No abstract

Hybridizing Ni2P/graphene sheet composite is successfully accomplished via a one-pot solvothermal method. As anode materials for lithium-ion batteries, the Ni2P spheres with sizes of 10–30 nm can effectively prevent the agglomeration of graphene sheets. In turn, the graphene sheets with good electrical conductivity serve as a conducting network for fast electron transfer between the active materials and charge collector, as well as buffered spaces to accommodate the volume expansion/contraction during cycling. The cyclic stability and rate capability of Ni2P are significantly improved after the incorporation of graphene sheets. After 50 cycles, the Ni2P/graphene sheet hybrid delivers a capacity of 450 mA h g–1 and 360 mA h g–1 at a current density of 54.2 and 542 mA g–1, respectively. The voltage hysteresis of Ni2P with and without graphene sheets is also discussed. The incorporation of graphene sheets can partly decrease the voltage polarization, and modify the thickness of solid electrolyte interface (SEI) film.

Flexible multidirectional strain sensors are crucial to accurately determining the complex strain states involved in emerging sensing applications. Although considerable efforts have been made to construct anisotropic structures for improved selective sensing capabilities, existing anisotropic sensors suffer from a trade-off between high sensitivity and high stretchability with acceptable linearity. Here, an ultrasensitive, highly selective multidirectional sensor is developed by rational design of functionally different anisotropic layers. The bilayer sensor consists of an aligned carbon nanotube (CNT) array assembled on top of a periodically wrinkled and cracked CNT–graphene oxide film. The transversely aligned CNT layer bridge the underlying longitudinal microcracks to effectively discourage their propagation even when highly stretched, leading to superior sensitivity with a gauge factor of 287.6 across a broad linear working range of up to 100% strain. The wrinkles generated through a pre-straining/releasing routine in the direction transverse to CNT alignment is responsible for exceptional selectivity of 6.3, to the benefit of accurate detection of loading directions by the multidirectional sensor. This work proposes a unique approach to leveraging the inherent merits of two cross-influential anisotropic structures to resolve the trade-off among sensitivity, selectivity, and stretchability, demonstrating promising applications in full-range, multi-axis human motion detection for wearable electronics and smart robotics.

MXenes are promising cathode materials for aqueous zinc-ion batteries (AZIBs) owing to their layered structure, metallic conductivity, and hydrophilicity. However, they suffer from low capacities unless they are subjected to electrochemically induced second phase formation, which is tedious, time-consuming, and uncontrollable. Here we propose a facile one-step surface selenization strategy for realizing advanced MXene-based nanohybrids. Through the selenization process, the surface metal atoms of MXenes are converted to transition metal selenides (TMSes) exhibiting high capacity and excellent structural stability, whereas the inner layers of MXenes are purposely retained. This strategy is applicable to various MXenes, as demonstrated by the successful construction of VSe2@V2CT x , TiSe2@Ti3C2T x , and NbSe2@Nb2CT x . Typically, VSe2@V2CT x delivers high-rate capability (132.7 mA h g–1 at 2.0 A g–1), long-term cyclability (93.1% capacity retention after 600 cycles at 2.0 A g–1), and high capacitive contribution (85.7% at 2.0 mV s–1). Detailed experimental and simulation results reveal that the superior Zn-ion storage is attributed to the engaging integration of V2CT x and VSe2, which not only significantly improves the Zn-ion diffusion coefficient from 4.3 × 10–15 to 3.7 × 10–13 cm2 s–1 but also provides sufficient structural stability for long-term cycling. This study offers a facile approach for the development of high-performance MXene-based materials for advanced aqueous metal-ion batteries.