Search

The main bottlenecks for the application of polymer electrolyte fuel cells in electric vehicles are the high cost and the inferior performance of Nafion at high temperatures above 80 °C. In this wo...

As one of the potential alternatives to graphite, non-graphitizable hard carbon (HC) is of great interest for its high capacity and better rate performance. It is generally accepted that the higher capacity of HC comes from the random arrangement of single graphene layers, which provides extra voids to accommodate lithium.1 However, its practical application is hindered by a large irreversible capacity and thus low initial Coulombic efficiency (ICE) (2 Chemical prelithiation is one of the most effective method to compensate the Li loss and thus improve the ICE. It refers to the application of Li-containing reagents with strong reducing capabilities, which transfer the Li ions to the anode materials along with the redox reaction.3-4 The operation is rather simple and shows great potential for industrial application with a suitable roll-to-roll design. In this study, the chemical prelithiation reagent, Li-biphenyl-tetrahydrofuran, was evaluated for its prelithiation capability in hard carbon electrodes through the immersion method. The prelithiation extent can be easily controlled by tuning the reaction time. A short time of 30 s results in a high ICE of ~106% in half cell. The improvement of ICE was evaluated in full cells as well. When matched with a LiNi1/3Co1/3Mn1/3O2 cathode, the full cell with the prelithiated hard carbon anode exhibits a much improved ICE and cycling performance than those of the pristine full cell. SEM, XPS, and EIS analysis were conducted to investigate the SEI difference between pristine and prelithiated samples, and the prelithiation mechanism was proposed. References (1) Nagao, M.; Pitteloud, C.; Kamiyama, T.; Otomo, T.; Itoh, K.; Fukunaga, T.; Tatsumi, K.; Kanno, R. Structure Characterization and Lithiation Mechanism of Nongraphitized Carbon for Lithium Secondary Batteries. J. Electrochem. Soc. 2006, 153, A914-A919. (2) Xing, W.; Dahn, J. R. Study of Irreversible Capacities for Li Insertion in Hard and Graphitic Carbons. Journal of The Electrochemical Society 1997, 144, 1195-1201. (3) Scott, M. G.; Whitehead, A. H.; Owen, J. R. Chemical Formation of a Solid Electrolyte Interface on the Carbon Electrode of a Li‐Ion Cell. J. Electrochem. Soc. 1998, 145, 1506-1510. (4) Tabuchi, T.; Yasuda, H.; Yamachi, M. Li-doping process for LixSiO-negative active material synthesized by chemical method for lithium-ion cells. J. Power Sources 2005, 146, 507-509.

Development of electric vehicles and portable electronic devices during the past decade calls for lithium-ion batteries (LIBs) with enhanced energy density and higher stability. Integration of FeF3 phases and carbon structures leads to promising cathode materials for LIBs with high voltage, capacity, and power. In this study, FeF3·0.33H2O nanoparticles were synthesized on reduced graphite oxide (rGO) nanosheets using an in situ approach. By chemically tuning the interfacial bonding between FeF3·0.33H2O and rGO, we successfully achieved high particle loading and enhanced cycling stability. Specifically, a discharge capacity of ∼208.3 mAh g–1 was observed at a current density of 0.5 C. The FeF3·0.33H2O/rGO nanocomposites also demonstrate great cycle capability with a reversible discharge capacity of 133.1 mAh g–1 after 100 cycles at 100 mA g–1; the capacity retention is about 97%. This study provides an alternative strategy to further improve the stability and performance of iron fluoride/carbon nanocomposi...

Silicon monoxide (SiO) is considered an attractive alternative to conventional graphite anodes due to its high specific capacity and good cycling performance. However, it suffers from low initial Coulombic efficiency (ICE) due to a large irreversible capacity and large volume change during cycling. Both deficiencies hinder the commercial use of SiO anodes. A new organolithium compound (Li−9,9-dimethyl-9H-fluorene−tetrahydrofuran) with lower redox potential is reported to prelithiate a SiO-based anode. An SEI layer is formed during prelithiation and a controllable amount of reversible lithium is preloaded into the SiO electrode. The ICE of a prelithiated SiO-based electrode in half-cell format is increased greatly to ~90.7%. When matched with a LiNi0·6Co0·2Mn0·2O2 cathode, the full cell with the prelithiated SiO/G anode exhibits a much improved ICE in comparison with the pristine one (87.1% vs. 61.1%). This facile prelithiation method is proved to be a practical solution for the commercial application of SiO-based materials.

The present study explored a new method to improve the catalytic activity of non-precious metals, especially in electrochemical reactions. Highly ionized Fe plasma produced by arc discharge was uniformly deposited on a porous carbon substrate and formed atomic clusters on the carbon surface. The as-prepared FeO x /C material was tested as a cathode material in a rechargeable Li–O2 battery under different current rates. The results showed significant improvement in battery performance in terms of both cycle life and reaction rate. Furthermore, X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the as-prepared cathode material stabilized the cathode and reduced side reactions and that the current rate was a critical factor in the nucleation of the discharge products.