•xLi2MnO3·(1−x)LiMnO2 nanorods are prepared by a pyrolysis reduction of m-Li2MnO3.•m-LiMnO2 content in the nanorods is adjustable by changing the stearic acid amount.•Those nanorods has initial charge/discharge profile similar to Li-rich material.•Improved cyclic and rate performance with higher reversible capacity is obtained.Layered-layered type xLi2MnO3·(1−x)LiMnO2 (x = 0.91, 0.78, 0.67, 0.54, 0.42, and 0.32) nanorods with a diameter of 100–200 nm and length of 400–1000 nm are prepared through a pyrolysis reduction process of monoclinic Li2MnO3 (m-Li2MnO3) nanorods. All the synthesized xLi2MnO3·(1−x)LiMnO2 nanorods exhibit the main characteristic diffraction peaks of m-Li2MnO3 in addition to some weak peaks attributable to m-LiMnO2 especially for those composites with x < 0.67. When used as cathode material of Li-ion battery, those xLi2MnO3·(1−x)LiMnO2 nanorods show an initial charge/discharge profile similar to the Li-rich solid solution in the voltage window of 2.0–4.8 V. The m-LiMnO2 portion in those synthesized composites can significantly enhance the reversible capacity but lower the cyclic stability, while the m-Li2MnO3 portion can improve the cyclic stability due to its retardation effect of the layered-to-spinel transformation during the charge/discharge processes, and thus xLi2MnO3·(1−x)LiMnO2 nanorods with x = 0.54 exhibits the best cyclic and rate performance since it contains appropriate m-Li2MnO3/m-LiMnO2 contents to balance the reversible capacity and Jahn-Teller effect. The present findings demonstrate an effective strategy for the development of low-cost pure Mn-based Li-rich layered cathode materials with adjustable reversible capacity, cyclic and rate performance by tailoring the composition.Download high-res image (382KB)Download full-size image

•PbO2 nanowires were electrodeposited using an anodic aluminum oxide membrane.•Ozone current efficiency remained steady at approximately 20%.•The performance did not decrease significantly during a 30-day period.PbO2 nanowires that were approximately 200 nm in diameter were obtained by template electrodeposition using an anodic aluminum oxide membrane. A proton exchange membrane (PEM) water electrolyzer with an anode made of this PbO2 nanowire, a cathode made of carbon supported platinum, and Nafion®-117 membrane operating at a current density of 1.5 A cm−2, an ozone current efficiency of 20% was achieved, and did not attenuate significantly during a 30-day period.

•Layered xLi2MnO3·(1 − x)LiMnO2 nanoplates are firstly prepared by pyrolysis reduction.•Transition metal layer of the nanoplate is parallel to the plate’s radial direction.•Nanoplate can retard the phase transformation and improve the cyclic stability.•Electrochemical property is improved by tailoring the morphology and composition.•Improved cyclic performance with reversible capacity up to 270 mAh g−1 is obtained.Layered xLi2MnO3·(1 − x)LiMnO2 (x = 0.57, 0.48, and 0.44) nanoplates are firstly prepared by pyrolysis reducing the electrochemically inactive monoclinic Li2MnO3 nanoplates, which is synthesized via a solid-state reaction by using home-made MnO2 nanoplates as self-template. The obtained xLi2MnO3·(1 − x)LiMnO2 nanoplates have a diameter of ∼200 nm and thickness of ∼60 nm with high crystallinity and the transition metal layers parallel to the plate’s radial direction. Although these xLi2MnO3·(1 − x)LiMnO2 nanoplates cause a longer Li+ diffusion distance, and then a lower reversible capacity as compared to the nanoparticle-like counterpart, the nanoplate-like morphology of these xLi2MnO3·(1 − x)LiMnO2 (especially with x < 0.5) are beneficial for retarding the layer-to-spinel phase transformation during the charge/discharge processes, and resulting in significant improvement of the cyclic stability. Moreover, the reduced reversible capacity caused by the longer Li+ diffusion distance of the nanoplate-like morphology can be offset by decreasing the x value, and the xLi2MnO3·(1 − x)LiMnO2 nanoplates with x = 0.44 performs a maximum reversible capacity as high as 270 mAh g−1 with a well cyclic performance. The present findings indicate that the cyclic performance and reversible capacity of xLi2MnO3·(1 − x)LiMnO2 can be improved by tailoring the particle’s morphology and composition, and demonstrate a simple and effective strategy for the development of the Co/Ni-free Mn-based layered Li-rich cathode materials with good cyclic and high reversible capacity.

•Single crystal LiMn2O4 rods are prepared by using γ-MnOOH rods as self-template.•LiMn2O4 rods obtained at 600 °C (LMO-600) exhibit the best performance.•LMO-600 has an initial capacity (125.6 mAh g−1) and high rate capacity.•Rod-like structure and 95.6% capacity are preserved after 100 cycles at 3 C.LiMn2O4 submicro-rods are synthesized via solid-state reaction by using γ-MnOOH submicro-rods as self-template, which is prepared via a solvothermal process in the presence of ethanol/water solvent by using KMnO4 and MnCl2 as raw materials. It is found that the ethanol content in a certain ethanol/water volume ratio range has no obvious influence on the crystal phase and morphology of γ-MnOOH submicro-rods derived from the solvothermal process, and a proper solid-state reaction temperature range for the preparation of spinel LiMn2O4 submicro-rods by using γ-MnOOH submicro-rods as self-template is 500∼700 °C. Moreover, the effects of reaction temperature on structure, crystal phase and electrochemical performance of the obtained LiMn2O4 submicro-rods as cathode material of Li-ion battery are studied in detail, and the LiMn2O4 submicro-rods obtained at 600 °C exhibit the best electrochemical performance with an initial capacity of 125.6 mAh g−1 and 95.6% capacity retention after 100 cycles at 3 C. Importantly, the rod-like nanostructure and crystal phase can be well preserved after prolonged the charge/discharge cycling time at a relatively high current rate, indicating its good structural stability as cathode material. Further development of this γ-MnOOH submicro-rod self-templating method may be interesting for the commercial production of LiMn2O4 for Li-ion batteries with superior high-rate capability and good cycling stability.

•P2-Na0.67Mn0.65Fe0.2Ni0.15O2 as Na storage cathode can deliver a high reversible capacity of 208 mAh g−1.•The P2-Na0.67Mn0.65Fe0.2Ni0.15O2 electrode exhibits a improved cycling stability.•The improved electrochemical performance is due to the Ni substitution.Na0.67Mn0.65Fe0.35-xNixO2 as a Na storage cathode material was prepared by a sol-gel method. The XRD measurement demonstrated that these samples have a pure P2 phase. The charging/discharging tests exhibit that the Na0.67Mn0.65Fe0.35O2 electrode has a high initial capacity of 204 mAh g−1 with a slow capacity decay to 136 mAh g−1, showing higher capacity and considerable cycling performance. When partially substituting Ni for Fe, the Na0.67Mn0.65Fe0.2Ni0.15O2 electrode exhibits higher reversible capacity of 208 mAh g−1 and improved cycling stability with 71% capacity retention over 50 cycles. The greatly improved electrochemical performance for the Na0.67Mn0.65Fe0.2Ni0.15O2 electrode apparently belongs to the contribution of the Ni substitution, which facilitates to improve the electrochemical reversibility of the electrode and alleviate the Jahn-Teller distortion of Mn(III). Therefore, the Ni-substituted Na0.67Mn0.65Fe0.2Ni0.15O2 possibly serves as a promising high capacity and stable cathode material for sodium ion battery applications.

Well-crystallized FeSbO4 nanorods with rutile-like structure are synthesized through a solid-state reaction and used as cathode material of Li-ion battery for the first time. The obtained nanorods can react with ∼11 Li-ions per FeSbO4 unit with a specific discharge capacity of 1 100 mAh·g− between 0.1 and 2.0 V. Three discharge plateaus can be observed during the fully discharging process, but the reversible reaction with ∼1 Li occurs between 1.5 V and 4.5 V vs. Li+/Li, and the reversible capacity is only 50–80 1 mAh·g−. FeSbO4 nanorods have a stable cyclic performance between 1.5 V and 4.5 V and it can be used as cathode material for rechargeable Li-ion battery.