A novel, new method has been developed to cheaply produce better lithium cobalt phosphate electrodes

By Gary Elinoff, contributing writer

Lithium_Cobalt_Phosphate_Crystals

Lithium cobalt
phosphate crystals viewed with an electron microscope. Image source: Katia Rodewald/TUM.

It’s
no secret that the limited storage capacity of rechargeable batteries is
perhaps the single greatest factor impeding the more widespread adaptation of
electric vehicles. It’s also the reason why, in the designing and development
of chips for any type of mobile device, beyond any other goal is the need for
the finished product to require as little operating power as possible.

Lithium cobalt phosphate electrodes

Lithium-ion
batteries (LIB) employing cathodes composed of lithium cobalt phosphate have
long been an engineering favorite because of their higher energy density when
compared to the now-ubiquitous devices employing lithium iron phosphate
cathodes, also known as the beltway
battery
. The
comparison is stark; lithium cobalt phosphate batteries can store about 800
watt-hours of power for each kilogram of battery weight, while the lithium iron
phosphate design clocks in at about 600 watt-hours.

Until now, producing
lithium cobalt phosphate has been difficult. The process needed to take place
at 800°C and produced crystals of unpredictable size. Those
crystals, in any case, then had to be reduced to a nanocrystalline powder in a subsequent manufacturing process that required a large
energy investment.

Synthesizing crystals in a
microwave oven

As described in an article from the
Technical University of
Munich
(TUM), Dr. Jennifer Ludwig has found a way to produce nanocrystalline lithium cobalt
phosphate crystals more quickly, and the method only requires heating to 250°C, which Dr. Ludwig generated in an ordinary microwave oven.
The process also obviated the previous method’s second step as the crystals
produced were smaller than 1 μm across, with a thickness
measured in hundreds of nanometers. “This shape
ensures better electrochemical performance because the lithium ions need to
move only short distances within the crystals,” said Ludwig.

But there
were some problems along the way. An undesirable compound of cobalt hydroxide
hydrogen phosphate was occasionally created by the high pressures involved in
the synthesis. Fortunately, Ludwig was able to modify the procedure to avoid
its production. “With this new production
process, we can now create high-performance, platelet-shaped lithium cobalt
phosphate crystals with tailored properties in high quality,” said Tom Nilges, within whose group Dr. Ludwig works.

Another
advantage of lithium cobalt phosphate batteries is that they produce somewhat
higher voltages than do other LIBs, which is one of the reasons for the
increased energy density. Research in LIBs is one of the hottest topics in
technology today. Increased safety and speed of charging are also vital
concerns, and major automobile companies such as Toyota are taking notice. One thing’s for
sure: Power on the go is in demand.