Ti 2 Nb 10 O 29 has recently been reported as a promising anode material for lithium-ion batteries. However, its poor electronic conductivity and insufficient Li + -ion diffusion coefficient significantly limit its rate capability. To tackle this issue, a strategy combining nanosizing and crystal-structure modification is employed. Ti 2 Nb 10 O 29– x mesoporous microspheres with a sphere-size range of 0.5–4 μm are prepared by a one-step solvothermal method followed by thermal treatment in N 2 . These Ti 2 Nb 10 O 29– x mesoporous microspheres exhibit primary nanoparticles , a large specific surface area (22.9 m 2 g −1 ) and suitable pore sizes, leading to easy electron/Li + -ion transport and good interfacial reactivity. Ti 2 Nb 10 O 29– x shows a defective shear ReO 3 crystal structure with O 2− vacancies and an increased unit cell volume, resulting in its increased Li + -ion diffusion coefficient. Besides Ti 4+ and Nb 5+ ions, Ti 2 Nb 10 O 29– x comprises Nb 4+ ions with unpaired 4 d electrons, which significantly increase its electronic conductivity. As a result of these improvements, the Ti 2 Nb 10 O 29– x mesoporous microspheres reveal superior electrochemical performances in term of large reversible specific capacity (309 mAh g −1 at 0.1 C), outstanding rate capability (235 mAh g −1 at 40 C) and durable cyclic stability (capacity retention of 92.1% over 100 cycles at 10 C).
Rational design & modulation of ion/electron transfer paths are critical for achieving high-performance anode materials for lithium ion batteries . In this work, we first time realize smart assembly of oxygen vacancy modulated titanium niobium oxide (Ti 2 Nb 10 O 29-x , TNO x ) onto highly conductive bacterial cellulose carbon (BCC) forming BCC/TNO x electrode through a facile solvothermal-annealing method. BCC consists of interlinked (N, S & P) co-doped carbon fibres uniformly decorated with TNO x nanoparticles . Impressively, the introduction of oxygen vacancy can effectively enhance the internal ion/electron transfer in TNO x and enhancement effect is elaborated by synchrotron radiation technology (XANES and XAFS) and DFT calculation. Meanwhile, with the aid of conductive BCC skeleton, the external ion/electron transfer path on TNO x is also greatly improved leading to better reaction kinetics. The synergistic dual internal plus external modulation on transfer path show positive advantages including smaller band gap with better electrical conductivity , and larger lattice parameters with faster ion/electron transfer. Accordingly, the BCC/TNO x electrode is endowed with outstanding lithium ion storage performance with high-rate capability (281 mA h g −1 at 5 C, and 160.5 mA h g −1 at 40 C). Our finding provides valuable insights into design of other advanced electrodes via dual transfer path modulation strategy.
Nan Luo,Guoliang Chen,Yunfan Shang,Suyang Lu,Jun Mei,Changyu Tang,Zhoukun He,Wenwen Zeng,Haoran Zhan
Ti 2 Nb 1 0 O 2 9 (TNO) is considered as a potential anode material due to its high capacity/power density and reliable safety. However, its poor electronic conductivity restricts its rate performance, which is important for its application in electric vehicles (EVs). In this study, we fabricated a hybrid of Ti 2 Nb 1 0 O 2 9 − x /holey-reduced graphene oxide (TNO x /HRGO) by a two-step method. In the structure of TNO x /HRGO, TNO x microspheres with oxygen vacancies are wrapped by gossamer-like HRGO. The oxygen vacancies of TNO x and the high conductivity of HRGO can effectively enhance the electronic conductivity of the TNO x /HRGO hybrid, and the HRGO holes are beneficial for the transmission of lithium-ion ( Li + ). The synergy effect of above features improves the rate performance of the TNO x /HRGO hybrid. In addition, the existence of HRGO can buffer volume expansion during the insertion processes of Li + , which can improve cyclic stability of the TNO x /HRGO hybrid. Consequently, the TNO x /HRGO electrode has excellent lithium-ion storage capacity, with high-rate performance (242 mAh/g at 10 ∘ C, 225 mAh/g at 20 ∘ C and 173 mAh/g at 40 ∘ C) and excellent cyclic stability (98.0% capacity retention after 300 cycles at 10 ∘ C). This work reveals that TNO x /HRGO can be a potential anode material for high-rate-performance lithium-ion storage.
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