Research Article Issue
Molecular sieve based Janus separators for Li-ions redistribution to enable stable lithium deposition
Nano Research 2022,15 (6) : 5143-5152
Published: 16 March 2022

During operation of a lithium metal battery, uneven lithium deposition often results in the growth of lithium dendrites and causes a rapid decay in battery performance and even leads to safety issues. This is still the main hurdle hindering the practical application of lithium metal anodes. We report a new type of Janus separator fabricated by introducing a molecular sieve coating on the surface of the polypropylene separator that serves as a redistribution layer for lithium ions. Our results show that using this layer, the growth of lithium dendrites can be largely inhibited and the battery performance greatly improved. In a typical Li||Cu half-cell with the Janus separator, the Coulombic efficiency of the lithium metal anode can be maintained at > 98.5% for over 500 cycles. The cycling life span is also extended by a factor of 8 in the Li||Li symmetric cell. Furthermore, the high-strength coating improves the mechanical properties of the separator, thus enhancing safety. The effectiveness of our strategy is demonstrated by both the inhibited growth of lithium dendrites and the improved battery performance. Our methodology could eventually be generalized for electrode protection in other battery systems.

Editorial Issue
Nano Research 2017,10 (12) : 3941
Published: 06 December 2017

Research Article Issue
Nanostructured organic electrode materials grown on graphene with covalent-bond interaction for high-rate and ultra-long-life lithium-ion batteries
Nano Research 2017,10 (12) : 4245-4255
Published: 06 July 2017

Nanostructured organic tetralithium salts of 2, 5-dihydroxyterephthalic acid (Li4C8H2O6) supported on graphene were prepared via a facile recrystallization method. The optimized composite with 75 wt.% Li4C8H2O6 was evaluated as an anode with redox couples of Li4C8H2O6/Li6C8H2O6 and as a cathode with redox couples of Li4C8H2O6/Li2C8H2O6 for Li-ion batteries, exhibiting a high-rate capability (10 C) and long cycling life (1, 000 cycles). Moreover, in an all-organic symmetric Li-ion battery, this dual-function electrode retained capacities of 191 and 121 mA·h·g–1 after 100 and 500 cycles, respectively. Density functional theory calculations indicated the presence of covalent bonds between Li4C8H2O6 and graphene, which affected both the morphology and electronic structure of the composite. The special nanostructures, high electronic conductivity of graphene, and covalent-bond interaction between Li4C8H2O6 and graphene contributed to the superior electrochemical properties. Our results indicate that the combination of organic salt molecules with graphene is useful for obtaining high-performance organic batteries.

Research Article Issue
Facile synthesis and electrochemical sodium storage of CoS2 micro/nano-structures
Nano Research 2016,9 (1) : 198-206
Published: 14 January 2016

We report the synthesis and electrochemical sodium storage of cobalt disulfide (CoS2) with various micro/nano-structures. CoS2 with microscale sizes are either assembled by nanoparticles (P-CoS2) via a facile solvothermal route or nanooctahedrons constructed solid (O-CoS2) and hollow microstructures (H-CoS2) fabricated by hydrothermal methods. Among three morphologies, H-CoS2 exhibits the largest discharge capacities and best rate performance as anode of sodium-ion batteries (SIBs). Furthermore, H-CoS2 delivers a capacity of 690 mA·h·g-1 at 1 A·g-1 after 100 cycles in a potential range of 0.1–3.0 V, and ~240 mA·h·g-1 over 800 cycles in the potential window of 1.0–3.0 V. This cycling difference mainly lies in the two discharge plateaus observed in 0.1–3.0 V and one discharge plateau in 1.0–3.0 V. To interpret the reactions, X-ray diffraction (XRD) and transmission electron microscopy (TEM) are applied. The results show that at the first plateau around 1.4 V, the insertion reaction (CoS2 + x Na+ + x e- → Nax CoS2) occurs; while at the second plateau around 0.6 V, the conversion reaction (Nax CoS2 + (4 - x ) Na+ + (4 - x )e- → Co + 2Na2S) takes place. This provides insights for electrochemical sodium storage of CoS2 as the anode of SIBs.

Research Article Issue
Spherical nano-Sb@C composite as a high-rate and ultra-stable anode material for sodium-ion batteries
Nano Research 2015,8 (10) : 3384-3393
Published: 08 September 2015

An aerosol spray pyrolysis technique is used to synthesize a spherical nano-Sb@C composite. Instrumental analyses reveal that the micro-nanostructured composite with an optimized Sb content of 68.8 wt% is composed of ultra-small Sb nanoparticles (10 nm) uniformly embedded within a spherical porous C matrix (denoted as 10-Sb@C). The content and size of Sb can be controlled by altering the concentration of the precursor. As an anode material of sodium-ion batteries, 10-Sb@C provides a discharge capacity of 435 mAh·g–1 in the second cycle and 385 mAh·g–1 (a capacity retention of 88.5%) after 500 cycles at 100 mAh·g–1. In particular, the electrode exhibits an excellent rate capability (355, 324, and 270 mAh·g–1 at 1, 000, 2, 000, and 4, 000 mA·g–1, respectively). Such a high-rate performance for the Sb-C anode has rarely been reported. The remarkable electrochemical behavior of 10-Sb@C is attributed to the synergetic effects of ultra-small Sb nanoparticles with an uniform distribution and a porous C framework, which can effectively alleviate the stress associated with a large volume change and suppress the agglomeration of the pulverized nanoparticles during prolonged charge-discharge cycling.

Research Article Issue
Ice-templated preparation and sodium storage of ultrasmall SnO2 nanoparticles embedded in three-dimensional graphene
Nano Research 2015,8 (1) : 184-192
Published: 21 November 2014

We report on the ice-templated preparation and sodium storage of ultrasmall SnO2 nanoparticles (3-4 nm) embedded in three-dimensional (3D) graphene (SnO2@3DG). SnO2@3DG was fabricated by hydrothermal assembly with ice-templated 3DG and a tin source. The structure and morphology analyses showed that 3DG has an interconnected porous architecture with a large pore volume of 0.578 cm3·g-1 and a high surface area of 470.5 m2·g-1. In comparison, SnO2@3DG exhibited a pore volume of 0.321 cm3·g-1 and a surface area of 237.7 m2·g-1 with a homogeneous distribution of ultrasmall SnO2 nanoparticles in a 3DG network. SnO2@3DG showed a discharge capacity of 1, 155 mA·h·g-1 in the initial cycle, a reversible capacity of 432 mA·h·g-1 after 200 cycles at 100 mA·g-1 (with capacity retention of 85.7% relative to that in the second cycle), and a discharge capacity of 210 mA·h·g-1 at a high rate of 800 mA·g-1. This is due to the high distribution of SnO2 nanoparticles in the 3DG network and the enhanced facilitation of electron/ion transport in the electrode.

Research Article Issue
Uniform MnO2 nanostructures supported on hierarchically porous carbon as efficient electrocatalysts for rechargeable Li-O2 batteries
Nano Research 2015,8 (1) : 156-164
Published: 05 November 2014

Through in situ redox deposition and growth of MnO2 nanostructures on hierarchically porous carbon (HPC), a MnO2/HPC hybrid has been synthesized and employed as cathode catalyst for non-aqueous Li-O2 batteries. Owing to the mild synthetic conditions, MnO2 was uniformly distributed on the surface of the carbon support, without destroying the hierarchical porous nanostructure. As a result, the as-prepared MnO2/HPC nanocomposite exhibits excellent Li-O2 battery performance, including low charge overpotential, good rate capacity and long cycle stability up to 300 cycles with controlling capacity of 1, 000 mAh·g-1. A combination of the multi-scale porous network of the shell-connected carbon support and the highly dispersed MnO2 nanostructure benefits the transportation of ions, oxygen and electrons and contributes to the excellent electrode performance.

Research Article Issue
Porous CuO nanowires as the anode of rechargeable Na-ion batteries
Nano Research 2014,7 (2) : 199-208
Published: 12 December 2013

We report the preparation of porous CuO nanowires that are composed of nanoparticles (~50 nm) via a simple decomposition of a Cu(OH)2 precursor and their application as the anode materials of rechargeable Na-ion batteries. The as-prepared porous CuO nanowires exhibit a Brunauer–Emmett–Teller (BET) surface area of 13.05 m2·g−1, which is six times larger than that of bulk CuO (2.16 m2·g–1). The anode of porous CuO nanowires showed discharge capacities of 640 mA·h·g–1 in the first cycle and 303 mA·h·g–1 after 50 cycles at 50 mA·g–1. The high capacity is attributed to porous nanostructure which facilitates fast Na-intercalation kinetics. The mechanism of electrochemical Na-storage based on conversion reactions has been studied through cyclic voltammetry, X-ray diffraction (XRD), Raman spectroscopy, and high resolution transmission electron microscopy (HRTEM). It is demonstrated that in the discharge process, Na+ ions first insert into CuO to form a Cu1xCuxO1x/2 solid and a Na2O matrix then Cu1xCuxO1x/2 reacts with Na+ to produce Cu2O, and finally Cu2O decompose into Cu nanoparticles enclosed in a Na2O matrix. During the charge process, Cu nanoparticles are first oxidized to generate Cu2O and then converted back to CuO. This result contributes to the design and mechanistic analysis of high-performance anodes for rechargeable Na-ion batteries.

Research Article Issue
Composite of sulfur impregnated in porous hollow carbon spheres as the cathode of Li–S batteries with high performance
Nano Research 2013,6 (1) : 38-46
Published: 06 December 2012

Carbon–sulfur composites as the cathode of rechargeable Li–S batteries have shown outstanding electrochemical performance for high power devices. Here, we report the promising electrochemical charge–discharge properties of a carbon–sulfur composite, in which sulfur is impregnated in porous hollow carbon spheres (PHCSs) via a melt-diffusion method. Instrumental analysis shows that the PHCSs, which were prepared by a facile template strategy, are characterized by high specific surface area (1520 m2·g–1), large pore volume (2.61 cm3·g–1), broad pore size distribution from micropores to mesopores, and high electronic conductivity (2.22 S·cm–1). The carbon–sulfur composite with a sulfur content of 50.2 wt.% displays an initial discharge capacity of 1450 mA·h·g–1 (which is 86.6% of the theoretical specific capacity) and a reversible discharge capacity of 1357 mA·h·g–1 after 50 cycles at 0.05 C charge–discharge rate. At a higher rate of 0.5 C, the capacity stabilized at around 800 mA·h·g–1 after 30 cycles. The results illustrate that the porous carbon–sulfur composites with hierarchically porous structure have potential application as the cathode of Li–S batteries because of their effective improvement of the electronic conductivity, the repression of the volume expansion, and the reduction of the shuttling loss.

Open Access Research Article Issue
Magnesium Microspheres and Nanospheres: Morphology-Controlled Synthesis and Application in Mg/MnO2 Batteries
Nano Research 2009,2 (9) : 713-721
Published: 12 September 2009

In this paper, we report on the morphology-controlled synthesis of magnesium micro/nanospheres and their electrochemical performance as the anode of primary Mg/MnO2 batteries. Mg micro/nanoscale materials with controllable shapes have been prepared via a conventional vapor-transport method under an inert atmosphere by adjusting the deposition temperatures. Extensive analysis techniques including SEM, XRD, TEM/HRTEM, and Brunauer–Emmett–Teller (BET) were carried out to characterize the as-obtained samples. The results show that the Mg samples are microspheres or micro/nanospheres with specific surface areas of 0.61–1.92 m2/g. The electrochemical properties of the as-prepared Mg and commercial Mg powders were further studied in terms of their linear sweep voltammograms, impedance spectra, and discharge capability. By comparing the performance of different inhibitors in electrolytes, it was found that NaNO2 (2.6 mol/L) as an inhibitor in the Mg(NO3)2 (2.6 mol/L) electrolyte affords a Mg electrode with high current density and low corrosion rate. In particular, the Mg sample consisting of microspheres with a diameter of 1.5–3.0 μm and nanospheres with a diameter of 50–150 nm exhibited superior electrode properties including negative initial potential (−1.08 V), high current density (163 mA/cm2), low apparent activation energy (5.1 kJ/mol), and high discharge specific capacity (784 mAh/g). The mixture of Mg nanospheres and microspheres is promising for application in primary Mg/MnO2 batteries because of the sufficient contact with the electrolyte and greatly reduced charge transfer impedance and polarization.

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