Thiourea induced the N/S co-doped carbon skeleton suppressing the dissolution of V to boost superior cyclic stability of Na3V2(PO4)3

Currently, poor conductivity property and volume collapse have severly hindered development of Na3V2(PO4)3. Meanwhile, the dissolution of active V leads to the unstable cyclic performance. Traditional modified methods using carbon-based materials only elevate the electronic conductivity, without considering the interaction between carbon skeleton and Na3V2(PO4)3 grains. In this work, the in-situ modified carbon skeleton by N/S diatomic doped derived from thiourea is successfully synthesized through a facile sol-gel route. Significantly, the synergistic effects of N and S elements can provide more defects and active sites in carbon substrate, stimulating more Na+ to participate the electrochemical process. Moreover, the in-situ N/S co-doping strategy promotes amorphous carbon converting to graphitized carbon, effectively accelerating electronic conductivity. Especially, a coral morphology is formed during sintering process, coming from the pyrolysis effect of thiourea. The porous construction can promote the infiltration of electrolyte, enlarging the contact surface areas between particles and electrolyte. Meanwhile, the generated micropores can relieve the pressure from the shrinkage of crystal to enhance the structural stability. More importantly, due to the introduction of S in carbon substrate, stable C–S–C bonds can be formed between carbon molecular layers to increase the layer distance, benefiting for Na+ migration. Notably, a strong C–S–V bridge bond connection is generated that combines Na3V2(PO4)3 and carbon materials, inhibiting the dissolution of V in electrolyte, resulting in superior cyclic stability. NVP/C@N,S-10 % submits high capacities of 90.5 mAh g−1 and 75.9 mAh g−1 at 60 and 80C, remaining 59.2 mAh g−1 and 57.9 mAh g−1 after 20,000 cycles.