Proton conducting plastic crystal electrolytes based on pivalic acid

Peer reviewed: YesNRC publication: Ye

A Polymer-Rich Quaternary Composite Solid Electrolyte for Lithium Batteries

All-solid-state batteries continue to grow as an alternative to replace the traditional liquid-based ones not only because they provide increased safety but also higher power and energy densities. However, current solid-state electrolytes are either ceramics that are brittle but highly conducting (e.g. Li0.33La0.55TiO3, LLTO) or polymer electrolytes that are poorly conducting but form flexible films with desired mechanical properties (e.g. Poly(ethylene oxide):Lithium bis(trifluoromethanesulfonyl)imide, PEO:LiTFSI). In this work, we have developed quaternary composite solid-state electrolytes (CSEs) to combine the benefits of the two types along with Succinonitrile (SN) as a solid plasticizer. CSEs with different compositions have been fully characterized over the whole compositional range. Guided by neural network simulation results it has been found that a polymer-rich CSE film gives the optimal ionic conductivity (>10−3 S cm−1 at 55 °C) and mechanical properties (Tensile strength of 16.1 MPa; Elongation-at-break of 2360%). Our solid-state coin-type cell which employs our in-house made cathode shows good cycling performance at C/20 and 55 °C maintaining specific discharge capacity at 143.2 mAh g−1 after 30 cycles. This new approach of formulating quaternary CSEs is proven to give the best combination of properties and should be universal and be applied to other CSEs with different chemistry

Proton conducting polymer electrolytes for CO sensors

Commercially available CO sensors suffer from many drawbacks most important of all is the dependence of their performance on changes in humidity. The objective of this work is to develop a non-aqueous proton conducting polymer to overcome such a problem. IMI. Poly(vinyledenefluoride-co-hexafluoropropylene), of A novel ionic liquid consisted of a mixture of imidazole and imidazolium bis- (triflouromethanesulphonyl imide) solids, The liquid was introduced into poly(vinyledenefluoride), FVdF, PVdF-HFP, poly(epichlorohydrin-co-ethyleneoxide), poly(methylmethacrylate), PMMA and PVdF-HFP polymeric hosts in order to obtain homogeneous films. Compatibility of the polymer hosts with IMI was first addressed. PEE and the (PMMA/PVdF-HFP) blend gave homogenous films whereas IMI mixtures with PVdF or PVdF-HFP were phase segregated. The latter became homogenous upon addition of propylene carbonate, PC. Conductivity of the films were studied as a function of IMI content, where a linear behaviour was observed between the logarithm of the conductivity versus the IMI content. A percolation threshold was proposed to explain the observed break point in the conductivity dependence of the PVdF-HFP:IMI films. XRD, TGA and DSC were used to characterise the films. blend PEE and a A planar amperometric CO sensor was fabricated using a IMI:PC:PVdF-HFP film. The sensor showed no response without being pre-equilibrated with water. The sensor response and tgo were found to be dependent on the CO concentration and relative humidity. Cyclic Voltammograms were performed on a Pt electrode in a IMI:PC solution. It was concluded that water was very crucial for the CO oxidation. A new gap electrode method was developed to measure the conductivity of the films. The results showed that uncontrollable variations in either the polymer conductivity or the geometry or both have made it difficult to fit the systematic variation to the theoretical model. Nevertheless, acceptable conductivity values were obtained for the polymers by a combined normalization/iteration method. The technique should therefore be generally applicable given better control of polymer uniformity and thickness.</p

New electrolytes based on glutaronitrile for high energy/power Li-ion batteries

Peer reviewed: YesNRC publication: Ye

Non-flammable electrolyte mixtures of ringed ammonium-based ionic liquids and ethylene carbonate for high voltage Li-ion batteries

Three ionic liquids based on ringed ammonium cations with different ring sizes [seven: azepanium; six: piperidinium; five: pyrrolidinium] and imide anion mixed with ethylene carbonate, EC, have been evaluated as electrolytes in high voltage lithium-ion batteries. It is found that mixing the ionic liquids with ethylene carbonate gives electrolyte mixtures with lower viscosities, increased conductivities and improved electrochemical cathodic stability than the neat ionic liquids. The flammability and thermal stability of the electrolytes have been studied by open-cup flash point measurements and thermogravimetric analysis combined with Infrared and Mass Spectroscopy. It is found that the neat ionic liquids have good thermal stability above 300\ub0C and no flammability compared to carbonate-based electrolyte but upon mixing with EC the mixture decomposes at temperature below 130\ub0C but stays non-flammable. The electrolyte mixtures have been evaluated in Li/LiMn\u2081.\u2085Ni\u2080.\u2085O\u2084 (LMNO) and graphite/Li half cells and in the presence of fluoroethylene carbonate additive. Discharge capacities reaching 112\u2013117 mAh.g\u207b\ub9 and 280\u2013293 mAh.g\u207b\ub9 with coulombic efficiencies of 95% and 99% were obtained for graphite and LMNO, respectively, over 100 cycles at C/12.Peer reviewed: YesNRC publication: Ye

New advanced lithiunm-ion battery electrolyte technologies for high power/energy density Li-ion batteries

Peer reviewed: YesNRC publication: Ye

New advanced lithium-ion battery electrolyte technologies for PHEVs

Peer reviewed: YesNRC publication: Ye

High-voltage electrolytes based on adiponitrole for Li-ion batteries

Adiponitrile, CN[CH2]4CN, ADN, was evaluated as both a solvent and cosolvent in safer and more electrochemically stable electrolytes suitable for high energy and power density Li-ion batteries. An electrochemical investigation of its electrolyte solution with the Li(CF3SO2)2N, LiTFSI, salt showed a wide electrochemical window of 6 V vs Li+/Li. The high melting point and the incompatibility of ADN with graphite anode required the use of ethylene carbonate (EC) as a cosolvent. The resultant EC:ADN electrolyte solutions showed ionic conductivities reaching 3.4 mS/cm, viscosities of 9.2 cP, and an improved resistance to aluminum corrosion up to 4.4 V, all at 20\ub0C. Li-ion batteries incorporating graphite/LiCoO2 electrodes were assembled using EC:ADN electrolyte mixture containing 1 M LiTFSI and 0.1 M LiBOB as a cosalt, and discharge capacities of 108 mAh/g with very good capacity retention were obtained. AC impedance spectra of the batteries recorded as a function of charging and cycling indicated the presence of a stable solid electrolyte interface.On a \ue9valu\ue9 l\u2019adiponitrile, CN[CH2]4CN (ADN), en tant que solvant ou cosolvant pour des \ue9lectrolytes plus s\ue9curitaires et plus stables sur le plan \ue9lectrochimique, convenant \ue0 des piles Li/ion \ue0 haute \ue9nergie et haute densit\ue9 de puissance. Une \ue9tude \ue9lectrochimique de sa solution \ue9lectrolyte avec le sel Li(CF3SO2)2N, LiTFSI, a permis de mettre en \ue9vidence une large fen\ueatre \ue9lectrochimique de 6 V par rapport \ue0 Li+/Li. Le point d\u2019\ue9bullition \ue9lev\ue9 et l\u2019incompatibilit\ue9 de l\u2019ADN avec l\u2019anode en graphite ont rendu n\ue9cessaire l\u2019utilisation de carbonate d\u2019\ue9thyl\ue8ne (CE) comme cosolvant. Les solutions \ue9lectrolytes CE/ADN ont exhib\ue9 des conductivit\ue9s ioniques pouvant atteindre 3,4 mS/cm, des viscosit\ue9s de 9,2 cP et une meilleure r\ue9sistance \ue0 la corrosion de l\u2019aluminium jusqu\u2019\ue0 4,4 V, le tout \ue0 20 \ub0C. On a assembl\ue9 des piles Li/ion comportant des \ue9lectrodes graphite/LiCoO2 et un m\ue9lange \ue9lectrolyte CE/ADN contenant du LiTFSI 1 M et du LiBOB 0,1 M en tant que co-sels, qui ont exhib\ue9 des capacit\ue9s de d\ue9charge de 108 mAh/g avec une tr\ue8s bonne r\ue9tention de capacit\ue9. Le spectre d\u2019imp\ue9dance c.a. des piles enregistr\ue9 en fonction de la charge et du cycle a mis en \ue9vidence la pr\ue9sence d\u2019une interface \ue9lectrolyte solide stable.Peer reviewed: YesNRC publication: Ye

Ionically-functionalized poly(thiophene) conductive polymers as binders for silicon and graphite anodes for li-ion batteries

Next-generation anode materials for Li-ion batteries such as silicon can lead to ten\u2005times more capacity than the state-of-the-art graphite. However, novel binders are required to overcome the detrimental effects of volume changes during battery cycling of silicon because of the poor chemical interaction and electrical conductivity between silicon and the binder. Most studies focus on either ionic binders or electrically conductive binders, but herein it was demonstrated that a new family of polymers based on electrically conductive poly(thiophene) functionalized with an ionic alkyl carboxylate groups of various lengths can successfully work as multifunctional binders for silicon and commercial graphite anodes in Li-ion battery half-cells. It was determined that the polymer with shorter side chain (PT-3-LiA) gives the highest reversible capacity upon pairing with graphite or silicon, reaching 3000\u2005mAh\u2009g 121 in the case of the latter, a capacity 500\u2005mAh\u2009g 121 ( 4822\u2009%) higher than those obtained with the electrically, but non-ionically, conductive PEDOT:PSS binder and the ionically, but non-electrically, conductive sodium carboxymethyl cellulose (NaCMC) binder. It is demonstrated that the superior performance of this new type of multifunctional binders can be attributed to their ability to maintain their doping level and conductivity as well as due to good interaction with the silicon surface during cycling.Peer reviewed: YesNRC publication: Ye