A New Method for Fabrication of Solid State Batteries

Commercially available solid-state lithium and lithium-ion batteries with inorganic electrolytes are typically low capacity, low energy density and high cost devices.  This paper discusses a new manufacturing technology with the potential to enable the development of high capacity solid-state batteries with very high energy density at very low cost.

The process is called Battery-on-Wire (BoW) and is shown in Fig. 1.  It consists of a single, cylindrical vapor phase reactor with multiple reactor zones.  A metal wire, which acts as the cathode current collector, is continuously fed into the top of the reactor and cathode, electrolyte, anode and anode current collector layers are sequentially deposited on the wire.  The result is a complete solid-state cell in the form of a thin flexible wire.

                A wide variety of anode, electrolyte and cathode materials can be deposited by judicious selection of reactants.  Electrode and electrolyte morphology and chemical composition can be modified by controlling the reactor temperature and the partial pressures of the reactants.  The various reactor sections are isolated to prevent cross contamination and the deposition rates are usually several orders of magnitude higher than those in the processes typically used to fabricate solid-state batteries with inorganic electrolytes. 

Fig. 2 shows SEM images of anode, cathode and electrolyte deposits.  The anode and cathode coatings exhibit some porosity and surface roughness with surface features on the order of 1-2 μm.  The electrolyte coating is smooth and non-porous.

                Fig. 3 shows initial cycle life data for a Si-based anode.  There is some capacity fade in the early cycles but the discharge capacity is almost constant after cycle 5 and the coulombic efficiency is near 100% after cycle 10.   The specific capacity of the anode material is estimated to be between 2500 and 3000 mAh/g.  Additional data for anode, cathode and electrolyte materials and complete cells will be shown in the presentation.