Recent trends to overcome limitations of state-of-the-art Li-ion batteries are often connected with such electrochemical systems as lithium-metal-polymer, lithium-sulfur or lithium-air. In such systems various high capacity cathodes are coupled with lithium metal anode offering much higher values of specific energy than those obtained in lithium-ion intercalation electrodes. However, prior practical implementation of such electrochemical designs, a number of technical challenges have to be solved. One of the most substantial problems is prevention of metallic lithium reactions with components either produced or supplied in cathode. The most promising way to guard lithium from undesirable interactions is utilization of solid electrolyte membranes permeable only for lithium ions and isolating anodic and cathodic parts of the battery. Materials based on NASICON-type solid ionic conductors Li1+xAlxGe2-x(PO4)3 are promising solution due to their high ionic conductivity, reasonable chemical and electrochemical stability. Here we propose a glass-ceramic approach to produce thin gas-tight electrolyte membranes instead of thick ceramic layers. However, the corresponding glass system tends to crystallize heterogeneously leading to cavities in the volume of resulting glass-ceramic membranes that affects the battery performance. Adding a nucleation agent, such as Y2O3, enables to depress heterogeneous crystallization and to induce controllable uniform crystallization on yttrium-containing particles formed in the glass volume. Solid-state NMR spectroscopy provides evidence that yttria has fulfilled the mission of the nucleation agent and reduced residual glass fraction after crystallization without modification of the crystalline phase (LAGP) chemical composition. Quantum-chemical calculations of NMR parameters and an intensity estimate based on assumption of random distribution of Al and Ge octahedra in the LAGP structure provide a good agreement with the experimental data. Furthermore, glass crystallization time has been optimized towards enhanced conductivity of LAGP glass-ceramic reaching 0.5 S×cm-1 at room temperature. Anomalous behavior of conductivity as a function of crystallization time is explained in terms of particle size and grain-boundary contribution in total conductivity. Gas permeability tests have been conducted to prove that the resulting glass-ceramic membranes are gas-tight and can be used to isolate anode and cathode.

Controllable uniform crystallization towards improved performance in glass-ceramic Li1+xAlxGe2-x(PO4)3 electrolyte membrane

249th National Meeting (2015)

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