operating life with an annual
self-discharge rate of two to three
percent per year, while a superior
grade LiSOCL2 battery can have a
much lower annual self-discharge
rate of just 0.7 percent per year,
permitting maintenance-free operation for up to 40 years.
The Evolution of Consumer
Grade Rechargeable Batteries
The first consumer rechargeable
batteries were developed back in
the mid-nineteenth century using
Nickel Cadmium (NiCad) chemistry.
These batteries are large, have low
energy density, and suffer from
memory effect, whereby the battery does not fully recharge if it is
not fully depleted.
The next major development was
the Nickel-Metal Hydride (NiMH)
battery, which eliminated the memory
effect problem, but still suffered from a
high annual self-discharge rate, making
them incapable of delivering extended storage life.
Another key breakthrough was the con-
sumer grade lithium ion (Li-ion) battery,
which features high efficiency and high
power output. Best known is the ubiquitous
18650 Li-ion cell, which was developed by
laptop computer manufacturers for use
in their own products. Since these laptop
computers were intended for planned
obsolescence,18650 cells only had to oper-
ate for approximately five years and 500
full recharge cycles, with a temperature
range from - 20° to 60°C. Consumer grade
Li-ion cells also experience a gradual deg-
radation of the cathode, making the battery
less receptive to future recharging, further
reducing battery operating life.
The introduction of low profile consumer devices, such as the smartphone and
tablet computers, led to the development
of lithium polymer batteries, also referred
to as laminate cells. These cells use sheets
of flexible material that can be rolled or
stacked like a deck of cards, with their positive and negative terminals protruding from
the cell as tabs. As a result, lithium polymer
batteries can be very thin, or quite large,
depending on the application.
Unlike standard batteries, which are constructed with a protective steel or aluminum
outer can, lithium polymer cells have no
outer protective layer, so they are prone to
puncture, which can result in an internal
short circuit or premature self-discharge. A
lithium polymer battery can also swell in size.
Fitting a Growing Need
To meet the growing need for industrial
grade rechargeable batteries, companies
are working to develop products that
can provide up to 20 years of service life
with a low annual self-discharge rate, and
These advances will help fill the performance gap between short-lived batteries
intended for consumer applications and
those that can deliver the ruggedness and
long-term reliability required to power
industrial grade remote wireless devices. PDD
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