A Powerful Protocol Based on Anode-Free Cells Combined with Various Analytical Techniques

Abstract

Conspectus Lithium (Li) metal is the ultimate negative electrode due to its high theoretical specific capacity and low negative electrochemical potential. However, the handling of lithium metal imposes safety concerns in transportation and production due to its reactive nature. Recently, anode-free lithium metal batteries (AFLMBs) have drawn much attention because of several of their advantages, including higher energy density, lower cost, and fewer safety concerns during cell production compared to LMBs. Pushing the reversible Coulombic efficiency (CE) of AFLMBs up to 99.98% is key to achieving their 80% capacity retention over more than 1000 cycles. However, interfacial irreversible phenomena such as electrolyte decomposition reactions on both electrodes, dead Li formation, and Li dendrite formation result in poor capacity retention and short circuits in LMBs and AFLMBs. Therefore, it is of great importance and scientific interest to explore those interfacial irreversible phenomena to improve the cell’s cycle life. Although significant contributions toward mitigating electrolyte decomposition, dead lithium, and dendritic lithium formation have been reported at the lithium anode, real irreversible phenomena are usually hidden or difficult to discover due to excess lithium employed in LMBs and simultaneous events taking place in both electrodes or at the interfaces. An integrated protocol is suggested to include Li||Cu, cathode||Li, and cathode||Cu configurations to provide overall quantification and determination of various sources of irreversible Coulombic efficiency (irr-CE) in AFLMBs and LMBs. Combining Li||Cu, cathode||Li, and cathode||Cu configurations is essential for separating the root sources of the capacity loss and irr-CE in LMBs and AFLMBs. Remarkably, integrating an anode-free cell with various analytical techniques can serve as a powerful protocol to decouple and quantify those interfacial irreversible phenomena according to our recent reports. In this Account, we focus on the protocol based on an anode-free cell combined with various analytical methods to investigate interfacial irreversible phenomena. Complementary advanced tools such as transmission X-ray microscopy (visualizing Li plating/stripping mechanism), nuclear magnetic resonance spectroscopy (quantifying dead lithium), and gas chromatography–mass spectroscopy (decoupling interfacial reactions) were employed to extract the intrinsic reasons and sources of individual irreversible reactions in LMBs and AFLMBs. Quantitative evaluation of nucleation and growth of Li metal deposition are addressed, along with solid electrolyte interphase (SEI) fracture, visualization of lithium dendrite growth, decoupling of oxidative and reductive electrolyte decomposition mechanisms, and irreversible efficiency (i.e., dead Li and SEI formation) to reveal the intrinsic causes of individual irr-CE in AFLMBs. Meanwhile, an anode-free protocol can also be utilized as a powerful and multifunctional tool to develop electrolyte formulations or artificial layers fo...

Microscopic Study of Solid–Solid Interfacial Reactions in All-Solid-State Batteries

“…The Coulombic efficiency was the worst in the first cycle, i.e., 61.8%, and the average Coulombic efficiency was 89%, as seen in Figure S2a,b. The reasons for the lower Coulombic efficiency can be various. , To estimate the true efficiency loss from the cathode, i.e., the irreversible Coulombic efficiency (irr-CE), a Li|LPSC|In half cell was then studied (Figure S3). The result showed that the first cycle irr-CE and average irr-CE of Li|LPSC|In were 9.0 and 2.4%, respectively, which could be seen as the efficiency loss attributed to the anode.…”

Intelligent Monitoring for Safety‐Enhanced Lithium‐Ion/Sodium‐Ion Batteries

“…Therefore, it is of great significance to focus on the gas generated inside the battery during battery operation to reveal the deep information of the battery interface reaction and improve the safety of the battery system. [61][62][63][64][65] In recent years, cryo-electron microscopy (Cry-EM) technology can observe the growth of Li/Na dendrites, and X-ray computed tomography and delayed transmission electron microscopy (TL-TEM) can help us visualize the penetration of Li dendrites. However, none of these techniques can predict the insertion and growth chemistry of Li/Na element in early time aiming to achieve the role of safety warning in advance.…”

Mechanistic Study on Artificial Stabilization of Lithium Metal Anode via Thermal Pyrolysis of Ammonium Fluoride in Lithium Metal Batteries

“…10 The solid electrolyte interface (SEI) formation at Li metal anodes is uncontrolled and prone to crack accompanied by volume expansion. 6,10,11 To mitigate parasitic reactions and monitor the lithium flux, a promising strategy of electrolyte additive 12,13 including alloy formation 14 is employed to stabilize deposited lithium. 15−20 The most effective approach is artificially stabilizing the lithium metal anode via gas treatment.…”