(Invited) Tailored Design of Polymer Electrolytes for Advanced High-Capacity and High-Voltage Lithium Batteries

For decades, the use of polymer-based lithium battery electrolytes has been restricted to cells containing low-voltage positive electrodes such as LiFePO 4 , which intrinsically limited the achievable energy density. On the other hand, the employment of polymer electrolytes allowed for the use of lithium metal negative electrodes, even though the operation remained limited to elevated temperatures due to the relatively low ionic conductivity at room temperature. 1,2 Accordingly, if these two challenges, i.e., the limited stability towards oxidation and the poor ionic conductivity, could be overcome, polymer-based electrolytes may pave the way towards high-energy lithium-metal batteries – one of the main targets of global battery research activities. 3,4 Herein, we report our latest achievements in this field, specifically for single-ion conductors, as they additionally provide highly homogeneous lithium deposition and suppress the detrimental occurrence of reversed cell polarization upon cycling. 2,5 These achievements include the design of polymer electrolytes with enhanced single-ion conductivities of about 10 -3 S cm -1 at 30 °C as well as excellent stability towards lithium metal and high-energy next generation cathode materials like Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 – up to anodic cut-off potentials as high as 4.5 V. As a result, these new single-ion conducting polymer electrolytes allow for highly stable cycling of such cells at 20 °C and even 0 °C. 6,7 We hope that this work will trigger further research efforts also in other labs to boost the development of advanced lithium-polymer batteries. References J. Kalhoff, G. G. Eshetu, D. Bresser, and S. Passerini, ChemSusChem , 8 , 2154–2175 (2015). D. T. Hallinan and N. P. Balsara, Annu. Rev. Mater. Res. , 43 , 503–525 (2013). X.-B. Cheng, R. Zhang, C.-Z. Zhao, and Q. Zhang, Chem. Rev. , 117 , 10403–10473 (2017). Y. Guo, H. Li, and T. Zhai, Adv. Mater. , 29 , 1700007 (2017). H. Zhang et al., Chem. Soc. Rev. , 46 , 797–815 (2017). H.-D. Nguyen et al., Energy Environ. Sci. , 11 , 3298–3309 (2018). Z. Chen et al., submitted manuscript.