Challenges and Strategies of High-Capacity Transition Metal Oxides as Anodes for Lithium-Ion Batteries (LIBs)

To satisfy the growing demand for high-energy and high-power-densities Lithium-ion Batteries (LIBs), the design and development of efficient electrode materials are necessary. In comparison to graphite, transition metal oxides (TMOs) have recently been widely investigated as anode materials due to their promising properties. These combine high specific capacities and high working potential, making them attractive anode candidates for emergent applications. Unfortunately, because of their poor electronic conductivity and high-volume expansion during cycling, they are unpractical and difficult to employ. To overcome these limitations, different approaches have been adopted. Examples are synthesizing the metal oxides at the nanometric scale, designing three-dimensional or hollow structures, coating the material with carbonaceous materials, etc. In this chapter, we report the elaboration of nanostructured transition metal oxides (Co3O4, Mn3O4, Co3−xMnxO4) using alginate gelling synthesis method. The Co3O4 octahedral-like nanoparticles display a remarkable cycling performance and good rate capability of 1194 mAh g−1 at C/5 and 937 mAh g−1 at 2C. Partially substituting the Co with Mn was shown to result in the production of Co2.53Mn0.47O4 and MnCo2O4 with high initial specific discharge capacities of 1228/921 and 1290/954 mAh g−1, respectively. As a Co-free material, the Mn3O4 delivers a reversible capacity of 271 mAh g−1, after 100 cycles

Study of electrolytes for lithium-ion capacitors

Le travail réalisé dans cette thèse concerne l'optimisation d’électrolytes organiques pour supercondensateur lithium-ion. Plusieurs solvants ont été sélectionnés pour la formulation de mélanges binaires ou ternaires additionnés de sel de lithium. Les propriétés physicochimiques et électrochimiques de ces électrolytes contenant LiTFSI ou LiPF6 (EC/DMC ; dinitrile/DMC ; EC/Ester/3DMC, EC/MiPC/3DMC) ont été caractérisées en vue de leur utilisation dans des dispositifs hybrides, l’objectif étant de satisfaire à la fois aux exigences des matériaux graphite et carbone activé. Les interactions solvant-solvant et solvant-sel des électrolytes ont été étudiées à partir des théories de Jones-Dole, Stocks-Einstein et Bjerrum appliquées aux mesures de viscosités et conductivités. Cela a permis de développer des modèles prédictifs de la conductivité dans des cas de solvants purs ou de mélanges simples. La deuxième partie de cette thèse a été dédiée à la réalisation de demi-cellules avec différentes formulations d'électrolytes à la fois sur carbone activé et sur graphite. Les interfaces électrodes/électrolytes et séparateurs/électrolytes ont été étudiées. La corrosion des collecteurs en Al en présence de LiTFSI a fait l'objet d'une étude qui a permis de dégager une solution consistant en la formulation d'un électrolyte additionné de 1% d'additifs source de fluorure tel que LiPF6. Enfin, des dispositifs complets graphite/carbone activé ont été réalisés en utilisant les différents électrolytes optimisés ce qui a permis de mettre en évidence le gain en énergie (x5) pour un tel système par rapport aux supercondensateurs symétriques classiques.The objective of this thesis is to broaden the knowledge of electrochemical, thermo physical and thermodynamic properties of different efficient and safe organic electrolytes for Lithium-ion Capacitors (LICs). Several solvent structures have been first selected to design new electrolytes based on binary or ternary solvent mixtures. These solvents were then characterized through conductivity, viscosity and electrochemical studies, in order to assess their structure and properties relationships. Based on this investigation, best compromise between mobility and ionic concentration has been evaluated to formulate the best electrolytes. Generally, it was proved that the addition of solvents with very low viscosity provides efficient electrolytes. Based on conductivity and viscosity measurements, a theoretical study on solvent-solvent and solvent-salt interactions has been then performed using different well-known equations based on Stock-Einstein, Jones-Dole and Bjerrum theories to understand, rationalize, correlate and then predict their transport properties. The second part of the study concentrated on the characterization of selected electrolytes in an asymmetric LIC prior to developing such electrolytes in any high performance asymmetric capacitor devices. In other words, the main objective of this part is to verify the compatibility of designed electrolytes with each element, e.g. electrodes (graphite, activated carbon) and current collectors (aluminum), of a LIC device. To drive such analysis, different experimental investigations between electrodes/electrolytes and between collectors/electolytes were in fact investigated. Using this strategy, asymmetric systems LICs containing a formulated organic electrolyte were fully characterized to deter mine the electrochemical performances of the designed solution in LIC conditions and then compared with those observed using classical electrolyte currently used

High-Voltage Lithium-ion Capacitors Based on Glutaronitrile Electrolytes

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Electrochemical lithiation and compatibility of graphite anode using glutaronitrile/dimethyl carbonate mixtures containing LiTFSI as electrolyte

International audienceThe compatibility of glutaronitrile (GLN) and its mixtures with dimethyl carbonate (DMC) containing lithium bis-(trifluoromethane sulfonyl) imide (LiTFSI) with graphite negative electrode was investigated. GLN/DMC/LiTFSI electrolytes’ mixtures were characterized in terms of their ionic conductivities and viscosities. Cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy were performed in order to study the performances of the graphite anode in the GLN-based electrolytes. Results clearly indicate that no significant Li intercalation occurs in graphite in pure GLN, but when GLN/DMC (1:1 and 1:3 w/w) mixtures were used, the cycling ability of the electrode was improved as the coulombic efficiency reaches 98 and 99 %, respectively. Moreover, SEM images of the graphite anode indicate that after being cycled in GLN-based electrolytes, the electrode surface was homogenously covered by a Solid Layer Interface which insures a reversible lithiation of graphite anode

Revealing the Influence of Electrolyte Additives in Reducing the Heat Generation of High Voltage Lithium‐Ion Batteries using Operando Accelerating Rate Calorimetry (ARC)

Abstract Lithium‐ion batteries operating at high voltage generally endure drastic capacity fading and serious safety issues. Working on the electrolytes’ stability can be a solution to mitigate these problems related to high voltage. Herein, the beneficial impact of functional electrolyte additives in a state‐of‐the‐art carbonate‐based electrolyte is demonstrated. The combination of fluoroethylene carbonate (FEC) with succinonitrile (SN) as additives was used to enhance the thermal stability of the electrolyte reference 1 M LiPF 6 in EC:DMC (1 : 1, by weight) and cycling stability of a high voltage lithium‐ion device, consisting of a LiMn 1.5 Ni 0.5 O 4 cathode and a metallic lithium anode. The electrolyte using the FEC/SN mixture displayed a wider electrochemical stability window (ESW) exhibited by linear sweep voltammetry (LSV). Furthermore, this electrolyte allowed the device to exhibit better rate capability and a capacity retention of 75 % after 100 cycles. Interestingly, the FEC+SN‐based electrolyte exhibited better thermal stability using operando accelerating rate calorimetry (ARC) by virtue of the lower heat quantity generated by the battery device. The remarkable improvements can be ascribed to the formation of a protective cathode‐electrolyte interface (CEI) produced by interfacial reactions between the cathode surface and electrolyte compounds

Nanostructured CoFe2O4 as Negative Electrode Materials for the Next Gen. Li-Ion Batteries

To meet the increasing energy demand for electric vehicles, renewable and grid storage systems, the design and the manufactory of new electrode materials is crucial. Recently, huge efforts have been oriented to the development of high capacity anode material as one of the important components for next-generation lithium-ion batteries. Compared to graphite which dominates the LIBs anode market, nanostructured metal oxides have demonstrated promising properties such as higher specific capacities and lower working potential, and hence can be regarded as tempting candidates for the long term application [1]. In this work, cobalt ferrite oxide CoFe2O4 has been prepared by the alginate gelling method. The face-centered cubic spinel structure and the spherical morphology of the produced material were confirmed using XRD, Raman spectroscopy, and SEM techniques. As anode material for LIBs, the material exhibits good cycling and multi-rate capability performances (976 mAh g-1 at C/5 and 570 mAh g-1 at 2C). To go further and to understand the lithiation/delithiation mechanism in-situ XRD and Ex-situ Mössbauer spectroscopy techniques have been performed. Reference [1] K. Cao, T. Jin, Y. Li and L. Jiao, "Recent progress on conversion reaction metal oxide anodes for Li-ion batteries", Materials chemistry Frontiers, vol. 1, pp. 2213-2242 (2017