Half and full sodium-ion batteries based on maize with high-loading density and long-cycle life

Sodium Stoichiometry Tuning of the Biphasic-Nax MnO2 Cathode for High-Performance Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are promising alternatives for large-scale energy storage owing to the rich resource and cost effectiveness. However, there are limitations of suitable low-cost, high-rate cathode materials for fast charging and high-power delivery in grid systems. Herein, a biphasic tunnel/layered 0.80Na0.44 MnO2 /0.20Na0.70 MnO2 (80T/20L) cathode delivering exceptional rate performance through subtly regulating the sodium and manganese stoichiometry is reported. It delivers a reversible capacity of 87 mAh g-1 at 4 A g-1 (33 C), much higher than that of tunnel Na0.44 MnO2 (72 mAh g-1 ) and layered Na0.70 MnO2 (36 mAh g-1 ). It proves that the one-pot synthesized 80T/20L is able to suppress the deactivation of L-Na0.70 MnO2 under air-exposure, which improves the specific capacity and cycling stability. Based on electrochemical kinetics analysis, the electrochemical storage of 80T/20L is mainly based on pseudocapacitive surface-controlled process. The thick film of 80T/20L cathode (a single-side mass loading over 10 mg cm-2 ) also has superior properties of pseudocapacitive response (over 83.5% at a low sweep rate of 1 mV s-1 ) and excellent rate performance. In this sense, the 80T/20L cathode with outstanding comprehensive performance could meet the requirements of high-performance SIBs.

Antimony nanobelt asymmetric membranes for sodium ion battery

In this study, composite asymmetric membranes containing antimony (Sb) nanobelts are prepared via a straightforward phase inversion method in combination with post-pyrolysis treatment. Sb nanobelt asymmetric membranes demonstrate improved cyclability and specific capacity as the alloy anode of sodium ion battery compared to Sb nanobelt thin films without asymmetric porous structure. The unique structure can effectively accommodate the large volume expansion of Sb-based alloy anodes, prohibit the loss of fractured active materials, and aid in the formation of stable artificial solid electrolyte interphases as evidenced by an outstanding capacity retention of ∼98% in 130 cycles at 60 mA g^-1. A specific capacity of ∼600 mAh g^-1is obtained at 15 mA g^-1(1/40C). When the current density is increased to 240 mA g^-1, ∼80% capacity can be maintained (∼480 mAh g^-1). The relations among phase inversion conditions, structures, compositions, and resultant electrochemical properties are revealed through comprehensive characterization.

A comprehensive study of the multiple effects of Y/Al substitution on O3-type NaNi0.33Mn0.33Fe0.33O2 with improved cycling stability and rate capability for Na-ion battery applications

O3-NaNi0.33Mn0.33Fe0.33O2 layered oxide has attracted increasing attention as one of the most promising materials for Na-ion battery applications due to air stability and environmental friendliness, but the complex phase transitions and inferior cycling stability are extremely challenging to overcome. Cation substitution has been widely used to stabilize crystal structures and improve electrochemical performance for SIBs. Based on past experimental results, it was discovered that the transition metal-oxygen bond energy of the introduced dopant is an important factor for optimizing electrochemical performance. In this study, we validated our hypothesis that yttrium (Y)-which possesses high bond energy for oxygen-is most likely to be an ideal doping element by conducting a comparative study of substituting Mn in O3-NaNi0.33Mn0.33Fe0.33O2 layered oxide with aluminum (Al) and Y through elemental doping. As hypothesized, the electrochemical properties of NaNi0.33Mn0.33Fe0.33O2 have increased markedly by introducing a small amount of Y and Al, and the Y-doped materials showed superior rate performance and cycling stability due to enhanced Na+ diffusion reaction kinetics and layered structure stability. Furthermore, the substitution of Y for Mn can improve thermal stability and alleviate phase transformations. The improvement mechanism of Y substitution can be attributed to a larger d-spacing and stronger metal-oxygen bond. These results suggest that structural modulation is an effective strategy to reinforce electrochemical properties of layered oxides and provides some guidance about designing promising electrode materials.

Mega High Utilization of Sodium Metal Anodes Enabled by Single Zinc Atom Sites

Low utilization of active metallic sodium (Na) and uncontrollable growth of Na dendrites remain significant challenges for high-performance Na metal batteries, which are limited to inefficient Na utilization (<1%) and shallow cycling conditions (0.25-1.0 mAh cm^-2). In this work, a kind of Na metal anode with record-high utilization and long-term cycling stability is reported, using carbon-substrate-supported nitrogen-anchored zinc (Zn) single atoms as a current collector. Single Zn atom sites which serve as a strong "magnet" for Na ions, can guide the metallic Na uniform nucleation and free from dendrite-induced short circuit. The nucleation overpotential of our strategy is essentially zero, where most of the reported modified substrates were greatly exceed 20 mV. Specifically, the Na anodes exhibit a high Na stripping/plating Coulombic efficiency with 99.8% over 350 cycles and a stable voltage response with small voltage hysteresis after cycling 1000 h. The full cell exhibits high Na utilization up to 100% and superior long-term cycling stability for more than 1000 cycles with excellent capacity retention. In terms of lifetime and Na utilization, the Na metal anodes based on our strategy significantly outperforms the reported state-of-the-art Na metal anodes. Moreover, this affords new insights into the controllable Na nucleation behavior and high Na utilization and sheds fresh light on atomic level design of an electrode for Na metal anodes.

N-Doped Carbon Nanofibers with Interweaved Nanochannels for High-Performance Sodium-Ion Storage

Although graphite materials have been applied as commercial anodes in lithium-ion batteries (LIBs), there still remain abundant spaces in the development of carbon-based anode materials for sodium-ion batteries (SIBs). Herein, an electrospinning route is reported to fabricate nitrogen-doped carbon nanofibers with interweaved nanochannels (NCNFs-IWNC) that contain robust interconnected 1D porous channels, produced by removal of a Te nanowire template that is coelectrospun within carbon nanofibers during the electrospinning process. The NCNFs-IWNC features favorable properties, including a conductive 1D interconnected porous structure, a large specific surface area, expanded interlayer graphite-like spacing, enriched N-doped defects and active sites, toward rapid access and transport of electrolyte and electron/sodium ions. Systematic electrochemical studies indicate that the NCNFs-IWNC exhibits an impressively high rate capability, delivering a capacity of 148 mA h g^-1 at current density of as high as 10 A g^-1 , and has an attractively stable performance over 5000 cycles. The practical application of the as-designed NCNFs-IWNC for a full SIBs cell is further verified by coupling the NCNFs-IWNC anode with a FeFe(CN)₆ cathode, which displays a desirable cycle performance, maintaining acapacity of 97 mA h g^-1 over 100 cycles.

Boosting High-Rate Sodium Storage Performance of N-Doped Carbon-Encapsulated Na3 V2 (PO4 )3 Nanoparticles Anchoring on Carbon Cloth

The further development of high-power sodium-ion batteries faces the severe challenge of achieving high-rate cathode materials. Here, an integrated flexible electrode is constructed by smart combination of a conductive carbon cloth fiber skeleton and N-doped carbon (NC) shell on Na₃ V₂ (PO₄ )₃ (NVP) nanoparticles via a simple impregnation method. In addition to the great electronic conductivity and high flexibility of carbon cloth, the NC shell also promotes ion/electron transport in the electrode. The flexible NVP@NC electrode renders preeminent rate capacities (80.7 mAh g^-1 at 50 C for cathode; 48 mAh g^-1 at 30 C for anode) and superior cycle performance. A flexible symmetric NVP@NC//NVP@NC full cell is endowed with fairly excellent rate performance as well as good cycle stability. The results demonstrate a powerful polybasic strategy design for fabricating electrodes with optimal performance.

2D ultrathin carbon nanosheets with rich N/O content constructed by stripping bulk chitin for high-performance sodium ion batteries

Two-dimensional (2D) nanomaterials hold considerable potential in reforming the energy storage performance, and the efficient production of high-performance 2D energy storage materials through facile and sustainable approaches is highly desirable. Herein, for the first time, large-area and ultrathin carbon nanosheets doped with N/O were constructed by stripping bulk chitin via a "top-down" method. On the basis of the specific layered structure composed of nanofibers, chitin samples after removing the protein and CaCO₃ could be efficiently exfoliated into nanosheets (CNs) via the hydrothermal method, which were then carbonized into N/O co-doped porous carbon nanosheets (CCNs). The CCNs with a thickness of about 3.8 nm retained the original nanosheet structure consisting of nanofibers, leading to a 2D structure with hierarchical porosities. When used as anode materials for sodium-ion batteries, the 2D porous nanostructures and abundant N/O doping of CCNs-600 (carbonized at 600 °C) enable a high reversible capacity of 360 mA h g^-1 at 50 mA g^-1, a good rate capability of 102 mA h g^-1 at 10 A g^-1, and an excellent cycling stability of 140 mA h g^-1 after 10 000 cycles at a high density of 5 A g^-1. Full cells consisting of a CCN anode and a Na₃V₂(PO₄)₃/C cathode exhibited favorable rate performance and cycling stability, showing potential application prospects in highly efficient energy storage systems.

Electrolytes and Electrolyte/Electrode Interfaces in Sodium-Ion Batteries: From Scientific Research to Practical Application

Sodium-ion batteries (SIBs) have drawn considerable interest as power-storage devices owing to the wide abundance of their constituents and low cost. To realize a high performance-price ratio, the cathode and anode materials must be optimized. As essential components of SIBs, electrolytes should have wide electrochemical windows, high thermal stability, and exceptional ionic conductivity. Therefore, improved electrolytes, based on various materials and compositions, are developed to meet the practical demands of SIBs, including organic electrolytes, ionic liquids, aqueous, solid electrolytes, and hybrid electrolytes. Although mature organic electrolytes are currently used in production, aqueous and solid electrolytes show advantages for future applications, as discussed here in detail. Current efforts in modifying electrolytes to optimize their interfacial compatibility with electrodes, leading to longer battery lifetimes and greater safety, are described. The advanced characterization techniques used to investigate the properties of electrolytes and interfaces are introduced, and the reaction processes and degradation mechanisms of SIBs are revealed. Furthermore, the practical prospects of SIBs promoted by high-quality electrolytes appropriately matched with electrodes are predicted and directions for developing next-generation SIBs are suggested.

Flexible P-Doped Carbon Cloth: Vacuum-Sealed Preparation and Enhanced Na-Storage Properties as Binder-Free Anode for Sodium Ion Batteries

In this work, a flexible and self-supporting P-doped carbon cloth (FPCC), which is composed of interwoven mesh of hollow microtubules with porous carbon walls, is prepared via a vacuum-sealed doping technology by employing the commercially available cotton cloth as sustainable and scalable raw material. When directly used as binder-free anode for sodium-ion batteries, the as-prepared FPCC delivers superior Na-storage properties in terms of specific capacity up to 242.4 mA h g^-1, high initial Coulombic efficiency of ∼72%, excellent rate capabilities (e.g., 123.1 mA h g^-1 at a high current of 1 A g^-1), and long-term cycle life (e.g., ∼88% capacity retention after even 600 cycles). All these electrochemical data are better than the undoped carbon cloth control, demonstrating the significance of P-doping to enhance the Na-storage properties of cotton-derived carbon anode. Furthermore, the technologies of electrochemical impedance spectroscopy and galvanostatic intermittent titration technique are implemented to disclose the decrease of charge transfer resistance and improvement of Na-migration kinetics, respectively.