A prototype of dual-ion conductor for all-solid-state lithium batteries

Ductile Inorganic Solid Electrolytes for All-Solid-State Lithium Batteries

Solid electrolytes, as the core of all-solid-state batteries (ASSBs), play a crucial role in determining the kinetics of ion transport and the interface compatibility with cathodes and anodes, which can be subdivided into catholytes, bulk electrolytes, and anolytes based on their functional characteristics. Among various inorganic solid electrolytes, ductile solid electrolytes, distinguished from rigid oxide electrolytes, exhibit excellent ion transport properties even under cold pressing, thus holding greater promise for industrialization. However, the challenge lies in finding a ductile solid electrolyte that can simultaneously serve as catholyte, bulk electrolyte, and anolyte. Fortunately, due to the immobility of solid electrolytes, combining multiple types of solid electrolytes allows for leveraging their respective advantages. In this review, we discuss five types of solid electrolytes, sulfides, halides, nitrides, antiperovskite-type, and complex hydrides, and the challenges and superiorities for these electrolytes are also addressed. The impact of pressure on ASSBs has been systematically discussed. Furthermore, the suitability of electrolytes as the catholyte, bulk electrolyte, and anolyte is discussed based on their functional characteristics and physicochemical properties. This discussion aims to deepen our understanding of solid electrolytes, enabling us to harness the advantages of various types of solid electrolytes and develop practical, high-performance ASSBs.

Entropy-Modulated Short-Chain Cathode for Low-Temperature All-Solid-State Li-S Batteries

All-solid-state Li-S batteries (ASSLSBs) due to high theoretical energy density and exceptional safety are highly desirable for electric aircraft. However, as the flight altitude rises, the low-temperature performance is hampered by inadequate practical capacity. Here, we discover that low-temperature sulfur utilization is constrained by the multi-step endothermic conversion reaction. By introducing multi-chalcogen to modulate the local entropy, a short-chain molecule cathode is designed to shorten the reduction pathways and enhance low-temperature discharge capacity. Furthermore, the mismatched lithiation lattice of the short-chain cathode reduces the decomposition energy barriers, thus enhancing low-temperature charge/discharge reversibility. The designed short-chain cathode exhibits high cathode utilization (99.4 %) and cycling stability (400 cycles, 92.2 % retention) at room temperature, as well as delivers excellent discharge capacity (579.6 mAh g-1, -40 °C) and cycling performance (100 cycles, 98.4 % retention, 394.9 Wh kg-1electrode, -20 °C) at low temperature. This study presents new opportunities to stimulate the development of low-temperature ASSLSBs.

Intercepting Dendrite Growth With a Heterogeneous Solid Electrolyte for Long-Life All-Solid-State Lithium Metal Batteries

The application of lithium metal anode in all-solid-state batteries has the potential to achieve both high energy density and safety performance. However, the presence of serious dendrite issues hinders this potential. Here, the ion transport pathways and orientation of dendrite growth are regulated by utilizing the differences of ionic conductivity in heterogeneous electrolytes. The in situ formed Li-Ge alloy phases from the spontaneous reaction between Li10GeP2S12 and the attracted dendrites greatly enhance the ability to resist dendrite growth. As an outcome, the heterogeneous electrolyte achieves a high critical current density of 2.1 mA cm-2 and long-term stable symmetrical battery operation (0.3 mA cm-2 for 17 000 h and 1.0 mA cm-2 for 2000 h). Besides, due to the superior interfacial stability and low interface impedance between the heterogeneous electrolyte and lithium anode, the Li||LiNi0.8Co0.1Mn0.1O2 full battery exhibits great cycling stability (80.5% after 500 cycles at 1.0 mA cm-2) and rate performance (125.4 mAh g at 2.0 mA cm-2). This work provides a unique strategy of interface regulation via heterogeneous electrolytes design, offering insights into the development of state-of the-art all-solid-state batteries.

Dual Ionic Pathways in Semi-Solid Electrolyte based on Binary Metal-Organic Frameworks Enable Stable Operation of Li-Metal Batteries at Extremely High Temperatures

The rapid development of the electronics market necessitates energy storage devices characterized by high energy density and capacity, alongside the ability to maintain stable and safe operation under harsh conditions, particularly elevated temperatures. In this study, a semi-solid-state electrolyte (SSSE) for Li-metal batteries (LMB) is synthesized by integrating metal-organic frameworks (MOFs) as host materials featuring a hierarchical pore structure. A trace amount of liquid electrolyte (LE) is entrapped within these pores through electrochemical activation. These findings demonstrate that this structure exhibits outstanding properties, including remarkably high thermal stability, an extended electrochemical window (5.25 V vs Li/Li+), and robust lithium-ion conductivity (2.04 × 10-4 S cm-1), owing to the synergistic effect of the hierarchical MOF pores facilitating the storage and transport of Li ions. The Li//LiFePO4 cell incorporating prepared SSSE shows excellent capacity retention, retaining 97% (162.8 mAh g-1) of their initial capacity after 100 cycles at 1 C rate at an extremely high temperature of 95 °C. It is believed that this study not only advances the understanding of ion transport in MOF-based SSSE but also significantly contributes to the development of LMB capable of stable and safe operation even under extremely high temperatures.

Enhancing Long Stability of Solid-State Batteries Through High-Energy Ball Milling-Induced Decomposition of Sulfide-Based Electrolyte to Sulfur

Metal sulfides are increasingly favored as cathode materials in all-solid-state batteries (ASSBs) due to their high energy density, stability, affordability, and conductivity. Metal sulfides often exhibit capacities exceeding their theoretical limits, a phenomenon that remains not fully understood. In this study, it reveals that this phenomenon is primarily due to the sulfur decomposition from sulfide-based electrolyte. By employing the high-energy ball milling (HEBM) technique, the deposition of sulfide-based electrolyte onto sulfur is intentionally promoted, resulting in higher charge capacities compared to the discharge capacities and surpass theoretical limits of metal sulfides. Using chromium sulfide (Cr2S3) as the active material, the sulfur decomposed from sulfide-based electrolyte transforms into lithium sulfide (Li2S) after discharge, resulting in an increased capacity by ≈439.6 mAh g-1 and improved cycling stability. Consequently, it demonstrates a specific capacity surpassing 1200 mAh g-1 with a capacity retention of over 80% after 650 cycles, maintaining cycling stability for more than 1900 cycles and achieving a Coulombic efficiency exceeding 99.9%. This versatile HEBM approach enables the fabrication of ASSBs utilizing various transition metal sulfides, such as molybdenum disulfide (MoS2), niobium disulfide (NbS2), and iron disulfide (FeS2), all exhibiting over theoretical limited capacities and prolonged cycling capabilities.

Permeable void-free interface for all-solid-state alkali-ion polymer batteries

All-solid-state batteries suffer from a loss of contact between the electrode and electrolyte particles, leading to poor cyclability. Here, a void-free ion-permeable interface between the solid-state polymer electrolyte and electrode is constructed in situ during cycling using charge/discharge voltage as the stimulus. During the charge-discharge, the permeation phase fills the voids at the interface and penetrates the electrode, forming strong bonds with the cathode and effectively mitigating the contact problem. Our all-solid-state potassium ion polymer batteries maintain high Coulombic efficiency more than 2000 cycles at a high operating voltage of 4.5 volt and stably cycle more than 500 cycles even at 4.6 volt. Our rational design for mitigating the contact problem is versatile, as demonstrated by the scalability of all-solid-state graphite-based polymer potassium-ion pouch cells and all-solid-state lithium-ion polymer batteries.

Constructing An Oxyhalide Interface for 4.8 V-Tolerant High-Nickel Cathodes in All-Solid-State Lithium-Ion Batteries

All-solid-state lithium batteries (ASSBs) have received increasing attentions as one promising candidate for the next-generation energy storage devices. Among various solid electrolytes, sulfide-based ASSBs combined with layered oxide cathodes have emerged due to the high energy density and safety performance, even at high-voltage conditions. However, the interface compatibility issues remain to be solved at the interface between the oxide cathode and sulfide electrolyte. To circumvent this issue, we propose a simple but effective approach to magic the adverse surface alkali into a uniform oxyhalide coating on LiNi0.8Co0.1Mn0.1O2 (NCM811) via a controllable gas-solid reaction. Due to the enhancement of the close contact at interface, the ASSBs exhibit improved kinetic performance across a broad temperature range, especially at the freezing point. Besides, owing to the high-voltage tolerance of the protective layer, ASSBs demonstrate excellent cyclic stability under high cutoff voltages (500 cycles~94.0 % at 4.5 V, 200 cycles~80.4 % at 4.8 V). This work provides insights into using a high voltage stable oxyhalide coating strategy to enhance the development of high energy density ASSBs.

Dual-ion conductors: from liquid to solid

The traditional working principle within lithium-ion batteries relies on Li+ shuttling between the cathode and anode, namely the rocking-chair mechanism. A single working ion constrains the possibilities for battery design and the selection of electrode materials, while realizing multiple working ions offers the potential to break through the fundamental principles of traditional battery construction. Accordingly, it is necessary to develop dual-ion conductors to enable the migration of multiple working ions. This focus article starts by introducing traditional dual-ion batteries based on liquid electrolytes and their pros and cons. Then, solidifying liquid dual-ion conductors is expected to overcome these drawbacks, so the development of solid dual-ion conductors is discussed in detail. Specifically, basic design principles of solid dual-ion conductors are briefly proposed, including constructing continuous ion transport channels and choosing appropriately sized ion carriers. The potential applications of solid dual-ion conductors are also summarized, such as stabilizing the electrode/electrolyte interface and activating additional redox couples. The goal of this article is to inspire researchers in the development of dual-ion conductors and to contribute to the advancement of all-solid-state batteries.