Lithium-ion and solvent co-intercalation enhancing the energy density of fluorinated graphene cathode

Fluorinated carbons CF_xhold the highest theoretical energy density(e.g.,2180 W h kg^(-1)when x=1)among all cathode materials of lithium primary batteries.However,the low conductivity and severe polarization limit it to achieve its theory.In this study,we design a new electrolyte,namely 1 M LiBF_(4)DMSO:DOL(1:9 vol.),achieving a high energy density in Li/CF_xprimary cells.The DMSO with a small molecular size and high donor number successfully solvates Li^(+)into a defined Li^(+)-solvation structure.Such solvated Li^(+)can intercalate into the large-spacing carbon layers and achieve an improved capacity.Consequently,when discharged to 1.0 V,the CF_(1.12)cathode demonstrates a specific capacity of 1944 m A h g^(-1)with a specific energy density of 3793 W h kg^(-1).This strategy demonstrates that designing the electrolyte is powerful in improving the electrochemical performance of CF_(x) cathode.

High-performance magnesium/sodium hybrid ion battery based on sodium vanadate oxide for reversible storage of Na^(+)and Mg^(2+)

Magnesium ion batteries(MIBs)are a potential field for the energy storage of the future but are restricted by insufficient rate capability and rapid capacity degradation.Magnesium-sodium hybrid ion batteries(MSHBs)are an effective way to address these problems.Here,we report a new type of MSHBs that use layered sodium vanadate((Na,Mn)V_(8)O_(20)·5H_(2)O,Mn-NVO)cathodes coupled with an organic 3,4,9,10-perylenetetracarboxylic diimide(PTCDI)anode in Mg^(2+)/Na^(+)hybrid electrolytes.During electrochemical cycling,Mg^(2+)and Na^(+)co-participate in the cathode reactions,and the introduction of Na^(+)promotes the structural stability of the Mn-NVO cathode,as cleared by several ex-situ characterizations.Consequently,the Mn-NVO cathode presents great specific capacity(249.9 mA h g^(−1)at 300 mA g^(−1))and cycling(1500 cycles at 1500 mA g^(−1))in the Mg^(2+)/Na^(+)hybrid electrolytes.Besides,full battery displays long lifespan with 10,000 cycles at 1000 mA g^(−1).The rate performance and cycling stability of MSHBs have been improved by an economical and scalable method,and the mechanism for these improvements is discussed.

Tailoring Nitrogen Terminals on MXene Enables Fast Charging and Stable Cycling Na-Ion Batteries at Low Temperature

Sodium-ion batteries stand a chance of enabling fast charging ability and long lifespan while operating at low temperature(low-T).However,sluggish kinetics and aggravated dendrites present two major challenges for anodes to achieve the goal at low-T.Herein,we propose an interlayer confined strategy for tailoring nitrogen terminals on Ti_(3)C_(2) MXene(Ti_(3)C_(2)-N_(funct)) to address these issues.The introduction of nitrogen terminals endows Ti_(3)C_(2)-N_(funct) with large interlayer space and charge redistribution,improved conductivity and sufficient adsorption sites for Na^(+),which improves the possibility of Ti_(3)C_(2) for accommodating more Na atoms,further enhancing the Na^(+) storage capability of Ti_(3)C_(2).As revealed,Ti_(3)C_(2)-N_(funct) not only possesses a lower Na-ion diffusion energy barrier and charge trans-fer activation energy,but also exhibits Na^(+)-solvent co-intercalation behavior to circumvent a high de-solvation energy barrier at low-T.Besides,the solid electrolyte interface dominated by inorganic com-pounds is more beneficial for the Na^(+)transfer at the electrode/electrolyte interface.Compared with of the unmodified sample,Ti_(3)C_(2)-Nfunct exhibits a twofold capacity(201 mAh g^(-1)),fast-charging ability(18 min at 80% capacity retention),and great superiority in cycle life(80.9%@5000 cycles)at -25℃.When coupling with Na_(3)V_(2)(PO_(4))_(2)F_(3) cathode,the Ti_(3)C_(2)-N_(funct)//NVPF exhibits high energy density and cycle stability at -25℃.

Utilizing the full capacity of carbon black as anode for Na-ion batteries via solvent co-intercalation

Carbonaceous materials have long been considered promising anode materials for Na-ion batteries. However, the electrochemical performance of conventional carbon anodes is generally poor because the sodium ion storage solely relies on the disordered region of the carbon materials in a carbonate-based electrolyte. The solvent co-intercalation mechanism for Na ions has been recently reported in natural graphite anodes for Na-ion batteries with ether-based electrolytes, but their capacities are still unsatisfactory. We show here for the first time that by combining regular Na ion storage in the disordered carbon layer and solvent co-intercalation mechanism in the graphitized layer of a commercial N330 carbon black as an anode material for Na-ion batteries in ether-based electrolyte, the reversible capacity could be fully realized and doubled in magnitude. This unique sodium intercalation process resulted in a significantly improved electrochemical performance for the N330 electrode with an initial reversible capacity of 234 mAh.g-1 at 50 mA.g-1 and a superior rate capability of 105 mAh.g-1 at 3,200 mA-g-1. When cycled at 3,200 mA.g-1 over 2,000 cycles, the electrode still exhibited a highly reversible capacity of 72 mAh.g-1 with a negligible capacity loss per cycle （0.0167%）. Additionally, surface-sensitive C K-edge X-ray absorption spectroscopy, with the assistance of electrochemical and physicochemical characterizations, helped in identifying the controlled formation and evolution of a thin and robust solid electrolyte interphase film. This film not only reduced the resistance for sodium ion diffusion, but also maintained the structural stability of the electrode for extended cycle reversibility. The superior electrochemical performance of N330 carbon black strongly demonstrated the potential of applying ether-based electrolytes for a wide range of carbon anodes apart from natural graphite.

Ultrathin Zn-free anode based on Ti_(3)C_(2)T_(x) and nanocellulose enabling high-durability aqueous hybrid Zn-Na battery with Zn2+/Na+co-intercalation mechanism

With low cost and high safety,aqueous zinc-based batteries have received considerable interest.Nevertheless,the excess utilization of zinc metal in the anodes of these batteries reduces energy density and increases costs.Herein,an ultrathin electrode of approximately 6.2μm thick is constructed by coating Ti_(3)C_(2)T_(x)/nanocellulose hybrid onto a stainless steel foil.This electrode is used as the Zn-free anode for aqueous hybrid Zn-Na battery,in which,a concentrated electrolyte is used to improve electrochemical reversibility.The Ti_(3)C_(2)T_(x)/nanocellulose coating is found to improve the electrolyte wettability,facilitate desolvation process of hydrated Zn^(2+) ions,lower nucleation overpotential,improve zinc plating kinetics,guide horizontal zinc plating along the Zn(002)facet,and inhibit parasitic side reactions.It is also found that the Na_(3)V_(2)(PO_(4))_(3) cathode material adopts a highly reversible Zn^(2+)/Na^(+)co-intercalation charge storage mechanism in this system.Thanks to these benefits,the assembled hybrid Zn-Na battery exhibits excellent rate capability,superior cyclability,and good anti-freezing ability.This work provides a new concept of electrode design for electrochemical energy storage.

Multi-componential metal intercalated graphite hybrids synthesized by co-intercalation polymerization towards highefficient microwave absorptions

Magnetic expanded graphite(EG)hybrids were synthesized by co-intercalation polymerization of aniline together with transition metal ions.Experimental results show that metal ions(Fe,Co,Ni,Cu)and even their mixtures can co-intercalate into graphite interlayers with flexibly controllable ratios and contents.Among these co-intercalation compounds,Fe/Ni-intercalated graphite with a predesigned mole ratio of 1:3 transforms into NiFe_(2)O_(4)/FeNi_(3)@EG during the annealing process.The synthesized magnetic EG hybrids present multiband microwave absorption in C and X bands due to improved impedance match as well as significantly enhanced interfacial polarization relaxation induced by multi-componential metals.The reflection values of−39.1 dB at 6.95 GHz and−25.7 dB at 9.4 GHz are achieved with an ultra-low loading of 5 wt.%.This work provides a flexible approach for tuning the components and structures of magnetic EG hybrids,which may contribute to the development of microwave absorption materials with superior performances.

Pre-constructed SEI on graphite-based interface enables long cycle stability for dual ion sodium batteries

Lithium batteries have been widely used in all over the world for its high energy density, long-term cycle stability. While the resources of lithium metal and transition metal are limited, which restrict their applications in the grid energy storage. Dual ion sodium batteries(DISBs) possess higher energy density,especially owning high power density for its higher operating voltage(> 4.5 V). Nevertheless, the poor oxidation tolerance of carbonate electrolyte and the co-intercalation of solvents accompanied with anions are main obstacles to make the DISBs commercialization. Herein, a physical barrier(artificial SEI film) is pre-constructed in the Na||graphite batteries to solve these thorny problems. With the CSMG(covered SEI on modified graphite), batteries deliver higher capacity 40 mAh/g even under the current density of 300 mA/g and the capacity retention maintains very well after 100 cycles at a high operating voltage.Moreover, the function mechanism was revealed by in-situ XRD, demonstrating that the pre-constructed SEI can effectively suppress the irreversible phase transition and exfoliation of graphite, resulting from the co-intercalation of anions. Additionally, the work voltage windows of carbonate electrolyte are significantly broadened by establishing electrode/electrolyte interphase. This method opens up an avenue for the practical application of DISBs on the grid energy storage and other fields.

NaF-rich protective layer on PTFE coating microcrystalline graphite for highly stable Na metal anodes

The practical application of Na metal anode is plagued by the dendrite growth,unstable solid electrolyte interphase(SEI)formation and volume change during the cycling process.Herein,poly(tetrafluoroethylene)(noted as PTFE)coating microcrystalline graphite is designed as the sodium metal anode host by a facile and cost-effective strategy.The isotropous microcrystalline graphite(MG)is conducive to guiding Na+to form a co-intercalation structure into MG.And the PTFE coating layer can form NaF as artificial SEI film for uniform ion transport and deposition.As a result,the gained PTFE coating MG electrode can deliver a long-life span over 1,200 cycles with an average Coulombic efficiency(CE)of 99.88%.To note,almost the CE in each cycle is around 99.8%–100%.When assembled with Na_(3)V_(2)(PO_(4))_(2)F_(3)cathode as full cells,the full cell paired with PTFE coating MG electrode can operate much stable than that of MG electrode for the existence of PTFE coating layer.Even utilized as sodium-free Na metal anode paired with Na_(3)V_(2)(PO_(4))_(2)F_(3)cathode,it can also deliver a high initial CE of 76.27%at 0.5 C.After 100 cycles,it still has a high discharge capacity of 83.5 mAh·g^(−1).

Synergistic effect of K^(+)and PANI in vanadium oxide hydration by interlayer engineering boosts the ammonium ion storage

Aqueous ammonium-ion(NH_(4)^(+))hybrid supercapacitor(AA-HSC),as a new type of energy storage device with great potential,is in the initial stage of rapid development.Based on its special energy storage mechanism,exploiting novel NH_(4)^(+)-hostingmaterials is still a great challenge.Herein,vanadium oxide hydration(VOH)tuned by interlayer engineering of K+/PANI co-intercalation,named KVO/PANI,is designed for AA-HSC.Intercalated PANI can shield interaction between NH_(4)^(+)and V–O layers to some extent and enlarge interlayer space,which improves the efficiency of reversible NH_(4)^(+)(de)insertion.However,K+enhances redox activity and electronic conductivity.The synergistic effect of co-intercalation optimizes intercalation pseudocapacitive behavior during the(de)ammonization process,which is reported in NH_(4)^(+)storage for the first time.Theoretical calculations reveal that the lowered electron transport barrier and enhanced electronic conductivity improveNH_(4)^(+)kinetics and exhibit high capacitance for charge storage.The KVO/PANI can deliver the specific capacitance of 340 F g^(−1) at 0.5 A g^(−1) and retain 177 F g^(−1) at 10 A g^(−1).Pairing with activated carbon,the AA-HSC can achieve a decent energy density of 31.8 Wh kg^(−1).This work gives inorganic/organic co-intercalation that can enhance the NH_(4)^(+)storage of VOH by interlayer engineering.The strategy can be used to design other materials for aqueous energy storage systems.