Construction of strong built-in electric field in binary metal sulfide heterojunction to propel high-loading lithium-sulfur batteries

The practical application of lithium-sulfur(Li-S)batteries is greatly hindered by soluble polysulfides shuttling and sluggish sulfur redox kinetics.Rational design of multifunctional hybrid materials with superior electronic conductivity and high electrocatalytic activity,e.g.,heterostructures,is a promising strategy to solve the above obstacles.Herein,a binary metal sulfide MnS-MoS_(2) heterojunction electrocatalyst is first designed for the construction of high-sulfur-loaded and durable Li-S batteries.The MnS-MoS_(2) p-n heterojunction shows a unique structure of MoS_(2) nanosheets decorated with ample MnS nanodots,which contributes to the formation of a strong built-in electric field at the two-phase interface.The MnS-MoS_(2) hybrid host shows strong soluble polysulfide affinity,enhanced electronic conductivity,and exceptional catalytic effect on sulfur reduction.Benefiting from the synergistic effect,the as-derived S/MnS-MoS_(2) cathode delivers a superb rate capability(643 m A h g^(-1)at 6 C)and a durable cyclability(0.048%decay per cycle over 1000 cycles).More impressively,an areal capacity of 9.9 m A h cm^(-2)can be achieved even under an extremely high sulfur loading of 14.7 mg cm^(-2)and a low electrolyte to sulfur ratio of 2.9μL mg^(-1).This work provides an in-depth understanding of the interfacial catalytic effect of binary metal compound heterojunctions on sulfur reaction kinetics.

Facile fabrication of interconnected-mesoporous T-Nb_2O_5 nanofibers as anodes for lithium-ion batteries

Niobium pentoxide(Nb2O5) has been extensively studied as anode materials for lithium ion batteries(LIBs) due to its good rate performance and safety advantages.However, the intrinsic low electronic conductivity has largely restricted its practical application. In this work, we report the construction of mesoporous T-Nb2O5 nanofibers by electrospinning followed by heat treatment in air. The interconnected mesoporous structure ensures a high surface area with easy electrolyte penetration. When used as anodes for LIBs, the mesoporous Nb2O5 electrode delivers a high reversible specific capacity of 238 mA h g-1 after 1,000 cycles at a current density of 1 A g-1 within a voltage range of 0.01–3.0 V.Even at a higher discharge cut-off voltage window of 1.0–3.0 V, it still possesses a high reversible capacity of166 mA h g-1 after 200 cycles. Moreover, the porous Nb2O5 electrode also exhibits excellent rate capability. The enhanced electrochemical performances are attributed to the synergistic effects of porous nanofiber structure and unique crystal structure of T-Nb2O5, which has endowed this material a large electrode-electrolyte contact area with improved electronic conductivity.

Rational synthesis of SnS_2@C hollow microspheres with superior stability for lithium-ion batteries

Tin-based nanomaterials have been extensively explored as high-capacity anode materials for lithium ion batteries（LIBs）. However,the large volume changes upon repeated cycling always cause the pulverization of the electrode materials. Herein,we report the fabrication of uniform SnS_2@C hollow microspheres from hydrothermally prepared SnO_2@C hollow microspheres by a solid-state sulfurization process. The as-prepared hollow SnS_2@C microspheres with unique carbon shell,as electrodes in LIBs,exhibit high reversible capacity of 814 mA h g^（-1） at a current density of 100 mA g^（-1）,good cycling performance（783 mA h g^（-1） for 200 cycles maintained with an average degradation rate of 0.02% per cycle） and remarkable rate capability（reversible capabilities of 433 mA h g^（-1）at 2C）. The hollow space could serve as extra space for volume expansion during the charge-discharge cycling,while the carbon shell can ensure the structural integrity of the microspheres. The preeminent electrochemical performances of the SnS_2@C electrodes demonstrate their promising application as anode materials in the next-generation LIBs.