Efficient asymmetric diffusion channel in MnCo2O4 spinel for ammonium-ion batteries.

Transition metal oxides ion diffusion channels have been developed for ammonium-ion batteries (AIBs). However, the influence of microstructural features of diffusion channels on the storage and diffusion behavior of NH4+ is not fully unveiled. In this study, by using MnCo2O4 spinel as a model electrode, the asymmetric ion diffusion channels of MnCo2O4 have been regulated through bond length optimization strategy and investigate the effect of channel size on the diffusion process of NH4+. In addition, the reducing channel size significantly decreases NH4+ adsorption energy, thereby accelerating hydrogen bond formation/fracture kinetics and NH4+ reversible diffusion within 3D asymmetric channels. The optimized MnCo2O4 with oxygen vacancies/carbon nanotubes composite exhibits impressive specific capacity (219.2 mAh g-1 at 0.1 A g-1) and long-cycle stability. The full cell with 3,4,9,10-perylenetetracarboxylic diimide anode demonstrates a remarkable energy density of 52.3 Wh kg-1 and maintains 91.9% capacity after 500 cycles. This finding provides a unique approach for the development of cathode materials in AIBs.

Revealing the Effect of the [CoO]6 Microstructure in Pseudocapacitance by Controlled Delithium of LiCoO2.

Revealing the in-depth structure-property relationship and designing specific capacity electrodes are particularly important for supercapacitors. Despite many efforts made to tune the composition and electronic structure of cobalt oxide for pseudocapacitance, insight into the [CoO]6 octahedron from the microstructure is still insufficient. Herein, we present a tunable [CoO]6 octahedron microstructure in LiCoO2 by a chemical delithiation process. The c-strained strain of the [CoO]6 octahedron is induced to form higher valence Co ions, and the (003) crystalline layer spacing increases to allow more rapid participation of OH- in the redox reaction. Interestingly, the specific capacity of L0.75CO2 is nearly four times higher than that of LiCoO2 at 10 mA g-1. The enhanced activity originated from the asymmetric strain [CoO]6 octahedra, resulting in enhanced electronic conductivity and Co-O hybridization for accelerated redox kinetics. This finding provides new insights into the modification strategy for pseudocapacitive transition metal oxides.

Polymer Chainmail: Steric Hindrance and Charge Compensation of Anion-Doped PEDOT to Boost Stress Deformation of Compressible Supercapacitor.

Conducting polymers with high theoretical capacitance and deformability are among the optimal candidates for compressible supercapacitor electrode materials. However, achieving both mechanical and electrochemical stabilities in a single electrode remains a great challenge. To address this issue, the "Polymer Chainmail" is proposed with reversible deformation capability and enhances stability because of the steric hindrance and charge compensation effect of doped anions. As a proof of concept, four common anions are selected as dopants for Poly(3,4-ethylenedioxythiophene) (PEDOT), and their effects on the adsorption and diffusion of H+ on PEDOT are verified using density functional theory calculations. Owing to the film formation effect, the PF 6 - ${{\rm{PF}}_6^- }$ doped PEDOT/nitrogen-doped carbon foam exhibits good mechanical properties. Furthermore, the composite demonstrates excellent rate performance and stability due to suitable anion doping. This finding provides new insights into the preparation of electrochemically stable conductive polymer-based compressible electrode materials.

Flexible electrochemical energy storage devices and related applications: recent progress and challenges.

Given the escalating demand for wearable electronics, there is an urgent need to explore cost-effective and environmentally friendly flexible energy storage devices with exceptional electrochemical properties. However, the existing types of flexible energy storage devices encounter challenges in effectively integrating mechanical and electrochemical performances. This review is intended to provide strategies for the design of components in flexible energy storage devices (electrode materials, gel electrolytes, and separators) with the aim of developing energy storage systems with excellent performance and deformability. Firstly, a concise overview is provided on the structural characteristics and properties of carbon-based materials and conductive polymer materials utilized in flexible energy storage devices. Secondly, the fabrication process and strategies for optimizing their structures are summarized. Subsequently, a comprehensive review is presented regarding the applications of carbon-based materials and conductive polymer materials in various fields of flexible energy storage, such as supercapacitors, lithium-ion batteries, and zinc-ion batteries. Finally, the challenges and future directions for next-generation flexible energy storage systems are proposed.