Niobium sulfide nanocomposites as cathode materials for all-solid-state lithium batteries with enhanced electrochemical performance.

All-solid-state lithium batteries coupled with transition metal sulfide cathodes have gained significant attention due to their high energy density and exceptional safety. However, there are still critical challenges impeding their practical application, such as limited capacity delivery, weak ionic reaction kinetics and volume expansion. Herein, an a-NbS4/20%VGCF@15%Li7P3S11 nanocomposite cathode material is employed in all-solid-state batteries. A certain proportion of VGCF is introduced into crystalline NbS4 in order to mitigate the volume expansion and improve electronic conductivity. At the same time, a-NbS4/20%VGCF is in situ coated with a Li7P3S11 solid electrolyte layer to achieve an intimate interfacial contact. The obtained a-NbS4/20%VGCF@15%Li7P3S11 nanocomposite exhibits a remarkable electronic conductivity (1.0 × 10-1 S cm-1) and ionic conductivity (5.5 × 10-4 S cm-1), which are improved by five and two orders of magnitude compared to those of NbS4, respectively. The Li/Li6PS5Cl/a-NbS4/20%VGCF@15%Li7P3S11 battery exhibits a high initial discharge capacity of 1043.25 mA h g-1 at 0.1 A g-1. Even at 0.5 A g-1, it could provide a reversible capacity of 403.2 mA h g-1 after 500 cycles. This work provides a promising cathode material for all-solid-state lithium batteries with improved ionic/electronic conductivity, high reversible capacity and superior cycling stability.

Deeply Lithiated Carbonaceous Materials for Great Lithium Metal Protection in All-Solid-State Batteries.

Protection of lithium (Li) metal electrode is a core challenge for all-solid-state Li metal batteries (ASSLMBs). Carbon materials with variant structures have shown great effect of Li protection in liquid electrolytes, however, can accelerate the solid-state electrolyte (SE) decomposition owing to the high electronic conductivity, seriously limiting their application in ASSLMBs. Here, a novel strategy is proposed to tailor the carbon materials for efficient Li protection in ASSLMBs, by in situ forming a rational niobium-based Li-rich disordered rock salt (DRS) shell on the carbon materials, providing a favorable percolating Li+ diffusion network for speeding the carbon lithiation, and enabling simultaneously improved lithiophilicity and reduced electronic conductivity of the carbon structure at deep lithiation state. Using the proposed strategy, different carbon materials, such as graphitic carbon paper and carbon nanotubes, are tailored with great ability to speed the interfacial kinetics, homogenize the Li plating/stripping processes, and suppress the SE decompositions, enabling much improved performances of ASSLMBs under various conditions approaching the practical application. This strategy is expected to create a novel roadmap of Li protection for developing reliable high-energy-density ASSLMBs.

Calcium Doped NASICON Electrolyte with Graphite Coating for Stable All-solid-state Sodium Metal Batteries.

All-solid-state sodium metal batteries face the challenges of low ionic conductivity of solid electrolytes and poor wettability towards metallic Na anode. Herein, Na3Zr2Si2PO12 solid electrolyte is doped with Ca2+, obtaining a high ionic conductivity of 2.09×10-3 S cm-1 with low electronic conductivity of 1.43×10-8 S cm-1 at room temperature, which could accelerate Na+ transportation and suppress sodium dendrite growth. Meanwhile, a graphite-based interface layer is coated on Na3.4Zr1.8Ca0.2Si2PO12 (Na3.4Zr1.8Ca0.2Si2PO12-G) in order to improve the solid-solid contact between solid electrolyte and Na anode, realizing a uniform current distribution and smooth Na metal plating/stripping, and thus achieving a triple higher critical current density of 3.5 mA cm-2 compared with that of Na3.4Zr1.8Ca0.2Si2PO12. In addition, the assembled Na3V2(PO4)3/Na3.4Zr1.8Ca0.2Si2PO12-G/Na all-solid-state battery exhibits excellent electrochemical performances with a reversible capacity of 81.47 mAh g-1 at 1 C and capacity retention of 97.75 % after 500 cycles.

Large Organic Polar Molecules Tailored Electrode Interfaces for Stable Lithium Metal Battery.

Lithium (Li) metal batteries (LMBs) are deemed as ones of the most promising energy storage devices for next electrification applications. However, the uneven Li electroplating process caused by the diffusion-limited Li+ transportation at the Li metal surface inherently promotes the formation of dendritic morphology and instable Li interphase, while the sluggish Li+ transfer kinetic can also cause lithiation-induced stress on the cathode materials suffering from serious structural stability. Herein, a novel electrolyte designing strategy is proposed to accelerate the Li+ transfer by introducing a trace of large organic polar molecules of lithium phytate (LP) without significantly altering the electrolyte structure. The LP molecules can afford a competitive solvent attraction mechanism against the solvated Li+, enhancing both the bulk and interfacial Li+ transfer kinetic, and creating better anode/cathode interfaces to suppress the side reactions, resulting in much improved cycling efficiency of LMBs. Using LP-based electrolyte, the performance of LMB pouch cell with a practical capacity of ~1.5 Ah can be improved greatly. This strategy opens up a novel electrolyte designing route for reliable LMBs.

Tungsten and Boron Codoping toward High Ionic Conductivity and Stable Sodium Solid Electrolyte for All-Solid-State Sodium Batteries.

Sodium solid electrolytes with high ionic conductivity and good interfacial stability with sodium metal are crucial to realize high-performance all-solid-state sodium batteries. In this work, W and B-codoped Na3Sb1-xWxS4-xBx solid electrolytes are prepared by melt-quenching with further annealing. The synthesized Na3Sb0.95W0.05S3.95B0.05 solid electrolyte possesses a high ionic conductivity of 11.06 mS cm-1 under 25 °C and shows significantly improved interface compatibility with metal sodium. Specifically, Na/Na3Sb0.95W0.05S3.95B0.05/Na symmetric cell can stable cycle for 500 h under a current density of 0.05 mA cm-2. In addition, the resultant TiS2/Na3Sb0.95W0.05S3.95B0.05/Na battery exhibits an initial charge capacity of 164.1 mAh g-1 at 0.1 C with a capacity retention of 76.4% after 100 cycles. This work provides a new strategy to realize the high ionic conductivity of sodium solid electrolytes with improved interfacial stability with sodium anode.

Inorganic Sodium Solid Electrolytes: Structure Design, Interface Engineering and Application.

All-solid-state sodium batteries (ASSSBs) are particularly attractive for large-scale energy storage and electric vehicles due to their exceptional safety, abundant resource availability, and cost-effectiveness. The growing demand for ASSSBs underscores the significance of sodium solid electrolytes; However, the existed challenges of sodium solid electrolytes hinder their practical application despite continuous research efforts. Herein, recent advancements and the challenges for sodium solid electrolytes from material to battery level are reviewed. The in-depth understanding of their fundamental properties, synthesis techniques, crystal structures and recent breakthroughs is presented. Moreover, critical challenges on inorganic sodium solid electrolytes are emphasized, including the imperative need to enhance ionic conductivity, fortifying interfacial compatibility with anode/cathode materials, and addressing dendrite formation issues. Finally, potential applications of these inorganic sodium solid electrolytes are explored in ASSSBs and emerging battery systems, offering insights into future research directions.

NaF-Rich Multifunctional Layers toward Stable All-Solid-State Sodium Batteries.

NASICON oxide solid electrolytes are considered promising candidates for all-solid-state sodium batteries due to their extremely high ionic conductivity and favorable electrochemical stability. However, the practical application of NASICON electrolytes is greatly impeded by poor electrolyte-electrode interfacial contact and continuous sodium dendrite propagation. Herein, a NaF-rich multifunctional interface layer on the surface of a Na anode (Na@NaF-rich), containing NaF, amorphous carbon, and an unreacted C-F bond species, is developed in situ by the reaction between Na and commercial poly(tetrafluoroethylene). This NaF-rich interface layer is proven to reduce the diffusion barriers at the Na/NASICON electrolyte interface and homogenize Na deposition as well as suppress Na dendrite growth, thus achieving a high critical current density of 4 mA cm-2. The resultant Na3V2(PO4)3@C/Na@NaF-rich all-solid-state cell showed a high initial specific capacity of 117.6 mAh g-1 at 0.1 C with a Coulombic efficiency of 94.8%. Even at 0.5 and 1 C, it still exhibited high capacity retentions of 83.3% and 80.4%, respectively, after 750 cycles.

Embedding alloying sites in a lithiated polymer matrix as a stable interphase of lithium electrodes.

Designing a stable interphase with lithium (Li) dendrite suppressing ability is a surging demand for high-energy-density Li metal batteries (LMBs). Here, a hybrid inorganic-organic interphase is achieved on a Li anode, on which the nanoscale phase separation between antimony nucleation sites and an interconnected Li+ conducting polymer matrix endows the Li growing behavior with high uniformity and stability, resulting in a long lifespan of LMB over 500 cycles with a practical capacity of ∼2.5 mA h cm-2.

Zn-Alloying Sites with Self-Adsorbed Molecular Crowding Layer as a Stable Interfacial Structure of Zn Electrodes.

Rechargeable aqueous zinc (Zn) metal batteries (ZMBs) have gained tremendous attention because of their intrinsic safety and low cost. However, the lifespan of ZMBs is seriously limited by severe Zn dendritic growth in aqueous electrolytes. Despite the feasibility of Zn deposition regulation by introducing Zn-alloying sites at the Zn plating surface, the activity of the Zn-alloying sites can be seriously reduced by side reactions in the aqueous environment. Here, we propose a facile but efficacious strategy to reinforce the activity of the Zn-alloying sites by introducing a low quantity of polar organic additive in the electrolyte that can be self-adsorbed on the Zn-alloying sites to form a molecular crowding layer against the parasitic water reduction during Zn deposition. As a consequence, stable cycling of the Zn anode can be maintained at such a multifunctional interfacial structure, arising from the synergism between the seeded low-overpotential Zn deposition on the stabilized Zn-alloying sites and a Zn2+ redistributing feature of the self-adsorbed molecular crowding layer. The interfacial design principle here can be widely employed due to the great variety of Zn-alloy and polar organic materials and potentially be applied to improve the performance of other aqueous metal batteries.

Achieving Practical High-Energy-Density Lithium-Metal Batteries by a Dual-Anion Regulated Electrolyte.

Lithium-metal batteries (LMBs) using lithium-metal anodes and high-voltage cathodes have been deemed as one of the most promising high-energy-density battery technology. However, its practical application is largely hindered by the notorious dendrite growth of lithium-metal anodes, the fast structure degradation of the cathode, and insufficient electrode-electrolyte interphase kinetics. Here, a dual-anion regulated electrolyte is developed for LMBs using lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and lithium difluoro(bisoxalato)phosphate (LiDFBOP) as anion regulators. The incorporation of TFSI- in the solvation sheath reduces the desolvation energy of Li+ , and DFBOP- promotes the formation of highly ion-conductive and sustainable inorganic-rich interphases on the electrodes. Significantly enhanced performance is demonstrated on Li||LiNi0.83 Co0.11 Mn0.06 O2 pouch cells, with 84.6% capacity retention after 150 cycles in 6.0 Ah pouch cells and an ultrahigh rate capability up to 5 C in 2.0 Ah pouch cells. Furthermore, a pouch cell with an ultralarge capacity of 39.0 Ah is fabricated and achieves an ultrahigh energy density of 521.3 Wh kg-1 . The findings provide a facile electrolyte design strategy for promoting the practical utilization of high-energy-density LMBs.

LiAlO2-Modified Li Negative Electrode with Li10GeP2S12 Electrolytes for Stable All-Solid-State Lithium Batteries.

Lithium (Li) metal has an ultrahigh specific capacity in theory with an extremely negative potential (versus hydrogen), receiving extensive attention as a negative electrode material in batteries. However, the formation of Li dendrites and unstable interfaces due to the direct Li metal reaction with solid sulfide-based electrolytes hinders the application of lithium metal in all-solid-state batteries. In this work, we report the successful fabrication of a LiAlO2 interfacial layer on a Li/Li10GeP2S12 interface through magnetic sputtering. As LiAlO2 can be a good Li+ ion conductor but an electronic insulator, the LiAlO2 interface layer can effectively suppress Li dendrite growth and the severe interface reaction between Li and Li10GeP2S12. The Li@LiAlO2 200 nm/Li10GeP2S12/Li@LiAlO2 200 nm symmetric cell can remain stable for 3000 h at 0.1 mA cm-2 under 0.1 mAh cm-2. Moreover, unlike the rapid capacity decay of a cell with a pristine lithium negative electrode, the Li@LiAlO2 200 nm/Li10GeP2S12/LiCoO2@LiNbO3 cell delivers a reversible capacity of 118 mAh g-1 and a high energy efficiency of 96.6% after 50 cycles. Even at 1.0 C, the cell with the Li@LiAlO2 200 nm electrode can retain 95% of its initial capacity after 800 cycles.

Fluorinated Li10 GeP2 S12 Enables Stable All-Solid-State Lithium Batteries.

The instability of Li10 GeP2 S12 toward moisture and that toward lithium metal are two challenges for the application in all-solid-state lithium batteries. In this work, Li10 GeP2 S12 is fluorinated to form a LiF-coated core-shell solid electrolyte LiF@Li10 GeP2 S12 . Density-functional theory calculations confirm the hydrolysis mechanism of Li10 GeP2 S12 solid electrolyte, including H2 O adsorption on Li atoms of Li10 GeP2 S12 and the subsequent PS4 3- dissociation affected by hydrogen bond. The hydrophobic LiF shell can reduce the adsorption site, thus resulting in superior moisture stability when exposing in 30% relative humidity air. Moreover, with LiF shell, Li10 GeP2 S12 shows one order lower electronic conductivity, which can significantly suppress lithium dendrite growth and reduce the side reaction between Li10 GeP2 S12 and lithium, realizing three times higher critical current density to 3 mA cm-2 . The assembled LiNbO3 @LiCoO2 /LiF@Li10 GeP2 S12 /Li battery exhibits an initial discharge capacity of 101.0 mAh g-1 with a capacity retention of 94.8% after 1000 cycles at 1 C.

Polyimide-Based Solid-State Gel Polymer Electrolyte for Lithium-Oxygen Batteries with a Long-Cycling Life.

Metal-air batteries have attracted wide interest owing to their ultrahigh theoretical energy densities, particularly for lithium-oxygen batteries. One of the challenges inhibiting the practical application of lithium-oxygen batteries is the unavoidable liquid electrolyte evaporation accompanying oxygen fluxion in the semi-open system, which leads to safety issues and poor cyclic performance. To address these issues, we propose a solid-state polyimide based gel polymer electrolyte (PI@GPE), immobilizing and reserving a liquid electrolyte in the gelled polymer substrate. The liquid electrolyte uptake of PI@GPE is measured to be 842%, 6 times higher than that of the commercial glass fiber separator, contributing to a high ionic conductivity of 0.44 mS cm-1. Additionally, PI@GPE possesses an enhanced lithium transference number of 0.596 as well as superior interfacial compatibility with lithium metals. Under 0.1 mA cm-2 and 0.25 mA h cm-2, PI@GPE-based lithium-oxygen batteries demonstrate distinguished long-cycling stability of 366 cycles, 4 times more than that with a glass fiber separator and liquid electrolyte. Our work provides a unique solid-state gel polymer electrolyte to mitigate liquid electrolyte leakage, exhibiting promising potential application in highly safe lithium-oxygen batteries with a long-cycling life.

Toluene Tolerated Li9.88GeP1.96Sb0.04S11.88Cl0.12 Solid Electrolyte toward Ultrathin Membranes for All-Solid-State Lithium Batteries.

Sulfide solid electrolyte membranes employed in all-solid-state lithium batteries generally show high thickness and poor chemical stability, which limit the cell-level energy density and cycle life. In this work, Li9.88GeP1.96Sb0.04S11.88Cl0.12 solid electrolyte is synthesized with Sb, Cl partial substitution of P, S, possessing excellent toluene tolerance and stability to lithium. The formed SbS43- group in Li9.88GeP1.96Sb0.04S11.88Cl0.12 exhibits low adsorption energy and reactivity for toluene molecules, confirmed by first-principles density functional theory calculation. Using toluene as the solvent, ultrathin Li9.88GeP1.96Sb0.04S11.88Cl0.12 membranes with adjustable thicknesses can be well prepared by the wet coating method, and an 8 µm thick membrane exhibits an ionic conductivity of 1.9 mS cm-1 with ultrahigh ionic conductance of 1860 mS and ultralow areal resistance of 0.68 Ω cm-2 at 25 °C. The obtained LiCoO2|Li9.88GeP1.96Sb0.04S11.88Cl0.12 membrane|Li all-solid-state lithium battery shows an initial reversible capacity of 125.6 mAh g-1 with a capacity retention of 86.3% after 250 cycles at 0.1 C under 60 °C.

Highly reversible Li metal anode using a binary alloy interface.

Suppressing lithium (Li) dendrite growth is a central issue for achieving stable Li metal batteries (LMBs). Here, we propose a binary alloy interface that consists of Ag inner nucleation cores and Zn outer diffusion shells through which a Li solubility gradient is created appropriately to enable simultaneous high lithiophilicity and stability. These merits provide the superior cycling stability of the as-generated Li-Ag-Zn electrode compared with the bare Li or Li-Ag counterparts, resulting in the long-term cycling stability of LMBs.

Cellulose Acetate-Based High-Electrolyte-Uptake Gel Polymer Electrolyte for Semi-Solid-State Lithium-Oxygen Batteries with Long-Cycling Stability.

Lithium-oxygen batteries have received great research interest owing to their ultrahigh theoretical energy density and are considered as one of the promising secondary batteries. However, there are still some challenges in their practical application, like liquid organic electrolyte evaporation in the semi-open system and instability in the high-voltage oxidizing environment. In this work, a cellulose acetate-based gel polymer electrolyte (CA@GPE) is proposed, whose cross-linked microporous structure ensures the ultrahigh liquid electrolyte uptake of 2391%. The prepared CA@GPE exhibits a high lithium-ion transference number of 0.595, a satisfying ionic conductivity of 0.47 mS cm-1 and a wide electrochemical stability window up to 5.0 V. The Li//Li symmetric cell employing CA@GPE could cycle stably over 1200 h. The lithium-oxygen battery with CA@GPE presents a superb cycling lifetime of 370 cycles at 0.1 mA cm-2 under 0.25 mAh cm-2 . This work offers a possible strategy to realize long-cycling stability lithium-oxygen batteries.

High-Rate Solid Polymer Electrolyte Based Flexible All-Solid-State Lithium Metal Batteries.

A flexible poly(vinylidene fluoride)-polyetherimide@poly(ethylene glycol) (PVDF-PEI@PEG) solid composite polymer electrolyte is prepared by an in situ thermal curing approach. The homogeneous PVDF-PEI composite porous membrane with an optimized PVDF and PEI weight ratio increases the amorphous phase, while the fast lithium ion transport channels are formed through the filled PEG electrolytes. The optimized polymer electrolyte exhibits high ionic conductivity of 2.36 × 10-4 S cm-1 at 60 °C and lithium ion transference number of 0.578 as well as excellent electrochemical stability window of 5.5 V. Moreover, the superior stability toward lithium metal anode enables over 3600 h cycling of the Li//Li symmetric cell at 0.1 mA cm-2. In particular, the LiFePO4//Li battery delivers high specific capacities of 132.4 and 111.5 mAh g-1 with a retention of 86.6% and 85.9% after 200 cycles at 2 C and 100 cycles at 3 C rate under 60 °C, respectively, demonstrating the feasibility as an energy storage device with high rate capability.

Amorphous Titanium Polysulfide Composites with Electronic/Ionic Conduction Networks for All-Solid-State Lithium Batteries.

All-solid-state lithium/sulfide batteries are considered as next-generation high-energy-density batteries with unrivaled safety. However, sulfide cathodes generally suffer from insulating properties and huge volume expansion in all-solid-state lithium batteries. Based on amorphous TiS4 (a-TiS4), a certain proportion of Super P is introduced to suppress the volume expansion and increase the electronic conductivity. Meanwhile, a Li7P3S11 solid electrolyte is in situ coated on the surface of 20% Super P/a-TiS4, and the close interfacial contact between the active material and the solid electrolyte constructs a favorable ionic conduction path. As a result, a Li/75% Li2S-24% P2S5-1% P2O5/Li10GeP2S12/20% Super P/a-TiS4@Li7P3S11 battery shows a high reversible capacity of 507.4 mAh g-1 after 100 cycles at 0.1 A g-1. Even the current density increases to 1.0 A g-1, and it can also provide a reversible capacity of 349.8 mAh g-1 after 200 cycles. These results demonstrate a promising 20% Super P/a-TiS4@Li7P3S11 cathode material with electronic/ionic conduction networks for all-solid-state lithium batteries.

Quasi-Ionic Liquid Enabling Single-Phase Poly(vinylidene fluoride)-Based Polymer Electrolytes for Solid-State LiNi0.6 Co0.2 Mn0.2 O2 ||Li Batteries with Rigid-Flexible Coupling Interphase.

Poly(vinylidene fluoride)-based polymer electrolytes are being intensely investigated for solid-state lithium metal batteries. However, phase separation and porous structures are still pronounced issues in traditional preparing procedure. Herein, a bottom-to-up strategy is employed to design single-phase and densified polymer electrolytes via incorporating quasi-ionic liquid with poly(vinylidene fluoride-co-hexafluoropropylene). Due to strong ion/dipole-dipole interaction, the optimized polymer electrolyte delivers high room-temperature ionic conductivity of 1.55 × 10-3 S cm-1 , superior thermal and oxidation stability of 4.97 V, excellent stretchability of over 1500% and toughness of 43 MJ cm-3 as well as desirable self-extinguishing ability. Furthermore, the superb compatibility toward Li anode enables over 3000 h cycling of Li plating/stripping and ≈98% Coulombic efficiency in Li||Cu test at 0.1 mA cm-2 . In particular, lithium metal battery Li||LiNi0.6 Co0.2 Mn0.2 O2 exhibits a room-temperature discharge retention rate of 96% after 500 cycles under a rate of 0.1 C, which is associated with the rigid-flexible coupling electrodes/electrolytes interphase. This investigation demonstrates the potential application of quasi-ionic liquid/polymer electrolytes in safe lithium metal batteries.

In Situ Formed Li-Ag Alloy Interface Enables Li10GeP2S12-Based All-Solid-State Lithium Batteries.

All-solid-state lithium-metal batteries (ASSLMBs) have received great interest due to their high potential to display both high energy density and safety performance. However, the poor compatibility at the Li/solid electrolyte (SE) interface and penetration of lithium dendrites during cycling strongly impede their successful commercialization. Herein, a thin Ag layer was introduced between Li and Li10GeP2S12 for the in situ formation of a Li-Ag alloy interface, thus tuning the interfacial chemistry and lithium deposition/dissolution behavior. Superior electrochemical properties and improved interfacial stability were achieved by optimizing the Ag thicknesses. The assembled symmetric cell with Li@Ag 1 µm showed a steady voltage evolution up to 1000 h with an areal capacity of 1 mAh cm-2. Moreover, a high reversible capacity of 106.5 mAh g-1 was achieved in an all-solid-state cell after 100 cycles, demonstrating the validity of the Ag layer. This work highlights the importance of the Li/SE interface re-engineering and provides a new strategy for improving the cycle life of ASSLMBs.