Yuyu Li

Graphene-Roll-Wrapped Prussian Blue Nanospheres as a High-Performance Binder-Free Cathode for Sodium-Ion Batteries

Sodium iron hexacyanoferrate (Fe-HCF) has been proposed as a promising cathode material for sodium-ion batteries (SIBs) because of its desirable advantages, including high theoretical capacity (∼170 mAh g-1), eco-friendliness, and low cost of worldwide rich sodium and iron resources. Nonetheless, its application faces a number of obstacles due to poor electronic conductivity and structural instability. In this work, Fe-HCF nanospheres (NSs) were first synthesized and fabricated by an in situ graphene rolls (GRs) wrapping method, forming a 1D tubular hierarchical structure of Fe-HCF NSs@GRs. GRs not only provide fast electronic conduction path for Fe-HCF NSs but also effectively prevent organic electrolyte from reaching active materials and inhibit the occurrence of side reactions. The Fe-HCF NSs@GRs composite has been used as a binder-free cathode with a capacity of ∼110 mAh g-1 at a current density of 150 mA g-1 (∼1C), the capacity retention of ∼90% after 500 cycles. Moreover, the Fe-HCF NSs@GRs cathode displays a super high rate capability with ∼95 mAh g-1 at 1500 mA g-1 (∼10C). The results suggest that the 1D tubular structure of 2D GRs-wrapped Fe-HCF NSs is promising as a high-performance cathode for SIBs.

High valence Mo-doped Na3V2(PO4)3/C as a high rate and stable cycle-life cathode for sodium battery

NASICON-structure Na3V2(PO4)3 (NVP) is a potential cathode material for sodium ion battery, which is still confronted with low rate performance because of its poor conductivity. To address this problem, high-valance Mo6+ ion was introduced into NVP. The crystal structure, electrochemical performances, sodium ion diffusion kinetics and ion transfer mechanism of high valence Mo-doped Na3−5xV2−xMox(PO4)3/C (0 < x < 0.04) were investigated. X-ray diffraction, electron microscopy and XPS data confirmed high purity NASICON phosphate phases. The Na ion diffusion process was identified through CV measurement, which clearly shows rapid sodium ion transportation in the Mo-doped NASICON materials. Moreover, DFT calculations proved that Na ion diffusion is promoted by Mo doping. Benefiting from the superior Na ion kinetics, Na2.9V1.98Mo0.02(PO4)3 exhibited a performance of 90 mA h g−1 at 10C and preserved 83.5% of the original capacity after 500 cycles. Our studies demonstrate that high-valence Mo doped Na3V2(PO4)3/C is a promising cathode material for sodium ion batteries with super-high rate capability and stable cycle life.

Al doping effects on LiCrTiO4 as an anode for lithium-ion batteries

Al-Doped LiCrTiO4 anode materials are successfully synthesized by a conventional solid-state reaction. Their structural and electrochemical properties are systematically investigated. With increasing the Al doping level (x), the lattice parameters of LiAlxCr1−xTiO4 get smaller. Meanwhile, asymmetric polarization was significantly reduced during the charge/discharge process, in contrast to an enhanced compatibility of electrode materials with organic electrolyte. The Al-doped LiAl0.2Cr0.8TiO4 anode can still keep a discharge capacity of 123 mA h g−1 at 1C for 100 cycles and 109 mA h g−1 at 2C. More importantly, the Al-doped LiAl0.2Cr0.8TiO4 anode exhibits remarkable electrochemical properties at a high-temperature of 60 °C with a very stable capacity of about 145 mA h g−1 at 1C, and is promising as a high-performance anode.

A P2-Type Layered Superionic Conductor Ga-Doped Na2Zn2TeO6 for All-Solid-State Sodium-Ion Batteries

Here, a P2-type layered Na2 Zn2 TeO6 (NZTO) is reported with a high Na+ ion conductivity ≈0.6×10-3 u2005Su2009cm-1 at room temperature (RT), which is comparable to the currently best Na1+n Zr2 Sin P3-n O12 NASICON structure. As small amounts of Ga3+ substitutes for Zn2+ , more Na+ vacancies are introduced in the interlayer gaps, which greatly reduces strong Na+ -Na+ coulomb interactions. Ga-substituted NZTO exhibits a superionic conductivity of ≈1.1×10-3 u2005Su2009cm-1 at RT, and excellent phase and electrochemical stability. All solid-state batteries have been successfully assembled with a capacity of ≈70u2009mAhu2009g-1 over 10u2005cycles with a rate of 0.2u2005C at 80u2009°C. 23 Na nuclear magnetic resonance (NMR) studies on powder samples show intra-grain (bulk) diffusion coefficients DNMR on the order of 12.35×10-12 u2005m2 u2009s-1 at 65u2009°C that corresponds to a conductivity σNMR of 8.16×10-3 u2005Su2009cm-1 , assuming the Nernst-Einstein equation, which thus suggests a new perspective of fast Na+ ion conductor for advanced sodium ion batteries.

New P2-Type Honeycomb-Layered Sodium-Ion Conductor: Na2Mg2TeO6

A novel solid sodium-ion conductor, Na2Mg2TeO6 (NMTO) with a P2-type honeycomb-layered structure, has been synthesized for the first time by a simple solid-state synthetic route. The conductor of NMTO exhibits high conductivity of 2.3 × 10-4 S cm-1 at room temperature (RT) and a large electrochemical window of ∼4.2 V (versus Na+/Na). The conductor is remarkably stable, both in the ambient environment and within its metallic Na anode. This facile sodium-ion conductor displays potential for use in all-solid-state sodium-ion batteries (SS-SIBs).