Silicon is one of the most promising anode materials for lithium‐ion batteries because of the highest known theoretical capacity and abundance in the earth' crust. Unfortunately, significant “breathing effect” during insertion/deinsertion of lithium in the continuous charge‐discharge processes causes the seriously structural degradation, thus losing specific capacity and increasing battery impedance. To overcome the resultant rapid capacity decay, significant achievements has been made in developing various nanostructures and surface coating approaches in terms of the improvement of structural stability and realizing the long cycle times. Here, the recent progress in surface and interface engineering of silicon‐based anode materials such as core‐shell, yolk‐shell, sandwiched structures and their applications in lithium‐ion batteries are reviewed. Some feasible strategies for the structural design and boosting the electrochemical performance are highlighted. Future research directions in the field of silicon‐based anode materials for next‐generation lithium‐ion batteries are summarized.

Herein, we report a "shape fixing via salt recrystallization" method to efficiently synthesize nitrogen-doped carbon material with a large number of active sites exposed to the three-phase zones, for use as an ORR catalyst. Self-assembled polyaniline with a 3D network structure was fixed and fully sealed inside NaCl via recrystallization of NaCl solution. During pyrolysis, the NaCl crystal functions as a fully sealed nanoreactor, which facilitates nitrogen incorporation and graphitization. The gasification in such a closed nanoreactor creates a large number of pores in the resultant samples. The 3D network structure, which is conducive to mass transport and high utilization of active sites, was found to have been accurately transferred to the final N-doped carbon materials, after dissolution of the NaCl. Use of the invented cathode catalyst in a proton exchange membrane fuel cell produces a peak power of 600 mW cm(-2), making this among the best nonprecious metal catalysts for the ORR reported so far. Furthermore, N-doped carbon materials with a nanotube or nanoshell morphology can be realized by the invented method.

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In order to achieve consistent electrochemical properties essential for the commercialization of the high-voltage spinel cathode LiMn 1.5 Ni 0.5 O 4 , a deeper fundamental understanding of the factors contributing to capacity fade is required. Specifically, the relationship between cation ordering, impurity phases present, and particle morphology must be elucidated. We present here a comparison of stoichiometric LiMn 1.5 Ni 0.5 O 4 cathodes with a 3:1 Mn/Ni ratio prepared by different methods with varying morphologies and degrees of cation ordering. Careful structural, chemical, and electrochemical characterizations illuminate the relative influence of the various factors on the electrochemical cycling stability and high-rate performance. It is found that although an increase in the degree of cation ordering decreases the rate capability, the crystallographic planes in contact with the electrolyte have a dominant effect on the electrochemical properties.

Zn–organic batteries are attracting extensive attention, but their energy density is limited by the low capacity (<400 mAh g–1) and potential (<1 V vs Zn/Zn2+) of organic cathodes. Herein, we propose a long-life and high-rate Zn–organic battery that includes a poly­(1,5-naphthalenediamine) cathode and a Zn anode in an alkaline electrolyte, where the cathode reaction is based on the coordination reaction between K+ and the CN group (i.e., CN/C–N–K conversion). Interestingly, we find that the discharged Zn–organic battery can recover to its initial state quickly with the presence of O2, and the theoretical calculation demonstrates that the K–N bond in the discharged cathode can be easily broken by O2 via redox reaction. Accordingly, we design a chemically self-charging aqueous Zn–organic battery. Benefiting from the excellent self-rechargeability, the organic cathode exhibits an accumulated capacity of 16264 mAh g–1, which enables the Zn–organic battery to show a record high energy density of 625.5 Wh kg–1.

A commercial LiNiCoMnO (LNCM) cathode material is purposefully modified using a small account of LiPF as one precursor via a simple means at low calcination temperature in air. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy images reveal that this modification process keeps the layered bulk structure of LNCM even though the surface components have obviously been modified. Electron energy loss spectroscopy and X-ray photoelectron spectroscopy with different etching depths further prove the formation of LiF and F doping on the LNCM surface, which simultaneously triggers partial Ni reduction to Ni; and the metal-oxygen bond is partially replaced by a higher energy metal-fluorine bond. The modified material (LNCM-2) retains 93.7% of its initial capacity and delivers 179.4 mAh g at a current density of 0.5 C after 100 stable cycles at 3.0-4.5 V. Meanwhile, LNCM-2 is able to maintain capacity retention up to 81.1% after 300 cycles at 5 C, much better than the original LNCM (35.1%) in the commercial electrolyte. Remarkably, 90% of initial capacity is retained for LNCM-2 with considerably improved Coulombic efficiency (>99.5%) at 5 C after 300 cycles within a voltage range of 3-4.5 V compared with the primary LNCM using succinonitrile-based electrolyte. Consequently, these results fully demonstrate the advantages of synergistic effect between F doping and LiF coating.

HIGHLIGHTS• A layered sodium-ion/crystal water co-intercalated Na 0.55 Mn 2 O 4 ·0.57H 2 O (NMOH) cathode is synthesized successfully with a selectively etching method for zinc-ion batteries.• A displacement/intercalation mechanism is confirmed in the Mn-based cathode for the first time.• The NMOH cathode delivers a competitive reversible capacity of 201.6 mA h g −1 at 500 mA g −1 after 400 cycles.ABSTRACT Mn-based rechargeable aqueous zinc-ion batteries (ZIBs) are highly promising because of their high operating voltages, attractive energy densities, and eco-friendliness. However, the electrochemical performances of Mn-based cathodes usually suffer from their serious structure transformation upon charge/discharge cycling.Herein, we report a layered sodium-ion/crystal water co-intercalated Birnessite cathode with the formula of Na 0.55 Mn 2 O 4 ·0.57H 2 O (NMOH) for high-performance aqueous ZIBs. A displacement/intercalation electrochemical mechanism was confirmed in the Mn-based cathode for the first time. Na + and crystal water enlarge the interlayer distance to enhance the insertion of Zn 2+ , and some sodium ions are replaced with Zn 2+ in the first cycle to further stabilize the layered structure for subsequent reversible Zn 2+ /H + insertion/extraction, resulting in exceptional specific capacities and satisfactory structural stabilities. Additionally, a pseudo-capacitance derived from the surface-adsorbed Na + also contributes to the electrochemical performances. The NMOH cathode not only delivers high reversible capacities of 389.8 and 87.1 mA h g −1 at current densities of 200 and 1500 mA g −1 , respectively, but also maintains a good long-cycling performance of 201.6 mA h g −1 at a high current density of 500 mA g −1 after 400 cycles, which makes the NMOH cathode competitive for practical applications.Zinc sulfate (ZnSO 4 ·H 2 O, 99.9%), sodium sulfate (Na 2 SO 4 , 99.9%), and manganese sulfate (MnSO 4 ·H 2 O, 99.9%) were purchased from Aladdin (China). Sodium silicate Nano-Micro Lett.

In this work, a novel carbon-free core-shell α-iron oxide (α-Fe2O3)@ spinel lithium titanate (Li4Ti5O12, LTO) composite has been synthesized via a facile hydrothermal process. Element mapping confirmed the core-shell structure of α-Fe2O3@LTO. The effects of various experimental parameters, including thickness of TiO2 coating, reaction temperature, and time on the morphologies of the resulted products, were systematically investigated. The electrochemical measurements demonstrate that uniform α-Fe2O3 ellipsoids are coated with LTO to avoid forming a solid electrolyte interface (SEI) layer, to reduce initial capacity loss, and to improve the reversibility of α-Fe2O3 for Li ion storage. Compared with naked α-Fe2O3 ellipsoids, the α-Fe2O3@LTO composites exhibit lower initial capacity loss, higher reversible capacity, and better cycling performance for lithium storage. The electrochemical performance of α-Fe2O3@LTO composite heavily depends on the thickness and density of LTO coating shells. The carbon-free coating of LTO is highly effective in improving the electrochemical performance of α-Fe2O3, promising advanced batteries with high surface stability and excellent security.