Soluble and insoluble inorganic additives have been applied to gel electrolytes in order to study possible enhancement of their characteristics and in this way extend the lifetime of lithium ion batteries. These additives consist of pure aluminum bromide (AlBr(3)) and/or fumed aluminum oxide (Al(2)O(3)) filler, pure and modified with H(2)SO(4). These have been added to lithium perchlorate (LiClO(4)) dissolved in propylene carbonate (PC) giving, in result, electrolytes that can be soaked into PVdF/HFP-based membranes. According to theory, this certain type of additive should improve properties of the electrolyte. For comparison the addition of fillers with Lewis acid surface groups on the properties of gel electrolytes is shown. This article presents measurements of lithium transference numbers, stability of the passive layer between the metallic lithium and gel electrolyte, also spectroscopic measurements of the gel electrolytes have been performed. (C) 2011 Elsevier Ltd. All rights reserved.