Review—Non-Carbonaceous Materials as Cathodes for Lithium-Sulfur Batteries

Abstract

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...

Low‐Temperature Synthesis of a Sulfur‐Polyacrylonitrile Composite Cathode for Lithium‐Sulfur Batteries

“…The fabrication of sulfur‐polyacrylonitrile composites (SPAN), which are classical representatives of these type of functional materials, has been proved to be very promising . Moreover, polymers offer soft structures that can undergo significant volume changes and improve the conductivity of composite cathodes . Although the precursors, polyacrylonitrile (PAN) and elemental sulfur, are the same in all reported SPAN composites, the specific synthetic protocol varies considerably in temperature, heating time, molar ratio of the reactants, and final sulfur content.…”

“…With the purpose to solve these problems, great effort has been made by modifying cathode composition, electrolyte, lithium anode, and separator . A special interest has been put on the cathode material modification in order to produce a functional material for energy storage.…”

Lithium Recovery from Brines Including Seawater, Salt Lake Brine, Underground Water and Geothermal Water

“…Lithium demand is expected to grow continuously and dramatically in the coming years as different types of lithium batteries are the most promising candidates for powering electric or hybrid vehicles [10,11]. Lithium batteries include both current technologies such as lithium-ion and growing battery technologies such as lithium-sulfur or lithium-air [12][13][14][15].…”

Pyrrolic‐Type Nitrogen‐Doped Hierarchical Macro/Mesoporous Carbon as a Bifunctional Host for High‐Performance Thick Cathodes for Lithium‐Sulfur Batteries

“…These conductive additives need to be critically designed for maintaining the electrode structure during cycling. This is due to the large volume change of 80% when converting sulfur (S 8 ) to Li 2 S. As the cell is cycled, the structure of the electrode is disrupted as sulfur loses contact with carbon, resulting in an interruption of the conductive pathway and a decline in cycle life . Additionally, the intermediate lithium polysulfides, (Li 2 S x , x = 4–8, LiPS), are produced from the conversion‐reaction chemistry of sulfur and readily dissolve in the organic electrolyte, causing LiPS shuttling between the two electrodes .…”