Quantitative Analysis of Sodium Metal Deposition and Interphase in Na Metal Batteries

Sodium-ion batteries exhibit significant promise as a viable alternative to current lithium-ion technologies owing to their sustainability, low cost per energy density, reliability, and safety. Despite recent advancements in cathode materials for this category of energy storage systems, the primary challenge in realizing practical applications of sodium-ion systems is the absence of an anode system with high energy density and durability. Although Na metal is the ultimate anode that can facilitate high-energy sodium-ion batteries, its use remains limited due to safety concerns and the high-capacity loss associated with the high reactivity of Na metal. In this study, titration gas chromatography is employed to accurately quantify the sodium inventory loss in ether- and carbonate-based electrolytes. Uniaxial pressure is developed as a powerful tool to control the deposition of sodium metal with dense morphology, thereby enabling high initial coulombic efficiencies. In ether-based electrolytes, the Na metal surface exhibits the presence of a uniform solid electrolyte interphase layer, primarily characterized by favorable inorganic chemical components with close-packed structures. The full cell, utilizing a controlled electroplated sodium metal in ether-based electrolyte, provides capacity retention of 91.84% after 500 cycles at 2C current rate and delivers 86 mAh/g discharge capacity at 45C current rate, suggesting the potential to enable Na metal in the next generation of sodium-ion technologies with specifications close to practical requirements

A Facile, Dry-Processed Lithium Borate-Based Cathode Coating for Improved All-Solid-State Battery Performance

Sulfide-based solid electrolytes are known to have narrow electrochemical windows which limit their practical use in all-solid-state batteries (ASSBs). Specifically, when paired with a high-voltage transition metal oxide (TMO) cathode, the electrolyte will typically undergo unwanted degradation via chemical reactions or electrochemical oxidation, especially upon charging to voltages beyond the electrochemical stability window of the electrolyte. To mitigate these undesired reactions, thin (<10 nm), conformal, ionically-conducting, and electronically-insulating oxide-based protective coating layers have been applied on the cathode, typically via a solution process. In this work, a lithium borate-based (LBO) coating, prepared instead with a dry coating process, was shown to have the same beneficial properties. As evidenced by electrochemical characterization, the developed LBO coating shows good cycling performance and even performs better than the LiNbO3 coating commonly used in the literature. This new solvent-free coating method can thus be used to fabricate longer-lasting ASSBs

A Facile, Dry-Processed Lithium Borate-Based Cathode Coating for Improved All-Solid-State Battery Performance

Sulfide-based solid electrolytes are known to have narrow electrochemical windows which limit their practical use in all-solid-state batteries (ASSBs). Specifically, when paired with a high-voltage transition metal oxide (TMO) cathode, the electrolyte will typically undergo unwanted degradation via chemical reactions or electrochemical oxidation, especially upon charging to voltages beyond the electrochemical stability window of the electrolyte. To mitigate these undesired reactions, thin (<10 nm), conformal, ionically-conducting, and electronically-insulating oxide-based protective coating layers have been applied on the cathode, typically via a solution process. In this work, a lithium borate-based (LBO) coating, prepared instead with a dry coating process, was shown to have the same beneficial properties. As evidenced by electrochemical characterization, the developed LBO coating shows good cycling performance and even performs better than the LiNbO3 coating commonly used in the literature. This new solvent-free coating method can thus be used to fabricate longer-lasting ASSBs

Fabrication of High-Quality Thin Solid-State Electrolyte Films Assisted by Machine Learning

International audienceSolid-state electrolytes (SSEs) are promising candidates to circumvent flammability concerns of liquid electrolytes. However, enhancing energy densities by thinning SSE layers and enabling scalable coating processes remain challenging. While previous studies have addressed thin and flexible SSEs, mainly ionic conductivity was considered for performance evaluation, and no systematic research on the effects of manufacturing conditions on the quality of SSE films was performed. Here, both uniformity and ionic conductivity are considered for evaluating the SSE films under the guidance of machine learning (ML). Three algorithms, principal component analysis, K-means clustering, and support vector machine, are employed to decipher the interdependencies between manufacturing conditions and film performance. Guided by ML, a 40 mu m SSE film with high ionic conductivity and good uniformity is used to construct a LiNi0.8Co0.1Mn0.1O2 parallel to Li6PS5Cl parallel to LiIn cell demonstrating 100 cycles. This study presents an efficient ML-assisted approach to optimize scalable production of high-quality SSE films

New insights into Li distribution in the superionic argyrodite Li6PS5Cl.

By using temperature-dependent neutron powder diffraction combined with maximum entropy method analysis, a previously unreported Li lattice site was discovered in the argyrodite Li6PS5Cl solid-state electrolyte. This new finding enables a more complete description of the Li diffusion model in argyrodites, providing structural guidance for designing novel high-conductivity solid-state electrolytes

Quantitative analysis of sodium metal deposition and interphase in Na metal batteries

Sodium-ion batteries exhibit significant promise as a viable alternative to current lithium-ion technologies owing to their sustainability, low cost per energy density, reliability, and safety. Despite recent advancements in cathode materials for this category of energy storage systems, the primary challenge in realizing practical applications of sodium-ion systems is the absence of an anode system with high energy density and durability. Although Na metal is the ultimate anode that can facilitate high-energy sodium-ion batteries, its use remains limited due to safety concerns and the high-capacity loss associated with the high reactivity of Na metal. In this study, titration gas chromatography is employed to accurately quantify the sodium inventory loss in ether- and carbonate-based electrolytes. Uniaxial pressure is developed as a powerful tool to control the deposition of sodium metal with dense morphology, thereby enabling high initial coulombic efficiencies. In ether-based electrolytes, the Na metal surface exhibits the presence of a uniform solid electrolyte interphase layer, primarily characterized by favorable inorganic chemical components with close-packed structures. The full cell, utilizing a controlled electroplated sodium metal in ether-based electrolyte, provides capacity retention of 91.84% after 500 cycles at 2C current rate and delivers 86 mA h g−1 discharge capacity at 45C current rate, suggesting the potential to enable Na metal in the next generation of sodium-ion technologies with specifications close to practical requirements

High-performing All-solid-state Sodium-ion Batteries Enabled by the Presodiation of Hard Carbon

All-solid-state sodium ion batteries (AS3iBs) are highly sought after for stationary energy storage systems due to their suitable safety and stability over a wide temperature range. Hard carbon (HC), which is low cost, exhibits a low redox potential, and a high capacity, is integral to achieve a practical large-scale sodium-ion battery. However, the energy density of the battery utilizing this anode material is hampered by its low initial Coulombic efficiency (ICE). Herein, two strategies, namely (i) thermal treatment and (ii) presodiation by thermal decomposition of NaBH4, are explored to improve the ICE of pristine HC. Raman spectroscopy, X-ray photoelectron spectroscopy and electrochemical characterizations elucidate that the thermal treatment increases the Csp2 content in the HC structure, while the presodiation supplies the sodium to occupy the intrinsic irreversible sites. Consequently, presodiated HC exhibits an outstanding ICE (>99%) compared to the thermally treated (90%) or pristine HC (83%) in half-cell configurations. More importantly, AS3iB using presodiated HC and NaCrO2 as the anode and cathode, respectively, exhibits a high ICE of 92% and an initial discharge energy density of 294 Wh kg_cathode^(-1

Evaluating Electrolyte-Anode Interface Stability in Sodium All-Solid-State Batteries.

All-solid-state batteries have recently gained considerable attention due to their potential improvements in safety, energy density, and cycle-life compared to conventional liquid electrolyte batteries. Sodium all-solid-state batteries also offer the potential to eliminate costly materials containing lithium, nickel, and cobalt, making them ideal for emerging grid energy storage applications. However, significant work is required to understand the persisting limitations and long-term cyclability of Na all-solid-state-based batteries. In this work, we demonstrate the importance of careful solid electrolyte selection for use against an alloy anode in Na all-solid-state batteries. Three emerging solid electrolyte material classes were chosen for this study: the chloride Na2.25Y0.25Zr0.75Cl6, sulfide Na3PS4, and borohydride Na2(B10H10)0.5(B12H12)0.5. Focused ion beam scanning electron microscopy (FIB-SEM) imaging, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) were utilized to characterize the evolution of the anode-electrolyte interface upon electrochemical cycling. The obtained results revealed that the interface stability is determined by both the intrinsic electrochemical stability of the solid electrolyte and the passivating properties of the formed interfacial products. With appropriate material selection for stability at the respective anode and cathode interfaces, stable cycling performance can be achieved for Na all-solid-state batteries