Large-scale Energy Storage Systems Research Articles

Structure-Controlled Prussian Blue Analog as a Cathode Material for Long-Life Seawater Batteries

Nowadays, as the use of fossil fuels is suppressed for achieving carbon neutrality, rechargeable battery is considered as a key factor to lead sustainable society. As far, the most developed and already commercialized batteries are lithium-ion batteries (LIBs). However, as the demand for LIBs is increasing, there are also several issues in the process of obtaining high-performance batteries. First, as the price of raw materials in LIB rises rapidly, a cost issue arises. In addition, as the fire accidents have occurred consistently due to overcharging or use of organic electrolyte, safety concerns are being raised. Finally, the environmental issues are emerging in the process of mining raw material and disposal of waste batteries. Therefore, a cheap, safe, and environmentally friendly battery system is needed as an alternative to LIBs.In this situation, a battery system called seawater battery (SWB) using seawater as a raw material is attracting attention. Since seawater is super-abundant resource, accounting 97% of the earth’s water, the material and manufacturing cost can be effectively reduced. Also, since it is operated in seawater, it is free from fire hazard and environmentally benign. In addition, as natural seawater can be used without additional treatment, energy can be reduced used for refining raw materials in LIBs.Likely to other battery systems, SWB consists of anode, cathode and separator. In anode part, Na-ions originated from NaCl in seawater are plated and stripped during cycling process. For facile metal plating, the anode part is filled with organic electrolyte, which also broaden the operation voltage window of overall cell. The ceramic solid electrolyte is used as separator, which is called Na-ion selective membrane, NASICON. The cathode part contains seawater which can act as an electrolyte or cathode as well (catholyte).The reaction mechanism mechanisms of cathode part can be sorted into three types―Na-intercalation, oxygen evolution/reduction reaction, and Cl-capturing. Herein, we have focused on the intercalation cathode to realize long-life and stable SWB, which is critical properties for large-scale energy storage systems. For intercalation cathode material, Prussian blue analog (PBA) was selected. PBA is an analog form of Prussian blue (PB). Since PB/PBAs have frame-like structures consist of metal nodes and cyanide ligands, the big alkali ions including Na-ions can be inserted and released through interstitial sites. By substituting the iron of PB to other transition metals, various form of PBAs can be synthesized. Among them, Ni-based PBA (Na2Ni[Fe(CN)6] when fully sodiated) was selected, because it is known as stable in seawater and undergoing small volume change during repeating ion (de)insertion, which is advantageous properties for stable SWB application.However, during synthetic process of PBAs, when metal ions and ligands meet rapidly, vacancies are easily created inside the structure. In these empty sites, the water molecules tend to coordinate, becoming crystal water. Since crystal water negatively affects the electrochemical performance of PB/PBAs, it should be controlled. Therefore, we have controlled the structure of Ni-based PBAs by chelation and improved the electrochemical performance of SWBs.By aid of chelating agent, well-structured Ni-based PBA was successfully synthesized. The defect ratio was effectively reduced from 40% to 6%, followed by less crystal water and more Na-ions inside the structure. When applied to SWB system, the cycle performance of chelated PBA was superior to untreated PBA, exhibiting capacity retention of 92.8% after 2000 cycles at 5 C. In conclusion, showing stable and reversible operation during 2000 cycles at the first time in SWB field, PBA-based SWB showed potential to be a promising next-generation battery. Figure 1

Interfacial Chemistry in Aqueous Lithium-Ion Batteries with Dilute Aqueous Electrolytes: A Case Study with V2O5

Aqueous lithium ion batteries (ALIBs) are promising candidates for large-scale energy storage systems, benefiting from the intrinsic safe and environmentally friendly properties of aqueous electrolytes. However, its practical application is impeded due to the narrow electrochemical stability windows (ESWs) of aqueous electrolytes. Despite that increasing electrolyte concentration can achieve a wide ESW with the protection of SEI layer, it brings numerous disadvantages induced by excessive salt as well. Therefore, understanding the SEI formation mechanism and further widening the ESWs of dilute aqueous electrolytes are critical for the breakthrough of next-generation ALIBs.Herein, the interphase chemistry of V2O5 electrode with dilute aqueous electrolyte was systematic investigated by conducting various Operando characterizations with LMO||V2O5 cell system. Dynamic SEI, which consists of Li2CO3, LiF and V2O4, was formed during charge and disappeared during the following discharge, which is strongly affected by electrolyte pH fluctuation. Moreover, its evolution process is reversible during cycling. There are several impacts affect the pH fluctuation during cycling. First, V2O5 dissolution, which turns electrolyte into acidic before cycling, and is aggravated by electrolyte concentration decrease. Second, proton/hydronium ion insertion, which takes place on electrode surface in dilute electrolyte, while it is suppressed by concentration increase due to reduced proton concentration. Third, the redox reaction of dissolved V2O5, which is controlled by both potential and electrolyte pH change according to the V-H2O poubaix diagram. Along with the anode potential decrease and the alkalinisation of electrolyte, V2O4 is formed on anode surface by the reduction of HV10O28 5- and V4O12 4- and this reduction process further produces hydroxide ion into electrolyte. Last, the carbon oxidation, which takes place on cathode side during charge and on anode side during the final discharge. Therefore, the acidification of electrolyte during cycling is detrimental to SEI stability in aqueous electrolytes. This systematic research work provides new perspectives to the understanding of the interphase chemistry evolution in aqueous Li-ion batteries using dilute electrolytes, which guides the building of effective SEI layer in aqueous Li-ion batteries and beyond. Figure 1

Synthesis and Interface Stabilization of Chalcogenide-Based Solid Electrolytes in Solid-State Sodium Batteries

Rechargeable sodium (Na) batteries that utilizing solid-state ion conductors have attracted intense attentions for large-scale energy storage systems due to the abundant resources of Na compounds and electrochemical voltage (2.70 V vs. 3.05V for Li). So far, the most popular inorganic Na-ion SEs include oxides, halides, and chalcogenides such as Na3PhCh4 (Ph=P, Sb; Ch=S, Se) etc. In specific, Na3SbCh4 (Ch=S, Se) chalcogenide conductors exhibit impressive ionic conductivity at room temperature due to vacancy-assisted three-dimensional (3D) ion transport channels. In this talk, we will introduce our works on the studies on in-situ synthesis of Na chalcogenide solid electrolytes (SEs) and several strategies for interface stabilization of such SEs towards Na anode. The in-situ synthesis studies of Na3SbCh4 (Ch=S, Se) reveal the structural evolutions during the solid-state reaction process.1 Besides, efficient interface stabilization strategies have been demonstrated to enable solid-state Na metal batteries that using Na as the anode, and metal sulfide (TiS2 or FeS2) as the cathode.2, 3 For instance, phase transition interlayer (PEG-PPG-PEG) has been successfully proved to prevent the side reactions between the Na3SbS4 SE and Na metal and contribute to the uniform Na deposition at interface to prevent dendrite formation and growth. The goal of our work is to develop novel chalcogenide Na conductors and promote their applications in solid-state Na batteries. Halacoglu, S.; Chertmanova, S.; Chen, Y.; Li, Y.; Rajapakse, M.; Sumanasekera, G.; Narayanan, B.; Wang, H., Visualization of Solid-State Synthesis for Chalcogenide Na Superionic Conductors by in-situ Neutron Diffraction. ChemSusChem 2021, 14 (23), 5161-5166.Li, Y.; Arnold, W.; Halacoglu, S.; Jasinski, J. B.; Druffel, T.; Wang, H., Phase-Transition Interlayer Enables High-Performance Solid-State Sodium Batteries with Sulfide Solid Electrolyte. Advanced Functional Materials 2021, 31 (28), 2101636.Li, Y.; Halacoglu, S.; Shreyas, V.; Arnold, W.; Guo, X.; Dou, Q.; Jasinski, J. B.; Narayanan, B.; Wang, H., Highly efficient interface stabilization for ambient-temperature quasi-solid-state sodium metal batteries. Chemical Engineering Journal 2022, 434, 134679.

Probing the Structure Evolution of Na-Cu-Mn-O Based Layered Oxide Cathode Materials in Sodium Ion Batteries

Sodium-ion batteries (SIBs) are considered as potential energy storage devices for large-scale energy storage system and smart power grids applications because of the low cost and abundant distribution of sodium in the earth's crust and ocean [1]. The development of highly efficient cathode materials for superior sodium storage is crucial for the development of SIBs. Among all the cathode materials, sodium transition-metal layered oxides, especially P2 and O3-typed layered oxides are of more interest due to their high theoretical capacity and easy synthesis [2,3]. From a structural point of view, P2 phase has an open pathway from one prismatic site to adjacent sites for more facile Na ion diffusion than O3 homologue. Therefore, the P2 phase shows not only better kinetic properties but improved cyclic stability thanks to its high structural stability.However, the pristine Na2/3MnO2 in P2 phase usually suffer from poor reversibility and dramatic capacity and voltage decay upon cycling, which origins form below issues: 1) the Na+/vacancy order-disorder transition, 2) the phase transition at high charge voltages due to MnO6 layers gliding 3) the Jahn-Teller distortion derived from Mn4+/Mn3+ redox couple, 4) the migration and dissolution of transition metals.[4] Up to now, a variety of improvement methods (doping and coating) have been utilized to stimulate the application of P2-type Na2/3MnO2 material. In particular, copper, as a low cost and environmental friendliness element, has also been introduced to synthesize multiple layered transition metal materials, like Na0.68Cu0.34Mn0.66O2, Na0.68Cu0.34Mn0.50Ti0.16O2, Na2/3Mn0.72Cu0.22Mg0.06O2 and so on. Furthermore, various redox behavior and structural evolution have also been explored. However, the process of structural transition during calcinating at different temperatures have been ignored, which leads to the unexpected neglect of some unique features of metastable phases in sintering materials.In our current work, Na2/3Cu1/3Mn2/3O2 in various phases have been successfully synthesized by sol-gel method and subsequently calcinated at different temperatures. XRD results show that Na2/3Cu1/3Mn2/3O2 calcinated at 600 °C (NCMO-600) is the triclinic phase, with the increasing calcination temperatures, the Na2/3Cu1/3Mn2/3O2 subsequently transfers to the hexagonal phase at 800 °C (NCMO-800). Subsequent electrochemical measurements show that NCMO-800 exhibit the better cycle stability and almost no voltage decay in the long term cycling, while the NCMO-600 sample exhibited rapid voltage attenuation at about 30 cycles. Besides, in situ XRD patterns and XANES spectra for both cathodes indicate slight different structural transition and electronic structure changes during charge and discharge. In a word, the NCMO-600 material exhibit the larger electron transfer at low current densities while the NCMO-800 material show the better cycle stability and rate performance.

Role of zinc hydroxysulfates in the thermodynamics and kinetics of mild-acid Zn-MnO2 batteries

Mild-acid Zn-MnO2 batteries have emerged as a promising alternative to replace Li-ion batteries in large-scale energy storage systems, primarily due to their high safety and low cost. While there have been significant improvements in the electrochemical performance of Zn-MnO2 batteries, the reaction mechanism of the MnO2 cathode is not fully comprehended. Despite the ongoing debate regarding the reaction mechanism of MnO2, it is noteworthy that the reversible formation and dissolution of zinc hydroxysulfates (ZHS) have been unequivocally observed during cycling. Nevertheless, the specific role of ZHS in the electrochemical reaction of MnO2 remains incompletely understood. Therefore, a comprehensive elucidation of the contribution of ZHS to the MnO2 reaction is still required. Herein, the role of ZHS in the electrochemical reaction of Mn2+ into MnO2 is investigated in terms of thermodynamics and kinetics. The voltage profiles associated with Mn2+ oxidation into MnO2 are compared under conditions of ZHS presence and absence. Operando pH analysis is also established to clarify the role of ZHS in the redox potential of the Mn2+/Mn4+ couple. In addition, a purposefully designed electrochemical experiment is performed to elucidate that ZHS significantly contributes to the oxidation kinetics of Mn2+ into MnO2 during charge. Various hydroxysulfate compounds are also examined to demonstrate a correlation between OH− derived from ZHS and the oxidation kinetics of Mn2+ during charge. These findings provide evidence that the electrochemical performance of Zn-MnO2 batteries is remarkably influenced by the dissolution kinetics of ZHS during charge and the precipitation sites of ZHS during discharge.

Improved marketing strategy of a hybrid renewable plant integrated with gravitational energy storage: Techno-economic analysis and multi-objective optimization

The intermittent nature of renewable energy sources, which could negatively impact the stability of the electricity grid and the economic viability of the technologies, has intensified concerns about their extensive contributions to the national energy systems' electricity supply. Energy storage systems have become increasingly relevant as a means for securing grids' stability with high shares of renewables. The purpose of this study is to investigate the potential of utility-scale gravitational energy storage as a ‘bidding strategy facilitator in the day-ahead market’ for renewable energy plants. With this ultimate goal, the size of the storage unit is not necessarily very large compared to the peak production capacity of the plant. This is in favor of the cost-effectiveness of the power plant due to today's unsupportive electricity pricing and market regulations for justifying large-scale energy storage systems. The gravitational energy storage system is assumed to accompany a PV farm in Denmark, just as a sample case study. The system is designed, sized, and planned for the optimal marketing strategy of the PV plant using rigorous techno-economic modeling and optimization techniques. According to preliminary findings, a 100 MWP PV plant with 5 MWh storage capacity can be built with a capital expenditure of $126.96 million, at a discounted payback period of 10.6 years, and reduced annual penalties of over 94.5 %.

In situ Construction of Multifunctional Surface Coatings on Zinc Metal for Advanced Aqueous Zinc–Iodine Batteries

AbstractAqueous zinc–iodine batteries (Zn–I2) demonstrate great promise in large scale energy storage systems. However, their practical application faces significant challenges including dendrite formation, corrosion caused by polyiodine ions, and other side reactions at the zinc anode side. Herein, a facile and efficient pretreatment method for zinc anodes through the substitution reaction of Zn and SnF2 to create a dense and durable multifunctional surface layer (MSL). The MSL comprise tin (Sn) and ZnF2 phases on the zinc metal, in which Sn possesses good zinc affinity and a high hydrogen evolution overpotential, while ZnF2 provides pathways for radial ion transport. Importantly, both have a low binding energy with polyiodine ions, preventing the failure of the interface layer. Therefore, this interface layer can effectively mitigate zinc metal electrode dendrite formation, corrosion from polyiodine ions, and other side reactions induced by water, simultaneously. As a result, the Zn–I2 batteries performance is greatly improved and exhibited a stable cycling to 20 000 times with 80% capacity retention at a current density of 2 A g−1. Even the I2 loading is increased to 8 mg cm−2, it can still cycle stably for 5000 cycles with a capacity retention of 94%.

Recent Advances on F-Doped Layered Transition Metal Oxides for Sodium Ion Batteries.

With the development of social economy, using lithium-ion batteries in energy storage in industries such as large-scale electrochemical energy storage systems will cause lithium resources to no longer meet demand. As such, sodium ion batteries have become one of the effective alternatives to LIBs. Many attempts have been carried out by researchers to achieve this, among which F-doping is widely used to enhance the electrochemical performance of SIBs. In this paper, we reviewed several types of transition metal oxide cathode materials, and found their electrochemical properties were significantly improved by F-doping. Moreover, the modification mechanism of F-doping has also been summed up. Therefore, the application and commercialization of SIBs in the future is summarized in the ending of the review.

Na3(VO)2(PO4)2F coated carbon nanotubes: A cathode material with high-specific capacity for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are one of the candidate technologies for large-scale energy storage systems due to their environmental friendliness, safety and resourcefulness. However, designing and synthesizing high-performance cathode materials with practical application value is currently a great challenge. Herein, we synthesize a carbon-nanotube-coated Na3(VO)2(PO4)2F (Na3(VO)2(PO4)2F@CNT) cathode material for AZIBs, which has a continuous and interconnected ion transport channel structure. A Zn2+/H+ co-intercalation mechanism is revealed by ex-situ X-ray diffraction (XRD) and ex-situ X-ray photoelectron spectroscopy (XPS) characterizations. The Na3(VO)2(PO4)2F@CNT cathode material exhibits a high specific capacity of 143 mAh‧g Wan et al. (2019). at 0.2 C in the electrolyte of 3 M Zn(OTf)2 aqueous solution. In addition, Na3(VO)2(PO4)2F@CNT shows a good low-temperature electrochemical performance in the electrolyte of 2 M Zn(OTf)2 deionized water/ethylene glycol (DIW/EG) mixed solution with a different ion storage mechanism. This study provides a new polyanionic cathode material for AZIBs and an idea to modulate the electrolyte polarity to enhance the zinc storage capacity of the cathode material.

Anodic protection strategy for zinc ion batteries

With the advent of the national dual-carbon strategy, there is a burgeoning demand for large-scale energy storage systems within the national grid. Nevertheless, lithium-ion batteries have been constrained in large-scale energy storage systems due to their limitations, encompassing scarce raw materials, diminished safety profiles, and environmental concerns. In recent years, zinc-ion batteries have emerged as the most promising option for large-scale energy storage systems, owing to their cost-effectiveness, heightened safety attributes, substantial theoretical capacity, and environmental compatibility. Nonetheless, zinc anodes continue to grapple with significant challenges, including dendrite growth, corrosion passivation, and the hydrogen-evolution reaction (HER), which impede the progressive advancement of zinc-ion battery anodes. This paper provides a comprehensive overview of the principal failure modes and mechanisms inherent to zinc anodes derived from an in-depth analysis of their associated issues. Furthermore, it systematically reviews the primary strategies for modifying zinc-negative electrodes, encompassing diaphragm modifications, electrolyte additives, and anode modifications. This endeavor aims to offer insights and support for enhancing zinc-ion battery anodes.

The Distance Between Phosphate-Based Polyanionic Compounds and Their Practical Application For Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are a viable alternative to meet the requirements of future large-scale energy storage systems due to the uniform distribution and abundant sodium resources. Among the various cathode materials for SIBs, phosphate-based polyanionic compounds exhibit excellent sodium-storage properties, such as high operation voltage, remarkable structural stability, and superior safety. However, their undesirable electronic conductivities and specific capacities limit their application in large-scale energy storage systems. Herein, the development history and recent progress of phosphate-based polyanionic cathodes are first overviewed. Subsequently, the effective modification strategies of phosphate-based polyanionic cathodes are summarized toward high-performance SIBs, including surface coating, morphological control, ion doping, and electrolyte optimization. Besides, the electrochemical performance, cost, and industrialization analysis of phosphate-based polyanionic cathodes for SIBs are discussed for accelerating commercialization development. Finally, the future directions of phosphate-based polyanionic cathodes are comprehensively concluded. It is believed that this review can provide instructive insight into developing practical phosphate-based polyanionic cathodes for SIBs.

Na5YSi4O12 fast ion conductor protection layer enabled dendrite-free Zn metal anode

Aqueous zinc-ion batteries (AZIBs) are promising for future large-scale energy storage systems, however, suffer from inferior cycling life due to the dendrites growth and side reaction on Zn metal anode. Herein, a fast ion conductor Na5YSi4O12 (NYSO) was synthesized and fabricated as a protection layer of the Zn metal anode. By adjusting the thickness, an optimized NYSO coating of 20.3 µm was obtained and the corresponding symmetry cell demonstrates an extended life span of 1896 h at the current density of 0.5 mA cm−2. In addition, a favorable rate performance of the NYSO@Zn anode at a high current density of 10 mA cm−2 was achieved. Benefiting from the NYSO coating, uniform diffusion and deposition of Zn2+ on the Zn anode could be realized, leading to the elimination of Zn dendrites and side reactions. Therefore, the aqueous NYSO@Zn|CNT@MnO2 full cell shows superior capacity and cycling stability to that of the bare Zn full cell.

Interlayer Engineering of VS2 Nanosheets via In Situ Aniline Intercalative Polymerization toward Long-Cycling Magnesium-Ion Batteries.

Rechargeable magnesium batteries (RMBs) show great potential in large-scale energy storage systems, due to Mg2+ with high polarity leading to strong interactions within the cathode lattice, and the limited discovery of functional cathode materials with rapid kinetics of Mg2+ diffusion and desirable cyclability retards their development. Herein, we innovatively report the confined synthesis of VS2/polyaniline (VS2/PANI) hybrid nanosheets. The VS2/PANI hybrids with expanded interlayer spacing are successfully prepared through the exfoliation of VS2 and in situ polymerization between VS2 nanosheets and aniline. The intercalated PANI increases the interlayer spacing of VS2 from 0.57 to 0.95 nm and improves its electronic conductivity, leading to rapid Mg-ion diffusivity of 10-10-10-12 cm2 s-1. Besides, the PANI sandwiched between layers of VS2 is conducive to maintaining the structural integrity of electrode materials. Benefiting from the above advantages, the VS2/PANI-1 hybrids present remarkable performance for Mg2+ storage, showing high reversible discharge capacity (245 mA h g-1 at 100 mA g-1) and impressive long lifespan (91 mA h g-1 after 2000 cycles at 500 mA g-1). This work provides new perspectives for designing high-performance cathode materials based on layered materials for RMBs.

Enhanced control strategy and energy management for a photovoltaic system with hybrid energy storage based on self-adaptive bonobo optimization

Large-scale energy storage systems (ESSs) that can react quickly to energy fluctuations and store excess energy are required to increase the reliability of electricity grids that rely heavily on renewable energy sources (RESs). Hybrid systems, which combine different energy storage technologies such as batteries and supercapacitors, are becoming increasingly popular because no single technology can satisfy all requirements. In this study, a supercapacitor is used to stabilize quickly shifting bursts of power, while a battery is used to stabilize gradually fluctuating power flow. This paper proposes a robust controller for managing the direct current (DC) bus voltage to optimize the performance of ESS. The proposed controller combines a fractional-order proportional integral (FOPI) with a classical PI controller for the first time in the DC microgrid area. The hybrid (FOPI-PI) controller achieves an outstanding and superior performance in all transient and dynamic response specifications compared to other traditional controllers. The parameters of the suggested controller are incorporated with the self-adaptive bonobo optimizer (SaBO) to determine the optimal values. Furthermore, various optimization techniques are applied to the model and the SaBO’s output outperforms other techniques by minimizing the best objective function. In addition, the current study has utilized a novel power management strategy that includes two closed current loops for both batteries and supercapacitors. By using this method, batteries’ lifespans may be increased while still retaining optimal system performance. The suggested controller is implemented in MATLAB/Simulink 2022b, and the outcomes are reported for several case studies. The findings demonstrate that the control technique remarkably improves the transient response, such as transient duration, overshoot/undershoot, and the settling time. The proposed controller (FOPI-PI) with the SaBO optimizer is effective in maintaining the DC bus voltage under load and solar system variation.

Inorganic All-Solid-State Sodium Batteries: Electrolyte Designing and Interface Engineering.

Inorganic all-solid-state sodium batteries (IASSSBs) are emerged as promising candidates to replace commercial lithium-ion batteries in large-scale energy storage systems due to their potential advantages, such as abundant raw materials, robust safety, low price, high-energy density, favorable reliability and stability. Inorganic sodium solid electrolytes (ISSEs) are an indispensable component of IASSSBs, gaining significant attention. Herein, this review begins by discussing the fundamentals of ISSEs, including their ionic conductivity, mechanical property, chemical and electrochemical stabilities. It then presents the crystal structures of advanced ISSEs (e.g., β/β''-alumina, NASICON, sulfides, complex hydride and halide electrolytes) and the related issues, along with corresponding modification strategies. The review also outlines effective approaches for forming intimate interfaces between ISSEs and working electrodes. Finally, current challenges and critical perspectives for the potential developments and possible directions to improve interfacial contacts for future practical applications of ISSEs are highlighted. This comprehensive review aims to advance the understanding and development of next-generation rechargeable IASSSBs.

Establishing Ultralow Self-Discharge Zn-I2 Battery by Optimizing ZnSO4 Electrolyte Concentration.

As one of promising candidates for large-scale energy-storage systems, Zn-I2 aqueous battery exhibits multifaceted advantages including low cost, high energy/powder density, and intrinsic operational safety, but also suffers from fast self-discharge and short cycle/shelf lifespan associating with I3 - shuttle, Zn dendrite growth, and corrosion. In this paper, the battery's self-discharge rate is successfully suppressed down to an unprecedent level of 17.1% after an ultralong shelf-time of 1000h (i.e., 82.9% capacity retention after 41 days open-circuit storage), by means of manipulating solvation structures of traditional ZnSO4 electrolyte via simply adjusting electrolyte concentration. Better yet, the optimized 2.7 mZnSO4 electrolyte further prolongs the cycle lifespan of the battery up to >10000 and 43000 cycles at current density of 1 and 5Ag-1, respectively, thanks to the synthetic benefits from reduced free water content, modified solvation structure and lowered I2 dissolution in the electrolyte. With both long lifespan and ultralow self-discharge, this reliable and affordable Zn-I2 battery may provide a feasible alternative to the centuries-old lead-acid battery.

Research on the loss characteristics of high-voltage cascaded energy storage systems based on IGCTs

High-voltage cascaded energy storage systems have become a major technical direction for the development of large-scale energy storage systems due to the advantages of large unit capacity, high overall efficiency, satisfactory economy, reliable safety, and easy access to grid dispatching. The loss characteristics analysis is the design basis of the water-cooling system of a high-voltage cascaded energy storage system, and its accurate calculation can determine the system’s safe and reliable operation of the system. This paper first introduces the four-quadrant operation principles of a cascaded H-bridge energy storage system, and analyzes the calculation method of the loss of the Integrated Gate-Commutated Thyristor based power module; On this basis, it studies the loss characteristics of the cascaded energy storage system and analyzes the influence of different modulation strategies and third harmonic injection on the loss characteristics of the energy storage system; Finally, this paper has completed the loss test for the engineering prototype module and compared the test results with theoretical calculation results to verify the accuracy of the loss calculation method of the high-voltage cascaded energy storage system.

Enhancement of lithiation on a graphane monolayer through extended H vacancy pathways: An ab initio study

The increasing interest for the need of large-scale energy-storage systems have led to the development of high-performance energy-storage devices such as lithium-ion batteries (LIBs). Two dimensional (2D) materials are promising candidates for fulfilling this requirement due to their peculiar physical properties. However, it is important to understand the role of multiple Li adatoms on the 2D materials, more especially when defects are involved. In this study, first-principles density functional theory (DFT) calculations were performed to study Li on the H vacancies (VH) following the line and zigzag pathways on a graphane sheet. The results of Li atom on a single H vacancy (VH1) reveal an immediate enhanced interaction based on the improved binding energies, high amount of charge transfer and significantly shortened Li height, as compared to those of pristine graphane counterpart. An increase in the number of H vacancies along the line pathway from one (VH1(L)) to five (VH5(L)) further improves the binding energies ranging from 1.82 eV to 2.91 eV. Considering a simultaneous increase of Li atoms and H vacancies following a line pathway (VH1(L) to five VH5(L)), the binding energies tend to reduce in order. However, it is still higher than the minimum Li standard bulk cohesive energy of 1.63 eV. We show that there is a possibility of uniform dispersion of Li atoms with less clustering on a graphane sheet. A transition from insulator to metallic character was observed from VH1(L) to VH5(L), due to an induced new Li states at the vicinity of the Fermi level, suggesting an enhancement of electronic conductivity in the graphane sheet. At five Li atom VH5(L) configuration along the line pathway, we obtained a relatively high storage capacity of 207.49 mAh/g with its corresponding lithiation potential of 1.48 V, comparable to those of well known two dimensional anode materials.

Tuning electrolyte solvation structure with Co-solvent engineering to enable highly reversible and stable Zn-graphite dual-ion batteries

Graphite-based dual-ion batteries (GDIBs) have attracted ever-growing attentions due to its non-transition metal configuration and high working potential. However, the safety concerns associated with the use of organic electrolyte make it unpractical for large-scale energy storage system. Moreover, the anodic limit of aqueous electrolytes, even the improved anodic limit derived from highly concentrated aqueous electrolytes, is not sufficient to support high graphite intercalation voltage. Herein, a co-solvent-induced hybrid aqueous/non-aqueous electrolyte has been proposed to break this bottleneck through regulating the solvation structures around anions. A series of hybrid electrolytes are prepared by controlling dimethyl carbonate (DMC) ratio and the relation between the solvation structures and anion intercalation chemistry is explored, indicating that the mutual interaction between solvent molecules and anions determines the anion intercalation behaviour. The optimized DMC-dominated solvation structures with a mass ratio of DMC to water of 1.2:1 significantly expand the anodic limit of electrolyte up to 2.54 V (vs. Zn/Zn2+). The as-designed Zn-Graphite batteries exhibit an excellent cyclic stability and reversibility (99 % capacity retention after 200 cycles at 200 mA g−1, nearly 98 % Coulombic efficiency). This work provides guidance to achieve the balance between security capability and electrochemical performances through controllable solvation structures.

Key Issues and Strategies of Aqueous Zinc-Ion Batteries

With the rapid growth of the world population and the further industrialization of modern society, the demand for energy continues to rise sharply. Hence, the development of alternative, renewable, and clean energy sources is urgently needed to address the impending energy crisis. Rechargeable aqueous zinc-ion batteries are drawing increased attention and are regarded as the most promising candidates for large-scale energy storage systems. However, some challenges exist for both the anode and cathode, severely restricting the practical application of ZIBs. In this review, we focus on the issues related to the anode (such as dendrites growth, hydrogen evolution, and surface passivation). We discuss the causes of these challenges and summarize the strategies (such as surface engineering, electrolyte modification, and 3D structural skeleton and alloying) to overcome them. Finally, we discuss future opportunities and challenges of ZIBs regarding the Zn anode.