All-solid-state Lithium-sulfur Batteries Research Articles

Understanding the role of interfaces in solid-state lithium-sulfur batteries

All-solid-state lithium-sulfur batteries (ASSLSBs) exhibit huge potential applications in electrical energy storage systems due to their unique advantages, such as low costs, safety and high energy density. However, the issues facing solid-state electrolyte (SSE)/electrode interfaces, including lithium dendrite growth, poor interfacial capability and large interfacial resistance, seriously hinder their commercial development. Furthermore, an insufficient fundamental understanding of the interfacial roles during cycling is also a significant challenge for designing and constructing high-performance ASSLSBs. This article provides an in-depth analysis of the origin and issues of SSE/electrode interfaces, summarizes various strategies for resolving these interfacial issues and highlights advanced analytical characterization techniques to effectively investigate the interfacial properties of these systems. Future possible research directions for developing high-performance ASSLSBs are also suggested. Overall, advanced in-situ characterization techniques, intelligent interfacial engineering and a deeper understanding of the interfacial properties will aid the realization of high-performance ASSLSBs.

High-Efficiency Hybrid Sulfur Cathode Based on Electroactive Niobium Tungsten Oxide and Conductive Carbon Nanotubes for All-Solid-State Lithium-Sulfur Batteries.

All-solid-state lithium-sulfur batteries (ASSLSBs) have become a promising candidate because of their high energy density and safety. To ensure the high utilization and electrochemical capacity of sulfur in all-solid-state batteries, both the electronic and ionic conductivities of the sulfur cathode should be as high as possible. In this work, an intercalation-conversion hybrid cathode is proposed by distributing sulfur evenly on electroactive niobium tungsten oxide (Nb18W16O93) and conductive carbon nanotubes (CNTs) for achieving high performance ASSLSBs. Herein, Nb18W16O93 shows good electrochemical lithium storage in the hybrid cathode, which could serve as an effective Li-ion/electron conductor for the conversion of sulfur in the discharge/charge processes to achieve a high utilization of sulfur. However, CNTs could further increase the electronic conductivity of the hybrid cathode by constructing good conductive frameworks and suppress the volumetric fluctuation during the interconversion of sulfur and Li2S. With this strategy, the S/Nb18W16O93/CNT cathode achieves a high sulfur utilization of 91% after one cycle activation with a high gravimetric capacity of 1526 mA h g-1. In addition, excellent rate performance is also obtained at 0.5 C with a reversible capacity of 1262 mA h g-1 after 1000 cycles. This work offers a new perspective to develop ASSLSBs.

High Surface Area N-Doped Carbon Fibers with Accessible Reaction Sites for All-Solid-State Lithium-Sulfur Batteries.

Porous carbon plays a significant role in all-solid-state lithium-sulfur batteries (ASSLSBs) to enhance the electronic conductivity of sulfur. However, the conventional porous carbon used in cell with liquid electrolyte exhibits low efficiency in ASSLSBs because the immobile solid electrolyte (SE) cannot reach sulfur confined in the deep pores. The structure and distribution of pores in carbon highly impact the electrochemical performance of ASSLSBs. Herein, a N-doped carbon fiber with micropores located only at the surface with an ultrahigh surface area of 1519m2 g-1 is designed. As the porous layer is only on the surface, the sulfur hosted in the pores can effectively contact SE; meanwhile the dense core provides excellent electrical conductivity. Therefore, this structurally designed carbon fiber enhances both electron and ion accessibilities, promotes charge transfer, and thus dramatically improves the reaction kinetic in the ASSLSBs and boosts sulfur utilization. Compared to the vapor grown carbon fibers, the ASSLSBs using PAN-derived porous carbon fibers exhibit three times enhancement in the initial capacity of 1166 mAh g-1 at C/20. An exceedingly cycling stability of 710 mAh g-1 is maintained after 220 cycles at C/10, and satisfactory rate capability of 889 mAh g-1 at C/2 is achieved.

All-Solid-State Lithium–Sulfur Batteries Enhanced by Redox Mediators

Redox mediators (RMs) play a vital role in some liquid electrolyte-based electrochemical energy storage systems. However, the concept of redox mediator in solid-state batteries remains unexplored. Here, we selected a group of RM candidates and investigated their behaviors and roles in all-solid-state lithium-sulfur batteries (ASSLSBs). The soluble-type quinone-based RM (AQT) shows the most favorable redox potential and the best redox reversibility that functions well for lithium sulfide (Li2S) oxidation in solid polymer electrolytes. Accordingly, Li2S cathodes with AQT RMs present a significantly reduced energy barrier (average oxidation potential of 2.4 V) during initial charging at 0.1 C at 60 °C and the following discharge capacity of 1133 mAh gs-1. Using operando sulfur K-edge X-ray absorption spectroscopy, we directly tracked the sulfur speciation in ASSLSBs and proved that the solid-polysulfide-solid reaction of Li2S cathodes with RMs facilitated Li2S oxidation. In contrast, for bare Li2S cathodes, the solid-solid Li2S-sulfur direct conversion in the first charge cycle results in a high energy barrier for activation (charge to ∼4 V) and low sulfur utilization. The Li2S@AQT cell demonstrates superior cycling stability (average Coulombic efficiency 98.9% for 150 cycles) and rate capability owing to the effective AQT-enhanced Li-S reaction kinetics. This work reveals the evolution of sulfur species in ASSLSBs and realizes the fast Li-S reaction kinetics by designing an effective sulfur speciation pathway.

All-Solid-State Lithium Metal Batteries with Sulfide Electrolytes: Understanding Interfacial Ion and Electron Transport

ConspectusWith the ever-growing demand for high energy density and high safety of energy storage technologies, all-solid-state lithium metal batteries (ASSLMBs) including all-solid-state lithium ion batteries (ASSLIBs) and all-solid-state lithium–sulfur batteries (ASSLSBs) have received considerable attention in recent years. To realize ASSLMBs, various solid-state electrolytes have been rapidly developed. Among them, sulfide electrolytes (SEs) demonstrate the highest ionic conductivity (>10 mS·cm–1) and the most favorable mechanical properties. However, the commercialization of SE-based ASSLMBs has been stymied by sluggish interfacial ion and electron transport kinetics, which arises from the detrimental interfacial reactions, poor interfacial solid–solid contact, and lithium dendrite growth. To overcome the interfacial challenges, an insightful understanding of the complex interfacial ion and electron transport processes in SE-based ASSLMBs is of the foremost importance. Although most of the previous review papers underscored the interfacial challenges and summarized the corresponding strategies, a fundamental understanding of the interfacial ions and electron-transport kinetics in SE-based ASSLMBs has not yet been presented. This Account therefore primarily summarizes our recent understanding of SE-based ASSLMBs from the perspectives of interfacial ion and electron transport, aiming to provide an insightful understanding of interfacial kinetics.We first compare various solid-state electrolytes including SEs, oxide electrolytes, halide electrolytes, polymer electrolytes, borohydride electrolytes in terms of their ionic conductivity, electrochemical stability windows, and mechanical properties, aiming to justify the advantages of SEs in ASSLMBs. Then, the interfacial challenges at both cathode and anode interfaces of SE-based ASSLIBs and SE-based ASSLSBs are presented, respectively. These interfacial challenges significantly hinder the interfacial ion and electron transport. To boost the interfacial charge transfer kinetics, our recent research advances related to the cathode interface between transition-metal oxides (TMOs) and SEs are then discussed. In parallel, our latest progress on SE-based ASSLSBs is also summarized from the perspective of interfacial kinetics. At the anode interface, our innovative strategies to enhance interfacial Li ion transport between Li metal and SEs are recapped. Finally, conclusions and our perspectives on SE-based ASSLMBs are presented. We believe that this specific Account provides an insightful understanding of interfacial ion and electron transport behavior in SE-based ASSLMBs.

Congener Substitution Reinforced Li7P2.9Sb0.1S10.75O0.25 Glass-Ceramic Electrolytes for All-Solid-State Lithium-Sulfur Batteries.

Glass-ceramic sulfide solid electrolytes like Li7P3S11 are practicable propellants for safe and high-performance all-solid-state lithium-sulfur batteries (ASSLSBs); however, the stability and conductivity issues remain unsatisfactory. Herein, we propose a congener substitution strategy to optimize Li7P3S11 as Li7P2.9Sb0.1S10.75O0.25 via chemical bond and structure regulation. Specifically, Li7P2.9Sb0.1S10.75O0.25 is obtained by a Sb2O5 dopant to achieve partial Sb/P and O/S substitution. Benefiting from the strengthened oxysulfide structural unit of POS33- and P2OS64- with bridging oxygen atoms and a distorted lattice configuration of the Sb-S tetrahedron, the Li7P2.9Sb0.1S10.75O0.25 electrolyte exhibits prominent chemical stability and high ionic conductivity. Besides the improved air stability, the ionic conductivity of Li7P2.9Sb0.1S10.75O0.25 could reach 1.61 × 10-3 S cm-1 at room temperature with a wide electrochemical window of up to 5 V (vs Li/Li+), as well as good stability against Li and Li-In alloy anodes. Consequently, the ASSLSB with the Li7P2.9Sb0.1S10.75O0.25 electrolyte shows high discharge capacities of 1374.4 mAh g-1 (0.05C, 50th cycle) at room temperature and 1365.4 mAh g-1 (0.1C, 100th cycle) at 60 °C. The battery also presents remarkable rate performance (1158.3 mAh g-1 at 1C) and high Coulombic efficiency (>99.8%). This work provides a feasible technical route for fabricating ASSLSBs.

S/MWCNt/LLZO composite electrode with e−/S/Li+ conductive network for all-solid -state Lithium–Sulfur batteries

Traditional liquid lithium-sulfur batteries have two key problems: poor safety and shuttle effect. These two challenges can be overcome by using solid-state electrolytes. But poor ionic and electronic conductivity due to solid/solid contact between the electrode and the electrolyte for all-solid-state lithium-sulfur batteries (ASSLSBs). Here, we have synthesized Li6.4Ga0.2La3Zr2O12(LLZO) conductive ceramics with high ionic conductivity. LLZO is used as the lithium-ion conductor and multi-walled carbon nanotubes (MWCNt) are used as the electronic conductor to form S/MWCNt/LLZO by the thermal diffusion method, resulting in an e−/S/Li+ conductive network. The prepared S/MWCNt/LLZO composite material, composite solid electrolyte, and lithium metal are assembled into ASSLSBs. After 50 cycles, the high capacity of 825 ​mAh·g−1 is maintained with 72.62% capacity retention at 0.2C and 45 ​°C. The higher capacity indicates the success of forming a conductive network that can improve the electrochemical performance of ASSLSBs. At 0.2C, the capacity of the S/MWCNt/LLZO composite cathode remains at 873 ​mAh·g−1 after 60 cycles when the operating temperature is increased to 60 ​°C, indicating good cycle performance.

Ultrasmall Li2S-Carbon Nanotube Nanocomposites for High-Rate All-Solid-State Lithium-Sulfur Batteries.

Due to the intrinsic poor ionic/electronic conductivities of Li2S, it is a great challenge to realize high-rate all-solid-state lithium-sulfur batteries (ASSLSBs) with long cyclic performance. Herein, ultrasmall Li2S (∼15 nm) is evenly deposited on a carbon nanotube (CNT) via a facile liquid-phase method to address these issues. The unique structure of the Li2S deposited on a CNT composite cathode can improve ionic/electronic conductivities of Li2S effectively and relieve the generated internal stress/strain during cycling. Specifically, the resultant Li/75%Li2S-24%P2S5-1%P2O5/Li10GeP2S12/Li2S-53%CNT ASSLSBs show a reversible capacity of 651.4 mAh g-1 under 1.0C at 60 °C after 300 cycles and even at a much higher cathode load of 5.08 mg cm-2, a high discharge capacity of 556 mAh g-1 can still be obtained under 0.1C after 20 cycles. The outstanding electrochemical performances are also attributed to the high diffusion coefficient of Li2S-53%CNT, which is 39 times that of pristine Li2S. This work presents an efficient procedure to design cathode materials with high ionic/electronic conductivities and paves the way for the successful commercialization of high-rate ASSLSBs.

Polymer-based electrolytes for all-solid-state lithium–sulfur batteries: from fundamental research to performance improvement

With the increasing demand for a higher energy density and a lower cost energy storage system, lithium–sulfur batteries have become one of the promising candidates to replace current Li-ion batteries. However, in liquid electrolyte systems, the lithium dendrite growth and the shuttle effect cause severe safety hazard as well as capacity decay, which hinders the commercialization of practical lithium–sulfur batteries. Polymer-based electrolytes provide a promising solution to these challenges. This type of electrolyte, including polymer and composite polymer electrolytes, demonstrates the capabilities to prevent polysulfide dissolution and suppress lithium dendrite growths, while ensuring good surface contact and high flame resistance. This review summarizes the most recent progress of polymer-based all-solid-state lithium–sulfur batteries (ASSLSB), which revealed mechanisms and challenges of electrolyte ionic conductivity, reaction mechanism, anode/electrolyte interface, and cathode/electrolyte interface. Based on these revealed principles, possible solutions to these challenges such as the addition of inorganic fillers, interface modification, utilization of different types of lithium salt and polymers are introduced. In addition, the state-of-the-art approaches with great performance improvement are highlighted in this review. Finally, we provide perspectives on research directions that can further the understanding and development of polymer-based ASSLSB.

Confining Sulfur in Porous Carbon by Vapor Deposition to Achieve High-Performance Cathode for All-Solid-State Lithium–Sulfur Batteries

All-solid-state lithium–sulfur batteries (ASLBs) have the potential to achieve high energy density because of sulfur’s high theoretical capacity (1672 mAh g–1) while alleviating persistent polysulf...

A novel air-stable Li7Sb0.05P2.95S10.5I0.5 superionic conductor glass-ceramics electrolyte for all-solid-state lithium-sulfur batteries

The blend of air stability and high lithium-ion (Li+) conductivity is not a simplistic approach to attain for sulfide-based solid-state electrolytes (SSEs), which hinders the exploitation of high energy all-solid-state lithium-sulfur batteries (ASSLSBs). Herein we report a novel lithium superionic conductor of Li7Sb0.05P2.95S10.5I0.5 as solid-state glass-ceramics electrolytes obtained by an annealing treatment in a solid-state reaction route. It systematically explores the impact of facile aliovalent dual doping into the newly synthesized solid electrolytes, which have influenced higher Li+ conductivity of 2.55 × 10−3 Scm−1 at room temperature, and wide range of voltage stability vs. Li/Li+ up to 7 V. Except that, an activation barrier of Li7Sb0.05P2.95S10.5I0.5 for Li+ migration drops expressively due to optimizing the dopant contents, and subsequently defects produced. The electrolyte also achieved significant air stability based on Hard and Soft Acid/Base (HSAB) theory. The intrinsic structural aspects of the air stability for Li7P3S11 and Li7Sb0.05P2.95S10.5I0.5 solid-state electrolytes are premeditated using a combination of ex-situ X-ray photoelectron spectroscopy, XRD as well as Raman spectroscopy and SEM. The Li2S-VGCF-SSE composite cathode with Li7Sb0.05P2.95S10.5I0.5 SSE exhibited a high initial discharge capacity of 622.3 mAhg−1 at 0.060 mAcm−2, and ASSLSB was retained over 683.3 mAh g−1 after 15th cycle at room temperature, better than pristine Li7P3S11 SSE-based cell. This research provides a novel concept on the design of air-stable and superionic conductor solid-state electrolytes for high-performance ASSLSBs.

Rational Designed Mixed-Conductive Sulfur Cathodes for All-Solid-State Lithium Batteries.

All-solid-state lithium-sulfur batteries (ASSLSBs) hold great promise for safe and high-energy-density energy storage. However, developing high-performance sulfur cathodes has been proven difficult due to low electronic and ionic conductivities and large volume change of sulfur during charge and discharge. Here, we reported an approach to synthesize sulfur cathodes with a mixed electronic and ionic conductivity by infiltrating a solution consisting of Li3PS4 (LPS) solid electrolyte and S active material into a mesoporous carbon (CMK-3). This approach leads to a uniform dispersion of amorphous Li3PS7 (L3PS) catholyte in an electronically conductive carbon matrix, enabling high and balanced electronic/ionic conductivities in the cathode composite. The inherent porous structure of CMK-3 also helps to accommodate the strain/stress generated during the expansion and shrinkage of the active material. In sulfide-based all-solid-state batteries with Li metal as the anode, this cathode composite delivered a high capacity of 1025 mAh g-1 after 50 cycles at 60 °C at 1/8C. This work highlights the important role of high and balanced electronic and ionic conductivities in developing high-performance sulfur cathodes for ASSLSBs.

Totally compatible P4S10+n cathodes with self-generated Li+ pathways for sulfide-based all-solid-state batteries

All-solid-state lithium sulfur batteries (ASSLSBs) are considered promising candidates for next-generation energy-storage systems due to their enhanced safety and high theoretical energy density. However, usually both solid-state electrolyte (SSE) and conductive carbon need to be incorporated into the cathode composite to provide Li+/electron pathways, leading to the reduced energy density and inevitable SSE decomposition. Moreover, the real electrochemical behavior of S or Li2S cathodes can not be reflected due to the partially overlapped redox reaction of SSE. Herein, a series of unique P4S10+n cathodes for high-performance ASSLSBs that totally do not need any extra SSE additives are reported. Synchrotron-based X-ray absorption near edge structure coupled with other analyses confirmed that ionic conductive Li3PS4 together with Li4P2S6 components can be electrochemically self-generated during lithiation process and partially maintained to provide fast Li+ transport pathways within the cathode layer. This is further evidenced by a 30–43-fold higher reversible capacity for P4S10+n/C cathodes compared to a S/C cathode. Bulk-type ASSLSBs based on the P4S34/C cathode show a highly reversible capacity of 883 ​mAh g−1 and stable cycling performance over 180 cycles with a high active material content of 70 ​wt%. The present study provides a promising approach for generating ionic conductive components from the electrode itself to facilitate Li+ migration within electrodes in ASSLSBs.

Kinetics of all-solid-state sulfur cathodes

All-solid-state lithium sulfur batteries (ASLSB) have many advantages over liquid electrolyte-based lithium sulfur batteries such as high sulfur utilization, low electrolyte-to-sulfur ratio and low self-discharge. However, the kinetics of all-solid-state sulfur cathodes is not well understood, which is critical to achieve their full potential. In this work, we determine the contributions of different processes to the overall kinetics of sulfur electrodes using Electrochemical Impedance Spectroscopy (EIS) and Gravimetric Intermittent Titration Technique (GITT). We show that the impedance of sulfur electrodes can be well described by the Transmission Line Model (TLM). It is found that the kinetics of the sulfur electrode is determined primarily by ionic migration at the electrode level and diffusion within the sulfur active materials. Based on this understanding, we compared kinetics of sulfur electrodes with different solid electrolytes and mixing methods. Electrodes using amorphous sulfide solid electrolyte and impregnated S/C composites display the best kinetics. ASLSB possess high capacities at moderate rates at room temperature, and can operate even at 120 ​°C. Combined with the negligible self-discharge over a year, we believe that ASLSB is a promising candidate for high-energy primary batteries.

Free-standing sulfide/polymer composite solid electrolyte membranes with high conductance for all-solid-state lithium batteries

Bulk-type all-solid-state lithium batteries (ASSLBs) with high theoretical capacity and good safety are considered to be promising candidates as future energy storage devices. The ASSLBs with inorganic electrolytes usually have a thick electrolyte layer (more than 1 mm), which significantly reduces the cell-based energy density; therefore, a free-standing high-conductance electrolyte layer with a low thickness is essential for high-performance ASSLBs. In this work, we prepare free-standing 78Li2S–22P2S5 glass-ceramic (7822gc) composite solid electrolyte membranes reinforced with polymer electrolytes with a thickness of 120 μm through a liquid-phase method and systematically investigate the effects of solvents and polymer electrolytes on the microstructure and electrochemical properties of the 7822gc/polymer composite membranes. The sulfide/PEO and sulfide/PVDF composite electrolytes without lithium salt show an ionic conductivity of 2–4 × 10−4 S cm−1 at room temperature, while the conductivity of those with lithium salt is enhanced to 4–7 × 10−4 S cm−1. With such a high conductivity and low thickness, an ultra-high areal conductance of 59.0 mS cm−2 is obtained for the composite electrolyte membranes, which is ~2.7 times of that of pure 7822gc electrolyte pellets. All-solid-state lithium-sulfur batteries (ASSLSBs) with a sulfur/carbon nanotube composite cathode and a Li–In alloy anode are prepared. The cell-based energy density is as high as 87.0 Ah L−1. A discharge capacity of 725.1 mA h g−1 at 0.176 mA cm−2 after 100 cycles and a high capacity retention of 93.2% are achieved for the cells with 7822gc/polymer composite electrolyte membranes.

Improved interfacial electronic contacts powering high sulfur utilization in all-solid-state lithium–sulfur batteries

All-solid-state lithium–sulfur batteries (ASSLSBs) afford a novel avenue for next-generation high energy density lithium–sulfur batteries due to the alleviated potential safety hazards. However, ASSLSBs suffer from high interfacial impedance and poor kinetics of electrochemical reactions. Herein, we probed the interfacial electron transfer between active sulfur and conductive carbon in a working cell. The co-axial carbon nanotube@sulfur composite with more robust electron contacts enables fast electron transportation and reduced interfacial charge transfer impedance, leading to a high sulfur utilization and excellent electrochemical performance. An initial discharge capacity of 1138.7 mAh g−1 at 0.21 mA cm−2 (0.1C) with a capacity retention of 87.7% after 200 cycles is achieved at a sulfur loading of 1.3 mg cm−2. Moreover, the cathode with superior and uniform electronic contacts delivers better rate capability and a higher discharge specific capacity at a high sulfur loading ranging from 3.8 to 5.9 mg cm−2. This work verifies the significance of 3D interconnected electronic pathways in the sulfur cathode for high performance ASSLSBs.

Solid/Solid Interfacial Architecturing of Solid Polymer Electrolyte-Based All-Solid-State Lithium-Sulfur Batteries by Atomic Layer Deposition.

Solid polymer electrolytes (SPEs)-based all-solid-state lithium-sulfur batteries (ASSLSBs) have attracted extensive research attention due to their high energy density and safe operation, which provide potential solutions to the increasing need for harnessing higher energy densities. There is little progress made, however, in the development of ASSLSBs to improve simultaneously energy density and long-term cycling life, mostly due to the "shuttle effect" of lithium polysulfide intermediates in the SPEs and the low interfacial compatibility between the metal lithium anode and the SPE. In this work, the issues of solid/solid interfacial architecturing through atomic layer deposition of Al2 O3 on poly(ethylene oxide)-lithium bis(trifluoromethanesulfonyl)imide SPE surface are effectively addressed. The Al2 O3 coating promotes the suppression of lithium dendrite formation for over 500 h. ASSLSBs fabricated with two layers of Al2 O3 -coated SPE deliver high gravimetric/areal capacity and Coulombic efficiency, as well as excellent cycling stability and extremely low self-discharge rate. This work provides not only a simple and effective approach to boost the electrochemical performances of SPE-based ASSLSBs, but also enriches the fundamental understanding regarding the underlying mechanism responsible for their performance.

High Capacity and Superior Cyclic Performances of All-Solid-State Lithium-Sulfur Batteries Enabled by a High-Conductivity Li10SnP2S12 Solid Electrolyte.

All-solid-state lithium-sulfur batteries (ASSLSBs) employing sulfide-based solid electrolytes have gained widespread attention for their high energy density and intrinsic safety. Li10SnP2S12 is identified as one of the most rivaling candidates in sulfide electrolytes. Herein, a highly Li-ion-conductive Li10SnP2S12 solid-state electrolyte (SSE) is synthesized via a combination of high-energy ball-milling and heat treatment processes, which is more facile and efficient compared with other previously reported methods. The obtained Li10SnP2S12 SSE exhibits high ionic conductivity (3.2 × 10-3 S cm-1) at room temperature (RT). The effects of the annealing temperature on the Li-ion conductivity and activation energy of Li10SnP2S12 are also thoroughly studied. Moreover, the ASSLSBs based on the Li10SnP2S12 electrolyte are constructed, and they deliver a high initial capacity of 1601.7 mAh g-1 at 40 mA g-1. A favorable capacity retention upon cycling and a good rate performance are also achieved at RT. Concomitantly, the Coulombic efficiency approaches 100% during the prolonged cycling. This work tremendously accelerates the practical applications of the Li10SnP2S12 SSE among the emerging high-energy ASSLSBs.

In Situ Generated Li2S-C Nanocomposite for High-Capacity and Long-Life All-Solid-State Lithium Sulfur Batteries with Ultrahigh Areal Mass Loading.

All-solid-state lithium-sulfur batteries (ASSLSBs) have attracted great attention due to their inherent ability to eliminate the two critical issues (polysulfide shuttle effect and safety) of traditional liquid electrolyte based Li-S batteries. However, it remains a huge challenge for ASSLSBs to achieve high areal active mass loading and high active material utilization simultaneously due to the insulating nature of sulfur and Li2S, and the large volume change during cycling. Herein, a Li2S@C nanocomposite with Li2S nanocrystals uniformly embedded in conductive carbon matrix, is in situ generated by the combustion of lithium metal with CS2. Benefiting from its unique architecture, the Li2S@C exhibits exceptional electrochemical performance as cathode for ASSLSBs, with both ultrahigh areal Li2S loading (7 mg cm-2) and 91% of Li2S utilization (corresponding to a reversible capacity of 1067 mAh g-1). Moreover, the Li2S@C also possesses outstanding rate capability and cycling stability. High reversible capacity of 644 mAh g-1 is delivered at 2 mA cm-2 even after 700 cycles. This work demonstrates that ASSLSBs with superior electrochemical performance can be realized via rational design of the cathode structure, which provides a promising prospect to the development of ASSLSBs with practical energy density surpassing that of lithium ion batteries.

High-Conductivity Argyrodite Li6PS5Cl Solid Electrolytes Prepared via Optimized Sintering Processes for All-Solid-State Lithium–Sulfur Batteries

Highly Li-ion conductive Li6PS5Cl solid-state electrolytes (SSEs) were prepared by solid-state sintering method. The influence of sintering temperature and duration on the phase, ionic conductivity, and activation energy of Li6PS5Cl was systematically investigated. The Li6PS5Cl electrolyte with a high ionic conductivity of 3.15 × 10-3 S cm-1 at room temperature (RT) was obtained by sintering at 550 °C for just 10 min, which was more efficient taking into account such a short preparation time in comparison with other reported methods to synthesize Li6PS5Cl SSEs. All-solid-state lithium sulfur batteries (ASSLSBs) based on the Li6PS5Cl SSE were assembled by using the nano-sulfur/multiwall carbon nanotube composite combined with Li6PS5Cl as the cathode and Li-In alloy as the anode. The cell delivered a high discharge capacity of 1850 mAh g-1 at RT for the first full cycle at 0.176 mA cm-2 (∼0.1C). The discharge capacity was 1393 mAh g-1 after 50 cycles. In addition, the Coulombic efficiency remained nearly 100% during galvanostatic cycling. The experimental data showed that Li6PS5Cl was a good candidate for the SSE used in ASSLSBs.