Physical-Chemical and Electrochemical Studies of the Lithium Naphthalenide Anolyte

We carried out physical-chemical and electrochemical characterizations of lithium naphthalenide solutions in tetrahydrofuran (THF) in view of their potential use as liquid anode material in rechargeable batteries. Concentrations of dissolved naphthalene and lithium were varied to prepare homogeneous solutions of general formulae LixN(THF)(n); 0 <= x <= 2 and 3 < n < 25. FTIR investigations support a two-step mechanism for LixN(THF)(n) formation. For 0 < x < 1 the solutions consist of mixture of lithium-free naphthalene Li0N(THF)(n) and lithium-bound naphthalene Li1N(THF)(n) whereas for 1 < x < 2 the solutions consist of mixture of Li1N(THF) and Li2N(THF) solutes. Electrical conductivity traces (sigma(x, n)) make a maximum at x similar to 1 in diluted solutions (n > 10) and at x similar to 0.5 for more concentrated ones (n < 10). The highest sigma value of 12.4 mS/cm is achieved in Li0.5N(THF)(6.2) composition. The conductivity of LixN(THF)(10.4) solutions shows linear behaviour with temperature of with negative slopes highlighting its metal-like character. We found a logarithm law of viscosity with 'x', a common feature in amorphous systems. Entropy and enthalpy measurements were performed in a Li/Ceramics/Li1N(THF)(10.4) half-cell by monitoring open-circuit potentials (OCP) changes in the temperature range of 25 degrees C - 10 degrees C. A full cell consisting of Li1N(THF)(10.4) anode and a iodine based liquid cathode was successfully tested to proof the concept of a new all liquid electrodes refillable lithium batteries. (C) 2015 Elsevier Ltd. All rights reserved.