Due to the large abundance, low redox potential, and multivalent properties of calcium (Ca), Ca‐ion batteries (CIBs) show promising prospects for energy storage applications. However, current ...research on CIBs faces the challenges of unsatisfactory cycling stability and capacity, mainly restricted by the lack of suitable electrolytes and electrode materials. Herein, we firstly developed a 3.5 m concentrated electrolyte with a calcium bis(fluorosulfonyl)imide (Ca(FSI)2) salt dissolved in carbonate solvents. This electrolyte significantly improved the intercalation capacity for anions in the graphite cathode and contributed to the reversible insertion of Ca2+ in the organic anode. By combining this concentrated electrolyte with the low‐cost and environmentally friendly graphite cathode and organic anode, the assembled Ca‐based dual‐ion battery (Ca‐DIB) exhibits 75.4 mAh g−1 specific discharge capacity at 100 mA g−1 and 84.7 % capacity retention over 350 cycles, among the best results known for CIBs.
Ca‐ion battery: Ascribed to the improved anion intercalation performance in the graphite cathode and reversible Ca2+ insertion in the organic anode, by combining a 3.5 m concentrated Ca‐ion electrolyte with the low‐cost and environmentally friendly graphite cathode and organic anode, the proof‐of‐concept Ca‐based dual‐ion battery exhibits 75.4 mAh g−1 specific discharge capacity and 84.7 % capacity retention over 350 cycles, among the best results for Ca‐ion batteries.
K‐based dual‐carbon batteries (K‐DCBs) integrate the advantages, including high‐voltage, low‐cost, and environmentally friendliness of dual‐ion batteries (DIBs), and large abundance of K, thus ...attracting much attention in large‐scale energy storage application. However, most currently used electrolytes based on KPF6 and carbonate solvents commonly suffer from poor oxidation potential (<4.4 V vs Li/Li+) and low electrolyte concentration (<1 m), which limit the cycling stability and energy density of K‐DCBs. Herein, after a matching behavior study of various electrolyte solvents with potassium salts, a concentrated electrolyte is developed by successfully dissolving 5.2 m potassium bis(fluorosulfonyl)imide into tetramethylene sulfone. This high‐concentration electrolyte exhibits advantages: 1) high oxidation potential that enhances intercalation reversibility and capacity of FSI− anions; 2) improved K+ storage at graphite anode; 3) dramatically increased energy density of K‐DCB. A proof‐of‐concept K‐ion dual‐graphite battery based on this high‐concentration electrolyte displays a discharge capacity of 83.4 mAh g−1 at 100 mA g−1, and negligible capacity fading after 300 cycles. Furthermore, considering both the electrolyte and electrode materials, energy density of such K‐DCB reaches ≈130 Wh kg−1, the best performance of K‐DCBs among previously reported research.
A 5.2 m highly concentrated potassium bis(fluorosulfonyl)imide/tetramethylene sulfone electrolyte is developed for K‐based dual‐graphite batteries. Ascribed to the high oxidation potential (≈6.0 V) that allows the intercalation reversibility of FSI− anions at the graphite cathode and improved K+ storage at graphite anode, the K‐based dual‐graphite battery displays significantly enhanced capacity and energy density based on this concentrated electrolyte.
As a novel cost‐effective, high operating voltage, and environmentally friendly energy storage device, the dual‐ion battery (DIB) has attracted much attention recently. Despite a similar energy ...storage mechanism at the anode side to the traditional “rocking‐chair” batteries like lithium‐ion batteries (LIBs), DIBs commonly featured intercalation of anions at the cathode materials. In addition, the electrolyte in DIBs not only acts as the ion transport medium, it also serves as the active material. As a result, the electrolyte not only determines the Coulombic efficiency and cycling life but also plays a crucial role in capacity and energy density of DIBs. Moreover, although they have similar electrochemical reactions at the anode side to LIBs, to match the fast intercalation kinetics of anions at the cathode side and take into account the quite different electrolyte systems for DIBs, rational design and optimization of anode materials still need to be considered. This review first describes the research development history and working mechanism of DIBs; after that, the research progress in electrolytes, cathode materials, and anode materials for DIBs are summarized, respectively. Finally, the prospects and future research directions of DIBs are also presented based on current understandings.
Both cations and anions are involved during the operation process of dual‐ion batteries (DIBs). In this review, apart from the research progress on cathode and anode materials, the importance of the electrolyte on the electrochemical performance of electrode materials and DIBs are emphasized, and various strategies and efforts toward high‐performance electrolyte systems are also discussed.
Dual‐ion batteries (DIBs) have attracted much attention owing to their low cost, high voltage, and environmental friendliness. As the source of active ions during the charging/discharging process, ...the electrolyte plays a critical role in the performance of DIBs, including capacity, energy density, and cycling life. However, most used electrolyte systems based on the LiPF6 salt demonstrate unsatisfactory performance in DIBs. We have successfully developed a 7.5 mol kg−1 lithium bis(fluorosulfonyl)imide (LiFSI) in a carbonate electrolyte system. Compared with diluted electrolytes, this highly concentrated electrolyte exhibits several advantages: 1) enhanced intercalation capacity and cycling stability of the graphite cathode, 2) optimized structural stability of the Al anode, and 3) significantly increased battery energy density. A proof‐of‐concept DIB based on this concentrated electrolyte exhibits a discharge capacity of 94.0 mAh g−1 at 200 mA g−1 and 96.8 % capacity retention after 500 cycles. By counting both the electrode materials and electrolyte, the energy density of this DIB reaches up to ≈180 Wh kg−1, which is among the best performances of DIBs reported to date.
A 7.5 mol kg−1 LiFSI highly concentrated electrolyte was developed for a dual‐ion battery (DIB). A proof‐of‐concept DIB based on this concentrated electrolyte exhibits a discharge capacity of 94.0 mAh g−1 at 200 mA g−1, 96.8 % capacity retention after 500 cycles, and an energy density up to approximately 180 Wh kg−1 based on the electrode materials and electrolyte, which is among the best performances of previously reported DIBs.
Potassium‐based energy storage devices (PESDs) are promising candidates for large‐scale energy storage applications owing to potassiums abundant in nature, the low standard redox potential (−2.93 V ...for K/K+ vs the standard hydrogen electrode) of potassium (K), and high ionic conductivity of K‐ion based electrolytes. However, lack of proper cathode and anode materials hinder practical applications of PESDs. In this work, carbon nanosheets doped with an ultrahigh content of nitrogen (22.7 at%) are successfully synthesized as an anode material for a K‐ion battery, which delivers a high capacity of 410 mAh g−1 at a current density of 500 mA g−1, which is the best result among the carbon based anodes for PESDs. Moreover, the battery exhibits an excellent cycling performance with a capacity retention of 70% after 3000 cycles at a high current density of 5 A g−1. In situ Raman, galvanostatic intermittent titration, and density functional theory calculations reveal that the ultrahigh N‐doped carbon nanosheet (UNCN) simultaneously combines the diffusion and pseudocapacitive mechanisms together, which remarkably improves its electrochemical performances in K‐ion storage. These results demonstrate the good potential of UNCNs as a high‐performance anode for PESDs.
Carbon nanosheets doped with an ultrahigh content of nitrogen (22.7 at%) are designed and successfully synthesized as the anode materials for K‐ion batteries. With the combination of diffusion and pseudocapacitive energy storage mechanisms, the K‐ion storage capability of this ultrahigh N‐doped carbon nanosheets is remarkably improved.
We developed a method to engineer well-distributed dicobalt phosphide (Co2P) nanoparticles encapsulated in N,P-doped graphene (Co2P@NPG) as electrocatalysts for hydrogen evolution reaction (HER). We ...fabricated such nanostructure by the absorption of initiator and functional monomers, including acrylamide and phytic acid on graphene oxides, followed by UV-initiated polymerization, then by adsorption of cobalt ions and finally calcination to form N,P-doped graphene structures. Our experimental results show significantly enhanced performance for such engineered nanostructures due to the synergistic effect from nanoparticles encapsulation and nitrogen and phosphorus doping on graphene structures. The obtained Co2P@NPG modified cathode exhibits small overpotentials of only −45 mV at 1 mA cm–2, respectively, with a low Tafel slope of 58 mV dec–1 and high exchange current density of 0.21 mA cm–2 in 0.5 M H2SO4. In addition, encapsulation by N,P-doped graphene effectively prevent nanoparticle from corrosion, exhibiting nearly unfading catalytic performance after 30 h testing. This versatile method also opens a door for unprecedented design and fabrication of novel low-cost metal phosphide electrocatalysts encapsulated by graphene.
The atomic thin, vertically-stacked 2H-MoTe2/MoS2 heterostructures are successfully synthesized using the single step chemical vapor deposition (CVD) method and a magnet-assisted secondary precursor ...delivery tool. The second material (MoTe2) was grown in a well-controlled, unique and epitaxial 2H-stacking mode atop the first material (MoS2), starting from the edges. This led to the construction of a vertical p-n junction with a broadband photoresponse from the ultraviolet (UV, 200 nm) to the near-infrared (IR, 1100 nm) regions. The high crystallinity of MoTe2/MoS2 heterostructures with a modulation of sulfur and tellurium distribution is corroborated by multiple characterization methods, including Raman spectroscopy, photoluminescence (PL) spectroscopy and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Furthermore, the photoelectrical measurements exhibit a tremendous photoresponsivity with an external quantum efficiency (EQE) as high as 4.71 A/W and 532% at 1100 nm, while as 4.67 A/W and 1935% at 300 nm, one to two orders of magnitude higher than other exfoliated MoTe2 heterostructure devices have been reported so far. This synthetic method is a controllable stacking mode confined synthesis approach for 2D heterostructures, and paves the way for the fabrication of high-performance functional telluride-based broadband photodetectors.
Highly crystallized bilayer MoTe2/MoS2 p-n heterojunctions with advanced photoresponsivity are for the first time synthesized by a single-run chemical vapor deposition method. The photodetectors exhibit a tremendous photoresponsivity as 4.71 A/W and an external quantum efficiency (EQE) as 532% at 1100 nm, while 4.67 A/W and 1935% at 300 nm, which are one to two orders of magnitude higher than other transition-metal dichalcogenides (TMDs) heterostructures reported so far. Display omitted
Atomic registry has a strong impact on the electronic structure and properties of graphene due to its localized strain and localized charge distribution. However, direct experimental evidence of a ...correlation between its physical structure and chemical reactivity is still lacking. Here, we report that the electron transfer chemistry is significantly modified in twisted bilayer graphene (tBLG) by investigating the results of chemical functionalization with diazonium salts. The relative reaction rate for grafting diazonium salts on tBLG is much faster than that on AB-stacking graphene. Gerischer–Marcus electron transfer theory analysis, along with electronic structure calculations, indicates that the different reactivities mainly result from distinct variations in the density-of-states distribution in the gap region. Our results suggest a venue to separate and sort different stacking modes of bilayer graphene for various promising applications in nanoelectronics.
The 2D geometry nature and low dielectric constant in transition-metal dichalcogenides lead to easily formed strongly bound excitons and trions. Here, we studied the photoluminescence of van der ...Waals heterostructures of monolayer MoS2 and graphene at room temperature and observed two photoluminescence peaks that are associated with trion emission. Further study of different heterostructure configurations confirms that these two peaks are intrinsic to MoS2 and originate from a bound state and Fermi level, respectively, of which both accept recoiled electrons from trion recombination. We demonstrate that the recoil effect allows us to electrically control the photon energy of trion emission by adjusting the gate voltage. In addition, significant thermal smearing at room temperature results in capture of recoil electrons by bound states, creating photoemission peak at low doping level whose photon energy is less sensitive to gate voltage tuning. This discovery reveals an unexpected role of bound states for photoemission, where binding of recoil electrons becomes important.
