When is a Lithium Battery Right for You?

While we are not a lithium battery shop, there is no question that lithium batteries are great. They have an acceptable safety profile for many applications, despite their danger if abused.  Pound for pound, lithium batteries can offer higher power than any other primary battery. They also can offer shelf life on the order of decades, rather than years, and provide excellent low-temperature performance. Lithium batteries can also offer high energy density.

Finally, and for many most importantly, lithium batteries are commonly available off-the-shelf in form factors that can work for many electronic devices. So, here are some times when a lithium battery is right for you:

When an off-the-shelf lithium battery meets your needs, and you have a less than significant supply volume

Custom battery development is a major undertaking, and we’re the first to admit this.  One of the first questions we ask prospective customers is “Why don’t you just use a lithium coin cell or a lithium–polymer pouch?” They are widely available, affordable, have long shelf life, and offer all the power you need for many applications. We are also very upfront about development costs—if you have anything less than large production volumes (think millions of batteries per year), you won’t see any cost savings from developing a custom battery.

What’s more, you may not need a thin film form factor. Thin film batteries have unique design constraints, which don’t carry over to other battery designs. If an off-the-shelf battery does everything you need, you should seriously think about going that route, at least initially.

When lithium battery safety is acceptable

One of the selling points that we have for our custom batteries is that they are intrinsically safer than lithium batteries.  For some biomedical applications, where the battery is in or near the body, this can be a major advantage. From an environmental standpoint, it may also be helpful to move away from lithium batteries for high-volume single use disposable devices; this can help with corporate image in being environmentally responsible and in some cases comply with regulation. That said, lithium batteries have an acceptable safety profile for a wide variety of applications and can be complemented with built-in battery safety monitoring chips. Things like memory backup, flashlights, sensors, toys, and so on can run on lithium batteries, and incidents are few and far between. You may very well find that lithium batteries have an acceptable safety profile after analyzing your application.

When you need a long shelf life

Batteries go bad over time, like many other things. Battery electrodes (the active materials) are reactive materials, which self-decompose over time, react with each other, and/or react with other battery components (such as the electrolyte or separator). These reactions take place over months to years. Lithium batteries generally have shelf lives on the order of decades, depending on the specific chemistry—longer than any other ready to use battery chemistry out there.  So, lithium batteries are what you should use if you need a very long shelf life.

When very low temperature operation is desired

Chemical reactions, both in batteries and elsewhere, tend to slow down as temperature falls. Eventually, at a low enough temperature a given battery cannot supply useful current. This temperature varies with the application used (lower rate applications suffer less degradation at low temperature than high rate applications), and with the type of battery chosen. 

There are two kinds of battery electrolytes out there—aqueous (water-based), and nonaqueous (non-water-based, in other words organic solvents). Aqueous electrolytes tend to become less conductive as temperature decreases to a greater extent than non-aqueous electrolytes. Commercially available lithium batteries generally use nonaqueous electrolytes to cope with lithium’s reactive nature, while most other primary batteries use aqueous electrolytes. So, in general lithium batteries are better able to perform at very low temperatures (below -20 °C or so) than other sorts of batteries.

When cost is not a major concern, or when only lithium batteries can meet your performance requirements

Some applications are relatively cost insensitive.  For instance, military/aerospace and medical device applications are generally not cost sensitive.  Moreover, depending on the industry there are various approvals which your device may need (MIL-SPEC, FDA, and so on).  These sorts of standards may very well convince you to initially go with a conventional battery chemistry, and a desire for high performance would lead you to going with lithium batteries. 

Your application—whatever it is—may also have stringent requirements for power and energy. Depending on how high you want to go, you may be stuck with lithium batteries. Normally, energy is expressed as Watt-hours per liter (that is, the total capacity divided by battery volume); this allows you to compare chemistries apples-to-apples. As seen in the table below, which is sourced from a variety of places including Linden’s battery handbook, going over ~400 W-h/L generally requires a lithium battery; while zinc-air batteries do offer exceptional energy density, they are generally low power, and have a relatively short service life once placed in operation due to self-discharge in air.

System

     W-h/L     

Rechargeable?

Zinc-air

950

No

Lithium-CF(x)

780

No

Lithium-thionyl choride

715

No

Lithium-iron disulfide

500

No

Lithium-MnO2

535

No

Lithium-SO2

415

No

Alkaline Zn-MnO2

400

No

Carbon-Zinc

165

No

Li-Ion

570

Yes

Li-Ion poly

350

Yes

Ni-Mh

370

Yes

Ni-Cd

170

Yes

SLA

70

Yes

When you want a single cell that is compatible with the voltage your electronics accepts.

Many electronic components are designed to work at around 3 V; for the sake of comparison most lithium batteries operate in the range of 2.5 – 3.5 Volts. Meanwhile, most aqueous batteries operate at 1.1 – 1.6 Volts, requiring two batteries to supply sufficient voltage to power many applications. The higher voltage of lithium also provides a significant advantage for higher power application (Power=Voltage x Current). Furthermore, there are plenty of electronic components in the market that have been designed to operate with batteries in this voltage range.

So do you think a lithium battery meets all or most of your battery requirements?  If yes, then this is no doubt a great option for you. If custom battery still seems like an attractive option for you, contact us to learn more about how we may help you.

About the Author

John

Hi, I'm John, editor-in-chief of an Flexel Battery online magazine!

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