High Performance 3D Si/Ge Nanorods Array Anode Buffered by TiN/Ti Interlayer for Sodium‐Ion Batteries

3D micro/nanobatteries in high energy and power densities are drawing more and more interest due to the urgent demand of them in integrating with numerous micro/nanoscale electronic devices, such as smart dust, miniaturized sensors, actuators, BioMEMS chips, and so on. In this study, the electrochemical performances of 3D hexagonal match‐like Si/Ge nanorod (NR) arrays buffered by TiN/Ti interlayer, which are fabricated on Si substrates by a cost‐effective, wafer scale, and Si‐compatible process are demonstrated and systematically investigated as the anode in sodium‐ion batteries. The optimized Si/TiN/Ti/Ge composite NR array anode displays superior areal/specific capacities and cycling stability by reason of their favorable 3D nanostructures and the effective conductive layers of TiN/Ti thin films. Sodium‐ion insertion behaviors are experimentally investigated in postmorphologies and elemental information of the cycled composite anode, and theoretically studied by the first principles calculation upon the adsorption and diffusion energies of sodium in Ge unit cell. The preferential diffusion of sodium in Ge structure over in Si lattice is evidently proved. The successful configuration of these distinctive wafer‐scale Si‐based Na‐ion micro/nanobattery anodes can provide insight into exploring and designing new Si/Ge‐based electrode materials, which can be integrated into micro‐electronic devices as on chip power systems in the future.     

Rational Designs for Lithium-Sulfur Batteries with Low Electrolyte/Sulfur Ratio

Lithium-sulfur batteries (LSBs) are considered a promising next-generation energy storage device owing to their high theoretical energy density. However, their overall performance is limited by several critical issues such as lithium polysulfide (PS) shuttles, low sulfur utilization, and unstable Li metal anodes. Despite recent huge progress, the electrolyte/sulfur ratio (E/S) used is usually very high (≥20 µL mg⁻¹), which greatly reduces the practical energy density of devices. To push forward LSBs from the lab to the industry, considerable attention is devoted to reducing E/S while ensuring the electrochemical performance. To date, however, few reviews have comprehensively elucidated the possible strategies to achieve that purpose. In this review, recent advances in low E/S cathodes and anodes based on the issues resulting from low E/S and the corresponding solutions are summarized. These will be beneficial for a systematic understanding of the rational design ideas and research trends of low E/S LSBs. In particular, three strategies are proposed for cathodes: preventing PS formation/aggregation to avoid inadequate dissolution, designing multifunctional macroporous networks to address incomplete infiltration, and utilizing an imprison strategy to relieve the adsorption dependence on specific surface area. Finally, the challenges and future prospects for low E/S LSBs are discussed.     

Lithium-Substituted Tunnel/Spinel Heterostructured Cathode Material for High-Performance Sodium-Ion Batteries

Sodium manganese oxides as promising cathode materials for sodium-ion batteries (SIBs) have attracted interest owing to their abundant resources and potential low cost. However, their practical application is hindered due to the manganese disproportionation associated with Mn³⁺, resulting in rapid capacity decline and poor rate capability. Herein, a Li-substituted, tunnel/spinel heterostructured cathode is successfully synthesized for addressing these limitations. The Li dopant acts as a pillar inhibiting unfavorable multiphase transformation, improving the structural reversibility, and sodium storage performance of the cathode. Meanwhile, the tunnel/spinel heterostructure provides 3D Na⁺ diffusion channels to effectively enhance the redox reaction kinetics. The optimized [Na_0.396Li_0.044][Mn_0.97Li_0.03]O₂ composite delivers an excellent rate performance with a reversible capacity of 97.0 mA h g^–1 at 15 C, corresponding to 82.5% of the capacity at 0.1 C, and a promising cycling stability over 1200 cycles with remarkable capacity retention of 81.0% at 10 C. Moreover, by combining with hard carbon anodes, the full cell demonstrates a high specific capacity and favorable cyclability. After 200 cycles, the cell provides 105.0 mA h g^–1 at 1 C, demonstrating the potential of the cathode for practical applications. This strategy might apply to other sodium-deficient cathode materials and inform their strategic design.     

A Novel 3D Li/Li9Al4/Li-Mg Alloy Anode for Superior Lithium Metal Batteries

Lithium metal has been recognized as the most promising anode material due to its high capacity and low electrode potential. However, the high reactivity, infinite volume variation, and uncontrolled dendrites growth of Li during long-term cycling severely limit its practical applications. To address these issues, herein, a novel 3D Al/Mg/Li alloy (denoted as AM-Li) anode is designed and constructed by a facile smelting-rolling strategy, which improves the surface stability, electrochemical cycling stability, and rate capability in lithium metal batteries. Specifically, the optimized AM-Li|AM-Li symmetric cell exhibits low polarization voltage (< 20 mV) and perfect cycling stability at 1 mA cm⁻²-1 mAh cm⁻² for more than 1600 h. Moreover, the AM-Li|NCM811 full cell exhibits superior rate capability up to 5 C and excellent cyclability for 100 cycles at 0.5 C with a high capacity retention of 90.8%. The realization of lithium-poor or lithium-free anode materials will be a major development trend of anode materials in the future. Therefore, the research shows that the construction of 3D alloy framework is beneficial to improve the cycling stability of Li anodes by suppressing the volume expansion effect and Li dendrite growth, which will promote the further development of lithium-poor metal anodes.     

Voltage Hysteresis in Transition Metal Oxide Cathodes for Li/Na-Ion Batteries

The pursuit of rechargeable batteries with high energy density has triggered enormous efforts in developing cathode materials for lithium/sodium (Li/Na)-ion batteries considering their extremely high specific capacity. Many materials are being researched for battery applications, and transition metal oxide materials with remarkable electrochemical performance stand out among numerous cathode candidates for next-generation battery. Notwithstanding the merits, daunting challenges persist in the quest for further battery developments targeting lower cost, longer lifespan, improved energy density and enhanced safety. This is, in part, because the voltage hysteresis between the charge and discharge cycles, is historically avoided in intercalation electrodes because of its association with structural disorder and electrochemical irreversibility. Given the great potential of these materials for next-generation batteries, a review of the recent understanding of voltage hysteresis is timely. This review presents the origin of their undesirable behaviors and materials design criteria to mitigate them by integrating various schools of thought. A large amount of progressive characterization techniques related to voltage hysteresis are summarized from the literature, along with the corresponding measurable range used in their determination. Finally, promising design trends with eliminated voltage hysteresis are tentatively proposed to revive these important cathode materials toward practical applications.     

Radial Pores in Nitrogen/Oxygen Dual-Doped Carbon Nanospheres Anode Boost High-Power and Ultrastable Potassium-Ion Batteries

Constructing electrode materials with fast ions and electrons transport channels is an effective solution to achieve high-power-density and long-cycle potassium-ion batteries (PIBs). Herein, completely opening radial pores in N/O dual-doped carbon nanospheres (RPCNSs) are constructed as anode for high-power PIBs. The RPCNS with hierarchical structure (micro/meso/macropores and radial channels) and N/O dual-doping permits speedy ions and electrons transportation within the carbon nanospheres anode, achieving a reversible capacity of 346 mAh g⁻¹ at 50 mA g⁻¹ after 360 cycles and long-term cycling life over 2000 cycles without obvious capacity attenuation. The in situ Raman and kinetic analysis (in situ electrochemical impedance spectroscopy and galvanostatic intermittent titration) suggest that the exquisitely designed pore structure and heterodoping enable highly reversible electrochemical reaction and fast de/intercalation kinetics. Moreover, the full cells packaged with RPCNS anode can be fully charged in 10 s and exhibit the highest charge power density of 24 866 W kg⁻¹ and longest cycling endurance of 5000 cycles in reported PIBs. The unique structural engineering provides a new way for high-power density potassium-ion storage devices.     

Ultrafast Laser-Induced Cathode/Electrolyte Interphase for High-Voltage Poly(Ethylene Oxide)-Based Solid Batteries

Poly(ethylene oxide) (PEO)-based solid polymer electrolyte promises interfacial compatibility with the high-capacity metallic anodes in all-solid-state batteries (ASSBs). However, the prototype construction is severely hindered by the parasitic ohmic resistance at the electrode-electrolyte interface, insufficient ionic pathway of the high loading cathode, as well as the PEO oxidation tendency at the high voltage. Herein, a laser-assisted strategy is presented toward ultra-efficient cathode modification (completes within 240 s) by constructing continuous, multi-scale artificial cathode/electrolyte interface (CEI). The tailorable, yet localized temperature gradient induced by the pulsed laser beam can customize the CEI species from the target precursor salts for the on-demand protection purpose. Derived from the tris(trimethylsilyl)phosphate, the proof-of-concept model achieves phosphorus-rich, ion-diffusion network across the high-mass-loading LiNi_0.8Co_0.1Mn_0.1O₂ cathode, which enables the high-rate operation of the ASSBs prototype as well as the extended shelf life at the oxidized idling state. Transmission-mode operando X-ray phase tracking unravels the electrochemical stability origin at the cathode/PEO interface due to the insulation of electron shuttling, where the layered to spinel phase transition and the lattice oxygen release are alleviated. This generic, readily tailorable, highly-efficient laser processing strategy thus provides unprecedented opportunities to secure the varieties of energy-dense, polymer-based ASSBs.     

Engineering Molecular Polymerization for Template-Free SiOx/C Hollow Spheres as Ultrastable Anodes in Lithium-Ion Batteries

SiO_x/C composites with a void-reserving structure are promising anodes for lithium-ion batteries. However, the facile and controllable synthesis of uniformly dispersed SiO_x and carbon components, simultaneously incorporating ample voids, still remains a great challenge. Herein, a molecular polymerization strategy is devised to construct SiO_x/C hollow particles for lithium-ion batteries. 3-aminopropyltriethoxysilane and dialdehyde molecules are judiciously engineered as silicon and carbon precursors to produce the polymer hollow spheres (PHSs) through a one-step aldimine condensation without any template and additive. A range of PHSs is obtained using terephthalaldehyde, glutaraldehyde, and glyoxal as the crosslinkers, demonstrating the high tunability of the strategy. Importantly, in situ pyrolysis of the PHSs warrants the homogeneous incorporation of SiO_x ( < 5 nm) in carbon hollow capsids at a nanocluster scale. The obtained SiO_x/C hollow spheres exhibit excellent Li⁺-ion storage behaviors, including cycling lifespan, coulombic efficiency, and rate performance. The superior performance is attributed to the well-dispersed SiO_x nanoclusters in carbon substrate and the hollow structure. This molecular polymerization approach not only enables Si-based hollow composites effective and scalable anode materials but also opens up a new avenue for the controllable synthesis of template-free hollow architectures.     

Confined Sulfur in Microporous Carbon Renders Superior Cycling Stability in Li/S Batteries

The use of sulfur in the next generation Li‐ion batteries is currently precluded by its poor cycling stability caused by irreversible Li₂S formation and the dissolution of soluble polysulfides in organic electrolytes that leads to parasitic cell reactions. Here, a new C/S cathode material comprising short‐chain sulfur species (predominately S₂) confined in carbonaceous subnanometer and the unique charge mechanism for the subnano‐entrapped S₂ cathodes are reported. The first charge–discharge cycle of the C/S cathode in the carbonate electrolyte forms a new type of thiocarbonate‐like solid electrolyte interphase (SEI). The SEI coated C/S cathode stably delivers ≈600 mAh g^?1 capacity over 4020 cycles (0.0014% loss cycle^?1) at ≈100% Coulombic efficiency. Extensive X‐ray photoelectron spectroscopy analysis of the discharged cathodes shows a new type of S₂ species and a new carbide‐like species simultaneously, and both peaks disappear upon charging. These data suggest a new sulfur redox mechanism involving a separated Li⁺/S^2? ion couple that precludes Li₂S compound formation and prevents the dissolution of soluble sulfur anions. This new charge/discharge process leads to remarkable cycling stability and reversibility.     

A Strategy for Polysulfides/Polyselenides Protection Based on Co9S8@SiO2/C Host in Na-SeS2 Batteries

To obtain unbroken sulfides with delicate morphology from metal–organic frameworks (MOFs), a method for in situ growth of SiO₂ protective layers on the surface of MOFs is proposed. This strategy can be successfully expanded to a variety of MOFs (ZIF-67, Cu-MOF, ZIF-8, and PBA). Importantly, room-temperature Na-SeS₂ batteries with Co₉S₈@SiO₂/C prepared from ZIF-67 as cathode host are assembled. Due to the hollow structure that can relieve the volume expansion and the co-adsorption of sodium polysulfides/sodium polyselenides by Co₉S₈@SiO₂/C, the SeS₂/Co₉S₈@SiO₂/C cathode shows excellent rate performance and Coulombic efficiency. In addition, ex situ X-ray diffraction and in situ Raman results show that S₈ and Se₈ are generated after the discharge of SeS₂, and Se₈ is preferentially oxidized during charging.     

Toward Critical Electrode/Electrolyte Interfaces in Rechargeable Batteries

The electrode/electrolyte interface plays a critical role in stabilizing the cycling performance and prolonging the service life of rechargeable batteries to meet the sustainable energy requirements of the mobile society. The understanding of interfaces is still at the preliminary stage due to the limited research techniques and variable properties with time and potential. Herein, the latest developments focused on the interfaces in rechargeable systems including the cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) are reviewed. The possible formation mechanisms of the electrode/electrolyte interface are discussed, followed by the introduction of two key influencing factors, specific adsorption and solvated coordinate structure, which will dominate the formation of the interface. Finally, the structure and chemical composition of the interface as well as the possible transport mechanism of lithium ions in the interface and the strategies to regulate the pathway through the interface are presented in detail. This work sheds light on the fundamental understanding of the interface and provides rational scientific principles in designing the electrode/electrolyte interface and inspires the rational design of long‐term cycling rechargeable batteries.