Garnet-type Li7La3Zr2O12 Research Articles

Dual influence of protonation on Li-ion transport in garnet solid electrolytes: A first-principles study

Garnet-type cubic Al-doped Li7La3Zr2O12 (LLZO) is a promising solid electrolyte for all-solid-state Li-ion batteries because of its excellent ionic conductivity and stability against Li metal. However, its sensitivity against moisture poses a significant challenge, as LLZO undergoes protonation upon exposure to water, which has been experimentally observed to reduce Li-ion conductivity. Despite this, the exact impact of protonation-induced structural changes and the role of protons in Li-ion transport within LLZO remain unclear. A thorough understanding of these mechanisms is crucial for enhancing the performance of LLZO as a solid electrolyte. In this study, we employed density functional theory (DFT) and DFT-based molecular dynamics (DFT-MD) simulations to investigate the effect of protonation on the structure, Li-ion transport, and proton dynamics in LLZO. Our results demonstrate that protonation induces a phase transition from the centrosymmetric Ia3‾d to a distorted non-centrosymmetric I4‾3d symmetry, concomitantly reducing the Li-ion conductivity, consistent with experimental observations. Furthermore, we identify two competing effects of protonation on Li-ion transport: protons tend to occupy octahedral sites, which trap Li-ions in more stable tetrahedral sites, thereby impeding their mobility. Conversely, proton insertion enlarges the bottlenecks along Li-ion diffusion pathways from a range of 1.78–1.90 Å to 1.80–1.92 Å, potentially lowering the diffusion barrier for Li transport. Therefore, protonation introduces both inhibitory and facilitating factors for Li-ion transport. Additionally, the reduction in Li-ion concentration due to protonation further diminishes the overall ionic conductivity of LLZO.

Tailored Design of a Nanoporous Structure Suitable for Thick Si Electrodes on a Stiff Oxide-Based Solid Electrolyte.

Oxide-based all-solid-state batteries are ideal next-generation batteries that combine high energy density and high safety, but their realization requires the development of interface bonding technology between the stiff solid electrolyte and electrode. Even if the interface could be bonded, it is difficult to hold the interface, because only the electrode expands/contracts unilaterally during charge/discharge reactions. In particular, silicon (Si), which has eagerly awaited as a next-generation negative-electrode material for many years, changes in volume by several hundred percent. To solve these problems, in this work, highly porous silicon oxide (SiOx) electrodes with different porous structures were fabricated on a stiff garnet-type Li7La3Zr2O12 solid electrolyte, the three-dimensional nanoporous structure was analyzed quantitatively, and the charge/discharge characteristics were investigated. The microscopic observation and electrochemical analysis revealed how we should control the porous structure, such as sizes of pores and SiOx, size distribution, and porosity, for repeated and stable charge/discharge cycles. In addition, the resultant porous SiOx electrodes demonstrated superior charge/discharge cycle performance even when it thickened to 5 μm, whereas non-porous SiOx easily peeled off from the solid electrolyte when its thickness exceeded 0.1 μm. The thick SiOx films greatly improved the energy density per unit area (mAh cm-2). Nanosized fine pores with an interconnected open-pore architecture effectively mitigated the internal and interfacial stress upon expansion (charge)/contraction (discharge) of Si, and as a result, the thick and porous SiOx electrode maintained the interfacial joint with the stiff solid electrolyte after repeated charge/discharge cycles. These results will provide useful insights for effectively designing more practical porous SiOx powder effectively.

A single-ion transport interfacial layer for solid-state lithium batteries

All-solid-state batteries possess several advantages including high safety, flexibility to use high-capacity metal anodes and are projected to be the next generation energy storage devices. Garnet-type cubic Li7La3Zr2O12 (LLZO) solid electrolyte is of particular interest due to its high ionic conductivity under ambient conditions and compatibility with Li metal. However, large electrode/electrolyte interfacial resistance constraints their development. Herein, the use of a highly lithium ion conducting dilithium phthalocyanine (Li2Pc) in ionic liquid as an interlayer is proposed to effectively suppress the high impedance at the interface thus improving the electrode-electrolyte contact. Fast Li+ mobility and high dielectric constant of dilithium phthalocyanine enhance the kinetics of Li+ transport across the interface. A significant reduction in overpotential and very stable stripping/plating cycling are observed in lithium symmetric cells upon introducing Li2Pc interlayer as compared to the use of bare tantalum doped lithium lanthanum zirconium oxide (LLZTO) electrolyte. Cells comprising interlayer-modified Li|LLZTO|LiFePO4 show high capacity with excellent cycling and rate capability. The performance of full cells using lithiated graphite and lithium titanate anodes has also been evaluated. This study presents a promising application of garnet electrolytes towards the advancement of solid-state lithium batteries.

Enhanced electrochemical performance of garnet Li7La3Zr2O12 electrolyte by efficient incorporation of LiCl

Garnet-type Ta-doped Li7La3Zr2O12 (LLZO) lithium-ion-conducting ceramic electrolytes has become the promising and critical candidate for developing the high-energy-density all-solid-state lithium batteries, due to the satisfied Li+ conductivity, stability against metallic lithium anode, and the feasible preparation under ambient air. Here, to further increase the lithium-ion conductivity of LLZO comparable to that of the commercial organic liquid electrolytes, lithium chloride (LiCl) is effectively introduced to synthesize the garnet-type ceramic electrolytes with the nominal composition (Li6.5La3Zr1.5Ta0.5O12)1-x–(LiCl)x (x = 0, 5mol%, 10mol%, 15mol%, 20mol%, and 25mol%) via high-temperature calcination process. The cubic structure with highly conductive performance is confirmed from X-ray diffraction measurement as well as Raman spectra analysis. Structural information is observed according to field emission scanning electron microscope equipped with energy dispersive spectrometer and density measurements. Among above investigated ceramic compositions, the prepared (Li6.5La3Zr1.5Ta0.5O12)0.85–(LiCl)0.15 ceramic electrolyte sheet sintered at 1200 °C for 12h presents the room-temperature Li-ion conductivity of 1.22 × 10−3 S·cm−1 by alternating current (AC) impedance analysis along with the corresponding activation energy of 0.262eV through Arrhenius equation calculation. The electronic conductivity measurements are also done by direct-current polarization to confirm the ionic nature for all investigated ceramics. Furthermore, the Li|(Li6.5La3Zr1.5Ta0.5O12)0.85–(LiCl)0.15 |Li symmetric batteries can possess the small interfacial resistance of 92.3 Ω cm2 and stably run for 1000 h at 0.1 mA cm−2 without a short circuit at room temperature. The hybridized lithium-sulfur battery with (Li6.5La3Zr1.5Ta0.5O12)0.85–(LiCl)0.15 electrolyte delivered excellent initial room-temperature discharge capacity of 1204mAh·g−1 and 1152 mAh·g−1 under the current density of 0.1C and 0.2C respectively, large coulombic efficiency, and great cycling stability. Moreover, the lithium-sulfur batteries also can show excellent cycling performances under different current densities and a good capacity recoverability. The above investigation results suggest that the low-melting-point LiCl incorporation in Li6.5La3Zr1.5Ta0.5O12 electrolyte is an effective measurement to synthesize the cubic and dense Li-stuff garnet ceramic sheets for the high-performance rechargeable next-generation solid-state batteries.

A Simple Method for the Study of Heteroionic Interface Impedances in Solid Electrolyte Multilayer Cells Containing LLZO.

Hybrid battery cells that combine a garnet-type Li7La3Zr2O12 (LLZO) solid electrolyte with other solid, polymer or liquid electrolytes are increasingly investigated. In such cells with layered electrolytes, ensuring a low-resistive heteroionic interface between neighboring electrolytes is crucial for preventing major additional overpotentials during operation. Electrochemical impedance spectroscopy is frequently used to extract such parameters, usually on multilayer symmetrical model cells that contain the different electrolytes stacked in series. Unfortunately, the impedance contributions of the heteroionic interfaces often overlap with those of the electrolyte|electrode interfaces, necessitating the use of sophisticated four-point cells that probe the electrochemical potential away from the polarization source. In this work, an alternative solution to this problem is demonstrated by taking advantage of the inherent fast charge transfer kinetics of LLZO with its parent metal electrode. The "resistance-free" nature of a reversible Li|LLZO interface enables a precise evaluation of the heteroionic interface impedance in symmetric two-point cells of the type Li|LLZO|electrolyte|LLZO|Li with negligible electrode contribution. This is exemplified for symmetric multilayer cells containing tantalum-doped LLZO and a poly(ethylene oxide) (PEO)-based dry polymer electrolyte. Validation and comparison of impedance data with results from symmetric four-point cells and two-point cells with ion-blocking electrodes demonstrate the advantage of the proposed method. Overall, this study presents a simple and reliable method for studying heteroionic interface impedances in LLZO-containing multilayer cells.

Universal-neural-network-potential molecular dynamics for lithium metal and garnet-type solid electrolyte interface

All-solid-state Li-metal batteries can conceivably improve the safety and extend the driving ranges of electric vehicles. In this regard, the garnet-type solid electrolyte Li7La3Zr2O12 (LLZ) has garnered considerable attention because of its high Li-ion conductivity and nonreactivity towards molten Li metal. Here, we perform molecular dynamics (MD) simulations using a universal neural network potential (UNNP) to analyse the Li-ion exchange at the LLZ/Li interface at the atomic scale. The UNNP-MD calculations show that Li ions traverse the LLZ/Li interface and that excess Li ions relative to the stoichiometric composition accumulate in an approximately 1 nm-thick zone near the LLZ phase interface, signifying the formation of a space-charge layer. Electronic structural analysis of the UNNP-MD-derived configuration, performed using density functional theory calculations, reveals band bending near the LLZ phase interface and the simultaneous suppression of Li metal reduction. These findings can help expedite the development of rationally designed all-solid-state Li-metal batteries.

Tailoring Solid-State Battery Performance through Computationally Tuning the Composition of LLZO-LCO Composite Cathodes

The composite cathode consisting of garnet-type solid-electrolyte Li7La3Zr2O12 (LLZO) and active material LiCoO2 (LCO) is one of the most promising solutions for the cathode design of all-solid-state lithium batteries. The transport properties of Li within the LLZO-LCO composite cathode are known to be sensitively dependent on the composition and microstructural features. This study focuses on computationally refining the performance of solid-state batteries by modifying the porosity and volume fractions of the LLZO-LCO composite cathode while considering the variations in the microstructural features. Various 2D and 3D microstructures were synthesized using a stochastic stacking particle model and the corresponding effective diffusivity of Li is calculated using a numerical homogenization method, which allows for a systematic assessment of the impact of composition on lithium transport within the microstructure. By identifying the optimal ratio between LLZO and LCO phases and porosity, this research yields crucial insights for improving the performance of solid-state batteries by tailoring the composite cathode.Figure 1: A) An example 3-dimensional microstructure with 20.3% percent vacuum (white space) and 39.25% percent LCO (yellow) and 40.45% LLZO (orange). B) The highest effective diffusivity (purple) is found when the LLZO percentage is highest. Once the vacuum percentage is 30% or higher, minimal effective diffusivity (red) is observed.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Figure 1

Microwave-assisted solvothermal synthesis of nanostructured Ga-Doped Li7La3Zr2O12 solid electrolyte with enhanced densification and Li-ion conductivity

Garnet-type Li7La3Zr2O12 (LLZO) Li-ion solid electrolytes are promising candidates for safe, next-generation solid-state batteries. In this study, we synthesize Ga-doped LLZO (Ga–LLZO) electrolytes using a microwave-assisted solvothermal method followed by low-temperature heat treatment. The nanostructured precursor (<50 nm) produced by the microwave-assisted solvothermal process has a high surface energy, facilitating the reaction for preparing garnet-type Ga–LLZO powders (<800 nm) within a short time (<5 h) at a low calcination temperature (<700 °C). Additionally, the calcined nanostructured Ga–LLZO powder can be sintered to produce a high-density pellet with minimized grain boundaries under moderate sintering conditions (temperature: 1150 °C, duration: 10 h). The optimal doping concentration was determined to be 0.4 mol% Ga, which resulted significantly increased the ionic conductivity (1.04 × 10−3 S cm−1 at 25 °C) and stabilized the cycling performance over 1700 h at 0.4 mA cm−2. This approach demonstrates the potential to synthesize oxide-type solid electrolyte materials with improved properties for solid-state batteries.

Holistic view on cation interdiffusion during processing and operation of garnet all-solid-state batteries

All-solid-state batteries based on the active cathode material LiCoO2 (LCO), a garnet-type Li7La3Zr2O12 (LLZO) electrolyte and a Li-metal anode are attracting a lot of attention as a robust and safe alternative to conventional lithium-ion batteries. The challenges in the practical realization of such cells are related to high-temperature sintering, which compacts the ceramic powder but also leads to undesirable material interactions such as cation interdiffusion and secondary phase formation. Even if high initial capacities can be achieved, the all-inorganic cells suffer from a strong capacity drop due to various degradation phenomena during processing and operation, which are not yet fully understood. In this study, the thermodynamic and kinetic aspects of co-sintering as well as the structural evolution of materials and interfaces during processing and operation of co-sintered LCO-LLZO cathodes are investigated in detail. A thermodynamic model for the interdiffusion of cations is derived and the effects of the diffusion of Al- and Co-ions, which occurs during the processing and cycling of the cells, are investigated. In LLZO, the diffusion of 0.13 Co per formula unit (pfu) has a negligible effect on ionic and electronic conductivity and electrochemical stability. In contrast, the substitution of 0.01 pfu Al and the induced disorder in the layer structure of LCO increases the polarization during cycling. All-inorganic cells fabricated with optimized sintering parameters to minimize interdiffusion between LCO and LLZO show good initial performance but similar degradation during cycling, as the used processing parameters result in a more porous microstructure leading to the development of cracks along the LLZO/LCO interface. The results obtained highlight the inherent instabilities of all-ceramic cathodes with unprotected LCO/LLZO interfaces, which require precise tuning of materials and processing parameters to achieve both high mechanical stability and low interdiffusion.

Unlocking high-energy solid-state lithium-sulfur batteries with an innovative double-layer hybrid solid electrolyte

This study developed a novel double-layer hybrid solid electrolyte (DLHSE) to address the limitations of solid-state lithium–sulfur (Li–S) batteries, which include poor electronic/ionic conductivity, interfacial chemical/electrochemical instability, and substantial interfacial resistance between the solid electrolyte and electrodes. The DLHSE comprises an ion-conducting ceramic, electrochemically stable polymer, and ether-based liquid electrolyte. Specifically, the dual-layer ceramic skeleton comprises an inorganic NASICON-type Li1+xAlxTi2-x(PO4)3 (LATP) layer facing the cathode to facilitate Li+ migration at the interface and a garnet-type Li7La3Zr2O12 (LLZO) layer facing the anode to suppress Li dendrite formation and mitigate the “shuttle effect”. The polymer binder (PVDF–TrFE) can create a three-dimensional network to enhance structural compactness and stability. The penetrating ether-based electrolyte can facilitate Li+ transfer and reinforce the interfacial contact. Furthermore, a well-designed porous carbon rod/sulfur (PCR/S) composite with an ultrahigh sulfur content of 80 wt% was prepared as the cathode. Consequently, the novel structural configuration with PCR/S cathode and DLHSE, not only demonstrated excellent coin-cell performance with a capacity retention of 802 mAh g−1 after 500 cycles at 0.2C, but also an outstanding A-h-level pouch cell with an impressive discharge capacity of 7 Ah at 0.1C.

Investigation of Li accumulations in LLZO based solid state batteries via operando neutron imaging and ex-situ correlative structural and chemical analysis

In this study, we present a comprehensive analysis of lithium dendrite formation in half-cells with lithium garnet-type solid-state electrolyte Li7La3Zr2O12 (LLZO) utilizing operando neutron imaging and subsequent ex-situ correlative structural and chemical analysis. The operando experiment involves cycling a solid-state symmetric half-cell (Li|LLZO|Li) until short-circuit failure, all while being irradiated with neutrons, providing invaluable insights into the dynamic processes within the symmetric half-cell. Post-mortem investigations were carried out, comprising two techniques: 1) secondary electron imaging for structural analysis and 2) secondary ion mass spectrometry (SIMS) for chemical mapping. This multifaceted approach creates complementary datasets, bridging the gap between neutron radiography, known for its quantitative transmission capabilities, and high-resolution, high-sensitivity structural and chemical imaging via scanning electron microscopy (SEM) and SIMS.Central to our investigation is the design and development of an operando neutron imaging approach, enabling the study of lithium penetration during the electrochemical cycling. Furthermore, structural, and chemical analyses through correlative SEM/SIMS unveil various morphologies of lithium accumulations. Specifically, regions with dense LLZO reveal intergranular lithium accumulations, while low-density areas within the LLZO pellet, such as pores and cracks, exhibit distinct types of lithium accumulations (e.g. whiskers).Notably, neutron analysis reveals an accumulation of lithium in selected regions, with a maximum increase of up to 3.6 vol.-%. These regions primarily correspond to the roughened LLZO/Li interface, as observed through neutron imaging, although the SEM/SIMS analysis unequivocally confirms the presence of lithium dendrites (with sizes at or below the resolution limit of neutron imaging) also within the bulk of LLZO.This work offers a comprehensive examination of the intricate dynamics of lithium dendrite formation and behaviour in LLZO-based solid-state half-cells, emphasizing the potential of operando techniques to advance our understanding of critical issues (e.g. degradation, dendrite formation, …) in battery research.

Dynamic lithium-compensation mechanism for densification of garnet-type Li7La3Zr2O12 electrolyte by Li2O atmosphere buffer pair

Dynamic lithium-compensation mechanism for densification of garnet-type Li7La3Zr2O12 electrolyte by Li2O atmosphere buffer pair

In-situ Li2O-atmosphere assisted solvent-free route to produce highly conductive Li7La3Zr2O12 solid electrolyte

Solid-state batteries have garnered attention due to their potentiality for increasing energy density and enhanced safety. One of the most promising solid electrolytes is garnet-type Li7La3Zr2O12 (LLZO) ceramic electrolyte because of its high conductivity and ease of manufacture in ambient air. The complex gas-liquid-solid sintering mechanism makes it difficult to prepare LLZO with excellent performance and high consistency. In this study, an in-situ Li2O-atmosphere assisted solvent-free route is developed for producing the LLZO ceramics. First, the lithium-rich additive Li6Zr2O7 (LiZO) is applied to in-situ supply Li2O atmosphere at grain boundaries, where its decomposition products (Li2ZrO3) build the bridge between the grain boundaries. Second, comparisons were studied between the effects of dry and wet routes on the crystallinity, surface contamination, and particle size of calcined powders and sintered ceramics. Third, by analyzing the grain boundary composition and the evolution of ceramic microstructure, the impacts of dry and wet routes and lithium-rich additive LiZO on the ceramic sintering process were studied in detail to elucidate the sintering behavior and mechanism. Lastly, exemplary Nb-doped LLZO pellets with 2 wt% LiZO additives sintered at 1,300 °C × 1 min deliver Li+ conductivities of 8.39 × 10-4 S cm-1 at 25 °C, relative densities of 96.8%, and ultra-high consistency. It is believed that our route sheds light on preparing high-performance LLZO ceramics for solid-state batteries.

Li5AlO4-Assisted Low-Temperature Sintering of Dense Li7La3Zr2O12 Solid Electrolyte with High Critical Current Density.

In recent years, solid electrolytes (SEs) have been developed a lot due to the superior safety of solid-state batteries (SSBs) upon liquid electrolyte-based commercial batteries. Among them, garnet-type Li7La3Zr2O12 (LLZO) is one of the few SEs that is stable to lithium anode with high Li+ conductivity and the feasibility of preparation under ambient air, which makes it a promising candidate for fabricating SSBs. However, high sintering temperature (>1200 °C) prevents its large-scale production, further hindering its application. In this work, the Li5AlO4 sintering aid is proposed to decrease the sintering temperature and modify the grain boundaries of LLZO ceramics. Li5AlO4 generates in situ Li2O atmosphere and molten Li-Al-O compounds at relatively low temperatures to facilitate the gas-liquid-solid material transportation among raw LLZO grains, which decreases the densification temperature over 150 °C and strengthens the grain boundaries against lithium dendrites. As an example, Ta-doped LLZO ceramics without excessive Li sintered with 2 wt % Li5AlO4 at 1050 °C delivered high relative density > 94%, an ionic conductivity of 6.7 × 10-4 S cm-1, and an excellent critical current density (CCD) of 1.5 mA cm-2 at room temperature. In comparison, Ta-doped LLZO with 15% excessive Li sintered at 1200 °C delivered low relative density < 89%, a low ionic conductivity of ∼2 × 10-4 S cm-1, and a poor CCD of 0.5 mA cm-2. Li symmetric cells and Li-LFP full cells fabricated with Li5AlO4-assised ceramics were stably cycled at 0.2 mA cm-2 over 2000 h and at 0.8C over 100 cycles, respectively.

Construction of an intimately riveted Li/garnet interface with ultra-low interfacial resistance for solid-state batteries

An intimately riveted Li/garnet interface, where Li4.4Si particles strongly bond with garnet, is constructed for dendrite-free solid-state lithium batteries.

Proton conductivity of Li+–H+ exchanged Li7La3Zr2O12 dense membranes prepared by molten long-chain saturated fatty acids

Alkali-proton exchange throughout ceramic dense bodies becomes possible using molten long-chain saturated fatty acids. As a case study, 91% Li+–H+ exchange of Al-doped cubic garnet-type Li7La3Zr2O12 dense membranes was demonstrated in this work.

Improvement of Ionic Conductivity in Li7La3Zr2O12 (LLZO) Solid Electrolyte By Doping with Aluminum/Tungsten

Recently, there has been increasing interest in solid electrolytes, which are the most important materials in all-solid-state lithium-ion batteries. Among all solid electrolytes, garnet-type Li7La3Zr2O12 (LLZO) has been proven to be one of the most promising electrolytes due to its high Li+ conductivity, wide potential window, and electrochemical stability towards metallic lithium anode. In particular, cubic garnet-type LLZO solid electrolytes have received a lot of attention for the development of high-performance all-solid-state batteries with safety, energy density, and long cycle life. In this study, we synthesized LLZO solid electrolyte powders with garnet structure and determined the optimal composition and sintering temperature by adding Al/W to form a stable cubic phase.In this study, Al or W-doped LLZO were prepared by a post-doping method. In this process, LLZO powder was first prepared, and then mixed with Al2O3 or WO3 powders to produce doped LLZO ceramic electrolytes, respectively. During this process, the doped ions entered the LLZO lattice, increasing the lithium ion transport channels and promoting lithium ion conductivity. The sintering time, crucible, and sintering temperature were adjusted to investigate the optimal process conditions of the post-doping method. As a result, the doped solid electrolyte exhibited high lithium ion conductivity and low activation energy. Using the high lithium ion conductivity and broad electrochemical stability window of the Al or W doped LLZO SSE, the (NCM622)/(Al or W doped-LLZO) cell delivered a steady cycle for 100 cycles at 0.1C. The Al or W doped-LLZO prepared in this study showed advantages of high conductivity, simple preparation process, high reproducibility, and low cost, which provides technical support and reference for further application of garnet-type SSEs in solid-state batteries with high energy density.

Electro-chemo-mechanical failure of solid-state electrolyte caused from intergranular or transgranular damage propagation in polycrystalline aggregates

Electro-chemo-mechanical failure of solid-state electrolytes (SEs) caused by the internal growth of lithium dendrites significantly impedes the application of solid-state batteries under high applied current density. The grain boundary is usually the key to the mechanical properties of polycrystalline ceramic SEs. Here, strength and width of grain boundary in SEs that are exampled by garnet-type Li7La3Zr2O12 are evaluated under the deposition of lithium by visualizing the stress field, damage accumulation and crack propagation. The enhancement of grain boundary strength triggers a dramatic increase stress when the ratio of tensile strength between grain boundary and grain (λ) is lower than 0.9. With the variation of λ, three damage processes are revealed as intergranular-damage, inter/transgranular-damage and transgranular-damage, leading to different propagation of cracks and the transformation of intergranular failure to transgranular failure. Furthermore, the width of the grain boundary is found to induce more transgranular-damage with its widening. A critical value of grain boundary width for the formation of displacement is obtained under various strengths, as δ = 21 nm for λ = 0.2, δ = 25 nm for λ = 0.5 and δ = 31 nm for λ = 0.9. The findings in this work indicate the coupling effect of grain boundary width and strength on the failure of SEs, providing an insightful perspective for the future design of solid-state batteries.

Viability of all-solid-state lithium metal battery coupled with oxide solid-state electrolyte and high-capacity cathode

Owing to the utilization of lithium metal as anode with the ultrahigh theoretical capacity density of 3860 mA h g−1 and oxide-based ceramic solid-state electrolytes (SE), e.g., garnet-type Li7La3Zr2O12 (LLZO), all-state-state lithium metal batteries (ASLMBs) have been widely accepted as the promising alternatives for providing the satisfactory energy density and safety. However, its applications are still challenged by plenty of technical and scientific issues. In this contribution, the co-sintering temperature at 500 °C is proved as a compromise method to fabricate the composite cathode with structural integrity and declined capacity fading of LiNi0.5Co0.2Mn0.3O2 (NCM). On the other hand, it tends to form weaker grain boundary (GB) inside polycrystalline LLZO at inadequate sintering temperature for LLZO, which can induce the intergranular failure of SE during the growth of Li filament inside the unavoidable defect on the interface of SE. Therefore, increasing the strength of GB, refining the grain to 0.4 μm, and precluding the interfacial defect are suggested to postpone the electro-chemo-mechanical failure of SE with weak GB. Moreover, the advanced sintering techniques to lower the co-sintering temperature for both NCM-LLZO composite cathode and LLZO SE can be posted out to realize the viability of state-of-the-art ASLMBs with higher energy density as well as the guaranteed safety.

Effect of Li2O–B2O3–SiO2 glass on Li+ diffusion and dendrite resistance of Li6.1Ga0.3La3Zr2O12 solid-state electrolyte

Garnet-type Li7La3Zr2O12 is currently being extensively studied as a potential candidate to replace the conventional liquid electrolytes due to prominent ionic conductivity and structural stability. The microstructure is the one of the important factor to obtain the electrochemical performances, resulting from Li-ion kinetics, local current density. Herein, we synthesize the Li6.1Ga0.3La3Zr2O12 with various Li2O–B2O3–SiO2 concentration (1, 3, 5, and 10 wt%) as a glass additive and investigate the effect on the crystallization, relative density, lithium ion conductivity and critical current density. Our findings reveal that proper amount of Li2O–B2O3–SiO2 could enhance the sinterability, thus enabling facile and continuous lithium ion conduction with suppressing propagation of Li dendrite through the pores. Therefore, it can be concluded that appropriate concentration of Li2O–B2O3–SiO2 can be regarded as a breakthrough to construct better solid electrolyte for all-solid-state lithium ion batteries.