Rechargeable aqueous Zn-ion batteries are attractive cheap, safe and green energy storage technologies but are bottlenecked by limitation in high-capacity cathode and compatible electrolyte to achieve satisfactory cyclability. Here we report the application of nonstoichiometric ZnMn2O4/carbon composite as a new Zn-insertion cathode material in aqueous Zn(CF3SO3)2 electrolyte. In 3 M Zn(CF3SO3)2 solution that enables ∼100% Zn plating/stripping efficiency with long-term stability and suppresses Mn dissolution, the spinel/carbon hybrid exhibits a reversible capacity of 150 mAh g–1 and a capacity retention of 94% over 500 cycles at a high rate of 500 mA g–1. The remarkable electrode performance results from the facile charge transfer and Zn insertion in the structurally robust spinel featuring small particle size and abundant cation vacancies, as evidenced by combined electrochemical measurements, XRD, Raman, synchrotron X-ray absorption spectroscopy, FTIR, and NMR analysis. The results would enlighten and pr...

Cation-Deficient Spinel ZnMn2O4 Cathode in Zn(CF3SO3)2 Electrolyte for Rechargeable Aqueous Zn-Ion Battery.

With the increasing importance of wireless microelectronic devices the need for on-board power supplies is evidently also increasing. Possible candidates for microenergy storage devices are planar all-solid-state Li-ion microbatteries, which are currently under development by several start-up companies. However, to increase the energy density of these microbatteries further and to ensure a high power delivery, three-dimensional (3D) designs are essential. Therefore, several concepts have been proposed for the design of 3D microbatteries and these are reviewed. In addition, an overview is given of the various electrode and electrolyte materials that are suitable for 3D all-solid-state microbatteries. Furthermore, methods are presented to produce films of these materials on a nano- and microscale.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/aenm.201000002

All-Solid-State Lithium-Ion Microbatteries: A Review of Various Three-Dimensional Concepts

Manganese dioxide compounds with various structures were synthesized and tested as "bulk" composite electrodes for electrochemical capacitors. The capacitance of the set of MnO 2 compounds having Brunauer-Emmett-Teller (BET) surface areas larger than 125 in 2 g -1 reached a maximum value of about 150 F g -1 . The capacitance of all amorphous compounds (except one) is due to faradaic processes localized at the surface and subsurface regions of the electrode. Further increasing the surface area does not provide additional capacitance. The capacitance of the crystallized materials is clearly dependent upon the crystalline structure, especially with the size of the tunnels able to provide limited cations intercalation. Thus, the 2D structure of birnessite materials gives an advantage to obtain relatively high capacitance values (110 F g -1 ) considering their moderate BET surface area (17 m 2 g -1 ). ID tunnel structure such as γ or β-MnO 2 is characterized by only a pseudofaradic surface capacitance and therefore relies on the BET surface area of the crystalline materials. 3D tunnel structure such as λ-MnO 2 shows some intermediate behavior between bimessite and ID tunnel structures.

Crystalline MnO2 as Possible Alternatives to Amorphous Compounds in Electrochemical Supercapacitors

4.3. Manganese Oxide-Based Compounds 1291 4.3.1. MnO2-Type Compounds 1291 4.3.2. Ternary Lithiated LixMnOy Compounds 1293 4.4. Vanadium Pentoxide V2O5 1298 4.4.1. V2O5 Structure 1298 4.4.2. LixV2O5 Bulk Phases 1300 4.4.3. LixV2O5 Crystallized Thin Films 1303 4.5. Titanium Oxide-Based Compounds 1305 4.5.1. Lithium Titanate Li4Ti5O12 1306 4.5.2. TiO2 Anatase 1308 5. Phospho-olivine LiFePO4 Compound 1312 6. General Conclusion 1314 7. Acknowledgments 1315 8. References 1315

Raman Microspectrometry Applied to the Study of Electrode Materials for Lithium Batteries

In this paper, we wish to present an overview of the research carried out in our laboratories with low-cost transition metal oxides (manganese dioxide, iron oxide and vanadium oxide) as active electrode materials for aqueous electrochemical supercapacitors. More specifically, the paper focuses on the approaches that have been used to increase the capacitance of the metal oxides and the cell voltage of the supercapacitor. It is shown that the cell voltage of an electrochemical supercapacitor can be increased significantly with the use of hybrid systems. The most relevant associations are Fe3O4 or activated carbon as the negative electrode and MnO2 as the positive. The cell voltage of the Fe3O4/MnO2 device is 1.8 V and this value was increased to 2.2 V by using activated carbon instead of Fe3O4. These two systems have shown superior behavior compared to a symmetric MnO2/MnO2 device which only works within a 1 V potential window in aqueous K2SO4. Furthermore, the activated carbon/MnO2 hybrid device exhibits a real power density of 605 W/kg (maximum power density =19.0 kW/kg) with an energy density of 17.3 Wh/kg. These values compete well with those of standard electrochemical double layer capacitors working in organic electrolytes.

Nanostructured transition metal oxides for aqueous hybrid electrochemical supercapacitors

Electrochemical properties of low temperature (LT) crystallized are investigated. LT was obtained by a precipitation process in aqueous solution and a final heat‐treatment at 400°C in air. Potentiometric, voltammetric, and ac impedance experiments are performed as well as x‐ray diffraction measurements on electrochemically delithiated compounds. LT shows electrochemical and structural properties quite different from that exhibited by the high temperature (HT) . The main differences appear in terms of practical voltage, reversibility, Li transport in oxide, and structural changes as Li is deintercalated. This work clearly proves the 3D character of LT (spinel‐like structure). In spite of a lower working potential and a satisfactory capacity (Δx = 0.5), the LT is highly reactive toward the electrolyte and is characterized by a slower Li transport than in layered HT .

https://iopscience.iop.org/article/10.1149/1.1837569/pdf

Electrochemical Properties of Low Temperature Crystallized LiCoO2

Electrochemical lithium insertion in sol-gel crystalline vanadium pentoxide thin films

Synthesis, structural and electrochemical characterizations of the sol–gel birnessite MnO1.84·0.6H2O

Cation-deficient mixed oxides, Mn–Co, Mn–Fe and Co–Fe, with the spinel structure have been synthesized by a solution technique. Preliminary results on electrochemical Li insertion into these compounds are discussed in relation to their structural and chemical characteristics, and emphasize the strong effect of cation vacancies on their electrochemical properties. The best results were obtained with the Mn–Co system.

J. Farcy

Papers

Electrochemical Properties of Low Temperature Crystallized LiCoO2

Electrochemical lithium insertion in sol-gel crystalline vanadium pentoxide thin films

Synthesis, structural and electrochemical characterizations of the sol–gel birnessite MnO1.84·0.6H2O

Low-temperature mixed spinel oxides as lithium insertion compounds

Low-temperature cobalt oxide as rechargeable cathodic material for lithium batteries