Solid state lithium ion batteries are generally safer than liquid electrolytes. Li6PS5Cl is a promising electrolyte with an instability in the active material and electrolyte interphase which causes an increase in impedance and capacity loss.
Doping with stable salts of LiCl and LiF could affect the stability. It is found that doping LiCl reduces the specific capacity retention despite having higher ionic conductivity from EIS. With the ex-situ XRD analysis, it is found that the decomposition is less than of pristine argyrodite. This could be due to poor interphase contact. In the case of dopant LiF, small doping of the argyrodite decreases the specific capacity retention of the active material which may be due to lowered ionic conductivity. The higher amount of LiF doped argyrodite improves the specific capacity retention despite the lower ionic conductivities. This could be due high decomposition rate. Alternatively, another doping method was used, but it was found to have higher chemical decomposition despite having good specific capacity retention. To improve the quality of this research, better synthesis of the argyrodite is preferred as this research has side phases. Further analysis that could be included are: TEM, XRD in-operando mode, and EDS.