Study of the Relaxational Polarization Dynamics of the LiPON Solid Electrolyte
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y of the Relaxational Polarization Dynamics of the LiPON Solid Electrolyte A. S. Rudyiа, *, M. E. Lebedevb, A. A. Mironenkoа, L. A. Mazaletskiib, V. V. Naumovа, A. V. Novozhilovab, **, I. S. Fedorovb, and A. B. Churilovа а
Yaroslavl Branch, Valiev Institute of Physics and Technology, Yaroslavl, 150007 Russia bDemidov State University, Yaroslavl, 150003 Russia *e-mail: [email protected] **e-mail: [email protected] Received January 22, 2020; revised January 30, 2020; accepted February 13, 2020
Abstract—The results of investigation of the polarization relaxation mechanism for the LiPON solid electrolyte by a discharge through an external load are presented. Test cells implemented in the form of encapsulated multilayer structures SiO2 Pt (100 nm) LiPON (1000 nm) Pt (100 nm) Ti (10 nm) SiO2 Si and previously studied by the standard techniques are tested on a special bench measuring discharge characteristics. The core of the method lies in charging the test cell from a stable voltage source up to saturation with the subsequent rapid switch to precision resistance and detection of the voltage drop. The measurements are taken in the load range from 0.1 MΩ to 10 Ω in the temperature range of –50 to 25°C. An equivalent electric circuit for the test cell is proposed, for which a mathematical model of the discharge process is constructed. In the context of the proposed model, the features of the experimental curves are explained by the processes of redox reactions of the lithium ions at the surface of the electrodes and generation of nonequilibrium charge carriers in the bulk upon the charging and discharging of the test cell. DOI: 10.1134/S1063739720040095
INTRODUCTION Modern lithium-ion batteries (LIBs) are used in a variety of devices: from portable electronics to electric vehicles and power systems. Most of the LIBs are produced via the so-called thick-film (paste) technology. When the use of thick-film LIBs is impracticable due to their dimensions, solid-state LIBs (all-solid-state lithium-ion batteries) manufactured by the thin-film technology are used as an alternative. In the majority of electrochemical systems of all-solid-state LIBs, lithium phosphorous oxynitride (LiPON), which was developed more than 20 years ago in the Oak Ridge National Laboratory, is used as an electrolyte [1, 2]. This material remains in demand due to its following characteristics: —ionic conductivity of 2 × 10–6 S/cm at 25°C; —electron transference number te < 10–8; —potential window of 0–5.5 V. The relatively low (against liquid electrolytes) ionic conductivity of LiPON is balanced by the electrolyte’s thickness in the thin-film LIB variant, which is not larger than 1 μm. Commonly, LiPON is deposited as a thin film on one of the LIB electrodes by the magnetron sputtering of lithium orthophosphate (Li3PO4) in a rarefied
nitrogen atmosphere. Most publications on this issue contain a brief description of the deposition technology, which enables obtaining the desired values of a LiPON film’s ionic conductivity. In making test cells
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