  Heterogeneous multilayered solid-state electrolyte (HMSSE) has been widely
explored for their broadened working voltage range and compatibility with
electrodes. However, due to the limitations of traditional manufacturing
methods such as casting, the interface between electrolyte layers in HMSSE can
decrease the ionic conductivity severely. Here, a novel combinatory aerosol jet
printing (CAJP) is introduced to fabricate functionally graded solid-state
electrolyte (FGSSE) without sharp interface. Owing to the unique ability of
CAJP (in-situ mixing and instantaneous tuning of the mixing ratio), FGSSE with
smooth microscale compositional gradation is achieved. Electrochemical tests
show that FGSSE has excellent oxidative stability exceeding 5.5 V and improved
conductivity (>7 times of an analogous HMSSE). By decoupling the total
resistance, we show that the resistance from the electrolyte/electrolyte
interface of HMSSE is 5.7 times of the total resistance of FGSSE. The
Li/FGSSE/NCM622 cell can be stably run for more than 200 cycles along with
improved rate performance.
