The chloride ion battery is an attractive rechargeable battery owing to its high theoretical energy density and sustainable components. An important challenge for research and development of chloride ion batteries lies in the innovation of the cathode materials. Here we report a nanostructured chloride ion-doped polymer, polypyrrole chloride, as a new type of potential cathode material for the chloride ion battery. The as-prepared polypyrrole chloride@carbon nanotubes (PPyCl@CNTs) cathode shows a high reversible capacity of 118 mAh g–1 and superior cycling stability. Reversible electrochemical reactions of the PPyCl@CNTs cathode based on the redox reactions of nitrogen species and chloride ion transfer are demonstrated. Our work may guide and offer electrode design principles for accelerating the development of rechargeable batteries with anion transfer.Keywords: cathode materials; chloride ion batteries; electrochemistry; polypyrrole chloride; rechargeable batteries;

•NMP was found to be intercalated into the FeOCl layers during the drying of the electrode coating at 373 K.•The electrolyte component can intercalate into the FeOCl layers without discharge and charge at 298 K.•The phase transformation of Fe3+/Fe2+ by the chloride ion transfer in the FeOCl electrode during cycling was confirmed by the EDS and FTIR results.Layered metal oxychloride FeOCl is considered as one of the promising cathode materials for chloride ion batteries due to its abundant elemental components and high capacity. Herein, we report the intercalation and electrochemical behaviors of the layered FeOCl material in the chloride ion battery. The intercalation of N-methyl-2-pyrrolidinone into the FeOCl layers has been found during the drying of the electrode coating at 373 K. The electrolyte component can also be intercalated into the FeOCl layers at 298 K without charge and discharge. The intercalation by these organic components results in evident expansion of the layers. Repeated charge and discharge cycling contributes to an activation of the FeOCl electrode and thus an increase of the discharge capacity. The results of elemental analysis and Fourier transform infrared spectroscopy confirm the chloride ion transfer of the FeOCl electrode during cycling.Download high-res image (148KB)Download full-size image

•New Zr-based bulk metallic glasses with superior Glass-forming ability and high plasticity were prepared.•The Zr-Cu-Al-Ni-Co amorphous alloy shows a supercooled liquid region width of 80 K and a compressive plasticity of 7.4 %.•The improvements of the Glass-forming ability and mechanical properties were studied.Zr-based bulk metallic glasses have been considered as promising engineering materials. However, their widespread application is limited by their contrasting properties of glass-forming ability (GFA) and plasticity. Herein, the effects of Ni substitution by Co on the GFA and plasticity of the representative Zr-based metallic glass of Zr65Cu17.5Al7.5Ni10 were investigated. A series of Zr65Cu17.5Al7.5Ni10 − xCox (x = 0, 2, 4, 6, 7, 8, 10) rod samples with 2 mm in diameter were prepared by injection copper mold casting method. Amorphous structure was successfully achieved when the Co content is less than 8 at.%. Importantly, the Co addition contributed to significant enhancements in both GFA and plasticity of the amorphous Zr65Cu17.5Al7.5Ni10 − xCox (x = 0, 2, 4, 6, 7) alloys. The as-prepared Zr65Cu17.5Al7.5Ni8Co2 amorphous alloy shows the best and attractive performance with a supercooled liquid region width of 80 K and a compressive plasticity of 7.4%, which are much higher than 50 K and 0.2% of the pristine Zr65Cu17.5Al7.5Ni10 amorphous alloy, demonstrating that the Co substituted Zr-Al-Ni-Cu metallic glass has the potential to be used for engineering applications.

•Li2CoTiO4 cathode materials with tunable nanostructures were synthesized.•Small particle or grain size can increase the Li ion diffusion rate.•Li2CoTiO4 with small particle size has good cycle stability and rate capability.Cation disordered Li2CoTiO4 titanate with 3D lithium ion channels could be a promising new cathode material for lithium ion batteries due to its high theoretical capacity. Herein the Li2CoTiO4 materials with tunable nanostructures were synthesized by a sol–gel method and subsequent heat treatment at different temperatures. The microstructure and electrochemical properties of the nanocrystalline Li2CoTiO4 materials have been systematically investigated. The Li2CoTiO4 material synthesized at lower temperature possessed smaller particle size and grain size, and allowed a higher reversible extraction of lithium ions per formula unit. Furthermore, the small particle size enabled insertion of lithium along short diffusion paths, and thus an increase of the lithium ion diffusion coefficient.

Spinel LiMnTiO4 as the cathode material for Li-ion batteries has been synthesized by a sol–gel method. The LiMnTiO4 cathode possesses two voltage plateaus, and exhibits an initial discharge capacity of 203.3 mAh g−1. After 47 charge–discharge cycles, the capacity retention of the LiMnTiO4 cathode is 77.5 %, which is much higher than that of LiMn2O4 (47.9 %). Ti substitution can successfully suppress the formation of tetragonal phase during cycling and hence increase the structural stability; however, it decreases the discharge capacity. Multi-walled carbon nanotubes (MWCNTs) were mechanically milled with the pristine LiMnTiO4. The as-prepared LiMnTiO4/MWCNTs composite electrode exhibits significantly improved electrochemical properties including rate capability and cycling stability, as compared with LiMnTiO4.

The Co-S/x wt.% AB5 (x=0, 10, 20, 30) composite materials were prepared by simply mixing Co-S material fabricated by hydrothermal method and AB5 alloy. The structure and morphology of the composite materials were characterized by XRD and SEM, respectively. The electrochemical properties of the composite electrodes were studied by the galvanostatic charge, discharge test and electrochemical impedance spectroscopy. The results showed that the Co-S/20 wt.% AB5 composite electrode showed the highest discharge capacity and the best cycling stability. The existence of the AB5 alloy improved the electrochemical activity of composite electrodes, reduced the electrochemical polarization resistances and promoted the electrochemical conversion reaction between Co and Co(OH)2. In order to improve the utilization rate of active materials, 0.01 mol/L Na2S2O3 was added into the electrolyte. The electrochemical properties of the composite electrode were significantly enhanced. After fifty cycles, the discharge capacity of the composite electrode increased from 407 to 481.7 mAh/g and the capacity retention increased from 79.7% to 91.2%.

We report a new type of rechargeable chloride ion battery using vanadium oxychloride (VOCl) as cathode and magnesium or magnesium/magnesium chloride (MgCl2/Mg) as anode, with an emphasis on the VOCl-MgCl2/Mg full battery. The charge and discharge mechanism of the VOCl cathode has been investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical measurements, demonstrating the chloride ion transfer during cycling. The VOCl cathode can deliver a reversible capacity of 101 mAh g–1 at a current density of 10 mA g–1 and a capacity of 60 mAh g–1 was retained after 53 cycles in this first study.Keywords: chloride ion; electrochemistry; magnesium anode; rechargeable battery; vanadium oxychloride