Synthesis of Garnet LLZO by Aliovalent Co-Doping, and Electrochemical Behavior of Composite Solid Electrolyte for All-Solid Lithium Batteries

• Published in: Journal of the Electrochemical Society 2022-12, Vol.169 (12), p.120506
• Main Authors: Kim, Min-Young, Kang, Byeong-Su, Song, Young-Woong, Park, Sang-Jun, Lim, Jinsub, Kim, Hyungchan, Hong, YoungSun, Kim, Ho-Sung, Han, Jong-Hun
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1945-7111/aca6a3

Garnet-like Ga- M ( M = Ta, Rb, Y) co-doped Li 7 La 3 Zr 2 O 12 powders are prepared by the Taylor reaction, including Ga-LLZO, Ga-Ta LLZO, Ga-Rb LLZO, and Ga-Y LLZO. The lattice constant (12.97 Å) and large crystallite size (866 Å) of Ga-Rb LLZO powder enabled the highest ionic conductivity (2.03 × 10 –3 S cm −1 at 25 °C) in the pellet form. Moreover, Ga-Rb LLZO powders are calcined in various temperature range and are utilized in composite solid electrolyte sheets consisting of Ga-Rb LLZO, polyethylene oxide, and salts. The ionic conductivity of the CSE sheets is increased in proportion to the calcination temperature in the range of 2.43 × 10 −4 to 8.60 × 10 −4 S cm −1 at 70 °C. The LLZO particle-size and crystallite-size requirements are differ for the cathode and CSE sheet. Three types of all-solid-state lithium batteries are designed, among which all-solid lithium batteries-3 employing Ga-Rb LLZO powder calcined at 900 °C and 1100 °C for the cathode and CSE sheet, respectively, exhibits an initial capacity of ∼139 mAh g −1 at 0.1C and 70 °C, with a capacity retention of ∼92% after 100 cycles. In particular, in terms of rate characteristics, 1C compared to 0.1C capacity shows excellent value, maintaining about 85%. Garnet-like Ga- M ( M = Ta, Rb, Y) co-doped Li 7 La 3 Zr 2 O 12 powders are prepared by Taylor reaction. Ga-Rb LLZO pellet shows the highest ion conductivity as 2.03 × 10 −3 S cm −1 at 25 °C. The controlled particle size of the solid electrolyte is important to apply composite electrode and CSE sheet in ASLBs. The optimized cell design (ASLB-3) shows enhanced rate capability at 70 °C.