Coal-based carbon anodes for high-performance potassium-ion batteries

TL;DR: In this article , the authors provide an up-to-date overview of the rapidly developing field of carbon-based electrode materials for potassium-ion batteries and provide guidance on carbon material design principles for next-generation potassium ion storage devices.

TL;DR: In this article, a simple ball mill-thermal treatment method is developed to prepare S/O co-doped soft carbons (SO-SC) using 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) as precursor.

TL;DR: In this paper, a facile molten-salt-mediated production of ultrathin carbon nanosheets with tunable nitrogen doping using low-cost precursors including asphalt and melamine is proposed.

TL;DR: In this paper, a simple process for fabricating ruthenium oxide (RuO2) nanoparticle (NP)-based ultrathin film electrodes with a Tvis of 97.1% and CA of 0.85 mF cm−2 was demonstrated.

TL;DR: To improve the performance of carbon K-ion anodes, this work synthesized a nongraphitic soft carbon that exhibits cyclability and rate capability much superior to that of graphite.

Abstract: DOI: 10.1002/aenm.201501874 its spherical morphology well without surface cracking of the spheres, which explains its excellent capacity retention of 83% after 100 cycles. HCS is obtained by a hydrothermal reaction of dissolved sucrose, followed by pyrolysis. [ 10 ] The obtained product comprises carbon microspheres with diameters of around 5–10 μm ( Figure 1 a), and these spheres are of a fairly porous surface texture, as shown in the high resolution transmission electron microscopy (HRTEM) image (Figure 1 b). HCS exhibits a Brunauer–Emmett–Teller (BET) specifi c surface area of 65 m 2 g −1 . The nongraphitic hard carbon nature of HCS is revealed by X-ray diffraction (XRD) and Raman spectra. The XRD pattern of HCS shows a broad (002) peak, indicating a small stacking height of graphene layers, i.e., an average L c of ca. 1.4 nm estimated according to the Scherrer equation (Figure 1 c). Compared to the d-spacing of 0.335 nm in crystalline graphite, HCS exhibits an average inter-layer distance of ca. 0.400 nm, revealed by the position of the (002) peak. The Raman spectrum of HCS is very typical for nongraphitic carbon materials, which contains the D-band more intensive than the G-band, where they are assigned to A 1g vibration mode of sp 2 carbon rings caused by defects and E 2g vibration mode of sp 2 carbon atoms, respectively (Figure 1 d). We fi rst investigated the charge/discharge properties of the HCS electrode in KIBs, as compared to NIBs. Figure 2 a shows the typical potassiation/depotassiation potential profi les, where there is a high-potential sloping region and a low-potential quasiplateau region. Considering the available alkali metal ion storage mechanisms for hard carbon anodes, the two potential regions should correspond to K-ion insertion into different substructures or structural sites inside HCS, i.e., edges or defective sites of turbostratic nanodomains (TNs), inter-layer space inside TNs, and voids between TNs. [ 11 ] At C/10 (28 mAh g −1 ), the HCS/K cell presents a reversible capacity of 262 mAh g −1 in the depotassiation process, which is lower than 322 mAh g −1 from the HCS/Na cells (Figure 2 b). Furthermore, it is worthwhile pointing out that a capacity contribution of 200 mAh g −1 , 60% of the total capacity in HCS/Na cells, comes from its plateau region, where the sodiation potential is below 0.1 V versus Na + /Na. In contrast, it is only ca. 50 mAh g −1 , less than 20% of its total capacity in HCS/K cells, that is gained at potentials lower than 0.1 V versus K + /K. The difference in redox potentials between HCS/K and HCS/Na cells is more evident in the corresponding d Q /d V profi les (Figure 2 c,d). The HCS/K cell exhibits its potassiation and depotassiation peaks at 0.2 and 0.33 V versus K + /K, respectively, while both sodiation and desodiation peaks in the HCS/Na cell are lower than 0.1 V versus Na + /Na. When metal ion insertion occurs at potentials too close to the plating of the corresponding metal, dendrite formation can be a serious concern, particularly at high current rates. Great needs for electrochemical energy storage come from not only transportation but also stationary applications, e.g., home solar-power storage, microgrids, and load leveling. [ 1 ] However, for state-of-the-art lithium-ion batteries (LIBs), lithium is simply too rare to be deployed in stationary facilities. [ 2 ] Therefore, there arises tremendous interest in alternative Earth-abundant metalion batteries, among which, sodium-ion batteries (NIBs) attract most attention due to the abundance of sodium and its similar “rocking chair” operation principle as LIBs. [ 3 ] Great progress has been made on new electrode materials for NIBs. [ 4 ]

TL;DR: Improved extrinsic pseudocapacitive contribution is demonstrated as the origin of fast kinetics of an alloying-based SnS2 electrode and the S-edge effect on the fast Na+ migration and reversible and sensitive structure evolution during high-rate charge/discharge is verified.

TL;DR: It is reported for the first time that potassium (K) ions can electrochemically intercalate into graphitic materials, such as graphite and reduced graphene oxide (RGO) at ambient temperature and pressure.