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SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff Bao Smith – B.Sc. Tim Blythman – B.E., B.Sc. Advertising Enquiries (02) 9939 3295 adverts<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty – M.Ed. Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com Founding Editor (retired) Leo Simpson – B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (Australia only) 6 issues (6 months): $70 12 issues (1 year): $130 24 issues (2 years): $245 Online subscription (Worldwide) 6 issues (6 months): $52.50 12 issues (1 year): $100 24 issues (2 years): $190 For overseas rates, see our website or email silicon<at>siliconchip.com.au * recommended & maximum price only Postal address: PO Box 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: 9 Kendall Street, Granville NSW 2142 2 Silicon Chip Editorial Viewpoint Confusion between lithium battery types It has become very common for people to refer to lithium-ion batteries as “lithium batteries”, but that is confusing since lithium metal batteries existed before lithium-ion batteries were invented, and they are quite different. The term “lithium battery” used to specifically refer to a disposable battery that used lithium metal as the anode. These have been around since the 1970s and are still widely used in applications where long shelf life and high energy density are important, such as memory backup, smoke alarms and small medical devices. They come in various chemistries, like lithium-manganese dioxide, lithium-­ thionyl chloride, lithium-iron disulfide, and so on. Those all share one critical feature: they are not rechargeable. In contrast, lithium-ion batteries are rechargeable and use a lithium compound rather than metallic lithium. The lithium atoms give up an electron to become positively charged ions, which move between compounds in the electrodes during charging and discharging – hence the name. Though their chemistry is more complex and sensitive than lithium-metal batteries, their energy density and rechargeability have made them the dominant choice for everything from phones to electric vehicles. In fact, what we call “lithium-ion batteries” is a whole family of different chemistries with similar, but not identical, properties. Common lithium-ion chemistry variants include lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt oxide (LiNiMnCoO2), lithium nickel cobalt aluminium oxide (LiNiCoAlO2), lithium manganese oxide (LiMn2O4) and lithium iron phosphate (LiFePO4). You may be familiar with that last one because it has more significantly different properties from most of the others, such as a lower terminal voltage, plus better tolerance for over-charging and over-discharging. Getting back to my main point, why the confusion between lithium-ion and lithium batteries? Somewhere along the line, “lithium-ion battery” got shortened; first in casual conversation, then in journalism, and now even in marketing. The problem is that “lithium battery” still means something else in technical contexts. The distinction especially matters in transport: postal and courier rules, particularly for air freight, can differ significantly between lithium and lithium-ion batteries. It doesn’t help that many consumer devices now include vague labels like “contains lithium battery”, even on products that clearly use lithium-ion cells. This ends up muddying the waters for everyone else. The distinction is especially important when it comes to charging. Try to charge a non-rechargeable lithium battery and you’re asking for trouble. The internal chemistry isn’t designed to handle reverse current, and the result can be catastrophic: swelling, leakage, or even fire. It is not just theoretical; there have been fires caused by consumers mistakenly trying to recharge lithium primary cells, often due to this exact terminological conflation. We all sometimes refer to a cell as “a battery” when (arguably) batteries contain more than one cell, but that’s a minor point. Not so the distinction between lithium and lithium-ion batteries. So let’s make a collective effort to be more precise. Use the term “lithium-­ ion” (or even better, the specific chemistry) to refer to rechargeable batteries. If you’re referring to a lithium-metal primary cell, it’s best to be explicit, but if you must call anything a “lithium battery”, it should be those types only. Cover Image: Steve Jurvetson – www.flickr.com/photos/ jurvetson/8065095602/in/album-72157608597030651/ (CC BY 2.0) Australia's electronics magazine by Nicholas Vinen siliconchip.com.au