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In order to inhibit the formation of lithium dendrites and solid electrolyte interface films, prevent the corrosion of electrolyte to lithium powder (Li) and improve the electrochemical properties of a lithium ion capacitor (LIC), the lithium powder was fluorinated at high temperature under the protection of nitrogen (N2) by using perfluororesin (CYTOP) as the fluorine source to obtain lithium/lithium fluoride powder (Li@LiF). Li@LiF was pre-embedded in the LIC-cathode sheet and assembled into the LIC. Scanning electron microscopy and x-ray diffraction were used to analyze and test the materials and electrode sheets. The electrochemical properties of the LIC were studied by constant-current charge and discharge (GCD) and electrochemical impedance spectroscopy. Experimental results showed that the lithium powder was successfully fluorinated, and that Li@LiF pre-embedded in the cathode can modify the electrochemical properties of the devices that store electrical charge. The specific capacitance of GCD reached 51.92 F g−1 at a current density of 50 mA g−1. In the range of 50 mA g−1 to 700 mA g−1, the smallest power density reached 68.51 Wh kg−1 and the highest energy density reached 1.02 kW kg−1. After 2000 invariant current charge and discharge cycles, the capacitance remained at about 96%.

A novel type of graphite sheet (GS) flexible electrode was obtained from high-temperature carbonized polyimide film. The GS establishes an excellent conductive network and promotes the transfer of electrons. In order to ensure the carrying capacity of tin oxide, the surface of the GS was coated with a layer of multi-walled carbon nanotube (MWCNT) slurry, and then coated with tin oxide. The fluffy porosity of MWCNT coating is an excellent carrier of tin oxide, which inhibits the volume expansion of tin oxide to a certain extent. Through repeated tests, the electrochemical performance of the electrode is best when the coating thickness is 0.3 mm.

In this paper, we develop a simple annealing method to prepare three-dimensional (3D) honeycomb porous carbon (Co-PC) as an interlayer material. Co2+ was introduced by redox reaction to improve the initial coulombic efficiency and boost the specific capacity of the electrodes; CoS obtained during the S melt-diffusion process served as redox catalyst. The 3D interconnected porous structure of the Co-PC interlayer was found to effectively adsorb polysulfide to inhibit the shuttle effect. Remarkable cycling stability was obtained, and a high reversible capacity of 803 mAh/g with a negligible fading rate of 0.024% per cycle at 1C was obtained after 200 cycles.

Lithium ions were inserted into the electrodes of tin oxide to eliminate the first irreversible capacity of the Li-SnO2 batteries. The stabilizing SEI film was obtained from pre-embedding lithium. Thereby, first irreversible capacity of the Li-SnO2 batteries is prevented with significantly increasing the specific capacity and reducing the damage. As a result, the SnO2@Li/MWCNTs electrodes exhibited outstanding electrochemical performance, first discharge specific capacity reached 1700.15 mAh g−1, and the utilization rate of active materials reached as high as 95.89% at 100 mAh g−1. After 100 cycles, the specific discharge capacity remained greater than 499.94 mAh g−1, with a coulombic efficiency of 99.77%.

Activated carbon (AC) was acidified with dilute sulfuric acid (H2SO4) as an acidifying agent to obtain acidified activated carbon (HAC). The positive electrode was prepared by mixing HAC with a conductive agent (SP) or polyvinylidene fluoride. Carbon nanotubes and mesocarbon microbeads, as negative materials, were prelithiated and used as the negative eletrode. The positive electrode and negative electrode were assembled into the lithium ion capacitor. Materials and electrodes were characterized by scanning electron microscopy; elemental analysis, chemical bond analysis and specific surface area analysis of acidified activated carbon were made by x-ray energy spectrum analysis, an intelligent Fourier transform infrared spectrometer and specific surface space as well as a porosimetry analyzer (BET); The electrochemical capability of lithium ion capacitors was tested by constant current charge and discharge as well as electrochemical impedance. From the results, it can be concluded that the activated carbon acidified successfully grafted with hydroxyl (OH) and carboxyl (COOH) functional groups has increased the surface area by about 60% compared with AC. Under this situation, the charge and discharge current density is 50 mA/g. Also the capacitor has a mass ratio of 40.17 F/g, whose maximum power density is 0.98 kW/kg (700 mA/g) and maximum energy density is 52.34 Wh/kg (50 mA/g). Impedance tests showed that it has low impedance characteristics; the capacitance retention rate is above 60% after 2000 cycles of charge and discharge; the energy density can still reach 21.68 Wh/kg with a power density of 0.98 kW/kg. The electrochemical capability of the lithium ion capacitor was improved with acidified activated carbon as positive electrode.

In this paper, a SnO2@C composite anode was prepared by coating SnO2 with asphalt by hydrothermal process and carbonization. The core–shell structure of SnO2 nanoparticles was characterized by scanning electron microscopy, energy-dispersive spectrometry, x-ray diffraction and thermal gravimetric analysis. The electrochemical performance tests showed the SnO2@C anode exhibited excellent cycle performance and high specific capacity. The core–shell structure can accommodate the huge volume expansion of SnO2 nanoparticles during charge/discharge. The conductivity of the electrode was also obviously enhanced. The first-charge capacity and coulombic efficiency reached 1798 mAh/g and 65%, respectively. After 80 cycles, the capacity still remained at 446 mAh/g at a current density of 100 mA/g.

Lithium–sulfur batteries have become one of the most promising high-energy batteries owing to their high energy density and low cost. Nevertheless, one of the major problems is the infamous shuttle effect of polysulfides, which causes active material sulfur loss and low Coulombic efficiency. Here, we designed a 3-D configuration electrodes. Multi-walled carbon nanotubes paper (MWCNTsP) was used as the current collector, and MWCNTs film was used as the interlayer (MWCNTsI) between the positive electrode and the separator. The unique configuration retarded the dissolution and dispersion of polysulfides. The electrochemical tests showed that the initial discharge capacity reached 1352 mAh/g and the Coulombic efficiency reached around 100% with the 3-D configuration electrode (MWCNTsP–S@MWCNTsI). The discharge capacity remained 1028 mAh/g after 20 cycles. Additionally, the batteries maintained a specific capacity of 902 mAh/g, 782 mAh/g and 509 mAh/g at the current rate of 1 C, 2 C and 5 C, respectively.

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.