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Abstract Metallic Li anodes are key to reaching high energy densities in next-generation solid-state batteries, however, major problems are the non-uniform deposition of Li at the interface and the penetrative power of Li metal during operation, which cause failure of the ceramic electrolyte, internal short-circuits and a premature end of battery life. In this work, we explore the anode-electrolyte interface instability of a Li metal-garnet electrolyte system during Li electrodeposition, and its implications for mechanical fracture, Li metal propagation, and electrolyte failure. The degradation mechanism was followed step-by-step during in-operando electrochemical cycling using optical and scanning electron microscopy. High amounts of Li electrodeposition in a localized zone of the interface lead to ceramic fracture followed by an electrode-to-electrode electrical connection via a conductor Li metal filament. This work enables deeper understanding of battery failure modes in all-solid-state batteries containing a ceramic electrolyte membrane. Graphical abstract Image 1 Highlights • In-operando visualization of Li metal propagation in a ceramic electrolyte. • Mechanisms of mechanical failure in a garnet electrolyte. • Li electrodeposition leading to short circuit via soft dendrite formation. • Limitation of all-solid-state batteries with a ceramic membrane. [ABSTRACT FROM AUTHOR]

Abstract: Sodium-ion transfer through the interface between ceramic and organic electrolytes was studied by AC impedance spectroscopy. Na3Zr1.88Y0.12Si2PO12 (NASICON) and Na-β″-alumina were used as ceramic electrolytes, and propylene carbonate (PC) and dimethyl sulfoxide (DMSO) containing 0.05moldm−3 NaCF3SO3 were used as organic electrolytes. The semi-circle ascribed to interfacial charge transfer resistance (R ct ) was observed. The activation energies for sodium-ion transfer at the interface between ceramic and organic electrolytes were evaluated by the temperature dependency of R ct . As a result, the activation energies depended on the ceramic electrolytes but not on the solvents. These results suggest that sodium-ion transfer from ceramic to organic electrolytes should be responsible for the activation energies, which is contrary to the case in a lithium-ion transfer system. Based on these results, the mechanism of interfacial sodium-ion transfer was discussed. [Copyright &y& Elsevier]

Abstract: An all solid-state rechargeable lithium battery was successfully fabricated using a ceramic electrolyte and a thin film technique. A polymer-modified sol–gel method was applied in order to prepare the electrode-coated ceramic electrolyte. Li4Ti5O12 known for its outstanding electrochemical performances and the partially crystallized glass ceramics, LiTi2(PO4)3–AlPO4 were adopted as electrode and electrolyte materials, respectively. The all solid-state battery cell constructed with lithium metal, PMMA buffer, and electrode-coated ceramic electrolyte was electrochemically evaluated with ac impedance, cyclic voltammetry, and discharge–charge test. The impedance of the interface between Li4Ti5O12 film and the solid electrolyte showed a relatively low resistance of ∼110Ωcm−2 at 1.60V. Highly reversible sharp redox peaks were observed at around 1.55V from cyclic voltammograms, and these were still clear even at a high scan rate of 3mVs−1, indicating a fast electrochemical response. A charge–discharge experiment showed an excellent reversibility of the cell but a relatively smaller discharge capacity of 100.49mAhg−1 at C/5 than theoretical one of 175mAhg−1. This may be due to formation of an interlayer at the interface, which may be caused by chemical reaction between Li4Ti5O12 and the ceramic electrolyte during a firing step during preparation. In spite of the undesirable side-reaction, the ceramic electrolyte was successfully applied to the solid-state rechargeable lithium battery by means of a thin film technique using the polymer-modified sol–gel method, through increasing the interfacial contact area, i.e. reducing the interfacial resistance. [Copyright &y& Elsevier]

Twenty percentage of Gd2O3-doped ceria solid solution has been prepared as an electrolyte for solid oxide fuel cells via the conventional mixed-oxide method from high-purity commercial CeO2 and Gd2O3. The solubility of Gd2O3 in CeO2 in the temperature range of 1300–1700 °C has been examined based on the measurements of the lattice parameter. It is found that the dissolution of Gd2O3 in CeO2 is completed at 1600 °C for 5 h. The addition of Gd2O3 increases sintering temperature, retards densification, and also depresses grain growth as compared with undoped CeO2. The sample sintered at 1550 °C for 5 h has the highest grain boundary conductivity, while the highest grain interior conductivity is achieved for the sample sintered at 1600 °C for 5 h. It is also observed that below 500 °C, the maximum total conductivity is exhibited by the former sample, but above 500 °C, for the latter one. [Copyright &y& Elsevier]

We analyse the initiation of void growth in the Li electrode during the stripping phase of an Li-ion cell with a solid (ceramic) electrolyte. We first show that standard Butler-Volmer kinetics fails to predict the observed void formation. This motivated us to recognise that void initiation/growth involves power-law creep of the Li electrode that is linked to the motion of dislocations. We show, via thermodynamic considerations, that dislocations significantly affect the interface kinetics and use variational principles to develop a modified form of Butler-Volmer kinetics for the interface flux that is associated with a deforming Li electrode. Numerical solutions are presented for the coupled flux of Li + in a single-ion conductor solid electrolyte and the associated creep deformation of the Li electrode for an imposed stripping current. This involves solution of a Laplace equation for flux in the electrolyte and the nonlinear Stokes flow equations for a power-law creeping solid in the electrode. These two domains are coupled together via the modified Butler-Volmer relation. The calculations predict that an increasing stack pressure needs to be exerted with increasing cell current to avoid the initiation of void growth and are in excellent quantitative agreement with measurements for an Li/LLZO/Li cell. Image 1 • A framework is developed for thermodynamics of a deforming Li electrode. • Dislocations in electrode are shown to reduce the interfacial resistance. • Li creep around an imperfection is shown to enhance flux focussing. • Framework used to analyse initiation of void growth during stripping. • Predictions of critical stack pressure are in excellent agreement with measurements. [ABSTRACT FROM AUTHOR]

We idealise dendrite growth in a ceramic electrolyte by climb of a thick edge dislocation. Growth of the dendrite occurs at constant chemical potential of Li + at the dendrite tip: the free-energy to fracture and wedge open the electrolyte is provided by the flux of Li + from the electrolyte into the dendrite tip. This free-energy is dependent on the Li + overpotential at the dendrite tip and is thereby related to the imposed charging current density. The predicted critical current density agrees with measurements for Li/LLZO/Li symmetric cells: the critical current density decreases with increasing initial length of the dendrite and with increasing electrode/electrolyte interfacial ionic resistance. The simulations also reveal that a void on the cathode/electrolyte interface locally enhances the Li + overpotential and significantly reduces the critical current density for the initiation of dendrite growth. • A dislocation mode proposed for dendrite propagation in solid electrolytes. • Propagation of the dendrite at constant chemical potential of Li +. • Flux of Li + into the dendrite tip provides the free-energy to drive propagation. • Voids on the plating electrode surface reduce the critical current densities. • The predicted critical currents are in good agreement with measurements. [ABSTRACT FROM AUTHOR]