enable the lithium metal anode with high rate capability. [1][2][3][4] While in LIBs with liquid electrolytes, lithium dendrite growth and low Coulombic efficiency prevent the use of lithium metal as an anode material, [3,[5][6][7][8][9][10][11] solid electrolytes (SEs) had been predicted to be able to block dendrite growth due to their high shear modulus. [12,13] In this context, Li 7 La 3 Zr 2 O 12 (LLZO) type garnet SEs [14] have attracted great attention as they combine high ionic conductivity with sufficient electrochemical stability against lithium metal, which prevents fast degradation and growth of a resistive interphase. [15,16] Nevertheless, certain issues at the lithium|solid electrolyte interface remain unsolved. [17,18] Lithium penetration through garnet-type SEs currently limits the possible charge rates. [19][20][21][22][23] In this context, it was found that good contact to a small reservoir of lithium metal is highly beneficial to prevent inhomogeneous lithium nucleation, which then reduces the lithium penetration susceptibility. [24] All previous results underline the need for sufficient and homogeneous contact between metal and SE during battery operation. Thus, it is of upmost importance for lithium metal solid-state battery development to prevent pore formation and growth at the anode interface during battery discharge. [24][25][26] Indeed, while the intrinsic charge transfer kinetics of the lithium|LLZO interface was found to be sufficiently fast for practical applications (R int < 2 Ωcm²), [26,27] recent work shows that the morphological instability of the (pure) lithium metal anode on solid electrolytes under anodic load is an inherent, fundamental problem that needs to be solved for battery designs that do not allow high operation pressures in the MPa range. [26,28] The morphological instability stems from the vacancy injection into lithium metal during anodic dissolution, which is a general phenomenon of parent metal electrodes. [29,30] It leads to contact loss and unwanted local current constriction during cell discharge. Therefore, transport of lithium in the lithium metal anode itself needs to be better understood and tuned to further increase the rate capability of cells with a lithium metal anode (i.e., to per-cycle areal capacities of 5 mAh cm −2 at current densities ranging to 10 mA cm −2 ). [31] However, the currently run, predominantly short-term lithium shuttling experiments onThe morphological instability of the lithium metal anode is the key factor restricting the rate capability of lithium metal solid state batteries. During lithium stripping, pore formation takes place at the interface due to the slow diffusion kinetics of vacancies in the lithium metal. The resulting current focusing increases the internal cell resistance and promotes fast lithium penetration. In this work, galvanostatic electrochemical impedance spectroscopy is used to investigate operando the morphological changes at the interface by analysis of the interface capacitances. Therewith, the effect of temper...

Solid‐state lithium‐sulfur batteries (SSLSBs) have the potential to cause a paradigm shift in energy storage. The use of emerging highly‐conductive solid electrolytes enables high energy and power densities. However, the need for an intimate mixture of electrolyte and conductive additives to compensate for the insulating nature of cathode active materials S8 and Li2S induces intense electrolyte degradation. Thus, it is paramount to understand better the electrochemical and transport properties of the cathode composite with extremely high interface density among cathode components. Here, by utilizing a ball‐milled composite of the lithium argyrodite Li6PS5Cl and carbon as a model electrode, the stability, reversibility, and transport in the composite as functions of cathode loading, the volume fraction of conducting phase, temperature, and applied potentials are comprehensively investigated. Comparing the onset potentials of electrolyte degradation and the sharp drop in the effective ionic conductivity of the composite determined through transmission‐line model analysis, successful enhancement of the capacity retention of SSLSBs is demonstrated by balancing between the attainable capacity and effective carrier transport, achieving a high areal capacity of 3.68 mAh cm−2 after 100 cycles at room temperature. The here‐observed analysis is applicable to any solid‐state composite with electrically insulating active materials.

potentials in all-solid-state Li-S batteries. ChemRxiv. Preprint.Owing to a remarkably high theoretical energy density, the lithium-sulfur (Li-S) battery has attracted significant attention as a candidate for next-generation batteries. While employing solid electrolytes can provide a new avenue for high capacity Li-S cells, all-solid-state batteries have unique failure mechanisms such as chemo-mechanical failure due to the volume changes of active materials. In this study, we investigate all-solid-state Li-S model cells with differently processed cathode composites and elucidate a typical failure mechanism stemming from irreversible Li 2 S formation in the cathode composites. Reducing the particle size is key to minimizing the influence of volume changes and a capacity of over 1000 mAh g sulfur -1 is achieved by ball-milling of the cathode composites. In addition, the long-term stability of the ball-milled cathode is investigated by varying upper and lower cut-off potentials for cycling, which results in unveiling the significantly detrimental role of the lower cut-off potential. Preventing a deep-discharge leads to a reversible capacity of 800 mAh g sulfur -1 over 50 cycles in the optimized cell. This work highlights the importance of mitigating chemo-mechanical failure using microstructural engineering as well as the influence of the cut-off potentials in all-solid-state Li-S batteries. File list (2)download file view on ChemRxiv revised manuscript.pdf (3.56 MiB) download file view on ChemRxiv Supporting Information.pdf (3.38 MiB)

Halide‐based solid electrolytes are currently growing in interest in solid‐state batteries due to their high electrochemical stability window compared to sulfide electrolytes. However, often a bilayer separator of a sulfide and a halide is used and it is unclear why such setup is necessary, besides the instability of the halides against lithium metal. It is shown that an electrolyte bilayer improves the capacity retention as it suppresses interfacial resistance growth monitored by impedance spectroscopy. By using in‐depth analytical characterization of buried interphases by time‐of‐flight secondary ion mass spectrometry and focused ion beam scanning electron microscopy analyses, an indium‐sulfide rich region is detected at the halide and sulfide contact area, visualizing the chemical incompatibility of these two electrolytes. The results highlight the need to consider more than just the electrochemical stability of electrolyte materials, showing that chemical compatibility of all components may be paramount when using halide‐based solid electrolytes in solid‐state batteries.

<p>Owing to a remarkably high theoretical energy density, the lithium-sulfur (Li-S) battery has attracted significant attention as a candidate for next-generation batteries. While employing solid electrolytes can provide a new avenue for high capacity Li-S cells, all-solid-state batteries have unique failure mechanisms such as chemo-mechanical failure due to the volume changes of active materials. In this study, we investigate all-solid-state Li-S model cells with differently processed cathode composites and elucidate a typical failure mechanism stemming from irreversible Li₂S formation in the cathode composites. Reducing the particle size is key to minimizing the influence of volume changes and a capacity of over 1000 mAh g_sulfur^-1is achieved by ball-milling of the cathode composites. In addition, the long-term stability of the ball-milled cathode is investigated by varying upper and lower cut-off potentials for cycling, which results in unveiling the significantly detrimental role of the lower cut-off potential. Preventing a deep-discharge leads to a reversible capacity of 800 mAh g_sulfur^-1over 50 cycles in the optimized cell. This work highlights the importance of mitigating chemo-mechanical failure using microstructural engineering as well as the influence of the cut-off potentials in all-solid-state Li-S batteries. </p>

Solid‐state batteries have the potential to outperform conventional lithium‐ion batteries, as they offer higher energy densities, necessary for the increasing demand for portable energy storage. Silicon‐graphite composites are considered to be one of the most promising alternatives to the lithium metal anode due to their low lithiation potential and resistance against dendrite formation. Since these composites show insufficient ionic conductivity, a fast‐conducting solid electrolyte is needed to facilitate the charge carrier transport. Optimizing the volume fractions of the solid electrolyte is crucial to ensure sufficient charge carrier transport and achieve the optimal performance. In this work, the influence of the charge carrier transport in a silicon on graphite (Si/C)/argyrodite solid electrolyte composite on the electrochemical performance is studied. By systematically varying the ratio of the Si/C to solid electrolyte, it was found that the effective ionic conductivity of the electrode composite improves exponentially with increasing content of the solid electrolyte, which in turn leads to an increase in the specific capacity of the composite across all C‐rates. This study highlights the importance of understanding and customizing charge carrier transport properties in solid‐state anode composites to achieve optimum electrochemical performance.

<p>Owing to a remarkably high theoretical energy density, the lithium-sulfur (Li-S) battery has attracted significant attention as a candidate for next-generation batteries. While employing solid electrolytes can provide a new avenue for high capacity Li-S cells, all-solid-state batteries have unique failure mechanisms such as chemo-mechanical failure due to the volume changes of active materials. In this study, we investigate all-solid-state Li-S model cells with differently processed cathode composites and elucidate a typical failure mechanism stemming from irreversible Li₂S formation in the cathode composites. Reducing the particle size is key to minimizing the influence of volume changes and a capacity of over 1000 mAh g_sulfur^-1is achieved by ball-milling of the cathode composites. In addition, the long-term stability of the ball-milled cathode is investigated by varying upper and lower cut-off potentials for cycling, which results in unveiling the significantly detrimental role of the lower cut-off potential. Preventing a deep-discharge leads to a reversible capacity of 800 mAh g_sulfur^-1over 50 cycles in the optimized cell. This work highlights the importance of mitigating chemo-mechanical failure using microstructural engineering as well as the influence of the cut-off potentials in all-solid-state Li-S batteries. </p>

Over the last decades, we have seen an increase in the number of new materials that can be incorporated into all-solid-state batteries (ASSBs). Halide solid electrolytes have attracted significant attention due to their superior stability against oxide-based cathode active materials when compared to sulfide-based solid electrolytes. Nonetheless, the dynamicity of interparticle contact during cycling in ASSBs hinders their stability and performance. Therefore, inactive materials such as electronically conductive additives and polymer binders are needed to compensate the contact-loss reducing the energy density of the resulting cells. Here, we present an aqueous approach for the preparation of halide solid electrolyte-conductive polymer hybrid composites with Li3InCl6 and poly(3,4-ethylendioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) in one-pot. The resulting composites combine the properties of a solid electrolyte with a conductive additive and a binder together with into a single hybrid material. Together with other analytical techniques, Kelvin Probe Force Microscopy (KPFM) imaging showed a successful synthesis of the hybrid materials and revealed that the conductive polymer (CP), namely PEDOT:PSS, is located at the surface/grain of the Li3InCl6. Upon incorporation of such composites in sulfide solid-state half-cells with lithium nickel manganese cobalt oxide (NMC) cathode active material (CAM) we observe an increase in the partial electronic transport of the catholytes with increasing CP content, which correlates an increase in the initial discharge capacities. This study sets the stage to explore the preparation of multi-functional catholytes without the necessity of organic solvents, extremely high temperatures or special environments.