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

Abstract

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 (LiNi1/3Mn1/3Co1/3O2 (NMC) or LiNi0.5Mn1.5O4 (LNMO)), solid electrolyte particles Li1.3Al0.3Ti1.7(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.