Carbon nanotube/Co3O4 composite for air electrode of lithium-air battery

A carbon nanotube [CNT]/Co3O4 composite is introduced as a catalyst for the air electrode of lithium-air [Li/air] batteries. Co3O4 nanoparticles are successfully attached to the sidewall of the CNT by a hydrothermal method. A high discharge capacity and a low overvoltage indicate that the CNT/Co3O4 composite is a very promising catalyst for the air electrode of Li/air batteries

Hierarchical urchin-shaped alpha-MnO2 on graphene-coated carbon microfibers: a binder-free electrode for rechargeable aqueous Na-air battery

With the increasing demand of cost-effective and high-energy devices, sodium-air (Na-air) batteries have attracted immense interest due to the natural abundance of sodium in contrast to lithium. In particular, an aqueous Na-air battery has fundamental advantage over non-aqueous batteries due to the formation of highly water-soluble discharge product, which improve the overall performance of the system in terms of energy density, cyclic stability and round-trip efficiency. Despite these advantages, the rechargeability of aqueous Na-air batteries has not yet been demonstrated when using non-precious metal catalysts. In this work, we rationally synthesized a binder-free and robust electrode by directly growing urchin-shaped MnO2 nanowires on porous reduced graphene oxide-coated carbon microfiber (MGC) mats and fabricated an aqueous Na-air cell using the MGC as an air electrode to demonstrate the rechargeability of an aqueous Na-air battery. The fabricated aqueous Na-air cell exhibited excellent rechargeability and rate capability with a low overpotential gap (0.7 V) and high round-trip efficiency (81%). We believe that our approach opens a new avenue for synthesizing robust and binder-free electrodes that can be utilized to build not only metal-air batteries but also other energy systems such as supercapacitors, metal-ion batteries and fuel cells.ope

Reactivity of transition metal (Co, Ni, Cu) sulphides versus lithium: The intriguing case of the copper sulphide

Transmission electron microscopy (TEM), in situ X-ray diffraction (XRD) and electrochemical techniques have been used to study the electrochemical reactivity of transition metal (cobalt, nickel, and copper) sulphides. We show that cobalt and nickel sulphides react versus lithium through conversion reactions similarly to their homologous oxides with during the discharge step the formation of metallic nano-particles embedded in Li2S that on the following charge convert back into sulphides. In contrast, the electrochemical reactivity of CuS towards Li was shown to follow a displacement reaction leading to the growth and disappearance of large copper dendrites with a concomitant reversible decomposition/re-crystallization of the initial electrode material. We show from structural considerations that this mechanism is nested in the creation of Cu2-xS phases, since intermediary phases during cycling have both high copper mobility and a sulphur network close to that of Li2S. In spite of their attractive capacity, none of these compounds show good capacity retention over the studied voltage range (0 to 2.5 V); the main reason being rooted in the partial solubility of Li2S into the electrolyte. © 2006 Elsevier SAS. All rights reserved

A Transmission Electron Microscopy Study of the Reactivity Mechanism of Tailor-Made CuO Particles toward Lithium

The electrochemical reactivity of tailor-made CuO powders prepared according to a new low-temperature synthesis method was studied by a combination of transmission electron microscopy (TEM) and electrochemical techniques. All the processes involved during cycling were successfully identified. We show that the reduction mechanism of CuO hy lithium involves the formation of a solid solution of CuII1-xCuIxO1-x/2 0 ≤ x ≤ 0.4, a phase transition into Cu2O, then the formation of Cu nanograins dispersed into a lithia matrix (Li2O) followed by the growth of an organic-type coating. This one is responsible for the extra capacity observed on the voltage vs. composition curve. During the subsequent charge, the organic layer vanishes first, and then the Cu grains are partially or fully oxidized with a concomitant decomposition of Li2O. The formation of Li2O and Cu nanograins and then the one of Cu, CuO, and Cu2O nanograins on the first discharge and subsequent charge, respectively, were identified by high-resolution TEM studies. These results enabled a better understanding of the processes governing the reactivity of 3d metal oxides rv. lithium down to 0.02 V. © 2001 The Electrochemical Society. All rights reserved

Study of the reactivity mechanism of M3B2O 6 (with M = Co, Ni, and Cu) toward lithium

The electrochemical reactivity mechanism of M3B 2O6 (with M = Co, Ni, and Cu) powders toward lithium was studied by a combination of transmission electron microscopy (TEM), infrared spectroscopy (IR), 11B magic angle spinning nuclear magnetic resonance (MAS NMR), and electrochemical techniques. The electrochemical properties of these materials as anodes for lithium batteries were investigated and found to be similar to those of 3d-metal oxides. In fact, the reduction process of 3d-metal borates involves their decomposition in metal nanograins dispersed into a lithia matrix surrounded by an organic layer responsible for the observed extra capacity. The lithia matrix consists of a mixture of lithium oxide (Li2O) and lithium orthoborate (Li3BO3). During the subsequent charge, the organic layer vanishes and the metal grains are partially or fully oxidized with the concomitant decomposition of Li 2O. The formation of Li2O and metal nanograins during the discharge, as well as that of oxides nanograins during the following charge, were identified by HRTEM studies while Li3BO3 was detected by IR spectroscopy and 11B MAS NMR techniques

Electrochemical Impedance Spectroscopy response study of a commercial graphite-based negative electrode for Li-ion batteries as function of the cell state of charge and ageing

International audienceThe successful development of electrified vehicles is a key factor in the transition to a moreenvironmentally friendly transportation sector. Li-ion batteries, which are today’s choice to powerelectrified vehicles, have to fulfill more stringent requirements in terms of ageing and need advancedtools to study the interfaces evolution upon cycling. This work is thus focused on understanding theimpedance behavior of a commercial graphite-based negative electrode, which is used in a Li-ion batterydesigned for such vehicles. 3-electrode pouch cells were assembled with such negative electrode, a LMOlayeredoxide-based positive electrode, a Celgard1type separator soaked with a carbonate solvents-LiPF6mixture electrolyte and a LTO-based electrode as reference. Electrochemical Impedance Spectroscopymeasurements were performed at different cell states of charge and ageing times. The impedance of thegraphite-based anode is analyzed forfirst time with de Levie’s equation for porous electrodes. Theanalysis is supported by designed SEI layer formation experiments with vinylene carbonate and vinyleneethyl carbonate additives. The high frequency domain of the interfacial kinetic loop reflects porosityeffects and the graphite particles–composite matrix electric tranfer. The SEI layer and charge transferphenomena are reflected in the medium and medium to low frequency domains respectively, and theirimpedance contributions depend on the Li content of the graphite particles. Upon ageing, the interfacialimpedance of the graphite-based electrode should increase due to SEI layer growing. However, from 100%to 80% of battery capacity retention, the impedance decreases. Our analysis backed by post-mortemcharacterizations allows to assign this unexpected behavior to porosity rise and slight Mn-contaminationof the SEI layer

A mechanism study of M3B2O6 (with M = Co, Ni and Cu) towards Li

The electrochemical reactivity mechanism of M3B 2O6 (with M = Co, Ni and Cu) powders towards Li was studied by a combination of Transmission Electron Microscopy (TEM), infrared spectroscopy (IR), 11B Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR). The electrochemical properties of these materials as anode for Li batteries were investigated, and found to be similar to those of 3d-metal oxides. In fact, the reduction process of 3d-metal borates involves their decomposition in metal nanograins dispersed into a lithia matrix surrounded by an organic layer responsible for the observed extra capacity. The lithia matrix consists of a mixture of lithium oxide (Li2O) and lithium orthoborate (Li3BO3). During the subsequent charge, the organic layer vanishes and the metal grains are partially or fully oxidized with the concomitant decomposition of Li2O