Electrochemical Stability and Performance of Li2OHCl Substituted by F or Br as Solid-State Electrolyte

Abstract Li2(OH)0.9F0.1Cl, Li2(OH)0.9Br0.1Cl, and Li2OHCl0.8Br0.2 solid electrolytes were synthesized and compared with Li2OHCl to analyze the exact improvement mechanism for Li+ conductivity and electrochemical stability of Li2OHX-type solid electrolyte. The substituted materials exhibit improved electrochemical stability and Li+ conductivity Li2OHCl. Among these materials, Li(OH)0.9F0.1Cl has improved Li+ conductivity due to a reduction of the OH– concentration and the conductivity of Li2OHCl0.8Br0.2 was also increased compared with Li2OHCl due to the large interstitial site. In the case of Li2(OH)0.9Br0.1Cl, it had the highest Li+ conductivity and good Li+ migration by both effects because of a larger interstitial site and low OH− concentration. Furthermore, the electrochemical stability of four materials was compared due to the different structural stabilities and strengths of binary chemical bonds such as Li–X, H–X, and O–X. Comparing the Li+ conductivity of Li2(OH)0.9F0.1Cl and Li2OHCl0.8Br0.2, the Li+ conductivity is influenced by the OH− concentration unlike the other mechanisms.