Hybrid Energy Storage of Ni(OH)₂-coated N-doped Graphene Aerogel//N-doped Graphene Aerogel for the Replacement of NiCd and NiMH Batteries.

ABSTRACT: Although Nickel-Cadmium (NiCd) and Nickel-metal hydride (NiMH) batteries have been widely used, their drawbacks including toxic Cd and expensive La alloy at the negative electrodes, low energy density (40-60?Wh/kg for NiCd and 140-300?Wh/L for NiMH), low power density (150?W/kg for NiCd and 1000?W/kg for NiMH), and low working potential (1.2?V) limit their applications. In this work, Cd and La alloy were replaced with N-doped reduced graphene oxide aerogel (N-rGO_ae) providing a hybrid energy storage (HES) having the battery and supercapacitor effects. The HES of Ni(OH)₂-coated N-rGO_ae//N-rGO_ae provides 1.5?V, a specific energy of 146?Wh/kg, a maximum specific power of 7705?W/kg, and high capacity retention over 84.6% after 5000 cycles. The mass change at the positive electrode during charging/discharging is 8.5?µg?cm^-2 owing to the insertion/desertion of solvated OH^- into the ?-Ni(OH)₂-coated N-rGO_ae. At the negative electrode, the mass change of the solvated K⁺, physically adsorbed/desorbed to the N-rGO_ae, is 7.5??g?cm^-2. In situ X-ray absorption spectroscopy (XAS) shows highly reversible redox reaction of ?-Ni(OH)₂. The as-fabricated device without using toxic Cd and expensive La alloy has a potential as a candidate of NiCd and NiMH.

SUBMITTER: Sirisinudomkit P 

PROVIDER: S-EPMC5430751 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature