A3Ti5NbO14 (A = H, Li and K) family: ionic exchange, physical and electrochemical properties.

A new layered titanoniobate, Li3Ti5NbO14, a member of the AxM2nO4n+2 family, has been synthesized using a molten salt reaction between H3Ti5NbO14 and an eutectic mixture of LiOH and LiNO3. This compound crystallizes in the P21/m space group with a = 9.273(15) Å, b = 3.788(6) Å, c = 8.871(3) Å, and ß = 114.33(1)°, as determined by 3D electron diffraction single crystal analysis. It exhibits [Ti5NbO14]3- layers similar to K3Ti5NbO14, but differs from the latter by a 'parallel configuration' of its [Ti5NbO5]3- ribbons between the two successive layers. The topotactic character of the reaction suggests that exfoliation plays a prominent role in the synthesis of this new form. This new phase intercalates reversibly 2 lithium through a first-order transformation leading to a capacity of 100 mA h g-1 at a potential of 1.67 V vs. Li/Li+.

Effect of the boron element in a Li-P-S system.

Lithium-ion batteries are nowadays a mature technology for energy storage. However, some safety problems have been identified during their operation in high power applications such as fire incidents in electric vehicles. The most promising solution to improve the safety of lithium-ion batteries is replacing the current organic liquid based electrolytes with solid electrolytes. In this context, new solid electrolytes having chemical and electrochemical stability with high ionic conductivity need to be discovered. Therefore, in the present study, a new LGPS-type structural domain is highlighted for the Li-B-P-S system. Ionic conductivities of up to 10-4 S cm-1 have been achieved for prepared solid electrolytes in the Li-B-P-S system, and higher stability against lithium metal as compared to Li10GeP2S12. These solid electrolytes also show better electrochemical characteristics in all solid-state batteries.

Facile synthesis and phase stability of Cu-based Na2Cu(SO4)2·xH2O (x = 0-2) sulfate minerals as conversion type battery electrodes.

Mineral exploration forms a key approach for unveiling functional battery electrode materials. The synthetic preparation of naturally found minerals and their derivatives can aid in designing of new electrodes. Herein, saranchinaite Na2Cu(SO4)2 and its hydrated derivative kröhnkite Na2Cu(SO4)2·2H2O bisulfate minerals have been prepared using a facile spray drying route for the first time. The phase stability relation during the (de)hydration process was examined synergising in situ X-ray diffraction and thermochemical studies. Kröhnkite forms the thermodynamically stable phase as the hydration of saranchinaite to kröhnkite is highly exothermic (-51.51 ± 0.63 kJ mol-1). Structurally, kröhnkite offers a facile 2D pathway for Na+ ion migration resulting in 20 times higher total conductivity than saranchinaite at 60 °C. Both compounds exhibited a conversion redox mechanism for Li-ion storage with the first discharge capacity exceeding 650 mA h g-1 (at 2 mA g-1vs. Li+/Li) upon discharge up to 0.05 V. Post-mortem analysis revealed that the presence of metallic Cu in the discharged state is responsible for high irreversibility during galvanostatic cycling. This study reaffirms the exploration of Cu-based polyanionic sulfates, which while having limited (de)insertion properties, can be harnessed for conversion-based electrode materials for batteries.