Search

Summary: Betel nut wastes are firstly modified with nitric acid/thiourea to fabricate hetero‐element doping carbon (C‐H‐T) for energy storage. C‐H‐T exhibits improved content of O (12.27%), N (2.52%), and S (2.88%) compared with that of purely carbonized carbon with O (9.2%) and N (1.76%). Without nitric acid heat treatment, the carbon materials prepared by hydrothermal treatment with thiourea only get increasing hetero‐elements content of O (10.46%), N (2.9%), and S (0.53%). The similar results have been obtained using urea and melamine as dopants. Due to the synergistic effects of the hetero‐elements containing functional groups, C‐H‐T get a significant enhancement in its electrochemical properties with a high capacitance (423 F g−1 at 0.5 A g−1) in KOH electrolyte. C‐H‐T based coin‐type symmetric supercapacitors display maximum energy density of 61.7 Wh kg−1 and considerate cycling ability with 94% capacitance retention after 10 000 cycles. The fabricated two‐step method can inspire the increase of hetero‐elements content in carbon materials to develop its application in energy storage. [ABSTRACT FROM AUTHOR]

[Display omitted] • This work provides a novel and reliable insight for designing bimetallic sulfide with 2D nanostructure. • Laurel-leaf-like Co 9 S 8 /WS 2 @NC delivers a capacity of 359 mA h g−1 at 5.0 A g−1 • This as-prepared bimetallic sulfide exhibits a high capacitive contribution ratio of 90.8%. • The excellent performance originates from interface electric field and synergistic effects Co 9 S 8 and WS 2. Devising novel composite electrodes with particular structural/electrochemical characteristics becomes an efficient strategy to advance the performance of rechargeable battery. Herein, considering the homogeneous transition metal sulfide with N-doped carbon derived from zeolitic imidazolate framework-67 (ZIF-67) and WS 2 with large interlayer spacing, a laurel-leaf-like Co 9 S 8 /WS 2 @N-doped carbon bimetallic sulfide (Co 9 S 8 /WS 2 @NC) is engineered and prepared via a step-by-step method. As an electrode material for sodium ion batteries (SIBs), Co 9 S 8 /WS 2 @NC composite delivers high capacities of 480 and 405 mA h g−1 at 0.1 and 1.0 A g−1, respectively. As the current density increases from 0.1 to 5.0 A g−1, it provides specific capacity of 359 mA h g−1 with a capacity retention rate of 78.0%, which is higher than that of Co 9 S 8 @NC (63.5%) and WS 2 (58.6%). The Co 9 S 8 /WS 2 @NC composite anode maintains a stable specific capacity (354 mA h g−1 at 2.0 A g−1). It also exhibits a high capacitive contribution ratio of 90.8% at 1.0 mV s−1. This study provides a new and reliable insight for designing bimetallic sulfide with two-dimensional nanostructure for energy storage. [ABSTRACT FROM AUTHOR]

Sn-based materials have been popularly researched as anodes for energy storage due to their high theoretical capacity. However, the sluggish reaction kinetics and unsatisfied cycling stability caused by poor conductivity and dramatic volume expansion are still pivotal barriers for the development of Sn-based materials as anodes. In this work, the binary-metal Mn 2 SnO 4 nanoparticles and Sn encapsulated in N-doped carbon (Sn@Mn 2 SnO 4 -NC) were fabricated by multistep reactions and employed as the anode for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The coexistence of binary metals (Sn and Mn) can improve intrinsic conductivity. Simultaneously, hollow architecture along with carbon relieves internal stress and prevents structural collapse. A Sn@Mn 2 SnO 4 -NC anode delivers an appealing capacity of 1039.5 mAh g -1 for 100 cycles at 100 mA g -1 and 823.8 mAh g -1 for 600 cycles at 1000 mA g -1 in LIBs. When evaluated as an anode in SIBs, the Sn@Mn 2 SnO 4 -NC anode tolerates up to 7000 cycles at 2000 mA g -1 and maintains a capacity of 185.8 mAh g -1 . Quantified kinetic investigations demonstrate the high contribution of pseudocapacitive effects during the cycle process. Furthermore, density functional theory (DFT) calculations further verify that introduction of the second metal (Mn) improves the conductivity of the material, which is favorable for charge transport. This work is expected to provide a feasible preparation strategy for binary-metal materials to enhance the performance of lithium- and sodium-ion batteries.