Ming Jiang

 

Construction of a thin-film all-solid-state battery by metal-organic CVD

Schematic of MO-CVD process (left) and electrochemical testing cell after [1](right) Copyright: M. Jiang/ M.E. Donders, et al. Schematic of MO-CVD process (left) and electrochemical testing cell after [1](right)

Because of the unmatchable combination of high energy and power density as well as their promising development prospect, rechargeable lithium-ion batteries (LIBs) have become important components of the various energy storage systems and electric devices. Yet, if LIBs are widely used in embedded electric devices (such as micro artificial cardiac pacemaker and micro sensor) in the future, they should meet much stricter safety standards under the various working conditions. Commercial LIBs are mostly based on liquid electrolytes, which imply the inherent risk of leakage and danger of ignition. Such problems can be overcome in all-solid-state batteries, employing a ceramic Li-ion conductor as the electrolyte. Various deposition strategies have been explored to fabricate ceramic thin films. In particularly, CVD process is capable of producing highly conformal coatings with excellent controllability and relatively fast deposition rate. To further improve the deposition efficiency, many enhancement techniques are employed in CVD and developed into low-pressure CVD (LP-CVD) and metal-organic CVD (MO-CVD). From all of these CVD techniques, MO-CVD is attracting more and more attention in thin-film ceramic processing. MO-CVD is a versatile technique for fabricating films at high deposition rates and moderate vacuum conditions (several hundred mbar compared to atmospheric pressure), which is highly controllable for film morphology and phase formation, the wide range of metal-organic compounds resources also provides broad application. LFP (LiFePO4) thin film batteries will be grown in the Aixtron 200 RF Chemical Vapour Deposition Reactor System, by using tert-butyllithium (t-BuLi), trimethylphosphate (TMPO), ferrocene (FeCp2) and oxygen as precursors (see Figure on the left). The carrier gas will be Argon. The deposition temperature on substrate surface will be investigated from 300 to 450oC. The morphology and structure information of as-deposited thin-film will be investigated by SEM, XRD, XPS and other measurements. Three electrodes cell system will be used in the electrochemical test (see Figure on the right). Vital tests such as cyclic voltammetry, impedance spectroscopic and cycling stability will be conducted to evaluate the electrochemical performance of obtained samples.

Reference:

  1. M.E. Donders, et al., J. Electrochemical Society, 2013, 160(5) A3066-A3071.