Hydrothermal ion exchange synthesis of CoM(M=Fe or Mn)/MXene 2D/2D hierarchal architectures for enhanced energy storage

Bimetallic compounds can offer higher electrochemical activity and capacity than monometallic ones owing to their rich chemical valences. Herein, the performance enhancement of monometallic compounds by introducing metal ions was demonstrated, and the effects of different metal ions were investigated. Through introduction of metal ions into LDHs under a hydrothermal environment, one kind of 2D/2D hierarchical CoM-LDH(M=Fe or Mn)/MXene composites were successfully synthesized. It was found that the introduced Fe ions extremely improves the specific capacity and the introduced Mn ions extremely enhances the rate capability of monometallic composite. The fabricated CoFe-LDH/MXene (CF-MX10) electrode exhibits a specific capacity of 808 F g−1 at current density of 0.5 A g−1, much higher than that of CoMn-LDH/MXene (CM-MX10, 562 F g−1) and Co(OH)2/MXene (C-MX10, 270 F g−1). The high areal capacity or rate capacity are attributed to strong synergistic effect between CoM-LDH and MXene, as well as the introduction of metal ions that change the architecture and the electronic or ionic conductivity, which leads to much improved electrical conductivity and electrochemical stability.