Degradation Mechanism of All-Solid-State Li-Metal Batteries Studied by Electrochemical Impedance Spectroscopy

Abstract

Solid-state Li-metal batteries have the potential to achieve both high safety and high energy densities. Among various solid-state fast-ion conductors, the garnet-type Li7La3Zr2O12 (LLZO) is one of the few that are stable to Li metal. However, the large interfacial resistance between LLZO and cathode materials severely limits the practical application of LLZO. Here a LiCoO2 (LCO) film was deposited onto an Al-doped LLZO substrate at room temperature by aerosol deposition, and a low interfacial resistance was achieved. The LCO particles were precoated by Li3BO3 (LBO), which melted to join the LCO particles to the LLZO substrate at heating. All-solid-state Li/LLZO/LBO-LCO cells could deliver an initial discharge capacity of 128 mAh g–1 at 0.2 C and 60 °C and demonstrated relatively high capacity retention of 87% after 30 cycles. The cell degradation mechanism was studied by electrochemical impedance spectroscopy (EIS) and was found to be mainly related to the increase of the interfacial resistance between LBO and LCO. In-situ SEM analysis verified the hypothesis that the increase of the interfacial resistance was caused primarily by interfacial cracking upon cycling. This study demonstrated the capability of EIS as a powerful nondestructive in-situ technique to investigate the failure mechanisms of all-solid-state batteries.

Evolution Process of the Interfacial Chemical Reaction in Ni-Rich Layered Cathodes for All-Solid-State Batteries

“…In order to determine the electrochemical states of the ASSBs in different cycling states, the interfacial stabilities of different cells were investigated using EIS. 3 The Nyquist plots for NCM-00, NCM-200, NCM-500, and NCM-1000 are shown in Figure 2A,B.…”

Polydopamine-Based Polymer Layer for Enhanced Interfacial Properties of Hybrid Ceramic–Polymer Solid Electrolytes

“…The EIS measurements were taken at every 5 °C temperature increasing from 25 to 60 °C, with at least 30 min to reach thermal equilibrium between any two successive measurements. In potentiostatic conditions, the EIS technique was used to measure the impedance of a system, by detecting the current responses to small-amplitude sinusoidal applied voltage at an angular frequency, ω. , The measured impedance, Z , can be described by Z (ω) = Z o cos(φ) + jZ o sin(φ) = Z′ + jZ″ (eq 1), which is derived elsewhere, where j = − 1 is the imaginary unit, ω = 2π f is the angular frequency, f is the frequency, and ϕ is the phase angle shift between the voltage and current. The Nyquist plot is typically used to represent the collected impedance data, where the real component is on the x -axis ( Z′ ) and the negative complex component of the impedance is on the y -axis (−Z″).…”

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

“…It is verified that the Li 3 BO 3 (LBO) and LCO interfaces in the composite cathode are cracked as the cycle evolution occurs, resulting in higher interface resistance and cell degradation. 72 Importantly, adding various equipment in the in situ SEM sample chamber can realize diverse in situ property measurements. For example, coupling a SEM system with mechanical test systems co-located in a large vacuum chamber can help conduct in situ experiments on mechanical properties.…”

“…It is verified that the Li 3 BO 3 (LBO) and LCO interfaces in the composite cathode are cracked as the cycle evolution occurs, resulting in higher interface resistance and cell degradation. 72…”