3D Printable Ionogels with High Ionic Conductivity

Hybrid materials based on ionic or polymer components are very useful in electrochemical devices like battery systems or fuel cells due to their unique properties like thermal and electrochemical stability and polarity. For all advances over the past, lithium ion based materials are still costly, limited and not very stable. Currently, solid-state polymer electrolytes (SPEs) and gel polymer electrolytes (GPEs) [ 1 ] have ion conductivities below 10 -4 S/cm at room temperature. Polymer electrolytes can be established by ionic liquids (ILs) which combine beneficial properties like high ionic conductivity, wide electrochemical potential window and high viscosity. These kinds of electrolytes can be very beneficial in solid-state batteries for example. This technology has garnered immense excitement from investors and large corporations. The main advantage of all-solid-state to liquid electrolyte-based batteries is that the size can be easily made smaller e.g. solid‐state electrolytes have a typical thickness of approximately 1.0 μm, whereas the separator in liquid electrolyte‐based cells typically has a thickness of 20 μm. Several investigators are exploring 3D architectures for thin-film rechargeable battery electrodes. Nevertheless additive manufacturing, also known as 3D printing, could revolutionize the structural properties of batteries. In addition, this technology could improve the adaptability of the electrolyte to the electrodes. This scientific approach introduces the possibility to combine ionic liquids with a commercial photoreactive resin to realise a well-defined structure by using stereolithography (SLA). This provides, for the first time, access to ionogels (IGs) with complex 3D shapes (figure 1a) with potential application in battery or fuel cell technology. For first experiments new IGs were prepared by adding a series of sulfonate-based ionic liquids (ILs), 1-methyl-3-(4-sulfobutyl)imidazolium para -toluenesulfonate [BmimSO 3 H][pTS], 1-methyl-1-butylpiperidiniumsulfonate para -toluenesulfonate [BmpipSO 3 ][pTS], and 1-methyl-3-(4-sulfobutyl) imidazolium methylsulfonate [BmimSO 3 H][MeSO 3 ] with a clear photoreactive resin which were used in a Form 2 3D printer [2]. Moreover, the IGs are thermally stable up to about 200 °C and mechanically robust. In addition to this synthesized protic conductive IGs, sulfobataine, metal and lanthanides containing IGs were prepared and analysed. These IGs exhibit higher conductivities compared to the sulfonated based IGs in the range from 10 -4 to 10 -2 S/cm at room temperature. 3D Printable metal-lanthanide IGs could possibly be an adequate replacement for lithium-ion electrolytes. Figure 1: a) Well-defined structures of IGs by SLA, b) Rhd battery cell for electrochemical measurements. Literature: [1] Stephan, A.M., Review on gel polymer electrolytes for lithium batteries. European polymer journal, 2006. 42 (1): p. 21-42. [2] Zehbe, K.; Lange,A.; Taubert, A., Stereolithography provides access to 3D printed ionogels with high ionic conductivity , Energy and Fuels, accepted. Figure 1