A New Triclinic Phase Na₂Ti₃O₇ Anode for Sodium‐Ion Battery

Abstract

A new phase Na 2 Ti 3 O 7 compound is synthesized by solid-state method for the first time, which is verified to belong to the triclinic structure in P-1 space group. Compared to the conventional monoclinic Na 2 Ti 3 O 7 (m-NTO), in P2 1 /m1 space group, the triclinic Na 2 Ti 3 O 7 (t-NTO) possesses a shorter O-O band in the distorted TiO 6 octahedron, which accounts for more smooth Na + transport channels and a more stable layered structure with smaller fluctuation. The experimental results show that the t-NTO keeps a low charge potential plateau at 0.3 V compared to the m-NTO, but with much promoted structure resilience. It delivers a capacity retention of 94.7%, far exceeding the 25.7% of the m-NTO upon decades of cycles. In situ X-ray diffraction reveals that the conventional m-NTO experiences an irreversible phase transition during insertion/de-insertion of Na + , while the new t-NTO can recover its structure reversibly after discharge and charge, which is consistent with its improved cycling performance. The results demonstrate a new t-NTO anode and provide a new understanding for the phase diversity of sodium-ion battery materials.

A Flexible Humidity Sensor with Wide Range, High Linearity, and Fast Response Based on Ultralong Na2Ti3O7 Nanowires

“…Among the inorganic candidates, Na 2 Ti 3 O 7 NWs stand out as a layered material because the large interlayer distance (∼8.4 Å) grants the nanowires with better mechanical flexibility . Synthesis of Na 2 Ti 3 O 7 nanowires by a simple hydrothermal process has been reported as early as 2004 and used in the fields of photocatalysis, energy storage, and a titanate nanowire synthesis template. − In 2008, nanowires were first found to have a good impedance humidity response, which was confirmed again in 2013 by Chengyan Xu et al , Previous studies exhibit promising sensing performances in the sensing range (11–95% RH in AC), fast response/recovery (5/6 s), and high sensitivity (impedance changes of 3 orders of magnitude with humidity varying from 11% RH to 95% RH). The excellent humidity sensing performance mainly results from the layered structure of Na 2 Ti 3 O 7 with large layer spacing, which makes sodium ion migration barrier smaller and sodium ion movement more active and greatly shortens the response time.…”

Sodium diffusion and dynamics in Na2Ti3O7: neutron scattering and ab initio simulations

“…Oxides-based metal-ion conductors have attracted attention 1,2 due to their easy synthesis, low cost, and high stability in variable temperature/pressure range. An important material, Na 2 Ti 3 O 7 has been extensively studied [24][25][26][27][28][29][30][31] for its usage as an anode material. It is known to be a very promising anode compound, especially when it is mixed with carbonaceous materials 32 .…”

Advanced Characterization Techniques Paving the Way for Commercialization of Low‐Cost Prussian Blue Analog Cathodes

“…For the anode, hard carbon is regarded as the most suitable anode material when coupled with PBAs to make full cells compared with other types of negative electrode materials. [135][136][137][138] Numerous organics and biomass materials are good sources for hard carbon, which have very low raw material costs and are environmentally friendly. Furthermore, hard carbon anode with high specific capacity and a low-voltage electrochemical profile is capable of achieving higher capacity and working voltage in full cells, thus obtaining higher energy density.…”