High-voltage lithium metal batteries (LMBs) utilizing lithium-rich manganese oxide (LRMO) cathodes offer a promising way towards high energy densities yet remain impractical when operating at high voltages, primarily due to electrolyte instability at interfaces of LRMO and Li metal electrodes. In this study, we report stable cycling of LRMO-based LMBs under ultra-high voltage conditions of 5 V via employing an aggregation-enhanced solvation electrolyte (AESE). The AESE features a solvation structure dominated by anion-wrapped aggregates, in which Li⁺ ions are under a coordination environment surrounded by numerous anions. With such a solvation structure, the AESE concurrently stabilizes the Li metal anode and LRMO cathode. It promotes a protective cathode–electrolyte interphase on LRMO and an inorganic-rich interphase on Li metal, collectively suppressing electrolyte oxidation and transition metal dissolution. Thereby, Li||LRMO cells can deliver exceptional cycling stability at 5 V, retaining >87% capacity after 200 cycles. It also sustains stable operation for 100 cycles at −20 °C. This work demonstrates the electrolyte design for 5 V-class LMBs capable of reliable operation under low-temperature conditions.

Because of the superiority of low cost and high theoretical capacity, sodium metal batteries are considered an attractive option for high energy storage. However, the uncontrollable and random deposition of Na tends to expedite the formation of Na dendrites and increases the risk of thermal runaway. The method of preplant sodiophilic sites can induce the lateral deposition of Na instead of sharp dendrite emergence. Here, we introduce the sodiophilic V₂O₃ particles to form a protective layer on Na surface (Na/V₂O₃). The high Na ion adsorption energy and low nucleation overpotential of Na/V₂O₃ facilitate the diffusion of Na ions and homogeneous Na deposition, which can work well in cubing dendrite development. Thus, the symmetrical cell (Na/V₂O₃||Na/V₂O₃) can stably operate for 670 h at 0.5 mA·cm⁻²/1 mAh·cm⁻² with a smaller voltage hysteresis (less than 100 mV). Moreover, full cell constructed by coupling Na/V₂O₃ anode with Na₃V₂(PO₄)₃ cathode displays an outstanding rate performance, maintaining a high capacity of 70 mAh·g⁻¹ at 30 C. On the basis of the design of sodiophilic protection layer, a dendrite-free, outstanding rate performance, and long lifespan sodium metal battery is realized.

Metal phosphides have shown great application potential as anode for sodium-ion batteries (NIBs) owing to high theoretical capacity, suitable operation voltage and abundant resource. Unfortunately, the application of NiP₂ anode is severely impeded by low practical capacity and fast capacity decay due to the huge volume variation and low reactivity of internal phosphorus (P) component towards Na⁺. Herein, electronic structure modulation of NiP₂ via heteroatoms doping and introducing vacancies defects to enhance Na⁺ adsorption sites and diffusion kinetics is successfully attempted. The as-synthesized three-dimensional (3D) bicontinuous carbon matrix decorated with well-dispersed fluorine (F)-doped NiP₂ nanoparticles (F-NiP₂@carbon nanosheets) delivers a high reversible capacity (585 mAh·g⁻¹ at 0.1 A·g⁻¹) and excellent long cycling stability (244 mAh·g⁻¹ over 1,000 cycles at 2 A·g⁻¹) when tested as anode in NIBs. Density functional theory (DFT) calculations reveal that F doping in NiP₂ induces the formation of P vacancies with increased Na⁺ adsorption energy and accelerates the alloying of internal P component. The F-NiP₂@carbon nanosheets//Na₃V₂(PO₄)₃ full cell is evaluated showing stable long cycling life. The heteroatoms doping-induced dual defects strategy opens up a new way of metal phosphides for sodium storage.

Sodium-ion batteries (SIBs) have become an auspicious candidate for large-scale energy storage by cause of low cost, natural abundance, and similar working principle with lithium-ion batteries (LIBs). At present, there is an urgent need to explore superior anode materials with rapid and stable sodiation/desodiation. Herein, 3D self-assembled VS₄ curly nanosheets hierarchitectures (VS₄-CN-Hs) are developed for SIB anodes, where VS₄ possesses a large theoretical sodium storage capacity, and the building block of nanosheets has large exposed surface area to the electrolyte as well as the constructed hierarchitectures can provide abundant buffer space to alleviate the volume expansion. As a result, VS₄-CN-Hs anode possesses excellent electrochemical performance under a wide voltage window of 0.01–3.0 V, such as high reversible capacity of 863 mA h g⁻¹ at 0.1 A g⁻¹, marvelous rate feature (444 mA h g⁻¹ at 10 A g⁻¹), and extralong cycle stability (386 mA h g⁻¹ after 1000 times at 5 A g⁻¹).

The use of TiO₂ as an anode in rechargeable sodium-ion batteries (NIBs) is hampered by intrinsic low electronic conductivity of TiO₂ and inferior electrode kinetics. Here, a high-performance TiO₂ electrode for NIBs is presented by designing a multichannel porous TiO₂ nanofibers with well-dispersed Cu nanodots and Cu²⁺-doping derived oxygen vacancies (Cu-MPTO). The in-situ grown well-dispersed copper nanodots of about 3 nm on TiO₂ surface could significantly enhance electronic conductivity of the TiO₂ fibers. The one-dimensional multichannel porous structure could facilitate the electrolyte to soak in, leading to short transport path of Na⁺ through carbon toward the TiO₂ nanoparticle. The Cu²⁺-doping induced oxygen vacancies could decrease the bandgap of TiO₂, resulting in easy electron trapping. With this strategy, the Cu-MPTO electrodes render an outstanding rate performance for NIBs (120 mAh·g^-1 at 20 C) and a superior cycling stability for ultralong cycle life (120 mAh·g^-1 at 20 C and 96.5% retention over 2, 000 cycles). Density functional theory (DFT) calculations also suggest that Cu²⁺ doping can enhance the conductivity and electron transfer of TiO₂ and lower the sodiation energy barrier. This strategy is confirmed to be a general process and could be extended to improve the performance of other materials with low electronic conductivity applied in energy storage systems.

Germanium-based oxide has been found to be a promising high-capacity anode material for lithium-ion batteries (LIBs). However, it exhibits poor electrochemical performance because of the drastic volume change during cycling. Herein, we designed porous Ge-Fe bimetal oxide nanowires (Ge-Fe-O_x-700 NWs) by a large-scale and facile solvothermal reaction. When used as the anode material for LIBs, these Ge-Fe-O_x-700 NWs exhibited superior electrochemical performance (~ 1, 120 mAh·g^-1 at a current density of 100 mA·g^-1) and good cycling performance (~ 750 mAh·g^-1 after 50 cycles at a current density of 100 mA·g^-1). The improved performance is due to the small NW diameter, which allows for better accommodation of the drastic volume changes and zero-dimensional nanoparticles, which shorten the diffusion length of ions and electrons.

As a typical two-dimensional transition metal dichalcogenide, molybdenum disulfide (MoS₂) is considered a potential anode material for sodium-ion batteries (NIBs), due to its relatively high theoretical capacity (~ 670 mAh·g^–1). However, the low electrical conductivity of MoS₂ and its dramatic volume change during charge/discharge lead to severe capacity degradation and poor cycling stability. In this work, we developed a facile, scalable, and effective synthesis method to embed nanosized MoS₂ into a thin film of three-dimensional (3D)-interconnected carbon nanofibers (CNFs), producing a MoS₂/CNFs film. The free-standing MoS₂/CNFs thin film can be used as anode for NIBs without additional binders or carbon black. The MoS₂/CNFs electrode exhibits a high reversible capacity of 260 mAh·g^–1, with an extremely low capacity loss of 0.05 mAh·g^–1 per cycle after 2, 600 cycles at a current density of 1 A·g^–1. This enhanced sodium storage performance is attributed to the synergistic effect and structural advantages achieved by embedding MoS₂ in the 3D-interconnected carbon matrix.

A flexible and free-standing multichannel carbon nanofiber (MCNF) film electrode was fabricated through electrospinning and carbonization. After high-temperature treatment of MCNFs in vacuum, the obtained fibers (MCNFs-V) had a dilated interlayer spacing of graphene sheets (0.398 nm) and an ultra-low specific surface area (15.3 m²/g). When used as an anode for sodium-ion batteries, the MCNFs-V showed a discharge plateau below 0.1 V, and sodium was intercalated into the stacked graphene sheets layers during the sodiation process. The MCNFs-V exhibited a reversible and high specific capacity of 222 mAh/g at a current density of 0.1 A/g after 100 cycles and excellent long-term cycling stability, which was superior to that of MCNFs. The improved sodium storage performance was attributed to the unique microstructure of the MCNFs-V with an enlarged interlayer spacing of graphene sheets for sodium intercalation. The MCNFs-V electrode holds great promise as an anode material for commercial sodium-ion batteries.

Sb is considered a promising anode material for high-performance sodium-ion batteries (NIBs) owing to its high theoretical specific capacity (660 mAh·g⁻¹). However, Sb shows a very large volume change (~200%) during sodiation and desodiation, leading to poor electrochemical performance. Here, we designed and tested a sandwich-like graphene-supported Sb nanocomposite (denoted Sb@RGO@Sb), in which ultrafine Sb nanoparticles are uniformly anchored on a reduced graphene oxide (RGO) surface. The ultrafine Sb nanocrystals anchored on the RGO surface minimize the aggregation of Sb and inhibit restacking of the RGO sheets, leading to a minimum transport length for both ions and electrons. The graphene layer not only accommodates the large volume variation of Sb during cycling but also promotes the electron conductivity of the whole electrode. Owing to its unique structure, this sandwich-like composite exhibits superior sodium storage properties.