A High Capacity and Working Voltage Potassium-Based Dual Ion Batteries

Potassium-based dual ion batteries(KDIBs)have attracted significant attention owing to high working voltage,high safety,low processing cost,and environmental friendliness.Nevertheless,one great challenge for practical KDIBs is to develop suitable anode materials with high specific capacity.Herein,we report an architecture of hierarchically porous antimony nanoparticles/carbon nanofibers(HPSb CNFs)as flexible,free-standing anode for high-performance KDIBs.The HPSb CNFs with hierarchically porous structure,and high-content nitrogen doping,not only offer sufficient free space to tolerate the repetitive volume expansion of Sb nanoparticles during long-term cycling,but also greatly facilitate the transport of electrons and ions within electrode,ensuring high material utilization ratio.Thus,the KDIBs,constituted by HPSb CNFs-700(calcined at 700°C)anode and graphite cathode,exhibited a high reversible capacity of 440 m Ah g^(-1)with high discharge medium voltage of 4.5 V at a specific current of 200 m A g^(-1)(the highest capacity for all KDIBs normalized by the mass of the anode),and excellent cyclic life.Outstanding electrochemical reversibility of the KDIBs was further demonstrated by ex situ XRD,ex situ Raman spectrum,and HRTEM.These results suggest the as-designed HPSb CNFs-700 with highcapacity and long-term cycling stability is a promising anode material for high-performance KDIBs.

N,O co-doped porous carbon with rich pseudocapacitive groups exhibiting superior energy density in an acidic 2.4 V Li_(2)SO_(4)electrolyte

Designing a carbon material with a unique composition and surface functional groups for offering high specific capacity in a wide voltage window is of great significance to improve the energy density for the supercapacitor in a cheap and eco-friendly aqueous electrolyte.Herein,we develop an efficient strategy to synthesize a N,O co-doped hierarchically porous carbon(NODPC-1.0)with moderate specific surface area and pore volume as well as rich heteroatoms using a deep eutectic solvent(DES)as an activator.It is found that NODPC-1.0 with a large proportion of pseudocapacitive functional groups(pyrrole-N,pyridineN and carbonyl-quinone)can work stable in an acidic 2 mol/L Li_(2)SO_(4)(pH 2.5)electrolyte,exhibiting specific capacities of 375 and 186 F/g at the current densities of 1.0 and 100 A/g,respectively.Also,the assembled symmetric capacitor using the NODPC-1.0 as the active material and 2 mol/L acidic Li_(2)SO_(4)(pH 2.5)as the electrolyte shows an outstanding energy density of 74.4 Wh/kg at a high power density of 1.44 k W/kg under a broad voltage window(2.4 V).Relevant comparative experiments indicate that H+of the acidic aqueous electrolyte plays a crucial part in enhancement the specific capacity,and the abundant pseudocapacitive functional groups on the surface of the NODPC-1.0 sample play the key role in the improvement of electrochemical cycle stability under a broad voltage window.