Lithium-sulfur batteries are presented as a promising alternative for the operation of those devices, including electric vehicles, that require higher specific capacity than current lithium-ion technology. Unfortunately, lithium-sulfur batteries suffer from several limitations that still produce a relatively fast capacity fading and poor utilization of active materials. In order to alleviate the disadvantages that arise at the cathode, several researchers have searched for new electrode materials. Because of the long standing tradition in the use of carbons in energy storage systems, carbonaceous cathodes have been the most popular choice. Recently, however, there has been a trend for the study of non-carbonaceous materials as cathodes in lithium-sulfur systems. Materials such as polymers, metal oxides, metal carbides, amongst many others were reported, showing excellent properties which make them compete side by side with state of the art carbonaceous cathodes. These materials have generally improved the conductivity of the conventional sulfur electrode, and have provided a 3D soft adsorbent porous structure, which efficiently traps polysulfides. These characteristics are reflected in an improved electrochemical performance, reaching, in some cases, capacity retention values close to 1000 mA h g −1 after 100 cycles at high discharge rate. Here, we propose a review of these non-carbonaceous cathodes. The specific energy of current lithium-ion secondary batteries is very close to reaching its theoretical thermodynamic limit.1 This specific energy value is limited for some technological applications, such as long autonomy range electric vehicles.2 Although no other rechargeable battery technology has shown the fantastic cyclability and stability of lithium-ion batteries, the search for new rechargeable battery technologies is a very active field of research.Lithium-sulfur (Li-S) batteries are one of several alternative systems that have been proposed for higher specific energy density rechargeable batteries. A lithium-sulfur battery consists of a lithium anode, an organic electrolyte and a sulfur composite cathode.2-5 During the discharge process, at the anode, metallic lithium is oxidized to lithium cations (Li + ), while at the cathode, and in the presence of lithium ions, elemental sulfur is reduced to lithium sulfide (Li 2 S). These batteries are presented as a promising alternative energy storage system, since they are relatively light and they have the advantage of a high theoretical energy density of 2600 Wh kg −1 , which is almost 6 times higher than that of commercial lithium-ion batteries (387 Wh kg −1 for LiCoO 2 -graphite battery). 6 In addition, sulfur has a very low cost and is largely abundant in nature. [7][8][9] The foundational stone on lithium-sulfur cells was led in 1962 by Herbert and Ulam, who proposed the use of elemental sulfur as cathode material.
10Despite their numerous theoretical advantages, lithium sulfur cells are still not commercially available due to a series of limitations.
11Sev...
