An AB alternating diblock single ion conducting polymer electrolyte membrane for all-solid-state lithium metal secondary batteries

Lithium 4,4'-difluorobenzene sulfonyl imide is copolymerized with polyethylene glycol (PEG, M-w = 200, 400, 600, 800 and 1000) to synthesize a series of AB alternating diblock copolymer electrolytes (ADCE-1, 2, 3, 4, 5) for reducing the crystallinity of solid-state single ion conducing materials for applications in all-solid-state lithium metal secondary batteries. The free-standing film of ADCE-5 with the highest [EO]/[Li+] ratio (23.7:1) is found to display the lowest glass transition temperature (T-g) and the highest ionic conductivities of 6.61 x 10(-6) S cm(-1) at 30 degrees C and 2.24 x 10(-4) S cm(-1) at 100 degrees C. The alternating architecture of the polymer effectively prevents the polymer from phase separation originated from aggregation of the ionic groups as well as the ethylene oxide groups. As a result, segment motion may take place readily in the amorphous region at low temperature. Subsequently, a piece of glass fiber mat reinforced composite polymer electrolyte film is prepared for practical battery tests. The fabricated all-solid-state single ion conducting polymeric lithium metal secondary battery is able to work at a temperature as low as 40 degrees C with stable cycling performance. The battery delivers 102 mA h g(-1) at 0.1 C and is stabilized at 94 mA h g(-1) after 200 cycles.