Uniform yolk–shell Sn4P3@C nanospheres exhibit very high reversible capacity, superior rate capability and stable cycling performance for Na-ion batteries.

Sodium ion batteries attract increasing attention for large-scale energy storage as a promising alternative to the lithium counterparts in view of low cost and abundant sodium source. However, the large ion radius of Na brings about a series of challenging thermodynamic and kinetic difficulties to the electrodes for sodium-storage, including low reversible capacity and low ion transport, as well as large volume change. To mitigate or even overcome the kinetic problems, we develop a self-assembly route to a novel architecture consisting of nanosized porous NASICON-type NaTi2(PO4)3 particles embedded in microsized 3D graphene network. Such architecture synergistically combines the advantages of a 3D graphene network and of 0D porous nanoparticles. It greatly increases the electron/ion transport kinetics and assures the electrode structure integrity, leading to attractive electrochemical performance as reflected by a high rate-capability (112 mAh g(-1) at 1C, 105 mAh g(-1) at 5C, 96 mAh g(-1) at 10C, 67 mAh g(-1) at 50C), a long cycle-life (capacity retention of 80% after 1000 cycles at 10C), and a high initial Coulombic efficiency (>79%). This nanostructure design provides a promising pathway for developing high performance NASICON-type materials for sodium storage.

Lithium ion capacitors are new energy storage devices combining the complementary features of both electric double-layer capacitors and lithium ion batteries. A key limitation to this technology is the kinetic imbalance between the Faradaic insertion electrode and capacitive electrode. Here, we demonstrate that the Li VO with low Li-ion insertion voltage and fast kinetics can be favorably used for lithium ion capacitors. N-doped carbon-encapsulated Li VO nanowires are synthesized through a morphology-inheritance route, displaying a low insertion voltage between 0.2 and 1.0 V, a high reversible capacity of ≈400 mAh g at 0.1 A g , excellent rate capability, and long-term cycling stability. Benefiting from the small nanoparticles, low energy diffusion barrier and highly localized charge-transfer, the Li VO /N-doped carbon nanowires exhibit a high-rate pseudocapacitive behavior. A lithium ion capacitor device based on these Li VO /N-doped carbon nanowires delivers a high energy density of 136.4 Wh kg at a power density of 532 W kg , revealing the potential for application in high-performance and long life energy storage devices.

Figure 3h in the originally published article is hereby corrected. In the originally published article, the representation is incomplete. The experimental data essentially show two maxima, which refer to NiP bonds and impurity effects, respectively. For simplicity only the major contributors to these maxima were indicated. On the other hand-and this is the misleading point-the fitted spectrum that was presented takes account of the fine-structure (in particular of the clearly visible shoulder in between the peaks) and is the complete superposition of the two spin-orbit split components of various chemical species (stemming from NiP bonds and from impurity effects caused by contamination with oxygen and/or carbon), and naturally not only of the two major components shown. The exact deconvolution is given in the new figure here. As contributions by impurities were clearly addressed in the original text, the interpretation and conclusions are not at all affected by this point. Nonetheless the authors would like to apologize for any possible confusion as a result. The authors would like to take this opportunity to also acknowledge the Scientific Facility Interface Analysis headed by Ulrich Starke. The authors thank in particular Kathrin Müller for performing the X-ray photoelectron spectroscopy (XPS) measurements using a Kratos Axis Ultra system equipped with a monochromatized Al K α X-ray source (photon energy 1486.7 eV) and for the exact data evaluation and fitting. Corrected Figure 3h. High-resolution XPS spectrum (P 2p) for Ni 2 P⊂pGN together with the exact fit and deconvolution into one NiP bond contribution (red) and two contributions stemming from contamination with oxygen and/or carbon (blue). For each species the two spin-orbit split components are plotted.