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Nickel cobalt sulfide (NiCo 2 S 4 ) nanosheets were successfully grown on porous graphitic carbon nitride (g-C 3 N 4 ) nanosheets (NiCo 2 S 4 NSs/P-g-C 3 N 4 ), which was employed as supercapacitor electrode materials. The NiCo 2 S 4 NSs/P-g-C 3 N 4 electrode shows specific capacity as high as 506 C g −1 at a current density of 1 A g −1 , outstanding rate capability and cycling stability (almost no attenuation after 1500 cycles at 3 A g −1 ), which can be attributed to the unique ‘sheets on sheets’ architectures providing short ion diffusion pathways, and good ion permeability. NiCo 2 S 4 NSs/P-g-C 3 N 4 was combined with activated carbon (AC) to construct NiCo 2 S 4 NSs/P-g-C 3 N 4 //AC asymmetric supercapacitor (ASC), which offers a specific energy of 16.7 W h kg −1 at a specific power of 200 W kg −1 , and high cycling performance (about 99% retention after 5000 continuous cycles). An ASC device could power a mini-fan for about 60 s, demonstrating that NiCo 2 S 4 NSs/P-g-C 3 N 4 is a potential electrode material for energy storage.

The effects of various Ti concentrations doping on the electrochemical properties of LiNi0.8Co0.1Mn0.1O2 (NCM 811) sample were systematically studied. The XRD, EDS and XPS analyses indicated that the Ti-ion was substituted the occupied sites of Li and transition metal on the crystal structure. It also led to the increase of lithium interlayer spacing and the decrease of transition metal interlayer slab. The secondary particle size distribution of the 0.005 mol Ti-doped in LiNi0.8Co0.1Mn0.1O2 approximated to normal distribution. It showed multi-layer performance with high capacity (214.9 mAh g−1 at 0.1C), good rate performance (165.02 mAh g−1 at 1 C, 136.9 mAh g−1 at 5 C) and more excellent cyclic stability (77.01% after 150 t h at 1 C and 86.54% after 50 t h at 5 C). TEM studies revealed that the structural degradation on NCM 811 primary nano-particle could be effectively suppressed by the effect of Ti ions doped. The results demonstrated that doping of Ti content had superior advantages for LiNi0.8Co0.1Mn0.1O2 cathodes.