Room temperature synthesis of cobalt-manganese-nickel oxalates micropolyhedrons for high-performance flexible electrochemical energy storage device

Abstract

Cobalt-manganese-nickel oxalates micropolyhedrons were successfully fabricated by a room temperature chemical co-precipitation method. Interestingly, the Co0.5Mn0.4Ni0.1C2O4*nH2O micropolyhedrons and graphene nanosheets have been successfully applied as the positive and negative electrode materials (a battery type Faradaic electrode and a capacitive electrode, respectively) for flexible solid-state asymmetric supercapacitors. More importantly, the as-assembled device achieved a maximum energy density of 0.46 mWh·cm−3, a decent result among devices with similar structures. The as-assembled device showed good flexibility, functioning well under both normal and bent conditions (0°–180°). The resulting device showed little performance decay even after 6000 cycles, which rendered the Co0.5Mn0.4Ni0.1C2O4*nH2O//Graphene device configuration a promising candidate for high-performance flexible solid-state asymmetric supercapacitors in the field of high-energy-density energy storage devices.

Synthesis, structural and electrochemical properties of sodium nickel phosphate for energy storage devices

“…24 From our hybrid calculation, the reliable band gaps of m-and t-NaNiPO 4 are 4.94 and 5.03 eV, respectively, which are larger than those obtained from PBE (0.76 and 0.86 eV, respectively). Clearly, this reflects the presence of strong electron localization in NaNiPO 4 . Moreover, altering the site of Na and Ni causes the triphylite form creating more space for Na ions to occupy and intercalate along one-dimensional [010] channel in its orthorhombic framework, which is an essential factor for energy storage host materials.…”

“…All the peaks are symmetric and asymmetric stretching modes of the P-O bonds. The bands are assigned with reference to the reported assignments of the spectra of LiNiPO 4 and other phosphate structures. 26,27 The difference seen in position of the symmetric stretching vibration in NaNiPO 4 at 550°C compared with that at 400°C is a function of synthetic temperature and illustrates the formation of new crystal structure (maricite).…”

“…Experimental measurements of NaNiPO 4 Physical characterization. The X-ray diffraction patterns of sodium nickel phosphate (NaNiPO 4 ) synthesized at different temperatures (a) 300°C, (b) 400°C and (c) 550°C are shown in Fig.…”

“…[14][15][16] The ordered olivine structure, with general formula LiMPO 4 (M = Ni, Fe, Co or Mn) has been extensively studied as a cathode material in battery systems. These compounds contain tetrahedral anion structure units (XO 4 ) n− with strong covalent bonding, generating oxygen octahedral sites occupied by other metal ions. 17 Among the several metal atom substitutions, lithium-iron and lithium-manganese phosphates have been recognised as promising cations in the olivine structure.…”

“…Recently, paper-based flexible supercapacitor that suits the requirement for flexibility in portable electronics has also been widely reported. [2][3][4][5] In supercapacitors, the charge is stored electro-statically (non-faradaically) at the interfaces of the capacitor electrodes. 6 Non-faradaic processes are utilized in electrical double-layer (EDL) capacitors, which store energy based on the charge separation at a carbon electrode/electrolyte interface.…”