3D Porous Co 3 O 4 /MXene Foam Fabricated via a Sulfur Template Strategy for Enhanced Li/K-Ion Storage.

Co 3 O 4 is a potential high-capacity anode material for lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs), but the poor electrical conductivity and large volume fluctuations during long-term cycling severely limit its cycle durability and rate capabilities, especially for PIBs with large K-ion size. Here, we propose a sulfur template route to fabricate an integral 3D porous Co 3 O 4 /MXene (Ti 3 C 2 T x ) foam using simple vacuum co-filtrating an aqueous dispersion of Co 3 O 4 , S and MXene followed by calcining to remove the S template. The 3D porous structure can easily accommodate the large volume changes of Co 3 O 4 while maintains electrode structural integrity, allowing to realize outstanding long-term cycle stability when tested as anodes for both LIBs (620.4 mA h g -1 after 1000 cycles at 1 A g -1 ) and PIBs (134.1 mA h g -1 after 1000 cycles at 0.5 A g -1 ). The high metallic conductivity of the 3D porous MXene network further facilitates the electron/ion transmission, resulting in an improved rate capability of 390 mA h g -1 at 13 A g -1 for LIBs and 125.3 mA h g -1 at 1 A g -1 for PIBs. The robust performance of the 3D porous Co 3 O 4 /MXene foam reflects its perspective as a high-performance anode material for both LIBs and PIBs.