Recycling and second life of MXene electrodes for lithium-ion batteries and sodium-ion batteries

The fast growth of electric vehicles and electronic devices produces a mounting number of spent batteries which have reached their end of life. Therefore, it is essential to find a sustainable and efficient approach to battery recycling. Conventional recycling via high-temperature decomposition of the active components in the electrode material into elements level has the disadvantages of cumbersome operation, environmentally unfriendly, and high cost. Herein, one type of MXene material, annealed delaminated Ti3C2Tz (AD-Ti3C2Tz) electrodes, obtained by vacuum-assisted filtration and annealing processes, was directly used as free-standing anodes for both lithium-ion batteries and sodium-ion batteries without the use of binder or carbon additives. Electrochemical analysis showed that the non-diffusion-controlled redox reaction dominates the electrochemical behavior of the AD-Ti3C2Tz electrode. Furthermore, the AD-Ti3C2Tz electrode exhibits good electrochemical performance without adding conductive carbon in lithium-ion and sodium-ion batteries. For example, the lithium storage capacity was 89 mAh g−1 after 2000 cycles at a specific current of 1 A g−1. The sodium storage capacity is 108 mAh g−1 and 71 mAh g−1 at 0.02 A g−1 and 2 A g−1, respectively. After AD-Ti3C2Tz electrodes reach the end of their battery life, facile direct recycling processes were employed to recover the electrodes and the capacity recovery rate is above 90 %. Besides, the cycled MXene electrodes can be easily oxidized into TiO2/C hybrids with adjustable carbon content by changing the heat-treatment temperature in CO2 flow. The obtained TiO2/C could be widely applied in batteries and the electrocatalysis field, which realizes the second life of cycled MXene.