Air Stabilization of Li7P3S11 Solid-State Electrolytes through Laser-Based Processing

All-solid-state batteries (ASSBs) that employ solid-state electrolytes (SSEs) have the potential to replace more conventional batteries that employ liquid electrolytes due to their inherent safety, compatibility with lithium metal and reputable ionic conductivity. Li7P3S11 is a promising SSE with reported ionic conductivities in the order of 10 mS/cm. However, its susceptibility to degradation through oxidation and hydrolysis limits its commercial viability. In this work, we demonstrate a laser-based processing method for SSEs to improve humidity stability. It was determined that laser power and scanning speed greatly affect surface morphology, as well as the resulting chemical composition of Li7P3S11 samples. Electrochemical impedance spectroscopy revealed that laser treatment can produce SSEs with higher ionic conductivities than pristine counterparts after air exposure. Further examination of chemical composition revealed an optimal laser processing condition that reduces the rate of P2S74- degradation. This work demonstrates the ability of laser-based processing to be used to improve the stability of SSEs.

Ultra-Thin Lithium Silicide Interlayer for Solid-State Lithium-Metal Batteries

All-solid-state batteries with metallic lithium (Li_BCC ) anode and solid electrolyte (SE) are under active development. However, an unstable SE/Li_BCC interface due to electrochemical and mechanical instabilities hinders their operation. Herein, an ultra-thin nanoporous mixed ionic and electronic conductor (MIEC) interlayer (≈3.25 µm), which regulates Li_BCC deposition and stripping, serving as a 3D scaffold for Li⁰ ad-atom formation, Li_BCC nucleation, and long-range transport of ions and electrons at SE/Li_BCC interface is demonstrated. Consisting of lithium silicide and carbon nanotubes, the MIEC interlayer is thermodynamically stable against Li_BCC and highly lithiophilic. Moreover, its nanopores (<100 nm) confine the deposited Li_BCC to the size regime where Li_BCC exhibits "smaller is much softer" size-dependent plasticity governed by diffusive deformation mechanisms. The Li_BCC thus remains soft enough not to mechanically penetrate SE in contact. Upon further plating, Li_BCC grows in between the current collector and the MIEC interlayer, not directly contacting the SE. As a result, a full-cell having Li_3.75 Si-CNT/Li_BCC foil as an anode and LiNi_0.8 Co_0.1 Mn_0.1 O₂ as a cathode displays a high specific capacity of 207.8 mAh g^-1 , 92.0% initial Coulombic efficiency, 88.9% capacity retention after 200 cycles (Coulombic efficiency reaches 99.9% after tens of cycles), and excellent rate capability (76% at 5 C).

Sn-Substituted Argyrodite Li6PS5Cl Solid Electrolyte for Improving Interfacial and Atmospheric Stability

Sulfide-based solid electrolytes exhibit good formability and superior ionic conductivity. However, these electrolytes can react with atmospheric moisture to generate H₂S gas, resulting in performance degradation. In this study, we attempted to improve the stability of the interface between Li metal and an argyrodite Li₆Ps₅Cl solid electrolyte by partially substituting P with Sn to form an Sn-S bond. The solid electrolyte was synthesized via liquid synthesis instead of the conventional mechanical milling method. X-ray diffraction analyses confirmed that solid electrolytes have an argyrodite structure and peak shift occurs as substitution increases. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses confirmed that the particle size gradually increased, and the components were evenly distributed. Moreover, electrochemical impedance spectroscopy and DC cycling confirmed that the ionic conductivity decreased slightly but that the cycling behavior was stable for about 500 h at X = 0.05. The amount of H₂S gas generated when the solid electrolyte is exposed to moisture was measured using a gas sensor. Stability against atmospheric moisture was improved. In conclusion, liquid-phase synthesis could be applied for the large-scale production of argyrodite-based Li6PS5Cl solid electrolytes. Moreover, Sn substitution improved the electrochemical stability of the solid electrolyte.

Lithium Phosphorus Sulfide Chloride-Polymer Composite via the Solution-Precipitation Process for Improving Stability toward Dendrite Formation of Li-Ion Solid Electrolyte

Improving the mechanical strength of ceramic solid electrolytes such as lithium phosphorus sulfide families for pressure-driven dendrite blocking as well as reducing the electronic conductivity to prevent a dendrite formation inside the electrolytes are very important to extend the lifespan of all-solid-state lithium-metal batteries. Here, we propose a low-temperature solution-precipitation process to prepare polymer-solid electrolyte composites for a highly uniform polymer distribution in the electrolyte to enhance their mechanical strength and reduce their electronic conduction. The composites with up to 12 wt % of polymer are prepared, and the composites exhibit high ionic conductivities of up to 0.3 mS/cm. Furthermore, the electrochemical stability of the electrolyte composites on Li striping/plating cycles is investigated. We confirm that the proposed solution-precipitation process makes the composite much more stable than the bare solid electrolyte and causes them to outperform similar composites from the other existing preparation methods, such as mechanical mixing and solution dispersion.

Grain Boundary Electronic Insulation for High-Performance All-Solid-State Lithium Batteries

Sulfide electrolytes with high ionic conductivities are one of the most highly sought for all-solid-state lithium batteries (ASSLBs). However, the non-negligible electronic conductivities of sulfide electrolytes (≈10^-8  S cm^-1 ) lead to electron smooth transport through the sulfide electrolyte pellets, resulting in Li dendrite directly depositing at the grain boundaries (GBs) and serious self-discharge. Here, a grain-boundary electronic insulation (GBEI) strategy is proposed to block electron transport across the GBs, enabling Li-Li symmetric cells with 30 times longer cycling life and Li-LiCoO₂ full cells with three times lower self-discharging rate than pristine sulfide electrolytes. The Li-LiCoO₂ ASSLBs deliver high capacity retention of 80 % at 650 cycles and stable cycling performance for over 2600 cycles at 0.5 mA cm^-2 . The innovation of the GBEI strategy provides a new direction to pursue high-performance ASSLBs via tailoring the electronic conductivity.

Rational Optimization of Cathode Composites for Sulfide-Based All-Solid-State Batteries

All-solid-state lithium-ion batteries with argyrodite solid electrolytes have been developed to attain high conductivities of 10^-3 S cm^-1 in studies aiming at fast ionic conductivity of electrolytes. However, no matter how high the ionic conductivity of the electrolyte, the design of the cathode composite is often the bottleneck for high performance. Thus, optimization of the composite cathode formulation is of utmost importance. Unfortunately, many reports limit their studies to only a few parameters of the whole electrode formulation. In addition, different measurement setups and testing conditions employed for all-solid-state batteries make a comparison of results from mutually independent studies quite difficult. Therefore, a detailed investigation on different key parameters for preparation of cathodes employed in all-solid-state batteries is presented here. Employing a rational approach for optimization of composite cathodes using solid sulfide electrolytes elucidated the influence of different parameters on the cycling performance. First, powder electrodes made without binders are investigated to optimize several parameters, including the active materials' particle morphology, the nature and amount of the conductive additive, the particle size of the solid electrolyte, as well as the active material-to-solid electrolyte ratio. Finally, cast electrodes are examined to determine the influence of a binder on cycling performance.

Exploiting Nanoscale Complexion in LATP Solid-State Electrolyte via Interfacial Mg2+ Doping

While great effort has been focused on bulk material design for high-performance All Solid-State Batteries (ASSBs), solid-solid interfaces, which typically extend over a nanometer regime, have been identified to severely impact cell performance. Major challenges are Li dendrite penetration along the grain boundary network of the Solid-State Electrolyte (SSE) and reductive decomposition at the electrolyte/electrode interface. A naturally forming nanoscale complexion encapsulating ceramic Li1+xAlxTi2-x(PO4)3 (LATP) SSE grains has been shown to serve as a thin protective layer against such degradation mechanisms. To further exploit this feature, we study the interfacial doping of divalent Mg2+ into LATP grain boundaries. Molecular Dynamics simulations for a realistic atomistic model of the grain boundary reveal Mg2+ to be an eligible dopant candidate as it rarely passes through the complexion and thus does not degrade the bulk electrolyte performance. Tuning the interphase stoichiometry promotes the suppression of reductive degradation mechanisms by lowering the Ti4+ content while simultaneously increasing the local Li+ conductivity. The Mg2+ doping investigated in this work identifies a promising route towards active interfacial engineering at the nanoscale from a computational perspective.

Recent Advancements in Selenium-Based Cathode Materials for Lithium Batteries: A Mini-Review

Selenium (Se)-based cathode materials have garnered considerable interest for lithium-ion batteries due to their numerous advantages, including low cost, high volumetric capacity (3268 mAh cm−3), high density (4.82 g cm−3), ability to be cycled to high voltage (4.2 V) without failure, and environmental friendliness. However, they have low electrical conductivity, low coulombic efficiency, and polyselenide solubility in electrolytes (shuttle effect). These factors have an adverse effect on the electrochemical performance of Li-Se batteries, rendering them unsuitable for real-world use. In this study, we briefly examined numerous approaches to overcoming these obstacles, including selecting an adequate electrolyte, the composition of Se with carbonaceous materials, and the usage of metal selenide base electrodes. Furthermore, we examined the effect of introducing interlayers between the cathode and the separator. Finally, the remaining hurdles and potential study prospects in this expanding field are proposed to inspire further insightful work.

Superionic Solid Electrolyte Li7La3Zr2O12 Synthesis and Thermodynamics for Application in All-Solid-State Lithium-Ion Batteries

Solid-state reaction was used for Li7La3Zr2O12 material synthesis from Li2CO3, La2O3 and ZrO2 powders. Phase investigation of Li7La3Zr2O12 was carried out by x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) methods. The thermodynamic characteristics were investigated by calorimetry measurements. The molar heat capacity (Cp,m), the standard enthalpy of formation from binary compounds (ΔoxHLLZO) and from elements (ΔfHLLZO), entropy (S0298), the Gibbs free energy of the Li7La3Zr2O12 formation (∆f G0298) and the Gibbs free energy of the LLZO reaction with metallic Li (∆rGLLZO/Li) were determined. The corresponding values are Cp,m = 518.135 + 0.599 × T - 8.339 × T-2, (temperature range is 298-800 K), ΔoxHLLZO = -186.4 kJ·mol-1, ΔfHLLZO = -9327.65 ± 7.9 kJ·mol-1, S0298 = 362.3 J·mol-1·K-1, ∆f G0298 = -9435.6 kJ·mol-1, and ∆rGLLZO/Li = 8.2 kJ·mol-1, respectively. Thermodynamic performance shows the possibility of Li7La3Zr2O12 usage in lithium-ion batteries.