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Lithium-Ion/Manganese High-Current Cells (Glossary) |
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| Lithium-Ion packs are being constantly developed and are becoming more efficient in practically every respect. For example their energy density has risen by around 10% each year over the past decade or so, the number of charging cycles has increased tenfold over the same period and the charge time too could be significantly improved. The use of new materials from the highly innovative and dynamic nanotechnologies sector in particular (mainly through an enlargement of the electrode surface area with the aid of nano-crystals) is steadily pushing the characteristics of Li-ion packs upwards. Through the use of new, manganese-based cathode materials and thus a much lower internal resistance of the cells, their high-current strength could also be decisively improved. Manganese as an electrode material The first generation of secondary Li-ion cells was based on lithium-cobalt oxide (LiCoO2) as a cathode material. Lithium-manganese oxide (LiMn2O4) lent itself as an alternative on account of the lower price, better environmental compatibility and for safety reasons. A simplified total formula results in:  Apart from a lower spontaneous discharge, wider temperature range, cycle strength of over 1,000 and the higher voltage that is typical of lithium-ion cells, they also display the following particular advantages: High-current strength The high-current strength of rechargeable batteries is a decisive criterion, particularly for the power tool market and starter batteries. For example, the starting currents of electric drills are only limited by the internal resistance of the cells. Li-ion high-current cells (Type 18650 and 26650) for power packs can now provide peak currents of up to 50 A and constant currents of up to 30 A thanks to their much lower internal resistance. Inherent safety High-current cells based on manganese have a high inherent safety since manganese does not react with lithium. In many cases a PCB ('Protection Circuit Board' - electronic circuit to monitor under and over-voltage, short-circuit and temperature) is thus not needed in this type of battery pack, saving weight and costs. Fields of use Li-ion high-current cells open up fields of use for accumulators that call for particularly high peak and constant currents, e.g. power tools, golf caddies, self-contained vacuum cleaners and bicycles with axillary motors. © Marc Stenzel |
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