The ability to store energy and release it as needed plays a surprisingly important role in our lives, so much so that we often forget how integral energy storage has become to a modern lifestyle. For instance, this thesis is written on a laptop, a device that is only possible due to significant advancements in battery technology over the course of decades. And as the performance of batteries has grown over the years, so too has the range of applications where they can play a part. While today it may seem inevitable that electric vehicles are set to replace their gasoline counterparts as automakers announce electrified lineups and countries announce electrification goals, it is easy to forget that just 10 years ago Tesla released their first electric vehicle to a skeptical public. Such a dramatic change in perspective is largely thanks to the precipitous drop in battery prices over that time period. Along a similar vein, renewable energy sources such as wind and solar have begun to provide a significant portion of the power in our electric grid, but their intermittency has created a need for large scale, cheap energy storage. We are already seeing batteries begin to play a role in this space, and the improvement of existing battery chemistries and development of new ones will only see their part grow. Between consumer electronics, electric vehicles, grid storage, and many more, the range of applications for batteries, in addition to the demands on them, is only growing. The scope of this thesis is dedicated to understanding some of these new battery chemistries, but to fully do so, it is instructive to look back at how we got to where we are today.
the mode of recycling constant current charge at 1 A within 30 s and constant power discharge at 0.1 W, 0.15 W, 0.2 W, 0.25 W, respectively, to calculate the specific energy and power. Considering that the electroactive species are dissolved or dispersed in moltensalt, we calculate the performance of MIB in the mass or volume of moltensalt. In detail, the weight of active iron metal was calculated by the theoretical values of iron metal that produced by the reduction of hematite under the charge current at 1 A within 30 s, and the weight of moltensalt was calculated by the theoretical values of the reduced hematite with the corresponding lithium carbonate and lithium oxide, for example, when 7.2 g hematite were reduced to 5.04 g iron, the weight of active iron metal was 5.04 g, and the weight of moltensalt was 30 g. The volume of moltensalt was measured via a fast draining method after a process of melting moltensalt under 800 ° C and then rapid cooling at room temperature. The columbic efficiency was
Sulfur (S) has been considered as a promising cathode candidate for lithiumbatteries due to its high theoretical specific capacity and energy density. However, the low active material utilization, severe capacity fading, and the short lifespan of the resultant lithium-sulfur (Li-S) batteries have strongly hindered their practicality. In this work, a multi-functional polyacrylonitrile/silica nanofiber membrane with an integral ultralight and thin multi-walled carbon nanotube sheet is presented and demonstrates a new approach to significantly improve the overall electrochemical performance of Li-S batteries. The experimental results are in agreement with molecular modeling studies based on density functional theory and Monte Carlo simulations. Remarkably, this design is favorable for the fast diffusion of both lithium ions and electrons, and mitigating the diffusion of polysulfides. As a consequence, a high reversible capacity of 741 mAh g -1 at 0.2C after 100 cycles with excellent cyclability and high- rate performance (627 mAh g -1 at 1C) are achieved even with a high sulfur loading of 70 wt% in the cathode, revealing its great potential for energy storage applications. Moreover, a capacity of 426 mAh g -1 is retained after 300 cycles at a high current density of 2C. These results represent a major step forward in the progress of Li-S battery technologies.
power as high as 5.5 mW·cm -2 (more than 4 times of LOB cathode power density) at high currents up to 4 mA·cm -2 and retained high-energy delivery at low currents as 0.01 mA·cm -2 . Besides, the discharged hybrid cathode presented the capability of self-recovery to charged-state while resting in oxygen (the capacity recovery percentage kept around 80% in each resting process), and the durability of high-power output was enhanced by this behavior. This work may provide a new approach to promote the development of lithium-oxygenbatteries.
attracted particular attention owing to their high theoret- ical capacities (>330 mAh g − 1 ) and good thermal stability through strong Si-O bond [1-3]. However, the practical discharge capacity is mainly achieved below 3.5 V, result- ing in a lower cell energy density. Substituting Si atom for Ti atom leads to another attractive cathode material of Li 2 MTiO 4 (M = Fe, Mn, Co, Ni) with high theoretical
space group. Weak superstructure peaks observed around 2θ = 20-25 o are known to correspond to the ordering of the lithium ions and transition metal ions in the transition metal layer of the layered lattice[8,19]. Speaking of the hydrothermal product at 140°C for 24 h, the intensity of reflection peaks is relatively lower, demonstrating not good crystallinity as samples prepared at 160°C and 180°C. Furthermore, reflection peaks correspond to (006) and (012) directions can not be clearly distinguished, which also indicates not so good layered structure. By comparison of samples obtained at 160°C for 24 h with sample prepared at 180°C for 24h , although we can easily distinguish the reflection peak of (006) direction from (012) , with increasing hydrothermal temperature T h , the peak
method. The surface morphology and its composition have been characterized by X-ray diffraction, inductively coupled plasma, Field-emission scanning electron microscopy and Energy Dispersive Spectrometer. The physicochemical properties and electrochemical properties of the materials also have been investigated, and show that the as-prepared electrodes exhibit excellent cycling and rate performance than the LiNi 0.5 Mn 1.5 O 4 electrodes. It is considered that a little Fe 3+ doping suppresses the
Electrochemical properties of the prepared samples were measured using Swagelok-type two- electrode cells. The working electrodes were pressed with a mixture of 80 wt.% active materials, 15 wt.% acetylene black, and 10 wt.% polytetrafluoroethylene (PTFE) binders. Then, the prepared electrodes were dehydrated by a vacuum dry at 60 ℃ for 12 h and were cooled down to room temperature. The cells assembled in an MBraun glove box filled with pure argon gas. A lithium disk served as counter and reference electrodes. The electrolyte was 1M LiPF 6 dissolved in ethylene
was cast onto an aluminum current collector and then dried at 120 °C for 12 h under vacuum. The charge/discharge behaviors of the prepared samples were tested using CR2032 coin cells containing a cathode, a Celgard 2300 membrane as the separator, a lithium foil anode, and the electrolyte (1 mol L −1 LiPF 6 inEC/DMC (1:1 by volume)). The cyclic voltammetry (CV) and electrochemical impedance
Herein, we develop a novel electropolymerized PPy nanofiber matrix grown on the Ni foil as a flexible substrate for the deposition of sulfur nanoparticle. In this well-designed configuration, sulfur was homogeneously coated on the surface of PPy matrix. The inactive PPy core canconveniently maintain the structural integrity of the compositeand facilitate the charge collection and transport. PPy nanofiber also has strong adhesion to the surface of Ni foil and absorbpolysulfides into its porous structure. Furthermore, binders and conductive agents are rendered unnecessary in this free-standing S/PPyelectrode, thereby simplifying its preparation. And the physical and electrochemical properties of the binder-free S/PPy cathodewere investigated for Li/S batteries.
Figure 5 shows a comparison of the relative standard deviations of this method with those of different methods reported in the literatures for the determination of (a) nickel; (b) cobalt and (c) manganese contents in cathode materials of lithium ion batteries. From the Figure 5, it can be seen that the obtained relative standard deviation values for determination of nickel, cobalt and manganese of this work is very low as compared with other reports [18-36]. Also, the relative standard deviations are 1.5-7% by instrumental analysis, which is adequate to trace analysis by multiple diluting macro analysis solution to about 100 ppm. The relative standard deviation of our method is only 0.9%, which is not required too much dilution of the solution, indicating the better accuracy of this new method.
In this paper, hollow S@NiS sphere composites are developed and designed as cathode materials for the lithium-sulfur batteries. This unique hollow sphere structure could provide a place for the storage of the soluble polysulfide. Therefore, the shuttle effect of the polysulfide in the lithium- sulfur battery could be effectively inhibited during the discharging and charging process. As a result, the hollow S@NiS composites show excellent cycle stability and high specific capacity. In all, this work may provide a promising method for synthesizing the cathode materials for the lithium-sulfur batteries.
Last, ZnO-coated layer minimizes the harmful side reactions within the batteries by isolating the oxidizing cathode material and liquid electrolyte. These mechanisms together lead to an electrochemically synergistic effect that contributes to the excellent cycleability of 2 wt.% ZnO-coated LiV 3 O 8 sample.
Remarkable progress has been made in developing high performance lithium-sulfur batteries, especially in the development cathodes with highenergy densities. In this view, the key points for the development of excellent lithium-sulfur batteries cathodes are highlighted in the following areas: sulfur-containing nanotubes/nanofibers, graphene-sulfur electrodes and porous carbon sulfur composites. In addition, the current challenges in this field for practical applications of lithium-sulfur batteries are further discussed.
state (see “Methods” section and Supplementary Fig. 11). The geometries and electronic states of oxalate were then examined using Raman and soft X-ray Absorption Spectra. Figure 3a shows Raman spectra of the pristine LFOx (black), LFOx mixed with conductive carbon for cathode (blue), initial cathode (green) and charged cathode in in-situ cells (red). Corresponding assignments of Raman peaks of pristine LFOx are stated in Supplementary Fig. 12 and Supplementary Table 8. In Fig. 3a, the strong and broad Raman peaks at 1342 and 1600 cm −1 are consistent with D-band and G-band vibrations, respectively, originating mainly from conductive carbon black and additive. The characteristic peaks at I (917 cm −1 ) and II (1485 cm −1 ) arose from LFOx, which were assigned to C–C symmetric and C = O asymmetric stretching 32 – 34 , as schematically illustrated in Fig. 3b. Other peaks from the pristine sample become difﬁcult to identify after assembling the in-situ cell, mainly because of noise from carbon additive, electrolyte, cell window, etc. Comparing the spectra of initial and charged cathodes in in-situ cells (green and red in Fig. 3a), it is apparent that both I and II became weaker after charging, indicating that the concentration of corresponding C–C and C = O groups is decreasing, evidence of geometry changes of the oxalate groups. Additionally, peak II became narrower and shifted towards higher wavenumbers in charged states (Supple- mentary Fig. 13), indicating that the double bond in C = O becomes more localized and stronger. The intensity evolution for the peak I and II as a function of time conﬁrmed the periodic changes of peak I and II (Supplementary Fig. 14). Further, from in-situ Raman patterns (Fig. 3c, d), the intensity of peaks (I and II) experienced periodic ﬂuctuations during cycling, demon- strating excellent reversibility of these changes.
high reversible capacities with excellent cyclic capacity retention at a relatively high charge/discharge rate. Besides, such 2D transition metal chalcogenides (TMDs) materials with a single layer or few layers have been proposed to be used as anode materials in LIBs by reason of the abundant adsorption sites and short Li + diffusion channels, such as MoS 2 [10-12], WS 2 , VS 2 , SnS 2 , and TiS 2 ,
Figure 8b shows the rate performances of the compos- ites. Both V/GO-I and V/GO-II composite electrodes ex- hibit good rate capability. The capacities vary slightly for the composites less than 8C. However, the rate perform- ance of the V/GO-I composite becomes obvious at rates higher than 16C. A specific capacity of 133 mA h g −1 can be obtained for V/GO-I composite even at 16C, which is very close to the theoretical capacity of 147 mA h g −1 for one lithium-ion intercalation per for- mula. Moreover, almost no capacity fade is detected at 32C and 40C. Even at 64C, the V/GO-I composite can still deliver a specific discharge capacity of 122 mAh g −1 . However, the capacity decreases much faster at high rates (>16C) for V/GO-II composite. The corresponding charge/discharge curves are shown in Additional file 1: Figure S3. The composite electrodes deliver specific dis- charge capacities of 108, 85, 74, and 50 mA h g −1 at 16C, 32C, 40C and 64C, respectively. When the dis- charge/charge rates were reset to 1C, high discharge capacity of 139 mAh g −1 can be recovered for both
lithium ions below the maximum potential during cathode charging, but active lithium ions almost cannot be embedded back into the cathode under the minimum potential during cathode discharging. Thirdly, such prelithiation additives have prominent compatibility with the active materials, common solvents and suitable binders during the preparation processes of the existing lithium ion batteries . Wenquan Lu et al. claimed that the LiNi 0.5 Co 0.2 Mn 0.3 O 2 /SiO full cell with 9.1% Li 5 FeO 4 additive was
EIS is one of the most powerful tools to analyze electrochemical reactions, such as those processes occurring at electrode/electrolyte interfaces and the lithium ion intercalation/deintercalation occurring in anode/cathode, and has been widely reported in the previous literature [17, 19-26]. The Nyquist plots of electrochemical lithium ion deintercalation from oxide-based electrodes (corresponding to the charge processes) commonly consist of three parts: the first arc in the high frequency range, the second arc in the medium frequency range and an approximate straight line inclined at a constant angle to the real axis in the lower frequency range. Though the dependence of Nyquist plots for impedance spectra on state of charge (SOC) does not come to an agreement among researchers, it is acknowledged that every part of the plots can indicate some electrochemical characterizations of electrode materials [27-31, 42]. In this study, EIS is employed to investigate the influence of SnO 2 on the electrochemical performance of LiMn 2 O 4 , especially the resistance of solid
the corresponding tools for subduing capacity are now required to advance the performance of Li-S batteries. In this work, carbon coated Sulfur / polymer composite was prepared by solvent less reaction. The physical characterizations of the prepared composite was investigated using XRD, RAMAN and SEM. Raman analysis specifies that D and G bands were well matched with the sulfur based ternary composite. The functional group vibration of the ternary composite was studied using FTIR. The XRD pattern reveals that the diffraction peaks of sublimed sulfur was clearly observed in the ternary composite, which is due to the limited pore volume of the carbon matrix. The prevailing study indicates that sulfur based ternary composite is a promising candidate for the cathode material mainly in Lithium Sulfur Battery.