Large Interfacial Resistance Research Articles

Enhanced thermoelectric performance and mechanical strength of n-type BiTeSe materials produced via a composite strategy

Zone-melted Bi2Te2.7Se0.3 (ZM BTS) alloys are typical n-type commercial thermoelectric (TE) materials and are utilized for refrigeration and power generation near room temperature. They usually suffer from poor mechanical performance, as well as having a low figure of merit (ZT). In this work, we report an effective composite strategy to improve both the TE and mechanical performance of n-type BTS materials by incorporating carbon microfibers. The introduction of carbon microfibers in BTS effectively reduces the lattice thermal conductivity due to phonon scattering at multi-scale boundaries and due to the large interfacial thermal resistance arising from phonon mismatch between the constituent phases. Simultaneously, it also gives rise to an enhancement of the electrical conductivity, which originates from the increased carrier density without significant limitation on its weighted mobility. Consequently, a high peak ZT of 1.1 at 400 K and an average ZTave value of 0.95 are achieved in the temperature range 300 ~ 550 K, yielding a calculated efficiency of η = 9%. Moreover, the BTS/carbon microfiber composites show superior compressive strength compared to a commercial ZM BTS sample. This improved strength is highly desirable for real-world TE applications. Our results demonstrate a novel way to produce high-performance TE materials, in which interfaces with large thermal resistance are used to achieve low thermal conductivity without significantly degrading the electrical properties of the materials.

Transport Properties of Flexible Composite Electrolytes Composed of Li1.5Al0.5Ti1.5(PO4)3 and a Poly(vinylidene fluoride-co-hexafluoropropylene) Gel Containing a Highly Concentrated Li[N(SO2CF3)2]/Sulfolane Electrolyte.

Flexible solid-state electrolyte membranes are beneficial for feasible construction of solid-state batteries. In this study, a flexible composite electrolyte was prepared by combining a Li+-ion-conducting solid electrolyte Li1.5Al0.5Ti1.5(PO4)3 (LATP) and a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP) gel containing a highly concentrated electrolyte of Li[N(SO2CF3)2] (LiTFSA)/sulfolane using a solution casting method. We successfully demonstrated the operation of Li/LiCoO2 cells with the composite electrolyte; however, the rate capability of the cell degraded with increasing LATP content. We investigated the Li-ion transport properties of the composite electrolyte and found that the gel formed a continuous phase in the composite electrolyte and Li-ion conduction mainly occurred in the gel phase. Solid-state 6Li magic-angle spinning NMR measurements for LATP treated with the 6LiTFSA/sulfolane electrolyte suggested that the Li+-ion exchange occurred at the interface between LATP and 6LiTFSA/sulfolane. However, the kinetics of Li+ transfer at the interface between LATP and the PVDF–HFP gel was relatively slow. The interfacial resistance of LATP/gel was evaluated to be 67 Ω·cm2 at 30 °C, and the activation energy for interfacial Li+ transfer was 39 kJ mol–1. The large interfacial resistance caused the less contribution of LATP particles to the Li-ion conduction in the composite electrolyte.

Designing Polymer-in-Salt Electrolyte and Fully Infiltrated 3D Electrode for Integrated Solid-State Lithium Batteries.

Solid-state lithium batteries (SSLBs) are promising owing to enhanced safety and high energy density but plagued by the relatively low ionic conductivity of solid-state electrolytes and large electrolyte-electrode interfacial resistance. Herein, we design a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based polymer-in-salt solid electrolyte (PISSE) with high room-temperature ionic conductivity (1.24×10-4 S cm-1 ) and construct a model integrated TiO2 /Li SSLB with 3D fully infiltration of solid electrolyte. With forming aggregated ion clusters, unique ionic channels are generated in the PISSE, providing much faster Li+ transport than common polymer electrolytes. The integrated device achieves maximized interfacial contact and electrochemical and mechanical stability, with performance close to liquid electrolyte. A pouch cell made of 2 SSLB units in series shows high voltage plateau (3.7 V) and volumetric energy density comparable to many commercial thin-film batteries.

Intrinsic low sodium/NASICON interfacial resistance paving the way for room temperature sodium-metal battery

Sodium-metal batteries have strong potential to be utilized as stationary high energy density storage devices. Owing to its high ionic conductivity, low electronic conductivity and relatively easy fabrication, NASICON-structure electrolyte (Na3Zr2Si2PO12) is one of the potential candidates to be considered in the solid-state sodium-metal batteries at room temperature. However, the large interfacial resistance between the solid-state electrolyte and the metallic sodium is known to limit the critical current density (CCD) of the cell. In this study, a simple and cost-effective annealing process is introduced to the electrolyte preparation to improves its interface with metallic sodium. X-ray photoelectron spectroscopy and scanning probe microscopy show that Si forms bonds with the surface functional groups when exposed to the ambient condition. With the removal of surface contamination as well as a partially reduced electrolyte surface, the annealed electrolyte shows an extremely small interfacial resistance of 11 Ω cm2 and a high CCD of 0.9 mA cm−2. This study provides an insight on the electrolyte surface preparation and its significant in a sodium-metal solid-state battery.

Origin of High Interfacial Resistance in Solid‐State Batteries: LLTO/LCO Half‐Cells**

AbstractThe interface between cathode and electrolyte is a significant source of large interfacial resistance in solid‐state batteries (SSBs). Spark plasma sintering (SPS) allows densifying electrolyte and electrodes in one step, which can improve the interfacial contact in SSBs and significantly shorten the processing time. In this work, we proposed a two‐step joining process to prepare cathode (LiCoO2, LCO)/electrolyte (Li0.33La0.57TiO3, LLTO) half cells via SPS. Interdiffusion between Ti4+/Co3+ was observed at the interface by SEM/STEM, resulting in the formation of the Li−Ti−La−Co−O and Li−Ti−Co−O phases in LLTO and the Li−Co−Ti−O phase in LCO. Computational modeling was performed to verify that the Li−Ti−Co−O phase has a LiTi2O4 host lattice. In a study of interfacial electrical properties, the resistance of this interdiffusion layer was found to be 105 Ω, which is 40 times higher than the resistance of the individual LLTO phase. The formation of an interdiffusion layer is identified as the origin of the high interface resistance in the LLTO/LCO half‐cell.

Interfacial engineering of lithium‐polymer batteries with in situ UV cross‐linking

AbstractDeveloping promising solid‐state Li batteries with capabilities of high current densities have been a major challenge partly due to large interfacial resistance across the electrode/electrolyte interfaces. This work represents an integrated network of self‐standing polymer electrolyte and active electrode materials with in situ UV cross‐linking. This method provides a uniform morphology of composite polymer electrolyte with low thickness of 20–40 μm. This modification leads to promising cycling results with 85% specific capacity retention in Li||LiFePO4 cell over 100 cycles at high current densities of 170 mA g−1 (~25 μA cm−2, 1 C). By applying this method, the interfacial resistance decreases as high as seven folds compared to noncross‐linked interfaces. The following work introduce a facile and cost‐effective method in developing fast‐charging self‐standing polymer batteries with enhanced electrochemical properties.image

Deciphering Interfacial Chemical and Electrochemical Reactions of Sulfide‐Based All‐Solid‐State Batteries

AbstractLarge interfacial resistance resulting from interfacial reactions is widely acknowledged as one of the main challenges in sulfide electrolytes (SEs)‐based all‐solid‐state lithium batteries (ASSLBs). However, the root cause of the large interfacial resistance between the SEs and typical layered oxide cathodes is not fully understood yet. Here, it is shown that interfacial oxygen loss from single‐crystal LiNi0.5Mn0.3Co0.2O2 (SC‐NMC532) chemically oxidizes Li10GeP2S12, generating oxygen‐containing interfacial species. Meanwhile, the interfacial oxygen loss also induces a structural change of oxide cathodes (layered‐to‐rock salt). In addition, the high operation voltage can electrochemically oxidize SEs to form non‐oxygen species (e.g., polysulfides). These chemically and electrochemically oxidized species, together with the interfacial structural change, are responsible for the large interfacial resistance at the cathode interface. More importantly, the widely adopted interfacial coating strategy is effective in suppressing chemically oxidized oxygen‐containing species and mitigating the coincident interfacial structural change but is unable to prevent electrochemically induced non‐oxygen species. These findings provide a deeper insight into the large interfacial resistance between the typical SE and layered oxide cathodes, which may be of assistance for the rational interface design of SE‐based ASSLBs in the future.

Surface Potential Regulation Realizing Stable Sodium/Na3 Zr2 Si2 PO12 Interface for Room-Temperature Sodium Metal Batteries.

Inorganic Na3 Zr2 Si2 PO12 is prospective with a high ionic conductivity but suffers large interfacial resistance and stability issues against sodium metal, hindering its practical application in all-solid-state sodium batteries. A surface potential regulation strategy is adopted to address these issues. Na3 Zr2 Si2 PO12 (NZSP) ceramic with homogeneously-sintered surface is synthesized by a simple two-step sintering method to promote its uniform surface potential, which is favorable for mitigating the potential fluctuations at the interface against Na metal and enhancing interfacial compatibility. The Na/NZSP interface can be stabilized for over 4 months with a low interfacial resistance of 129 Ω cm2 at 25 °C. The symmetrical Na/NZSP/Na cell exhibits ultra-stable sodium platting/stripping cycling for over 1000 cycles under 0.1mA cm-2 . Superior interfacial performance is well retained even under 0.2mA cm-2 at room temperature. The robust interface is further signified by its excellence under higher current densities of up to 0.85mA cm-2 at 60 °C. A 4V all-solid-state Na3 V1.5 Cr0.5 (PO4 )3 /NZSP/Na metal battery is demonstrated at ambient conditions, which exhibits superior rate capability and delivers a high reversible capacity of 103mA h g-1 under 100mA g-1 for over 400 cycles with a Coulombic efficiency of over 99%.

Interfacial compatibility issues in rechargeable solid-state lithium metal batteries: a review

Solid-state lithium metal batteries (SSLBs) contain various kinds of interfaces, among which the solid electrode|solid electrolyte (ED|SE) interface plays a decisive role in the battery’s power density and cycling stability. However, it is still lack of comprehensive knowledge and understanding about various interfacial physical/chemical processes so far. Although tremendous efforts have been dedicated to investigate the origin of large interfacial resistance and sluggish charge (electron/ion) transfer process, many scientific and technological challenges still remain to be clarified. In this review, we detach and discuss the critical individual challenge, including charge transfer process, chemical and electrochemical instability, space charge layers, physical contact and mechanical instability. The fundamental concepts, individual effects on the charge transfer and potential solutions are summarized based on material’s thermodynamics, electrode kinetics and mechanical effects. It is anticipated that future research should focus on quantitative analysis, modeling analysis and in-situ microstructure characterizations in order to obtain an efficient manipulation about the complex interfacial behaviors in all solid-state Li batteries.

Influence of Bi2O3 additive on the electrochemical performance of Na3.1Y0.1Zr1.9Si2PO12 inorganic solid electrolyte

Owing to the flammability of dendrites and organic liquid electrolytes, the safety performance of lithium-ion batteries cannot be effectively ensured. The sodium-ion solid electrolyte is anticipated to become the leading next generation battery in commercial applications due to the high thermal stability and low price. Yet, the insufficient ionic conductivity of Na3Zr2Si2PO12 solid electrolytes, along with the large interfacial resistance between the cathode material and the solid electrolyte, substantially restricts the performance of room-temperature all-solid-state sodium rechargeable batteries. In the present study, the effects of Bi2O3 additive on the phase, microstructure and ionic conductivity of Na3.1Y0.1Zr1.9Si2PO12 ceramic electrolyte are reported. Moreover, a significant room temperature conductivity of 1.21 × 10-3 S cm-1 and the dense microstructure was attained by adding 1 wt% Bi2O3 to Na3.1Y0.1Zr1.9Si2PO12 sintered at 1100 °C for 6 h. Simultaneously, an electrochemical test exhibited that the electrochemical stability window increased to 4.8 V and revealed good cycle stability.

Sliding Water Droplet on Oil Impregnated Surface and Dust Particle Mitigation.

Self-cleaning of surfaces becomes challenging for energy harvesting devices because of the requirements of high optical transmittance of device surfaces. Surface texturing towards hydrophobizing can improve the self-cleaning ability of surfaces, yet lowers the optical transmittance. Introducing optical matching fluid, such as silicon oil, over the hydrophobized surface improves the optical transmittance. However, self-cleaning ability, such as dust mitigation, of the oil-impregnated hydrophobic surfaces needs to be investigated. Hence, solution crystallization of the polycarbonate surface towards creating hydrophobic texture is considered and silicon oil impregnation of the crystallized surface is explored for improved optical transmittance and self-cleaning ability. The condition for silicon oil spreading over the solution treated surface is assessed and silicon oil and water infusions on the dust particles are evaluated. The movement of the water droplet over the silicon oil-impregnated sample is examined utilizing the high-speed facility and the tracker program. The effect of oil film thickness and the tilting angle of the surface on the sliding droplet velocity is estimated for two droplet volumes. The mechanism for the dust particle mitigation from the oil film surface by the sliding water droplet is analyzed. The findings reveal that silicon oil impregnation of the crystallized sample surface improves the optical transmittance significantly. The sliding velocity of the water droplet over the thick film (~700 µm) remains higher than that of the small thickness oil film (~50 µm), which is attributed to the large interfacial resistance created between the moving droplet and the oil on the crystallized surface. The environmental dust particles can be mitigated from the oil film surface by the sliding water droplet. The droplet fluid infusion over the dust particle enables to reorient the particle inside the droplet fluid. As the dust particle settles at the trailing edge of the droplet, the sliding velocity decays on the oil-impregnated sample.

Interfacial Engineering in a Cathode Composite Based on Garnet‐Type Solid‐State Li‐Ion Battery with High Voltage Cycling

AbstractGarnet‐type solid electrolyte is a promising candidate for the fabrication of high energy all‐solid‐state Li‐ion batteries (ASSLIBs), but its use is hampered by a large interfacial resistance. Herein, we propose a surface modification and subsequent sintering to enhance the interfacial connection between the cathode and the solid electrolyte. The ASSLIB prepared by this method delivered an initial discharge capacity of ∼66 mAh g−1 (80 °C) at a rate of 0.1 C. However, the poor contact between the cathode and electrolyte triggered the increase of the interfacial resistance, which caused severe capacity decay upon cycling. The encapsulation of LiCoO2 particles with LiBO2 using a single‐step sintering process dramatically increased the interfacial contact, resulting in a higher discharge capacity of 116 mAh g−1 with good cycling behavior. Therefore, surface modification of the cathode offers a reduction of resistance and promotes efficient Li‐ion transfer pathways across the cathode/solid‐electrolyte interface.

Interfacial modification enabled room temperature solid-state lithium–metal batteries

Lithium solid-state batteries (SSBs) with tantalum doped Li7La3Zr2O12 (LLZT) inorganic ceramic electrolytes have been attracting much interest for its extraordinary lithium ionic conductivity, non-flammability, and wide electrochemical window. However, poor solid–solid contact between the electrodes and electrolyte results in large interfacial resistance, which hinders its normal operation and practical application. Herein, triethylene glycol diacetate-2-propenoic acid butyl ester (TEGDA-BA) based gel polymer electrolytes (GPE) were fabricated and coated on both sides of spark plasma sintering (SPS)–derived LLZT pellet. GPE introduction not only provides intimate contact between solid electrolyte and electrodes but also avoids side reactions such as reduction of LLZT by lithium anode. Moreover, symmetric Li cell markedly reduced interfacial resistance and exhibited a critical current density up to 1.0 mA cm−2 at room temperature (25 °C), and it can also stably cycle at 0.5 mA cm−2 for over 277 h without Li dendrite formation. The assembled solid-state LiNi0.5Co0.2Mn0.3O2 (NCM523)/GPE–LLZT–GPE/Li battery exhibits high initial capacity (163.5 mAh g−1) at 0.2 C. This work provides a facile method to reduce the interfacial resistance and demonstrates durable high-energy solid-state lithium metal batteries suitable for practical application.

Recent progress in thermally conductive polymer/boron nitride composites by constructing three-dimensional networks

As one of the critical components in thermal management system, high thermally conductive polymer composites is the key factor affecting the heat dissipation of electronic devices. During the past few decades, considerable researches have been done to enhance the thermal conductivity of polymer composites by adding fillers with high thermal conductivity, such as metals, carbon-based materials and ceramics. Boron nitride (BN) has been considered as an ideal thermally conductive filler for polymer composites. However, the large interfacial thermal resistance at the filler-matrix interfaces and the filler-filler interfaces has greatly hampered the heat conduction, resulting in the limited improvement in thermal conductivity. In this mini review, we attempt to present recent progress in fabricating high thermally conductive polymer/boron nitride composites by constructing three-dimensional networks. We started from introducing the thermal conduction mechanism in polymer composites, and then briefly discussed the factors influencing the thermal conductivity of polymer composites, followed by presenting different fabrication methods of constructing three-dimensional networks in polymer/boron nitride composites to increase the thermal conductivity. We hope this mini review would provide some beneficial inspiration for improving the thermal conductivity of polymer composites.

In-situ formation of LiF-rich composite interlayer for dendrite-free all-solid-state lithium batteries

Polyethylene oxide (PEO)-based composite electrolytes are considered as competent candidates to achieve high energy density all-solid-state lithium batteries (ASSLBs) due to good flexibility, which can effectively solve the problem of large interfacial resistance with electrodes. However, poor mechanical strength and low Li+ transference number can’t restrain the formation and growth of Li dendrites, leading to parasitic reaction between electrolyte and Li anode and unsatisfied coulombic efficiency. Herein, Li metal is pre-treated by poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP)/CuF2 composite to form a stable interlayer on the anode. In-situ reaction of CuF2 with Li greatly improves the contact between PVDF-HFP layer and Li anode, forming a LiF-rich modified layer. The interlayer with high mechanical strength and ionic conductivity can not only suppress the formation of Li dendrites, but also achieve the growth restriction and elimination of dendrites. Moreover, excellent elasticity and strong adhesion with Li anode can ensure the structure stability of modified layer during dynamic plating/stripping of Li. Applied in ASSLBs with PEO-based electrolyte, PVDF-HFP/CuF2 modified symmetrical Li cells demonstrate increased critical current density and extended cycle life than that of bare Li or single CuF2 treated Li. Furtherly, the ASSLBs with LiFePO4 cathode show excellent cycle stability and high coulombic efficiency over 1000 cycles at 1 C.

Synthesis and electrochemical performance of (100-x)Li7P3S11-xLi3SI composite solid electrolyte for all-solid-state lithium batteries

Li7P3S11 (LPS) solid electrolytes have great advantages, such as high lithium-ion conductivity, and can easily fabricate to make bulk-type all-solid-state lithium batteries. However, LPS has a disadvantage because of large interfacial resistance with lithium, which give a limitation for all-solid-state battery. In this study, (100-x)Li7P3S11-x Li3SI (x=0. 2 and 5) solid electrolyte composites are prepared by mechanical ball milling process. Various physiochemical analysis was carried out to confirm the proper mixing of Li7P3S1 and Li3SI solid electrolytes. The addition of Li3SI solid electrolyte, effectively influence the ionic conductivity and electrochemical properties of the Li7P3S1 solid electrolyte. The prepared Li7P3S11/Li3SI solid electrolyte composites are stable against the lithium metal anode even after 100h charge-discharging process and has stable potential window up to 10V. In particular, 98Li7P3S11-2Li3SI solid electrolyte based ASSLBs shows the highest capacity, of 110mA/g at the current density of 7.5mA g−1 (0.05 C). The charge – discharge cycle stability test also proved the Li3SI mixing to Li7P3S11 helped to maintain the capacity retention value of ∼100 % after 10 cycles. Therefore, the Li3SI into the Li7P3S11 electrolyte helps improve the electrochemical performance.

Ionic Liquid Therapy for Reducing Interfacial Resistance Between Electrode and Ceramic Solid Electrolyte

The main concerns of the electric vehicle (EV) industry are the relatively low driving range and safety issues. The safety issues become more problematic with increasing battery size because conventional liquid electrolytes, e.g., ethylene carbonate (EC), are highly flammable. Although ceramic solid electrolytes, e.g., Li7La3Zr2O12 (LLZO), are promising candidates to replace the conventional liquid electrolytes for developing high-performance solid-state Li metal batteries, the large interfacial resistance between solid electrolytes and electrodes, particularity at the cathode-side, severely limits the practical application of those ceramic electrolytes. Here we developed an ionic liquid (IL)-containing while non-fluidic quasi-solid-state composite cathode, which can maintain a good contact with ceramic electrolytes. For example, the interfacial resistance between LiCoO2 (LCO) and Al-doped LLZO (Al-LLZO) decreased significantly with introduction of an IL. Quasi-solid-state LCO/Al-LLZO/Li cells demonstrated a relatively high capacity retention about 80% after 100 cycles at 60 °C. The IL therapy offers a simple and practical approach to addressing the interfacial resistance issue between cathodes and solid electrolytes. Nevertheless, the performance of the quasi-solid-state composite cathode is dependent on the type as well as the content of the IL. Thus, identifying a suitable IL as well as its optimal content is critical for the development of quasi-solid-state Li-metal batteries.

A Multilayer Ceramic Electrolyte for All-Solid-State Li Batteries.

Despite of the good stability with Li-metal, Li6.75 La3 Zr1.75 Ta0.25 O12 (LLZTO) suffers from large interfacial resistance and severe Li-metal penetration. Herein, a dual layer ceramic electrolyte of Ti-doped LLZTO(Ti-LLZTO)/LLZTO was developed, with the reducible Ti-LLZTO layer contacting Li-metal and the LLZTO layer contacting cathode. The identical crystal structures of Ti-LLZTO and LLZTO enables a seamless contact and a barrierless Li+ transport between them. The densities of Ti-LLZTO pellets are higher than that of LLZTO. With an in situ reduction of Ti-LLZTO by Li-metal, the interfacial wettability was improved and a mixed ion-electron conducting layer was created. Both features help to reduce defects/pores on interface and homogenize the interfacial ionic/electronic flux, facilitating the reduction of interfacial resistance and suppression of dendrites. With the help of Ti-LLZTO layer, long-term stable lithium plating/stripping was reached in an areal capacity of 3.0 mAh cm-2 .

A Multilayer Ceramic Electrolyte for All‐Solid‐State Li Batteries

AbstractDespite of the good stability with Li‐metal, Li6.75La3Zr1.75Ta0.25O12(LLZTO) suffers from large interfacial resistance and severe Li‐metal penetration. Herein, a dual layer ceramic electrolyte of Ti‐doped LLZTO(Ti‐LLZTO)/LLZTO was developed, with the reducible Ti‐LLZTO layer contacting Li‐metal and the LLZTO layer contacting cathode. The identical crystal structures of Ti‐LLZTO and LLZTO enables a seamless contact and a barrierless Li+ transport between them. The densities of Ti‐LLZTO pellets are higher than that of LLZTO. With an in situ reduction of Ti‐LLZTO by Li‐metal, the interfacial wettability was improved and a mixed ion‐electron conducting layer was created. Both features help to reduce defects/pores on interface and homogenize the interfacial ionic/electronic flux, facilitating the reduction of interfacial resistance and suppression of dendrites. With the help of Ti‐LLZTO layer, long‐term stable lithium plating/stripping was reached in an areal capacity of 3.0 mAh cm−2.

Enhanced Performance of Li6.4La3Zr1.4Ta0.6O12 Solid Electrolyte by the Regulation of Grain and Grain Boundary Phases.

The application of Li-ion conducting garnet electrolytes is challenged by their large interfacial resistance with the metallic lithium anode and the relative small critical current density at which the lithium dendrites short-circuit the battery. Both of these challenges are closely related to the morphology and the structure of the garnet membranes. Here, we prepared four polycrystalline garnet Li6.4La3Zr1.4Ta0.6O12 (LLZTO) pellets with different particle sizes (nano/micro) and grain boundary additive (with/without Al2O3) to investigate the influence of grain size, the composition of the grain boundary, and the mechanical strength of the pellet on the total Li-ion conduction of the pellet, Li/garnet interfacial transfer, and lithium dendrite growth in all-solid-state Li-metal cells. The results showed that the garnet pellets prepared with nanoparticles and LiAlO2-related grain boundary phase had decreased total Li-ion conductivity because of the increased resistance of the grain boundary; however, these pellets showed higher mechanical strength and improved capability to suppress lithium dendrite growth at high current densities. By controlling the grain size and optimizing the grain boundary with Al2O3 sintering additive, the hot-pressing sintered LLZTO solid electrolytes can reach up to 1.01 × 10-3 S cm-1 in Li+ conductivity and 0.29 eV in activation energy. LLZTO with nanosized grain and LiAlO2-modified grain boundary showed the highest critical current density, which is 0.6 mA cm-2 at room temperature and 1.7 mA cm-2 at 60 °C. This study offers a useful guideline for preparing a high-performance LLZTO solid electrolyte.