Lithium Metal Deposition Research Articles

Structures of Solid‐Electrolyte Interphases and Impacts on Initial‐Stage Lithium Deposition in Pyrrolidinium‐Based Ionic Liquids

The Cover Feature shows the nucleation and growth of initial stage lithium metal deposition beneath solid-electrolyte interphases (SEIs) with different compositions and structures formed in Py14-based ionic liquids containing different ratios of TFSI and FSI anions. Discrepancies in nucleation density and diffusion coefficients and their relationships with overpotentials are investigated in correlation with the SEI structures. More information can be found in the Article by J.-W. He et al.

X-Ray CT Measurement of Lithium Metal Morphological Changes of All-Solid-State Lithium Battery

Global warming, air pollution, and depletion of fossil fuels stimulate the transition of energy sources from conventional fuels to renewable energies. Electric vehicle (EV) with longer cruising range is desired to enhance the utilization of renewable energies in transportation. In order to develop the EV with longer cruising range, it is important to improve the energy density of rechargeable batteries due to the limited space in EV. All solid state battery (ASSB) is expected to realize higher energy density compared to conventional lithium-ion battery because it is able to use a higher voltage cathode and/or lithium metal anode. Hence, ASSB is promising as a power source of the next-generation EV. In order to maximize the energy density of ASSB, active material with a higher capacity is necessary. This instigates the research toward the application of lithium metal anode, which possesses the highest theoretical capacity among anode materials. The key point for realizing lithium metal anode is to secure a good contact between lithium metal anode and solid electrolyte, since the decrease of reaction area would result in the increase of interfacial resistance and the decrease of power output. In other words, lithium metal deposition and dissolution should play important roles on the cell performance through the morphological changes of lithium metal at the interface. Previous research suggested that lithium metal dissolution causes deterioration in the contact [1][2]. On the other hand, the behavior of deposition has not been revealed. In this study, we try to understand the effect of lithium metal morphological behavior during deposition on the cell performance. Here, we develop a nondestructive visualizing method of lithium metal with X-ray and visualization of lithium metal’s morphological changes under dissolution/deposition conditions is conducted. In order to observe the morphological behavior of lithium metal, it is required to distinguish solid electrolyte (SE), lithium metal, and void. However, it is difficult to distinguish void from lithium metal due to the similarity of absorption coefficients between lithium metal and argon used as inert gas. Therefore, in this study, high pressure xenon method is developed. In this method, the X-ray imaging jig (and the void in the cell) is filled with high pressure xenon (8 atm) that has significant difference in absorption coefficient compared to lithium metal, making enough contrast to distinguish lithium metal from void. By using this high pressure xenon method, the distribution of SE, lithium metal, and void (xenon) is successfully visualized. In this study, a cylindrical symmetry cell (lithium metal/SE (LPS-glass)/lithium metal, diameter of 2 mm) is used. The symmetry cell is installed into X-ray imaging jig, sandwiched by stainless-steel current collectors and pressurized to 0.5 MPa with a spring. In order to induce lithium dissolution/deposition, constant current of 0.2 mA/cm2 for 15 hours is supplied to the cell. Before and after the current supply, three dimensional images of the cell are captured by using X-ray CT. Then, these raw images are segmented into SE, lithium metal, and void regions respectively with the intensity of X-ray transmission. Figure 1 shows X-ray CT images of lithium deposition side electrode (a) before the current supply and (b) after the current supply. SE, lithium metal, and void are shown as yellow, white, and transparent respectively. Especially, the contact area of SE and lithium metal is colored by green. Before the current supply, good contact condition is achieved between the SE and lithium metal. However, after current is applied, the contact remains only around the center of the cell. Figure 2 shows the trend of the cell voltage when current is applied. Meanwhile, the voltage gradually increases. It is assumed that the decrease in the contact area between lithium metal and SE during lithium deposition would lead to this increase of voltage.

Electrical Dynamic Switching of Magnetic Plasmon Resonance Based on Selective Lithium Deposition.

Active plasmonic nanostructures have garnered considerable interest in physics, chemistry, and material science due to the dynamically switchable capability of plasmonic responses. Here, the first electrically dynamic control of magnetic plasmon resonance (MPR) through structure transformation by selective deposition of lithium on a metal-insulator-metal (MIM) structure is reported. Distinct optical switching between MPR and surface plasmon polariton (SPP) excitations can be enabled by applying a proper electrical current to the electrochemical cell. Furthermore, the structure transformation through lithium metal deposition indicates the reconfigurable MPR excitation in a full cycling of the charging and discharging process. The results may shed light on electrically compatible self-powered active plasmonics as well as nondestructive optical sensing for electrochemical evolution.

High-energy lithium batteries based on single-ion conducting polymer electrolytes and Li[Ni0.8Co0.1Mn0.1]O2 cathodes

Abstract Single-ion conducting polymer electrolytes are considered ideal for suppressing dendritic lithium deposition, but so far suffered instability at elevated potentials and, thus, incompatibility with next-generation high-energy cathodes such as Ni-rich Li[Ni1-x-yCoxMny]O2 (NCM(1-x-y)xy). Herein, we show that the thoughtful design of electrolytes based on multi-block co-poly(arylene ether sulfone)s and incorporating suitable “molecular transporters” (such as propylene carbonate) may, in fact, enable the realization of high-energy lithium-metal batteries employing, for the first time, NCM811-based positive electrodes. These batteries can be cycled with high reversible capacity at various temperatures, including 20 °C and even 0 °C, for more than 500 cycles without substantial capacity fading when applying an optimized charging mode. The careful electrochemical characterization and ex situ investigation of the electrode/electrolyte interfaces reveals, moreover, that the use of such single-ion conductor successfully inhibits dendritic lithium metal deposition, while particular care has to be taken for the interface between the electrolyte and the NCM811 cathode.

Effect of Pressure on Lithium Metal Deposition and Stripping against Sulfide-Based Solid Electrolytes.

Fundamental challenges for lithium metal anode cycling against solid electrolytes (SEs) at high current densities and high areal capacities include lithium dendrite penetration during Li deposition and void formation during Li stripping. These two dynamic processes have a distinct dependency on the external pressure. The majority of research to date on Li cycling behaviors adopt symmetric cell (Li/SE/Li) configurations, where the stack pressure and the failure associated with the deposition and the stripping processes cannot be delineated. In this work, we investigate the effect of external pressure on the deposition and the stripping of Li metal anodes separately against a sulfide-based SE by employing asymmetric cell configurations. We show that (1) for Li striping, the pressure required is positively correlated with stripping current densities; (2) for Li deposition, higher pressure leads to lower maximum allowed current densities, defined as the current densities beyond which dendrite penetration occurs. The apparent opposing requirement for external pressure of Li deposition and Li stripping elucidates why the methodology of Li metal cycling in symmetric cell configurations is fundamentally flawed and highlights the importance of refined pressure regulation in all-solid-state Li metal batteries.

Effect of high concentration of polysulfides on Li stripping and deposition

The direct reaction of polysulfide species with the Li metal anode causes several issues in the performance of lithium-sulfur batteries, from poor capacity utilization and fast capacity fade to poor Coulombic efficiency. Nevertheless, several reports indicate formation of favorable lithium SEI when allowing for its contact with polysulfides. With cycling tests, impedance spectroscopy measurements and morphology investigation, we have confirmed the beneficial effect of polysulfides on lithium metal stripping and deposition even without LiNO3, which is usually added. Most importantly, highly concentrated catholytes, which are closer to the saturated solutions encountered in lean electrolyte-to-sulfur ratios, were tested. In the 1 M Li2S8 catholyte solution, its effect produced Li electrodes without dendritic growth, but rather a wrinkled surface. To circumvent the issue of viscosity in such solutions, pre-treatment in polysulfide solutions was also tested. The performance of such electrodes showed an increase in cycle life and lower overpotentials, although dendritic growth could not be fully avoided. In order to better understand the effect of pre-treatment on transport/reaction mechanism in Li electrode, a detailed analysis of selected impedance spectra is carried out using physics-based transmission line modelling (TLM).

High-performance all-solid-state polymer electrolyte with fast conductivity pathway formed by hierarchical structure polyamide 6 nanofiber for lithium metal battery

Abstract The utilization of all-solid-state electrolytes is considered to be an effective way to enhance the safety performance of lithium metal batteries. However, the low ionic conductivity and poor interface compatibility greatly restrict the development of all-solid-state battery. In this study, a composite electrolyte combining the electrospun polyamide 6 (PA6) nanofiber membrane with hierarchical structure and the polyethylene oxide (PEO) polymer is investigated. The introduction of PA6 nanofiber membrane can effectively reduce the crystallinity of the polymer, so that the ionic conductivity of the electrolyte can be enhanced. Moreover, it is found that the presence of finely branched fibers in the hierarchical structure PA6 membrane allows the polar functional groups (C=O and N−H bonds) to be fully exposed, which provides sufficient functional sites for lithium ion transport and helps to regulate the uniform deposition of lithium metal. Moreover, the hierarchical structure can enhance the mechanical strength (9.2 MPa) of the electrolyte, thereby effectively improving the safety and cycle stability of the battery. The prepared Li/Li symmetric battery can be stably cycled for 1500 h under 0.3 mA cm−2 and 60 °C. This study demonstrates that the prepared electrolyte has excellent application prospects in the next generation all-solid-state lithium metal batteries.

Selective NMR observation of the SEI\u2013metal interface by dynamic nuclear polarisation from lithium metal

While lithium metal represents the ultimate high-energy-density battery anode material, its use is limited by dendrite formation and associated safety risks, motivating studies of the solid–electrolyte interphase layer that forms on the lithium, which is key in controlling lithium metal deposition. Dynamic nuclear polarisation enhanced NMR can provide important structural information; however, typical exogenous dynamic nuclear polarisation experiments, in which organic radicals are added to the sample, require cryogenic sample cooling and are not selective for the interface between the metal and the solid–electrolyte interphase. Here we instead exploit the conduction electrons of lithium metal to achieve an order of magnitude hyperpolarisation at room temperature. We enhance the 7Li, 1H and 19F NMR spectra of solid–electrolyte interphase species selectively, revealing their chemical nature and spatial distribution. These experiments pave the way for more ambitious room temperature in situ dynamic nuclear polarisation studies of batteries and the selective enhancement of metal–solid interfaces in a wider range of systems.

Observation of Lithium Dendrite Growth on Llzo-PEO Solid Electrolyte

Solid-state electrolytes have been discovered as an alternative to liquid electrolyte on lithium-based batteries. Among all solid electrolytes, poly (ethylene oxide) based-solid electrolytes (PEO) have the advantages of low flammability, good flexibility, and excellent thermal stability. The major problem limiting the rate capability of PEO-based electrolyte in the lithium metal battery during charging is the issue of lithium penetration through the PEO electrolyte that results in short circuits 1. To overcome these drawbacks, we have added the ceramic fillers (i.e., garnet (Li7La3Zr2O12) etc.) in a ratio of 10-40% in the polymer host matrix. The garnet ceramic filler contributes to reduce the crystallinity of polymer and so to increase the ionic conductivity. The ceramic in polymer also provides higher mechanical strength that can reduce the lithium dendrite formation 2. To investigate the formation of lithium dendrite, we show a detailed study of lithium metal deposition on the LLZO-PEO electrolyte using ex-situ electrochemical and electron microscopic methods. Keywords: Solid-state lithium batteries, Solid polymer electrolyte, Garnet, Polymer-ceramic composite electrolyte, Lithium dendrite REFERENCES 1. J. Mindemark, M. J. Lacey, T. Bowden and D. Brandell, Progress in Polymer Science, 2018, 81, 114-143.2. W. Zhang, J. Nie, F. Li, Z. L. Wang and C. Sun, Nano Energy, 2018, 45, 413-419. Figure 1

Transient Voltammetry with Ultramicroelectrodes Reveals the Electron Transfer Kinetics of Lithium Metal Anodes

Fully understanding the mechanism of lithium metal deposition is critical for the development of rechargeable lithium battery anodes. The heterogeneous electron transfer kinetics are an important a...

Graphene-Like Graphite Negative Electrode Rapidly Chargeable at Constant Voltage

The present paper describes the excellent input performance of graphene-like graphite (GLG) as a negative electrode material for the lithium ion batteries (LIBs), which should allow a new rapid charging method. We find that the GLG electrode can be fully charged only within several minutes by the constant voltage mode, i.e., without resorting to the constant current mode, during which the maximum current reaches as high as ca. 80 A g−1. No evidence is observed for the lithium metal deposition on the GLG electrode, despite the rapid charging at the voltage below the lithium deposition potential. These characteristics have never been achieved by graphite, currently used as the negative electrode material in LIBs. The GLG-based negative electrode should not only provide a safe and rapid charging method but also facilitate the battery control of LIBs.

Anode Overpotential Control via Interfacial Modification: Inhibition of Lithium Plating on Graphite Anodes.

Lithium-metal deposition on graphite anodes limits the cycle life and negatively impacts safety of the current state of the art Li-ion batteries. Herein, deliberate interfacial modification of graphite electrodes via direct current (DC) magnetron sputtering of nanoscale layers of Cu and Ni is employed to increase the overpotential for Li deposition and suppress Li plating under high rate charge conditions. Due to their nanoscale, the deposited surface films have minimal impact (∼0.16% decrease) on cell level theoretical energy density. Interfacial properties of the anodes are thoroughly characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and spatially resolved mapping X-ray absorption near edge structure (XANES) spectroscopy. The spectroscopic measurements indicate that the Cu and Ni coatings form oxide upon exposure to an ambient environment, but they are reduced within the electrochemical cell and remain in a metallic state. Li plating is quantified by X-ray diffraction and associated electrochemistry measurements revealing that the surface treatment effectively reduces the quantity of the plated Li metal by ∼50% compared to untreated electrodes. These results establish an effective method using interfacial modification to achieve deliberate control of Li-metal deposition overpotential and reduction of lithium plating on graphite.

Seed-Free Selective Deposition of Lithium Metal into Tough Graphene Framework for Stable Lithium Metal Anode.

Graphene has been wildly used as a host to suppress dendrite growth to stabilize the lithium metal anode. However, the high overpotential of lithium deposition on pure graphene has to be lowered by doping or employing precious metals. Additionally, the soft nature of graphene rendered itself to aggregate, consequently squeezing room for lithium accommodation. Herein, a tough graphene framework composed of 3D periodic hollow spheres was reported as a free-standing host to stabilize lithium metal anodes. The prepared 3D periodic hollow structure not merely reinforces the framework to maintain hollow structure under pressure caused by assembling battery, but also lowers the overpotential without the help of dopant or precious metals. It is worthy to note that high efficiency of ion diffusion, thanks to the channels interconnecting hollow spheres by holes on the walls, benefits both suppression of lithium dendrite and rate capability. The properties of low density and high mechanical strength make graphene frameworks electrode a promising lightweight Li host material, which reveals a new avenue for designing high-energy density electrode materials.

A scalable bio-inspired polydopamine-Cu ion interfacial layer for high-performance lithium metal anode

The growth of Li dendrites and the instability of the solid electrolyte interphase (SEI) layer during plating/stripping has hindered the practical application of high-energy-density batteries based on a lithium metal anode. Building a stable interfacial layer is effective in preventing lithium corrosion by the electrolyte and controlling the deposition of lithium metal. Here, we present a robust polydopamine-Cu ion (PDA-Cu2+) coating layer formed by the aggregation of nanoparticles and Cu ions, which can be obtained by a subtle immersion strategy. We demonstrate that the PDA-Cu2+ protective layer, with a unique structure comprising nanoparticles, can regulate and guide Li metal deposition, and together with Cu ions, forms a lubricating surface to facilitate uniform Li ion diffusion and induce stable SEI layer formation. Li anodes with this PDA-Cu2+ layer modification ultimately achieve higher Coulombic efficiencies, which are consistently stable for over 650 cycles at 0.5 mA·cm−2 without Li dendrites. The introduced PDA-Cu2+ coating can adhere to any material of any shape; additionally, the operation can be realized on a large scale because of its simplicity. These merits provide a promising approach for developing stable and safe lithium metal batteries.

(Invited) Acoustic Detection of Unwanted Lithium Deposition in Lithium Ion Batteries

The ability to quickly charge lithium ion batteries at rates comparable to petrol refueling may be an accelerant for the adoption of EVs. In cells of sufficient energy density for EV applications rates faster than 3C can lead to the unwanted deposition of lithium metal on the anode, which at best puts the cell into an indeterminate state. In this work we explore the applicability of electrochemical acoustic signal interrogation for detecting and measuring the deposition of lithium metal within lithium ion cells. Initial experiments indicate sufficiently sensitive detection lithium plating such that BMS protocols may be developed to reverse early stage deposition.

Assessing Safety Properties of Lithium Metal Batteries

Currently, the so-called all-solid-state battery (ASSB) is getting enormous attention in academia and industry as a potential next-generation battery technology replacing the state-of-the-art lithium ion battery (LIB) based on a liquid electrolyte. Especially the high energy density (Wh/L) and specific energy (Wh/kg) are appealing [1] with regard to the application in electric vehicles and protable devices. However, the breakthrough of the ASSB technology is hindered by practical challenges in terms of processing, rate capability and cycle life. [2] Apart from high energy densities and a long cycle life, significantly enhanced safety properties are considered key for future battery technologies. Therein, the ASSB benefits from the absence of flammable liquid electrolyte as present in state-of-the-art LIBs. However, only very few studies were published showing the evaluation of the safety properties of lithium metal batteries. [3, 4] Therefore, this study aims on giving first insights into the factors influencing the thermal stability, hence the safety properties of different lithium metal battery (LMB) setups. As a baseline, lithium metal batteries based on liquid electrolyte were investigated in order to understand the influence of the lithium metal deposition behavior on the thermal stability of LMBs. Therein, during charging, lithium metal does not deposit homogeneously but forms dendritic or mossy structures often referred to as high surface area lithium (HSAL). [1, 5] At elevated temperatures, the high reactivity of HSAL can lead to fatal consequences, especailly in presence of liquid electrolyte (e.g. fire, explosion). Thus, the controlled deposition of lithium metal is crucial in order to guarantee safe operation of lithium metal batteries. This can be achieved by either modifying the charging process or the lithium metal surface (mechanically/chemically). Beyond that, lithium metal batteries based on either ceramic or polymer-based electrolytes are investigated. Therein, the cells are cycled to different sates of charge (SOC) and/or states of health (SOH) before analyzing the thermal stability by differential scanning calorimetry (DSC). This way, it is possible to determine distinct differences in the onset temperature for exothermic reactions and the evolving heat as a measure for the intensity of the reactions that might lead to a thermal runaway in large-scale cells. Moreover, the thermal stability of the cell components are characterized individually and in presence of each other du deduce interdependencies considering the chemical and thermal stability. In combination with comprehensive post-mortem analysis, it is possible to determine the factors influencing the thermal stability most. In summary, this study presents first results on the thermal stability of various LMB types to unravel the advantages/disadvantages compared to LIBs. [1] T. Placke, et al., J Solid State Electrochem 2017, 21, 1939-1964. [2] K. Kerman, et al., J Electrochem Soc 2017, 164, A1731-A1744. [3] T. Inoue, et al., ACS Appl Mater Interfaces 2017, 9, 1507-1515. [4] Uyama, et al., ACS Appl Energy Mater 2018, 1, 5712-5717. [5] M. Winter, et al., Adv Mater 1998, 10, 725-763.

Generating Enhanced Interfaces between Micro-Patterned Lithium Electrodes and Solid Polymer Electrolytes

Lithium is a very promising anode material for the next generation of rechargeable batteries. The research on such battery systems is motivated especially by the high theoretical specific capacity (3860 mAh/g) and the low density (0.53 g/cm³), which qualifies lithium particularly also for portable devices. Furthermore, this metal features the lowest negative electrode potential (-3.04 V vs. SHE), which enables a high cell voltage and high specific energy, respectively.[1-2] Nevertheless, there are also some challenges, like the inhomogeneous deposition of lithium metal during cycling leading to high surface area lithium (HSAL). Such deposits can be dendritic or needle-like and can easily penetrate the separator inducing short circuits and local heating, which in the end can lead to fires or even explosions.[1-3] To counteract the safety issue of HSAL, many different approaches were studied which should lead to a more homogeneous deposition of lithium.[4-7] One of them are solid polymer electrolytes (SPEs). They have the benefits to be very thermally and electrochemically stable, their exothermal decomposition kinetics are slow and they generate a flexible and dense barrier between the electrodes. Furthermore, the less volatility of the components of SPEs leads to a lower risk of explosion and toxication, which represent disadvantages of liquid organic electrolytes.[3-5] Another approach is the mechanical modification of lithium electrodes with micro patterning to increase the electrode surface, which leads to a lower current density resulting in a reduced formation of HSAL. Moreover, HSAL shows the tendency to deposit first at the walls of the defects before it later on grows on the remaining surface. For this reason, the dendritic growth towards the counter electrode is delayed and thereby the risk of short circuits is decreased.[2, 6-7] In this work, the focus lies on the combination of these two approaches. Herein, we will present a new way to combine SPEs with modified lithium electrodes by an advanced coating method. The wetting of the micro patterned lithium surface by the SPE and the directed lithium deposition in the defects are verified by SEM analysis and the electrochemical properties are investigated on the basis of constant current cycling and impedance experiments. [1] K. Zhang, et al., Adv. Energy Mater. 2016, 6, 1600811. [2] P. Schmitz, et al., Phys. Chem. Chem. Phys. 2017, 19, 19178-19187. [3] M. Joost, et al., Electrochim. Acta, 2013, 113, 181-185. [4] Q. Pan, et al., Adv. Mater. 2015, 27, 5995-6001. [5] J. Paulsdorf, et al., Solid State Ion . 2002, 169, 25-33. [6] M.-H. Ryou, et al., Adv. Funct. Mater. 2015, 25, 834-841. [7] J. Park, et al., Adv. Mater. Interfaces 2016, 3, 1600140.

Artificial solid electrolyte interphase based on polyacrylonitrile for homogenous and dendrite-free deposition of lithium metal**Project supported by the National Natural Science Foundation of China (Grant Nos. 51822211 and 51802342) and the State Grid Technology Project, China (Grant No. DG71-17-010).

High chemical reactivity, large volume changes, and uncontrollable lithium dendrite growth have always been the key problems of lithium metal anodes. Coating has been demonstrated as an effective strategy to protect the lithium metal. In this work, the effects of polyacrylonitrile (PAN)-based coatings on electrodeposited lithium have been studied. Our results show that a PAN coating layer provides uniform and dendrite-free lithium deposition as well as better cycling performance with carbonate electrolyte. Notably, heat treatment of the PAN coating layer promotes the formation of larger deposit particle size and higher coulombic efficiency (85%). The compact coating layer of heat-treated PAN with a large Young modulus (82.7 GPa) may provide stable protection for the active lithium. Improved homogeneity of morphology and mechanical properties of heat-treated PAN contribute to the larger deposit particles. This work provides new feasibility to optimize the polymer coating through rational modification of polymers.

Polydopamine Coating Layer Modified Current Collector for Dendrite-Free Li Metal Anode

Lithium metal is considered to be the most promising anode material due to its high theoretical capacity, low density and low electrochemical potential. However, continuous lithium dendrite growth results in low coulombic efficiency, capacity decay and safety hazard, which hinder the practical application of lithium metal anode. In this work, a functional polydopamine (PDA) layer inspired by nature is introduced to the surface of Cu foil, which is used as a current collector for lithium metal anode here. During depositing of lithium, lithium ions will firstly react with the hydroxyl groups of PDA layer, yielding uniformly distributed lithium complexing carbonyl groups which can work as nucleation sites and is favorable for uniform and stable deposition of lithium metal on the current collector, thus effectively suppress dendrite formation and growth. As a result, lithium metal batteries with PDA modified current collectors exhibit high coulombic efficiency of above 97% for 100 cycles at 0.5 mA cm-2 and the Li/Li symmetric cells show more than 800 h stable repeated lithium plating and stripping. The LiFePO4/Li batteries with the modified current collectors show extended cycle life (more than 150 cycles). This work provides a novel way to address the problems of lithium metal anode.

Insights into the Safety Properties of Lithium Metal Batteries

With regard to current trends, the so-called all-solid-state battery (ASSB) is getting enormous attention in academia and industry as a potential next-generation battery technology replacing the state-of-the-art lithium ion battery (LIB). Especially the high energy density (Wh/L) and specific energy (Wh/kg) are appealing properties of the ASSB [1] potentially enabling longer driving ranges for electric vehicles compared to the state-of-the-art lithium ion technology. However, the breakthrough of the ASSB technology is facing practical challenges in terms of processing, rate capability and cycle life. [2] In addition to high energy densities and a long cycle life, significantly enhanced safety properties are considered key for future battery technologies. Regarding the latter, the ASSB benefits from the absence of flammable liquid electrolyte compared to LIBs. However, only very few studies were published showing the evaluation of the safety properties of lithium metal batteries. [3] Therefore, this study aims on giving first insights into the factors influencing the thermal stability, hence the safety properties of different lithium metal battery setups. As a starting point, lithium metal batteries based on liquid electrolyte were investigated in order to understand the influence of the lithium metal deposition behavior on the thermal stability of the cell. Therein, it has to be considered that during charging lithium metal does not deposit homogeneously but forms dendritic or mossy structures often referred to as high surface area lithium (HSAL). [1, 4] At elevated temperatures, the high reactivity of HSAL in presence of liquid electrolyte can lead to fatal consequences (e.g. fire, explosion). Thus, the controlled deposition of lithium metal is crucial in order to guarantee safe operation of lithium metal batteries. This can be achieved by either modifying the charging process or the lithium metal surface (mechanically/chemically). Beyond that, lithium metal batteries based on either ceramic or polymer-based electrolytes are investigated. Therein, the cells are cycled to different sates of charge (SOC) and/or states of health (SOH) before analyzing the thermal stability by differential scanning calorimetry (DSC). This way, it is possible to determine distinct differences in the onset temperature for exothermic reactions and the evolving heat as a measure for the intensity of the reactions that might lead to a thermal runaway in large-scale cells. Moreover, the thermal stability of the cell components are characterized individually and in presence of each other. In combination with comprehensive post-mortem analysis, it is possible to determine the factors influencing the thermal stability most. In summary, this study presents first results on the thermal stability of various lithium metal battery types to unravel the advantages/disadvantages compared to LIBs. The authors acknowledge the BMBF for funding the project “BCT” (03XP019I). [1] T. Placke, et al., J Solid State Electrochem 2017, 21, 1939-1964. [2] K. Kerman, et al., J Electrochem Soc 2017, 164, A1731-A1744. [3] T. Inoue, et al., ACS Appl Mater Interfaces 2017, 9, 1507-1515. [4] M. Winter, et al., Adv Mater 1998, 10, 725-763.