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In this paper, the effects of ordinary multiwalled carbon nanotubes (MWCNTs) interlayer and novel fluorinated carbon nanotube (F-MWCNTs) interlayer on the electrochemical performance of lithium–sulfur (Li–S) batteries were investigated. After fluorination of graphitized MWCNTs, F-WMCNTs with a core–shell structure (fluorocarbon atomic ratio C/F = 1:1) can be obtained. The surface of F-WMCNTs was fluorinated to form a fluorinated carbon structure, while the internal structure of the original MWCNTs remains. F-MWCNTs/MWCNTs and cellulose fibers form a 3D crosslinked network structure, which effectively captures polysulfides. This layer was confirmed by scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). The F-MWCNTs interlayer Li–S battery maintained specific capacities of 1026 mAh/g, 938 mAh/g, and 764 mAh/g at 1C, 2C, and 3C, respectively, showing excellent rate performance. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) were doped by ammonium borate as the sources of nitrogen and boron. Under the protection of Ar gas, boron-nitrogen doped CNTs were prepared through nitriding and boronization at high temperature. It is a conductive additive. Then, the obtained CNTs were mixed with activated carbon (AC), SP, sodium dodecyl sulfate (SDS), and cellulose fiber to prepare electrodes. With all the materials, a symmetric electric double-layer supercapacitor (EDLC) was assembled. Next, the materials and electrodes were also characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The factors, chemical connections, and specific surface area of the CNTs were analyzed by X-ray energy spectrum analysis (EDS), X-ray photoelectron spectroscopy (XPS), as well as a specific surface area and porosimetry analyzer (BET). In addition, the electrochemical performances of electric double-layer capacitors were tested with the help of cyclic voltammetry, constant-current charging and discharging, and so on. From the results, we can make a conclusion, that is, both B and N atoms were added into the CNTs and formed bonds successfully with carbon atoms mutually. Besides, the specific surface area is about 1.5 times than that of the CNT. When the charge/discharge current density reaches 50 mA/g, we can find that the mass specific capacitance of the capacitor can run up to 32.19 F/g. Also, we observe that the maximum power density is close to 220 W/kg (700 mA/g), and the energy density can arrive 9.31 Wh/kg (50 mA/g). Based on the impedance test, the electrodes are characterized with low impedance. After 2000 cycles, the boron-nitrogen doped double-layer capacitors maintain a capacitance retention ratio of above 95%. Its power density can still achieve 220 W/kg when the energy density keeps at 3.46 Wh/kg. In other words, the electrochemical performance functions of the electric double-layer capacitors are enhanced while the CNTs serve as the electrodes. Boron–nitrogen double-doped multi-walled carbon nanotubes (BNC) were obtained by high-temperature nitridation and boronation. BNC and activated carbon (AC) are used as the anode and cathode of an electric double-layer capacitor (EDLC). EDLC performs excellent supercapacitor performance. Boron–nitrogen-doped MWCNTs have potential application as high performance electric double-layer capacitor electrodes. [ABSTRACT FROM AUTHOR]

A 3-dimensional carbonized multi-walled carbon nanotube (MWCNT) paper was used as the host of nano-tin oxide (SnO2) for lithium-ion batteries (LIBs). The cellulose fibers were fully mixed with MWCNTs in water. Then, the paper was obtained via vacuum filtration. Carbonization was carried out in a vacuum furnace at 1460°C. SnO2 slurry was coated on the carbonized MWCNT paper (CMP). Scanning electron microscopy (SEM) was utilized to observe the anode electrode. The images of SEM indicated that the nano-SnO2 was embedded into the holes of the porous CMP collector. This contributed the increase of contact interface area of the nano-SnO2 and the collector and the significantly reduced interface resistance. Electrochemical tests showed that the initial discharge capacity reached 1745 mAh g−1 with a coulumbic efficiency (CE) of 70.39% at a current density of 50 mA g−1. The composite electrode still maintained a reversible capacity of 753 mAh g−1 with a CE of 98% at a current density of 200 mA g−1 after 100 cycles. These marvelous composite electrodes exhibited a promising future for the next generation of LIBs. [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotubes have been synthesized by floating reactant method in a vertical tubular reactor. An internal short approach process was developed to achieve the pre-lithiated multiwalled carbon nanotube MWCNTs/graphite composite anodes. Lithium-ion capacitors (LICs) were composed of a pre-lithiated multiwalled carbon nanotubes/graphite composite anode and an activated carbon (AC) cathode. The electrochemical performance of LICs with different MWCNTs content was investigated through galvanostatic charge/discharge and electrochemical impedance. The results show that the charge-discharge performance of LICs was greatly improved with the addition of MWCNTs in anodes. LIC25 (25 wt% MWCNTs) was found to achieve the optimal electrochemical performance. The LIC25 hold a specific capacitance of 58.2 F/g at the current density of 100 mA/g. The maximum energy density and power density were up to 96 Wh/kg and 10.1 kW/kg, respectively, in the current range of 100~8000 mA/g. The continuous galvanostatic charge-discharge cycling tests revealed that the LIC25 maintained excellent capacity retention of 86% after 3000 cycles. [ABSTRACT FROM AUTHOR]

A kind of flexible carbon nanotubes (CNTs) paper was investigated. Cellulose fibers were used as matrix and CNTs were used as conductive additive. The CNT papers were made by suction filtration method. The size and conductivity of the CNT paper can be arbitrarily tailored. The CNT papers show good electrical conductivity, electrochemical and electromagnetic interference (EMI) shielding properties. The electrical conductivity and (EMI) shielding effectiveness (SE) of CNT papers were enhanced with an addition of CNTs in the paper. The electrical conductivity increased from 9.92 S m −1 to 216.3 S m −1 and SE improved from 15 dB to 45 dB with a loading of CNTs from 10 wt% to 71 wt%. The CNT papers also show excellent applications for lithium ion battery, supercapacitors and zinc-manganese batteries. The testing results show that the capacity of supercapacitor reached 46 F/g at a scan rate of 5 mV/s. The reversible discharge capacity reached 474.0 mAh/g with the paper as anode current collector of lithium ion battery. The discharge capacity of Zn–Mn battery increased 100% when CNT paper replaced the graphite collector as current collector. [ABSTRACT FROM AUTHOR]

Sulfur is widely distributed in earth and is low cost and environmentally friendly. Lithium-sulfur battery was considered to be the next generation of new energy storage systems. However, the solubility, deposition, and shuttle effect of polysulfides of lithium-sulfur (Li-S) batteries checked the practical applications owing to low coulomb efficiency and the loss of active substances. Tris (2-carboxyethyl) phosphine (TCEP) can be used as a shear agent to transfer higher order lithium-polysulfide compounds (Li2Sx, x > 6) into low-order lithium-polysulfide compounds (Li2Sx, x < 4). The dissolution and diffusion of polysulfides were checked with an increase of utilization rate of active substances. The performance of charge and discharge and cycle of lithium-sulfur battery also were improved. Multi-walled carbon nanotubes (MWCNTs) provided high conductivity and maintained structural integrity of electrode, the diameter of MWCNTs is about 80 nm, and length is about 15 μm. The electrochemical test results showed that the first discharge capacity of electrode with TCEP interlayer reached 1410 mAh/g at a rate of 0.05 C, and the utilization rate of active material was as high as 84.6%. After 10 cycles at 3 C ratio, the discharge specific capacity still reached 526 mAh/g and the coulomb efficiency remained at 90.6%. It showed good rate and cycling performance. [ABSTRACT FROM AUTHOR]