Fabrication and electrochemical properties of electrode composites for oxide-type all-solid-state batteries through...

All-solid-state batteries, which use flame-resistant solid electrolytes, are regarded as safer alternatives to conventional lithium-ion batteries for various applications including electric vehicles. Herein, we report the fabrication of cathode composites for oxide-type all-solid-state batteries through an electrostatic assembly method. A polyelectrolyte is used to adjust the surface charge of the matrix particles to positive/negative, and the aggregation resulting from electrostatic interactions is utilized. Composites consisting of cathode active material particles (LiNi_1/3Mn_1/3Co_1/3O₂ (NMC) or LiNi_0.5Mn_1.5O₄ (LNMO)), solid electrolyte particles Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP), and electron conductive one-dimensional carbon nanotubes (CNT) are formed via an electrostatic integrated assembly of colloidal suspensions. Electrostatic integration increases the electronic conductivity by two orders of magnitude in the NMC-LATP-CNT composite (6.5 × 10^-3 S cm^-1/3.2 × 10^-5 S cm^-1) and by six orders of magnitude in the LNMO-LATP-CNT composite (6.4 × 10^-3 S cm^-1/2.3 × 10^-9 S cm^-1). The dispersion of CNTs in the cathode composite is enhanced, resulting in percolation of e^- path even at 1 wt% (approximately 2.5 vol%) CNT. This study indicates that an integrated cathode composite can be fabricated with particles uniformly mixed by electrostatic interaction for oxide-type all-solid-state batteries.