Significant enhancement of proton conductivity in solid acid at the monolayer limit.

Proton transport in nanofluidic channels is not only fundamentally important but also essential for energy applications. Although various strategies have been developed to improve the concentration of active protons in the nanochannels, it remains challenging to achieve a proton conductivity higher than that of Nafion, the benchmark for proton conductors. Here, taking H3Sb3P2O14 and HSbP2O8 as examples, we show that the interactions between protons and the layer frameworks in layered solid acid HnMnZ2O3n+5 are substantially reduced at the monolayer limit, which significantly increases the number of active protons and consequently improves the proton conductivities by ∼8 ‒ 66 times depending on the humidity. The membranes assembled by monolayer H3Sb3P2O14 and HSbP2O8 nanosheets exhibit in-plane proton conductivities of ~ 1.02 and 1.18 S cm-1 at 100% relative humidity and 90 °C, respectively, which are over 5 times higher than the conductivity of Nafion. This work provides a general strategy for facilitating proton transport, which will have broad implications in advancing both nanofluidic research and device applications from energy storage and conversion to neuromorphic computing.

Amorphous Heterostructure Derived from Divalent Manganese Borate for Ultrastable and Ultrafast Aqueous Zinc Ion Storage.

Aqueous zinc-manganese (Zn-Mn) batteries have promising potential in large-scale energy storage applications since they are highly safe, environment-friendly, and low-cost. However, the practicality of Mn-based materials is plagued by their structural collapse and uncertain energy storage mechanism upon cycling. Herein, this work designs an amorphous manganese borate (a-MnBOx ) material via disordered coordination to alleviate the above issues and improve the electrochemical performance of Zn-Mn batteries. The unique physicochemical characteristic of a-MnBOx enables the inner a-MnBOx to serve as a robust framework in the initial energy storage process. Additionally, the amorphous manganese dioxide, amorphous Znx MnO(OH)2 , and Zn4 SO4 (OH)6 ·4H2 O active components form on the surface of a-MnBOx during the charge/discharge process. The detailed in situ/ex situ characterization demonstrates that the heterostructure of the inner a-MnBOx and surface multicomponent phases endows two energy storage modes (Zn2+ /H+ intercalation/deintercalation process and reversible conversion mechanism between the Znx MnO(OH)2 and Zn4 SO4 (OH)6 ·4H2 O) phases). Therefore, the obtained Zn//a-MnBOx battery exhibits a high specific capacity of 360.4 mAh g-1 , a high energy density of 484.2 Wh kg-1 , and impressive cycling stability (97.0% capacity retention after 10 000 cycles). This finding on a-MnBOx with a dual-energy storage mechanism provides new opportunities for developing high-performance aqueous Zn-Mn batteries.

Developing high voltage Zn(TFSI)2/Pyr14TFSI/AN hybrid electrolyte for a carbon-based Zn-ion hybrid capacitor.

Aqueous Zn-ion hybrid capacitors (ZIHCs), integrating the typical characteristics of Zinc ion batteries and supercapacitors, have become a promising candidate to replace or supplement lithium-ion energy storage technology. However, the narrow operating voltage window and the instability of the Zn/electrolyte interface caused by aqueous solvents have become a great challenge for practical applications. Here, we developed a new type of hybrid electrolyte (Zn(TFSI)2/[[Pyr14TFSI]3]16/[AN]4) based on the organic solvent (AN) combined with ionic liquid (Pyr14TFSI) and Zn salt (Zn(TFSI)2). This non-flammable electrolyte benefited from the synergistic advantages of Pyr14TFSI and AN, and could output a wide electrochemical window (3.32 V vs. Zn/Zn2+) and good compatibility with metallic Zn, while possessing excellent wettability. Theoretical and experimental results further reveal that such superb performance originates from the change of Zn coordination environment. Consequently, the constructed ZIHC displays a stable cycling performance (10 000 cycles at 5 A g-1 without significant capacity fade) and a high operating voltage of 2.1 V. This newly developed electrolyte, which solves the conventional interface problem and improves the voltage window, will promote the development of ZIHCs.

Construction of Supercapacitor-Based Ionic Diodes with Adjustable Bias Directions by Using Poly(ionic liquid) Electrolytes.

The newly emerging supercapacitor-diode (CAPode), integrating the characteristics of a diode into an electrical-double-layer capacitor, can be employed to extend conventional supercapacitors to new technological applications and may play a crucial role in grid stabilization, signal propagation, and logic operations. However, the reported CAPodes have only been able to realize charge storage in the positive-bias direction. Here, bias-direction-adjustable CAPodes realized by using a polycation-based ionic liquid (IL) or a polyanion-based IL as electrolyte in an asymmetric carbon-based supercapacitor architecture are proposed. The resulting CAPodes exhibit charge-storage function at only the positive- or negative-bias direction with a high rectification ratio (≈80% for rectification ratio II, RRII ) and an outstanding cycling life (4500 cycles), representing a crucial breakthrough for designing high-performance capacitive ionic diodes.

Controllably Enriched Oxygen Vacancies through Polymer Assistance in Titanium Pyrophosphate as a Super Anode for Na/K-Ion Batteries.

Although sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are promising prospects for next-generation energy storage devices, their low capacities and inferior kinetics hinder their further application. Among various phosphate-based polyanion materials, titanium pyrophosphate (TiP2O7) possesses outstanding ion transferability and electrochemical stability. However, it has rarely been adopted as an anode for SIBs/PIBs due to its poor electronic conductivity and nonreversible phase transitions. Herein, an ultrastable TiP2O7 with enriched oxygen vacancies is prepared as a SIB/PIB anode through P-containing polymer mediation carbonization, which avoids harsh reduction atmospheres or expensive facilities. The introduction of oxygen vacancies effectively increases the pseudocapacitance and diffusivity coefficient and lowers the Na insertion energy barrier. As a result, the TiP2O7 anode with enriched oxygen vacancies exhibits ultrastable Na/K ion storage and superior rate capability. The synthetic protocol proposed here may offer a simple pathway to explore advanced oxygen vacancy-type anode materials for SIBs/PIBs.

Structural Modulation of Co Catalyzed Carbon Nanotubes with Cu-Co Bimetal Active Center to Inspire Oxygen Reduction Reaction.

Rational design of highly efficient catalyst for ORR is critical for development of advanced air cathode in Zn-air cells and fuel cells. To optimize the ORR performance of Co based cathode, the structure of carbon nanotube from DCI-Co precursor could be controlled through modulate synthetic parameters. The optimized ORR catalyst Co@NCNT-700 exhibit larger BET area, higher content of Co-N x and graphitic N, which performance could be improved in further through Cu doping. The experiment data approved that the activity of Co-N x was enhanced by the synergistic effect with introduced Cu. Furthermore, the high-performance zinc-air batteries was fabricated with the bimetal catalyst CuCo@NCNT-700 as an air electrode. The high open-cycle potential (1.54 V) and peak power density (0.275 W.cm-2 at 0.474 A.cm-2) were achieved, which would be potentially used to develop next generation energy conversion devices.

Amorphous Iron(III)-Borate Nanolattices as Multifunctional Electrodes for Self-Driven Overall Water Splitting and Rechargeable Zinc-Air Battery.

Highly stable and low-cost electrocatalysts with multi-electrocatalytic activities are in high demand for developing advanced energy conversion devices. Herein, a unique trifunctional amorphous iron-borate electrode is developed, which is capable of boosting hydrogen evolution, oxygen evolution, and oxygen reduction reactions simultaneously. The amorphous iron borate can self-assemble into well-defined nanolattices on electrode surface through a facile hydrothermal process, which possess more active sites and charge transfer pathways. As a result, the asymmetry overall water-splitting cell that adopts the amorphous electrodes as anode and cathode can be driven at 1.56 V with the current density of 10 mA cm-2 , which is lowest in state-of-the-art catalysts. Moreover, the water-splitting devices can be powered by a two-series-connected amorphous electrode-based zinc-air battery with high stability and Faradic efficiency (96.3%). The result can offer a potential and promising alternative way to develop metal-borate electrode for multifunctional applications.