Lithium Garnet Li₇La₃Zr₂O₁₂ Electrolyte for All‐Solid‐State Batteries: Closing the Gap between Bulk and Thin Film Li‐Ion Conductivities

Abstract

The high ionic conductivity and wide electrochemical stability of the lithium garnet Li7La3Zr2O12 (LLZO) make it a viable solid electrolyte for all‐solid‐state lithium batteries with superior capacity and power densities. Contrary to common ceramic processing routes of bulk pellets, thin film solid electrolytes could enable large‐area fabrication, and increase energy and power densities by reducing the bulkiness, weight and critically, the area‐specific resistance of the electrolyte. Fabrication of LLZO films has nonetheless been challenging because of lithium losses and formation of impurity phases that result in low densities and poor ionic conductivities as compared to bulk pellets. Here, a scalable method for fabricating submicron films of LLZO employing co‐sputtering from doped LLZO and Li2O targets is presented. A record ionic conductivity of 1.9 × 10−4 S cm–1 is measured for dense and uniform cubic‐phase Ga‐substituted LLZO films annealed at 700 °C in oxygen, which is comparable to the values in high‐temperature sintered pellets and outperforms by one order of magnitude the latest record for LLZO thin films as well as the typical conductivities in the well‐established LiPON electrolyte. This result is an important milestone to realize all‐vacuum deposited solid‐state batteries with higher power density.

Blocking Lithium Dendrite Growth in Solid-State Batteries with an Ultrathin Amorphous Li-La-Zr-O Solid Electrolyte

“…At lower LLZO:Li 2 O mass fractions, the ionic conductivity decreases again although not as abruptly as in the low Li 2 O fraction region. In contrast, the electronic conductivity remains fairly constant at 1 × 10 −14 S cm −1 for different mass fractions of LLZOand Li 2 O, seven orders of magnitude below the best ionic conductivity measured and about six orders of magnitude below reported values for bulk and thin-film crystalline LLZO 8,17.…”

“…In this way it is possible to prepare ultrathin conformal and grain-boundary free films that can act as injection barrier for electrons while allowing LLZO thin films,. 16,17 Besides compensating lithium losses, it is an effective way to tune the Li-ion concentration in the electrolyte film and modify its electrochemical properties.…”

Pulsed Laser Deposition as a Tool for the Development of All Solid‐State Microbatteries

“…While the deposition of stoichiometric crystalline LLZO by co‐sputtering of Li 2 O and LLZO was recently reported, [140] high temperatures PLD depositions still present difficulties. The presence of heavy elements, like Zr and La, leads to a significant lithium deficiency and stabilization of the La 2 Zr 2 O 7 pyrochlore phase.…”

How interdiffusion affects the electrochemical performance of LiMn2O4 thin films on stainless steel

“…[1][2][3][4][5][6][7] Furthermore, Li-ion conductive ceramics, e.g. Li 7 La 3 Zr 2 O 12 (LLZO) [8][9][10][11] or Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP), 12,13 and glassy lithium phosphorus oxynitrides (LIPON) 14,15 form a stable solid electrolyte interface (SEI) or have a higher potential window up to 5 V vs. Li/Li + , so that less degradation of the electrolyte is expected and the implementation of high-voltage active materials might be feasible. [16][17][18] Li et al demonstrated, for instance, a highvoltage LiMn 1.5 Ni 0.5 O 4 TF-SSB using a LIPON electrolyte with a capacity retention of 90.6% after 10 000 cycles and a coulombic efficiency of almost 100%.…”