Effect of Carbon Source on Synthesis of Carbon Coated Lithium Titanate

Carbon coated lithium titanate (Li4Ti5O12/C) was obtained by a facile solid state approach in inert Ar atmosphere. The composition, morphology, residual carbon content and Ti valence of the samples were systematically investigated. The carbon content of Li4Ti5O12/C should be optimized, since excess carbon in the composite leads to the reduction of Ti (IV) to form Ti (III), which results in large irreversible capacity of Li4Ti5O12/C. With an optimal carbon content of 0.68wt%, the Li4Ti5O12/C sample shows high rate capabilities and good cycling ability, delivering discharge capacities of 160.8 mAh/g at 5C. The superior high rate properties are ascribed to the specific nanostructures, which enables fast electronic and ionic transport by introducing carbon coating and decreasing the particle size of lithium titanate.

A Segmented Cell Measuring Technique for Current Distribution Measurements in Batteries, Exemplified by the Operando Investigation of a Zn-Air Battery

A transimpedance amplifier circuit as well as an instrumental amplifier circuit were used to measure current densities of a zinc-air battery with an integrated segmented current collector foil. Error calculation showed that the transimpedance amplifier is superior to the used instrumental amplifier, but both methods provide valuable and consistent results. They both showed comparable results with operando insight into the current distribution of the battery. The knowledge about those distributions is essential to avoid fast degradation of battery materials and irreversible capacity loss due to heterogeneous dissolution of the anode during discharge. In this work we showed that oxygen starvation as well as gas flow rate leads to large current gradients. It was also demonstrated that heterogeneous current distributions on cathode side induces also a heterogenous dissolution behavior on the anode, resulting in irreversible capacity loss.

Elevated Electrochemical Performance of LiNi0.1Mg0.1Co0.8O2 and LiFePO4 Cathodes with Tris(2,2,2-trifluoroethyl) Phosphite as an Efficient Electrolyte Additive

The significant role of Tris(2,2,2-trifluoroethyl) phosphite (TTFP) as an efficient additive during cycling of the layered nanostructured LiNi0.1Mg0.1Co0.8O2 and olivine LiFePO4 cathode materials in EC/DMC and 1M LiPF6 electrolyte for Li-ion battery are extensively investigated in this work. The electrochemical characterization techniques such as cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy show that TTFP improves cycling stability and reduces the irreversible capacity of LiNi0.1Mg0.1Co0.8O2 and LiFePO4 electrodes. Also, the presence of TTFP in electrolyte solution reduces the impedance in LiNi0.1Mg0.1Co0.8O2 and LiFePO4 cathode materials at room temperature. A family of Nyquist plots was obtained from LiNi0.1Mg0.1Co0.8O2 and LiFePO4 electrodes for various potentials during the course of charging. The addition of TTFP in the electrolyte reduces the surface impedance of lithiated LiNi0.1Mg0.1Co0.8O2 and LiFePO4 which can be attributed to the reaction of the additive on the electrode’s surface. Also, the presence of the additive TTFP in LiNi0.1Mg0.1Co0.8O2 and LiFePO4 cell enhances the lithium diffusion rate and improves the electronic conductivity of the cathode material.

Recent Progress in Presodiation Technique for High-Performance Na-Ion Batteries

Na-ion batteries (NIBs) have been attracting growing interests in recent years with the increasing demand of energy storage owing to their dependence on more abundant Na than Li. The exploration of the industrialization of NIBs is also on the march, where some challenges are still limiting its step. For instance, the relatively low initial Coulombic efficiency (ICE) of anode can cause undesired energy density loss in the full cell. In addition to the strategies from the sight of materials design that to improve the capacity and ICE of electrodes, presodiation technique is another important method to efficiently offset the irreversible capacity and enhance the energy density. Meanwhile, the slow release of the extra Na during the cycling is able to improve the cycling stability. In this review, we would like to provide a general insight of presodiation technique for high-performance NIBs. The recent research progress including the principles and strategies of presodiation will be introduced, and some remaining challenges as well as our perspectives will be discussed. This review aims to exhibit the basic knowledge of presodiation to inspire the researchers for future studies.

The triad “electrode – solid electrolyte interphase – electrolyte” as a ground for the use of conversion type reactions in lithium-ion batteries

The solution to the problem of negative impact on the ecology of fossil fuel consumption is the use of electrochemical energy sources. The special attractiveness has shown of lithium power sources is highlighted and the need to develop new cheap electrode materials and electrolytes with unique properties. The peculiarities of the behavior of lithium and the formation of a layer of reaction products on its surface upon contact with a liquid organic electrolyte have considered. The analysis of the main problems and ways of their solution at use of conversion electrodes of the II type for lithium-ion batteries has carried out. Emphasis is placed on the need to use in the development of new electrode materials of such parameters as capacity loading and accumulated irreversible capacity of the electrodes. The triad “electrode – solid electrolyte interphase – electrolyte” is considered as a basis of a systematic approach to the creation of new generations of lithium power sources. The optimal scenarios have proposed for the formation of an effective solid electrolyte interphase on the surface of the electrodes. The advantages of electrolytes based on fluoroethylene carbonate with synergistic acting additives of vinylene carbonate and ethylene sulfite are described. A new strategy for the use of “secondary” silicon nanomaterials to prevent direct contact of its surface with the electrolyte has considered. It has shown that the solid electrolyte interphase is a dynamic system that self-organizes from the unstable state into a stable one. The electrochemical behavior of electrodes with silicon nanocomposites with high capacity loading and low accumulated irreversible capacity has described.

Engineering Mesoporous Structure in Amorphous Carbon Boosts Potassium Storage with High Initial Coulombic Efficiency

Amorphous carbon shows great potential as an anode material for high-performance potassium-ion batteries; however, its abundant defects or micropores generally capture K ions, thus resulting in high irreversible capacity with low initial Coulombic efficiency (ICE) and limited practical application. Herein, pore engineering via a facile self-etching strategy is applied to achieve mesoporous carbon (meso-C) nanowires with interconnected framework. Abundant and evenly distributed mesopores could provide short K+ pathways for its rapid diffusion. Compared to microporous carbon with highly disordered structure, the meso-C with Zn-catalyzed short-range ordered structure enables more K+ to reversibly intercalate into the graphitic layers. Consequently, the meso-C shows an increased capacity by ~ 100 mAh g−1 at 0.1 A g−1, and the capacity retention is 70.7% after 1000 cycles at 1 A g−1. Multiple in/ex situ characterizations reveal the reversible structural changes during the charging/discharging process. Particularly, benefiting from the mesoporous structure with reduced specific surface area by 31.5 times and less defects, the meso-C generates less irreversible capacity with high ICE up to 76.7%, one of the best reported values so far. This work provides a new perspective that mesopores engineering can effectively accelerate K+ diffusion and enhance K+ adsorption/intercalation storage.