Thin-Film Solid Electrolytes

Thin-film solid electrolytes in the range of Ipm have the advantage that the material which is inactive for energy storage is minimized and the resistance of the solid electrolyte film is drastically decreased for geometrical reasons. This allows the application of a large variety of solid electrolytes which exhibit quite poor ionic conductivity but high thermodynamic stability. The most important thin-film preparation methods for solid electrolytes are briefly summarized below. 

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Fabrication techniques, especially the preparation of thin films of functional materials, have made major progress in recent years. Thin-film solid electrolytes in the range of several nanometers up to several micrometers have been prepared successfully. The most important reason for the development of thin-film electrolytes is the reduction in the ionic resistance, but there is also the advantage of the formation of amorphous materials with stoichiometries which cannot be achieved by conventional techniques of forming crystalline compounds. It has often been observed that thin-film electrolytes produced by vacuum evaporation or sputtering provide a struc-... 

Electronic conductivity of thin-film solid electrolytes. Besides having low electronic transference numbers, it is essential for thin films of the order of 1 jim that the magnitude of the electronic resistance is low in order to prevent self-discharge of the battery. For this reason, specific electronic resistances in the range of 1012-1014 Qcm are required for thin-film solid electrolytes. Often the color may be a valuable indication of the electronic conductivity. In this regard, solid electrolytes should preferably be transparent white [20]. 

Direct-current sputtering is not generally applicable for the preparation of thin-film solid electrolytes since these compounds are electronic insulators. The target surface would be charged with the same polarity as that of the ions in the plasma, and the sputtering plasma would rapidly break down. 

Kanehori K, Matsumoto K, Miyauchi K, Kudo T (1983) Thin film solid electrolyte and its application to secondary Lithium cell. Solid State Ionics 9-10 1445-1448 Py MA, Haering RR (1983) Structural destabilization induced by lithium intercalation in M0S2 and related compounds. Can J Phys 61 76-84... 

Cairns EJ, Shimotake H (1969) High-temperature batteries. Science 164 1347-1355 Kennedy JH (1977) Thin film solid electrolyte systems. Thin Solid Films 43 41-92 Linford RG (1988) Apphcations of solid state ionics for batteries. Solid State Ionics 28-30 831-840... 

Kennedy, I.H., Thin films solid electrolyte systems. Thin Solid Films 43 (1977) 41-92. Skliar, M. and Tathireddy, R, Approximation of evolutional system using singular forcing, Comput. Chem. Eng. 26 (2002) 1013—1021. 

Wang B., Greenblatt M., Yan J., Wu Y. Sol-gel derived (LiCl)2-Al203-Si02 thin film solid electrolyte. 

Fabrication techniques, especially the preparation of thin films of functional materials, have made major progress in recent years. Thin-film solid electrolytes in the range of several nanometers up to several micrometers have been prepared successfully. The most important reason for the development of thin-fihn... 

Leng YJ, Chan SH, Khor KA, and Jiang SP. Performance evaluation of anode-supported solid oxide fuel cells with thin-film YSZ electrolyte. Int J Hydrogen Energy 2004 29 1025-1033. 

Yan, J.W., Lu, Z.G., Jiang, Y., Dong, Y.L., Yu, C.Y., and Li, W.Z., Fabrication and testing of a doped lanthanum gallate electrolyte thin-film solid oxide fuel cell. Journal of the Electrochemical Society, 2002, 149, A1132-A1135. 

The last few years have witnessed a high level of activity pertaining to the research and development of all-solid, thin-film polymer electrolyte batteries most of these use lithium as the active anode material, polymer-based matrices as solid electrolytes, and insertion compounds as active cathode materials. High-performance prototypes of such batteries stand currently under research, whose trends are expected to include the development of amorphous polymers with very low glass-transition temperatures, mixed polymer electrolytes, and fast-ion conductors in which the cationic transport number approaches unity. 

Ranran P, Yan W, Lizhai Y and Zongqiang M (2006), Electrochemical properties of intermediate-temperature SOFCs based on proton conducting Sm-doped BaCeOj electrolyte thin film . Solid State Ionics, 177,389-393. 

The absence of solvents in such solid-polymer-electrolyte photovoltaic cells presents the possibility of fabricating corrosion-free systems. The thin-film solid-state cells also allow fabrication of multispectral cells composed of more than one semiconductor in optical and electrical series. A solid-state photovoltaic cell, n-Si/Pt/PP/PEO(K.I/ l2)/Pt/ITO, was studied. The surface modifications of n-Si with PP can dramatically reduce the large activation energy barrier against efficient charge transfer between semiconductor and polymer-solid electrolyte. The efficiency of this cell is limited by a high surface recombination velocity associated with surface states of the n-Si. The cell had V = 225 mV and 11 niA cm at 100 mW cm illumination with junction ideality factor of 1.5. This implies the existence of deleterious surface states acting as recombination centres. 

J.B. Bates, N.J. Dudney, G.R. Gmzalsld, R.A. Zuhr,A. Choudhury, C.F. Luck,J.D. Robertson, Electrical properties of amorphous lithium electrolyte thin films. Solid State Ionics 53-56, 647-654 (1992)... 

Solid-State Electrolytes. True all solid-state ionic electrolytes such as lithium phosphorus oxynitride (LiPON) provide adequate conductivity for use in thin film solid-state batteries (see Sec. 35.8.)... 

In the late 1970s, polymer electrolyte materials were proposed for use in solid-state battery designs." A considerable development effort has resulted in a number of review arti-cles" " describing the status of such batteries in some detail. The unique aspect of these batteries is that the electrolyte is a soM flexible film comprised of a polymer matrix and an ionic salt complexed into the matrix. Thin-film solid-polymer electrolyte batteries offer tbe possibility of an intrinsically safe battery design in combination with good high-rate capability. 

A specialized type of Li-ion battery developed for semi-conductor and printed circuit board (PCB) applications are thin-film, solid-state devices. These batteries which employ ceramic negative, solid electrolyte and positive electrode materials, can sustain high temperatures (250°C), and can be fabricated by high volume manufacturing techniques on silicon wafers which are viable as on-chip or on-board power sources for microelectronics. Batteries of this type can be very small, 0.04 cm x 0.04 cm x 2.0 fjm. For microelectronics applications, all components must survive solder re-flow conditions, nominally 250°C in air or nitrogen for 10 minutes. Cells with liquid or polymer electrolytes cannot sustain these conditions because of the volatility or thermal stability of organic components. Further, cells that employ lithium metal also fail as solder re-flow conditions exceed the melting point of lithium (180.5°C). 

Lithium solid state microbatteries, which consist of a thin-film electrolyte sandwiched between two thin-film electrodes (Figure 11.13), have been realized and give high perfor-mances. Among mai attempts presented, one finds consistent effort toward the development of complete thin-film solid state battery, and the most promising device seems to be that developed by Jones and Akridge. ... 

Neagu, R., Perednis, D., Princivalle, A. Djurado, E. (2006). Influence of the process jjarameters on the ESD synthesis of thin film YSZ electrolytes. Solid State Ionics. Vol. 177, pp. 1981. 

The composition of the polyurethane gel electrolyte was PU EC PC salt in the ratio 1 2 2 0.1 (w/w).The components were dissolved in 30 mLtetra-hydrofuran and the solution was stirred for 24 h to complete homogenization, then it was cast in a mold to obtain a solid thin-film gel electrolyte. Similarly, Pearl Black 2000 carbon powder (0.10 g), 0.2 g of the above electrolyte solution and additional plasticizer/salt solution (additional plasti-cizer/salt solution was prepared from EC-PC (1 1 v/v) and lithium perchlorate in the ratio 10 1 (w/w)) in the range of 20-200 wt% with respect to the initial mass of the carbon composite electrode homogenized mixture, were cast to make films. To make the cell assembly, the gel electrolyte was sandwiched between high surface area carbon-cloth and carbon-composite electrodes respectively. 

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