Structure-Activity Relationships of a Ni-MOF, a Ni-MOF-rGO, and pyrolyzed Ni/C@rGO Structures for Sodium- ion Batteries

MOF (Metal-Organic Framework) based materials have attracted recent interest as- anode materials for Alkali- ion batteries. However, the insertion reaction that dictates the alkali ion storage in the MOFs being a conversion reaction depicts the drastic drop in cycling and rate stabilities. Herein we report a low- temperature twinning of a representative Ni-MOF with rGO (reduced graphene oxide) by low- temperature processing and through an intermediate physical mixing method to enhance the electrochemical anodic performance of the parent pristine Ni-based MOF that is Ni-MOF. The uniqueness of this process is that low- temperature processing (300 degrees C) ensures that the identity of MOF is maintained but generates intimate contacts between the Ni-MOF and thermally reduced GO (Graphene Oxide). The Ni-MOF@rGO composite so achieved has delivered a considerably enhanced rate and cycling stability with a capacity of 385 mAhg(-1) (100 mAg(-1)) which stays consistent till 400 charge- discharge cycles against the pristine MOF which degrades to 272 mAg(-1) in just 250 cycles. The rate enhancements at higher currents are also substantial with the Ni-MOF@rGO composite depicting the capacity of 205 mAhg(-1) at 1 Ag-1 as against the capacity of 113 mAhg(-1) for pristine Ni-MOF. The Ni-MOF@ rGO also depicts a considerably enhanced performance compared to carbonized (600 degrees C and 800 degrees C) control samples.