Abstract
Currently, commercialised batteries work with negative electrodes based on carbon or graphite which show good cycling properties, but have limited mass and volume capacities and and may be unsafe under certain conditions <br />In order to increase the specific energy, several metals forming alloys with lithium were proposed as new generation accumulators due to their high energy density. <br />The aim of the present work is the search and development of new composite materials synthesized by ex situ dispersion of tin in an inactive matrix (CaSiO3). <br />The performances of the composite ‘‘Sn-0,4CaSiO3'' chosen as the reference compound are interesting: high reversible mass capacity of 480 mAh.g-1, low polarization of only 140 mV. However, the first-cycle capacity loss of 146 mAh.g-1 is too important and the cycling stability is insufficient.<br />To understand the reasons responsible for these two phenomena we have undertaken a detailed study of the reaction mechanism governing the first cycle of restructuration. To this end, several experimental techniques were combined. <br />We show that the charge/discharge rate influences the restructuration process. At a C/50 rate, the formation of tin-rich and stable intermediate alloys like LiSn leads to poorer performances than the restructuration process taking place at a C/10 rate. The chemical composition of the matrix influences the electrochemical properties and in particular the first-cycle capacity loss. The use of sodium borosilicate, which is a better conductor than calcium silicate, significantly reduces the irreversible capacity in the first cycle (90 mAh.g-1).