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For building high-energy density asymmetric supercapacitors, developing anode materials with large specific capacitance remains a great challenge. Although Fe2O3 has been considered as a promising anode material for asymmetric supercapacitors, the specific capacitance of the Fe2O3-based anodes is still low and cannot match that of cathodes in the full cells. In this work, a composite material with well dispersed Fe2O3 quantum dots (QDs, ≈2 nm) decorated on functionalized graphene-sheets (FGS) is prepared by a facile and scalable method. The Fe2O3 QDs/FGS composites exhibit a large specific capacitance up to 347 F g−1 in 1 m Na2SO4 between -1 and 0 V versus Ag/AgCl. An asymmetric supercapacitor operating at 2 V is fabricated using Fe2O3/FGS as anode and MnO2/FGS as cathode in 1 m Na2SO4 aqueous electrolyte. The Fe2O3/FGS//MnO2/FGS asymmetric supercapacitor shows a high energy density of 50.7 Wh kg−1 at a power density of 100 W kg−1 as well as excellent cycling stability and power capability. The facile synthesis method and superior supercapacitive performance of the Fe2O3 QDs/FGS composites make them promising as anode materials for high-performance asymmetric supercapacitors. [ABSTRACT FROM AUTHOR]

Immiscibility between polymer and ionic liquid, and the loss of solid-state configuration when ionic liquid loading becomes too high have been addressed by creating poly(ethylene oxide)-immobilized ionogel through a facile mechanochemical method. The poly(ethylene oxide)-immobilized ionogel with ionic liquid loading as high as 50 wt% demonstrates a high room-temperature ionic conductivity in the order of 10-4 S cm-1. [ABSTRACT FROM AUTHOR]

The practical use of solid‐state lithium metal batteries is hindered by the rapid growth of lithium dendrites through the solid electrolyte, leading to a short lifespan, and poor performance at high rates. The mass transport in anode bulk is proposed as a critical reason related to the chemo‐mechanical failure of the interface and growth of lithium dendrites. In this study, a lithium‐composite anode with a smartly integrated LiC6 phase is developed using a thermodynamic reaction between molten Li and thermally expanded graphite. The gravity segregation effect creates a gradient dispersion of LiC6 in Li, resulting in improved bulk Li diffusion kinetics (70 times higher than that of a pure Li anode). This composite electrode exhibits low interfacial resistance (≈2.3 Ω cm2) and an ultra‐high critical current density of 2.4 mA cm−2 in all‐solid‐state symmetric cells at room temperature. During repeated Li stripping/plating cycles, the enhanced bulk Li diffusion kinetics maintain the close interfacial contact, leading to excellent long‐term cycling stability for over 4000 h with a high cumulative areal capacity. These findings provide valuable insights that promoted mass transport in lithium metal anode is of great benefit to high‐performance solid‐state lithium metal batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] The synthesis of new carbon nanoflake (CNF)-supported composites with a La 2 O 3 /CNFs@C core–shell structure is described. The carbon surface is functionalized by oxidation with nitric acid vapor for 1, 3, or 6 h. The evolutions of the structure and composition are investigated by transmission electron microscopy and X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

LiNi0.5Mn1.5O4 nanorods wrapped with graphene nanosheets have been prepared and investigated as high energy and high power cathode material for lithium-ion batteries. The structural characterization by X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy indicates the LiNi0.5Mn1.5O4 nanorods prepared from β-MnO2 nanowires have ordered spinel structure with P4332 space group. The morphological characterization by scanning electron microscopy and transmission electron microscopy reveals that the LiNi0.5Mn1.5O4 nanorods of 100-200 nm in diameter are well dispersed and wrapped in the graphene nanosheets for the composite. Benefiting from the highly conductive matrix provided by graphene nanosheets and one-dimensional nanostructure of the ordered spinel, the composite electrode exhibits superior rate capability and cycling stability. As a result, the LiNi0.5Mn1.5O4-graphene composite electrode delivers reversible capacities of 127.6 and 80.8 mAh g−1 at 0.1 and 10 C, respectively, and shows 94% capacity retention after 200 cycles at 1 C, greatly outperforming the bare LiNi0.5Mn1.5O4 nanorod cathode. The outstanding performance of the LiNi0.5Mn1.5O4-graphene composite makes it promising as cathode material for developing high energy and high power lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Lithium (Li) metal batteries (LMBs) have garnered significant research attention due to their high energy density. However, uncontrolled Li dendrite growth and the continuous accumulation of "dead Li" directly lead to poor electrochemical performance in LMBs, along with serious safety hazards. These issues have severely hindered their commercialization. In this study, a lithiophilic layer of Sn-Cu 2 O is constructed on the surface of copper foam (CF) grown with Cu nanowire arrays (SCCF) through a combination of electrodeposition and plasma reduction. Sn-Cu 2 O, with excellent lithiophilicity, reduces the Li nucleation barrier and promotes uniform Li deposition. Simultaneously, the high surface area of the nanowires reduces the local current density, further suppressing the Li dendrite growth. Therefore, at 1 mA cm -2 , the half cells and symmetric cells achieve high Coulombic efficiency (CE) and stable operation for over 410 cycles and run smoothly for more than 1350 h. The full cells using an LFP cathode demonstrate a capacity retention rate of 90.6% after 1000 cycles at 5 C, with a CE as high as 99.79%, suggesting excellent prospects for rapid charging and discharging and long-term cyclability. This study provides a strategy for modifying three-dimensional current collectors for Li metal anodes, offering insights into the construction of stable, safe, and fast-charging LMBs.

The electrical conductivity, density and diffusion coefficients of trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide ([P66614][NTf 2 ]) ionic liquid and its binary solutions in acetonitrile, propionitrile, dimethyl and diethyl carbonates were measured in the temperature range of 293-348 K. The electrical conductivity - ionic liquid mole fraction dependencies for the binary solutions were fitted with the empirical Casteel-Amis equation. The temperature dependencies of electrical conductivity were analyzed using the Arrhenius, Litovitz and Vogel-Fulcher-Tammann approaches. The dependences of the Arrhenius activation energy and pre-exponential factor on the mole fraction of ionic liquid in the solutions were fitted with the empirical equations proposed in the literature. The thermo-gravimetric analysis combined with mass spectrometry demonstrated the high thermal stability of [P66614][NTf 2 ] up to 600 K. At higher temperatures the decomposition of [P66614][NTf 2 ] proceeded via the elimination of alkyl radicals as a result of the nucleophilic attack of reactive intermediates to the [P66614] + cation with the formation of trialkylphosphines. The activation energies of the thermal destruction of [P66614][NTf 2 ] were calculated using the Kissinger equation and non-linear integral isoconversional model.

Composite polymer electrolytes provide an emerging solution for new battery development by replacing liquid electrolytes, which are commonly complexes of polyethylene oxide (PEO) with ceramic fillers. However, the agglomeration of fillers and weak interaction restrict their conductivities. By contrast with the prevailing methods of blending preformed ceramic fillers within the polymer matrix, here we proposed an in situ synthesis method of SiO 2 nanoparticles in the PEO matrix. In this case, robust chemical interactions between SiO 2 nanoparticles, lithium salt and PEO chains were induced by the in situ non-hydrolytic sol gel process. The in situ synthesized nanocomposite polymer electrolyte delivered an impressive ionic conductivity of ~1.1 × 10 -4 S cm -1 at 30 °C, which is two orders of magnitude higher than that of the preformed synthesized composite polymer electrolyte. In addition, an extended electrochemical window of up to 5 V vs. Li/Li + was achieved. The Li/nanocomposite polymer electrolyte/Li symmetric cell demonstrated a stable long-term cycling performance of over 700 h at 0.01-0.1 mA cm -2 without short circuiting. The all-solid-state battery consisting of the nanocomposite polymer electrolyte, Li metal and LiFePO 4 provides a discharge capacity of 123.5 mAh g -1 , a Coulombic efficiency above 99% and a good capacity retention of 70% after 100 cycles., Competing Interests: The authors declare no conflict of interest.

Although the theoretical capacitance of MnO 2 is 1370 F g -1 based on the Mn 3+ /Mn 4+ redox couple, most of the reported capacitances in literature are far below the theoretical value even when the material goes to nanoscale. To understand this discrepancy, in this work, the electrochemical behavior and charge storage mechanism of K + -inserted α-MnO 2 (or K x MnO 2 ) nanorod arrays in broad potential windows are investigated. It is found that electrochemical behavior of K x MnO 2 is highly dependent on the potential window. During cyclic voltammetry cycling in a broad potential window, K + ions can be replaced by Na + ions, which determines the pseudocapacitance of the electrode. The K + or Na + ions cannot be fully extracted when the upper cutoff potential is less than 1 V vs Ag/AgCl, which retards the release of full capacitance. As the cyclic voltammetry potential window is extended to 0-1.2 V, enhanced specific capacitance can be obtained with the emerging of new redox peaks. In contrast, the K + -free α-MnO 2 nanorod arrays show no redox peaks in the same potential window together with much lower specific capacitance. This work provides new insights on understanding the charge storage mechanism of MnO 2 and new strategy to further improve the specific capacitance of MnO 2 -based electrodes.