Seawater battery is a new energy storage technology that uses seawater as the electrolyte, which can effectively reduce battery production costs, is safe and sustainable, and has broad application prospects in fields such as ocean exploration, underwater communication, and island power supply. However, most of the seawater batteries currently developed are disposable and cannot be reused. Recently, Tian Xinlong and Yang Jinlin from Hainan University's "Ocean Clean Energy" innovation team have developed an ultra long cycle life, rechargeable chloride ion battery based on natural seawater electrolyte. This achievement has achieved a technological breakthrough in reversible anion storage electrodes, which is an innovation in sustainable water-based batteries and can provide a solution for energy storage and supply in deep and offshore fields. The relevant research paper has been published in the international academic journal "Journal of the American Chemical Society". Overcoming the problem of reversible storage technology for chloride ions: "China has vast sea areas and abundant seawater resources, which contain various soluble cations and anions with good ion conductivity. If natural seawater can be used as the electrolyte for batteries, it can solve the cost and safety issues of batteries." Professor Tian Xinlong from the School of Marine Science and Engineering at Hainan University introduced the original intention of the team's research and development of rechargeable seawater batteries to reporters. The existing seawater batteries are mostly disposable batteries that cannot be reused, which limits their application in many fields. This is because the electrode materials used in disposable seawater batteries do not have the ability to reversibly store chloride ions Yang Jinlin, Associate Researcher at the School of Marine Science and Engineering, Hainan University, stated. To achieve the transition from "disposable" to "reusable" seawater batteries, it is necessary to solve the problem of reversible storage electrodes for chloride ions. Tian Xinlong introduced that unlike conventional batteries that rely on cation storage such as lithium ions or sodium ions, the working principle of seawater batteries is based on chloride ion storage, which belongs to anions. Traditional electrode materials, such as oxides and sulfides, cannot achieve reversible storage of anions, including chloride ions, and therefore cannot be applied to the development of rechargeable seawater batteries. The research team screened more than 10 potential inorganic chloride ion storage materials through literature review and high-throughput calculations, and attempted to synthesize 7 of them. Finally, MXene, a novel two-dimensional material, was selected as the battery chlorine storage electrode. Unlike traditional materials, MXene material is a layered material with high conductivity Yang Jinlin introduced. High conductivity facilitates the rapid transfer of ions and electrons, while a stable layered structure facilitates the reversible insertion and extraction of chloride ions between material layers, which can improve the cycling life of the battery. The team researchers found that MXene materials have a controllable surface functional group - chlorine surface end groups. In addition, the chlorine surface end groups of the material can form covalent interactions with chloride ions in seawater. This weak interaction can both allow chloride ions to adsorb between material layers and facilitate their rapid migration, thereby achieving reversible storage of chloride ions. Although the primary problem of chlorine storage electrode materials has been solved, the corrosiveness of chloride ions in seawater still needs to be addressed. Yang Jinlin said that the team found in the early stages of the research that the charging voltage of seawater batteries was very low and the cycle life did not meet the requirements. By gradually eliminating influencing factors, researchers ultimately found that chloride ions have strong corrosiveness to the battery casing and current collector, which is the main reason affecting battery performance. In response to this issue, the team has begun to invest in designing more corrosion-resistant battery devices: using carbon paper and titanium foil that are more resistant to chloride ion corrosion instead of traditional copper foil as current collectors; Perform anti-corrosion treatment on the shell of the battery; Optimize the connection process. These improvement measures effectively reduce the damage of chloride ions to the battery, and enhance the overall performance and stability of the battery. At present, the optimal operating temperature range for lithium-ion batteries is between 15 degrees Celsius and 35 degrees Celsius, while the seawater battery we have developed has a wide temperature working ability and can maintain stable performance in the temperature range of minus 20 degrees Celsius to 50 degrees Celsius Yang Jinlin introduced that low or high ambient temperatures can have adverse effects on the performance of batteries, and even cause safety issues. The research team believes that this wide temperature working capability broadens the usage scenarios of batteries, allowing them to be used in devices that require extreme environments, such as electric vehicles and energy storage base stations. In the face of scorching summer heat and severe winter cold, the battery can maintain stable performance to ensure the continuous operation of the equipment. In the experiment, this newly developed battery also demonstrated good characteristics such as high reversible capacity, high energy density, and ultra long cycle life. Yang Jinlin explained that the higher the capacity and energy density of a battery, the longer it can be used after a single charge; Long cycle life means that the battery can be repeatedly charged and discharged multiple times while still maintaining excellent performance. In the experiment, the newly developed battery can cycle up to 40000 times in seawater electrolyte, which means its actual service life will exceed one year. Tian Xinlong introduced that the newly developed battery uses natural seawater instead of traditional organic solvents as the battery electrolyte, which can save about 10% of production costs. The assembly process of batteries does not require a harsh environment without water or oxygen, and has lower requirements for equipment and manufacturing processes. Therefore, it is expected that the overall price of batteries can be reduced by 20% to 30%. In addition, MXene electrode materials do not contain expensive metal elements such as lithium and cobalt, which greatly reduces the production cost of this battery. At the same time, it has the advantage of being non-toxic and environmentally friendly, which can help promote the sustainable development of global energy and achieve China's "dual carbon" goals. How to quickly achieve the implementation and transformation of innovative achievements? Tian Xinlong believes that in the long run, the application prospects and potential environmental benefits of ultra long cycle life seawater batteries cannot be ignored, but currently it still faces many technological and market challenges. We still need to address issues such as large-scale batch preparation of materials, structural and process optimization of battery devices, "he said. (New Society)