A Ti3C2Tx-encapsulated Mn2+-doped Co(OH)2 nanosheets electrode grown on carbon cloth for low-temperature flexible supercapacitors

Abstract

In general, most flexible supercapacitors with excellent performance at room temperature cannot work properly at relatively low temperatures (such as 0 °C), mainly due to the poor cold resistance of the electrodes and electrolytes. In this paper, the carbon cloth was coated with positively charged Mn²⁺-doped Co(OH)₂ coating by electrodeposition and then impregnated with negatively charged Ti₃C₂T_x nanosheets suspension (This electrode is named CC@Co(OH)₂:Mn²⁺@T_x, Where x is the number of impregnation Ti₃C₂T_x.). The results show that the obtained electrode has a good supercapacitor performance with the specific capacitance of 22.13 F g^-1 (the area specific capacitance of the sample is 202.5 mF cm^-2), which is attributed to the synergistic effect of Ti₃C₂T_x and the flower microstructure of Mn²⁺-doped Co(OH)₂ coating. Ti₃C₂T_x was introduced to polyvinyl alcohol/sodium alginate hydrogel electrolyte to obtain a new antifreezing organohydrogel and then a flexible asymmetric supercapacitor was assembled with CC@Co(OH)₂:Mn²⁺@T₃ as the positive electrode, CC@T₃ as negative electrode, and the performance of the supercapacitor at 25 °C and at 0 °C were investigated. It was found the supercapacitor exhibited better performance at 0 °C instead of 25 °C. When the current density is 5 mA cm^-2, the area specific capacitance of the supercapacitor at 0 °C reaches 52.02 mF cm^-2. After 1000 cycles, the supercapacitor has a capacitance retention rate of 82.5% at 0 °C, which is much higher than that of 55.15% at 25 °C. The reason may be related to the Ti₃C₂T_x and the crosslinked networks structures of composite hydrogel. The results show that the supercapacitor has excellent working ability at 0 °C, which provides the possibility for the device to work normally in low temperature.