Why though? The main benefit of solid state is the energy density, which is not at all important for a stationary, grid-connected system. It's also super expensive. Why not just stick with sodium-ion batteries for the grid which are way cheaper per kWh?
I like that its green, but is really more strategic on their part. China has just a small fraction of domestic petroleum production of other countries like the USA or Russia. This means China is vulnerable to other countries that they depend on for petroleum imports to feed their people and produce economically.
Every effort to shift energy production (and storage) to domestic ways means less dependence on other nation's energy exports.
