Understanding Rapid Intercalation Materials One Parameter at a Time

Abstract

Demand for fast, energy‐dense storage drives the research into nanoscale intercalation materials. Nanomaterials accelerate kinetics and can modify reaction path thermodynamics, intercalant solubility, and reversibility. The discovery of intercalation pseudocapacitance has opened questions about their fundamental operating principles. For example, are their capacitor‐like current responses caused by storing energy in special near‐surface regions or rather is this response due to normal intercalation limited by a slower faradaic surface‐reaction? This review highlights emerging methods combining tailored nanomaterials with the process of elimination to disambiguate cause‐and‐effect at the nanoscale. This method is applied to multiple intercalation pseudocapacitive materials showing that the timescales exhibiting surface‐limited kinetics depended on the total intercalation length scale. These trends are inconsistent with the near‐surface perspective. A revised current‐model without assuming special near‐surface storage fits experimental data better across wide timescales. This model, combined with tailored nanomaterials and the process of elimination, can isolate material‐specific effects such as how amorphization/defect‐tailoring modifies both insertion and diffusion kinetics. Avenues for both faster intercalation pseudocapacitance and increased energy density are discussed. A relaxation time argument is suggested to explain the continuum between battery‐like and pseudocapacitive behaviors. Future directions include synthetic methods emphasizing tailored defects and analytical methods that minimize assumptions.

Stepwise Monomicelle Assembly for Highly Ordered Mesoporous TiO2 Membranes with Precisely Tailored Mesophase and Porosity

“…Interestingly, from the relationship between current ( i ) and scan rate ( v ), the b -values for cathodic and anodic peaks are calculated to be 0.98 and 0.96 even below 100 mV s –1 and the b -values also remain relatively high at greater scan rates, demonstrating the ultrafast kinetics from pseudocapacitance (Figure d). The derivative of the log( i )–log( v ) plots show the rate-dependent b -value along with increasing sweep rates (Figure e), which is well-fitted through a series model proposed by Stefik and co-workers. − The surface-limited threshold (SLT) of b -value > 0.9 and the diffusion-limited threshold (DLT) of b -value < 0.6 are applied to evaluate the reaction kinetics. The mesoporous TiO 2 membranes have a SLT of 100 mV s –1 , corresponding to a (dis)charging time of 20 s, demonstrating the ultrafast kinetics from pseudocapacitance.…”

“…The derivative of the log( i )–log( v ) plots show the rate-dependent b -value along with increasing sweep rates ( Figure 4 e), which is well-fitted through a series model proposed by Stefik and co-workers. 44 − 46 The surface-limited threshold (SLT) of b -value > 0.9 and the diffusion-limited threshold (DLT) of b -value < 0.6 are applied to evaluate the reaction kinetics. The mesoporous TiO 2 membranes have a SLT of 100 mV s –1 , corresponding to a (dis)charging time of 20 s, demonstrating the ultrafast kinetics from pseudocapacitance.…”

Enabling intercalation‐type TiNb24O62 anode for sodium‐ and potassium‐ion batteries via a synergetic strategy of oxygen vacancy and carbon incorporation

“…In consistent with the CV curves, there are no distinct voltage plateaus in the GCD profiles of TNO (Figure 3C). The sloping‐shaped profiles indicate that an intercalation of Na + into the tunnels of TNO occurs via Faradaic charge transfer with no phase transformation 54–56 . TNO delivers a reversible discharge capacity of 71 mA h g −1 at the current density of 20 mA g −1 , and the creation of OVs and rGO wrapping in TNO x /rGO‐32 significantly increases the capacity to 130 mA h g −1 (Figure 3D).…”

“…The sloping-shaped profiles indicate that an intercalation of Na + into the tunnels of TNO occurs via Faradaic charge transfer with no phase transformation. [54][55][56] TNO delivers a reversible discharge capacity of 71 mA h g −1 at the current density of 20 mA g −1 , and the creation of OVs and rGO wrapping in TNO x /rGO-32 significantly increases the capacity to 130 mA h g −1 (Figure 3D). Moreover, the storage of Na + in TNO x /rGO-32 is more reversible compared to TNO, which is evident from initial coulombic efficiency (ICE).…”

New approach for SANS measurement of micelle chain mixing during size and morphology transitions

“…Block polymer micelles have applications that span from drug/ gene delivery, [1][2][3] to nanoreactors, 4,5 emulsions, 6 and templates for nanomaterials. [7][8][9][10][11][12][13][14][15] The characterization of how micelle size and morphology evolves over time as a result of chain mixing are important, but has remained elusive. Despite the capabilities of existing SANS models, there is not yet such an approach compatible with the low data statistics associated with rapid measurements during morphology/size transformations.…”