Electrochemical synthesis and lithium storage properties of three-dimensional porous Sn–Co alloy/CNT composite

Three-dimensional (3-D) porous copper with stable pore structure is prepared by electroless plating. 3-D porous Sn–Co alloy/carbon nanotube (CNT) composite is synthesized by electrodeposition using 3-D porous copper as the substrate. The scanning electron microscope results indicate that 3-D porous Sn–Co alloy/CNT composite contains a large amount of interconnected pores with the diameter size of ~3 μm. Upon cycling, the pore structure gradually disappears, but no serious exfoliation appears due to porous structure and reinforcement by CNT. The charge/discharge results demonstrate that the 3-D porous Sn–Co alloy/CNT composite electrode delivers high first reversible specific capacity of 490 mAh g^?1, and remains 441 mAh g^?1 after 60 cycles tested at different current densities. Even at the current density of 3,200 mA g^?1, the reversible specific capacity remains 319 mAh g^?1, which is 65 % of the first specific capacity cycled at the current density of 100 mA g^?1.     

High Rate and Long Cycle Life of a CNT/rGO/Si Nanoparticle Composite Anode for Lithium‐Ion Batteries

Si nanoparticle (Si‐NP) composite anode with high rate and long cycle life is an attractive anode material for lithium‐ion battery (LIB) in hybrid electric vehicle (HEV)/pure electric vehicle (PEV). In this work, a carbon nanotube (CNT)/reduced graphene oxide (rGO)/Si nanoparticle composite with alternated structure as Li‐ion battery anode is prepared. In this structure, rGO completely wraps the entire Si/CNT networks by different layers and CNT networks provide fast electron transport pathways with reduced solid‐state diffusion, so that the stable solid‐electrolyte interphase layer can form on the whole surface of the matrix instead of on single Si nanoparticle, which ensure the high cycle stability to achieve the excellent cycle performance. As a result, the CNT/rGO/Si‐NP anode exhibits high performances with long cycle life (≈455 mAh g^?1 at 15 A g^?1 after 2000 cycles), high specific charge capacity (≈2250 mAh g^?1 at 0.2 A g^?1, ≈650 mAh g^?1 at 15 A g^?1), and fast charge/discharge rates (up to 16 A g^?1). This nanostructure anode with facile and low‐cost synthesis method, as well as excellent electrochemical performances, makes it attractive for the long life cycles at high rate of the next generation LIB applications in HEV/PEV.     

Advanced LiTi<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C anode by incorporation of carbon nanotubes for aqueous lithium-ion batteries

Inferior rate capability is a big challenge for LiTi₂(PO₄)₃ anode for aqueous lithium-ion batteries. Herein, to address such issue, we synthesized a high-performance LiTi₂(PO₄)₃/carbon/carbon nanotube (LTP/C/CNT) composite by virtue of high-quality carbon coating and incorporation of good conductive network. The as-prepared LTP/C/CNT composite exhibits excellent rate performance with discharge capacity of 80.1 and 59.1 mAh g^?1 at 10 C and 20 C (based on the mass of anode, 1 C = 150 mA g^?1), much larger than that of the LTP/C composite (53.4 mAh g^?1 at 10 C, and 31.7 mAh g^?1 at 20 C). LTP/C/CNT also demonstrates outstanding cycling stability with capacity retention of 83.3 % after 1000 cycles at 5 C, superior to LTP/C without incorporation of CNTs (60.1 %). As verified, the excellent electrochemical performance of the LTP/C/CNT composite is attributed to the enhanced electrical conductivity, rapid charge transfer, and Li-ion diffusion because of the incorporation of CNTs.     

Encapsulation of SnO2/Sn Nanoparticles into Mesoporous Carbon Nanowires and its Excellent Lithium Storage Properties

A peculiar nanostructure of encapsulation of SnO₂/Sn nanoparticles into mesoporous carbon nanowires (CNWs) has been successfully fabricated by a facile strategy and confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution TEM (HRTEM), X‐ray diffraction (XRD), BET, energy‐dispersive X‐ray (EDX) spectrometer, and X‐ray photoelectron spectroscopy (XPS) characterizations. The 1D mesoporous CNWs effectively accommodate the strain of volume change, prevent the aggregation and pulverization of nanostructured SnO₂/Sn, and facilitate electron and ion transport throughout the electrode. Moreover, the void space surrounding SnO₂/Sn nanoparticles also provides buffer spaces for the volumetric change of SnO₂/Sn during cycling, thus resulting in excellent cycling performance as potential anode materials for lithium‐ion batteries. Even after 499 cycles, a reversible capacity of 949.4 mAh g^?1 is retained at 800 mA g^?1. Its unique architecture should be responsible for the superior electrochemical performance.     

Vertically aligned α-MnO<Subscript>2</Subscript> nanosheets on carbon nanotubes as cathodic materials for aqueous rechargeable magnesium ion battery

In this work, vertically aligned α-MnO₂ nanosheets on carbon nanotubes are synthesized simply by a solution process and the electrochemical performance as host materials of magnesium ion is tested in aqueous solution. Cyclic voltammetry analysis confirms the enhanced electrochemical activity of carbon nanotube-supported samples. Moreover, carbon nanotubes skeleton could reduce the charge transfer resistant of the cathode materials, which is confirmed by electrochemical impedance spectroscopy. Furthermore, when tested as magnesium ion batteries cathodic electrode, the α-MnO₂/carbon nanotube sample registers a prominent discharge capacity of 144.6 mAh g^?1 at current density of 0.5 A g^?1, which is higher than the discharge capacity of α-MnO₂ (87.5 mAh g^?1) due to the synergistic effect of insertion/deinsertion reaction and physical adsorption/desorption process. After the 1000th cycle, a remarkable discharge capacity of 48.3 mAh g^?1 is collected for α-MnO₂/carbon nanotube at current density of 10 A g^?1, which is 85% of the original. It is found that the carbon skeleton not only improved the capacity but also enhanced the cycling performance of the α-MnO₂ electrode significantly. Therefore, α-MnO₂/carbon nanotube is a very promising candidate for further application in environmentally benign magnesium ion batteries.     

One-pot synthesis and electrochemical property of MnO/C hybrid microspheres

In this paper, we reported a one-pot method to synthesize MnO/C hybrid microspheres via solvothermal approach for the first time. Only peaks of MnO could be observed from X-ray diffractometry patterns, indicating that the carbon in the composite was amorphous. Scanning electron microscope and transmission electron microscopy images showed that the surfaces of these as-prepared spheres were relatively smooth and of about 2.2 μm in diameter. Electrochemical property demonstrated that the annealed MnO/C hybrid microspheres possessed higher reversible capacity and cycling stability than that of MnO nanoparticles. The annealed MnO/C hybrid microspheres exhibited a large initial charge capacity of 856 mAh?g^?1, and the stabilized capacity was as high as 601 mAh?g^?1 after 30 cycles. These improvements can be ascribed to the amorphous carbon, which can enhance the conductivity of MnO, suppress the aggregation of active particles, and increase their structural stability during cycling.     

A novel composite anode for LIB prepared via template-like-directed electrodepositing Cu–Sn alloy process

A novel composite anode material consisted of electrodeposited Cu–Sn alloy dispersing in a conductive micro-porous carbon membrane coated on Cu current collector was investigated. The composite material was prepared by template-like-directed electrodepositing Cu–Sn alloy process and then annealing. The template-like microporous membrane electrode was obtained as follows: (1) casting a polyacrylonitrile (PAN) solution on a copper foil, (2) then immersing the copper foil into deionized water for phase inversion, and (3) drying the membrane electrode. This method provided the composite material with high decentralization of Cu–Sn alloy and supporting medium function of conductive carbon membrane deriving from pyrolysis of PAN. SEM, XRD, and EDS analysis confirmed this structure. The characteristic structure was beneficial to inhibit the aggregation among Cu–Sn microparticles, to relax the volume expansion during cycling, and to improve the cycle ability of electrode. The reversible charge/discharge capacity of the composite material remained more than 426.6 and 445.1 mAh g⁻¹, respectively, after 70 cycles, while that of the electrode prepared by electrodepositing Cu–Sn on a bare Cu foil decreased seriously to only 11.3 mAh g⁻¹. These results show that the novel preparing anode process for LIB is a promising method and can achieve composite materials with larger specific capacity and long cycle life.     

Facile synthesis of N-doped carbon-coated Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode for application in high-rate lithium ion batteries

A facile sol-gel approach for the synthesis of lithium titanate composite decorated with N-doped carbon material (LTO/NC) is proposed. Urea is used as a nitrogen source in the proposed approach. The LTO/NC exhibits superior electrochemical performances as an electrode material for lithium-ion batteries, delivering a discharge capacity of as high as 103 mAh g^?1 at a high rate of 20 C and retaining a stable reversible capacity of 90 mAh g^?1 after 1000 cycles, corresponding to 100% capacity retention. These excellent electrochemical performances are proved by the nanoscale structure and N-doped carbon coating. NC layers were uniformly dispersed on the surface of LTO, thus preventing agglomeration, favoring the rapid migration of the inserted Li ion, and increasing the Li⁺ diffusion coefficient and electronic conductivity. LTO with the appropriate amount of NC coating is a promising anode material with applications in the development of high-powered and durable lithium-ion batteries.     

An electrochemical and structural investigation of porous composite anode materials for LIB

A porous composite anode for lithium ion battery (LIB) was investigated. The composite anode was prepared by electrodepositing Sn?CSb alloy on a template-like electrode and then annealing it in the atmosphere of N₂, whereas the porous template-like electrode was obtained by forming a sponge-like porous membrane on a copper foil via a mixed phase inversion process, followed by pre-plating Cu through membrane pores in it. SEM and XRD results showed that composite structure of the anode consisted of electrodeposited Sn?CSb alloy dispersed in a PAN-pyrolyzed conjugated conducting polymer gridding, which was tightly connected with the Cu foil through transition alloy layer formed by heat treatment. Due to its relatively reasonable microcosmic structure, the composite anode presented better cycling performance and specific capacity retention during charging and discharging at diverse rates. When cycled between 0 and 2.0?V (vs Li/Li⁺) at 0.5?C rate, the reversible charge/discharge capacity of the composite material remained 415 and 414.8?mAh?g^?1, respectively, after 30 cycles, corresponding to 82.9% of the capacity retention. When charging and discharging at 2?C rate, the composite material electrode showed 71.7% capacity retention at the 30th cycle.     

Effect of pyrolytic polyacrylonitrile on electrochemical performance of Si/graphite composite anode for lithium-ion batteries

The silicon/graphite (Si/G) composite was prepared using pyrolytic polyacrylonitrile (PAN) as carbon precursor, which is a nitrogen-doped carbon that provides efficient pathway for electron transfer. The combination of flake graphite and pyrolytic carbon layer accommodates the large volume expansion of Si during discharge-charge process. The Si/G composite was synthesized via cost-effective liquid solidification followed by carbonization process. The effect of PAN content on electrochemical performance of composites was investigated. The composite containing 40 wt% PAN exhibits a relatively better rate capability and cycle performance than others. It exhibits initial reversible specific capacity of 793.6 mAh g^?1 at a current density of 100 mA g^?1. High capacity of 661 mAh g^?1 can be reached after 50 cycles at current density of 500 mA g^?1.