Insights into Formation and Li‐Storage Mechanisms of Hierarchical Accordion‐Shape Orthorhombic CuNb₂O₆ toward Lithium‐Ion Capacitors as an Anode‐Active Material

Abstract

The orthorhombic CuNb2O6 (O–CNO) is established as a competitive anode for lithium‐ion capacitors (LICs) owing to its attractive compositional/structural merits. However, the high‐temperature synthesis (>900 °C) and controversial charge‐storage mechanism always limit its applications. Herein, we develop a low‐temperature strategy to fabricate a nano‐blocks‐constructed hierarchical accordional O–CNO framework by employing multilayered Nb2CTx as the niobium source. The intrinsic stress‐induced formation/transformation mechanism of the monoclinic CuNb2O6 to O–CNO is tentatively put forward. Furthermore, the integrated phase conversion and solid solution lithium‐storage mechanism is reasonably unveiled with comprehensive in(ex) situ characterizations. Thanks to its unique structural merits and lithium‐storage process, the resulted O–CNO anode is endowed with a large capacity of 150.3 mAh g−1 at 2.0 A g−1, along with long‐duration cycling behaviors. Furthermore, the constructed O–CNO‐based LICs exhibit a high energy (138.9 Wh kg−1) and power (4.0 kW kg−1) densities with a modest cycling stability (15.8% capacity degradation after 3000 consecutive cycles). More meaningfully, the in‐depth insights into the formation and charge‐storage process here can promote the extensive development of binary metal Nb‐based oxides for advanced LICs.

Achieving High-Rate and Durable Sodium Storage through Confined Construction of NiSe2 Particles Embedded in Porous N-Doped Carbon Spheres

“…Moreover, the GITT test was performed to compare the sodium diffusion kinetics in the NiSe 2 /NC and NiSe 2 electrodes. 63,64 Based on the GITT results, the D Na + values could be evaluated according to the simplified equation as follows + value of NiSe 2 /NC (1.17 × 10 −13 cm 2 s −1 ) is much higher than that of NiSe 2 (8.7 × 10 −14 cm 2 s −1 ) during the whole process of sodiation and desodiation, further confirming the faster Na + diffusion kinetics in the NiSe 2 /NC, in good accordance with the EIS results.…”

“…Moreover, the GITT test was performed to compare the sodium diffusion kinetics in the NiSe 2 /NC and NiSe 2 electrodes. , Based on the GITT results, the D Na + values could be evaluated according to the simplified equation as follows D Na + = 4 π τ ( m normalb V normalm M normalb S ) 2 ( Δ E normals Δ E τ ) 2 where τ, m b , M b , V m , and S refer to the time relaxation, mass loading of active material, molar mass, molar volume, and surface area of electrode, while Δ E s and Δ E τ represent the voltage change at the steady-state, and voltage change during the constant current pulse. Figure F shows the variations in D Na + values for NiSe 2 /NC and NiSe 2 under different states.…”

Solution Combustion Synthesis of Submicron-Sized Titanium Niobium Oxide Anodes for High-Rate and Ultrastable Lithium-Ion Batteries

“…Figure h,i illustrates the typical GITT curves during the initial lithiation and delithiation processes. The apparent Li + diffusion coefficients at different discharge/charge states were calculated using the following equation (eq ), based on Fick’s second law , : D Li = 4 π true( m B V m M B S true) 2 true( normalΔ E s normalΔ E τ true) 2 ( τ ≤ L 2 D Li ) …”

Internal and External Cultivation Design of Zero‐Strain Columbite‐Structured MNb2O6 toward Lithium‐Ion Capacitors as Competitive Anodes

“…Synthesis of MNb 2 O 6 Samples: Typically, 5 mmol of m-Nb 2 CT x , which was fabricated with the developed method before, [29] was added into 40 mL of ethanol with gentle stirring. Thereafter, 5 mmol of CdCl Materials Characterization: Crystal phases and compositions of resultant samples were characterized by X-ray diffraction (XRD, Rigaku-TTRIIItype, Cu K𝛼, 𝜆 = 0.15 418 nm, Japan), X-ray photoelectron spectrometer (XPS, Phi5000), Raman spectroscopic (Lab RAM HR, 514.5 nm laser excitation).…”

“…In the contribution, we utilized m-Nb 2 CT x as the precursor, which was obtained by etching Nb 2 AlC MAX powder with aqueous HCl-LiF solution, [29] S2, Supporting Information), and are constructed by many nano-dimensional subunits, which is visually corroborated by transmission electron microscopy (TEM) and highresolution TEM (HRTEM) images (Figure 1g,h; Figure S3a-j, Supporting Information). The building blocks of ≈50-200 nm in size for CdNb 2 O 6 manifest their unique single-crystal property (Figure 1g,h), as confirmed by fast Fourier transform (FTT) analysis (the insets in Figure 1h).…”