Lithium Metal Polymer Research Articles

Stable Cyclability of Novel Triblock Polyelectrolyte Separators for Lithium Metal Battery

Lithium metal is a promising anode for next generation lithium batteries due to its high theoretical energy density (3860mAh g-1). However, despite the attractive feature of lithium metal, its dendrite could form short circuit inside the cells and cause serious safety problems during lithium plating and stripping process. Polymer electrolyte with high lithium transference number and high modulus would substantially mitigate dendrite growth in lithium metal battery. According to previous models, structuring the electrolyte to immobilized the anions with high shear modulus is of the various options to suppress dendrite growth. In this work, we designed a single-ion conductor (SIC) based on a block copolymer using sulfonic anion, whose structure covalently bonded with hydoxylated polyisoprene (named as sPI) to reach high transference number. Polystyrene can be used to support the mechanical properties of matrix and the adjacent polyisoprene with double bond main chain plays a decoupling role (PI(1,4)) which separate the stiff PS domain, and the lithium conducting sPI domain (referred to SII block copolymer). Using small angle X-ray scattering and transmission electron microscopy, nanostructures of membranes were identified as a bi-continuous network structure. Remarkably, the maximum conductivity was 1.4×10-4 S cm-1 at ambient temperature with merely 30 wt% solvent uptake. The lithium transference number (TLi +) was nearly unity in liquid electrolyte. The Young’s modulus of SII was 53 MPa and storage modulus was nearly 3 GPa at room temperature. This bi-continuous morphology with high TLi +, high modulus, and moderate conductivity is believed to suppress dendrite grow effectively. From galvanostatic cycling experiments, we found that the presence of PS and the sPI in SII membrane in liquid electrolyte with lithium symmetric cell provides over 245 hr in cell life time. Batteries containing SII membranes in liquid electrolyte are able to cycle at least 20 times with high coulombic efficiency (98%). This results warrant that the sPI can effectively delay lithium dendrite formation due to reduced uneven lithium deposition while maintaining the mechanical property with moderate values by adjusting PS and PI(1,4) length, and this architecture design also made the application of SIC in lithium metal polymer battery possible in the future.

Modeling Co-Extruded Cathodes for High Energy Lithium-Ion Batteries

Utilizing an existing macro-homogeneous porous electrode model developed by John Newman, this talk presents the potential energy density gains that can be realized in lithium-ion battery electrodes fabricated with co-extrusion (CoEx) technology. CoEx uses carefully engineered fluidic channels to cause multiple streams of dissimilar fluids to impart shape to one another. The result is a high-speed, continuous deposition process that can create fine linear structures much smaller than the smallest physical feature within the printhead. By eliminating the small channels necessary for conventional extrusion and injection processes, CoEx is able to deposit highly loaded and viscous pastes at high line speeds under reasonable operating pressures. The CoEx process is capable of direct deposition of features as small as 10 μm with aspect ratios of 5 or greater, and print speeds > 80 ft/min. We conduct an analysis on two-dimensional cathode cross-sections in COMSOL and present the electrochemical performance results, including calculated volumetric energy capacity for Lithium Nickel Manganese Cobalt Oxide (NMC) co-extruded cathodes, in the presence of a lithium metal anode, polymer separator and ethylene carbonate–diethyl carbonate (EC:DEC) liquid electrolyte. The impact of structured electrodes on cell performance is investigated by varying the physical distribution of a fixed amount of cathode mass over a space of dimensions which can be fabricated by CoEx. By systematically varying the thickness and aspect ratio of the electrode structures, we present an optimal subset of geometries and design rules for co-extruded geometries. Modeling results demonstrate that NMC CoEx cathodes, on the order of 125-200 µm thick, can garner an improvement in material utilization and in turn capacity through the addition of fine width electrolyte channels or highly conductive electrode regions. We also present initial experimental results on CoEx NMC cathode structures. The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000324.

Scalable plasticized polymer electrolytes reinforced with surface-modified sepiolite fillers – A feasibility study in lithium metal polymer batteries

Electrochemical properties of (polyethylene oxide) (PEO)/lithium trifluoromethanesulfonate (LiTf)/ethylene carbonate (EC)/sepiolite extruded composite electrolytes were studied. Appreciable electrochemical stability of 4.5 V at 70 °C was observed for polymer composite membranes with d-α-tocopherol-polyethylene glycol 1000 succinate-coated sepiolite fillers. Lithium plating/stripping analysis indicated no evidence of dendrite formation with good interfacial properties which were further confirmed by postmortem analysis of the cells. Solid state NMR studies show the presence of two Li+ population in the membranes. The feasibility of these electrolytes has been shown with LiFePO4 cathode materials. Initial discharge capacity of 142 mAh/g was observed remaining at 110 mAh/g after 25 cycles with a coulombic efficiency of 96%. The upscaling of these polymers can be easily achieved by extrusion technique and the capacity can be improved by varying the cathode architecture.

All-Solid-State Lithium Secondary Battery Using Plastic Crystal As Solid Electrolyte

Introduction All-solid-state lithium ion batteries (ASS-LIBs), which consist of nonflammable solid electrolyte, are expected as high capacity and safety secondary batteries for vehicle and industrial use. Bulk-type ASS-LIBs, whose positive and negative electrodes are composed of an active material, a conductive agent, a binder and a solid electrolyte, are more desirable than film type electrode, in terms of capacity and energy density. A main issue of the bulk-type ASS-LIBs is reduction of internal resistance of the electrodes, which originated from a poor contact between the electrolyte and the active materials to form the micro void. Plastic crystalline fast ion conductors have been studied as the solid-state electrolyte for ASS-LIBs [1, 2]. As these materials readily deform above relatively low melting point, for example 1-ethyl-1-methyl pyrolidinium bis(trifluoromethylsulfonyl imide (12PyrTFSI) melt at 90 °C, it will form a favorable active material-electrolyte solid-solid interface. In this study, to reduce the internal resistance of the electrode, lithium ion conductive plastic crystals which show thermoplasticity was used as solid electrolyte. Experimental In this research, a mixture of 12PyrTFSI and lihium sulfonyl imide (LiTFSI) was used as lithium conductive plastic crystal. We developed a negative electrodes consisting of lithium titanium oxide (LTO), acetylene black, polyvinylidene fluoride, the mixture of 12PyrTFSI, LiTFSI. The negative electrode was obtained by coating the dispersion slurry containing the above mentioned materials and N-methylpyrrolidone (NMP), and thereby drying NMP solvent. Drying temperature was selected more than 71 °C that is a melting point of the mixture of 12PyrTFSI and LiTFSI [3]. The negative electrodes were structurally characterized by SEM-EDX. The anode half cell was prepared by assembling the anode on a polyethylene oxide (PEO) polymer sheet and Li foil as reference counter electrode to measure the charge and discharge property of the negative electrodes. At 50 °C, the charge and discharge were operated in the galvanostatic mode at 5.57 μA¥cm-2 (0.02C). The internal resistance of the negative electrode after charge was obtained using an impedance analyzer over a frequency range of 0.1 to 106 Hz and amplitude of 10 mV at 50 °C. The cells were cycled between 1 to 1.35 V vs. Li/Li+. Fig.1 illustrates the charge and discharge curves of the LTO negative electrode with a plastic crystal. The discharge capacity at the first cycle was 82 mA¥g-1 at 0.02 C, which is only 47 % of theoretical capacity. The cross sectional SEM images showed that the plastic crystal was not uniformly distributed in the electrode. Conceivably, the non-uniform distribution resulted in the formation of heterogeneous lithium ion conduction path over the negative electrode, deteriorating the discharge capacity. Fig. 2 shows Nyquist plots of the negative cell after first charging. The interfacial resistance between lithium metal and PEO polymer sheet and internal resistance of the negative electrode forms an arc. It shows the small resistance of the negative cell 55 Ωcm2. Evidently, partial ion conduction path comprising of 12PyrTFSI and LiTFSI contributed to the low internal resistance of the negative cell. It was concluded that the formation of the homogeneous ion conduction path was needed to increase the capacity of the negative electrode.

Composite Polymer Electrolyte Containing Core-Shell Structured SiO2(Li+) Particles for Suppressing Lithium Dendrite Growth and Improving High Temperature Cycling Stability of LiNi0.5Mn1.5O4

The most widely used electrolyte for lithium-ion batteries is lithium hexafluorophosphate (LiPF6) in a mixture of organic carbonate solvents due to its high conductivity, good electrochemical stability and acceptable cycle performance at low temperatures [1]. However, the use of liquid electrolytes in lithium batteries has many drawbacks, such as high flammability of organic solvents, possibility of leakage and poor thermal stability [2, 3]. Among the potential electrolytes for lithium batteries, polymer electrolyte has received considerable attention due to high ionic conductivity and superior thermal safety with no electrolyte leakage [4]. However, polymer hosts lose their mechanical strength when they are plasticized with liquid electrolyte solution, leading to serious problems in terms of cycle life and safety [5]. In this study, in order to obtain polymer electrolytes with enhanced mechanical strength and good electrochemical properties, core-shell structured SiO2 nanoparticles containing poly(lithium acrylate) in the shell were synthesized. They were used as functional fillers in preparing composite polymer electrolytes for suppressing lithium dendrite growth and preventing HF generation in the electrolyte. The composite polymer electrolytes prepared with SiO2(Li+) particles exhibited high ionic conductivity, good thermal stability and favorable interfacial characteristics. The lithium metal polymer cells composed of lithium metal negative electrode and LiNi0.5Mn1.5O4 positive electrode are assembled and their cycling performances are evaluated. The cells assembled with the composite polymer electrolyte exhibited superior cycling performance both at ambient temperatures and at elevated temperature.

Lithium Metal Polymer Battery: Towards Optimized Cathodes and Crosslinked Polymer Electrolytes

Although lithium metal polymer batteries (LMPBs) have lots of advantages such as high energy density, design flexibility and enhanced safety, they have not been widely used in the commercial market due to low ionic conductivity and poor interfacial stability towards electrodes comparing to liquid electrolytes. However, most of researches on LMPBs have been focused for electrolytes themselves without broad cell performance data such as cycle life and rate capability. Furthermore, as discovered in previous works on commercial LIBs, the electrode density and thickness are also very crucial parameters governing the electrochemical performance of batteries. For the purpose of providing basic but essential electrochemical properties of LMPB, we have manufactured four different LiFePO4 cathodes with different densities and thicknesses. Their physical and electrochemical properties are investigated by using the unit cells consisting of LiFePO4/cross-linked polymer electrolyte/Li metal. In particular, with the optimized cathode and crosslinked polymer electrolyte, high capacity retention could be realized at even 5C and room temperature. Acknowledgements This research was financially supported by the Ministry of Education, Science and Technology (MEST) and National Research foundation (NRF) of Korea through the Human Resource Training Project for Regional Innovation (2014066977) and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2014046008). Figure 1

Lithium Metal Polymer Battery Interfaces Studied By Hard X-Ray Microtomography

Conventional Lithium-ion batteries contain volatile liquid compounds that can leak and violently react with the environment leading to a fire.1 Solid polymer electrolytes (SPEs) are one solution as these flexible materials do not contain any volatile components. Additionally, they enable the use of high energy density lithium (Li) metal anodes.2 However, Li metal battery utilization is hampered by the dendrite growth.3 Upon cycling lithium metal is plated unevenly on the lithium metal anode side. Such dendrites can grow through the electrolyte and cause the battery to fail by short circuit. Solid block copolymer electrolytes are a class of SPEs that contains a mechanical reinforced block and an ion conducting block doped with a Li salt.4 The block immiscibility induces microphase separation, producing ordered morphologies on the nanometer scale.5 The seminal work done by K.J. Harry et al. 6 on solid polystyrene-b-poly(ethylene oxide) (SEO) block copolymer electrolyte led to a better understanding of Li dendrite formation and growth. Using Li symmetric cells dendrite evolution was observed and imaged by a non-destructive tool, hard X-ray microtomography. To go toward the application, batteries were imaged by hard X-ray microtomography. The batteries are made of a Li metal anode, a SEO electrolyte layer and a composite cathode. The cathode deposited onto on Aluminum (Al) foil, contains LiFePO4 as active material, SEO electrolyte as binder, and carbon black. Hard X-ray microtomography enables to visualize the microstructural changes at the Li/SEO and SEO/cathode interfaces to get insight on the battery failure mechanisms. The batteries were cycled at 90°C at a C/20 charge rate and a C/8 discharge rate (Figure 1a). Prior and after battery cycling, the electrode-electrolyte interfaces were imaged by hard X-ray microtomography as shown in figure 1b and 1c, respectively. We found that the supposed intimate Li/SEO interface undergoes a strong delamination phenomenon that leads to the formation of voids (Figure 1b). Using a rendering image software, the void fraction can be measured all along the Li/SEO interfaces, and its effect on the battery capacity fading be estimated. References J.-M. Tarascon, M. Armand, Nature, 414 (2001) 359.M. Armand, J.-M. Tarascon, Nature, 451 (2008) 652.M. Rosso, C. Brissot, A. Teyssot, M. Dollé, L. Sannier, J.-M. Tarascon, R. Bouchet, S. Lascaud, Electrochimica Acta, 51 (2006) 5334.M. Singh, O. Odusanya, G.M. Wilmes, H.B. Eitouni, E.D. Gomez, A.J. Patel, V.L. Chen, M.J. Park, P. Fragouli, H. Iatrou, N. Hadjichristidis, D. Cookson, N.P. Balsara, Macromolecules, 40 (2007) 4578.V. Abetz, T. Goldacker, Macromolecular Rapid Communications, 21 (2000) 16.K.J. Harry, D.T. Hallinan, D.Y. Parkinson, A.A. MacDowell, N.P. Balsara, Nature Materials, 13 (2014) 69. Figure 1

A rechargeable lithium/quinone battery using a commercial polymer electrolyte

The present study reports superior electrochemical performance with capacity doubled for organic positive electrodes based on a small redox-active molecule when using the Lithium Metal Polymer (LMP) technology. Particularly, the simple use of the regular solid polymer electrolyte currently employed in commercial LMP cells allows obtaining for the first time an efficient two-electron cycling of tetramethoxy-p-benzoquinone with high-rate capability at temperatures as high as 100 °C. With no optimization, the restored capacity represents 80% of the theoretical value (190 mAh/g) after 20 cycles operated at a C rate. On the contrary, when cycled in conventional carbonate-based electrolytes, this quinone compound exhibits quite poor electrochemical features such as a very limited depth of discharge (~ 50% of the theoretical capacity in the first cycle) followed by rapid capacity decay. After cycling, preliminary post-mortem characterizations did not evidence any obvious degradation in the cell. Although the adverse effect of the diffusion of the active material is not fully inhibited, the coulombic efficiency is close to 100% while the Li/electrolyte interface appears stable.

New lithium metal polymer solid state battery for an ultrahigh energy: nano C-LiFePO₄ versus nano Li1.2V₃O₈.

Novel lithium metal polymer solid state batteries with nano C-LiFePO4 and nano Li1.2V3O8 counter-electrodes (average particle size 200 nm) were studied for the first time by in situ SEM and impedance during cycling. The kinetics of Li-motion during cycling is analyzed self-consistently together with the electrochemical properties. We show that the cycling life of the nano Li1.2V3O8 is limited by the dissolution of the vanadium in the electrolyte, which explains the choice of nano C-LiFePO4 (1300 cycles at 100% DOD): with this olivine, no dissolution is observed. In combination with lithium metal, at high loading and with a stable SEI an ultrahigh energy density battery was thus newly developed in our laboratory.

Composite Gel Electrolytes for Suppressing Lithium Dendrite Growth and Improving Cycling Performance of LiNi0.5Mn1.5O4 Electrodes

Core-shell structured SiO2 particles with a poly(lithium acrylate) shell were synthesized and used in preparing a composite gel electrolyte. The composite gel electrolyte exhibited high ionic conductivity and favorable interfacial characteristics at the lithium electrode. The use of a composite gel electrolyte containing SiO2(Li+) particles effectively suppressed both the dendrite growth of lithium and dissolution of transition metals from the active LiNi0.5Mn1.5O4 material. The lithium metal polymer cell composed of a lithium negative electrode and a LiNi0.5Mn1.5O4 positive electrode delivered a high discharge capacity of 136.6 mAh g−1 and exhibited good capacity retention.

Effect of LiFePO4 cathode density and thickness on electrochemical performance of lithium metal polymer batteries prepared by in situ thermal polymerization

In order to investigate the effects of electrode density and thickness on the room temperature electrochemical performance of lithium metal polymer batteries (LMPBs), four LiFePO4 cathodes with different electrode density/thickness (1.6gcm−3/20μm, 1.6gcm−3/40μm, 2.0gcm−3/20μm, and 2.0gcm−3/40μm) are prepared. Several types of unit cells employing each cathode are prepared using in situ thermally cross-linked polymer electrolytes controlled under the same manufacturing condition. The unit cells employing the thinnest cathode with highest density achieve the most improved rate capability and cycle life, which seems to be attributed to the higher electrical conductivity of the cathode and shorter diffusion length of Li+ ions within the cathode pores. In addition, the LMPB with an optimized LiFePO4 cathode (2.0gcm−3, 20μm) and polymer electrolyte (5vol% of the crosslinking agent with non-volatile liquid electrolytes) delivers a high and stable charge/discharge capacity under very fast charging and discharging conditions (at a 2C rate) at room temperature.

Performance of polyphosphazene based gel polymer electrolytes in combination with lithium metal anodes

This work presents a detailed study of the electrochemical performance of a polyphosphazene based gel polymer electrolyte in a lithium metal polymer cell. The polyphosphazene MEEP was chosen because of its favorable properties, such as good thermal and electrochemical stability versus lithium metal. In combination with a liquid electrolyte, consisting of 0.7 mol L−1 LiBOB in EC/DMC, a high ionic conductivity of ∼9·10−4 S cm−1 at 30 °C was achieved. The electrochemical stability window ranges between 0 V and 4.4 V vs. Li/Li+ reference electrode. The gel polymer was drop coated onto the electrode materials and cross-linked to achieve high mechanical stability. The gel polymer showed a very good interface stability at lithium metal electrodes in the prepared full cells, where a stable SEI was formed during initial contact. The full cell tests delivered a stable cycling behavior with more than 1300 cycles and capacities higher than 110 mAh g−1 at high discharge rates of 2CD, without any indication for short circuits caused by lithium dendrites.

Improved lithium-metal/vanadium pentoxide polymer battery incorporating crosslinked ternary polymer electrolyte with N-butyl-N-methylpyrrolidinium bis(perfluoromethanesulfonyl)imide

Li metal polymer batteries incorporating crosslinked ternary PEO/PYR14TFSI/LiTFSI solid polymer electrolyte (SPE) have been prepared, using V2O5 as active cathode material. As a result of the optimization of the SPE as well as the cell assembly and cycling conditions, V2O5 lithium metal polymer batteries allow reaching 796 Wh kg−1 (of V2O5) at C/10 at 40 °C and maintaining 663 Wh kg−1 after 200 cycles at 40 °C. This is higher than the theoretical specific energy of LiCoO2 vs. Li of 609 Wh kg−1. Cycling at 80 °C allows reaching 270 mAh g−1 at C/2 and 210 mAh g−1 at 1 C, while at 20 °C it is still possible to reach a discharge capacity of almost 100 mAh g−1 at low rates. Post-cycling SEM and EDX imaging showed that, after 200 cycles at 40 °C, if the plating of Li is not fully homogeneous, no sign of dendrite growth nor obvious vanadium dissolution and redeposition on the anode side occurred.

Effects of the Cross-Linking Agent on Electrochemical Performances of the Lithium Metal Polymer Batteries Prepared by In-Situ Thermal Polymerization with Trimethylolpropane Treiacrylate

All-solid lithium metal polymer batteries (LMPBs) consisting of lithium transition metal cathodes, polymer electrolytes and lithium (Li) metal anodes have long been investigated for over two decades to achieve higher level of energy density compared to those of lithium-ion batteries (LIBs) [1-2]. Unfortunately, however, LMPBs have failed to come to the market because of their low level of standard to use; relatively poor ion conductivity level (<10-3 Scm-1) and high interfacial resistance. In order to improve these bottlenecks, gel polymer electrolytes (GPEs) were developed by adding solvents into pure solid polymer electrolytes (SPEs).In this study, we developed the novel GPE systems based on in-situ thermal polymerization process, which play as polymer electrolytes within pores of microporous polyethylene separators and polymeric binders for cathode at the same time. GPEs were synthesized via in-situ thermal polymerization process, and thus it is remarkably economical and easy to handle. We found optimum ratio of cross-linking agent for GPEs, and evaluated cell performance of LMPBs employing the same. Furthermore, we evaluated the effects of GPEs upon surfaces of Li metal anodes and cathodes by monitoring the morphological changes of them by electron scanning microscopy (SEM) as a function of cross-linking agent concentration. Acknowledgements This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (2010-0025738).

All-Solid Lithium Metal Polymer Batteries; Effect of LiFePO4 Cathode Density and Thickness on Electrochemical Performance

All-solid lithium metal polymer batteries (LMPBs) consisting of lithium transition metal cathode, polymer electrolyte and Li metal anode have been investigated for achieving much higher energy density than lithium-ion batteries (LIBs) or providing special design properties such as flexibility[1-2]. Unfortunately, commercially available LMPBs failed to go to market, because solid polymer electrolytes (SPEs) show low ionic conductivity and poor interfacial stability towards electrodes comparing to liquid electrolytes. However, most of researches on SPEs have been focused for electrolytes themselves without broad cell performance data such as cycle life and rate capability. Moreover, even though the cathode should be developed or optimized for LMPB systems, few researches on cathodes (for example, cathode thickness, density, or composition) unlike LIBs have been done systematically for LMPBs up to now [3]. So, in this work, we investigate the room temperature electrochemical properties of all-solid LMPBs while changing cathode thicknesses and densities. The LMPBs consist of LiFePO4/SPE/Li metal, in which SPEs for electrolyte and cathode binder are manufactured by in-situ thermal polymerization after cathode/high porous separator/Li cell assembly. The optimum thickness and density of LiFePO4 cathodes could be found by evaluating cycle performances at room temperatures and rate capability. At the same time, morphological changes within the cathode and electrochemical changes before and after polymerization are also compared precisely. Acknowledgements This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MEST)(2010-0025738).

Modeling mass and density distribution effects on the performance of co-extruded electrodes for high energy density lithium-ion batteries

Utilizing an existing macro-homogeneous porous electrode model developed by John Newman, this paper aims to explore the potential energy density gains which can be realized in lithium-ion battery electrodes fabricated with co-extrusion printing technology. This paper conducts an analysis on two-dimensional electrode cross-sections and presents the electrochemical performance results, including calculated volumetric energy capacity for a general class of lithium cobalt oxide (LiCoO2) co-extruded cathodes, in the presence of a lithium metal anode, polymer separator and liquid ethylene carbonate, propylene carbonate, and dimethyl carbonate (EC:PC:DMC) electrolyte. The impact of structured electrodes on cell performance is investigated by varying the physical distribution of a fixed amount of cathode mass over a space of dimensions which can be fabricated by co-extrusion. By systematically varying the thickness and aspect ratio of the electrode structures, we present an optimal subset of geometries and design rules for co-extruded geometries. Modeling results demonstrate that ultra-thick LiCoO2 electrodes, on the order of 150–300 μm, can garner a substantial improvement in material utilization and in turn capacity through electrolyte channels and fine width electrode pillars which are 25–100 μm wide.

Structural changes of a Li/S rechargeable cell in Lithium Metal Polymer technology

Lithium/sulfur batteries in Lithium Metal Polymer (LMP) technology suffer from poor reversibility and important capacity fade. In this paper we studied structural evolutions of Li/S cells with PEO-based (poly(ethylene oxide)) dry polymer electrolyte, by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Discharge occurs along with dissolution of the active material into soluble polysulfides in PEO. Diffusion of the sulfide species results in important volume changes of both the electrode and the electrolyte. This eventually leads to collapse of the electrode upon a few cycles, which contributes to the poor cyclability of the battery. In order to prevent this phenomenon, the mechanical strength of the cathode was enhanced by adding poly(vinylidene fluoride) (PVDF) in its composition. However, although PVDF helps maintaining the electrode's structure, it could not completely solve the cyclability issue.

Very High Specific Area Lithium-Air Battery

Unlike traditional batteries, the lithium-air cell is an open system by definition, since it needs to have access to oxygen from the surrounding air to work. This has important implications on the cell design. The traditional lithium-ion or LMP (lithium metal polymer) sealed designs can no longer be applied and completely new architectures need to be developed. For example, very large, very thin electrodes tightly wound into cylindrical cells or folded into prismatic cells will be difficult to use since they would lead to air starvation. Positive and negative compartments with high specific surface area capacities therefore need to be developed in order to reduce the size of the electrodes packed into a cell. As a consequence, the negative electrode needs to be able cycle over much greater lithium thicknesses than a lithium battery in order to limit its size. Large amounts of the discharge product per geometrical area unit also have to be stored in the positive electrode. In the aqueous lithium-air design developed by EDF and its partners, the areal capacity of the positive electrode is not limited since the product of the reaction is stored as solid LiOH.H2O in the aqueous electrolyte compartment, and not in the air electrode as in the anhydrous design. The precipitation of LiOH in the aqueous compartment have little impact on the performance of the cell, even up 80% solid LiOH.H2O by volume. Cells that can be charged to more than 100 mAh/cm² on the negative electrode have been obtained.

Temperature dependence of electrochemical properties of cross-linked poly(ethylene oxide)–lithium bis(trifluoromethanesulfonyl)imide–N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide solid polymer electrolytes for lithium batteries

An advanced electrochemical characterization of cross-linked ternary solid polymer electrolytes (SPEs), prepared by a solvent-free hot-pressing process, is reported. Ionic conductivity, electrochemical stability window and limiting current measurements were performed as a function of the temperature by using both potentiodynamic and galvanostatic techniques. Additionally, the lithium cycleability was evaluated with respect to its dependence on both the operating temperature and the current density by using a new multi-rate Li-stripping-plating procedure. The results clearly indicate the beneficial effect of higher operating temperatures on the rate-capability, without major degradation of the electrochemical stability of the SPE. All-solid-state lithium metal polymer batteries (LMPBs), comprising a lithium metal anode, the cross-linked ternary solid polymer electrolyte and a LiFePO4 composite cathode, were manufactured and investigated in terms of the interdependencies of the delivered capacity, operating temperature and discharge rate. The results prove quite exceptional delivered capacities both at medium current densities at ambient temperatures and even more impressive capacities above 160mAhg−1 at high discharge rates (1C) and temperatures above 60°C.

Comparison of Electric Karting Modelling Using Matlab®/Simulink® Software

Electric karting was modelled for efficiency and energy consumption study. The model includes models of battery, power electronics converter, electric motor, and vehicle dynamic of a typical 48 seconds track driving schedule in Europe competition. The regenerative braking energy was also considered in simulation. The comparison of different type of electric motors – direct current (DC) motor, induction motor, permanent magnet synchronous motor (PMSM), brushless direct current motor (BLDC), and switched reluctance motor (SRM) - and batteries – Lead Acid, Lithium Metal Polymer (LMP), Nickel Metal Hybride (NiMH) - also were investigated. Finally, the efficiency was compared between the different type of electric motor and battery. The result shown that the SRM and LMP Battery has a high efficiency and performance compare to the others.