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It is of necessity to investigate the adjustment of flood discharge capacity in the Lower Yellow River (LYR) because of its profound importance in sediment transport and flood control decision-making, and additionally its magnitude is influenced by the channel and upstream boundary conditions, which have significantly varied with the ongoing implementation of soil and water conservation measures in the Loess Plateau and the operation of the Xiaolangdi Reservoir. The braided reach between two hydrometric stations of Huayuankou and Gaocun in the LYR was selected as the study area. Different parameters in the study reach during the period 1986–2015 were calculated, covering bankfull discharge (the indicator of flood discharge capacity), the pre-flood geomorphic coefficient (the indicator of channel boundary condition), and the previous five-year average fluvial erosion intensity during flood seasons (the indicator of incoming flow and sediment regime). Functional linkages at scales of section and reach were then developed respectively to quantitatively demonstrate the integrated effects of channel and upstream boundary conditions on the flood discharge capacity. Results show that: (1) the reach-scale bankfull discharge in the pre-dam stage (1986–1999) decreased rapidly by 50%, accompanied with severe channel aggradation and main-channel shrinkage. It recovered gradually as the geometry of main channel became narrower and deeper in the post-dam stage, with the geomorphic coefficient continuously reducing to less than 15 m −1/2 . (2) The response of bankfull discharge to the channel and upstream boundary conditions varied at scales of section and reach, and consequently the determination coefficients differed for the comprehensive equations, with a smallest value at the Jiahetan station and a highest value (0.91) at reach scale. Generally, the verified results calculated using the comprehensive equations agreed well with the corresponding measured values in 2014–2015. (3) The effect of channel boundary condition was more prominent than that of upstream boundary condition on the adjustment of bankfull discharge at the Jiahetan station and the braided reach, which was proved by a larger improvement in determination coefficients for the comprehensive equations and a better performance of geomorphic coefficient on the increase of bankfull discharge.

To simultaneously reduce the cost of environmental treatment of discarded food waste and the cost of energy storage materials, research on biowaste conversion into energy materials is ongoing. This work employs a solid-state thermally assisted synthesis method, transforming natural eggshell membranes (NEM) into nitrogen-doped carbon. The resulting NEM-coated LFP (NEM@LFP) exhibits enhanced electrical and ionic conductivity that can promote the mobility of electrons and Li-ions on the surface of LFP. To identify the optimal synthesis temperature, the synthesis temperature is set to 600, 700, and 800 °C. The NEM@LFP synthesized at 700 °C (NEM 700@LFP) contains the most pyrrolic nitrogen and has the highest ionic and electrical conductivity. When compared to bare LFP, the specific discharge capacity of the material is increased by approximately 16.6% at a current rate of 0.1 C for 50 cycles. In addition, we introduce innovative data-driven experiments to observe trends and estimate the discharge capacity under various temperatures and cycles. These data-driven results corroborate and support our experimental analysis, highlighting the accuracy of our approach. Our work not only contributes to reducing environmental waste but also advances the development of efficient and eco-friendly energy storage materials.

The deposition of sediments with different roughness increases uncertainty in the prediction of effective Manning's n (also known as composite roughness). In this paper, the changing rules of composite roughness and the influence on the discharge capacity of drainage pipes under different flows and slopes were studied by experimental measurement and numerical simulation. When the Froude number is less than 1, the composite roughness decreases gradually with the increase of flow. When the Froude number is more than 1, the composite roughness increases at first and then decreases with the increase of flow. It also showed that the different bed roughness has a great influence on composite roughness, which affects the hydraulic characteristics of flow. The composite roughness of the drainage pipe increases as the bed roughness increases. The water surface rises and the average velocity decreases under a certain slope and flow. The formulas for calculating the composite roughness are obtained by analogy analysis, which can provide theoretical support for the design of the drainage pipeline.

Non-aqueous sodium-ion batteries (SiBs) are a viable electrochemical energy storage system for grid storage. However, the practical development of SiBs is hindered mainly by the sluggish kinetics and interfacial instability of positive-electrode active materials, such as polyanion-type iron-based sulfates, at high voltage. Here, to circumvent these issues, we proposed the multiscale interface engineering of Na 2.26 Fe 1.87 (SO 4 ) 3 , where bulk heterostructure and exposed crystal plane were tuned to improve the Na-ion storage performance. Physicochemical characterizations and theoretical calculations suggested that the heterostructure of Na 6 Fe(SO 4 ) 4 phase facilitated ionic kinetics by densifying Na-ion migration channels and lowering energy barriers. The (11-2) plane of Na 2.26 Fe 1.87 (SO 4 ) 3 promoted the adsorption of the electrolyte solution ClO 4 − anions and fluoroethylene carbonate molecules, which formed an inorganic-rich Na-ion conductive interphase at the positive electrode. When tested in combination with a presodiated FeS/carbon-based negative electrode in laboratory- scale single-layer pouch cell configuration, the Na 2.26 Fe 1.87 (SO 4 ) 3 -based positive electrode enables an initial discharge capacity of about 83.9 mAh g −1 , an average cell discharge voltage of 2.35 V and a specific capacity retention of around 97% after 40 cycles at 24 mA g −1 and 25 °C. Sluggish kinetics is a major challenge for iron-based sulfate electrode materials. Here, the authors report multiscale interface engineering to build continuous Na-ion transfer channels at all length scales by designing ionic conductors inside bulk and low-electron-density exposed crystal surfaces.

The α-molybdenum trioxide has attracted much attention for proton storage owing to its easily modified bilayer structure, fast proton insertion kinetics, and high theoretical specific capacity. However, the fundamental science of the proton insertion mechanism in α-molybdenum trioxide has not been fully understood. Herein, we uncover a three-proton intercalation mechanism in α-molybdenum trioxide using a specially designed phosphoric acid based liquid crystalline electrolyte. The semiconductor-to-metal transition behavior and the expansion of the lattice interlayers of α-molybdenum trioxide after trapping one mole of protons are verified experimentally and theoretically. Further investigation of the morphology of α-molybdenum trioxide indicates its fracture behavior upon the proton intercalation process, which creates diffusion channels for hydronium ions. Notably, the observation of an additional redox behavior at low potential endows α-molybdenum trioxide with an improved specific discharge capacity of 362 mAh g −1 . The proton insertion mechanism in α-molybdenum trioxide remains incompletely elucidated. Herein, the authors uncover a three-proton intercalation mechanism within α-molybdenum trioxide using a specially designed electrolyte, which endows α-molybdenum trioxide with an improved specific discharge capacity.

Prussian blue analogues (PBAs) are appealing active materials for post-lithium electrochemical energy storage. However, PBAs are not generally suitable for non-aqueous Li-ion storage due to their instability upon prolonged cycling. Herein, we assess the feasibility of PBAs with various lithium content for non-aqueous Li-ion storage. We determine the crystal structure of the lithiated PBAs via neutron powder diffraction measurements and investigate the influence of water on structural stability and Li-ion migration through operando X-ray diffraction measurements and bond valence simulations. Furthermore, we demonstrate that a positive electrode containing Li 2-x FeFe(CN) 6 ⋅nH 2 O (0 ≤ x ≤ 2) active material coupled with a Li metal electrode and a LiPF 6 -containing organic-based electrolyte in coin cell configuration delivers an initial discharge capacity of 142 mAh g −1 at 19 mA g −1 and a discharge capacity retention of 80.7% after 1000 cycles at 1.9 A g −1 . By replacing the lithium metal with a graphite-based negative electrode, we also report a coin cell capable of cycling for more than 370 cycles at 190 mA g −1 with a stable discharge capacity of about 105 mAh g −1 and a discharge capacity retention of 98% at 25 °C. Prussian blue analogues (PBAs) are appealing materials for aqueous Na- and K- ion batteries but are limited for non-aqueous Li-ion storage. Here, the authors report the synthesis of various lithiated PBAs and discuss critical factors for improving the non-aqueous electrochemical storage of Li ions.

Aqueous zinc batteries are ideal candidates for grid-scale energy storage because of their safety and low-cost aspects. However, the production of large-format aqueous Zn batteries is hindered by electrolyte consumption, hydrogen gas evolution and accumulation, and Zn dendrites growth. To circumvent these issues, here we propose an “open” pouch cell design for large-format production of aqueous Zn batteries, which can release hydrogen gas and allow the refilling of the electrolyte components consumed during cell cycling. The cell uses a gel electrolyte containing crosslinked kappa (k)-carrageenan and chitosan. It bonds water molecules and hinders their side reaction with Zn, preventing electrolyte leakage and fast evaporation. As a proof-of-concept, we report the assembly and testing of a Zn | |Zn x V 2 O 5 ·nH 2 O multi-layer “open” pouch cell using the carrageenan/chitosan gel electrolyte, which delivers an initial discharge capacity of 0.9 Ah and 84% capacity retention after 200 cycles at 200 mA g ‒1 , 370 kPa and 25 °C. The production of large-format aqueous Zn batteries is hindered by electrolyte consumption, hydrogen gas evolution and Zn dendrites growth during cycling. Here, the authors propose a specific pouch cell design capable of releasing hydrogen gas and refilling the electrolyte components.

Potassium-ion batteries are a compelling technology for large scale energy storage due to their low-cost and good rate performance. However, the development of potassium-ion batteries remains in its infancy, mainly hindered by the lack of suitable cathode materials. Here we show that a previously known frustrated magnet, KFeC 2 O 4 F, could serve as a stable cathode for potassium ion storage, delivering a discharge capacity of ~112 mAh g −1 at 0.2 A g −1 and 94% capacity retention after 2000 cycles. The unprecedented cycling stability is attributed to the rigid framework and the presence of three channels that allow for minimized volume fluctuation when Fe 2+ /Fe 3+ redox reaction occurs. Further, pairing this KFeC 2 O 4 F cathode with a soft carbon anode yields a potassium-ion full cell with an energy density of ~235 Wh kg −1 , impressive rate performance and negligible capacity decay within 200 cycles. This work sheds light on the development of low-cost and high-performance K-based energy storage devices. The abundance and low cost of potassium makes potassium batteries a promising technology for large scale energy storage. Here the authors apply a previously known frustrated magnet, KFeC 2 O 4 F, as the cathode in which the unique structure and Fe 2+ /Fe 3+ redox enable excellent cycling stability.

Paring seawater electrolyte with zinc metal electrode has emerged as one of the most sustainable alternative solutions for offshore stationary energy storages owing to the intrinsic safety, extremely low cost, and unlimited water source. However, it remains a substantial challenge to stabilize zinc metal negative electrode in seawater electrolyte, given the presence of chloride ions and complex cations in seawater. Here, we reveal that chloride pitting initiates negative electrode corrosion and aggravates dendritic deposition, causing rapid battery failure. We then report a charge gradient negative electrode interface design that eliminates chloride-induced corrosion and enables a sustainable zinc plating/stripping performance beyond 1300 h in natural seawater electrolyte at 1 mA cm -2 /1 mAh cm -2 . The gradually strengthened negative charges formed via diffusion-controlled electrostatic complexation of biomass-derived polysaccharides serve to repel the unfavorable accumulation of chloride ions while simultaneously accelerating the diffusion of zinc ions. The seawater-based Zn | |NaV 3 O 8 ·7H 2 O cell delivers an initial areal discharge capacity of 5 mAh cm -2 and operates over 500 cycles at 500 mA g -1 . Seawater electrolytes provide a sustainable option for aqueous zinc batteries but challenge the stability of zinc metal electrodes. Here, authors elucidate the zinc electrode failure mechanisms and propose a charge gradient interface strategy to stabilize the zinc electrode in seawater electrolytes.

Solid polymer electrolytes are considered among the most promising candidates for developing practical solid-state sodium batteries. However, moderate ionic conductivity and narrow electrochemical windows hinder their further application. Herein, inspired by the Na + /K + conduction in biological membranes, we report a (–COO – )-modified covalent organic framework (COF) as a Na-ion quasi-solid-state electrolyte with sub-nanometre-sized Na + transport zones (6.7–11.6 Å) created by adjacent –COO – groups and COF inwalls. The quasi-solid-state electrolyte enables selective Na + transport along specific areas that are electronegative with sub-nanometre dimensions, resulting in a Na + conductivity of 1.30×10 –4 S cm –1 and oxidative stability of up to 5.32 V (versus Na + /Na) at 25 ± 1 °C. Testing the quasi-solid-state electrolyte in Na||Na 3 V 2 (PO 4 ) 3 coin cell configuration demonstrates fast reaction dynamics, low polarization voltages, and a stable cycling performance over 1000 cycles at 60 mA g –1 and 25 ± 1 °C with a 0.0048% capacity decay per cycle and a final discharge capacity of 83.5 mAh g −1 . Quasi-solid-state polymer electrolytes are ideal candidates for practical secondary battery applications. Here, the authors propose a negatively charged (–COO – )-modified covalent organic framework as a Na-ion quasi-solid-state electrolyte with sub-nanometric Na-ion transport zones.