Aerosol Engineering of Battery Electrodes: A Review of a Decade of Spray Drying and Spray Pyrolysis of Intercalation and Conversion Materials

ADAM M BOIES, Manar Almazrouei, Maurits Houck, Jean de La Verpilliere, Michael De Volder, University of Cambridge

     Abstract Number: 504
     Working Group: Nanoparticles and Materials Synthesis

Abstract
Modern lithium ion battery electrodes materials require precise morphology and crystalline structure to achieve high energy density, rate performance and cycle stability. Aerosol processes offer tools to impart desired morphological structure and material chemistry to high throughput production. This presentation details the last decade of work to synthesize battery electrode materials using both spray drying and high temperature spray pyrolysis that has moved from academic lab to industrial production. The ability to control particle morphology of desired chemistries with sizes ranging from 100 nm to 10 µm is an asset of spray processes. However, spray processes alone cannot provide sufficient residence times to achieve desired crystallinity, requiring costly post processing.

The presentation will detail the aerosol production of anode materials consisting of lithium conversion materials consisting of aluminium iron oxide and iron silicide particles stabilized with carbons. The reaction front of lithiation within the particles induces swelling and structural expansion of the powders upon electrochemical cycling. The morphology imparted by aerosol processing is critical to controlling the swell/shrink material properties, and thus the rate performance and overall cycle life of the materials. Hysteresis in charge-discharge processing leads to heat generation within the anode materials that can be dissipated by nano-scale carbon materials. The localized heat generation does not impede operation within individual cells, but at the pack level requires additional cooling systems that limits widescale adoption.

Alternatively, layered metal oxides that allow the intercalation of lithium ions within a robust crystalline lattice do not suffer from large hysteresis cycles, and thus overcome the limitations of heat generation. The production of mixed niobium oxide (e.g. Nb2O5) anode materials and layered cathode materials, such as lithium cobalt oxide (LCO) and nickel manganese oxide (NMC) can be achieved by aerosol processing. The resulting energy density, power density and cycle life of such engineered materials can rival or exceed materials produced by other processes. However, post processing the sprayed powders requires time consuming (hours) calcination steps in stationary high temperature (300-1000 °C) furnaces to achieve the desired layered crystalline structure properties. Thus, there are further opportunities for the development of advanced aerosol processes that achieve higher temperatures and prolonged residence times for greater efficiency of material production.