Search

Lack of high-performance active materials limits the rapid development of advanced energy storage devices with both high power and high-energy performance. Here, Mn3O4/reduced graphene oxide (RGO) was synthesized as a negative material for both lithium-ion batteries (LIBs) and lithium-ion capacitors (LICs). The RGO prevents the aggregation of Mn3O4 and enhances the charge transport rate, enabling Mn3O4/RGO to exhibit high specific capacity, superior rate performance, and long cycling stability. More significantly, the charge storage of Mn3O4/RGO is mainly from the surface controlled reaction, which accounts for 58.2–83.3% of charge storage capacity when the scan rate increases from 0.1 to 1.0 mV s−1. Owing to high specific capacity and fast reaction kinetics of Mn3O4/RGO, the composite exhibits high energy performance when assembled with a LiNi0.5Co0.2Mn0.3O2 cathode, and achieves both high-energy and high-power performance in LICs after being assembled with activated carbon (AC). The LiNi0.5Co0.2Mn0.3O2//Mn3O4/RGO LIB displays a specific energy of 144.8 W h kg−1 at 215.1 W kg−1, and the AC//Mn3O4/RGO LIC exhibits a specific energy of 98.6 W h kg−1 at 180.1 W kg−1 with a retained specific energy of 70.3 W h kg−1 at a high specific power of 1937.5 W kg−1. [ABSTRACT FROM AUTHOR]

[Display omitted] Rechargeable alkaline nickel-zinc (Ni-Zn) batteries are attracting increased attention owing to their exceptional inherent safety and high specific capacity. Unfortunately, the limited power and cycling performances of these Ni-Zn batteries are still challenging. Herein, bimetal nickel–cobalt sulfide/ reduced graphene oxide (NiCo-S/RGO) composites with tunable compositions are synthesized by rational designing precursor and subsequent sulfidation treatment. NiCo-S is evenly anchored on RGO surface, resulting in increased number of electrochemical active sites, accelerated electrolyte ion diffusion, and enhanced electrical conductivity. Particularly, by tuning the Ni and Co composition ratios in NiCo-S, NiCo-S/RGO with a Ni to Co ratio of 2:1 (NiCo-S-2/RGO) shows a specific capacity of 145.7 mA h g−1 at 1 A g−1 and long-life cycling retention of 84.7% after 1000 cycles, and the above performances are superior than the controlled samples with other Ni to Co ratios. Furthermore, the as-assembled alkaline zinc batteries of NiCo-S-2/RGO//Zn deliver an impressive specific energy of 333.2 W h kg−1, showing great potential in practical applications. This experiment hopefully provides new idea for construction of high-performance electrodes of aqueous rechargeable batteries. [ABSTRACT FROM AUTHOR]

A novel and simple approach to preparing hierarchical zinc oxide/reduced graphene oxide (ZnO/RGO@RGO) composite is demonstrated using few-layered graphene oxide (GO) and metal zinc as starting materials following combined processes, including in-situ metal zinc reduction and catalyzed GO deoxygenation. Metal zinc can directly reduce GO sheets in aqueous GO suspension at room temperature to obtain a porous composite precursor (ZnO/RGO) with ZnO nanoparticles anchored on the RGO sheets. Then another RGO protecting layer is directly coated on the ZnO/RGO precursor to obtain the hierarchical ZnO/RGO@RGO composite. In this step, the exposed ZnO nanoparticles on the surface of ZnO/RGO play the role of catalyst to accelerate the deoxygenation of GO from the extra added GO aqueous suspension under mild hydrothermal condition. The reaction mechanism of metal zinc with GO aqueous suspension has been explored and the catalyst role of ZnO has been verified in this work. The prepared ZnO/RGO@RGO composite exhibited both stable cycling performance and good rate capability as anode for lithium-ion batteries. The method to prepare ZnO/RGO composite is economic and eco-friendly, and the ZnO catalyzing GO reduction opens a new approach to prepare graphene derivates. [ABSTRACT FROM AUTHOR]