Energy Material Advances
EISSN : 2692-7640
Published by: American Association for the Advancement of Science (AAAS) (10.34133)
Total articles ≅ 29
Latest articles in this journal
Published: 12 October 2021
Energy Material Advances, Volume 2021, pp 1-13; https://doi.org/10.34133/2021/9769347
Ca-ion batteries (CIBs) have the potential to provide inexpensive energy storage, but their realization is impeded by the lack of suitable electrolytes. Motivated by recent experimental progress, we perform ab initio molecular dynamics simulations to investigate early decomposition reactions at the anode-electrolyte interface. By examining different combinations of solvent—tetrahydrofuran (THF) or ethylene carbonate (EC)—and salt—Ca(BH4)2, Ca(BF4)2, Ca(BCl4)2, and Ca(ClO4)2—we identify a variety of behavioral trends between electrolyte solutions. Next, we perform a separate trajectory with pure THF and gradually increased negative charge; despite an addition of -32, no THF decomposition is detected. Charge analysis reveals that in a reductive environment, THF distributes excess charge evenly across its hydrocarbon backbone, while EC concentrates charge on its ester oxygens and carbonyl carbon, resulting in decomposition. Graphs of charge vs. time for both solvents reveal that EC decomposition products can be reduced by up to five electrons, while those of THF are limited to a single electron. Ultimately, we find Ca(BH4)2 and THF to be the most stable solution investigated herein, corroborating experimental evidence of its suitability as a CIB electrolyte.
Published: 1 October 2021
Energy Material Advances, Volume 2021, pp 1-11; https://doi.org/10.34133/2021/9795825
The high-capacity phosphorus- (P-) based anode materials for sodium-ion batteries (NIBs) often face poor performance retentions owing to the low conductivity and large volume expansion. It is thus essential to buffer these problems by appropriately alloying with other elements such as tin (Sn) and constructing well-designed microstructures. Herein, a series of P-/Sn-based composites have been synthesized by the facile and low-cost one-step ball milling. Pair distribution function (PDF) has been employed as a hardcore quantitative technique to elucidate their structures combined with other techniques, suggesting the formation and ratios of Sn4P3 and Sn crystalline domains embedded inside an amorphous P/carbon matrix. The composite with the largest amount of Sn4P3 in the P/C matrix can deliver the most balanced electrochemical performance, with a capacity of 422.3 mA-h g−1 for 300 cycles at a current density of 1000 mA g−1. The reaction mechanism has been elucidated by 23Na and 31P solid-state nuclear magnetic resonance (NMR) investigations. The study sheds light on the rational design and concrete identification of P-/Sn-based amorphous-dominant composite materials for NIBs.
Published: 15 September 2021
Energy Material Advances, Volume 2021, pp 1-14; https://doi.org/10.34133/2021/9895403
Magnesium-ion-conducting solid polymer electrolytes have been studied for rechargeable Mg metal batteries, one of the beyond-Li-ion systems. In this paper, magnesium polymer electrolytes with magnesium bis(trifluoromethane)sulfonimide (Mg(TFSI)2) salt in poly(ε-caprolactone-co-trimethylene carbonate) (PCL-PTMC) were investigated and compared with the poly(ethylene oxide) (PEO) analogs. Both thermal properties and vibrational spectroscopy indicated that the total ion conduction in the PEO electrolytes was dominated by the anion conduction due to strong polymer coordination with fully dissociated Mg2+. On the other hand, in PCL-PTMC electrolytes, there is relatively weaker polymer–cation coordination and increased anion–cation coordination. Sporadic Mg- and F-rich particles were observed on the Cu electrodes after polarization tests in Cu|Mg cells with PCL-PTMC electrolyte, suggesting that Mg was conducted in the ion complex form (Mg x TFSI y ) to the copper working electrode to be reduced which resulted in anion decomposition. However, the Mg metal deposition/stripping was not favorable with either Mg(TFSI)2 in PCL-PTMC or Mg(TFSI)2 in PEO, which inhibited quantitative analysis of magnesium conduction. A remaining challenge is thus to accurately assess transport numbers in these systems.
Published: 7 September 2021
Energy Material Advances, Volume 2021, pp 1-16; https://doi.org/10.34133/2021/9786201
In this work, we for the first time developed a novel lithium-containing crosslinked polymeric material, a lithicone that enables excellent protection effects over lithium (Li) metal anodes. This new lithicone was synthesized via an accurately controllable molecular layer deposition (MLD) process, in which lithium tert-butoxide (LTB) and glycerol (GL) were used as precursors. The resultant LiGL lithicone was analyzed using a suite of characterizations. Furthermore, we found that the LiGL thichicone could serve as an exceptional polymeric protection film over Li metal anodes. Our experimental data revealed that the Li electrodes coated by this LiGL lithicone can achieve a superior cycling stability, accounting for an extremely long cyclability of >13,600 Li-stripping/plating cycles and having no failures so far in Li/Li symmetric cells at a current density of 5 mA/cm2 and an areal capacity of 1 mAh/cm2. We found that, with a sufficient protection by this LiGL coating, Li electrodes could realize long-term stable cyclability with little formation of Li dendrites and solid electrolyte interphase. This novel LiGL represents a facile and effective solution to the existing issues of Li anodes and potentially paves a technically feasible route for lithium metal batteries.
Published: 6 September 2021
Energy Material Advances, Volume 2021, pp 1-12; https://doi.org/10.34133/2021/9761263
Nitrate is a crucial environmental pollutant, and its risk on ecosystem keeps increasing. Photocatalytic conversion of nitrate to ammonia can simultaneously achieve the commercialization of environmental hazards and recovery of valuable ammonia, which is green and sustainable for the planet. However, due to the thermodynamic and kinetic energy barriers, photocatalytic nitrate reduction usually involves a higher selectivity of the formation of nitrogen that largely limits the ammonia synthesis activity. In this work, we reported a green and facile synthesis of novel metallic ruthenium particle modified graphitic carbon nitride photocatalysts. Compare with bulk graphitic carbon nitride, the optimal sample had 2.93-fold photocatalytic nitrate reduction to ammonia activity (2.627 mg/h/gcat), and the NH3 selectivity increased from 50.77% to 77.9%. According to the experimental and calculated results, the enhanced photocatalytic performance is attributed to the stronger light absorption, nitrate adsorption, and lower energy barrier for the generation of ammonia. This work may provide a facile way to prepare metal modified photocatalysts to achieve highly efficient nitrate reduction to ammonia.
Published: 14 August 2021
Energy Material Advances, Volume 2021, pp 1-8; https://doi.org/10.34133/2021/9795237
A novel electroactive organic molecule, viz., 1-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-1-(3-(trimethylammonio)propyl)-4,4-bipyridinium trichloride ((TPABPy)Cl3), is synthesized by decorating 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) with viologen, which is used as the positive electrolyte in neutral aqueous redox flow battery (ARFB). Extensive characterizations are performed to investigate the composition/structure and the electrochemical behavior, revealing the favorable effect of introducing the cationic viologen group on the electroactive TEMPO. Salient findings are as follows. First, the redox potential is elevated from +0.745 V for TEMPO to +0.967 V for decorated TEMPO, favoring its use as the positive electrolyte. Such an elevation originates from the electron-withdrawing effect of the viologen unit, as evidenced by the nuclear magnetic resonance and single crystal structure analysis. Second, linear sweep voltammetry reveals that the diffusion coefficient is , and the rate constant of the one-electron transfer process is . The two values are sufficiently high as to ensure low concentration and kinetics polarization losses during the battery operation. Third, the permeability through anion-exchange membrane is as low as . It is understandable as the positive-charged viologen unit prevents the molecule from permeating through the anion exchange membrane by the Donnan effect. Fourth, the ionic nature features a decent conductivity and thus eliminates the use of additional supporting electrolyte. Finally, a flow battery is operated with 1.50 M (TPABPy)Cl3 as the positive electrolyte, which affords a high energy density of 19.0 Wh L-1 and a stable cycling performance with capacity retention of 99.98% per cycle.
Published: 30 July 2021
Energy Material Advances, Volume 2021, pp 1-22; https://doi.org/10.34133/2021/9819521
The development of sodium-ion batteries (SIBs), which are promising alternatives to lithium-ion batteries (LIBs), offers new opportunities to address the depletion of Li and Co resources; however, their implementation is hindered by their relatively low capacities and moderate operation voltages and resulting low energy densities. To overcome these limitations, considerable attention has been focused on anionic redox reactions, which proceed at high voltages with extra capacity. This manuscript covers the origin and recent development of anionic redox electrode materials for SIBs, including state-of-the-art P2- and O3-type layered oxides. We sequentially analyze the anion activity–structure–performance relationship in electrode materials. Finally, we discuss remaining challenges and suggest new strategies for future research in anion-redox cathode materials for SIBs.
Published: 14 June 2021
Energy Material Advances, Volume 2021, pp 1-14; https://doi.org/10.34133/2021/9849202
The impact of cell voltage on the capacitance of practical electrochemical supercapacitors is a phenomenon observed experimentally, which lacks a solid theoretical explanation. Herein, we provide combined experimental and molecular dynamics investigation of the relation between voltage and capacitance. We have studied this relation in supercapacitor cells comprising of activated carbon material as the active electrode material, and neat ionic liquids (ILs), and a mixture of ILs as the electrolyte. It has been observed that the increase of accumulative charge impacts the conformation and packing of the cations in the anode, which determines its nonlinear behavior with increasing voltage. It has also been shown that for the mixture IL with two types of cations, the contribution of each type of cation to the overall capacitance is highly dependent on the different pore sizes in the system. The smaller tetramethylammonium (TMA+) shows tendency for more efficient adsorption in the mesopores, while 1-Ethyl-3-methylimidazolium (EMIM+) is found to be present almost exclusively in the micropores where TMA+ is present in small quantities. Such microscopic insights from computer simulations of the molecular phenomena affecting the overall performance in supercapacitors can help to design more efficient electrolytes and devices.
Published: 26 May 2021
Energy Material Advances, Volume 2021, pp 1-12; https://doi.org/10.34133/2021/9857563
The development of an energy storage system with abundant elements is a key challenge for a sustainable society, and the interest of Na intercalation chemistry is extending throughout the research community. Herein, the impact of Ti integration into NaMnO2 in a binary system of NaMnO2–() TiO2 () is systematically examined for rechargeable Na battery applications. Stoichiometric NaMnO2, which is classified as an in-plane distorted O3-type layered structure, delivers a large initial discharge capacity of approximately 200 mAh g-1, but insufficient capacity retention is observed, most probably associated with dissolution of Mn ions on electrochemical cycles. Ti-substituted samples show highly improved electrode performance as electrode materials. However, the appearance of a sodium-deficient phase, Na4Mn4Ti5O18 with a tunnel-type structure, is observed for Ti-rich phases. Among the samples in this binary system, Na0.8Mn0.8Ti0.2O2 (), which is a mixture of a partially Ti-substituted O3-type layered oxide (Na0.88Mn0.88Ti0.12O2) and tunnel-type Na4Mn4Ti5O18 as a minor phase elucidated by Rietveld analysis on both neutron and X-ray diffraction patterns, shows good electrode performance on the basis of energy density and cyclability. Both phases are electrochemically active as evidenced by in situ X-ray diffraction study, and the improvement of reversibility originates from the suppression of Mn dissolution on electrochemical cycles. From these results, the feasibility of Mn-based electrode materials for high-energy rechargeable Na batteries made from only abundant elements is discussed in detail.
Published: 22 May 2021
Energy Material Advances, Volume 2021, pp 1-10; https://doi.org/10.34133/2021/9870879
NASICON- (Na superionic conductor-) based solid-state electrolytes (SSEs) are believed to be attracting candidates for solid-state sodium batteries due to their high ionic conductivity and prospectively reliable stability. However, the poor interface compatibility and the formation of Na dendrites inhibit their practical application. Herein, we directly observed the propagation of Na dendrites through NASICON-based Na3.1Zr2Si2.1P0.9O12 SSE for the first time. Moreover, a fluorinated amorphous carbon (FAC) interfacial layer on the ceramic surface was simply developed by in situ carbonization of PVDF to improve the compatibility between Na metal and SSEs. Surprisingly, Na dendrites were effectively suppressed due to the formation of NaF in the interface when molten Na metal contacts with the FAC layer. Benefiting from the optimized interface, both the Na||Na symmetric cells and Na3V2(PO4)3||Na solid-state sodium batteries deliver remarkably electrochemical stability. These results offer benign reference to the maturation of NASICON-based solid-state sodium batteries.