Boosting capacitive energy density of conjugated molecule modified porous graphene film as high-performance electrode materials

Graphene Film with a Controllable Microstructure for Efficient Electrochemical Energy Storage

The agglomeration of graphene sheets and undesired pore size distribution usually lead to unsatisfactory electrochemical properties of reduced graphene oxide (RGO) film electrodes. Herein, crumpled exfoliated graphene (EG) sheets are adopted as the microstructure-regulating agent to tune the morphology and micro-/mesopore amounts with the aim of increasing active surface sites and ion transportation paths in electrodes. With the optimum ratio between EG and GO, the resulting 75%-EG/RGO shows significantly improved specific gravimetric capacitance (C_s) and rate capability when compared with pure RGO electrodes in a symmetrical supercapacitor system. Moreover, when coupling the 75%-EG/RGO cathode with a Zn anode to form a Zn ion hybrid supercapacitor (ZHS), the 75%-EG/RGO exhibits a much higher C_s of 327.39 F g^-1 at 0.1 A g^-1 and can maintain 91.7% capacitance after 8000 cycles. Systematic ex situ X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) measurements reveal that the charge storage mechanism is based on both reversible physical adsorption and dual ion uptake. Furthermore, the quasi-solid-state flexible ZHS also presents high capacitive performance and can maintain ∼100% capacitance under various bending states, demonstrating potential application in wearable electronics. This strategy opens up a new path for constructing high-performance graphene film electrodes.

A Synergistic Strategy of Organic Molecules Introduced a High Zn2+ Flux Solid Electrolyte Interphase for Stable Aqueous Zinc-Ion Batteries

Aqueous rechargeable zinc-ion batteries (ARZIBs) are considered as attractive candidates for the next generation of high-safety and low-cost energy storage in large-scale power grids. However, challenges such as the dendrites and the corrosion on the zinc (Zn) surface result in short battery life and low reversibility of Zn plating/stripping. In this work, a method of preconditioning of a zinc anode in hybrid electrolytes (based on poly(ethylene glycol)-200 and H₂O) to form a solid electrolyte interphase (SEI) that prevents anode corrosion and dendrites is proposed. Though surface composition analysis and density functional theory calculation, this SEI has dense organic and inorganic components due to the induction of organic molecules and anions and has rapid kinetic and high-throughput properties for the transport of zinc ions. As a result, the SEI-modified Zn anode can maintain a low-voltage hysteresis stable cycle for more than 1600 h in aqueous electrolyte. The anode also exhibits impressive reversibility with a high Coulomobic efficiency of 99.23% over 1300 cycles. Furthermore, the ARZIB encapsulated by this anode and Mn-doped V₆O₁₃ cathode enables an outstanding electrochemical stability (181.8 mAh g^-1 after 800 cycles at room temperature, 102.2 mAh g^-1 after 1000 cycles at -15 °C). This work provides an intriguing idea for the stability maintenance of the anode for ARZIBs or other metal-ion batteries.