Olivier Crosnier

TiO2(B) nanoribbons as negative electrode material for lithium ion batteries with high rate performance.

Nanosized TiO(2)(B) has been investigated as a possible candidate to replace Li(4)Ti(5)O(12) or graphite as the negative electrode for a Li-ion battery. Nanoribbon precursors, classically synthesized in autogenous conditions at temperatures higher than 170 °C in alkaline medium, have been obtained, under reflux (T ∼ 120 °C, P = 1 bar). After ionic exchange, these nanoribbons exhibit a surface area of 140 m(2) g(-1), larger than those obtained under autogenous conditions or by solid state chemistry. These nanoparticles transform after annealing to isomorphic titanium dioxide. They mainly crystallize as the TiO(2)(B) variety with only 5% of anatase. This quantification of the anatase/TiO(2)(B) ratio was deduced from Raman spectroscopy measurement. TEM analysis highlights the excellent crystallinity of the nanosized TiO(2)(B), crystallizing as 6 nm thin nanoribbons. These characteristics are essential in lithium batteries for a fast lithium ion solid state diffusion into the active material. In lithium batteries, the TiO(2)(B) nanoribbons exhibit a good capacity and an excellent rate capability (reversible capacity of 200 mA h g(-1) at C/3 rate (111 mA g(-1)), 100 mA h g(-1) at 15C rate (5030 mA g(-1)) for a 50% carbon black loaded electrode). The electrode formulation study highlights the importance of the electronic and ionic connection around the active particles. The cycleability of the nano-TiO(2)(B) is another interesting point with a capacity loss of 5% only, over 500 cycles at 3C.

Doping of Cobalt into Multilayered Manganese Oxide for Improved Pseudocapacitive Properties

Anodic electrodeposition of layered manganese oxides has been carried out in a MnSO 4 solution heated at various bath temperatures from 25 to 80°C. The crystallinity of the deposits increased with an increase in the bath temperature. Although Co 2+ ions were not involved in the deposition reaction at room temperature, at the elevated temperature the addition of Co 2+ gave rise to a catalytic current suggesting the formation of Co/Mn mixed oxide. No new X-ray diffraction peaks appeared with the insertion of Co 2+ ions in the structure, but their addition caused broadening of the peaks due to the Mn dioxide phase. This indicates that Co ions are not accommodated in the interlayer space but are well dispersed within the MnO 2 layers composed of edge-shared Mn0 6 octahedra. The Co-doped Mn oxide film thus obtained exhibited much better pseudocapacitive performance than the undoped counterpart.

Advanced oxide and metal powders for negative electrodes in lithium-ion batteries

Abstract In this study, tin dioxide, tin and bismuth have been envisioned as possible candidate to replace graphite negative electrodes in Li-ion batteries. Tin dioxide thin films and nanoscaled tin and bismuth powders have been synthesized by different techniques. Their electrochemical behaviors have been compared to electrodes made with standard commercially available powders. In all cases, nanoscaled materials have shown enhanced electrochemical properties compared to standard powders. SnO 2 thin films exhibit a longer cycle life than tin dioxide powder. The capacities measured on both bismuth and tin nanoscaled materials were more important than for the same electrodes prepared by commercially available powders. Moreover, the values are close to those expected from the theoretical reactions. However, the cycling life of tin or bismuth electrodes is still the weak point of these systems. Subsequently, an optimized matrix is required in order to prevent capacity loss upon cycling.

Lithium rhenium(VII) oxide as a novel material for graphite pre-lithiation in high performance lithium-ion capacitors

The electrochemical reversibility of lithium extraction from lithium rhenium oxide (Li5ReO6, LReO) has been studied using standard 1 mol L−1 LiPF6 in EC/DMC electrolyte. An irreversible capacity of 410 mA h g−1 was observed below 4.3 V vs. Li/Li+ (close to the total theoretical capacity of 423 mA h g−1). Owing to this huge irreversible capacity, LReO could be included as a sacrificial material in the positive activated carbon electrode of a lithium-ion capacitor (LIC) to be used for pre-lithiating the graphite negative electrode. After the pre-lithiation step, the hybrid lithium-ion capacitor constituted of Li doped graphite and activated carbon as negative and positive electrodes, respectively, was cycled at current densities from 0.25 A g−1 to 0.65 A g−1. The LIC system demonstrated excellent capacitance stability up to 5000 cycles in the voltage range 2.2–4.1 V. The energy and power densities calculated per total mass of both electrodes reached 40 W h kg−1 and 0.5 kW kg−1, respectively. Hence, by using LReO, the prelithiation of graphite can be considerably simplified in comparison to traditional LIC systems, while enabling safer operating conditions owing to the absence of metallic lithium.

Safe and recyclable lithium-ion capacitors using sacrificial organic lithium salt

Lithium-ion capacitors (LICs) shrewdly combine a lithium-ion battery negative electrode capable of reversibly intercalating lithium cations, namely graphite, together with an electrical double-layer positive electrode, namely activated carbon. However, the beauty of this concept is marred by the lack of a lithium-cation source in the device, thus requiring a specific preliminary charging step. The strategies devised thus far in an attempt to rectify this issue all present drawbacks. Our research uncovers a unique approach based on the use of a lithiated organic material, namely 3,4-dihydroxybenzonitrile dilithium salt. This compound can irreversibly provide lithium cations to the graphite electrode during an initial operando charging step without any negative effects with respect to further operation of the LIC. This method not only restores the low CO2 footprint of LICs, but also possesses far-reaching potential with respect to designing a wide range of greener hybrid devices based on other chemistries, comprising entirely recyclable components.Lithium-ion capacitors (LICs) shrewdly combine a lithium-ion battery negative electrode capable of reversibly intercalating lithium cations, namely graphite, together with an electrical double-layer positive electrode, namely activated carbon. However, the beauty of this concept is marred by the lack of a lithium-cation source in the device, thus requiring a specific preliminary charging step. The strategies devised thus far in an attempt to rectify this issue all present drawbacks. Our research uncovers a unique approach based on the use of a lithiated organic material, namely 3,4-dihydroxybenzonitrile dilithium salt. This compound can irreversibly provide lithium cations to the graphite electrode during an initial operando charging step without any negative effects with respect to further operation of the LIC. This method not only restores the low CO2 footprint of LICs, but also possesses far-reaching potential with respect to designing a wide range of greener hybrid devices based on other chemistries, comprising entirely recyclable components.

Electrochemical intercalation of lithium into the perovskite-type NbO2F: influence of the NbO2F particle size

Abstract Niobium(V) oxyfluoride, NbO2F, has a perovskite structure and presents the property of lithium intercalation by topotactic chemical reaction either with n-butyllithium dissolved in n-hexane or by electrochemical reaction. The intercalation leads to the reduction of the transition metal from the oxidation state Nb(V) to the oxidation state Nb(III). This allows a theoretical Li/NbO2F intercalation ratio of 2. In this paper we will show that this theoretical value can be approached by using micron the sized active material particles. Moreover, the electrical properties of the cathode studied by the galvanostatic intermittent titration technique and a.c. impedance spectroscopy are explained in terms of structural and grain size considerations. Results of cycling experiments are also described.

Tin based alloys for lithium ion batteries

The electrochemical behaviour of a standard electrodeposited equiatomic nickel-tin alloy has been tested. Such a material can be an interesting candidate to make thin film anodes for lithium ion batteries since it is deposited by a simple electroplating technique. Using standard deposition conditions, 3 µm thick films of NiSn alloy were deposited onto copper current collectors. The électrochemical behavior of the electrodes suggests that the decomposition of the NiSn alloy occurs during the lithium insertion leading to the formation of nickel particles, followed by the formation of Li-Sn alloys. It is believed that the extraction of lithium during the discharge leads to the decomposition of the Li-Sn alloys. However, according to the structural characterizations performed on the samples, there is no clear evidence to support these reactions. Despite an interesting theoretical capacity of 682 mAh/g, the maximum capacity observed in the NiSn thin films was 77 mAh/g. This low value of the capacity is related to a very slow diffusion of lithium throughout the electrode.

Capacitive and Pseudocapacitive Electrodes for Electrochemical Capacitors and Hybrid Devices

Abstract Electrochemical capacitors are energy storage devices that have intermediate energy and power densities between those of batteries (high energy) and dielectric capacitors (high power). In this chapter, the distinctions between these different devices, as well as emerging devices such as lithium-ion capacitors, are presented in terms of electric and electrochemical properties. The materials for electrochemical capacitors are classified with respect to their charge storage behavior and the electrochemical techniques that are used to characterize them. The different types of carbon that have been investigated as electrode materials are depicted with a special focus on the modern theory on electrochemical double-layer capacitance. The concept of “pseudocapacitance” is explained and the differences between battery-type electrodes and pseudocapacitive electrodes are detailed, distinguishing “intrinsic” from “extrinsic” pseudocapacitance. The role of battery-type electrodes in hybrid capacitors is also explained.

Ni(OH)2 and NiO Based Composites: Battery Type Electrode Materials for Hybrid Supercapacitor Devices

Nanocomposites of Ni(OH)2 or NiO have successfully been used in electrodes in the last five years, but they have been falsely presented as pseudocapacitive electrodes for electrochemical capacitors and hybrid devices. Indeed, these nickel oxide or hydroxide electrodes are pure battery-type electrodes which store charges through faradaic processes as can be shown by cyclic voltammograms or constant current galvanostatic charge/discharge plots. Despite this misunderstanding, such electrodes can be of interest as positive electrodes in hybrid supercapacitors operating under KOH electrolyte, together with an activated carbon-negative electrode. This study indicates the requirements for the implementation of Ni(OH)2-based electrodes in hybrid designs and the improvements that are necessary in order to increase the energy and power densities of such devices. Mass loading is the key parameter which must be above 10 mg·cm−2 to correctly evaluate the performance of Ni(OH)2 or NiO-based nanocomposite electrodes and provide gravimetric capacity values. With such loadings, rate capability, capacity, cycling ability, energy and power densities can be accurately evaluated. Among the 80 papers analyzed in this study, there are indications that such nanocomposite electrode can successfully improve the performance of standard Ni(OH)2 (+)//6 M KOH//activated carbon (−) hybrid supercapacitor.