Sodium ion batteries are attractive for the rapidly emerging large‐scale energy storage market for intermittent renewable resources. Currently a viable cathode material does not exist for practical non‐aqueous sodium ion battery applications. Here we disclose a high performance, durable electrode material based on the 3D NASICON framework. Porous Na3V2(PO4)3/C was synthesized using a novel solution‐based approach. This material, as a cathode, is capable of delivering an energy storage capacity of ∼400 mWh/g vs. sodium metal. Furthermore, at high current rates (10, 20 and 40 C), it displayed remarkable capacity retention. Equally impressive is the long term cycle life. Nearly 50% of the initial capacity was retained after 30,000 charge/discharge cycles at 40 C (4.7 A/g). Notably, coulombic efficiency was 99.68% (average) over the course of cycling. To the best of our knowledge, the combination of high energy density, high power density and ultra long cycle life demonstrated here has never been reported before for sodium ion batteries. We believe our findings will have profound implications for developing large‐scale energy storage systems for renewable energy sources.

In this paper, we report that Li can be stored in RuO2 with an unusually high coulombic efficiency. The process involves three electrochemical steps: i) formation of a Ru/Li2O nanocomposite, ii) formation of a Li‐containing surface film, and iii) interfacial deposition of Li within the Ru/Li2O matrix. Corresponding to the storage of 5.6 mole of Li ions per mole of RuO2, a high capacity of 1130 mAh g–1 is achieved. Furthermore, virtually all inserted Li ions can be extracted, corresponding to a nearly 100 % coulombic efficiency at the first cycle. Achieving a complete reversibility for such a Li storage system through complex heterogeneous solid‐state electrochemical reactions is possible because of the formation of nanoscale Ru/Li2O during Li insertion and nano‐RuO2 during Li extraction, in addition to the favorable transport properties of RuO2 itself.

and TiN with lithium in nonaqueous lithium cells over a wide voltage range ͑0.02-4.3 V͒ at room temperature. In most cases, deep Li uptake occurs via heterogeneous reaction resulting in transformation of MX m (M ϭ transition metal; X ϭ F or O or S or N͒ into a nanocrystalline or amorphous LiX m/n /M composite from which Li can be extracted under restoration of the MX m phase. Thermodynamic and kinetic aspects, especially overpotential and its possible origins for both Li uptake and Li extraction processes, are discussed.

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We report here the electrochemical properties of Na 2 Ti 3 O 7 , a potential non-carbon based, low-voltage anode material for room temperature sodium ion battery applications. A solid-state route was used to prepare Na 2 Ti 3 O 7 . Further, XRD, SEM, TEM, HRTEM, SAED, XPS and EDX techniques were used to characterize the material. The Na/Na 2 Ti 3 O 7 cell displayed a charge capacity of 177 mA h g À1 at 0.1 C rate. High rate and long term cyclic performance at different rates showed relatively stable storage capacities. Surprisingly, if the lower cut-off voltage is altered, the appearance of a new charge plateau is seen, with no apparent change in the discharge behaviour. The kinetics of sodium insertion and extraction are discussed utilizing CV and EIS techniques. We also report the sodium chemical diffusion coefficient of the Na 2 Ti 3 O 7 /CB electrode estimated using GITT.

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