NASICON-type Solid Electrolyte Research Articles

An automatic descriptors recognizer customized for materials science literature

Materials science literature contains domain knowledge about numerous descriptors, which play a critical role in data-driven materials design. However, automatically extracting descriptors from literature remains challenging. Here, we develop an automatic descriptors recognizer based on natural language processing (NLP) to mine latent descriptors, which consists of a conditional data augmentation model incorporating materials domain knowledge (cDA-DK), coarse- and fine-grained descriptors subrecognizers (CGDR and FGDR). cDA-DK conducts augmenting training data of text mining model, which can significantly reduce the cost of manually labeling and enhance the robustness of its model. On this basis, CGDR recognizes coarse-grained descriptor entities automatically, and FGDR performs screening of fine-grained descriptors related to specific materials design. Following this, the activation energy of NASICON-type solid electrolytes, which is influenced by complicated descriptors, is taken as an example to demonstrate the potential utility of our recognizer. CGDR extracts 106896 descriptor entities from 1808 relevant articles with an accuracy (F1) of 0.87. Furthermore, with features from 408 descriptors screened by FGDR, six activation energy prediction models are constructed to perform experiments, achieving an optimal prediction performance (R2) of 0.96. This work provides important insight towards the understanding of structure-activity relationships, thus promoting materials design and discovery.

Enhanced ionic conductivity of composite solid electrolyte by directionally ordered structures of linear Li1.3Al0.3Ti1.7(PO4)3

The NASICON-type solid electrolyte structure of Li1.3Al0.3Ti1.7(PO4)3 (LATP) exhibits good electrochemical performance and thermal stability, and has been promising as a solid electrolyte. Here, a stable good-stability LATP precursor spinning solution was prepared using the sol–gel method for the first time. A linear LATP solid electrolyte with an oriented ordered structure was obtained using improved electrostatic spinning equipment. The sintering process regime of the LATP-ordered construction was determined. The ionic conductivity of the prepared LATP-PEO/LiClO4-PEG composite solid-state electrolyte with an ordered structure was as high as 2.05 × 10-4 S·cm−1 at room temperature (25 °C), one order of magnitude higher than the ionic conductivity of the LATP composite solid-state electrolyte reported so far. Organic solid-state electrolytes to protect LATP-ordered structured solid-state electrolytes yield excellent electrochemical stability in lithium-metal batteries.

Dopant effect on Li+ ion transport in NASICON-type solid electrolyte: Insights from molecular dynamics simulations and experiments

The performance of sodium superionic conductor (NASICON)-type LiZr2(PO4)3 (LZP) solid electrolytes for Li-ion batteries is dependent on their ion transportation properties. Therefore, to achieve high stability, ionic conductivity, and good compatibility with Li, the LZP solid electrolyte has chosen and doped with Al to improve aforesaid properties. Also, the effect of the dopant on various parameters has been investigated via MD simulations and experimentally. In this study, molecular dynamics (MD) simulations were used to investigate the effect of Al doping on the ion transport properties of Li1+xAlxZr2−x(PO4)3 (LAZP, x = 0.0–1.0) solid electrolytes. A facile solid-state reaction was used to synthesize both pristine and Al-doped solid electrolytes and to estimate the effect of doping on the ionic conductivity and ion diffusion in LZP. Computational and experimental results provided strong evidence of improved ion conductivity and diffusion in LZP owing to the presence of the Al dopant. Furthermore, the computational results agreed well with the experimental results, thereby validating the computational model. A maximum ionic conductivity of σLi = 2.77 × 10−5 S cm −1 (for x = 0.2) was obtained. Enhanced ionic conductivity was observed with Al dopants owing to the creation of interstitial Li ions through a reduction in grain boundary resistance. However, a further increase in the amount of dopant reduced the ionic conductivity of LZP owing to Li-ion trapping at the most stable and metastable sites around the Al insertions. Doped LZP solid electrolytes are suitable for use in energy storage devices because of their enhanced ionic conductivity compared to that of pristine LZP.

Interface modification of NASICON-type Li-ion conducting ceramic electrolytes: a critical evaluation

This review article focuses on the methods to solve the critical issue of reduction in NASICON-type solid electrolytes such as Li1+xAlxTi2−x(PO4)3 and Li1+xAlxGe2−x(PO4)3 by Li metal.

A niobium-substituted sodium superionic conductor with conductivity higher than 5.5 mS cm−1 prepared by solution-assisted solid-state reaction method

Although research on all-solid-state sodium batteries (ASSSBs) have been conducted for many years, the solid-state electrolyte (SSE) material is still far from practical application at room temperature. One major reason is that no suitable electrolyte material with high ionic conductivity has been found yet. In this study, Nb5+ is introduced into NASICON-type solid electrolyte, where Nb5+ substituted Na3.4Zr2Si2.4P0.6O12 (NZSP) is prepared by a solution-assisted solid-state reaction method. The best ionic conductivity is as high as 5.51 mS cm−1 which is a significant improvement. High-frequency electrochemical impedance spectroscopy shows that the increase in total conductivity is mainly due to the decrease of grain boundary impedance as well as bulk impedance. The decrease in grain boundary impedance is probably owing to the increase in density of the electrolyte material after incorporation of the Nb content, which has a beneficial impact of the sintering of NZSP. The decrease in bulk impedance rather results from the ratio of sodium ion concentration and sodium vacancy concentration of 3.3:0.7 in the crystal structure, thus facilitating the sodium ion transport. Symmetric cells with sodium metal as electrodes (Na|Nb5+ substituted NZSP|Na) are subsequently assembled and cycled stably for 60 cycles at a current density of 0.05 mA/cm2.

Process optimisation for NASICON-type solid electrolyte synthesis using a combination of experiments and bayesian optimisation

The optimal sintering conditions for LiZr2(PO4)3, a NASICON-type solid electrolyte with high conductivity, were explored. It was also found that these optimum sintering conditions could be efficiently discovered by using Bayesian optimisation.

Bayesian optimisation with transfer learning for NASICON-type solid electrolytes for all-solid-state Li-metal batteries.

NASICON-type LiZr2(PO4)3 (LZP) has attracted significant attention as a solid oxide electrolyte for all-solid-state Li-ion or Li-metal batteries owing to its high Li-ion conductivity, usability in all-solid-state batteries, and electrochemical stability against Li metal. In this study, we aim to improve the Li-ion conductivity of Li-rich NASICON-type LZPs doped with CaO and SiO2, i.e., Li1+x+2y Ca y Zr2-y Si x P3-x O12(0 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.3) (LCZSP). Herein, a total of 49 compositions were synthesised, and their crystal structures, relative densities, and Li-ion conductivities were characterised experimentally. We confirmed the improvement in Li-ion conductivity by simultaneous replacement of Zr and P sites with Ca and Si ions, respectively. However, the intuition-derived determination of the composition exhibiting the highest Li-ion conductivity is technically difficult because the compositional dependence of the relative density and the crystalline phase of the sample is very complex. Bayesian optimisation (BO) was performed to efficiently discover the optimal composition that exhibited the highest Li-ion conductivity among the samples evaluated experimentally. We also optimised the composition of the LCZSP using multi-task Gaussian process regression after transferring prior knowledge of 47 compositions of Li1+x+2y Y x Ca y Zr2-x-y P3O12 (0 ≤ x ≤ 0.376, 0 ≤ y ≤ 0.376) (LYCZP), i.e., BO with transfer learning. The present study successfully demonstrated that BO with transfer learning can search for optimal compositions two times as rapid as the conventional BO approach. This approach can be widely applicable for the optimisation of various functional materials as well as ionic conductors.

Preparation and infiltration of NASICON-type solid electrolytes with microporous channels

A lithium-ion conductor with microporous channels (p-LATP) was prepared by using templates from a hydrothermal-assisted sol-gel method, and the as-prepared p-LATP was infiltrated to obtain p-LATP and d-LATPs composites in this work. SEM photos showed that the morphologies of p-LATP, d-LATP, and p-LATP and d-LATP composites were quite similar. XRD analysis showed that the crystallographic structures were also similar. TEM examinations revealed that microporous channels existed in the pure p-LATP and the p-LATP and d-LATP composites but not in the pure d-LATP. The total conductivities of the composites were higher than those of the pure p-LATP and pure d-LATP. The enhancement of the total conductivity of the composites was ascribed to the interaction of microporous channels and dense lithium-ion conducting areas. The promising results obtained in this work provide a new way to prepare solid lithium-ion conductors.

Negating the Interfacial Resistance between Solid and Liquid Electrolytes for Next-Generation Lithium Batteries.

The combination of solid and liquid electrolytes enables the development of safe and high-energy batteries where the solid electrolyte acts as a protective barrier for a high-energy lithium metal anode, while the liquid electrolyte maintains facile electrochemical reactions with the cathode. However, the contact region between the solid and liquid electrolytes is associated with a very high resistance, which severely limits the specific energy that can be practically delivered. In this work, we demonstrate a suitable approach to virtually suppress such interfacial resistance. Using a NASICON-type solid electrolyte in a variety of liquid electrolytes (ethers, DMSO, acetonitrile, ionic liquids, etc.), we show that the addition of water as electrolyte additive decreases the interfacial resistance from >100 Ω cm2 to a negligible value (<5 Ω cm2). XPS measurements reveal that the composition of the solid-liquid electrolyte interphase is very similar in wet and dry liquid electrolytes, and thus the suppression of the associated resistance is tentatively ascribed to a plasticizer or preferential ion solvation effect of water, or to a change in the interphase morphology or porosity caused by water. Our simple estimates show that the improvement in the solid-liquid electrolyte interphase resistance observed here could translate to an enhancement of 15-22% in the practical energy density of a Li-S or Li-O2 battery and improvements in the roundtrip efficiency of 21-28 percentage points.

Prevention of Reduction in Nasicon-Type Solid Electrolyte By Thin Polymer Coating

The next generation energy storage systems endeavor to implement solid electrolytes for safety reasons, enhancing cycle life and thermal stability of a battery. One of the most promising solid electrolytes is NASICON structured ceramic material with composition of Li1.3Al0.3Ti1.7(PO4)3, which is stable towards air and moisture. However, NASICON-type electrolyte containing titanium metal suffers from reduction while contacting with Li metal. Reduction of Ti4+ to Ti3+ leads formation of the secondary phase that hinders lithium ion conduction between the solid electrolyte and electrode. By all means, this could be resolved by applying thin composite gel polymer electrolyte (GPE) as artificial buffer layer using layer by layer (LbL) technique. Despite preventing the side reaction, the coated layer improves interfacial contact between two solid phases. The structure and morphology of the solid electrolytes were confirmed by XRD, SEM images. The effect of polymer coating was observed via several electrochemical examinations. Acknowledgement This research was supported by the research grant #OPFE2021001 "New materials and devices for defense and aerospace applications" from MDDIAI Republic of Kazakhstan.

Insights into the local structure, microstructure and ionic conductivity of silicon doped NASICON-type solid electrolyte Li1.3Al0.3Ti1.7P3O12

NASICON-type solid electrolyte Li1.3Al0.3Ti1.7P3O12 (LATP) is attractive because of the cheap raw materials, excellent air stability, and high ionic conductivity. Silicon doping is generally adopted to improve its conductivity further, but the corresponding mechanism is vacant. Herein, we synthesize the silicon doped LATP electrolyte with a simple solution-based method and systemically investigate the effects of different silicon doping level on the local structure, microstructure and ionic diffusion kinetics of the solid electrolytes. We firstly put forward the octahedral occupation of silicon in Li1.3Al0.3Ti1.7P3O12 electrolyte instead of tetrahedral sites. Silicon doping is found to be negative for the ionic transportation in grain bulk, however, the grain boundary conductivity can be increased after a small amount of silicon doping due to the modification of micro-structure, i, e., the silicon doping induces the segregation of LiTiOPO4 in the grain boundary, which can effectively suppress the abnormal growth of electrolyte grains and concomitant gas pores and cracks during sintering. As a result, the total conductivity can reach ∼10−3 S⋅cm−1 after silicon doping with this simple method. Our results demonstrate the critical importance of adjusting secondary phase on the micro-structure and ionic conductivity of electrolyte during the development of inorganic fast ionic conductors.

Co-precipitation synthesis and electrochemical properties of NASICON-type Li1.3Al0.3Ti1.7(PO4)3 solid electrolytes

NASICON-type solid electrolytes have gathered wide attention to meet the requirements of high energy density Li-metal batteries. In this study, Li1.3Al0.3Ti1.7(PO4)3 (LATP) were synthesized through co-precipitation method. The composition, phase transformation, microstructure, and particle size of LATP powder were characterized in detail. Pure LATP phase can be obtained at 800 °C with primary particle size of ~ 590 nm. In addition, the ionic conductivities of LATP pellets increased at first and then decreased with the increased sintering temperature and time. Owing to the highest relative density (95.6%), LATP (sintered at 900 °C for 6 h, LATP-9006) exhibited a highest total conductivity of 2.19 × 10−4 S/cm with a low activation energy of 0.32 eV. The results suggest that co-precipitation synthesized LATP-9006 ceramic electrolyte could be a promising alternative toward achieving a safe solid-state battery. Moreover, the co-precipitation method is suitable for the preparation of other oxide ceramic electrolytes.

Fracture behavior of solid electrolyte LATP material based on micro-pillar splitting method

The NASICON type solid electrolyte LATP is a promising candidate for all-solid-state Li-ion batteries considering energy density and safety aspects. To ensure the performance and reliability of batteries, crack initiation and propagation within the electrolyte need to be suppressed, which requires knowledge of the fracture characteristics. In the current work, micro-pillar splitting was applied to determine the fracture toughness of LATP material for different grain orientations. The results are compared with data obtained using a conventional Vickers indentation fracture (VIF) approach. The fracture toughness obtained via micro-pillar splitting test is 0.89 ± 0.13 MPa∙m1/2, which is comparable to the VIF result, and grain orientation has no significant effect on the intrinsic fracture toughness. Being a brittle ceramic material, the effect of pre-existing defects on the toughness needs to be considered.

Influence of LiBF4 sintering aid on the microstructure and conductivity of LATP solid electrolyte

To improve sintering performance, LiBF4, as a novel sintering aid, was added to a NASICON-type solid electrolyte LATP, which was synthesized by the sol-gel method. The microstructure, crystallinity and lithium-ion conductivity of the obtained LATP was measured by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Raman spectroscopy, MAS NMR and impedance spectroscopy (IS). Results indicate that during sintering, LiBF4 not only forms liquid phase to promote the growth of grains, but also forms a replacement solid solution with LATP. A small amount of boron and fluorine substitutes phosphorus and oxygen, thus entering the LATP lattice and forming a channel that is more suitable for Li-ion migration. The formation of the solid solution phase of LiBF4 and LATP also leads to the gradual disappearance of grain boundaries, which further promotes the improvement in ionic conductivity. The highest ionic conductivity of the LATP sintered pellet obtained with 3 wt% LiBF4 is 0.85 mScm−1.

Stability of Solid-State Sintered Li1.5Al0.5Ge1.5(PO4)3 Solid Electrolytes in Var-ious Mediums for All Solid-State Li-ion Batteries

Solid electrolytes are strong candidates for next-generation Li-ion bat-teries for Electrical Vehicle (EV) applications. However, their usage is not widely spread because of their relatively poor ionic conductivity and high electrode/electrolyte interfacial resistance compared to their com-mercial counterparts, organic based liquid electrolytes. Sodium Superi-onic Conductor (NASICON) type solid electrolytes could be an option to overcome these problems. Li1.5Al0.5Ge1.5(PO4)3 (LAGP) stands forward among other NASICON type solid electrolytes with their easy synthesis and processing. Yet, their stability against various mediums remain un-known and needs to be enlightened. In this study, the stability of LAGP against water, air at 85°C and 1M LiOH solution was discussed. LAGP re-sults after sintering at 900°C for 3 hours showed impurity-free, highly dense structure with a restricted grain growth. Water and air aged sam-ples showed a dramatical reduction on grain boundary contribution of to-tal ionic conductivity whereas the sample aged at 1M LiOH solution ex-hibited both reduction in ionic conductivity and increase on grain boundary conductivity. The highest reduction on total ionic conductivity was observed on the sample aged in water. On the contrary, the sample aged in 1M LiOH solution resulted in a net increase on total ionic con-ductivity. The highest total conductivity of 4.3 x 10-4 S/cm was obtained from the sample aged in 1M LiOH. On the other hand, the sample aged the lowest conductivity – 1.8 x 10-4 S/cm – showed the lowest total con-ductivity of all samples.

Phase Behavior in Nasicon Electrolytes and Electrodes

An avenue to create safer batteries is to replace the liquid electrolyte with a non-flammable solid electrolyte.1–3 A good candidate is the Natrium superionic conductor (NaSiCON) Na1+xZr2SixP3-xO12 (0 x 3) which displays high bulk ionic conductivity and good relative stability towards other NaSiCON-based electrodes.2 Despite the sizeable share of research on the Na1+xZr2SixP3-xO12 material, the structural properties of NaSiCON are still poorly understood and as a result the optimisation of this class of materials often follows chemical intuition.4–9 Here, we analyse the phase behaviour of the NaSiCON electrolyte by constructing the Na1+xZr2SixP3-xO12 phase diagram as a function of temperature and composition (0 x 3) for the high-temperature rhombohedral phase. This phase is also common in several Na-based positive electrodes, such as Na3Ti2(PO4)3, Na3V2(PO4)3 and Na3Cr2(PO4)3. Using a multi-scale approach, based on density functional theory, the cluster expansion formalism and Monte Carlo simulations, we elucidate: i) the entire phase-diagram of NaSiCON as a function of temperature and Na content, identifying the regions providing the highest Na+-ion conductivity; ii) previously, unreported phase-separation behaviour in a specific region of the phase diagram, iii) the relationship between the population of Na-sites and the relative ratio of Si:P in the structure. We reveal that kinetic effects hinder the expected mechanism of phase separation in Na1+xZr2SixP3-xO12. We then extended these principles between the competition of thermodynamic and kinetic driving forces derived on Na1+xZr2SixP3-xO12 to popular mono-transition metal NaSiCON electrodes, which all tend to phase separate upon Na extraction/insertion. These results are important for the development of inexpensive Na-ion batteries.(1) Janek, J.; Zeier, W. G. A Solid Future for Battery Development. Nature Energy 2016, 1 (9), 16141. https://doi.org/10.1038/nenergy.2016.141.(2) Famprikis, T.; Canepa, P.; Dawson, J. A.; Islam, M. S.; Masquelier, C. Fundamentals of Inorganic Solid-State Electrolytes for Batteries. Nat. Mater. 2019, 18, 1278–1291. https://doi.org/10.1038/s41563-019-0431-3.(3) Canepa, P.; Dawson, J. A.; Sai Gautam, G.; Statham, J. M.; Parker, S. C.; Islam, M. S. Particle Morphology and Lithium Segregation to Surfaces of the Li7La3Zr2O12 Solid Electrolyte. Chemistry of Materials 2018, 30 (9), 3019–3027. https://doi.org/10.1021/acs.chemmater.8b00649.(4) Hong, H. Y.-P. Crystal Structures and Crystal Chemistry in the System Na1+xZr2SixP3−xO12. Materials Research Bulletin 1976, 11 (2), 173–182. https://doi.org/10.1016/0025-5408(76)90073-8.(5) Boilot, J. P.; Collin, G. Relation Structure-Fast Ion Conduction in the NASICON Solid Solution. J. Solid State Chem. 1988, 73, 160–171.(6) Masquelier, C.; Croguennec, L. Polyanionic (Phosphates, Silicates, Sulfates) Frameworks as Electrode Materials for Rechargeable Li (or Na) Batteries. Chem. Rev. 2013, 113 (8), 6552–6591. https://doi.org/10.1021/cr3001862.(7) Ma, Q.; Guin, M.; Naqash, S.; Tsai, C.-L.; Tietz, F.; Guillon, O. Scandium-Substituted Na3Zr2(SiO4)2(PO4) Prepared by a Solution-Assisted Solid-State Reaction Method as Sodium-Ion Conductors. Chemistry of Materials 2016, 28 (13), 4821–4828. https://doi.org/10.1021/acs.chemmater.6b02059.(8) Deng, Y.; Eames, C.; Nguyen, L. H. B.; Pecher, O.; Griffith, K. J.; Courty, M.; Fleutot, B.; Chotard, J.-N.; Grey, C. P.; Islam, M. S.; Masquelier, C. Crystal Structures, Local Atomic Environments, and Ion Diffusion Mechanisms of Scandium-Substituted Sodium Superionic Conductor (NASICON) Solid Electrolytes. Chem. Mater. 2018, 30 (8), 2618–2630. https://doi.org/10.1021/acs.chemmater.7b05237.(9) Zhang, Z.; Zou, Z.; Kaup, K.; Xiao, R.; Shi, S.; Avdeev, M.; Hu, Y.-S.; Wang, D.; He, B.; Li, H.; Huang, X.; Nazar, L. F.; Chen, L. Correlated Migration Invokes Higher Na+-Ion Conductivity in NaSICON-Type Solid Electrolytes. Advanced Energy Materials 2019, 9 (42), 1902373. https://doi.org/10.1002/aenm.201902373.

In Situ Synchrotron Radiation XRD and XAFS Measurements of Multilayer All-Solid-State Lithium-Ion Batteries Using Li2CoP2O7 as a Positive Electrode Material

All-solid-state lithium-ion batteries are expected as next-generation batteries due to their safety and high volumetric energy density. We reported Li2CoP2O7 (LCPO) as a positive electrode material with charge/discharge reactions over 5 V. [1–3] In this study, the structural and valence change of LCPO in multilayer all-solid-state lithium-ion batteries during charge/discharge was investigated using in situ synchrotron radiation X-ray diffraction (XRD) and X-ray Absorption Fine Structure (XAFS) measurements.In multilayer all-solid-state lithium-ion batteries, LCPO was the positive electrode active material, Ti-based oxide was the negative electrode active material, and NASICON-type solid electrolyte was used as the solid electrolyte. Each material for the positive and negative electrodes and the solid electrolyte was made into a paste. They were laminated using a screen printing method and integrally sintered to produce multilayer all-solid-state batteries. Synchrotron radiation XRD and XAFS measurements were performed at the large synchrotron radiation facility SPring-8. In situ XRD was measured in a transmission mode using 30 keV X-rays for a multilayer all-solid-state battery. The X-ray beam had to pass through the center of the multilayer all-solid-state battery during the first charge/discharge reactions. In situ XAFS experiments were measured using a fluorescence method. XAFS scans covering the Co K edge peak were taken during the first charge/discharge reactions.Figure 1 shows the XRD patterns of the multilayer all-solid-state battery during the first cycle in the charge/discharge process. The main diffraction peaks of LCPO are located at around 13.0°, 14.4°, and 16.7°. The diffraction peak position at 16.7° gradually shifts to the lower degree side from its uncharged state and the peak intensity decreases during the charging process. In addition, the peak shift returns to the same position at the uncharged state during the discharging process. However, that is not completely. The diffraction peak intensity at 14.4° decreases. In the XAFS measurement results, the Co K edge spectrum shifts to the higher energy side compared to the uncharged state during the charging process. The Co K edge spectrum returns to the same energy position in the uncharged state during the discharging process. These results show that the valence of Co changes from 2+ to 3+ upon charging and returns from 3+ to 2+ upon discharging. We observed how the Co of the LCPO operates while the multilayer all-solid-state battery was charging and discharging.[1] A. Kato, The 395th Committee Of Battery Technology, (2019)[2] M. Kobayashi, et al., The 60th Battery Symposium, 2F19, (2019)[3] C. Yamamoto, et al., The 87th ECSJ Spring Meeting, (2020) Figure 1

Investigation of the stability of NASICON-type solid electrolyte in neutral-alkaline aqueous solutions

The effects of aqueous solutions with different pH values on the ionic conductivity of Na3Zr2Si2PO12 (NASICON) are studied at room temperature. The ionic conductivity of NASCION reduced severely in the solution with pH value of 7. The AC impedance method was used to study the changes of the bulk, grain boundary, and cracking surface resistances of the sample under different conditions. The electrolyte morphology, cell parameters, Na+ site occupancy fraction, and microscopic strain change were obtained by SEM and XRD data refinement. According to above analysis, the degradation processes of hydration, grain refinement, and surface cracking were observed gradually, the corresponding corrosion mechanism of NASICON in aqueous solutions was explained.

Increase in ionic conductivity of NASICON-type solid electrolyte Li1.5Al0.5Ti1.5(PO4)3 by Nb2O5 doping

A NASICON-type Li1.5Al0.5Ti1.5(PO4)3 (LATP) solid electrolyte was fabricated using a novel sol–gel approach with citric acid as a complex agent. An electrochemical impedance spectroscopy analysis shows that the ionic conductivity of the LATP solid electrolyte synthesized using the sol–gel route was low (8 × 10−5 S cm−1 at 303 K), owing to its large grain boundary impedance. To improve the ionic conductivity of the LATP conducting ceramic, we incorporated Nb2O5 as a doping agent into the LATP solid electrolyte. The effects of Nb2O5 on the phase composition, microstructure, and ionic conductivity of the LATP solid electrolyte were investigated. The LATP conducting ceramic with an 8-wt% Nb2O5 doping exhibited the highest total ionic conductivity of 3.54 × 10−4 S cm−1 at 303 K, relative density of 91.7%, and lowest activation energy of 0.271 eV. The fabricated LATP solid electrolyte doped with Nb2O5 is a promising material for electrochemical devices.

Chemomechanical Failure Mechanism Study in NASICON-Type Li1.3Al0.3Ti1.7(PO4)3 Solid-State Lithium Batteries

NASICON-type solid electrolytes such as Li1.3Al0.3Ti1.7(PO4)3 (LATP) have the following advantages: they are of low cost and environmentally friendly and they exhibit air stability and high ionic c...