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Potassium-based dual ion batteries have emerged as promising alternatives to the prevailing lithium-ion batteries due to the advantages in cost and sustainability. Single-anion intercalation into graphite takes place on the cathode side, but it usually delivers a low capacity with poor Coulombic efficiency in potassium-based systems. We demonstrate the performance could be significantly boosted through synergistic dual-anion intercalation of FSI− and PF 6 −. The presence of PF 6 − helps the formation of an effective cathode electrolyte interface to allow high anionic stability up to 5.5 V, while FSI− intercalation brings about superior rate capability and long-term cyclic stability. Concurrent intercalation of FSI− and PF 6 − is tracked by in-situ Raman spectroscopy and ex-situ XRD. It reveals the formation of stage I graphite intercalation compounds (GICs) upon charging, leading to a reversible capacity of over 100 mAh g−1 with an average potential of 4.65 V (vs. K+/K). Furthermore, the graphite-potassium cell delivers an exceptional capacity of 94 mAh g−1 at 0.3 A g−1 and shows capacity retention of 96% after 250 cycles. The strategy provides a novel avenue toward stable dual-ion battery via intercalation chemistry regulation. Synergistic intercalation of PF 6 − and FSI− enables high-capacity and stable graphite cathode for potassium-based dual ion battery. [Display omitted] • Synergistic intercalation of PF 6 - and FSI- enables stable graphite cathode for potassium-based dual ion battery. • PF 6 - facilitates the formation of F-rich CEI against oxidation and FSI- promotes the kinetics at high rates. • Formation of stage I graphite intercalation compounds at 5.5 V (vs. K+/K) is revealed via in-situ Raman and ex-situ XRD. • The graphite-K cell delivers a high capacity of 94 mAh g-1 at 0.3 A g-1 and proves 96% retention after 250 cycles. [ABSTRACT FROM AUTHOR]

Lithium-oxygen batteries (LOBs) have attracted much attention because of their extraordinarily high specific energies. They possess critical weaknesses, however, such as poor cyclic stability, low energy efficiencies, as well as serious safety issues arising from the formation of lithium dendrites. Here, we report the synthesis of a long-life Li ion O 2 battery (LIOB) consisting of an anode made from pre-lithiated aluminum (Al) foil and a Li 2 O 2 -preloaded oxygen cathode, which are both commercially available. The assembled LIOB delivers an excellent specific reversible capacity of 1000 mAh g −1 carbon for over 100 cycles at 100 mA g −1 and a maximum specific energy density of 1178 Wh kg −1 . The pre-lithiated Al foil functions as both the anode and current collector, and the stable solid electrolyte interphase layer formed on anode during pre-lithiation greatly improves the cyclic stability. In view of abundance and availability of the cathode and anode materials, the assembly strategy developed here can offer a promising route to large-scale fabrication of LIOBs for real-world applications. [ABSTRACT FROM AUTHOR]

Abstract: Graphene decorated with manganese dioxide nanoparticles are prepared by electrostatic adsorption. The manganese dioxide is synthesized by a microemulsion route using the cationic surfactant hexadecyltrimethyl ammonium bromide, which dispersed in water is converted to be positively charged. The surface charge of graphene in water is negative, allowing two forms of manganese dioxide-decorated graphene to be synthesized by electrostatic adsorption: (a) free in situ synthesis and (b) layer-by-layer self-assembly. By electrochemical analysis, the specific capacitances of two materials are found to be about 40% and 250% larger than that of manganese dioxide. The improvement is because of the tighter contact between graphene and manganese dioxide, and the higher conductive and capacitive characteristics of graphene. [Copyright &y& Elsevier]

Abstract: The co-existence of two mechanisms, the surface chemisorption mechanism (SCM) and the tunnel storage mechanism (TSM), for the charge storage of MnO2 is investigated. Sample α-MnO2 whose tunnels (2×2) are almost vacant is synthesized by chemical co-precipitation technique. To verify whether the charge storage of as-prepared α-MnO2 involves the charges based on the SCM besides the TSM, Ba2+ and K+ are intercalated into the tunnels of α-MnO2 by refluxing and samples Ba-MnO2 and K-MnO2 are obtained, respectively. By powder X-ray diffraction, ICP and the extraction test, it is confirmed that Ba2+ and K+ occupy the tunnels and are difficult to remove. By electrochemical analyses, we have found that the charge storage of Ba-MnO2 and K-MnO2 basically depends on the SCM, as Ba2+ and K+ stabilized in the tunnels in advance block the intercalation/deintercalation of cations from the electrolyte. Thus, it can be inferred that for α-MnO2 two mechanisms contribute to the charge storage. The contributions of α-MnO2''s mechanisms are estimated. The charges based on the TSM predominantly account for 81.2–89.9% of the total charges. The charges on the SCM may contribute to 7.9–16.8% and are not negligible. The charges from double-layer capacitance may be negligible, since it is only 1.1–4.1%. [Copyright &y& Elsevier]

Abstract: Porous graphitic carbons were prepared by combining chemical activation (ZnCl2) with catalytic graphitization (metal Fe and Ni). The activating agent ZnCl2 increased the surface area of porous carbon, and the catalyst (Fe, Ni) accelerated the graphitization. With increasing heat treatment temperature (600–900°C), metal Fe and Ni promoted the degree of graphitization which was characterized by powder X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy. The surface area of samples prepared using Fe and Ni catalysts varied from 275 to 787m2 g−1 and from 83 to 121m2 g−1, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The activated carbons (ACs) prepared from mesophase pitch with KOH etching are used to fabricate electrodes for electric double layer capacitors. The ACs with pre-carbonization are also prepared. Nitrogen adsorption at 77K is used to characterize the surface area and porous structure of the ACs, which show a bimodal pore distribution. By adjusting the residence time at 800°C, the intersection of the ACs’ microcrystallites is changed and the peak value varies between 1.7nm and 2.1nm. Pre-carbonization promotes the growth of graphitic microcrystallites and hinders the crystallites from intersecting, and thus the surface area decreases and the size of the pore is more difficult to adjust. The performance of the ACs in the organic solvent (1M of Et4NBF4 in propylene carbonate) is investigated with voltage sweep cyclic voltammetry and constant-current charge–discharge cycling. The sample with the surface area of 2258 m2/g possesses a specific capacitance as high as 145 F/g. When power density is increased to 12kW/kg, its capacitance does not decrease, and energy density keeps at 31 Wh/kg. [Copyright &y& Elsevier]

Potassium-ion batteries (PIBs) have attracted significant attention due to their low cost and high energy density. Despite being a promising anode candidate for PIBs, graphite is still plagued by limited capacity and fast capacity degradation with low coulombic efficiency (CE). Herein, we propose a high-capacity and highly stable potassium-enriched graphite (KRG) anode which surpasses the limitation of parent graphite. The KRG is characteristic of possessing the potassium-graphite intercalation compounds as a potassiophilic host for uniform and high-efficiency plating/stripping of potassium metal. The robust mixed conducting network possessed by the KRG is beneficial for mitigating drastic volume change of the electrode and improving ion/electron transport. A specific capacity of ∼520 mAh/g was demonstrated for KRG anode as the optimized value to maximize the capacity storage while suppressing dendrites growth. With a stable solid-electrolyte interphase buildup, the KRG/Prussian blue full cell with a controlled anode/cathode capacity ratio of 1.1:1 can deliver a high capacity of 108 mAh/g with a CE of 99% after 180 cycles at 1C. Our results provide valuable insights into the rational design of graphitic anodes for high-energy-density PIBs. [Display omitted] [ABSTRACT FROM AUTHOR]

Controlling graphite intercalation is vital for its use in potassium ion batteries. Prior studies have revealed different intercalation behaviors between a dilute (1 M or less) vs. a concentrated (4 M or higher) ether-based electrolytes: the former forms solvent-co-intercalation while the latter shows binary intercalation. However, no study has been carried out on the intermediate concentrations. In this work, for the first time we report that in an intermediate concentration of electrolyte (2 mol KFSI per kg DME, 2 mol/kg) the electrochemical intercalation of K+ ions in graphite anode exhibits an interesting transition from the ternary to binary process with the increasing cycle number. Furthermore, the pre-formed anion-derived solid-electrolyte interphase on graphite anode in highly concentrated electrolyte was rather stable in 2 mol/kg of KFSI/DME electrolyte, and as a result the graphite anode achieved a two-year cycle life with an ultrahigh capacity retention of 96.7% based on binary intercalation. [Display omitted] In intermediate-concentration ether-based electrolyte (2 mol/kg KFSI/DME) the transition of K+ ion in graphite anode from ternary to binary electrochemical intercalation upon cycling was reported for the time. Furthermore, in 2 mol/kg of KFSI/DME electrolyte the graphite anode with pre-formed anion-derived SEI achieved a two-year cycle life based on binary intercalation. [ABSTRACT FROM AUTHOR]

As emerging energy storage systems, potassium-ion batteries (PIBs) are suitable for grid-scale energy storage application due to the abundant potassium resources and low cost. It is crucial to achieve fast-charging PIBs. However, as the most promising anode candidate, graphite still faces setbacks in achieving fast charging due to poor kinetic issue. Herein, modified graphite (MG) is synthesized to realize the fast potassium ion storage. Benefiting from the enlarged graphitic space combined with unique porous microstructure, MG exhibits outstanding electrochemical performance. The optimized MG anode delivers a specific capacity of 115 mAh g−1 at 4 A g−1 and excellent cycling stability of 1500 cycles at 1 A g−1. Moreover, the full cell assembled with MG anode and Prussian Blue (PB) cathode exhibits a capacity retention of 75% after 20000 cycles at the current density of 1 A g−1. The excellent electrochemical performance is further demonstrated to be associated with dominant pseudo-capacitance behavior, i.e. surface or near-surface reversible redox reactions, which are less affected by solid electrolyte interface (SEI) than intercalation reactions. Our work proposes a strategy to optimize graphitic anode materials by regulating the microstructure and may provide insight into the synthesis of high rate carbon-based anode materials for PIBs. A low-cost modified graphite (MG) is prepared as an anode for potassium-ion batteries (PIBs), achieving higher specific capacity and superior long-term cyclic stability than pristine natural graphite. Moreover, the different impact of solid electrolyte interface (SEI) accumulation during K storage on the two K storage mechanisms (intercalation and adsorption mechanism) is investigated. [Display omitted] • A low-cost modified graphite was prepared as an anode to achieve fast-charging K-ion battery. • The first attempt to illustrate different impact of SEI on intercalation and adsorption K storage mechanisms. • Adsorption K storage mechanism is less affected by SEI than intercalation behavior. [ABSTRACT FROM AUTHOR]

As a promising anode for potassium-ion batteries (PIBs), graphite has drawn great attention due to easy availability, low cost and formation of potassium-based intercalation compound. However, poor cyclic and rate performances due to severe structural degradation limit the practical application of graphite anode. Herein, a low cost mildly-expanded graphite (MEG) with adjustable interlayer lattice distance is synthesized through a wet chemical oxidation route. As anode for PIBs, the MEG exhibited stable intercalation/deintercalation plateaus, outstanding cyclic stability and rate performance. By optimizing the mass ratio between graphite and potassium permanganate oxidant, the MEG anode retaining long-range-ordered domains of graphite delivers a capacity of 88 mAh/g at 1500 mA/g and a capacity retention of 72.3% after 200 cycles at 100 mA/g. The potassium ion full cell assembled with MEGs anode exhibites high energy density and outstanding cyclic stability. Our results demonstrate a promising graphite-based anode for PIBs and provide guidance for the designing of novel carbonic electrodes for PIBs. Image 1 [ABSTRACT FROM AUTHOR]

Abstract The aprotic lithium-oxygen (Li-O 2) batteries based on carbon-based oxygen cathodes usually suffer from low round-trip efficiency. Here we adopt oxygen-enriched carbon nanotubes (CNTs) by acid etching treatment as the cathode, in which a low voltage plateau at ∼3.5 V during charge is exhibited and the initial round-trip efficiency is increased from 69.9% to 76.0%. An optimized integration of electrocatalytic property and electrical conductivity is crucial for the oxidized CNTs cathode to enhance the capacity and cycling performance. In particular, the surface oxygen groups can facilitate the electrocatalysis of O 2 with the enhanced oxygen reduction reaction activity and induce defective lithium peroxide (Li 2 O 2) formation due to their preferential adsorption of O 2 on the oxidized CNTs. Compared to the high crystalline Li 2 O 2 toroids, the defective Li 2 O 2 with poor crystallinity could be decomposed at a lower charge potential, contributing to the enhanced round-trip efficiency of Li-O 2 batteries. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract: The lithium ion batteries using Li4Ti5O12 as the anode material are easily being inflated during charge and discharge, which, however, does not occur in the batteries using graphite as the anode material. The high reduction reactivity of electrolyte on the Li4Ti5O12 material may be the main reason. In this work, the reduction reactivities of electrolyte on the uncoated and carbon-coated Li4Ti5O12 electrodes are compared for the first time. The results show that the reduction decomposition of electrolyte does occur on the uncoated Li4Ti5O12 electrode at around 0.7V, while it only takes place at the first cycle on the carbon-coated Li4Ti5O12 electrode. The carbon coating layers cover the catalytic active sites of Li4Ti5O12 particles and separate the Li4Ti5O12 particles from the electrolyte. A successive solid electrolyte interface (SEI) film is formed on the carbon layer during the formation process, which can prevent the further reduction decomposition of electrolyte at around 0.7V. The impurity phases of rutile and anatase TiO2 do not influence the reduction reactivity of electrolyte. This work is not only important to understand the reduction decomposition mechanism of electrolyte on the Li4Ti5O12 electrode, but also provides an effective solution to suppress the reduction decomposition of electrolyte in the batteries. [Copyright &y& Elsevier]

Abstract: Li4Ti5O12 anode material is synthesized using TiO2 with different crystal structure as titanium source by solid-state method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical test methods are applied to characterize the effects of TiO2 crystal structure on the structure, morphology and electrochemical performance of Li4Ti5O12. Results show that the reaction of TiO2 with Li2CO3 is an exothermic behavior. The reactivity of TiO2 with Li2CO3 gradually decreases and the particles size of Li4Ti5O12 increases with the TiO2 crystal structure changing from amorphous to rutile. The TiO2 crystal structure has a slight influence on the reversibility of Li4Ti5O12, while the specific capacities of Li4Ti5O12 at different current densities decreases obviously with the TiO2 crystal structure changing from amorphous to rutile and the sample using amorphous TiO2 as titanium sources shows highest specific capacity. The capacity retentions of all Li4Ti5O12 samples are above 97% after 50 cycles and these materials show good cycle performance. The TiO2 crystal structure has not large effects on the cycling performance of Li4Ti5O12 material. [Copyright &y& Elsevier]