Sulfide electrolyte grain boundary
212860787
The Effect of Space Charge on Blocking Grain Boundary Resistance in an Yttrium Doped Barium Zirconate Electrolyte for Solid Oxide Fuel Cells
The higher grain boundary resistance in the proton conducting yttrium doped barium zirconate is one of the major issues to be solved. A new strategy has been experimentally studied on the basis of
Aarthi Uthayakumar Arunkumar Pandiyan Sribalaji Mathiyalagan Anup Kumar Keshri Suresh Babu Krishna Moorthy
227252492
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 x 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 degC. This study offers a useful guideline for preparing a high performance LLZTO solid electrolyte.
ACS applied materials interfaces
Zeya Huang Linhui Chen Bing Huang Biyi Xu Gang Shao Hailong Wang Yutao Li Chang-An Wang
234131557
High Ionic Conductivity Achieved in Li3Y(Br3Cl3) Mixed Halide Solid Electrolyte via Promoted Diffusion Pathways and Enhanced Grain Boundary
The development of all solid state batteries is limited by the low ionic conductivity of solid electrolytes. Beyond sulfides and oxides, halides represent another family of solid electrolytes with
Zhantao Liu Shuan Ma Jue Liu Shan Xiong Hailong Chen
199064915
Consolidating the grain boundary of the garnet electrolyte LLZTO with Li3BO3 for high performance LiNi0.8Co0.1Mn0.1O2/LiFePO4 hybrid solid batteries
All solid state batteries have received significant attention due to their excellent safety performance. As a key component, the garnet type electrolyte is one of the best known electrolytes due to its air stability and good compatibility with metallic lithium. However, the total Li+ conductivity of this kind of electrolyte is usually lower than that of the bulk electrolyte primarily due to the grain boundary resistance. In this study, we focused on engineering the electrolyte Li6.4La3Zr1.4Ta0.6O12 (LLZTO) by introducing Li3BO3 (LBO) into it to form the electrolyte LLZTO/LBO with the aim to consolidate the grain boundary. Via characterization by both neutron and X ray diffraction, the as prepared LLZTO was indexed as a pure cubic phase, where Ta certainly substituted the Zr sites. LLZTO/LBO still maintained the cubic structure, and the B atoms did not occupy any cation sites in the unit cell. It was demonstrated that an amorphous phase of a boracic substance was trapped inside the cubic LLZTO phase. The amorphous boracic phase sutured the gaps among the LLZTO grains and then lowered the grain boundary resistance without introducing impurities, ultimately consolidating the solid state electrolyte. Electrochemical impedance spectroscopy revealed that the total Li+ conductivity of LLZTO/LBO reached 5.47 x 10 4 S cm 1, much higher than those of the as prepared Li7La3Zr2O12 (LLZO) and LLZTO. Using LLZTO/LBO as an electrolyte, the LiNi0.8Co0.1Mn0.1O2/LiFePO4 hybrid solid battery showed an excellent cycling performance with the reversible capacity of 147.8 mA h g 1 at 0.2C for 100 cycles and the capacity retention of 93.8% These results suggest that the consolidation of the grain boundary with LBO is a promising way to achieve an improved electrolyte, LLZO, with higher total Li+ conductivity.
Huilin Xie Chunli Li Wang Hay Kan Maxim Avdeev Chenyou Zhu Zhikun Zhao Chu Xiaorong Daobin Mu Feng Wu
202876641
Distinguishing Bulk and Grain Boundary Transport of a Proton Conducting Electrolyte by Combining Equivalent Circuit Scheme and Distribution of Relaxation Times Analyses
Features of ionic transport across grains and along grain boundaries of solid oxide electrolyte materials play a key role in the efficient application of these materials in electrochemical devices including solid oxide fuel and electrolysis cells, membrane reactors, and electrochemical converters. In the present work, equivalent circuit scheme (ECS) and distribution of relaxation times (DRT) analyses were successfully utilized to distinguish the bulk and grain boundary resistances, both from each other and from the polarization resistance component. Considering a Ag|BCG|Ag symmetrical cell (where BCG BaCe0.9Gd0.1O3 d) as a simple model system, the complex impedance spectra were obtained. Due to the close characteristic parameters (relaxation time and capacitance) exhibited by some electrochemical processes, these spectra cannot be precisely resolved using only an ECS tool, although a joint application of ECS and DRT allowed the spectra to be deconvoluted. As a result, data concerning grain and grain bou.
The Journal of Physical Chemistry C
Julia G Lyagaeva Gennady K Vdovin Dmitry A Medvedev
104408227
Theory for impedance response of grain and grain boundary in solid state electrolyte
Abstract We develop a generic phenomenological theory for the electrochemical impedance response of solid state electrolytes (SSEs) The theory describes dynamics of various physical processes in grain (g) and grain boundary (gb) Leaking capacitor model for the dynamics of ions in grain accounts compositional heterogeneity, ion reorganization and transfer across the surface of the grain. Model for ion relaxation in the grain boundary is determined through generalized electric double layer (EDL) theory over heterogeneous surface (Singh and Kant, 2013) The theory accounts for ion transfer and reorganization in grain boundary has the following components: (i) ions distribution at energetically heterogeneous surface of grain; (ii) space charge layer (SCL) in the grain boundary. Predicted impedance response of SSE evinces three frequency regimes, viz. (i) high frequency regime, attributed to relaxation of ions in grain and grain boundary (SCL) (ii) intermediate frequency regime, related to ion reorganization and transfer across heterogeneous grain and grain boundary (iii) low frequency regime, ascribed to the SSE/metal interface. The model emphasizes that ions encounter energetic heterogeneity in the grain causing distribution of relaxation time with a characteristic exponent gg. Doped grain with aliovalent cations further enhances the structural/energetic heterogeneity and concentration of mobile ions therefore decreases the ion transfer resistance from grain to grain boundary. Doping also enhances the surface concentration of mobile ions at the grain boundary region resulting in enhanced capacitance and prolonged relaxation time of compact layer.
Journal of Electroanalytical Chemistry
Neha Goswami Rama Kant
145835640
Divalent cations modified grain boundary scavenging in samarium doped ceria electrolyte for solid oxide fuel cells
Abstract Grain boundary conductivity of samarium doped ceria electrolyte (SDC) depends on the space charge potential and oxygen vacancy concentration existing at the grain boundary region. Here, we report the effect of co doping 1 mol% divalent alkaline earth metals in samarium doped ceria (Ce0.78Sm0.2A0.01O1.89, [ASDC] A Mg, Ca, Sr, Ba) on the grain boundary conductivity. The increase (Ca2+ Sr2+ Ba2+ or decrease (Mg2+ in lattice parameter in comparison to SDC (0.5445 nm) depends on the ionic radii of the co dopant. The oxygen vacancy concentration of ASDC system, quantified from the Raman spectra, increased from 2.98 x 1021 cm 3 (SDC) to 3.18 x 1021 cm 3. The samples sintered at 1400 degC for 5 h, resulted in a dense electrolyte with a relative density of 98 99% Calcium co doped SDC (CSDC) showed the highest conductivity of 2.04 x 10 3 S/cm at 700 degC with activation energy of 0.90 eV. The oxygen vacancy profile at the space charge layer was found to be higher for CSDC while the potential reduced from 0.24 V (SDC) to 0.18 V. The observed lower space charge potential in co doped SDC, contributed to the enhancement in oxygen vacancy concentration at the space charge layer and increased the grain boundary conductivity. Thus the present study highlights the correlation of space charge potential, oxygen vacancy concentration to grain boundary conductivity and provide a profound insights on the grain boundary understandings for improving the performance of the electrolyte for solid oxide fuel cell application.
Journal of Alloys and Compounds
Sridhar Preethi K Suresh Babu
199642999
Synergistic effect of lithium and calcium for low temperature densification and grain boundary scavenging in samarium doped ceria electrolyte
Abstract A highly dense electrolyte with lower grain boundary resistance is desirable for improving the performance of solid oxide fuel cell. This paper studies the synergistic role of calcium and lithium on the densification and ionic conductivity of samarium doped ceria (SDC) electrolyte. Nanosized powders of compositions, CaxLiySm0.2Ce0.78O2 d (CLSDC, x y 0.02) were prepared by citrate nitrate combustion method and subsequently sintered at 900 degC. A single phase cubic fluorite structure of CeO2 was observed in X ray diffraction analysis. The segregation of the co dopants was identified from Raman spectroscopic analysis and FESEM EDX analysis. The presence of lithium enhanced the densification at 900 degC while calcium improved the grain boundary scavenging. The synergistic effect of an increase in configurational entropy and density in 0.5 mol% Ca and 1.5 mol% Li (0.5CLSDC900) resulted in the highest conductivity of 5.3 x 10 3 S/cm at 800 degC with a scavenging factor of 20.2. Thus the optimum ratio of Li+ and Ca2+ plays a key role in suppressing the ordering of oxygen vacancy and improve the ionic conductivity for its use as an electrolyte for solid oxide fuel cells.
Materials Chemistry and Physics
Preethi Sudarsan Suresh Babu Krishna Moorthy
105393937
Minimizing the Grain Boundary Resistance of Li Ion Conducting Oxide Electrolyte by Controlling Liquid Phase Formation During Sintering
The commercialization of sintered solid state devices using oxide electrolyte is hindered by their low total conductivity, which largely originates from high ionic resistance at grain boundaries (G.
Toyoki Okumura Sou Taminato Tomonari Takeuchi Hironori Kobayashi
233543451
Grain boundary modification in garnet electrolyte to suppress lithium dendrite growth
Abstract Solid state batteries (SSBs) have attracted many attentions due to its higher energy density and improved safety. As one of the most promising solid electrolytes, garnet Li7La3Zr2O12 (LLZO) has achieved significant advances in its cell performance, however, its application in Li metal batteries is still hindered by lithium dendrite growth at voids or grain boundaries inside the solid electrolyte. Herein, a novel grain boundary enhancement strategy was demonstrated by introducing Li6Zr2O7 (LZO) which can be decomposed into Li2O in situ, into Ta doped LLZO (LLZT) The Li2O provides a sufficient inner Li2O atmosphere, achieving none mother powder sintering. The Li2ZrO3 stays at garnet grain boundaries or fills up the pores, which have been shown to effectively suppress the lithium dendrite growth. More importantly, the critical current density (CCD) of the Li LLZT LZO Li symmetric cell achieved as high as 1.4 mA cm 2 at 25 degC and 2.0 mA cm 2 at 60 degC, and the long term lithium cycling remained stable over 2000 h at 0.3 mA cm 2. Moreover, the Li S battery maintained high discharge capacity of 816 mAh g 1 after 200 cycles at 0.5C. Therefore, our work provides a facile and effective strategy to prepare a safety enhanced electrolyte for future applications of SSBs.
Chujun Zheng Yadong Ruan Jianmeng Su Zhen Song Tongping Xiu Jun Jin Michael E Badding Zhaoyin Wen