An optimization of the specific capacity exhibited by the best layered lithiated cobalt nitride Li2.20Co0.40N is proposed by using a conditioning electrochemical oxidation up to 1.1V before cycling in the 1.1V–0.02V potential range. This initial charge process allows the Co3+/Co2+ redox couple to be involved in the cycling process in addition to the Co2+/Co+ couple as in the 1V–0.02V voltage range. A new electrochemical fingerprint is obtained with a single step at 0.4/0.8V for the discharge-charge process and a specific capacity of 300mAhg−1 at C/5 which constitutes a huge improvement compared to 130mAhg−1 recovered in the conventional 1V–0.02V potential window. This high capacity value and the excellent capacity retention of 100% over at least 75 cycles make Li2.20Co0.40N a promising anode material for Li-ion batteries.

Electrochemical capacitors that can store high density of electrical energy with fast power delivering and long operating life time are important for many challenging applications. Tremendous research efforts aim at developing electrodes which gather the advantages of both electrochemical double layer capacitors (high power density, long cycling life) and pseudo-capacitors (high energy density). Here we highlight the design of hierarchically composite electrodes consisting of porous and nanostructured TiN grown on vertically aligned CNTs as high-performance electrode for micro-supercapacitors. The electrodes, which are deposited on silicon substrates, exhibit an areal capacitance as high as 18.3mFcm−2 at 1Vs−1 that can be further enhanced by increasing the TiN layer thickness. Furthermore, this capacitance is maintained over 20,000 cycles. We propose that such high performance originates from the high surface area of the electrodes having a nanoporous structure, as well as to their specific surface chemistry, which contains large amount of oxygen vacancies as a result of nitrogen self-doping of anatase which forms at the TiN surface.

TiOxNy and VOxNy powders have been synthesized using oxide precursors and a conventional nitridation method. It enables to control of oxygen content and surface area. The electrochemical performances of the different powders have been investigated. A strong dependence on the surface area as well as on the nature of the oxynitride has been found. A typical value of 300μFcm−2 has been determined for VOxNy powders, while TiOxNy powders only show 50μFcm−2. In this last case it is believed that only double layer capacitance or weak redox reactions participate in charge storage mechanism while for vanadium based oxynitrides, a thin layer below the surface (≈4Å) is involved in charge storage via faradic reactions. VOxNy electrodes can be operated in different aqueous electrolytes, but only double layer capacitance is measured in neutral electrolytes. The highest capacitance values (≈80Fg−1) are measured in KOH and fair cycling ability is achieved when the electrochemical window is limited, thus avoiding oxidative potentials.

Herein, the novel concept of a solid‐state electrode materials with ionic‐liquid (IL) properties is presented. These composite materials are a mixture of electroactive matter, an electronic conductor, a solid‐state ionic conductor and a polymeric binder. The approach of a solid‐state ionic conductor combines the high safety of an IL with the nanoconfinement of such a liquid in a mesoporous silica framework, an ionogel, thus leading to a solid with liquid‐like ionic properties. The same ionic conductor is also used as a solid‐state separator to evaluate the properties of our solid‐state electrode materials in all‐solid‐state batteries. Such a concept of a solid‐state electrode material contributes to addressing the challenge of energy storage, which is one of the major challenges of the 21st century. The ionogel, along with its processability, allows a single‐step preparation of the assembly of the solid‐state electrode and solid‐electrolyte separator and can be applied without specific adaptation to present, thick electrodes prepared by the widespread tape‐casting technique. The filling of the electrode porosity by an ionogel is shown by elemental mapping using scanning electron microscopy, and is subsequently confirmed by electrochemical measurements. The ionogel approach is successfully applied without specific adaptation to two state‐of‐the‐art, positive electroactive materials developed for future‐generation lithium‐ion batteries, namely LiFePO4 and LiNi1/3Mn1/3Co1/3O2.

Easy immobilisation of carbon nanofillers in a solid state device featuring mesopores filled with ionic liquid (IL) is presented. Such a route allows a good dispersion of carbon nanotubes (CNTs) and carbon fibers in N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, subsequently followed by the confinement of the whole within a porous silica matrix. We thus obtain herein a new type of hybrid ionogel within a solid device containing a percolating IL network as its real liquid state, as well as presenting a percolating carbon network. The process is carried out within a single step, without any chemistry for covalent grafting. We show that an IL with a non π-conjugated cation allows good dispersion of the carbon nanotubes, with a subsequent percolation for a loading level lower than 3.6 wt%. Together with the dynamic IL properties of ionogels, we thus present herein an inorganic-solid host containing carbon nanofillers, which gives the solid device ionic and electronic conductivities.

We report a systematic study of the layered lithium nitridocuprates Li3−xCuxN with 0.1≤x≤0.39. The structural data obtained from experimental XRD patterns, Rietveld refinements and unit cell parameters calculation vs x, indicate that copper (I) substitute interlayer lithium ions in the parent nitride Li3N to form the Li3−xCuxN compound without any Li vacancy in the Li2N− layer. Electrochemical results report Li insertion into the corresponding layered structures cannot take place in the 1.2/0.02 V voltage range as in the case of lithium into nitridonickelates and nitridocobaltates. However, in the initial charge process of Li3−xCuxN at 1.4 V leading to a specific capacity higher than 1000 mA h/g, the oxidation of copper and nitride ions is probably involved inducing a strong structural disordering process. As a consequence a new rechargeable electrochemical system characterized by discharge–charge potential of ≈0.3 V/1.2 V appears from the second cycle. Cycling experiments 0.02 V voltage/0.02 V range induce a complete destruction of the layered host lattice and the presence of Cu3N in the charge state suggests a conversion reaction. The capacity recovered in the 1.4/0.02 V range practically stabilizes around 500 mA h/g after 20 cycles.

New lithium nickel nitrides Li3−2xNixN (0.20≤x≤ 0.60) have been prepared and investigated as negative electrode in the 0.85/0.02V potential window. These materials are prepared from a Ni/Li3N mixture at 700°C under a nitrogen flow. Their structural characteristics as well as their electrochemical behaviour are investigated as a function of the nickel content. For the first time are reported here the electrochemical properties of a lithium intercalation compound based on a layered nitride structure. The Li3−2xNixN compounds can be reversibly reduced and oxidized around 0.5V versus Li/Li+ leading to specific capacities in the range 120–160mAh/g depending on the nickel content and the C rate. Due to a large number of lithium vacancies, the structural stability provides an excellent capacity retention of the specific capacity upon cycling.

We report the first example of an intercalation compound based on the nitrogen framework in which lithium can be intercalated and deintercalated. A comparison of the structural and electrochemical properties of the ternary lithium cobalt, nickel and copper nitrides is performed. Vacancy layered structures of ternary lithium nitridocobaltates Li3−2xCoxN and nitridonickelates Li3−2xNixN with 0.10⩽x⩽0.44 and 0.20⩽x⩽0.60, respectively, are proved to reversibly intercalate Li ions in the 1V–0.02V potential range. These host lattices can accommodate up to 0.35 Li ion par mole of nitride. Results herein obtained support Li insertion in vacancies located in Li2N− layers while interlayer divalent cobalt and nickel cations are reduced to monovalent species. No structural strain is induced by the insertion–extraction electrochemical reaction which explains the high stability of the capacity in both cases. For the Li1.86Ni0.57N compound, a stable faradaic yield of 0.30F/mol, i.e. 130mAh/g, is maintained at least for 100 cycles. Conversely, the ternary copper nitrides corresponding to the chemical composition Li3−xCuxN with 0.10⩽x⩽0.40 do not allow the insertion reaction to take place due to the presence of monovalent copper combined with the lack of vacancies to accommodate Li ions. In the latter case, the discharge of the lithium copper nitrides is not reversible.