Thin-film Rechargeable Batteries Research Articles

Monolithic All-Solid-State High-Voltage Li-Metal Thin-Film Rechargeable Battery.

The substitution of an organic liquid electrolyte with lithium-conducting solid materials is a promising approach to overcome the limitations associated with conventional lithium-ion batteries. These constraints include a reduced electrochemical stability window, high toxicity, flammability, and the formation of lithium dendrites. In this way, all-solid-state batteries present themselves as ideal candidates for improving energy density, environmental friendliness, and safety. In particular, all-solid-state configurations allow the introduction of compact, lightweight, high-energy-density batteries, suitable for low-power applications, known as thin-film batteries. Moreover, solid electrolytes typically offer wide electrochemical stability windows, enabling the integration of high-voltage cathodes and permitting the fabrication of higher-energy-density batteries. A high-voltage, all-solid-state lithium-ion thin-film battery composed of LiNi0.5Mn1.5O4 cathode, a LiPON solid electrolyte, and a lithium metal anode has been deposited layer by layer on low-cost stainless-steel current collector substrates. The structural and electrochemical properties of each electroactive component of the battery had been analyzed separately prior to the full cell implementation. In addition to a study of the internal solid–solid interface, comparing them was done with two similar cells assembled using conventional lithium foil, one with thin-film solid electrolyte and another one with thin-film solid electrolyte plus a droplet of LP30 liquid electrolyte. The thin-film all-solid state cell developed in this work delivered 80.5 mAh g–1 in the first cycle at C/20 and after a C-rate test of 25 cycles at C/10, C/5, C/2, and 1C and stabilized its capacity at around 70 mAh g–1 for another 12 cycles prior to the start of its degradation. This cell reached gravimetric and volumetric energy densities of 333 Wh kg–1 and 1,212 Wh l–1, respectively. Overall, this cell showed a better performance than its counterparts assembled with Li foil, highlighting the importance of the battery interface control.

Rechargeable Batteries with 100% Cathode Active Materials─Conductive Vapor-Deposited Films of a Stable Organic Neutral Radical

Organic cathode active materials have been developed as promising alternatives to inorganic materials for rechargeable batteries due to environmental sustainability. However, the electrically insulating feature of organic materials causes the limitation in the capacity of the whole device, where the cathode requires massive conductive carbons. In this paper, we have realized rechargeable batteries with a cathode of 100% organic active material using highly conductive vapor-deposited films of 4,8,12-trioxotriangulene (TOT) neutral radical. These cathodes contained neither a binder nor a conductive additive and showed high capacities close to the theoretical value of the active material. The face-on films had better rate and cycle characteristics in comparison with the edge-on film due to their anisotropic conductivities. The films of ∼3 μm thickness maintained the face-on orientation and high capacities close to the theoretical value. The battery characteristics of highly oriented vapor-deposited films of TOT will provide a new promising strategy for the development of flexible, high-capacity thin-film rechargeable batteries.

3D Printable Ionogels with High Ionic Conductivity

Hybrid materials based on ionic or polymer components are very useful in electrochemical devices like battery systems or fuel cells due to their unique properties like thermal and electrochemical stability and polarity. For all advances over the past, lithium ion based materials are still costly, limited and not very stable. Currently, solid-state polymer electrolytes (SPEs) and gel polymer electrolytes (GPEs) [1] have ion conductivities below 10-4 S/cm at room temperature.Polymer electrolytes can be established by ionic liquids (ILs) which combine beneficial properties like high ionic conductivity, wide electrochemical potential window and high viscosity. These kinds of electrolytes can be very beneficial in solid-state batteries for example. This technology has garnered immense excitement from investors and large corporations. The main advantage of all-solid-state to liquid electrolyte-based batteries is that the size can be easily made smaller e.g. solid‐state electrolytes have a typical thickness of approximately 1.0 μm, whereas the separator in liquid electrolyte‐based cells typically has a thickness of 20 μm. Several investigators are exploring 3D architectures for thin-film rechargeable battery electrodes. Nevertheless additive manufacturing, also known as 3D printing, could revolutionize the structural properties of batteries. In addition, this technology could improve the adaptability of the electrolyte to the electrodes.This scientific approach introduces the possibility to combine ionic liquids with a commercial photoreactive resin to realise a well-defined structure by using stereolithography (SLA). This provides, for the first time, access to ionogels (IGs) with complex 3D shapes (figure 1a) with potential application in battery or fuel cell technology. For first experiments new IGs were prepared by adding a series of sulfonate-based ionic liquids (ILs), 1-methyl-3-(4-sulfobutyl)imidazolium para-toluenesulfonate [BmimSO3H][pTS], 1-methyl-1-butylpiperidiniumsulfonate para-toluenesulfonate [BmpipSO3][pTS], and 1-methyl-3-(4-sulfobutyl) imidazolium methylsulfonate [BmimSO3H][MeSO3] with a clear photoreactive resin which were used in a Form 2 3D printer [2]. Moreover, the IGs are thermally stable up to about 200 °C and mechanically robust. In addition to this synthesized protic conductive IGs, sulfobataine, metal and lanthanides containing IGs were prepared and analysed. These IGs exhibit higher conductivities compared to the sulfonated based IGs in the range from 10-4 to 10-2 S/cm at room temperature. 3D Printable metal-lanthanide IGs could possibly be an adequate replacement for lithium-ion electrolytes. Figure 1: a) Well-defined structures of IGs by SLA, b) Rhd battery cell for electrochemical measurements. Literature: [1] Stephan, A.M., Review on gel polymer electrolytes for lithium batteries. European polymer journal, 2006. 42(1): p. 21-42. [2] Zehbe, K.; Lange,A.; Taubert, A., Stereolithography provides access to 3D printed ionogels with high ionic conductivity, Energy and Fuels, accepted. Figure 1

Fe-induced layer exchange of multilayer graphene for rechargeable battery anodes

Multilayer graphene (MLG) is a promising material for anodes of next-generation thin-film rechargeable batteries. The inverted layer exchange using an Fe catalyst allowed for the low-temperature (600 °C) self-organization of the anode electrode structure, that is, an active material (MLG) on a current collector (Fe). A coin-type cell, fabricated from the MLG electrode and pure Li metal foil, showed distinct peaks, indicating Li intercalation into the MLG in a cyclic voltammogram. After 100 charge/discharge cycles, the capacity was 3.3 μAh cm−2 and coulombic efficiency was 98%. The low-temperature synthesis of a MLG anode structure and its operation were demonstrated.

Development and Novel Characterization of All-Solid-State Thin Film Batteries

All-solid-state batteries are looked to for their high energy density and reduced capacity fade, and are a safer alternative to the conventional liquid electrolyte batteries currently being manufactured. However, few solid electrolytes are currently known. Amorphous lithium phosphorus oxynitride (LiPON) is a well-established solid electrolyte and is currently the only viable solid-state electrolyte for thin film batteries. LiPON is stable in contact with Li metal, but exhibits a relatively low ionic conductivity (10-6 S/cm2) [1]. A variety of other solid electrolytes with higher ionic conductivities are currently being explored, such as lithium lanthanum titanate (LLTO), achieving high lattice ionic conductivity of >10-3 S/cm2 [2]. We aim to enable LLTO as an electrolyte for thin film batteries via pulsed laser deposition. Additionally, performance of all-solid-state batteries is largely influenced by interfacial impedance and phase evolution during charge and discharge. The thin film geometry provides an ideal platform for analyzing the various electrode/electrolyte interfaces. Using novel focused ion beam and dynamic in situ transmission electron microscopy techniques, we have fabricated electrochemically active nanobatteries and observed their cycling behavior in situ. These techniques have been demonstrated on the layered lithium cobalt oxide (LCO)/LiPON interface, elucidating the mechanism of interfacial impedance which was previously unknown via ex-situ cycling experiments [3]. [1] N.J. Dudney, “Solid-state thin film rechargeable batteries,” Materials Science and Engineering: B, 116 (2005) 245-249. [2] O. Bohnke, “The fast lithium-ion conducting oxides Li3xLa2/3 − xTiO3 from fundamentals to application,” Solid State Ionics, 179 (2008) 9-15. [3] Z. Wang, D. Santhanagopalan, W. Zhang, F. Wang, H. Xin, K. He, J. Li, N. Dudney and Y.S. Meng, “In situ STEM/EELS Observation of Nanoscale Interfacial Phenomena in All-Solid-State Batteries,” Submitted.

Optical Properties and Electrochemical Performance of LiFePO4 Thin Films Deposited on Transparent Current Collectors.

LiFePO4 thin film cathodes are deposited on various transparent conducting oxide thin films on glass, which are used as cathode current collectors. The XRD patterns show that the thin films have the phase of LiFePO4 with an ordered olivine structure indexed to the orthorhombic Pmna space group. LiFePO4 thin film deposited on various TCO glass substrates exhibits transmittance of about 53%. The initial specific discharge capacities of LiFePO4 thin films are 25.0 μAh/cm2 x μm on FTO, 33.0 μAh/cm2 x μm on ITO, and 13.0 μAh/cm2 x μm on AZO coated glass substrates. Interestingly, the retention capacities of LiFePO4 thin films are 76.0% on FTO, 31.2% on ITO, and 37.7% on AZO coated glass substrates at 20th cycle. The initial specific discharge capacity of the LiFePO4/FTO electrode is slightly lower, but the discharge capacities of the LiFePO4/FTO electrode relatively decrease less than those of the others such as LiFePO4/ITO and LiFePO4/AZO with cycling. The results reported here provide the high transparency of LiFePO4 thin films cathode materials and the good candidate as FTO current collector of the LiFePO4 thin film cathode of transparent thin film rechargeable batteries due to its high transparency and cyclic retention.

Energy Storage in crystalline Materials based on multivalent Ions

Energy conversion and storage has become the main challenge to satisfy the growing demand for renewable energy solutions as well as mobile applications. Nowadays, several technologies exist for the conversion of electric energy into e. g. heat, light and motion or vice versa. Among a large variety of storage concepts, the conversion of electrical in chemical energy is of great relevance in particular for location-independent use. Main factors that still limit the use of electrochemical cells are the volumetric and gravimetric energy density, cyclability as well as safety. The concept for a new thin-film rechargeable battery that possibly improves these properties is presented. In contrast to the widespread lithium-ion technology, the discussed battery is based on the redox reaction of multivalent Al-ions and their migration through solid electrolytes. The ion conduction and insertion processes in the crystalline materials of the suggested cell are discussed under a crystallographic point of view to identify suitable electrode and separator materials. A multilayer-stack of all-solid-state batteries is synthesized by pulsed laser deposition and investigated in situ, i. e. during charge and discharge, by X-ray reflection and diffraction methods. The correlation between crystal structure, morphology and electrical performance is investigated in order to characterize the ion diffusion and insertion process.

First Principles Study on the Electrochemical, Thermal and Mechanical Properties of LiCoO2 for Thin Film Rechargeable Battery

Thin film rechargeable battery has become a research hotspot because of its small size and high energy density. Lithium cobalt oxide as a typical cathode material in classical lithium ion batteries is also widely used in thin film rechargeable batteries. In this work, the electrochemical, mechanical and thermal properties of LiCoO2 were systematically investigated using the first principles method. Elastic constants under hydrostatic pressures between 0 to 40GPa were computed. Specific heat and Debye temperature at low temperature were discussed. Thermal conductivity was obtained using the imposed-flux method. The results show good agreements with experimental data and computational results in literature.

Integrated Thin-Film Rechargeable Battery on α-Si Thin-Film Solar Cell

In this paper we reported on fabrication and characterization of a composite harvesting device integrated thin-film rechargeable battery on α-Si thin-film solar cell. The α-Si thin-film solar cell typically presented open-circuit voltage of 4.3 V, short-circuit current of 15.4 mA/cm2 and efficiency of 7.4%. The thin-film rechargeable battery composed of Nb2O5/LiPON/LiMn2O4 systems fabricated using dry process, which showed the initial discharge capacity of about 215 μAh (or 12.4 μAh/cm2), the cycleabilty for discharge was good at keeping about 12.3 μAh/cm2 with a small decreasing ratio of 0.1% per cycle and the coulombic efficiency was all over 95% for the 100 cycles. On the other hand, the discharge capacity of approximately 80% was provided by the self-charging of the solar cell for 10 min, and the coulombic efficiency was also over 95%.

A thin-film rechargeable battery for integration in stand-alone microsystems

Thin-film solid-state rechargeable batteries on silicon are ideal power sources for microsystems applications, where a high level of integration is required. This paper presents a lithium solid-state thin-film battery for integration in stand-alone microsystems. The thin-films were deposited by direct current (DC) and radio-frequency (RF) reactive sputtering techniques. The materials of the battery includes SnO2, Li3PO4N and LiCoO2 as anode, electrolyte and cathode, respectively. The SnO2 gives the battery a maximum storage capacity of 781 mAhg−1, the LiCoO2 can maintain a capacity of 140 mAhg−1. The two materials used as anode and cathode with the Li3PO4N as electrolyte can obtain an output voltage in the range 3-4.2 V.

Solid-state thin-film rechargeable batteries

Thin-film solid-state rechargeable lithium batteries are ideal micropower sources for many applications requiring high energy and power densities, good capacity retention for thousands of discharge/charge cycles, and an extremely low self-discharge rate. Batteries fabricated using the crystalline LiCoO 2 cathode consistently provide the maximum power levels up to 30 mW/cm 2, long cycle life, negligible self-discharge and rapid charge rates. Similarly promising results have also been obtained with crystalline LiMn 2O 4 cathodes, although good reproducibility has not been achieved. These fully lithiated cathodes can be used with Li-free or Li-ion thin-film anodes to produce batteries that can withstand high temperature solder bonding processes.

Thin-film rechargeable lithium batteries

Thin-film rechargeable batteries with a lithium metal anode, an amorphous inorganic electrolyte, and cathodes of amorphous V 2O 5 and crystalline and amorphous Li x Mn 2O 4 have been fabricated and characterized. The performance of the thin-film cells was evaluated at different current densities and, in the case of Li V 5, at several temperatures. Electrical measurements show that the current density of the thin-film cells is limited by the lithium-ion mobility in the cathodes. The resistance of Li Li x Mn 2O 4 cells with crystalline cathodes is about two orders of magnitude lower than that of Li V 5 cells with amorphous cathodes.

Thin Film Fuel Cells

AbstractIn recent years there has been an enormous increase in the application of thin film technologies in the fabrication of solid state electrochemical devices. Devices in which thin film components are utilized are,e.g.solid oxide fuel cells (SOFCs), thin film rechargeable batteries, and chemical gas sensors. Chemical vapour deposition (CVD) is one of the synthesis techniques for the fabrication of thin film components for solid state electrochemical devices. This paper will focus on the application of novel CVD techniques for the fabrication of the thin film components of one of these devices,i.e.the solid oxide fuel cell. A new SOFC design concept which uses only one gas phase synthesis method will be presented.

Properties of a Carbon Negative Electrode in Completely Inorganic Thin Film Li-Ion Batteries with a LiCoO2 Positive Electrode

AbstractCompletely inorganic thin film lithium ion battery cells have been prepared by vapor deposition processes (vacuum evaporation and sputtering). The negative and positive electrodes were films of disordered carbon and lithium cobalt oxide, respectively. The results of battery charging/discharging and other measurements (e.g., in-situ lithium chemical diffusion constant measurements for the carbon films) indicate that disordered carbon films have a relatively high reversible charge capacity, (> 160 mC/μmand possibly higher than 360 mC/cm2-μm, or > 296 and possibly 667 mAh/g, respectively, assuming the measured film density of 1.5g/cm3), and a lithium chemical diffusion constant at room temperature ≈10-9 cm2/s. These results suggest that disordered carbon films should be good substitutes for metallic lithium in thin film rechargeable batteries.

A monolithic thin-film electrochromic window

Three closely related thin-film solid-state ionic devices that are potentially important for applications are: electrochromic smart windows, high-energy density thin-film rechargeable batteries, and thin-film electrochemical sensors. Each usually has at least one mixed ion/electron conductor, an electron-blocking ion conductor, and an ion-blocking electron conductor; and many of the technical issues associated with thin-film solid-state ionics are common to all three devices. Since the electrochromic window has the added technical requirement of electrically controlled optical modulation (over the solar spectrum), and since research at the authors' institution has focused primarily on the window structure, this paper will address the electrochromic window, and particularly a monolithic variable-reflectivity electrochromic window, as an illustrative example of some of the challenges and opportunities that are confronting the thin-film solid-state ionics community.

ChemInform Abstract: Prussian Blue Containing Nafion Composite Film as Rechargeable Battery.

AbstractA solid‐state thin film rechargeable battery has been prepared using a novel efficient technique of "surface complexation method" by which a thin layer of Prussian Blue (PB) can be coated on a solid polymer electrolyte of Nafion (Nf) as matrix.

Prussian Blue Containing Nafion Composite Film as Rechargeable Battery

A solid‐state thin film rechargeable battery has been prepared using a novel efficient technique of “surface complexation method” by which a thin layer of Prussian blue (PB) can be overlaid on a solid polymer electrolyte of Nafion (Nf) as matrix. An electrochemical cell made of the composite PB‐Nf film sandwiched with supporting electrodes was examined on i‐V curves in solid state and for characteristics as a rechargeable battery. The resulting PB‐Nf battery showed good durability in repetitive cycles of charging and discharging and gave the following results: open‐circuit voltage of the unit cell per 160 μm 0.68V, short‐circuit current 0.2–2 mA/cm2 depending upon the water content of the Nf matrix, and an energy density of about 50 Wh/kg.