Invited Talk: React-in-Place Battery Electrodes for Large Scale Energy Storage

We present a coupling of synthesis and deposition procedures for large scale, high performance electrochemical energy storage electrodes.  We will use inkjet deposited precursors to create oxides, hydroxides, sulfides, and phosphates from combinations of  a range of homogeneous liquid precursors.  A range of equilibrium (e.g. hot/cold stage) and nonequlibrium (laser) post processing tools have been built into the machine to allow for control of both chemical kinetics and morphology.  

At first this coupling may seem counterintuitive.  The separation of active material synthesis and deposition allows for chemists and process engineers to optimize for two differents operations rather a single operation as we proposed above.  The problem with this decoupled approach is that battery electrodes suffer from the difficult problem of “repeatable painting of high mass loaded slurries.”  Inch-to-inch and batch-to-batch the electrode has variations in porosity and active material mixing that in the worst electrodes leads to inconsistent capacity and in the all electrodes leads to inconsistent impedance as a function of position and electrode number.  For low rate, low cycle systems this impedance mismatch is less of a problem, but as higher rates are demanded for longer cycle lifes in smaller form factors (e.g. high performance portable electronics, electric vehicles), the uncertainty of  the art of slurry casting becomes a significant challenge for industry.  Beyond this, the poor ordering and rough surfaces left by traditional slurry casting and provide difficulties for creating batteries for conformal/flexible applications.

This is a recognized problem and there are many efforts which are recoupling materials processing and device processing to solve this problem, including layer-by-layer electrode assembly and co-extrusion processes.  Our effort furthers this recoupling by creating the desired structure repeatedly at the correct locations at high throughput and with heretofore unrealized layer registration for batteries.  

Inkjet printers have exceptional reliability and repeatability with liquid-only inks, while nanoparticle laden inks either 1) quickly clog heads at high solid mass loading or 2) result in isolated/poorly percolated particle coatings at low solid mass loading.  This is acceptable for typographic inks, certain sensor systems, and catalyst links, but not for electrochemical energy storage systems.  By jetting and mixing chemical precursors on sorbet substrates, we can accomplish two goals

1) at a laboratory scale we can using combinatorial methods to test non-stoichiometric, many component and/or composite structures for optimal processes

2) at a production scale we can synthesis the same structure with 10 µm precission over many meters of film per hour.