No abstract

Herein, we present the upscaled synthesis of nanoparticulate Li 4 Ti 5 O 12 (LTO) by means of flame spray pyrolysis (FSP), yielding high phase purity and appropriate morphology for application as high-power lithium-ion anode material. Electrodes based on this optimized LTO nanopowder, carboxymethyl cellulose (CMC) as binder, and copper as current collector revealed excellent rate performance, providing specific capacities of 133, 131, 129, 127, 124, and 115 mAh g −1 when applying C rates of 1C, 2C, 5C, 10C, 20C, and 50C, respectively. Targeting the commercial application of thus synthesized nanoparticles, we optimized also the electrode composition, comparing three different binding agents (CMC, PVdF, and poly(acrylic acid), PAA) and substituting the copper current collector by aluminum. The results of this comparative analysis show, that the combination of nanoparticulate LTO, CMC, and an aluminum current collector appears most suitable toward the realization of environmentally friendly and cost-efficient lithium-ion anodes, presenting very stable cycling performance for more than 1000 cycles at 10C without substantial capacity decay. While lithium-ion batteries are already the energy storage device of choice for portable electronic devices, they are recently gaining importance for large-scale applications like (hybrid) electric vehicles and stationary energy storage.1-5 However, beside advances regarding the energy density, such applications still require an improved safety, long-term cycling stability, as well as enhanced power densities with respect to state-of-the-art lithium-ion cells, commonly employing graphite as anode material.1-5 Spinel-structured Li 4 Ti 5 O 12 (LTO), reported for the first time by Colbow et al. in 1989, 6 is presently considered as one of the most promising alternative anode materials for realizing safer, long-lasting, high power lithium-ion batteries 7-13 and is, for such reasons, already utilized in commercial cells.2 While the enhanced safety and advanced long-term cycling stability, resulting from the relatively higher lithium (de-)insertion potential and the negligible volume variation upon (de-)lithiation, 14-17 respectively, are, to a great extent intrinsic to LTO, the high power performance, i.e., the rate capability, of the material is highly dependent on the utilized synthesis method and the resulting particle size and morphology. 9,13,[18][19][20][21] Indeed, downsizing the particle size to the nanometer-scale resulted in excellent power performance, 21-25 allowing (dis-)charging LTObased electrodes in as little as a few seconds. However, one of the major challenges toward the commercialization of nano-sized LTO is the development of easily scalable synthesis methods, providing large batches of active material at competitive prices.13 A highly attractive method for the large-scale preparation of metal oxide nanoparticles appears to be flame spray pyrolysis (FSP). 26,27 We have recently reported the electrochemical characterization of the first generation of FSP-synthesi...

No abstract

Non-fluorinated Li3V1.95Ni0.05(PO4)3/C-based electrodes were prepared by using sodium carboxymethyl cellulose, sodium alginate and poly(acrylic acid) as alternative binders of the standard poly(vinylidene difluoride). The effect of the binders was investigated on several aspects, starting from the rheological properties of the dispersions, to the physical-chemical properties of the layers (adhesion test, electrode porosity, surface conductivity). The prepared Li3V1.95Ni0.05(PO4)3/C-based electrodes were characterized as cathodes at different C-rates ranging from 1 C to 200 C in two different potential windows, between 3.0–4.3 and 3.0–4.8 V vs. Li/Li+. The cycle life of the LVNP/C-based electrodes was characterized for each potential window at C-rate as high as 100 C and for 10000 cycles. Electrochemical impedance spectroscopy, scanning electrode microscopy, X-ray diffraction and energy dispersive X-ray measurements were used to study the aged electrodes. Among the electrodes, the one prepared with Na-alginate binder displays the best electrochemical performance, with a specific capacity of 100 and 85 mAh g−1 delivered at 100 C when charged up to 4.3 and 4.8 V vs. Li/Li+, respectively. Moreover, in the same potential windows, it displays an excellent cycling stability over 10000 cycles at 100 C, with a capacity retention of 80% and 65%

This work is dedicated to the memory of Prof. Roberto Marassi, to thank him for his passion and his immeasurable contribution to the research in the electrochemistry field. He also instilled love for Electrochemistry to his research group and his students.Two lithium-ion hybrid supercapacitors (LiHSs) based on high power active materials like Li 3 V 1.95 Ni 0.05 (PO 4 ) 3 /C (LVNP/C), Li 4 Ti 5 O 12 (LTO) and activated carbon (AC) are investigated as high energy and high power devices. Both LiHSs are assembled by using a bi-material negative LTO:AC electrode (50 : 50), able to deliver 38.3 mAh g À 1 at 35 A g À 1 (200 C for LTO), and to retain 80 % of the initial capacity over 10000 cycles at 17.5 A g À 1 . Two positive electrodes are employed in complete devices: a battery-type LVNP/C and a bi-material LVNP/C:AC (65 : 35) based electrodes, for two LiHSs named Hybrid A and Hybrid B, respectively. The energies of the LiHSs are evaluated from 0.05 to 10 A g À 1 , and at different cell voltages (2.6, 2.7 and 2.8 V). The best performance is obtained with Hybrid A cycled between 0-2.7 V, that with 36.3 Wh L À 1 at 4.3 kW L À 1 , possesses an energy density five time higher than that of the AC j j AC (6.8 Wh L À 1 ). Despite both LiHSs charged up to 2.8 V possess superior energy values, at this cell voltage Hybrid A and Hybrid B retain only 11 % and 8 % of the initial capacity cycled over 8000 cycles at 10 A g À 1 , respect to the 75 % and 81 % of the same systems cycled up to 2.7 V.