High-voltage superionic and humidity-tolerant Li2.5Sc0.5Zr0.5Cl6 conductor for lithium batteries via preferred orientation

Chloride solid electrolytes (CSEs) have good compatibility with commercial oxide cathode materials and show great potential for application in all-solid-state Li metal batteries (ASSLMBs). However, achieving simultaneously low cost, high ionic conductivity, excellent moisture tolerance, and robust electrochemical stability with >4 V-class cathodes for CSEs remains challenging. Herein, we report a facile Zr substitution strategy to increase the degree of preferred orientation and lower the Li + diffusion barrier of the (001) plane, i.e. the ab plane, of Li 3 ScCl 6 , thus boosting the ion conduction kinetics and framework stability. As such, Li 2.5 Sc 0.5 Zr 0.5 Cl 6 exhibits a high conductivity of 2.23 mS cm −1 and low activation energy of 0.26 eV at room temperature (RT). ASSLMBs are constructed using a LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode, Li 2.5 Sc 0.5 Zr 0.5 Cl 6 electrolyte, and Li-In anode, and deliver an exceptional initial Coulombic efficiency of 89.6 % at RT and can run stably over 200 cycles with 90 % capacity retention at 0.2C. In-situ electrochemical impedance inspection of the battery further reveals a high interfacial stability between Li 2.5 Sc 0.5 Zr 0.5 Cl 6 and LiNi 0.8 Co 0.1 Mn 0.1 O 2 . Moreover, Li 2.5 Sc 0.5 Zr 0.5 Cl 6 demonstrates high wet fatness with a preserved structure stability and high ionic conductivity after exposure to atmosphere with 5 % relative humidity. Such humidity tolerance and cost-effectiveness solve two major obstacles for the application of CSEs.