ABSTRACT
Sodium-ion batteries (SIBs) are becoming promising candidates for energy storage devices due to the low cost, abundant reserves, and excellent electrochemical performance. As the most important unit, layered cathodes attract much attention, where honeycomb-layered-oxides (HLOs) manifest outstanding structural stability, high redox potential, and long-life electrochemistry. Here, recent progress on HLOs as well as Na3 Ni2 SbO6 and Na3 Ni2 BiO6 as two representative materials are introduced, and the crystal and electronic structure, electrochemical performance, and modification strategies are summarized. The advanced high nickel HLOs are highlighted toward development of state-of-the-art sodium-ion batteries. This review would deepen the understanding of superstructure in layered oxides, as well as structure-property relationship, and inspire more interest in high output voltage, long lifespan sodium-ion batteries.
ABSTRACT
A new layered C2/m oxide, Li2Ni0.2Mn0.4Ru0.4O3 (LNMR), is introduced as a cathode for lithium-ion batteries, which undergoes a low volume variation of 1.5% in the voltage window of 2.0-4.6 V studied via in situ X-ray diffraction. Compared with the contrast sample Li2MnO3, LNMR displays superior capacity, a more stable capacity retention rate, and higher energy density and average discharge voltage.
ABSTRACT
Sodium dendrite growth is responsible for short circuiting and fire hazard of metal batteries, which limits the potential application of sodium metal anode. Sodium dendrite can be effectively suppressed by applying mechanically robust electrolyte in battery systems. Herein, a composite gel polymer electrolyte (GPE) is designed and fabricated, mainly consisting of graphene oxide (GO) and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). With the addition of an appropriate amount of GO content, the compressive Young's modulus of 2 wt% GO+PVDF-HFP (2-GPH) composite GPE is greatly enhanced by a factor of 10, reaching 2.5 GPa, which is crucial in the suppression of sodium dendrite growth. As a result, uniform sodium deposition and ultralong reversible sodium plating/stripping (over 400 h) at high current density (5 mA cm-2 ) are achieved. Furthermore, as evidenced by molecular dynamics simulation, the GO content facilitates the sodium ion transportation, giving a high ionic conductivity of 2.3 × 10-3 S cm-1 . When coupled with Na3 V2 (PO4 )3 cathode in a full sodium metal battery, a high initial capacity of 107 mA h g-1 at 1 C (1 C = 117 mA g-1 ) is recorded, with an excellent capacity retention rate of 93.5% and high coulombic efficiency of 99.8% after 1100 cycles.
