Lithium cells self-discharge

As a rule, manganese dioxide-lithium cells are discharged to the final voltage of 2 V the rated voltage is 3 V. The cells function in the temperature range of -20 to +50°C and can be stored for 10 years without any significant self-discharge. 

Self-discharge by the diffusion of iodine through the Lil layer is minimal. The result of this is that only a very thin layer of Lil is initially formed, so that the resistance of a freshly made cell is only 2-3 kQ, and losses in capacity during storage or use are small - estimated to be 5-10% over a period of 10 years. On the other hand, if the lithium electrode should... 

During overcharge of a cell an instability was observed because of an increase of lithium activity in the negative electrode, of its dissolution in the electrolyte and therefore the self-discharge [375] increases. To avoid this phenomenon, approximately 10 mol% Al5Fe2 was added to the negative electrode. These electrodes were employed throughout 900 cycles without an appreciable capacity loss. 

The necessary porosity for thicker layers was introduced by appropriate current densities [321-323], by co-deposition of composites with carbon black [28, 324] (cf. Fig. 27), by electrodeposition into carbon felt [28], and by fabrication of pellets from chemically synthesized PPy powders with added carbon black [325]. Practical capacities of 90-100 Ah/kg could be achieved in this way even for thicker layers. Self-discharge of PPy was low, as mentioned. However, in lithium cells with solid polymer electrolytes (PEO), high values were reported also [326]. This was attributed to reduction products at the negative electrode to yield a shuttle transport to the positive electrode. The kinetics of the doping/undoping process based on Eq. (59) is normally fast, but complications due to the combined insertion/release of both ions [327-330] or the presence of a large and a small anion [331] may arise. Techniques such as QMB/CV(Quartz Micro Balance/Cyclic Voltammetry) [331] or resistometry [332] have been employed to elucidate the various mechanisms. 

Solid-state and wet lithium cells have replaced the conventional Rubin-Mallory zinc/mereury pacemaker battery using aqueous NaOH solutions. Both types of lithium cell exhibit higher energy densities than conventional cells, e.g. Zn/HgO with 100 W h/kg > or 0.35 W h/cm or Zn/MnOj with 0.1 to 0.2 W h/cm " >, and a far longer shelf-life, e.g. a lead-acid battery exhibits a self-discharge rate of 1 % per day the Zn/MnOj-cell of 20 % per year... 

Microfuel cells Microfiiel cells such as lithium ion cell offer an interesting alternative to the batteries by providing high-energy density, low self-discharge rate with unattended operation, and many years of maintenance-free performance [29]. 

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