The organic electrolyte Li-ion batteries still surfer from safety concern especially when the energy density of the batteries is approaching the limits. Development of safe electrolytes is urgent needed. In recent five years, we focus on three non-flammable electrolytes; water-in-salt (WIS) aqueous electrolytes, all-fluorinated electrolytes, and solid state electrolytes. WIS electrolytes are intrinsic safe but have narrowed electrochemical stability window limiting the energy density of aqueous electrolyte batteries. By adding high concentrated salts in water, we successfully expend the electrochemical stability window to 3.0V. To further enhance the energy density, we also developed transition metal-free LiBr-LiCl-graphite cathodes that provides 240 mAh/g at 4.2V representing one of highest energy cathodes in Li-ion batteries. In addition, the Li dendrite formation in all- fluorinated electrolytes and solid state electrolytes also investigated.