Electrochemical investigation of ion-beam sputter-deposited carbon thin films for Li-ion batteries

Abstract

The C-rate capability of 230 nm- and 16 nm-thin ion-beam sputter-deposited amorphous carbon films, an interesting class of carbonaceous material for lithium-ion batteries, was investigated up to Li-platting. Stepwise ascending and descending constant Li+ currents after each fifth cycle, followed by hundreds of cycles with the highest current were applied. The carbon films show similar cycling with irreversible losses during the first five cycles, followed by reversible cycling with a capacity close to that of graphite. The capacity is significantly lower at high currents; however, it is restored for subsequent cycling again at low currents. Differential charge and differential capacity curves reveal three Li+ uptake and three Li+ release peaks located between 0 and 3 V. Irreversible as well as reversible Li bonding can be associated with all these peaks. Irreversibly bonded Li can be found at the surface (solid electrolyte interphase) and in the bulk of the carbon films (Li trapping). Reversible Li bonding might be possible inside the carbon films in graphite-like nano-domains and at defects. The thinner film reveals a more pseudo-capacitive cycling behavior, pointing to enhanced Li kinetics. Graphical abstract

Lithium Niobate for Fast Cycling in Li-ion Batteries: Review and New Experimental Results

“…Note, however, that LiNbO 3 also has disadvantages. The operation voltage of a LiNbO 3 cell is lower than that of a Li metal cell or even a silicon [29,30] or graphite [27,28] cell. This reduces the cell energy density and power level of the cell.…”

“…The film thickness was determined using X-ray reflectometry (XRR) as described in Ref. [27]. Grazing incidence X-ray diffraction (GI-XRD) and XRR were measured with a Bruker D8 DISCOVER (Germany) diffractometer using Cu Kα radiation.…”

“…Differential charge (dQ) plots (dQ/dV) were derived from CC measurements as described in Ref. [27]. Direct comparisons between CV and dQ/dV plots are given within this work.…”

“…The schematized positive electrode (called also cathode) is an oxide such as LiNi x Mn y Co z O 2 (NMC), which will often be mentioned in this review. Figure 1a shows a scheme of commercial batteries where the negative electrode (called also anode) contains graphite [27,28] as the electrochemically active material. More charge can be stored if the negative electrode encompasses silicon [29,30] (Figure 1b).…”

“…to cite only some of the work on positive electrodes). Carbon (e.g., graphite) [27,28] and silicon [29,30] are utilized as Li + storage media, i.e., as electroactive material for negative electrodes. Since recently, the introduction of lithium niobate (LiNbO 3 ) in LIB is considered to boost stability (integrity) and fast operation even for high-voltage (i.e., towards 5 V) LIBs, as it is further outlined in the next section.…”