As a new type of two-dimensional material, MXene is one of the key materials for micro supercapacitors with high conductivity and ultra-high volume capacitance. However, MXene is easily oxidized under high anodic potential in water electrolyte, and is limited by the electrochemical stability window of water, resulting in the operating voltage is usually less than 0.6V, which greatly limits the energy density of MXene micro supercapacitor.
In addition, water electrolyte is easy to freeze below zero, resulting in a sharp decline in ionic conductivity. The structure of the electrolyte is very unstable at high temperatures, making it difficult to retain the water molecules inside. Therefore, there are still challenges in developing water electrolyte with high pressure resistance and wide temperature zone.
It is found that the symmetrical planar MXene micro supercapacitor based on highly concentrated lithium chloride gel electrolyte has a working voltage of up to 1.6V and a volume energy density of 31.7MWh /cm3. Due to the ultra-high ionic conductivity (69.5mS/cm) and ultra-low melting point (-57°C) of the highly concentrated lithium chloride gel electrolyte, MXene micro supercapacitors can operate in a wide temperature range from -40°C to 60°C, illustrating their usefulness in extreme environments. This work provides a new research idea for the construction of micro supercapacitor with high voltage and wide temperature region.
In terms of the construction of Mxene-based supercapacitors and batteries, Wu Zhongshuai's team has previously developed multi-functional water MXene ink for high capacitance electrodes, batteries and sensing materials, as well as micro supercapacitors. The MXene microelectrode strategy of ionic liquid pre-intercalation was developed to construct a micro supercapacitor with high specific energy. A 3d MXene - based dendrite-free lithium anode was developed. MXene nanoribbons were prepared by one-step alkalization of MXene, and MXene derived ultrathin sodium titanate or potassium titanate nanoribbons were obtained by oxidation treatment, which had excellent sodium/potassium storage properties.
The findings were published recently in the National Science Review. The first author of this work is Zhu Yuanyuan and Zheng Shuanghao, postdoctoral fellow of group 508 of the Institute.
The research work of the Two-dimensional Material Chemistry and Energy Application Group (508 Group) mainly focuses on the basic research of two-dimensional material chemistry and energy application, including two-dimensional energy materials and efficient electrochemical energy devices, two-dimensional catalytic materials and energy conversion applications, and has achieved systematic innovation achievements.
Wu Zhongshuai is the leader of the research group. His research field is two-dimensional materials chemistry. Energy catalysis (electrocatalysis, thermal catalysis); Micro/nano electrochemical energy (micro energy storage, super capacitor, lithium ion/lithium sulfur/solid state battery, etc.); Study on dynamic reaction process and mechanism of electrochemical catalysis/Energy storage.