Constructing a multidimensional porous structure of K/Co co-substituted Na 3 V 2 (PO 4 ) 3 /C attached on the lamellar Ti 3 C 2 T x MXene substrate for superior sodium storage property.

Na 3 V 2 (PO 4 ) 3 (NVP) materials have emerged as prospective cathodes for sodium-ion batteries (SIBs). However, its weak intrinsic conductivity has limited deeper research. Herein, we adopt the strategy of simultaneous K/Co co-substitution and Ti 3 C 2 T x MXene (MX) introduction to optimize NVP. The K/Co co-substitution brings about the synergetic effect of NVP framework stabilization. Doping Co 2+ generates beneficial holes and accelerating electronic conductivity. The MX plates are stacked at random to form a porous construction, increasing the contact areas to provide more active sites for Na + shuttling and buffering the volume change. Furthermore, the lamellar MX and the carbon layers form efficient conductive networks that increase electron migration. Notably, K 0.1 Na 2.95 V 1.95 Co 0.05 (PO 4 ) 3 @MX (KC05@MX) exhibited an initial capacity of 116 mA h g -1 under 1 C with an extraordinary retention of 86.8% at the 400 th cycle. It realized high performance under 20 C and 50 C, and the outputs were 93.5 and 82.4 mA h g -1 at the 1 st cycle and 66.6 and 53.4 mA h g -1 at the 1000 th cycle, respectively, with slight capacity loss at 0.028% and 0.035%. Furthermore, the Bi 2 Se 3 //KC05@MX asymmetric full cell expressed great electrochemical properties, indicating the superior practical application prospect of KC05@MX.