Two-dimensional (2D) antimonene is a promising anode material in sodium-ion batteries (SIBs) because of its high theoretical capacity of 660 mAh g and enlarged surface active sites. However, its Na storage properties and sodiation/desodiation mechanism have not been fully explored. Herein, we propose the sodiation/desodiation reaction mechanism of 2D few-layer antimonene (FLA) based on results acquired by in situ synchrotron X-ray diffraction, ex situ selected-area electron diffraction, and theoretical simulations. Our study shows that the FLA undergoes anisotropic volume expansion along the a/b plane and exhibits reversible crystalline phase evolution (Sb ⇋ NaSb ⇋ NaSb) during cycling. Density-functional theory calculations demonstrate that the FLA has a small Na-ion diffusion barrier of 0.14 eV. The FLA delivers a larger capacity of 642 mAh g at 0.1 C (1 C = 660 mA g) and a high rate capability of 429 mAh g at 5 C and maintains a stable capacity of 620 mA g at 0.5 C with 99.7% capacity retention from the 10th to the 150th cycle. Considering the 660 mAh g theoretical capacity of Sb, the electrochemical utilization of Sb atoms of FLA is as high as 93.9% at a rate of 0.5 C for over 150 cycles, which is the highest capacity and Sb utilization ratio reported so far. Our study discloses the Na storage mechanism of 2D FLA, boosting promising applications of 2D materials for advanced SIBs.

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Binder plays a key role in maintaining the mechanical integrity of electrodes in lithium-ion batteries. However, the existing binders typically exhibit poor stretchability or low conductivity at large strains, which are not suitable for highcapacity silicon (Si)-based anodes undergoing severe volume changes during cycling. Herein, a novel stretchable conductive glue (CG) polymer that possesses inherent high conductivity, excellent stretchablity, and ductility is designed for high-performance Si anodes. The CG can be stretched up to 400% in volume without conductivity loss and mechanical fracture and thus can accommodate the large volume change of Si nanoparticles to maintain the electrode integrity and stabilize solid electrolyte interface growth during cycling while retaining the high conductivity, even with a high Si mass loading of 90%. The Si-CG anode has a large reversible capacity of 1500 mA h g −1 for over 700 cycles at 840 mA g −1 with a large initial Coulombic efficiency of 80% and high rate capability of 737 mA h g −1 at 8400 mA g −1 . Moreover, the Si-CG anode demonstrates the highest achieved areal capacity of 5.13 mA h cm −2 at a high mass loading of 2 mg cm −2 . The highly stretchable CG provides a new perspective for designing next-generation high-capacity and high-power batteries.

urgent strategies worldwide. [1] Rechargeable lithium-ion batteries have achieved great success during the last 40 years, while they gradually display certain limitations in further large-scale applications, such as high cost, uneven geological distribution and short supplies of lithium resources (0.0017 wt%) around the world. As alternative energy storage sources, sodium ion batteries (SIBs) and potassium ion batteries (PIBs) have recently attracted tremendous interest owing to their natural abundance, low cost and environmental friendliness. Despite having a similar abundance with sodium (sodium and potassium represent 2.36 and 2.09 wt% in the Earth's crust, respectively), potassium presents some specific advantages. K + /K exhibit a lower standard redox potential of −2.93 V (vs E°) compared with that of Na + /Na (−2.71 V vs E°), implying a higher working voltage and energy density of PIBs. [2] Moreover, potassium ions have much better conductivity and relatively lower desolvation energy in organic solvents. [3] These merits of potassium make it a promising low-cost candidate for high-energy and power density energy storage applications.The progress of PIBs mainly follows the development of electrode materials, especially considering the large-size of Metallic bismuth (Bi) has been widely explored as remarkable anode material in alkali-ion batteries due to its high gravimetric/volumetric capacity. However, the huge volume expansion up to ≈406% from Bi to full potassiation phase K 3 Bi, inducing the slow kinetics and poor cycling stability, hinders its implementation in potassium-ion batteries (PIBs). Here, facile strategy is developed to synthesize hierarchical bismuth nanodots/graphene (BiND/G) composites with ultrahigh-rate and durable potassium ion storage derived from an in situ spontaneous reduction of sodium bismuthate/graphene composites. The in situ formed ultrafine BiND (≈3 nm) confined in graphene layers can not only effectively accommodate the volume change during the alloying/dealloying process but can also provide high-speed channels for ionic transport to the highly active BiND. The BiND/G electrode provides a superior rate capability of 200 mA h g −1 at 10 A g −1 and an impressive reversible capacity of 213 mA h g −1 at 5 A g −1 after 500 cycles with almost no capacity decay. An operando synchrotron radiation-based X-ray diffraction reveals distinctively sharp multiphase transitions, suggesting its underlying operation mechanisms and superiority in potassium ion storage application.

This paper addresses an approach which integrates activity classification and dead reckoning techniques in step-based pedestrian navigation. In the proposed method, the pedestrian is equipped with a prototype wearable sensor module to record accelerations and determine the headings while walking. To improve the step detection accuracy, different types of activities are classified according to extracted features by means of a probabilistic neural network (PNN). The vertical acceleration data, which indicate the periodic vibration during gait cycle are filtered through a wavelet transform before being used to count the steps and assess the step length from which the distance traveled is estimated. By coupling the distance with the azimuth, navigation through pedestrian dead reckoning is implemented. This research provides a possible seamless pedestrian navigation solution which can be applied to a wide range of areas where the global navigation satellite system (GNSS) signal remains vulnerable. Results of two experiments in this paper reveal that the proposed approach is effective in reducing navigation errors and improving accuracy.

Downsizing alloy anode materials has been demonstrated as an efficient strategy to alleviate volume expansion and prolong the cycling performance for lithium (Li) ion storage.

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