Flexible Quasi-Solid-State Sodium Battery for Storing Pulse Electricity Harvested from Triboelectric Nanogenerators.

In order to satisfy the increasing requirements on operation time of wearable and portable electronic devices, novel self-powered systems by integrating triboelectric nanogenerator (TENG) with an energy storage device have emerged as a promising technology to provide sustainable power. Here, a flexible sodium composite anode (Na@CC) was prepared by infusing the molten sodium into flexible sodiophilic carbon cloth. The symmetric cell with the Na@CC anode shows stable sodium plating and stripping for 400 h. The full cell with a flexible quasi-solid-state electrolyte, Na3V2(PO4)3@C nanofiber cathode, and Na@CC anode delivers an excellent rate capacity of 72.5 mAh g-1 at 5 C and also exhibits stable cycling performance under different bent degrees. By combining with TENG to form a self-powered system, the flexible quasi-solid-state sodium battery can effectively store the pulse current and shows stable discharging capacity for over 100 cycles. The advanced flexible battery demonstrates its capability as a promising energy storage part in combination with TENGs and shows great potential in powerful flexible self-powered systems.

Effects of Pulse Charging by Triboelectric Nanogenerators on the Performance of Solid-State Lithium Metal Batteries.

Solid-state lithium metal batteries (SSLMBs) are an emerging technology because they can effectively solve the safety problem facing the lithium-ion batteries with nonaqueous liquid electrolyte. However, the lithium dendrite problem in SSLMBs can still occur at the sites of grain boundaries and defects. It is reported that effective charge procedures enable to suppress the growth of lithium dendrite, especially the pulse charging mode. In this work, SSLMBs were charged by a vertical contact-separation triboelectric nanogenerator (TENG). The effects of the pulse current on the lithium dendrite growth of SSLMBs are studied. It is found that the lithium ions can diffuse uniformly during the intermittent period of the pulse current compared to the constant current charge, so the growth rate of the lithium dendrites is effectively inhibited by the pulse current. At the same time, it is found that the lower the frequency of TENG is, the slower the growth rate of lithium dendrites is. This work provides a guideline for designing an appropriate charging method for durable SSLMBs.

Fe2+ -Doped Layered Double (Ni, Fe) Hydroxides as Efficient Electrocatalysts for Water Splitting and Self-Powered Electrochemical Systems.

Developing nonprecious electrocatalysts with superior activity and durability for electrochemical water splitting is of great interest but challenging due to the large overpotential required above the thermodynamic standard potential of water splitting (1.23 V). Here, in situ growth of Fe2+ -doped layered double (Ni, Fe) hydroxide (NiFe(II,III)-LDH) on nickel foam with well-defined hexagonal morphology and high crystallinity by a redox reaction between Fe3+ and nickel foam under hydrothermal conditions is reported. Benefiting from tuning the local atomic structure by self-doping Fe2+ , the NiFe(II,III)-LDH catalyst with higher amounts of Fe2+ exhibits high activity toward oxygen evolution reaction (OER) as well as hydrogen evolution reaction (HER) activity. Moreover, the optimized NiFe(II,III)-LDH catalyst for OER (O-NiFe(II,III)-LDH) and catalyst for HER (H-NiFe(II,III)-LDH) show overpotentials of 140 and 113 mV, respectively, at a current density of 10 mA cm-2 in 1 m KOH aqueous electrolyte. Using the catalysts for overall water splitting in two-electrode configuration, a low overpotential of just 1.54 V is required at a benchmark current density of 10 mA cm-2 . Furthermore, it is demonstrated that electrolysis of the water device can be drived by a self-powered system through integrating a triboelectric nanogenerator and battery, showing a promising way to realize self-powered electrochemical systems.