High‐rate sodium‐ion storage of vanadium nitride via surface‐redox pseudocapacitance

Abstract

Vanadium nitride (VN) electrode displays high‐rate, pseudocapacitive responses in aqueous electrolytes, however, it remains largely unclear in nonaqueous, Na+‐based electrolytes. The traditional view supposes a conversion‐type mechanism for Na+ storage in VN anodes but does not explain the phenomena of their size‐dependent specific capacities and underlying causes of pseudocapacitive charge storage behaviors. Herein, we insightfully reveal the VN anode exhibits a surface‐redox pseudocapacitive mechanism in nonaqueous, Na+‐based electrolytes, as demonstrated by kinetics analysis, experimental observations, and first‐principles calculations. Through ex situ X‐ray photoelectron spectroscopy and semiquantitative analyses, the Na+ storage is characterized by redox reactions occurring with the V5+/V4+ to V3+ at the surface of VN particles, which is different from the well‐known conversion reaction mechanism. The pseudocapacitive performance is enhanced through nanoarchitecture design via oxidized vanadium states at the surface. The optimized VN‐10 nm anode delivers a sodium‐ion storage capability of 106 mAh g−1 at the high specific current of 20 A g−1, and excellent cycling performance of 5000 cycles with negligible capacity losses. This work demonstrates the emerging opportunities of utilizing pseudocapacitive charge storage for realizing high‐rate sodium‐ion storage applications.

SnS2 nanoparticles embedded in sulfurized polyacrylonitrile composite fibers for high‐performance potassium‐ion batteries

“…To further determine the contribution of diffusion‐controlled behavior to the overall process, the following equation was employed: $$$i(V)={k}_{1}(V)\hspace{0.17em}\cdot \hspace{0.17em}v+{k}_{2}(V)\hspace{0.17em}\cdot \hspace{0.17em}{v}^{1/2},$$$where k 1 and k 2 are the constants, and k 1 ( V ) · $$v$$ and k 2 ( V ) · $$v$$ 1/2 represent the contribution of capacitive and diffusion control processes, respectively. [ 70 ] Figure shows that approximately 25% of the overall capacity is attributed to the capacitive process at a scan rate of 0.6 mV s −1 . The contribution of pseudocapacitance to the overall capacities of SnS 2 @SPAN is plotted in Figure .…”

“…where k 1 and k 2 are the constants, and k 1 (V) • v and k 2 (V) • v 1/2 represent the contribution of capacitive and diffusion control processes, respectively. [70] Figure S4c shows that approximately 25% of the overall capacity is attributed to the capacitive process at a scan rate of 0.6 mV s −1 . The contribution of pseudocapacitance to the overall capacities of SnS 2 @SPAN is plotted in Figure S4d.…”

PEDOT Nanowires Connecting Exfoliated HNb3O8 Nanosheets as High-Rate Anode for Lithium-Ion Capacitor

“…This result reveals that the storage of Li + ions in E-HNb 3 O 8 -PEDOT-0.2 is dominated by a diffusion-controlled electrochemical process. The quantitative analysis of capacity contribution is further conducted by using the formula i = k 1 v + k 2 v 1/2 , where k 1 v and k 2 v 1/2 are the current contributions from capacitive and diffusion-controlled processes, respectively. − As shown in Figure c, the current contribution from the capacitive-controlled process accounts for 22% of the total current at 0.1 mV s –1 . This capacitive-controlled contribution gradually increased and reached 48% at 1.0 mV s –1 (Figure d).…”

Adsorption Recycling and High-Value Reutilization of Heavy-Metal Ions from Wastewater: As a High-Performance Anode Lithium Battery

“…The MC-700 electrode’s initial CE is 62.05% and rises significantly to 98.57% in the 10th cycle. During the early cycles, the capacity of the three electrodes was unstable, possibly due to the intrinsic reactivity of the active materials including volume changes, which caused structural deterioration and unstable SEI development . The electrodes progressively recover and even exceed their original capacity in successive cycles due to the following reasons: (1) Some functional groups and defects remain on the surface of the carbon aerogel, which can provide additional lithium storage capacity through a pseudocapacitive mechanism during cycling; (2) the electrode activation process forms the electrochemically active gel-like film, which has been widely reported for most transition-metal oxide-based anode materials.…”