| Li2O-Al2O3-（Ge,Ti）O2-P2O5（LAGTP） glass ceramics are thought to be candidateelectrolytes for all solid state lithium ionic battery because of their high lithium ionicconductivity, excellent mechanical strength and electrochemical stability. So far thereare some unsolved problem such as the crystal separation mechanism, lithium ionicconducting channel, relationship between conductivity and the heat treatmentparaments and the performances of glass ceramics assembled in lithium ionic battery.The above problems has been exhaustive studied in this thesis and the main results aresummarized as follows:1. The influence of crystallization paraments on phases’ transformation, thecrystal growth and conductivity of Li1.5Al0.5Ge1.5（PO4）3glass ceramics were carriedout, respectively. The highest conductivity (5.9×10-4S/cm) at room temperature wasobtained for the specimen crystallized at850°C, with uniform crystals and densemicrostructure.2. The lithium ionic conducting mechanism was studied in this thesis. There aretwo kinds of Li+conducting channels in LAGP glass ceramics. The first channel islong-narrow shape in space and is parallel with the c axis of LiGe2（PO4）3phase. Thesecondary channel is columnar in shape and is parallel with the c axis of R3R-AlPO4phase. In major crystal phase LiGe2（PO4）3phase, there are two occupy sites for Liatom. The Li（S1） atom can move freely in the conducting channel, forming theconductivity. However, Li（S2） atom just can vibrate nearby it’s original site, with nocontribution to the conductivity of glass ceramics.3. The crystallization kinetics, crystal phase’s components, microstructures andconductivities of Li1.5Al0.5（Ge1-yTiy）1.5（PO4）3（y=01） glass ceramics were studied,respectively. With increasing "y" value, the major conducting phase of glass ceramicschanged from LiGe2（PO4）3to LiTi2（PO4）3, the minor phase changed fromun-conducting C121-AlPO4to conducting R3R-AlPO4, the conductivity increasedfrom5.9×10-4S/cm to8.8×10-4S/cm, the value of Avrami index （n） decreased from3to1and the activation energy of crystallization （Ec） decreased gradually from313KJ/mol to276KJ/mol, respectively. That indicated the change from simultaneouslythree dimension to one dimension for crystal phases growth.4. The results showed that the influence factors on Li1.5Al0.5Ge1.5（PO4）3glassceramics’ conductivity follows the sequence: the relative content percentage of major phase> the average grain size of crystal phases> the porosity percentage. A functionrelationship between conductivity and the heat treatment parameters was proposedfirstly: σ（β, T, t）=5.66+0.06β+0.13T-0.03t-0.18βt-0.16β2-0.22T2-0.13t2, providingtheoretical supervision to fabricate great performance of glass ceramics.5. The Li+conductivities of Li1.5Al0.5Ge1.5（PO4）3glass ceramics were no lessthan10-4S/cm in the measure temperatures range from-25°C to210°C, with wideelectrochemical window （07V） and great interfacial compatibility with lithiummetals active substance. The excellent charge and discharge performance of all solidstate lithium battery assembled with LAGP glass ceramics suggested that the glassceramics have great potential applications in both military and civilian areas.6. Spark Plasma Sintering （SPS） has been employed to prepare large size, greatdense and high conductivity of Li2O-Al2O3-TiO2-P2O5（LATP） glass ceramics. Themaximum conductivity of glass ceramics was obtained at6.7×10-4S/cm whensintering temperature was650°C.It is solved by the above mention research that the core issue of relationshipamong “the optimization of components and heat-treated schedules---microscopicstructures---the electric propertiesâ€. With regard to “the Li+conducting channelstructures, the mechanism of crystallization, the establishment of relationship betweenconductivity and crystallization paraments, the battery service performance assembledby LAGP electrolyteâ€, the present thesis has such a certain innovation that it could beuseful for reference on studying the fast lithium ionic conducting materials. |
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