ABSTRACT
Organic anodes have emerged as a promising energy storage medium in proton ion batteries (PrIBs) due to their ability to reversibly accommodate non-metallic proton ions. Nevertheless, the currently available organic electrodes often encounter dissolution issues, leading to a decrease in long-cycle stability. In addition, the inherent potential of the organic anode is generally relatively high, resulting in low cell voltage of assembled PrIBs (<1.0 V). To address these challenges, a novel long-period stable, low redox potential biphenylzine derivative, [2,2'-biphenazine]-7,7'-tetraol (BPZT) is explored, from the perspective of molecular symmetry and solubility, in conjunction with the effect of the molecular frontier orbital energy levels on its redox potential. Specifically, BPZT exhibited a low potential of 0.29 V (vs SHE) and is virtually insoluble in 2 m H2SO4 electrolyte during cycling. When paired with MnO2@GF or PbO2 cathodes, the resulting PrIBs achieve cell voltages of 1.07 V or 1.44 V, respectively, and maintain a high capacity retention of 90% over 20000 cycles. Additionally, these full batteries can operate stably at a high mass loading of 10 mgBPZT cm-2, highlighting their potential toward long-term energy storage applications.
ABSTRACT
Aqueous zinc ion batteries (AZIBs) are gaining popularity as advanced energy storage devices that are economical, safe, and use resource-abundant storage options. In this study, we have synthesized a bipolar phenothiazine organic scaffold known as 3,7-bis(melaminyl)phenothiazin-5-ium iodide (PTDM), which is obtained by undergoing nucleophilic substitution through phenothiazinium tetraiodide hydrate (PTD) and melamine. Electrochemical results indicate that PTDM can act as a high-potential cathode material for rechargeable AZIBs. In detail, the aqueous PTDM//Zn full cell exhibits a high average voltage of approximate 1.13â V, along with a specific capacity of 118.3â mAh g-1 at 0.1â A g-1 . Furthermore, this demonstrated cell displays moderate long-term cycling stability over 6400 cycles, which is encouraging and suggests potential for developing advanced organic electrode materials for rechargeable AZIBs.
ABSTRACT
Aqueous zinc-ion batteries (AZIBs) are expected to be an attractive alternative in advanced energy storage devices due to large abundance and dependable security. Nevertheless, the undesirable energy density and operating voltage still hinder the development of AZIBs, which is intimately associated with the fundamental properties of the cathode. In this work, polyvinylpyrrolidone (PVP) intercalated Mn0.07 VOx (PVP-MnVO) with a large interlayer spacing of 13.5 Å (against 12.5 Å for MnVO) synthesized by a facile hydrothermal method is adopted for the cathode in AZIBs. The experimental results demonstrate that PVP-MnVO with expanded interlayer spacing provides beneficial channels for the rapid diffusion of Zn2+ , resulting in a high discharge capacity of 402 mAh g-1 at 0.1 A g-1 , superior to that of MnVO (275 mAh g-1 at 0.1 A g-1 ). Meanwhile, the PVP molecule remains in the layer structure as a binder/pillar, which can maintain its structural integrity well during the charging/discharging process. Consequently, PVP-MnVO cathode exhibits superior rate capability and cycling stability (89% retention after 4300 cycles at 10 A g-1 ) compared to that of MnVO (≈51% retention over 500 cycles at 2 A g-1 ). This work proposes a new approach to optimize the performance of vanadium-based electrode materials in AZIBs.
