Just to corroborate some of the info in this thread:
The cells Dr. Meyer is referring to are Energizer Lithium AA 1.5v cells. They are a specially constructed "consumer-driven" battery style-- the chemistry of prior cells using Li-Mn technology were 3v nominal primary cells. Energizer is the one manufacturer I know of currently making these 1.5v jobs: I believe they developed it or bought the exclusive rights to it. I'm told Panasonic do have a version, but I haven't seen it on shelves yet.
But Li-Mn 3.0v (and Lithium-chloride 3.6v) technology has been used by our calc community for a long time... if you have any devices using CR2032's or 2016's or many of the other "coin-cell" lithium batteries, that's what they are.
Other than an extremely fast discharging (a short), I can think of no condition that could arise in which these cells would ever cause damage to a calculator.
Note also that the "cmos" backup battery in your PC, laptop or PDA computer will almost always be a Lithium primary cell; a 3v coin cell, or, as in most Macs, a 3.6v "1/2 AA" short cylinder cell. These have proven VERY reliable for these low-drain applications.
Why a primary Lithium instead of a rechargeable NiCd or NiMH? Because rechargeables, even whether used-down regularly or hardly ever drawn upon, can only stand the pressures of constant trickle-charging for a limited time. The NiCd might last a few years; the NiMH is more charge-sensitive and might last MAYBE two years as a constantly-charged backup; but the ideal in a PC is a backup that doesn't even NEED a trickle, and lasts more like six to ten years. That's the Lithium primary.
Also, the 1/2-AA and AA-sized 3.6v (and sometimes the camera-sized cr-2 or cr-123) are used quite often in remote alarm systems for the glass-breakage detectors mounted on ceilings or high-walls. You only have to replace them after 5 years of use or so-- unlike akalines which would make you climb a ladder every 18 months.
I have never seen a corroded, leaky or bulging Li-Mn cylinder or coin-- never. Saft, Maxell, Tadiran, Sanyo, Panasonic, Sony, Renata, Ultralife or Energizer. I handled lots of these, sold trays full of these-- they just don't have this failure mode, UNLIKE alkalines or silver-oxide cells, which do rupture/leak on occasion. Dr. Mikey is, in my opinion, on totally safe ground with these. I think, with his experience of their utility in calcs, he has convinced me to try some in my 33c, in fact.
True, a "short" CAN cause the LiMn batteries to occasionally explode in a most spectacular manner-- like a "black cat" firework-- and I have actually seen this happen once; I tossed a 2032 into a box of dead coin cells and it hit them just right. The result was a loud percussion and a black powder-mark on the wall just above the box. The battery was separated neatly in two like an oreo cookie-- but I'm glad I wasn't hovering my fingers over that box.
But a short is really a rare (maybe non-existent) thing if installed in equipment. I've never seen a Casio databank, for example, damaged by batteries (it uses 3 coin lithiums: 2 for display, 1 for data-backup). Chances are, if you have a car made in the last 5 years, you are carrying a remote keyless entry fob in your pocket. Most of them contain one or two coin-style lithium cells. They undergo real abuse, as you can probably imagine. They don't leak though, and I've never heard of one exploding.
While I was working at a Batteries Plus, I would occasionally tack-weld solder-tabs onto coin cells, mainly for laptop computer CMOS backup-battery replacements. The metal can on these is extremely thin, and so the pulse of the welder is set to a much lower level when working on these than, say, to weld tabs on a NiCd. I believe that the REASON the metal is so thin is for safety: if it DID become shrapnel, it would tear and deform and lose energy there rather than propelling sharp hard pieces... you gun-owners probably know that ammunition cabinets are made of soft containment metals for a similar reason.
Anyway, in tack-welding to them, a couple of times I melted through the thin metal can of a lithium cell (this'll wake you up during a long shift). It spits out a watery clear-grey substance which does not seem to be very corrosive, nor does it much irritate the skin-- BUT it SMELLS really nasty. So bad, in fact, that it'll take several minutes to get the icky sweet, metallic smell out of your nostrils. I have no doubt it is poisonous. Um, don't try it at home.
I have heard of R/C modellers and scale-racing car enthusiasts building pulsed rechargers from schematics on the internet so that they can recharge LiMn cells (CR-123 camera cells usually). This is dangerous-- though the camera-typs cr-2 and cr-123 are designed as wide-bodied and capable of handling large drains, they are NOT intended for recharge. If you are not extremely cautious, you will cause them to develop a hot-spot inside, and then they MAY explode. Radio-control guys live on the bleeding-edge of battery performance, so they do risky things and experiment with all technologies-- which is fine, but is *no* guide to those of us who want reliable and SAFE power sources.
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Now, what about Lithium-ION? Well, that is a slightly different set of technologies from the LiMn/LiCl primary cells we have been discussing. Unlike the primaries, Li-Ion CAN be charged and recharged for hundreds of cycles (typical lifetime: two years). It has the highest storage density of any rechargeable; it has a VERY small self-discharge rate; it can deliver to moderate loads without sagging; UNFORTUNATELY, it is still really expensive and requires a fairly sophisticated circuit around it, especially in packs, or it becomes unstable and can explode or catch fire. (Which is, I believe, the reason for the story related by Bill Hemphill earlier-- an early ICOM Li-Ion setup).
Currently, most laptops use them, and most handheld Videocameras, and some PDAs and digital cameras. They will ALL have an ABS fire-resistant plastic case, and ALL have a failsafe coulometry circuit inside them, which will DISABLE THE PACK if any anomaly develops in any ONE cell in the pack. So you may have a LiIon battery that works fine for months until suddenly, it is dead to the world-- this is the fail-safe circuit having done its job of protecting the user and his equipment.
You will see Li-Ion EVENTUALLY in AA and similar consumer sizes, I think, IF nothing better comes along in the meantime, and IF the cost of the cell INCLUDING the charge-limiting, delivery-limiting and failure-protection circuits can be made reasonably cheap. Right now a single AA made this way would cost about $10-15, with a $50-75 charger for it to go into... this hasn't really got the marketing guys all excited just yet.
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Environmental note: all RECHARGEABLES (NiCd, NiMH, LiIon, lead-acid, etc) pose a potential problem when considered "en masse".
They all have Heavy Metals, that is, elements that exist in nature in trace quantities everywhere, but when you concentrate them for a purpose like making a battery, you are changing the way Nature decays and disperses their effects.
Lead was a terrible problem for years-- so useful in so many ways to us, but until we got wiser, it was building up in biopotentially harmful ways. Now it's out of paints, fuels, eating utensils and landfills-- and so lead-poisoning is fairly rare now. The Battery Council International (a manufacturers coalition) is proud of statistics which show lead to be the most recycled material on earth-- some 97% of lead used in batteries is eventually returned for re-smelting.
After a heavy awareness set in on mercury's effects in fish and waterfowl, it was taken out of formulations of alkaline and other batteries. Now, mercury poisoning is rare-- except a few places in the world where agricultural chemicals are still allowed to contain the stuff.
Nickel, Cadmium, and Lithium are disposal problems in the making because they often DO end up in the landfill, and thus their concentrations in groundwater become a concern. While these elements play important roles in life-processes, too much of any of them has been shown to increase birth defects and stillbirths. Sterility is suspected to be one effect of excessive cadmium exposure. So communities would do well to support recycling efforts for these materials. You may have to call around in your area to find the proper place in your municipality for disposal of rechargeable batteries-- in some places, they classify them as hazardous waste and seal them in drums to be buried on the high side of the city dump.
(Batteries Plus, by the way, accepts all rechargeable batteries for recycling, and they ship them to a company that does metal-reclamation in a large-scale operation, which makes it economically feasible. This is something I was proud my employer supported so fully.)
Lithium PRIMARY coin-cells and camera batteries and the consumer-sized Li-Mn and Li-Cl have YET to be considered by the U.S. government for either hazardous status or for serious recycling. Some states say they are mere "household waste". A couple of states are of the opinion that they are hazardous, yet have no disposal guidelines for consumers, only industrial users. My personal advice is to put them in plastic bags for the time your locality invites hazardous waste disposal, and give it to them then. To drop it into the trashcan only is to put it eventually in your community's water-table; you don't really want that.