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Abstract: Direct methanol fuel cells (DMFCs) are a promising power source for mobile devices. However, DMFCs currently experience the technical shortcomings of high cost due to the use of noble metal catalysts and polymer electrolyte membranes (PEMs), low power density because of their low catalytic efficiency and cathode catalyst poisoning by methanol, which crosses through the PEM from anode to cathode. Here, we report a new DMFC structure utilizing a polymer fiber membrane (PFM), which is electrolyte-permeable, instead of a PEM. An inexpensive perovskite-type oxide, LaNiO3, is used as the cathode catalyst, which has shown excellent tolerance to methanol-poisoning and good catalytic activity for oxygen reduction reaction (ORR). The peak power density can reach 103 mW cm−2 at 65 °C. This improvement in performance is due to the lower electrical resistance of the PFM. [Copyright &y& Elsevier]

Abstract: Direct borohydride fuel cells (DBFCs), with a series of perovskite-type oxides La1−x Sr x CoO3 (x =0.1–0.5) as the cathode catalysts and a hydrogen storage alloy as the anode catalyst, are studied in this paper. The structures of the perovskite-type catalysts are mainly La1−x Sr x CoO3 ( x =0.1–0.5) oxides phases. However, with the increase of strontium content, the intensities of the X-ray diffraction peaks of the impure phases La2Sr2O5 and SrLaCoO4 are gradually enhanced. Without using any precious metals or expensive ion exchange membranes, a maximum current density of 275mAcm−2 and a power density of 109mWcm−2 are obtained with the Sr content of x =0.2 at 60°C for this novel type of fuel cell. [Copyright &y& Elsevier]

The effects of gas, pressure and temperature on the production of amorphous carbon nadotubes were investigated using an arc discharging furnace at controlled temperature. Co/Ni alloy powder was used as catalyst. The discharge current was 80 A and voltage was 32 V. The optimal parameters were obtained: 600°C temperature, hydrogen gas and 500 torr pressure. The productivity and purity of amorphous carbon nanotubes are 6.5 gram per hour and 80%, respectively. The diameter of the amorphous carbon nanotubes is about 7–20 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] Aqueous zinc-ion batteries (ZIBs) have been considered one of the most promising flexible chemical power sources, because of their affordable cost, absolute security, and lightweight. However, the development of flexible aqueous ZIBs has been hindered by cathode materials due to their unsatisfied capacity, unstable structure, and ambiguous electrochemical energy storage mechanism. To address the above issues, a high-performance manganese cerium-doped dioxide-based core–shell hybrid structure cathode (CS@Ce-MnO 2) has been successfully prepared via a facile low-temperature liquid-phase reaction strategy. Benefit from the delicately designed hierarchical carbon spheres core and cerium-doped manganese dioxide nanosheets shell structure, the capacity and stability of CS@Ce-MnO 2 based flexible ZIBs has been dramatically improved, and the origin of the improved electrochemical performance and storage mechanism was demonstrated by electrochemical methods and ex-site x-ray diffraction (XRD) and scanning electron microscopy (SEM). The principal reason for the high reversible specific capacity is the plausible Zn2+ and H+co-insertion/extraction, while the porous structure of the carbon spheres contributes to the improved electron conduction and ion transport in the MnO 2 matrix. This work provides a new opportunity for high-performance flexible aqueous zinc-ion batteries. [ABSTRACT FROM AUTHOR]

Cycling properties and schematic diagrams of the formation for LMR, LKMR and LKMR@C. [Display omitted] Lithium-rich layered oxides are believed to be the most competitive cathode materials for next-generation lithium-ion batteries (LIBs) due to their high specific capacity, but the poor cycle stability and voltage attenuation severely limit their commercial applications. In this paper, a simple method combining surface treatment via pyrolysis of polyvinyl alcohol (PVA) and potassium ions (K+) doping, is designed to improve the above defects of the cobalt-free Lithium-rich material Li 1.2 Mn 0.6 Ni 0.2 O 2 (LMR). The insoluble surface byproduct Li 2 CO 3 and amorphous carbon nanolayer derived from the pyrolysis process of PVA alleviate the corrosion of acidic species with a favorable conductivity, while a large radius of K+ can enlarge the space of the lithium (Li) layer to facilitate the diffusion of Li+, suppress voltage polarization, and synchronously restrain the transformation from a layered structure to a spinel-like structure. After modification, the LMR material exhibits a great initial discharge capacity of 266.0 mAh g−1 at 0.1C, a remarkable rate capability of 159.1 mAh g−1 at 5C and an extremely high capacity retention of 98.5% over 200 cycles at 0.5C with a small voltage drop. [ABSTRACT FROM AUTHOR]

We prepared the Cr-doped Li-rich cathodes coated by Li 3 PO 4 with stable capacity and median voltage for lithium-ion batteries. Lithium-rich layered oxides exhibit one of the highest reversible discharge capacities among cathode materials for lithium-ion batteries. However, their voltage decay and poor cycle stability severely restrict their use as a commercial cathode material. In this work, a novel approach of that combines Cr doping and a Li 3 PO 4 coating was designed to address the problems associated with lithium-rich Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 materials. The synergistic method not only increases the discharge capacity and cycle stability but also decreases the voltage decay. The 1.0 wt% Li 3 PO 4 coating and 0.08 Cr doping on Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 cathode shows a capacity retention of 76.5% compared to the 59.0% capacity retention for the pristine electrode after 200 cycles. The initial discharge capacity is also increased from 255.8 mAh·g−1 to 265.2 mAh·g−1. In addition, the discharge voltage decay decreases from 0.84 V to 0.39 V after 200 cycles as a result of the Cr doping and Li 3 PO 4 coating. These enhanced electrochemical properties are attributed to the fact that the Cr doping stabilized the layered structure and inhibited its phase transformation to the spinel phase, and the Li 3 PO 4 coating confined the interfacial side reactions between the electrode and electrolyte. This work may provide a new method to solve the subsistent problems of lithium-rich cathode materials. [ABSTRACT FROM AUTHOR]

We prepared nonstoichiometric Li-rich cathodes with stable capacity and median voltage for lithium-ion batteries. • The nonstoichiometry of Li-rich cathodes were firstly synthesized for lithium-ion batteries. • The nonstoichiometric cathodes exhibit stable capacity and median voltage upon cycling. • The improvement of cycling ability attributes to the production of Ni3+ ions in the nonstoichiometric samples. Lithium-rich layered oxides are considered as promising cathode materials for lithium-ion batteries due to its high capacity, but the rapid decay of capacity and operating voltage are great challenges to achieve its commercial application. In this work, the nonstoichiometry of Li-rich layered oxide Li 1.2 Mn 0.6 Ni 0.2 O 2 was designed by directly declining the Mn amounts in the form of Li 1.2 Mn x Ni 0.2 O 2 (x = 0.59, 0.57, 0.55). The nonstoichiometric sample Li 1.2 Mn 0.55 Ni 0.2 O 2 exhibits a capacity of 170.73 mAh g−1 at 0.5 C, a little lower than 187.29 mAh g−1 of Li 1.2 Mn 0.6 Ni 0.2 O 2 , however, better cycling stability of operating voltage and capacity is attained with the reduction of Mn amounts, compared to that of Li 1.2 Mn 0.6 Ni 0.2 O 2. The capacity retention of Li 1.2 Mn 0.55 Ni 0.2 O 2 is enhanced to 88.7% via 74.7% of Li 1.2 Mn 0.6 Ni 0.2 O 2 after 100 cycles at 0.5 C. The declining value of operating voltage for Li 1.2 Mn 0.55 Ni 0.2 O 2 is 0.200 V as compared to 0.559 V for Li 1.2 Mn 0.6 Ni 0.2 O 2. X-ray photoelectron spectra (XPS) was employed to confirm the existence of Ni3+ in the nonstoichiometric samples, and the amounts of Ni3+ increase along the Mn contents decrease. The improvement of electrochemical properties for nonstoichiometric samples is attributed to the presence of Ni3+ due to Ni3+ can defer the transition of layered-to-spinel structure through decreasing the Li/Ni mixing. [ABSTRACT FROM AUTHOR]

Abstract Potassium-ion batteries (KIBs) are regarded as potentially promising large-scale energy storage (EES) systems due to the close redox potential to lithium, the rich reserve and low cost of potassium resources. Nevertheless, the larger ionic radius of K-ion makes cathode materials for KIBs be a difficult issue. Herein, we construct Mn-based layered oxide (K 0.32 MnO 2) microsphere, self-assembled by ultrathin nanosheets, as potential cathode electrode for nonaqueous KIBs, which delivers a reversible discharge capacity of 95.1 mAh·g−1 at 10 mA g−1. It is demonstrated that K 0.32 MnO 2 undergoes a simple solid solution reaction mechanism for K-ions deintercalation/intercalation during the initial charge-discharge process, which is not like complex multiple processes accompanied by phase transition for Mn-based layered oxide particles. Ex situ measurements reveal that K 0.32 MnO 2 nanosheets can provide outstanding morphology and structure stability, as well as fast electrochemical kinetics upon cycling, thus high rate capacity, improved cycling lifetime and voltage stability at low and high rates can be obtained. We also verify the practical feasibility of K-ion full cell with commercial super P carbon black anode. This novel work illuminates the electrochemical mechanism for K-ions storage in depth, which may push the study on layered oxide cathodes and accelerate the development of KIBs. Graphical abstract Image 1 Highlights • Mn-based layered oxide nanosheet was synthesized via a facile hydrothermal method. • Mn-based layered oxide nanosheet exhibits superior electrochemical performances. • The mechanism of K-ions extraction/insertion is analyzed in depth. • The improved properties are due to highly morphology and structural stability. [ABSTRACT FROM AUTHOR]

Serious decay of capacity and voltage for Li-rich layered cathode materials restrict their commercial application for Li-ion batteries. In this paper, a spherical core-shell structure, Li 1.2 Ni 0.2 Mn 0.6 O 2 @Li 1.2 Ni 0.4 Mn 0.4 O 2 was in-situ prepared using hydrothermal method. SEM images as well as the analysis with XPS and EDS verified that the core-shell structure grows well. Electrochemical properties showed that the merits of the both materials have been preserved for high capacity of core material and high voltage as well as superior cycling stability of shell material. C/S-1/1 sample, whose mass proportion of core to shell is 1:1, exhibits the initial discharge capacity of 218 mAh·g −1 with the highest operating voltage of 3.763 V at 0.1C between 2.0 and 4.8 V, splendid cycling stability with the capacity retention of 93.1% and high voltage retention value of 3.335 V after 100 cycles. The improvement of electrochemical performances are attributed to the stable Li 1.2 Ni 0.4 Mn 0.4 O 2 protective shell, which is beneficial to improve the electrochemical kinetics, mitigate the morphology evolution and retard the layered-spinel phase transition by restraining the release of O 2 and weakening the electrode-electrolyte interfacial reaction. [ABSTRACT FROM AUTHOR]

Li-rich layered oxides have been regarded as valuable cathode materials for high energy density lithium-ion batteries. However, high initial irreversible capacity, bad rate capability, as well as serious capacity fading and voltage decay hinder their commercial application. In this paper, a nano CoF 2 protective layer is coated on the surface of Li 1.2 Ni 0.2 Mn 0.6 O 2 via a facial wet chemistry method. A high initial discharge capacity of 264.4 mAh g −1 is obtained for 0.5% CoF 2 -coated sample and 259.1 mAh g −1 for 1% CoF 2 -coated sample owing to the suppression of irreversible release of O 2 and the contribution of electrochemical conversion of CoF 2 /LiF. Furthermore, 1% CoF 2 -coated sample exhibits the excellent rate capability of 167.5 mAh g −1 at 5 C rate, the superior cycling stability with the capacity retention of 241.0 mAh g −1 and the ameliorative voltage drop of 0.312 V at 0.1C after 100 cycles. The enhanced rate performance as well as stability of capacity and voltage can be attributed to the nano coatings which inhibit the electrolyte-electrode side reaction, enhance the electrochemical kinetics and mitigate structure transition from layered to spinel phase. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ce-doped MnO 2 was prepared by the potentiostatic electrodeposition strategy. • The assembled flexible Zn//Ce-MnO 2 @CC battery exhibits long cycle-life. • The doped cerium ions could stabilize the structure of the cathode materials. • A H+/Zn2+ co-insertion mechanism of the Mn-based oxides cathode was demonstrated. With the development of flexible electronic devices, power sources' higher safety, lighter, and bending ability have been demanded in recent years. While, aqueous zinc-ion batteries (ZIBs) have gained much attention due to their low cost, rich zinc resources, and high safety. Hence, they have been considered the most promising secondary battery in the near future. However, the practical application of aqueous ZIBs is still impeded by the unsatisfied performance of the cathode materials and the complex manufacturing process. Moreover, the electrochemical energy storage process and mechanism of the cathodes at the flexible ZIBs still remain ambiguous and under discussion, which severely limited the development of the ZIBs. Herein, a Ce doped-MnO 2 binder-free cathode electrode was prepared via a one-step potentiostatic electrodeposition strategy. A flexible ZIB assembled based on the Ce-MnO 2 @CC cathode and a homemade gel electrolyte exhibits a high reversible specific capacity (∼311 mAh g−1), a significant energy density (370 Wh kg−1), an excellent stability performance, and achieves good electrochemical behavior even under different bending conditions. Furthermore, the energy storage mechanism of the flexible ZIBs with Mn-based oxides cathode was monitored by the in-situ Raman, XRD, SEM, and TEM, revealing the reversible insertion/extraction of Zn2+ and H+ during the charge/discharge process. Moreover, the results also demonstrate that the structural shedding, and dissolution of the MnO 2 structure are the major factors in reducing capacity. This research opens up new opportunities for flexible ZIBs in the field of portable and wearable electronics. [ABSTRACT FROM AUTHOR]

Abstract: Direct methanol fuel cells (DMFCs) confront with the problems of the high costs of both polymer electrolyte membrane (PEM) and noble metal catalysts. Especially, the PEM has a shortcoming of methanol crossover through it, which lowers the power density of cells and makes cathode catalysts poisoned. In this paper, a new structured alkaline DMFC is presented, which makes a great progress in solving the problems. In this DMFC, PEM is replaced by a polymer fiber membrane (PFM) which shows very low resistance to ions motion in electrolyte and is very inexpensive. MnO2 and PtRu/C have been used as cathode and anode catalysts respectively. The peak power densities of 27.3mWcm−2 and 108.4mWcm−2 have been achieved at 20°C and 68°C respectively, which are around 2–10 times higher than that of published similar researches. The experimental results demonstrate that MnO2 shows not only good electro-catalytic activity and stability for oxygen reduction reaction in alkaline solutions, but also an excellent tolerance to methanol. [Copyright &y& Elsevier]

Abstract: LaNi0.9Ru0.1O3 as cathode catalyst for a direct borohydride fuel cell (DBFC) was synthesized and investigated for the first time. The electrochemical experiments indicated that perovskite-type oxide LaNi0.9Ru0.1O3 exhibited higher electrochemical performance compared with LaNiO3, which suggested incorporation of element Ru into LaNiO3 could further improve the catalytic ability for oxygen reduction reaction (ORR) in alkaline solution. LaNi0.9Ru0.1O3 catalyst was found to have good tolerance of BH4 −. Meanwhile the maximum power density of 171mWcm−2 was obtained at 65°C without using any precious ion exchange membrane. A life test indicated that the DBFC displayed no significant degradation for about 70h testing. The electrochemical data suggested that LaNi0.9Ru0.1O3, which provided a simple way to construct DBFCs without using any ion exchange membrane, might be promising cathode catalyst with high performance and low cost for DBFCs. [Copyright &y& Elsevier]

Abstract: A perovskite-type oxide LaNi0.8Co0.2O3 is prepared as a direct borohydride fuel cell (DBFC) cathode catalyst. Its electrochemical properties are studied by cyclic voltammetry. The results demonstrate that LaNi0.8Co0.2O3 exhibits excellent electrochemical activity with respect to the oxygen reduction reaction (ORR) and good tolerance of BH4 − ions. Maximum power densities of 114.5mWcm−2 at 30°C and 151.3mWcm−2 at 62°C are obtained, and good stability (300-h stable performance at 20mAcm−2) is also exhibited, which shows that such perovskite-type oxides as LaNi0.8Co0.2O3 can be excellent catalysts for DBFCs. [Copyright &y& Elsevier]

Abstract: In this paper, the perovskite-type oxide LaCoO3 was studied as a cathode catalyst for use in a direct borohydride fuel cell (DBFC). The experimental results demonstrated that the LaCoO3-catalysed cathode not only shows good electrocatalytic activity for oxygen reduction in alkaline solutions, but also shows good resistance to poisoning from BH4 − ions originating from the fuel during discharge performance. Based on this new type of catalyst, a membraneless fuel cell was designed with a hydrogen storage alloy used as the anode catalyst. The maximal current density of 220mAcm−2 and power density of 65mWcm−2 were obtained at ambient conditions. [Copyright &y& Elsevier]