Achieving high critical current density in practical superconductors for high-field applications requires well-connected fine grains decorated with nano-scale crystalline defects to immobilize magnetic vortices. In compounds with rigid crystal lattices, however, grain refinement is usually accompanied by the release of stored strain energy rather than the retention of defects. Here, we demonstrate a scalable fluid-assisted milling strategy to produce high-purity Ba_1–xK_xFe₂As₂ precursor powders with uniform grains. Unlike dry milling that induces catastrophic fracture through breaking Fe–As covalent bonds, the liquid medium buffers impact energy and promotes shear-dominated deformation. This shear-dominated process selectively disrupts the weaker Ba–As ionic bonds, inducing a concerted lattice twist around the [001] axis and triggering the self-organization of interwoven screw dislocation networks. The dislocations with a density 2–4 orders of magnitude higher than those in conventional ceramics serve as strong pinning centers for magnetic vortices. Together with better grain connectivity and texture, the tapes fabricated from optimally milled powders exhibit a 50% enhancement in critical current density, reaching 1.45 × 10⁵ A/cm² at 4.2 K and 10 T. Our results establish fluid-assisted milling as a practical route to synergistically refine grains and construct strong pinning landscapes, offering a scalable pathway to high-performance iron-based superconductors.

As a promising transition metal oxide, Co₃O₄ is considered a low-cost anode material in lithium-ion capacitors (LICs) due to its sizeable theoretical capacity and excellent electrochemical reversibility. However, its inherently inferior electrical conductivity and huge volume expansion upon long-term operation often cause reduced energy storage and slow rate capability during lithiation/delithiation in LICs. To overcome these limitations, we present a simple annealing approach that leverages both vacancy chemistry and surface engineering to refine the physiochemical structure of Co₃O₄ nanoboxes with adjustable thickness of CoO layers on the surface, enabling precise microstructural control over lithium storage performance. Our analysis shows that electrochemical lithiation of Co₃O₄ leads to an increased generation of oxygen vacancies at octahedral Co²⁺ sites, facilitated by Co²⁺–ligand interactions. Theoretical calculations confirm that these vacancies induce a new electronic density of state in the bandgap and create localized charge imbalances, considerably enhancing electrical conductivity and accelerating faradaic reactions. With this vacancy-engineered structure, Co₃O₄ nanoboxes demonstrate an impressive reversible specific capacity of 917 mAh/g after 100 cycles. Furthermore, LICs based on the Co₃O₄ anode achieve an exceptional power density up to 33.6 kW/kg together with an energy density of 124.1 Wh/kg. This study provides a robust strategy for vacancy engineering in electrode materials to boost the electrochemical energy storage performances.

Lithium-ion capacitors (LICs) offer higher power density and longer cycle life compared to lithium-ion batteries, and greater energy density than supercapacitors, making them ideal for applications requiring both high energy and power density. However, during high-rate charging, LIC anodes may suffer from lithium plating, a critical issue that remains unaddressed. To date, no direct analytical technique exists to study lithium plating behavior on LIC anodes. This study is the first to employ a 3-electrode pouch-type LICs, using differential analysis of the anode potential rather than the traditional terminal voltage approach, to accurately detect the charging rates at which lithium plating begins. We employed differential charging voltage (DCV), Coulombic efficiency (CE), and voltage relaxation profile (VRP) methods to comprehensively analyze lithium plating behavior. The feasibility of indirectly detecting lithium plating was validated by applying the CE and VRP methods to high-capacity 1,100 F LICs. The study found that lithium plating in LICs begins at a charging current of 20 C. The lithium deposited at currents below 50 C is reversible, while at currents above 50 C, irreversible dead lithium is formed. Furthermore, the study identified two reverse reactions following lithium deposition on the anode: lithium stripping and lithium intercalation. For soft carbon anodes, the potential difference between lithium stripping and intercalation was approximately 20 mV under relaxation conditions, and about 45 mV under constant voltage conditions. This research provides critical theoretical insights and practical guidance for optimizing LIC charging strategies.

Carbon nanofiber (CNF) was widely utilized in the field of electrochemical energy storage due to its superiority of conductivity and mechanics. However, CNF was generally prepared at relatively high temperature. Herein, nitrogen-doped hard carbon nanofibers (NHCNFs) were prepared by a low-temperature carbonization treatment assisted with electrospinning technology. Density functional theory analysis elucidates the incorporation of nitrogen heteroatoms with various chemical states into carbon matrix would significantly alter the total electronic configurations, leading to the robust adsorption and efficient diffusion of Na atoms on electrode interface. The obtained material carbonized at 600 °C (NHCNF-600) presented a reversible specific capacity of 191.0 mAh g⁻¹ and no capacity decay after 200 cycles at 1 A g⁻¹. It was found that the sodium-intercalated degree had a correlation with the electrochemical impedance. A sodium-intercalated potential of 0.2 V was adopted to lower the electrochemical impedance. The constructed sodium-ion capacitor with activated carbon cathode and presodiated NHCNF-600 anode can present an energy power density of 82.1 Wh kg⁻¹ and a power density of 7.0 kW kg⁻¹.

Lithium metal is a promising candidate for the promotion of the next generation high energy density batteries. The employment of ultrathin Li metal anode with controllable thickness could enable a higher efficiency of Li utilization. Herein, a simple method to fabricate free-standing 10 μm ultrathin Li metal anode is developed in this work. A three-dimensional MnO_x-coated CNT framework is constructed through a facile hydrothermal process, utilizing as a host for molten Li infusion, which could not only put forward a simple strategy to modulate the thickness of Li metal film but also restricts the volume expansion. The abundant MnO_x nanoparticles acting as lithiophilic sites reduce the Li nucleation barrier and optimize the electrochemical kinetics at the anode/electrolyte interface. As a result, the ultrathin Li composite anode exhibits a superior lifespan expanded to 2000 cycles in a symmetric cell, as well as a better capacity and rate capability than that of bare Li anode in full cell, fulfilling the requirements of high energy density and stable cycling life. Furthermore, a wave-shaped Li metal pouch cell based on the ultrathin Li composite anode is assembled that exhibits remarkable mechanical bending toleration and cyclic stability, demonstrating large potential application in the field of flexible wearable devices.