Solid-state Li-ion batteries operating at room temperature using new borohydride argyrodite electrolytes

TL;DR

This study introduces a new borohydride-substituted argyrodite electrolyte enabling room-temperature solid-state Li-ion batteries with promising cycling stability, especially with TiS2 cathodes, highlighting improved interfacial compatibility and capacity retention.

Contribution

The paper reports the development of a novel borohydride-argyrodite electrolyte that enables room-temperature operation of Li-ion batteries with enhanced cycling performance.

Findings

Reversible cycling with both oxide and sulfide cathodes.

Lower interfacial resistance with TiS2 compared to NMC.

At least 35 cycles with >97% coulombic efficiency for TiS2 cathode.

Abstract

Using a new class of (BH4)- substituted argyrodite Li6PS5Z0.83(BH4)0.17, (Z = Cl, I) solid electrolyte, Li-metal solid-state batteries operating at room temperature have been developed. The cells were made by combining the modified argyrodite with an In-Li anode and two types of cathode: an oxide, LixMO2 (M = 1/3Ni, 1/3Mn, 1/3Co; so called NMC) and a titanium disulfide, TiS2. The performance of the cells was evaluated through galvanostatic cycling and Alternating Current AC electrochemical impedance measurements. Reversible capacities were observed for both cathodes for at least tens of cycles. However, the high-voltage oxide cathode cell shows lower reversible capacity and larger fading upon cycling than the sulfide one. The AC impedance measurements revealed an increasing interfacial resistance at the cathode side for the oxide cathode inducing the capacity fading. This resistance was attributed to the intrinsic poor conductivity of NMC and interfacial reactions between the oxide material and the argyrodite electrolyte. On the contrary, the low interfacial resistance of the TiS2 cell during cycling evidences a better chemical compatibility between this active material and substituted argyrodites, allowing full cycling of the cathode material, 240 mAhg-1, for at least 35 cycles with a coulombic efficiency above 97%.