Recent progress in the development and use of organic ionic plastic crystal electrolytes

Abstract

Significant progress has been made recently in the development of Organic Ionic Plastic Crystals (OIPCs), a unique family of solid state electrolytes with applications in electrochemical devices such as lithium batteries and dye-sensitised solar cells. The negligible volatility of OIPCs renders them more suitable than molecular species for long-term device use, while the high thermal and electrochemical stability of many OIPCs fulfils an essential requirement for solid state electrolytes for many device applications. However, the complex mechanisms of conduction through these materials, both in their pure state and in the presence of a small amount of a second component (such as lithium salts to enable their use in lithium batteries) are still not fully understood. At the same time, the range of anions and cations utilised in the synthesis of plastic crystal phases continues to increase. This perspective concentrates on recent research into both fundamental and device-oriented aspects of these materials. Important fundamental understanding of the physical properties and transport mechanisms of different OIPCs has been achieved through use of techniques including variable temperature solid-state NMR and crystallographic analysis, as well as detailed molecular dynamics simulations. In parallel, the applicability of these materials as electrolytes for dye-sensitised solar cells and lithium batteries is being more widely demonstrated. The possibility of using OIPCs as solid state electrolytes for fuel cells is also discussed.

Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion

“…Although the molecules in the highesttemperature phase of 1 b were found to undergo anisotropic rotation (see below), they can be regarded as ionic plastic phases [17] having melting entropies smaller than 20 J K À1 mol…”

Phase Behavior of the [N(C₂H₅)₄][BF₄]-[N(C₃H₇)₄][BF₄] Binary System

“…[1][2][3][4][5][6][7][8][9][10][11] In particular, organic ionic plastic crystals (OIPCs) are attractive for the application as solid-state electrolytes because of the greater structural flexibility than simple inorganic salts. 8,12 Because of the similarity in chemical structures of ionic species used in IPC and ionic liquid materials, chemistry of OIPCs is often regarded as an extended field of ionic liquids. The plastic crystal phase is commonly reached via a solid-solid phase transition with increasing temperature and is often associated with an order-disorder transition.…”

Synchrotron Radiation and Chemistry: Studies of Materials for Renewable Energy Sources

“…Today, the research in dye-sensitized solar cells is focussed to the elimination of liquid electrolytes [30], involving cumbersome management and leakage-related performance decay. Actually, solid hole conducting polymers like spiro-OMeTAD (2,2 ,7,7 -tetrakis(N,N -di-p-methoxyphenylamine)-9,9 -spirobifluorene ensure better efficiency, durability, thermal and electrochemical stability with respect to liquid electrolytes.…”

“…In particular, the dye LUMO must lie higher in energy with respect to the semiconductor conduction band, while the HOMO should be lower than the hole level of the electrolyte. In view of this mutual arrangement, most of the SR studies are addressed to the investigation of the electronic strucure by photoemission and soft X-ray absorption techniques [28][29][30].…”