Qijiu Deng

Electrochemical characterization of Co3O4/MCNTs composite anode materials for sodium-ion batteries

A composite of transition metal oxide Co3O4 and multiwalled carbon nanotubes (MCNTs) was applied as an anode material for sodium-ion batteries via a simply modified solid-state reaction and sonication method. The as-prepared Co3O4/MCNTs composite shows improved electrochemical performance than bare Co3O4 owing to the Co3O4/MCNTs nanostructure that benefits Na ion and electronic transport together with buffering the large volume change of Co3O4 during charging and discharging process. Additionally, the Na-storage behavior and the original capacity loss of Co3O4 based on the conversion reaction have been investigated through cyclic voltammogram, X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. It is firstly demonstrated that in discharge state, Co3O4 particles initially react with Na to produce CoO and then is further reduced to nanosized Co in an amorphous sodium oxides matrix. In the charge process, Co nanoparticles were partially oxidized to Co3O4, the other part of the CoO remain leading capacity loss. These results offer new insights into the electrochemical process of transition metal-based anode materials for Na-ion batteries.

Porous Li2C8H4O4 coated with N-doped carbon by using CVD as an anode material for Li-ion batteries

Lithium terephthalate (Li2C8H4O4) and its carboxylate-based derivatives have been proposed as advanced organic anodes for low cost lithium/sodium ion batteries. One of the key barriers for practical application is poor rate capability due to the intrinsic low electronic conductivity of most organic materials at room temperature. To overcome this issue, porous microspheres consisting of Li2C8H4O4 nanoparticles were synthesized by a common spray drying method for the first time. Furthermore, a straight-forward surface coating technique was developed using urea powder as nitrogen and carbon sources simultaneously. Consequently, a N-doped carbon layer was uniformly coated onto nanostructured Li2C8H4O4 electroactive material at 400 °C by chemical vapor deposition. The composite electrode displays excellent electrochemical performance under high current rate even at room temperature.

Dicarboxylate CaC8H4O4 as a high-performance anode for Li-ion batteries

Currently, many organic materials are being considered as electrode materials and display good electrochemical behavior. However, the most critical issues related to the wide use of organic electrodes are their low thermal stability and poor cycling performance due to their high solubility in electrolytes. Focusing on one of the most conventional carboxylate organic materials, namely lithium terephthalate Li2C8H4O4, we tackle these typical disadvantages via modifying its molecular structure by cation substitution. CaC8H4O4 and Al2(C8H4O4)3 are prepared via a facile cation exchange reaction. Of these, CaC8H4O4 presents the best cycling performance with thermal stability up to 570 °C and capacity of 399 mA·h·g−1, without any capacity decay in the voltage window of 0.005–3.0 V. The molecular, crystal structure, and morphology of CaC8H4O4 are retained during cycling. This cation-substitution strategy brings new perspectives in the synthesis of new materials as well as broadening the applications of organic materials in Li/Na-ion batteries.

Disodium terephthalate/multiwall-carbon nanotube nanocomposite as advanced anode material for Li-ion batteries

Organic small molecule materials have attracted extensive attention due to their environmentally friendly, sustainability, and low cost which can be obtained from biomass and recyclable resources for Li/Na-ion batteries. However, the intrinsic poor electronic conductivities and the dissolution in organic liquid electrolyte lead to poor electrochemical performance, thus preventing them from practical application. To tackle these issues, herein, we take disodium terephthalate (Na2TP) as an example and report an organic/multiwall-carbon nanotube nanocomposite via a simple spray drying methodology as an anode material for Li-ion battery. It delivers improved electrochemical performance compared to the pristine Na2TP microspheres produced by the same spray drying method and the bulk microsized Na2TP prepared by a conventional water-crystallization method. This is mainly due to the as-prepared nanocomposite can shorten the Li-ion diffusion distance, form highly conductive network and slow the dissolution rate. Our simple methodology could be of interest designing newly organic composites.