態電解質,因其不含揮發易燃的有機溶劑,也不需要使用隔離膜,不僅可以大幅提高電池的安全性,還可配合產品外觀需求任意設計形狀。本團隊掌握此關鍵發展趨勢,開發高電位與高安全性的固態電解質,並針對固態電解質與電極界面特性及鋰離子傳遞機制進行深入探討,並搭配成大防火研究中心鋰電池實驗室進行軟包全電池製作測試,未來將成為可供廠商技術移轉的核心技術,並帶動鋰離子電池產業自主技術開發動能,有效節省開發鋰離子電池材料的製程成本、人力與時間。

          在電動車的發展中,除了鋰電池作為主要能源的供應外,超級電容器由於其本身持有的優勢,越來越受到業界的重視。超級電容器是一種具備高儲電能力,以及能提供強大脈衝功率的物理二次電源,其原理是透過電解質中的離子,在電極表面進行的物理性的吸附及脫附形成一雙電荷層,進而儲存電荷,因此又可稱為電雙層電容器。而超級電容器具有以下幾個優點:高功率密度、極佳長效表現、可高速充放電等優點,但由於其儲電機制沒有化學反應的參與,因此即使超級電容器擁有高功率密度,其能量密度相較於鋰電池較低。在電動車產業的運用上,由於超級電容器所具備的高功率密度,可運用在電動車在起步、加速、煞車回收動能時對於馬達瞬間大電流輸出的要求,若與鋰電池互相搭配使用,可以降低大電流放電對於電池壽命的損耗,有效延長電池壽命。目前市面上的超級電容器也以液態電解質為大宗,基於液態電解質之漏液等問題,鄧熙聖老師研究團隊致力開發高分子膠固態電解質,搭配有機相電解液,使超電容可供作之電位窗擴大,透過計算能量密度之公式可知擴大電位窗可提升超級電容的能量密度;除了高分子膠固態電解質,本團隊亦致力於研究鋰離子電容,其結合了鋰離子電池(高能量密度)以及超級電容器(高功率密度)的優點,是一種極具開發潛力的新型除能系統。

          除了鋰離子電池以及超級電容器之外,太陽能被認為是一種理想的可再生且乾淨的能源。然而,由於到達行星的陽光程度的變化取決於位置,季節和時間需要太陽能以經濟有效且環境友好的方式轉換和儲存。氫是一種極具潛力的能量載體,具有高能量密度的優點,遠遠超過汽油和煤的能量密度,沒有碳排放,只有因燃燒產生的水的有用副產物,並且易於運輸。其研究團隊使用一種豐富的材料-氧化石墨烯量子點,並透過陽光將水分解為氫和氧。各種表面工程策略,例如表面形態控制,表面修飾,表面相結和助催化劑負載,以產生更有效的水分解已被鄧老師團隊所開發。此技術定制氧化石墨烯量子點的性質並使其對於氫氣量產生更具吸引力。