• Energy Research

The sodiation/de-sodiation mechanism of metallic NbSe2 anodes is corrected to involve an initial irreversible conversion from NbSe2 to Na2Se/Nb composites and the subsequent reversible selenide conversion reaction.

One of the crucial methods for adapting distributed PV generation is the microgrid. However, solar resources, load characteristics, and the essential microgrid system components are all directly tied to the optimal planning scheme for microgrids. This article conducts a collaborative planning study of grid-connected PV-storage microgrids under electric vehicle integration in various scenarios using HOMER 1.8.9 software. To be more specific, in multiple scenarios, we built capacity optimization models for PV modules, energy storage, and converters in microgrids, with several scenarios each accounting for the cleanliness, economic performance, and overall performance of microgrids. For multiple scenarios, this paper used the net present value cost and levelized cost of electricity as indicators of microgrid economics, and carbon dioxide emissions and the fraction of renewable energy were used as indicators of microgrid cleanliness. The optimal capacity allocation for economy, cleanliness, and a combination of economy and cleanliness were separately derived. Finally, on a business park in Wuhan, China, we conducted thorough case studies to compare and debate the planning performance under various scenarios and to undertake sensitivity analyses on the cases. The sensitivity analyses were conducted for the optimal configuration of microgrids in terms of the EV charging scale, carbon dioxide emissions, PV module unit cost, and storage unit cost. The results of the simulation and optimization show that the optimization approach could determine the ideal configuration for balancing economy and cleanliness. As the EV charging demand increased, the energy storage capacity required in the microgrid gradually increased, while the carbon dioxide emission limit was negatively correlated with the energy storage capacity demand. The unit investment cost of PV module units had a greater impact on the optimal system configuration than the cost of batteries.

AbstractThe use of lithium–sulfur batteries under high sulfur loading and low electrolyte concentrations is severely restricted by the detrimental shuttling behavior of polysulfides and the sluggish kinetics in redox processes. Two‐dimensional (2D) few layered black phosphorus with fully exposed atoms and high sulfur affinity can be potential lithium–sulfur battery electrocatalysts, which, however, have limitations of restricted catalytic activity and poor electrochemical/chemical stability. To resolve these issues, we developed a multifunctional metal‐free catalyst by covalently bonding few layered black phosphorus nanosheets with nitrogen‐doped carbon‐coated multiwalled carbon nanotubes (denoted c‐FBP‐NC). The experimental characterizations and theoretical calculations show that the formed polarized P–N covalent bonds in c‐FBP‐NC can efficiently regulate electron transfer from NC to FBP and significantly promote the capture and catalysis of lithium polysulfides, thus alleviating the shuttle effect. Meanwhile, the robust 1D‐2D interwoven structure with large surface area and high porosity allows strong physical confinement and fast mass transfer. Impressively, with c‐FBP‐NC as the sulfur host, the battery shows a high areal capacity of 7.69 mAh cm−2 under high sulfur loading of 8.74 mg cm−2 and a low electrolyte/sulfur ratio of 5.7 μL mg−1. Moreover, the assembled pouch cell with sulfur loading of 4 mg cm−2 and an electrolyte/sulfur ratio of 3.5 μL mg−1 shows good rate capability and outstanding cyclability. This work proposes an interfacial and electronic structure engineering strategy for fast and durable sulfur electrochemistry, demonstrating great potential in lithium–sulfur batteries.

AbstractNovel cost‐effective fuel cells have become more attractive due to the demands for rare and expensive platinum‐group metal (PGM) catalysts for mitigating the sluggish kinetics of the oxygen reduction reaction (ORR). The high‐cost PGM catalyst in fuel cells can be replaced by Earth‐abundant transition‐metal‐based catalysts, that is, an Fe–N–C catalyst, which is considered one of the most promising alternatives. However, the performance of the Fe–N–C catalyst is hindered by the low catalytic activity and poor stability, which is caused by insufficient active sites and the lack of optimization of the triple‐phase interface for mass transportation. Herein, a novel Fe–N–C catalyst consisting of mono‐dispersed hierarchically mesoporous carbon sphere cores and single Fe atom‐dispersed functional shells are presented. The synergistic effect between highly dispersed Fe‐active sites and well‐organized porous structures yields the combination of high ORR activity and high mass transfer performance. The half‐wave potential of the catalyst in 0.1 M H2SO4 is 0.82 V versus reversible hydrogen electrode, and the peak power density is 812 mW·cm−2 in H2–O2 fuel cells. Furthermore, it shows superior methanol tolerance, which is almost immune to methanol poisoning and generates up to 162 mW·cm−2 power density in direct methanol fuel cells.

A separator, which can sustainably release Mg(NO3)2 into the electrolyte to ensure dendrite-free and long cycling of lithium metal batteries, is reported. This method is simple and efficient.

Abstract It is of great importance to improve the electrochemical performance of graphitic anode materials since they are dominantly used in practical lithium ion battery and still will be the main component as anode material in the future. By SEM, XPS, Micro-Raman and EDX analyses of graphite electrodes before and after discharge/charge cycle, it is found that capacity fading is strongly related to the dispersion of conductive. Homogeneous dispersion of conductive resulted in good cycle performance. However, for the poorly fabricated electrode, with heterogeneous dispersion of conductive, it gives rise to the formation of imperfect SEI film in the first cycle and subsequent continual decomposition of the electrolyte, leading to large amounts of nonconductive surface deposits consisting of Li2CO3 and LiF. As a result, its irreversible capacity is high and capacity retention is poor. Thus, homogeneous dispersion of conductive is necessary to obtain good performance for graphitic anode electrode. The formation of Li2CO3 and LiF during repeated cycling is attributed to the inhomogeneous distribution of the overpotential throughout the fabricated electrode.

The battery power state (SOP) is the basic indicator for the Battery management system (BMS) of the battery energy storage system (BESS) to formulate control strategies. Although there have been many studies on state estimation of lithium-ion batteries (LIBs), aging and temperature variation are seldom considered in peak power prediction during the whole life of the battery. To fill this gap, this paper aims to propose an adaptive peak power prediction method for power lithium-ion batteries considering temperature and aging is proposed. First, the Thevenin equivalent circuit model is used to jointly estimate the state of charge (SOC) and SOP of the lithium-ion power battery, and the variable forgetting factor recursive least squares (VFF-RLS) algorithm and extended Kalman filter (EKF) are utilized to identify the battery parameters online. Then, multiple constraint parameters including current, voltage, and SOC were derived, considering the dependence of the polarization resistance of the battery on the battery current. Finally, the verification experiment was carried out with LiFePO4 battery. The experimental results under FUDS operating conditions show that the maximum SOC estimation error is 1.94%. And the power prediction errors at 20%, 50%, and 70% SOC were 5.0%, 8.1% and 4.5%, respectively. Our further work will focus on the joint estimation of battery state to further improve the accuracy.

A novel PEO-based SPE with a synergistic effect of black phosphorus (BP) nanosheets and a cryogenic method, which can combine the advantages of the fast Li+ pathways of BP nanosheets and the low PEO crystallization of cryogenic method.