Criteria for the Selection of Ligands in the Development of Complex Electrolytes for the Electrochemical Formation of Functional Tin Films as Effective Anode Materials for Lithium-ion Batteries

Abstract

The choice of ligands for complex electrolytes for the deposition of tin films as anode materials for lithiumion batteries with high and stable electrochemical characteristics is substantiated. Tin films obtained from complex (pyrophosphate, tartrate, citrate, citrate-chloride and citrate-trilonate) electrolytes were studied by the methods of potentiodynamic and galvanostatic cycling in a 1 $\mathrm{mol} \cdot \mathrm{l}^{-1}$ aprotic LiClO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> solution. Comparative characterization of the proposed complex electrolytes for the deposition of functional tin films as anode materials for lithium-ion batteries has been performed. It is shown that the nature of the ligand determines the composition of electrochemically active complexes, the mechanism of the process and the electrochemical characteristics of tin films as anode materials of lithium-ion batteries. The specific capacity of thin films of tin obtained from complex electrolytes and the efficiency of their cycling in aprotic solvents with lithium anode are due not only to the nature of the ligand but also to the anion of tin (II) salt. The most stable charge / discharge characteristics during long cycling are inherent in tin films with minimal masses deposited from pyrophosphate and citrate-chloride electrolytes, including when discharge is at different current densities. The mechanism of deposition of tin (II) from these electrolytes, in contrast to tartrate, citrate and citrate-trilonate electrolytes, is limited by the preceding chemical reaction of formation of electrochemically active complexes of tin (II). The obtained tin films have a high specific capacity and are able to provide a high charge / discharge current density without mechanical failure, which will allow them to be used as effective anode materials in lithium-ion batteries.