Performance of Polyphosphazene Based Gel Polymer Electrolytes in Combination with Lithium Metal Anodes

Polyphosphazene based polymer electrolytes exhibit excellent thermal and electrochemical properties accompanied by a high stability versus lithium metal anodes [1]. The combination of the cross-linked polymer matrix with electrolytes based on organic carbonates or ionic liquids leads to ionic conductivities of 1 mS/cm at 30 °C and good lithium transference numbers. Even with high amounts of liquid additives, the mechanical stability is suitable for use as ion conducting polymeric separator membrane for lithium ion cells. Here, we present the electrochemical performance of different “MEEP” based gel polymer elecrolytes and the galvanostatic cycling behaviour using cells with lithium metal anodes (cf. Fig. 1) and different cathode materials. The results indicate a very good cycling stability due to the high stability of the polymer in contact with metallic lithium. Compared to other gel polymer electrolytes in combination with carbon anodes [2] the “MEEP” based gel polymers exhibit good cycling stability with higher specific capacities.

Fig. 1. Galvanostatic cycling of a full cell with polymeric gel electrolyte from MEEP using LiFePO₄cathode and metallic lithium as anode.

The authors acknowledge funding by the German Ministery for education and research (BMBF) within the project “MEET Hi-EnD“.

[1] Jankowsky S. et al., J. Power Sources 2014, 253, 256-262.

[2] Isken P. et al., J. Power Sources 2013, 225, 157-162.