Synthesis of Hierarchically Porous SnO₂ Microspheres and Performance Evaluation as Li-Ion Battery Anode by Using Different Binders

We have prepared nanoporous SnO₂ hollow microspheres (HMS) by employing the resorcinol-formaldehyde (RF) gel method. Further, we have investigated the electrochemical property of SnO₂–HMS as negative electrode material in rechargeable Li-ion batteries by employing three different binderspolyvinylidene difluoride (PVDF), Na salt of carboxy methyl cellulose (Na-CMC), and Na-alginate. At 1C rate, SnO₂ electrode with Na-alginate binder exhibits discharge capacity of 800 mA h g^–1, higher than when Na-CMC (605 mA h g^–1) and PVDF (571 mA h g^–1) are used as binders. After 50 cycles, observed discharge capacities were 725 mA h g^–1, 495 mA h g^–1, and 47 mA h g^–1, respectively, for electrodes with Na-alginate, Na-CMC, and PVDF binders that amounts to a capacity retention of 92%, 82%, and 8% . Electrochemical impedance spectroscopy (EIS) results confirm that the SnO₂ electrode with Na-alginate as binder had much lower charge transfer resistance than the electrode with Na-CMC and PVDF binders. The superior electrochemical property of the SnO₂ electrode containing Na-alginate can be attributed to the cumulative effects arising from integration of nanoarchitecture with a suitable binder; the hierarchical porous structure would accommodate large volume changes during the Li interaclation–deintercalation process, and the Na-alginate binder provides a stronger adhesion betweeen electrode film and current collector

Synthesis, Structure, and Electrochemical Properties of the Layered Sodium Insertion Cathode Material: NaNi_¹/₃Mn_¹/₃Co_¹/₃O₂

A layered phase, NaNi_¹/₃Mn_¹/₃Co_¹/₃O₂ (NaNMC), isostructural to NaCoO₂ has been synthesized. Stoichiometric NaNMC crystallizes in a rhombohedral R3̅m space group where Na is in an octahedral environment (O3-Type). Galvanostatic cycling on NaNMC vs Na cell indicated a reversible intercalation of 0.5 Na, leading to a capacity of 120 mAh·g^–1 in the voltage range of 2–3.75 V and indicating its possible application in Na-ion batteries. The electrochemically driven Na insertion/deinsertion in NaNMC is associated with several phase transitions and solid solution regimes which are studied by <i>in situ</i> X-ray diffraction. Sodium deinsertion in Na_<i>x</i>NMC resulted in sequential phase transitions composed of biphasic and monophasic domains. The composition driven structural evolution in Na_<i>x</i>NMC follows the sequence O3 ⇒ O1 ⇒ P3 ⇒ P1 phases with an increased ‘<i>c</i>’ parameter, while the ‘<i>a</i>’ parameter remains almost unchanged