Decoupling Parasitic Reactions at the Positive Electrode Interfaces in Argyrodite-Based Systems

Tailoring Interfacial Structures to Regulate Carrier Transport in Solid-State Batteries

Solid-state lithium-ion batteries (SSLIBs) have been considered as the priority candidate for next-generation energy storage system, due to their advantages in safety and energy density compare with conventional liquid electrolyte systems. However, the introduction of numerous solid-solid interfaces results in a series of issues, hindering the further development of SSLIBs. Therefore, a thorough understanding on the interfacial issues is essential to promote the practical applications for SSLIBs. In this review, the interface issues are discussed from the perspective of transportation mechanism of electrons and lithium ions, including internal interfaces within cathode/anode composites and solid electrolytes (SEs), as well as the apparent electrode/SEs interfaces. The corresponding interface modification strategies, such as passivation layer design, conductive binders, and thermal sintering methods, are comprehensively summarized. Through establishing the correlation between carrier transport network and corresponding battery electrochemical performance, the design principles for achieving a selective carrier transport network are systematically elucidated. Additionally, the future challenges are speculated and research directions in tailoring interfacial structure for SSLIBs. By providing the insightful review and outlook on interfacial charge transfer, the industrialization of SSLIBs are aimed to promoted.

Engineering Detrimental Functional Groups in Conductive Additives Toward High-Performance All-Solid-State Batteries

Conductive additives are of great importance for the adequate utilization of active materials in all-solid-state lithium batteries by establishing conductive networks in the composite cathode. However, it usually causes severe interfacial side reactions with solid electrolytes, especially sulfide electrolytes, leading to sluggish ion transportation and accelerated performance degradation. Herein, a simple hydrogen thermal reduction process is proposed on a commonly used conductive additive Super P, which effectively removes the surface oxygen functional groups and weakens the interfacial side reactions with sulfide. With a small amount of 1 wt % reduced Super P, ASSLBs demonstrates a competitive capacity of 180.2 mAh g-1, which is much higher than the 130.8 mAh g-1 of untreated Super P. Impressively, reduced Super P based ASSLBs also exhibit a higher capacity retention of 81.8 % than 64.6 % of untreated Super P. The cathode interfacial chemical evolutions reveal that reduced Super P could effectively alleviate the side reactions of sulfide. Reduced Super P shows better reversible capacity compared to reduced carbon nanofiber with almost no loss of capacity retention, due to its more complete conductive network. Our results highlight the importance of oxygen-containing functional groups for conductive additives, lightening the prospect of low-cost 0D conductive additives for practical ASSLBs.

State of Charge-Dependent Impedance Spectroscopy as a Helpful Tool to Identify Reasons for Fast Capacity Fading in All-Solid-State Batteries

Thiophosphate-based all-solid-state batteries (ASSBs) are considered the most promising candidate for the next generation of energy storage systems. However, thiophosphate-based ASSBs suffer from fast capacity fading with nickel-rich cathode materials. In many reports, this capacity fading is attributed to an increase of the charge transfer resistance of the composite cathode caused by interface degradation and/or chemo-mechanical failure. The change in the charge transfer resistance is typically determined using impedance spectroscopy after charging the cells. In this work, we demonstrate that large differences in the long-term cycling performance also arise in cells, which exhibit a comparable charge transfer resistance at the cathode side. Our results confirm that the charge transfer resistance of the cathode is not necessarily responsible for capacity fading. Other processes, such as resistive processes on the anode side, can also play a major role. Since these processes usually depend on the state of charge, they may not appear in the impedance spectra of fully charged cells; i.e., analyzing the impedance spectra of charged cells alone is insufficient for the identification of major resistive processes. Thus, we recommend measuring the impedance at different potentials to get a complete understanding of the reasons for capacity fading in ASSBs.

One Stone, Three Birds: An Air and Interface Stable Argyrodite Solid Electrolyte with Multifunctional Nanoshells

Li6 PS5 Cl (LPSC) solid electrolytes, based on Argyrodite, have shown potential for developing high energy density and safe all-solid-state lithium metal batteries. However, challenges such as interfacial reactions, uneven Li deposition, and air instability remain unresolved. To address these issues, a simple and effective approach is proposed to design and prepare a solid electrolyte with unique structural features: Li6 PS4 Cl0.75 -OF0.25 (LPSC-OF0.25 ) with protective LiF@Li2 O nanoshells and F and O-rich internal units. The LPSC-OF0.25 electrolyte exhibits high ionic conductivity and the capability of "killing three birds with one stone" by improving the moist air tolerance, as well as the interface compatibility between the anode or cathode and the solid electrolyte. The improved performance is attributed to the peculiar morphology and the self-generating and self-healing interface coupling capability. When coupled with bare LiCoO2 , the LPSC-OF0.25 electrolyte enables stable operation under high cutoff voltage (≈4.65 V vs Li/Li+ ), thick cathodes (25 mg cm-2 ), and large current density (800 cycles at 2 mA cm-2 ). This rationally designed solid electrolyte offers promising prospects for solid-state batteries with high energy and power density for future long-range electric vehicles and aircrafts.