An electrode group is constructed by disposing a positive electrode current collector exposed portion on one end side and a negative electrode current collector exposed portion on the other end side. This is the most simple and most effective design to predetermine the optimal ratio of volumes of expansion and compression processes only at the expense of the form of profile of contact surface of pair gear rims of the rotary machine. More particularly, said mixture is including a succinate and a formate, wherein the succinate is in an amount of at least 50 wt %, on a dry basis. in order to reduce the need for oversampling in high-frequency applications, the invention furthermore proposes a multi-phase sampling technique according to which a number of phase-shifted sample clocks are generated for the purpose of sampling the signal to be monitored.