The continuously increasing number and size of lithium-based batteries developed for large-scale applications raise serious environmental concerns. Herein, we address the issues related to electrolyte toxicity and safety by proposing a “water-in-ionomer” type of electrolyte which replaces organic solvents by water and expensive and toxic fluorinated lithium salts by a non-fluorinated, inexpensive and non-toxic superabsorbing ionomer, lithium polyacrylate. Interestingly, the electrochemical stability window of this electrolyte is extended greatly, even for high water contents. Particularly, the gel with 50 wt% ionomer exhibits an electrochemical stability window of 2.6 V vs. platinum and a conductivity of 6.5 mS cm −1 at 20 °C. Structural investigations suggest that the electrolytes locally self-organize and most likely switch local structures with the change of water content, leading to a 50% gel with good conductivity and elastic properties. A LiTi 2 (PO 4 ) 3 /LiMn 2 O 4 lithium-ion cell incorporating this electrolyte provided an average discharge voltage > 1.5 V and a specific energy of 77 Wh kg −1 , while for an alternative cell chemistry, i.e., TiO 2 /LiMn 2 O 4 , a further enhanced average output voltage of 2.1 V and an initial specific energy of 124.2 Wh kg −1 are achieved.
Bibliographical noteFunding Information:
Jie Li and Jun Wang acknowledge the funding from the German federal ministries of education and research (BMBF), of economics technology and environment (BMWi), of nature preservation and nuclear safety (BMU) within the project KaLiPat (03EK3008). Dominic Bresser would like to acknowledge the NanoSciences Programme (CEA) and the EU/CEA Enhanced Eurotalents Fellowship for financial support. Moreover, Dominic Bresser would like to thank Dr. Alain Farchi for his support with setting up the SAXS experiments. Zigeng Liu would like to thank Yanting Jin for the measurement of samples with solution NMR. We thank Margarita Kruteva for supporting the SAXS measurements on GALAXI.
© 2018, The Author(s).