Investigation of Lithium Deposition in Tri-Layer Llzo Garnet Structure As a Function of Cell Cycling Using Nuclear Reaction Analysis Method

Abstract

A key challenge of lithium metal batteries is the volumetric expansion of battery after several charging cycles due to the non-uniform deposition of lithium on anode. This leads to lithium dendrite formation compromising battery safety, and poor lifetime. We adapted tri-layer (porous-dense-porous) Al-doped Lithium Lanthanum Zirconium Oxide (LLZO) host (separator) via tape casting. During cycling lithium is deposited in the porous structure preventing dendrite formation. XRD analysis of annealed host structure confirmed presence of cubic phase LLZO which provides higher ionic conductivity. We measured Li distribution on LLZO host structure before and after different cell cycling conditions and investigated the failure mechanism. We performed concentration depth profiles of 7Li and 6Li isotopes by Nuclear Reaction Analysis (NRA) using two different methods: Proton Induced Gamma-ray Emission (PIGE) and Proton Induced Alpha-particle Reaction (Particle-Particle reaction) and compared the results for accuracy. Depth profile of 7Li confirmed 33 at % Li at 0.44µm thickness before cycling which was increased after cycling. The Gaussian distribution of NRA data indicated a uniform Li depth profile in the dense layer. Through electrochemical testing, we measured that Li capacity loss after 5 and 25 charging cycles with 0.1C rate, 1.51mAh and 2.89mAh, respectively, in tri layered LLZO separator.