ИСТИНА

At present rapidly evolving technologies require continuous enhancement of energy storage performance and creation of next-generation high-energy and high-power batteries. Lithium metal is considered to be the most perspective anode material for the rechargeable lithium battery systems including highly promising Li–sulfur, Li–air, and others [1-3]. Main reason preventing successful deployment of rechargeable lithium metal batteries is connected with non-uniform lithium plating during charge. Li is deposited in the form of filaments often called “dendrites” at negative electrode that leads to internal short-circuiting, low Coulombic efficiency, and short cycle life. Although there is still no widely acknowledged mechanism of dendrite initiation and propagation established. Dendrite formation during electrodeposition is rather complicated process and can’t be studied with only electrochemical techniques. Hence, in order to monitor solid electrolyte interphase (SEI) formation, dendrite nucleation and growth in polymer electrolyte we suggest using neutron reflectometry (NR) in situ as transient processes taking place in the working electrochemical cell can hardly be quenched for ex situ analysis. In contrast to other techniques, NR provides an averaged information of surface layers evolution thus allowing to avoid locality of information obtained, which can distorted by many factors. NR measurements of operating electrochemical cells have been performed in originally designed three electrode electrochemical cell at GRAINS reflectometer with horizontal sample plane (IBR-2 reactor, Dubna). Copper coated on single-crystal Si substrate (with Ti adhesion sublayer) served as a working electrode, Li-foil fixed to Ni mesh current collector – as a counter electrode. Ag+/Ag reference electrode in Vycor-frit isolated tube was inserted into the cell for providing accurate potential measurement. For contrast optimization the electrolyte with deuterated propylene carbonate solvent (1M LiClO4 in PC-d6 (C4D6O3)) was used in the experiments. Reflectivity data were collected under open circuit potential (OCV to -0.5V vs. Li+/Li) after lithium was deposited on the working electrode upon various amount of charge passed through the cell at the rate of the deposited layer thickness up to 200 nm. Fit analysis of the obtained dataset shows the technique of neutron reflectometry allows to detect surface layers covering the electrode of about few nanometers thick, further provides with an estimate averaged roughness of the deposited layers. References [1]. Zhong Ma, Xianxia Yuan. A Review of Cathode Materials and Structures for Rechargeable Lithium-Air Batteries. Energy Environ. Sci.,140, (2015) 15. [2]. G. Bieker, M. Winter. Electrochemical in situ investigations of SEI and dendrite formation on the lithium metal anode. Phys.Chem.Chem.Phys., 8670 (2015) 17. [3]. Wu Xu, Jiulin Wang. Lithium metal anodes for rechargeable batteries. Energy Environ. Sci., 515 (2014) 7.