Mesoporous Li_xMn₂O₄Thin Film Cathodes for Lithium-Ion Pseudocapacitors

Abstract

Charge storage devices with high energy density and enhanced rate capabilities are highly sought after in today's mobile world. Although several high-rate pseudocapacitive anode materials have been reported, cathode materials operating in a high potential range versus lithium metal are much less common. Here, we present a nanostructured version of the well-known cathode material, LiMn2O4. The reduction in lithium-ion diffusion lengths and improvement in rate capabilities is realized through a combination of nanocrystallinity and the formation of a 3-D porous framework. Materials were fabricated from nanoporous Mn3O4 films made by block copolymer templating of preformed nanocrystals. The nanoporous Mn3O4 was then converted via solid-state reaction with LiOH to nanoporous LixMn2O4 (1 < x < 2). The resulting films had a wall thickness of ∼15 nm, which is small enough to be impacted by inactive surface sites. As a consequence, capacity was reduced by about half compared to bulk LiMn2O4, but both charge and discharge kinetics as well as cycling stability were improved significantly. Kinetic analysis of the redox reactions was used to verify the pseudocapacitive mechanisms of charge storage and establish the feasibility of using nanoporous LixMn2O4 as a cathode in lithium-ion devices based on pseudocapacitive charge storage.

Artificial solid electrolyte interphase for aqueous lithium energy storage systems

“…Similar to R ct , the 10RGO sample has smaller D Li in the initial few cycles but shows much larger values than the Blank sample after 10 cycles. In the ALESS, the Jahn-Teller distortion of Li transition metal oxides and the carbon oxidation/consumption significantly affect the Li + diffusion in electrode/electrolyte interfaces ( 71 , 72 ). The results obtained here are also in agreement with the calculated D Li from the CV plots at different C rates.…”

Insert Zn Nanoparticles into the 3D Porous Carbon Ultrathin Films as a Superior Anode Material for Lithium Ion Battery

“…Quantitatively, the formula i ( V ) = k 1 v + k 2 v 1/2 can be used to calculate the mixed mechanisms concretely, where i is the current, V is some fixed potential, v is scan rate, and k 1 and k 2 are constants . As shown in Figure d, P‐Zn/C composite is with 74% capacitance contribution and 26% diffusion contribution at the scan rate of 0.2 mV s −1 .…”

Controllable Fabrication and Li Storage Kinetics of 1 D Spinel LiMn2O4 Positive Materials for Li‐ion Batteries: An Exploration of Critical Diameter

“…Because of a large number of Li + ions at the 8 a sites being replaced by Mn 2+ ions, a stable, thick electrochemically inactive surface consisting of Mn 2+ [Mn 3+ Mn 3+ ]O 4 phase can be easily formed . Different from the spinel Li + [Mn 3+ Mn 4+ ]O 4 phase, the fresh Mn 2+ [Mn 3+ Mn 3+ ]O 4 phase is unable to undergo a Mn 3+ →Mn 4+ transition, which is likely to trigger the capacity fading of the LiMn 2 O 4 nanorod electrodes . The illustration of the electrochemically inactive surface is shown in Figure b.…”