Emerging Role of Non-crystalline Electrolytes in Solid-State Battery Research

et al. 2021

Preprint

Lithium metal dendrites have become a roadblock in the realization of next-generation solid-state batteries with lithium metal as high-capacity anode. The presence of surface and bulk inhomogeneities with non-negligible electronic conductivity in crystalline electrolytes such as the lithium garnet Li7La3Zr2O12 (LLZO) facilitates the growth of lithium filaments, posing a critical safety risk. Here we explore the amorphous phase of LLZO (aLLZO) as a lithium dendrite shield owing to its grain-boundary-free microstructure, stability against metallic lithium, and high electronic insulation. We demonstrate that by tuning the lithium stoichiometry in sputtered aLLZO films, the ionic conductivity can be increased up to 10-7 S cm-1 while retaining an ultralow electronic conductivity of 10-14 S cm-1. In Li/aLLZO/Li symmetric cells, plating-stripping results in no degradation of the films and current densities up to 3.2 mA cm-2 can be applied with no signs of lithium penetration. The defect-free and conformal nature of the films enables microbatteries with an electrolyte thickness as low as 70 nm, which withstand charge-discharge at 0.2 mA cm-2 for over 500 cycles. Finally, we demonstrate that the application of aLLZO as a coating on crystalline LLZO lowers the interface resistance and significantly impedes the formation of lithium dendrites, increasing the critical current density of a symmetric cell up to 1.3 mA cm-2 at room temperature and without external pressure. The effectiveness of the amorphous Li-La-Zr-O as lithium dendrite blocking layer can accelerate the development of more powerful and safer solid-state batteries.<div></div>

supporting

confidence: 91%

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

Sastre

Futscher²,

et al. 2021

Preprint

“…This is consistent with findings on other amorphous solid electrolytes such as lithium thiophosphate (LPS) and lithium phosphorus oxynitride (LiPON). 28 Above a critical mass fraction we assume that the added Li + ion forms aggregates which reduce the ion conductivity, as suggested by the obtained mobile Li + ion density, which does not increase further after the critical mass fraction of 0.66 LLZO:Li 2 O is reached.…”

Section: Resultsmentioning

confidence: 71%

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

Sastre¹,

Futscher²,

et al. 2021

Preprint

Lithium metal dendrites have become a roadblock in the realization of next-generation solid-state batteries with lithium metal as high-capacity anode. The presence of surface and bulk inhomogeneities with non-negligible electronic conductivity in crystalline electrolytes such as the lithium garnet Li7La3Zr2O12 (LLZO) facilitates the growth of lithium filaments, posing a critical safety risk. Here we explore the amorphous phase of LLZO (aLLZO) as a lithium dendrite shield owing to its grain-boundary-free microstructure, stability against metallic lithium, and high electronic insulation. We demonstrate that by tuning the lithium stoichiometry in sputtered aLLZO films, the ionic conductivity can be increased up to 10-7 S cm-1 while retaining an ultralow electronic conductivity of 10-14 S cm-1. In Li/aLLZO/Li symmetric cells, plating-stripping results in no degradation of the films and current densities up to 3.2 mA cm-2 can be applied with no signs of lithium penetration. The defect-free and conformal nature of the films enables microbatteries with an electrolyte thickness as low as 70 nm, which withstand charge-discharge at 0.2 mA cm-2 for over 500 cycles. Finally, we demonstrate that the application of aLLZO as a coating on crystalline LLZO lowers the interface resistance and significantly impedes the formation of lithium dendrites, increasing the critical current density of a symmetric cell up to 1.3 mA cm-2 at room temperature and without external pressure. The effectiveness of the amorphous Li-La-Zr-O as lithium dendrite blocking layer can accelerate the development of more powerful and safer solid-state batteries.

“…This is consistent with findings on other amorphous solid electrolytes such as lithium thiophosphate (LPS) and lithium phosphorus oxynitride (LiPON). 24 Above a critical mass fraction we assume that the added Li + ion forms aggregates which reduce the ion conductivity, as suggested by the obtained mobile Li + ion density, which does not increase further after the critical mass fraction of 0.66 LLZO:Li 2 O is reached. The aLLZO films here investigated can be utilized as ultrathin electrolyte for thin-film solid-state batteries.…”

mentioning

confidence: 71%

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

Sastre

Futscher²,

et al. 2021

Preprint

Lithium garnet Li7La3Zr2O12 (LLZO) electrolyte is a potential candidate for the development of solid-state batteries with lithium metal as high-capacity anode. But ceramic LLZO in the form of pellets or polycrystalline films can still suffer from lithium dendrite penetration because of surface and bulk inhomogeneities and grain boundaries with non-negligible electronic conductivity. In contrast, the amorphous phase of LLZO (aLLZO) possesses a grain-boundary-free microstructure with moderate ionic conductivity (10-7 S cm-1) and high electronic insulation (10-14 S cm-1), which in the form of thin coatings can offer resistance to lithium dendrite growth. We explore the electrochemical properties and applications of aLLZO ultrathin films prepared by sputtering deposition. The defect-free and conformal nature of the films enables microbatteries with an electrolyte thickness as low as 70 nm, which withstand charge-discharge at 0.2 mA cm-2 for over 500 cycles. In Li/aLLZO/Li symmetric cells, plating-stripping at current densities up to 3.2 mA cm-2 shows no signs of lithium penetration. Finally, we show that the application of aLLZO as a coating on LLZO ceramic pellets significantly impedes the formation of Li dendrites.