Cu2S@ N, S dual-doped carbon matrix hybrid as superior anode materials for lithium/sodium ion batteries

CuS is considered as a promising electrode material for lithium-ion and sodium-ion batteries owing to its flat charge-discharge plateau as well as the abundant reserves. However, serious capacity fading and formation of polysulfides during electrochemical process restrict its practical application. In this work, a new type of CuS@N, S dual-doped carbon matrix (CuS@NSCm) hybrid is synthesized through a simple in-situ polymerization process and subsequent carbonization process. Due to the N, S dual-doped carbon matrix, which can buffer the volume change, restrain the dissolution of polysulfide and enhance the electron conductivity during electrochemical process, the hybrid demonstrates excellent electrochemical performance. The CuS@NSCm hybrid exhibits a reversible capacity of 560.1 mAh g at a current density of 1000 mA g after 550 cycles when used in lithium-ion batteries, which is among the best performance for CuS based anode materials. Moreover, a capacity of 182.3 mAh g is obtained after 50 cycles when used as an anode material in sodium ion batteries, which is much better than the pure CuS

CoO@N-Doped Carbon Composite Nanotubes as Excellent Anodes for Lithium-Ion Batteries

In this work, we report the successful fabrication a new type of CoO@N-doped carbon matrix composite nanotubes (CoO@NC Ntm) using Co(CO)(OH)⋅0.11HO needlelike nanorods as the self-sacrifice templates and polypyrrole as carbon and nitrogen sources. The preparation process is facile and efficient. CoO nanoparticles are homogeneously embedded in the N-doped carbon nanotube matrix. Combining the benefits of the N-doped carbon matrix and the special architecture, CoO@NC Ntm delivers a superior long-term cycling stability and high-rate performance as the anode material for lithium-ion batteries. Even when tested at a higher current density of 2000 mA g, a reversible capacity of 523.4 mAh g can be retained after 1000 cycles, with capacity retention of almost 100 % from 2 to 1000 cycles. This work may shed light on the fabrication of other oxide materials @N-doped carbon matrix composites for energy-storage applications

Enlarging Surface/Bulk Ratios of NiO Nanoparticles toward High Utilization and Rate Capability for Supercapacitors

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Reasonable design and delicate control of microstructures are critical to achieve high energy density of active materials for pseudocapacitors that seriously depend on usable reaction interface. This work shows the effect of ultrasmall particle size on enhancing utilization and rate performance of active materials. Three types of NiO nanocrystals with different sizes of 3.36, 6.24, and 7.18 nm in average diameter are uniformly distributed on mesoporous carbon nanosheets derived from corn straw piths. The nanosheets with 3.36 nm NiO particles present an extremely high NiO utilization of 93.4% (2404 F g−1 at 0.5 A g−1), which is 2–2.5-fold higher than materials with large sizes (6.24 and 7.18 nm). This enhancement is ascribed to more complete conversion and higher ionic/electronic conductivity from a preferable surface/bulk ratio of NiO. By coupling with commercial activated carbon, the asymmetric supercapacitors present high energy and power densities (28.53 Wh kg−1 at 375 W kg−1), with 78.3% capacitance retention after 10 000 cycles at 10 A g−1

Size-dependent capacitive behavior of homogeneous MnO nanoparticles on carbon cloth as electrodes for symmetric solid-state supercapacitors with high performance

As promising electrode materials for supercapacitors, manganese oxides still have big challenges such as the low material utilization and poor ionic/electronic conductivity. Reducing particle sizes through nanotechnology has been used to improve material conductivity and electrochemical active sites at materials/electrolyte interfaces. Nevertheless, the extremely small particle size may result in physical and/or chemical instability, mass loss and subsequent capacitance attenuation. Understanding this trade-off effect of electrode materials size with their electrochemical properties is critical to fabricate high-performance supercapacitors. In this work, we prepare homogenous and size-tunable MnO particles (with mean diameters of 80, 41, 20, 15 and 9 nm) on carbon cloth via a facile gel-like film assisted method. It is found that the medium-size nanoparticle (20 nm) displays the best performance instead of the smallest one. These observations are different from the traditional view about material size-property relationship. Instead this work provides a new insight referring to both the size-dependent solubility and ionic/electronic transport. Beneficial from the good flexibility and high conductivity/stability of carbon cloth, the optimized MnO/carbon cloth electrode demonstrates extraordinary performance in symmetric solid-state supercapacitors with energy densities of 86 and 70 Wh kg−1 at the power densities of 450 W kg−1 and 9 kW kg−1, respectively

Enlarging Surface/Bulk Ratios of NiO Nanoparticles toward High Utilization and Rate Capability for Supercapacitors

Reasonable design and delicate control of microstructures are critical to achieve high energy density of active materials for pseudocapacitors that seriously depend on usable reaction interface. This work shows the effect of ultrasmall particle size on enhancing utilization and rate performance of active materials. Three types of NiO nanocrystals with different sizes of 3.36, 6.24, and 7.18 nm in average diameter are uniformly distributed on mesoporous carbon nanosheets derived from corn straw piths. The nanosheets with 3.36 nm NiO particles present an extremely high NiO utilization of 93.4% (2404 F g−1 at 0.5 A g−1), which is 2–2.5-fold higher than materials with large sizes (6.24 and 7.18 nm). This enhancement is ascribed to more complete conversion and higher ionic/electronic conductivity from a preferable surface/bulk ratio of NiO. By coupling with commercial activated carbon, the asymmetric supercapacitors present high energy and power densities (28.53 Wh kg−1 at 375 W kg−1), with 78.3% capacitance retention after 10 000 cycles at 10 A g−1.</p