New polymer lithium secondary batteries based on ORMOCER (R) electrolytes-inorganic-organic polymers

Based on new plasticized inorganic-organic polymer electrolytes CM. Popall, M. Andrei, J. Kappel, J. Kron, K. Olma, B. Olsowski,'ORMOCERs as Inorganic -organic Electrolytes for New Solid State Lithium Batteries and Supercapaci tors', Electrochim. Acta 43 (1998) 1155] new flexible foil-batteries in 'co ffee bag arrangement' were assembled and tested. The electrolyte works as s eparator and binder for the cathodes. Self-diffusion NMR studies on the sys tem (EC/PC/Li+N(SO2CF3)(2)(-)/ORMOCER(R)) resulted in cationic transport nu mbers t(+)) of 0.42 for the EC/PC/salt system and 0.35 for the ternary elec trolyte, typical for polymer electrolytes. Cycling tests (more than 900 cyc les) proved that the unplasticized electrolyte can act as binder in composi te cathodes of lithium secondary batteries [2]. Charge/discharge cycles of complete batteries like (Cu/active carbon/ORMOCER(R)/LiCoO2/Al) with an ORM OCER(R) as separator electrolyte were measured. The voltage drop of these b atteries is very similar to cells with standard liquid electrolytes and the efficiency is close to 100%. Cycling the batteries with a current density of 0.25 mA cm(-2) between the voltage limits of 3.1 and 4.1 V results in a charge/discharge capacity (referring to the cathode mass) of 100 mAh g(-1) at the beginning and after a slight decrease in a stabilised capacity of 75 mAh g(-1) after 15 cycles. These promising results could be optimised by u sing highly purified components. (C) 2001 Elsevier Science Ltd. All rights reserved.