High Energy Density Lithium Batteries Research Articles

Silicon-Carbon Composite Electrode Materials Prepared by Pyrolysis of a Mixture of Manila Hemp, Silicon Powder, and Flake Artificial Graphite for Lithium Batteries

A high performance lithium anode is a key component for high energy density lithium batteries. Silicon based lithium anode materials are attractive for the lithium anode due to their high theoretical capacity. However, a severe problem is the huge volume change that occurs during cycling, resulting in a poor capacity retention. We have developed a silicon based anode that disperses silicon particles on a carbon paper made from Manila hemp. The composite silicon electrode materials showed a high initial coulombic efficiency of 83%. The initial capacity of 566 mAh g−1 based on the total weight of the electrode was retained at 491 mAh g−1 after 70 cycles at the charge and discharge rate of 100 mA g−1 and at room temperature.

Enabling reliable lithium metal batteries by a bifunctional anionic electrolyte additive

Lithium metal has been considered as an attractive anode for high energy density lithium battery because of high specific capacity and the lowest redox potential. However, the growth of Li dendrites during cycling has hindered the practical application of Li metal battery (LMB). Herein, TTFEB is adopted as a bifunctional electrolyte additive to improve the performance of Li metal anode, which is beneficial for the surface chemistry of anode and the property of the electrolyte. A LiF-rich SEI layer and enhanced Li+ migration in electrolyte can be achieved with 2% TTFEB, which result in uniform Li deposition without uncontrollable Li dendrites. With controlled Li deposition in TTFEB-containing electrolyte, a significantly improved Coulombic efficiency (~ 96%) in Li|Cu cell, long lifetime (over 1000h), and weak polarization in Li|Li cell can be obtained. Moreover, excellent cycling performance and rate capability of Li|LiFePO4 cells with TTFEB are also presented in this work. Our strategy provides new insights on the diverse function of electrolyte additives for rechargeable LMB.

On Cell Variability and Fade Mechanisms in High Energy Density Lithium Batteries

Li-ion battery technology is approaching its limits in terms of capacity density and energy density based on current anode and cathode materials, which poses a technical challenge for increasing the range of electric vehicles and minimizing overall battery pack size. An alternative lithium battery technology utilizing a high capacity cathode such as a Ni-rich layered oxide can theoretically deliver an energy density upwards of 500 Wh/kg [1]. Combined with a lithium anode and a suitable liquid electrolyte, one such Nickel–rich layered oxide, LiNi0.6Mn0.2Co0.2O2 (NMC 622), has the theoretical potential to deliver batteries with an energy density of at least 500 Wh/kg [2, 3]. Here we have studied the performance of such high energy density full cells comprised of a Li metal anode, NMC622 cathode, and 1.2 M in LiPF6 (3:7) EC:EMC electrolyte. In order to better understand and compare the performance of different systems, a deep understanding of cell variability and its impact on fade mechanisms is necessary [4]. Hence, challenges in identifying true fade mechanisms due to cell variability will be discussed The presentation will cover the different fade mechanisms and their gradual progression as observed during cycling of these cells. Differential capacity analysis was applied to identify different fade mechanisms and to quantify degradation modes. The different fade mechanisms are related to variations in cells. Statistical analyses will be presented to characterize and quantify cell variability based on the different fade mechanisms observed.

The Role of Ionic Liquid Electrolytes in Li-S Batteries

Much attention is being paid to high-energy density lithium batteries such as lithium-sulfur (Li-S) battery because its specific energy density is much higher than those for commercialized lithium ion batteries [1]. However, many challenges including insulating properties of active materials, sluggish electrochemical reactions, and dissolution of the sulfur species into electrolyte remain unresolved for practical application. Electrolyte properties are essentially concerned with the above serious issues of these batteries. Undesirable side-reactions between electrolytes and the reduction products (lithium polysulfides, Li2Sm) occur in some non-aqueous electrolytes. The dissolution of the sulfur species, volatility, and flammability of electrolytes have also to be addressed for long-life operation of the Li-S cells. Therefore, development of electrolytes is a key to establishing these batteries [2]. We have determined saturated solubility of Li2Sm and S8 in various type of electrolytes ranging from molecular solvents to aprotic and solvate ionic liquids to study factors that govern the dissolution of S8 and Li2Sm species into electrolyte. In terms of solvent parameters, the solubility of Li2Sm was well correlated with Gutmann’s donor number, whereas solubility of S8 was explained by Hildebrand solubility parameter. Although weakly coordinating solvents having low donor number could greatly suppressed dissolution of Li2Sm, supporting lithium salts (e.g., LiTFSA) were hardly soluble in such weakly coordinating solvents. An exception was ionic liquid-based electrolytes: ionic liquids having a weakly coordinating anion can dissolve the supporting salt while suppressing dissolution of Li2Sm. We show how the electrolyte properties of the ionic liquids link to the cell performance such as large capacity, high Coulombic efficiency, and good reversibility. Reference [1] P. G. Bruce, S. A. Freunberger, L. J. Hardwick, and J-M. Tarascon, Nat. Mater., 11, 19 (2012). [2] M. Watanabe M. L. Thomas, S. Zhang, K. Ueno, T. Yasuda, K. Dokko, Chem. Rev., ASAP (2017).

Lithiophilic Cu–Ni core–shell nanowire network as a stable host for improving lithium anode performance

Lithium metal is long-term considered as a promising anode for high energy density lithium batteries. However, the practical application of lithium metal anode is hindered by the poor interfacial stability and lithium dendritic growth, which are originated from the relative infinite volume change of ‘hostless’ lithium metal anode. Here, we report a highly lithiophilic and stable Cu-Ni core-shell nanowires network host to accommodate the dramatic volume change of lithium and therefore improve the life-span of lithium metal anode. The Ni coating on the Cu nanowire endows the lithiophilic surface of the 3D network host facilitating the formation of the Li-Cu@Ni metallic nanocomposite anode via the facile infusion of molten lithium. The fabricated Li-Cu@Ni metallic anode shows superior electrochemical performance under galvanostatic cycling in the carbonate electrolyte, retaining flat voltage profiles over 500 cycles at a high current density of 3mAcm-2 with a low voltage polarization of 140mV. Furthermore, the Li-Cu@Ni based full cell coupled with the LiCoO2 cathode exhibited good rate capability (~ 90mAh/g at 5C) and cycling stability at 5C for 250 cycles (0.015% decay per cycle).

Chemically Coupled Conducting Complex Framework Materials (C4FMs) As Sulfur Hosts in Lithium – Sulfur Batteries

Ever increasing demand for efficient portable energy storage systems has directed researchers towards finding alternatives for the conventional insertion – based lithium-ion battery cathodes. Sulfur, with a theoretical specific capacity of 1672 mAh/g is a promising candidate for high energy density lithium battery cathodes1, 2. Low cost and ease of availability further adds to the advantages of sulfur over hitherto transition metal – based cathodes. However, elemental sulfur has very low electronic conductivity (~10-15 S/cm)3 at room temperature which restricts the active material utilization in Li – S battery. The formation of soluble non – intercalation based polysulfide intermediates (Li2Sn; n = 2 – 8)4 during electrochemical cycling further results in active material loss by coating onto the anode leading to eventual battery failure. Embedding sulfur into porous materials have shown considerable reduction in polysulfide dissolution by preventing direct contact with the liquid electrolyte5-7. However, inability to precisely control porosity and lack of chemical interaction between these porous structures and the entrapped sulfur greatly limits the efficiency of this approach. To completely prevent polysulfide dissolution, sulfur hosts with tunable, engineered porosity and increased affinity for polysulfide needs to be engineered. In this work, chemically coupled conductive complex framework materials (C4FMs) with nanoporous structure were used as hosts for sulfur in Li – S battery. Introduction of special functional groups improves the affinity of these structures towards polysulfide. The frameworks were synthesized using microwave assisted hydrothermal synthesis and then infiltrated with sulfur using vapor infiltration techniques. These sulfur – hosted cathodes showed a stable electrochemical performance with an initial discharge capacity of ~1620 mAh/g which stabilized at 1100 mAh/g to100 cycles (Figure 1). Acknowledgements: The authors acknowledge the financial support of DOE grant DE-EE 0006825, Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM).

Project “ Key technology and basic science problem reach for high energy density lithium batteries”

Project “ Key technology and basic science problem reach for high energy density lithium batteries”

Cathode Materials for High Energy Density Lithium Batteries

Two classes of cathode materials have been developed for high energy density applications. The Li-rich layered oxide material with the general formula Li1+xM1-xO2 (M = Ni, Mn, Co) and the lithium manganese silicate Li2MnSiO4. Both materials have theoretical capacities higher than commercialized ones, which may give rise to higher energy density batteries.

In Situ Generation of Poly (Vinylene Carbonate) Based Solid Electrolyte with Interfacial Stability for LiCoO2 Lithium Batteries.

Nowadays it is extremely urgent to seek high performance solid polymer electrolyte that possesses both interfacial stability toward lithium/graphitic anodes and high voltage cathodes for high energy density solid state batteries. Inspired by the positive interfacial effect of vinylene carbonate additive on solid electrolyte interface, a novel poly (vinylene carbonate) based solid polymer electrolyte is presented via a facile in situ polymerization process in this paper. It is manifested that poly (vinylene carbonate) based solid polymer electrolyte possess a superior electrochemical stability window up to 4.5 V versus Li/Li+ and considerable ionic conductivity of 9.82 × 10−5 S cm−1 at 50 °C. Moreover, it is demonstrated that high voltage LiCoO2/Li batteries using this solid polymer electrolyte display stable charge/discharge profiles, considerable rate capability, excellent cycling performance, and decent safety characteristic. It is believed that poly (vinylene carbonate) based electrolyte can be a very promising solid polymer electrolyte candidate for high energy density lithium batteries.

Electrochemical properties and optical transmission of high Li+ conducting LiSiPON electrolyte films

Lithium silicon phosphorus oxynitride (LiSiPON) thin films with different compositions have been prepared by RF magnetron sputtering in N2 by using three targets xLi2SiO3 · (1 − x) Li3PO4 with x = 0.1, 0.3, and 0.5. Compared with LiPON, the electrical properties of LiSiPON have been improved by introducing silicon. LiSiPON films deposited from the target 0.5Li2SiO3 · 0.5Li3PO4 yield the highest ionic conductivity of up to 9.7 × 10−6 S cm−1 with an activation energy of only 0.41 eV. The main mechanism for increasing ionic conductivity is the enhancement of carrier mobility. By DC polarization measurements the electronic partial conductivity was found at least seven orders of magnitude smaller than the ionic conductivity. Linear voltammetry results showed that the LiSiPON films are electrochemically stable in contact with stainless steel in the voltage range of 0–6 V. The substitution of silicon for phosphorus in the film evidenced from X‐ray photoelectron spectroscopy analysis indicated silicon in the film will create more abundant cross‐linking structures Si–O–P and (P, Si)–N < (P, Si), hence created more Li+ conducting paths which favored the higher mobility of lithium ions and larger ionic conductivity. The optical bandgap was found to decrease with increasing silicon content. We demonstrate that the prepared LiSiPON films with their larger ionic conductivity and low electronic conductivity may serve as an alternative to LiPON for applications in high energy density and high voltage lithium batteries.

Doped Lithium Orthosilicates - Promising High Rate Lithium-Ion Conductors for Li-S Batteries

There is an increased demand for portable energy storage systems that demonstrate high efficiency. The current Li – ion battery system based on Li – graphite insertion chemistry has a theoretical capacity of 372 mAh/g. For Li – ion batteries to be implemented in portable energy devices, specific capacities twice than that of the current system is necessary. Sulfur demonstrates a high theoretical specific capacity of 1672 mAh/g1 , 2, and is hence a promising candidate for high energy density lithium batteries. Moreover, sulfur is a low cost material and is easily available. Sulfur has very low conductivity (- 10-15 S/cm) which restricts the complete utilization of active material. Sulfur forms non – intercalation based polysulfide intermediates (Li2Sn ; n = 2 – 8)3which are soluble in liquid electrolyte resulting in loss of active material. In addition, the dissolved polysulfide gets coated onto the anode resulting in gradual cell voltage drop ultimately resulting in failure. These problems prevent the technology from being commercialized. Jampani et al. demonstrated reduced polysulfide dissolution and improved cycling stability by coating the sulfur cathodes with a lithium-ion conductor (LIC)4. The study identified Li4SiO4as a stable LIC. However, the application of this coating strategy is limited by the ionic conductivity of the LIC. In this work, the Li4SiO4 LIC was doped with dopants identified using first principles calculations by a high temperature solid state approach. The LIC was doped up to 5% without phase separation as represented in Figure 1. The doped LIC demonstrates a threefold increase in ionic conductivity as shown in Figure 2. This enhanced ionic conductivity is expected to improve the cycling stability of lithium-sulfur cathodes which will be discussed and presented in detail.

Flexible High Energy Density Silicon Composite Anode for Structural Batteries

The challenges of using high capacity metallic lithium foil as an anode for high energy density lithium battery are still remaining despite many years of research efforts, due to the intrinsic problems associated with the electrodeposition of reactive light metals such as lithium. In addition, the required excess lithium (3-5 times) to satisfy the battery long cycle life, and the safety concern associated with the large format cells containing metallic lithium anode have force the battery community to search for other alternatives. Some of the alternative anodes may exceed the energy density of metallic lithium when the excess lithium is considered. We will present a new class of composite anode material for structural and conformal lithium batteries. Our new composite anode is based on an optimized free-standing silicon coated carbon nanofiber in the form of flexible thin-paper with capacity exceeding 1500Ah/kg for the electrode including the carbon fiber and the silicon, and with high capacity retention during extensive charge-discharge cycles. The electrode/electrolyte interface and the silicon/carbon interface have been engineered to minimize the initial irreversibility during lithiation and delithiation, to less than 10%. In addition, the in-plan conductivity of the free standing composite anode has been optimized for high power battery application. We will report the performances of the silicon-carbon nanofiber composite anode in half cells and in full cells against high energy density lithium-rich layered oxide, and olivine based cathodes.

Structured electrolytes to suppress dendrite growth in high energy density batteries

Dendrite formation on the anode surface of high energy density lithium batteries is closely related to the safety and capacity of batteries; therefore, the suppression of dendrite growth could significantly improve battery performance and lifetime. Many reports demonstrate the close relation between local mass transport and dendrite growth, and most of the research focuses on improving the transport properties of isotropic electrolytes (electrolytes with a uniform diffusion coefficient). Recent research reveals strong dendrite suppression effects with anisotropic electrolytes which have a directional diffusivity; however applying anisotropic electrolytes to existing battery systems is challenging. In this paper we propose several hybrid structured electrolyte designs which can generate local non-uniform mass transport properties and induce dendrite suppression effects while still using conventional isotropic electrolytes. A numerical study is done to consider three hybrid electrolyte designs and shows that using a columnized solid structure with a typical isotropic liquid electrolyte can significantly suppress dendrite growth without sacrificing battery performance. The effects of the columnized hybrid electrolyte compare well with experimental data and suggest that through careful design of a columnar structure the benefits of an anisotropic electrolyte can be achieved without the need for developing new anisotropic liquid electrolytes. Copyright © 2016 John Wiley & Sons, Ltd.

Highly Ordered Complex Framework Materials (CFMs) As Sulfur Hosts for Li-S Batteries

In recent years, there is a near exponential increase in the number of plug – in hybrid vehicles and portable energy storage devices. This results in an increased demand for portable energy storage devices with greater efficiency. The commercial Li – ion batteries based on lithiation chemistry has a maximum theoretical capacity of 372 mAh/g could not meet this ever increasing demand. Thus the need of the hour is to find new materials and hybrids with improved energy storage capacity. Sulfur with a theoretical specific capacity of 1672 mAh/g1 , 2 is a promising candidate for high energy density lithium batteries. Sulfur being one of the abundant elements on the Earth’s crust adds advantages as a low cost and environmentally benign promising technology3. Despite these advantages, sulfur has very low conductivity (- 10-30 S/cm) which restricts the complete utilization of the active material. Sulfur forms non – intercalation based polysulfide intermediates (Li2Sn ; n = 2 – 8)4which are soluble in liquid electrolyte resulting in active material loss. In addition, the dissolved polysulfide gets coated onto the anode resulting in cell failure. These problems prevents the technology from being commercialized. Utilizing mesoporous5 and hollow carbonaceous materials6 , 7as sulfur hosts has shown to reduce polysulfide dissolution by avoiding direct contact with the liquid electrolyte. However, the pore size of these materials are in the order of µm and hence the problem of polysulfide dissolution has not been completely addressed. Porous materials with pore size comparable or less than the size of the polysulfide is required to completely overcome this problem. In this work, highly ordered complex framework materials (CFM) were used as hosts for sulfur. These nano porous hosts trap the polysulfides formed during lithiation of sulfur and thus prevent active material loss with cycling. Two variants of the host were synthesized at room temperature and sulfur was infiltrated into them using infiltration techniques. These sulfur impregnated CFM cathodes showed a stable electrochemical performance with an initial discharge capacity of 1476 mAh/g which stabilized at 609 mAh/g for over 200 cycles (Figure 1). Results of these studies are presented and discussed.

Investigating the Effects of Anisotropic Mass Transport on Dendrite Growth in High Energy Density Lithium Batteries

Dendrite formation on the electrode surface of high energy density lithium (Li) batteries causes safety problems and limits their applications. Suppressing dendrite growth could significantly improve Li battery performance. Dendrite growth and morphology is a function of the cation concentration gradient in the electrolyte near the anode interface. Most research into dendrites in batteries focuses on dendrite formation in isotropic electrolytes (i.e., electrolytes with an isotropic diffusion coefficient). In this work, an anisotropic diffusion reaction model is developed to study the anisotropic mass transport effect on dendrite growth in Li batteries. The model uses a Lagrangian particle-based method to model dendrite growth in an anisotropic electrolyte solution. The model is verified by comparing the numerical simulation results with analytical solutions, and its accuracy is shown to be better than previous particle-based anisotropic diffusion models. Several parametric studies of dendrite growth in an anisotropic electrolyte are performed and the results demonstrate the effects of anisotropic transport on dendrite growth and morphology, and show the possible advantages of anisotropic electrolytes for dendrite suppression.

Effective Suppression of Dendritic Lithium Growth Using an Ultrathin Coating of Nitrogen and Sulfur Codoped Graphene Nanosheets on Polymer Separator for Lithium Metal Batteries.

The enhanced stability of lithium metal is vital to the development of high energy density lithium batteries due to its higher specific capacity and low redox potential. Herein, we demonstrate that nitrogen and sulfur codoped graphene (NSG) nanosheets coated on a polyethylene separator stabilized the lithium electrode in lithium metal batteries by effectively suppressing dendrite growth and maintaining a uniform ionic flux on the metal surface. The ultrathin layer of NSG nanosheets also improved the dimensional stability of the polymer separator at elevated temperatures. In addition, the enhanced interfacial interaction between the NSG-coated separator and lithium metal via electrostatic attraction released the surface tension of lithium metal and suppressed the initiation of dendrite growth on lithium metal. As a result, the electrochemical performance of a lithium metal cell composed of a LiNi0.8Co0.15Al0.05O2 positive electrode with an NSG-coated separator was remarkably improved as compared to the cell with an uncoated polyethylene separator.

Investigating the Effects of Transport and Mixing on Dendrite Growth in High Energy Density Lithium Batteries

High Energy density lithium (Li) batteries are promising advanced energy technologies for applications in the automotive and portable power markets. Advanced Li batteries have several design and operational challenges to overcome before becoming commercially viable. One of these challenges is the formation of dendrites on the anode surface of the Li-air battery over multiple charge and discharge cycles. Dendrite formation decreases cell performance and causes safety concerns due to short circuiting. In this research computational methods are adopted to investigate the physics of dendrite formation in Li-air batteries and to develop strategies to suppress dendrite growth. The effects of convection and anisotropic transport properties in the electrolyte on the morphology and growth rate of dendrites are investigated using a two-dimensional (2D) smoothed particle hydrodynamics (SPH) model. SPH is a mesh-free Lagrangian computational fluid dynamics method, which allows for easy implementation of complex physics at the dendrite surface. Anisotropic diffusion is modeled to study the effects of mixing near the anode-electrolyte interface on dendrite growth. The simulation results suggest that high anisotropy in the electrolyte promotes a robust, compact dendrite structure versus isotropic diffusion cases. Convection effects are also considered to study the electro-osmosis effect on dendrite growth. Circulating flows are included in the model to simulate electro-osmotic flows near the anode-electrolyte interface. The simulation results reveal that the convection effect will increase the mixing near the dendrite and lead to significant changes in dendrite morphology. The results of these computational studies are being used to develop mitigation strategies for dendrite growth in Li-air batteries. These strategies include the use of novel electrolyte solutions and hybrid electrolyte designs, which allow for the tuning of transport properties through the electrolyte. The computational models are being used to investigate these designs and optimize material properties to increase battery performance and lifetime. Figure 1

A Polypyrrole Hollow Sphere@Se Cathode for Rechargeable Lithium Batteries

The exploration of new electrode materials is indispensable for lithium ion batteries. Selenium, belonging to the same group as sulfur and with a high specific theoretical capacity of 675 Ah/kg or 3253 Ah/m3 was first demonstrated as a candidate of cathode material for lithium and sodium rechargeable batteries by Abouimrane et al.(1). Li-Se batteries are supposed to possess a large volumetric energy density that is of greater importance than gravimetric energy density in terms of lightweight and portability of batteries. Moreover, selenium exhibits a quite high intrinsic electronic conductivity (1×10-3 S/m) that is approximately 20 orders of magnitude greater than sulfur(1, 2), which could afford Se better electrochemical activity and better rate capability.Nevertheless, the shuttle effect in Li-Se system remains to be a problem that deteriorates the cycle performance due to the dissolution of polyselenide species in electrolyte. Here, we designed a novel polypyrrole(PPy) hollow sphere@Se composite, in which Se was confined in PPy hollow microspheres. Thus, the loss of active material and capacity fading was effectively suppressed.Polypyrrole(PPy) hollow spheres were synthesized via a multi-step templating method. The PPy hollow sphere@Se composite was prepared by a melt-diffusion approach with a mixture of selenium and PPy hollow spheres in a certain weight ratio under vacuum.The morphology of prepared PPy hollow spheres is shown in figure 1a and b. The hollow microspheres are self-assembled by smaller polypyrrole particles, with an approximate diameter of 300nm. The hollow PPy spheres with good shape and dispersibility are demonstrated. A part of selenium is infiltrated into the hollow spheres as shown in figure 1c. Figure 1. a) SEM image of PPy hollow spheres; TEM images of b) PPy hollow spheres and c) PPy hollow sphere@Se. d) Cycling performance and coulombic efficiency of PPy hollow sphere@Se and pristine Se; e) Nyquist plots of Li-PPy@Se and Li-Se cells after 50 cycles with 1M LiTFSI plus 0.1M LiNO3 in DOL/DME as electrolyte.Figure 1d compares the specific discharge capacity and coulombic efficiency of PPy hollow sphere@Se and pristine Se at 0.1C rate. Pristine Se cathode presents rather poor cycling stability with a low reversible capacity of less than 40 mAh/g after 50 cycles. The severe capacity fading is ascribed to the shuttle effect with dissolution of polyselenide species generated during discharging process which also results in lower coulombic efficiency. By contrast, a specific discharge capacity of 250mAh/g is obtained for PPy hollow sphere@Se electrode after 50 cycles. Moreover, the coulombic efficiency almost reaches 100%, indicating that the shuttle effect has been inhibited effectively by the hollow structure of the PPy matrix.Electrochemical impedance spectroscopy (EIS) provides further evidence for its superior cyclability as figure 1e indicates. The data show that both the electrolyte resistance Re and the charge transfer resistance Rct reduce when pristine Se is substituted by PPy hollow sphere@Se for cathode. Especially the value of Rct in Li-PPy@Se cell obviously decreases to just 40% of the one for Li-Se cell. The reduction of resistances is proposed to be owing to the restriction of the discharge products inside the hollow spheres and less shuttle effect which could also corrode the surface of lithium metal electrode. From the above, selenium cathode has great potential for the development of high energy density lithium batteries and PPy hollow sphere@Se composite is a favorable cathode in Li-Se system.

A Solid-State Single-Ion Conductor for Lithium Batteries Based on Anionic Nanoparticles of Fluorinated Titania

Nowadays, among the most challenging classes of materials for the development of high-energy density lithium batteries are electrolytes and high-capacity cathode materials [1]. A considerable interest is attracted by metallic lithium anode-based Li-S and Li-air batteries because of their high specific capacity [2]. Nevertheless, the use of a metallic lithium anode compromises the chemical and electrochemical stability of the electrolyte. To address these drawbacks, a significant research effort is recently devoted to the design and preparation of new lithium-conducting electrolytes. Here, a new concept of electrolyte based on a solid-state lithium single-ion conductor is proposed, which opens new perspectives in the development of advanced lithium batteries [3]. The electrolyte is obtained by direct reaction of nanometric fluorinated TiO2 (FT) with molten metallic lithium, and consists of nanoparticles (NPs) with surface anionic groups neutralized by lithium cations. The resulting nanopowder is labelled LiFT® [4]. It should be highlighted that after functionalization, the conductivity of fluorinated TiO2 increases by more than four orders of magnitude. In this work, the structure of LiFT is elucidated by means of several techniques such as: Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES); High-Resolution Transmission Electron Microscopy (HR-TEM), powder X-Ray Diffraction (XRD), Infrared Spectroscopy (FT-MIR and -FIR), electrochemical measurements and solid-state Magic-Angle Spinning-NMR (MAS-NMR) spectroscopy. XRD and HR-TEM measurements show that LiFT has the “core” structure of anatase, with Li cations present only in the external lithium-rich shell of NPs. Thus, no intercalation processes of Li+ in “core” LiFT NPs take place. In addition, it is demonstrated that lithium cations can migrate through grain boundaries of electrolyte NPs in a very effective way, achieving: 1) a room-temperature single-ion conductivity of about 3x10-4 Scm-1; 2) an excellent electrochemical stability; and 3) a high exchange current density. All these features, together with an easy synthesis process, which is based on precursors obtained from very cheap starting materials, make LiFT a very attractive material for application in several fields such as: a) all-solid-state lithium batteries; b) molten electrode lithium batteries; c) nanocomposite electrolytes and d) lithium-air batteries.[1] M. Armand, J.-M. Tarascon, Building better batteries, Nature. 451 (2008) 652–657.[2] P.G. Bruce, S.A. Freunberger, L.J. Hardwick, J.-M. Tarascon, Li-O2 and Li-S batteries with high energy storage., Nat. Mater. 11 (2012) 19–29.[3] F. Bertasi, K. Vezzù, E. Negro, S. Greenbaum, V. Di Noto, Single-ion-conducting nanocomposite polymer electrolytes based on PEG400 and anionic nanoparticles: Part 1. Synthesis, structure and properties, Int. J. Hydrogen Energy. (2013).[4] V. Di Noto, F. Bertasi, E. Negro, M. Piga, M. Bettiol, F. Bassetto, Solid-state electrolytes based on fluorine-doped oxides, PCT/IB2012/053542, 2013.

Design and Fabrication of High Energy Density Lithium Battery

Rechargeable LIBs have been widely used in many portable consumer electronics. They presently have limited acceptance in larger energy storage markets, e.g., plug-in hybrid and electrical vehicles due to several issues, including 1) low energy density or power density, 2) poor cycling stability, 3) safety concerns about lithium-ion batteries.EC Power has been working on development of novel polymer-carbon nanocomposite cathode materials to demonstrate high energy/power Li-ion batteries using the electrode materials. A series of polymers with electrochemically active functional groups have been synthesized, characterized, and fabricated as cathode for lithium batteries. The polymer cathode has showed high capacity up to 250mAh/g and the long cycling performance up to 500 cycles. Compared to the traditional cathode materials, the polymer cathode materials not only have high specific capacity, but also are potentially low-cost and recyclable.In order to study the degradation of the battery cells, EC Power also designed and fabricated 3-electrode cells. With the lithium reference, we are able to test and observe the voltage profile of cathode, anode and the full cell, respectively. Thus we will be able to study the degradation behavior of the cathode and anode respectively in the full cell environment. The degradation behavior of cathode and anode in a full cell is different from that in a half-cell. The study help us to understand the kinetics of full cell chemistry, target the control step in degradation and thus to mitigate the degradation.In this presentation, we will also demonstrate several complimentary methods for fabrication of commercially viable size cells of the Li-polymer and conventional Li-ion batteries with the process much faster and cost-effective. With the EC Power’s proprietary cell design software, which gives us a very reasonable starting point for expected cell performance upon cell fabrication, EC Power has successfully fabricated different types of cells.