Interphase Formed at Li_6.4La₃Zr_1.4Ta_0.6O₁₂/Li Interface Enables Cycle Stability for Solid‐State Batteries

Abstract

Garnet‐type Li6.4La3Zr1.4Ta0.6O12 (LLZTaO) is considered a promising solid‐state electrolyte (SSE) for all‐solid‐state batteries (SSBs), but LLZTaO/Li interfacial issues limit their power density. The key question of whether LLZTaO does or does not form an interphase layer before and at the initial stage of electrochemical cycling remains debatable. An XPS interface approach, electrochemical cycling, and an electrochemically coupled phase field model to study the dynamic changes of interfacial resistance during cycling are utilized, and it is found that the generation rate of the interphase via electrochemical reaction processes at the LLZTaO/Li interface depends on the applied current density. For a Li/LLZTaO/Li cell, the impedance and overpotential increase gradually at the initial stage of electrochemical cycling at a current density of 0.1 mA cm–2 due to the formation of a passivating reaction zone (interphase) at LLZTaO/Li interface, which can protect the LLZTaO from being continuously reacted. With increasing the current density to 0.5 mA cm–2, the electrochemical reaction is suppressed and tied to uneven Li ion transport across the LLZTaO/Li interface on plating, leading to a short circuit of the cell. Understanding how interface dynamic transformations influence electrochemical degradation is helpful to stabilize these interfaces in SSBs.

Enabling High‐Voltage “Superconcentrated Ionogel‐in‐Ceramic” Hybrid Electrolyte with Ultrahigh Ionic Conductivity and Single Li+‐Ion Transference Number

“…The signal of Ta was also detected from the Ta 4f spectra at binding energies of 25.7 and 27.8 eV (Figure 3h). [ 43 ] Thus, the data obtained demonstrates the integrated structure of the SIC electrolyte.…”

CO2 Laser Sintering of Garnet-Type Solid-State Electrolytes

“…Among these SSEs, only oxides show wide electrochemical windows that enable pairing with high voltage cathodes (up to 5 V vs Li + /Li) and Li-metal anodes, 22,23 making them promising SSEs toward the realization of high power and high energy density batteries. 24−27 A representative of the garnet-type SSEs, Ta-doped Li 7 La 3 Zr 2 O 12 (e.g., Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO)), 28−31 has been receiving considerable attention because of its out-standing chemical compatibility with Li-metal 23,32 and layeredoxide cathodes, 33 high room-temperature (RT) ionic conductivity (∼1 mS•cm −1 ), 28,34,35 and environmental friendliness. 28 However, this promising LLZTO-garnet electrolyte suffers from poor sinterability; 34,36 elevated sintering temperatures (typically ≥1100 °C), long sintering time (10−40 h) and high packing density of the SSE green body (i.e., high hydraulic press pressure (hundreds of MPa)) are general requirements to yield highly dense LLZTO SSEs.…”

Recent advances in in situ and operando characterization techniques for Li7La3Zr2O12-based solid-state lithium batteries

“…Similarly, depth profile XPS also revealed the reduction of Zr 4+ and generation of Li-O species at the Ta-LLZO/Li interface. 132 The formation rate of ODI is highly affected by current density at the interface. At low current densities, ODI has a passivation effect to protect LLZO from sustained reduction and constrain interfacial resistance.…”