Dongping Lv

Coordination Chemistry in magnesium battery electrolytes: how ligands affect their performance

Magnesium battery is potentially a safe, cost-effective, and high energy density technology for large scale energy storage. However, the development of magnesium battery has been hindered by the limited performance and the lack of fundamental understandings of electrolytes. Here, we present a study in understanding coordination chemistry of Mg(BH4)2 in ethereal solvents. The O donor denticity, i.e. ligand strength of the ethereal solvents which act as ligands to form solvated Mg complexes, plays a significant role in enhancing coulombic efficiency of the corresponding solvated Mg complex electrolytes. A new electrolyte is developed based on Mg(BH4)2, diglyme and LiBH4. The preliminary electrochemical test results show that the new electrolyte demonstrates a close to 100% coulombic efficiency, no dendrite formation, and stable cycling performance for Mg plating/stripping and Mg insertion/de-insertion in a model cathode material Mo6S8 Chevrel phase.

Nanostructured 0.8Li2FeSiO4/0.4Li2SiO3/C composite cathode material with enhanced electrochemical performance for lithium-ion batteries

A strategy is proposed and developed to promote Li+ diffusion in polyanion cathode materials such as 0.8Li2FeSiO4/0.4Li2SiO3/C with the incorporation of Li2SiO3 as a lithium ionic conductive matrix. It is shown that the presence of Li2SiO3 separates the Li2FeSiO4 particles into small domains of a few nanometres and provides a fast Li+ diffusion channel, thus effectively enhancing Li+ diffusion in the 0.8Li2FeSiO4/0.4Li2SiO3/C composite. As a result, the composite material shows enhanced electrochemical performance and delivers a capacity as high as 240 mA h g−1 (corresponding to 1.44 electrons exchange per active Li2FeSiO4 formula unit) with good cyclic stability at 30 °C. The XRD and FTIR results indicate that the Li2SiO3 component exists in an amorphous phase. SEM and TEM analyses show an aggregate structure consisting of primary nanocrystallites (about tens of nanometres in diameter). The primary particles consist of a crystal Li2FeSiO4 phase and an amorphous Li2SiO3 and C, and a nanocrystalline Li2FeSiO4 surrounded by amorphous Li2SiO3 and C which are well known as a lithium ion conductor and electron conductor. The smaller nanoparticles of Li2FeSiO4 and the presence of lithium ionic and electronic conducting amorphous Li2SiO3 and carbon matrix both contributed to the enhanced electrochemical performance of the composite.

Hydrothermal Synthesis and Electrochemical Performance of Li1.59H0.41MnO3 as a Cathode Material for Lithium-Ion Battery

Li 1.59 H 0.41 MnO 3 , a Li 2 MnO 3 -type cathode material, was synthesized by hydrothermally treating an amorphous MnOOH in LiOH and (NH 4 ) 2 S 2 O 8 aqueous solution. Such a rocksalt material was confirmed as proton-substituted Li 2 MnO 3 , i.e., Li 1.59 H 0.41 MnO 3 instead of a composite of Li 2 MnO 3 with other polymorphs of manganese oxides with Mn(IV) such as Li 2 Mn 4 O 9 and Li 4 Mn 5 O 12 . The Li 1.59 H 0.41 MnO 3 shows a remarkable difference in structure and electrochemical performance from those proton-substituted Li 2 MnO 3 by acid treatment in previous studies. The Li 1.59 H 0.41 MnO 3 cathode behaved similarly to that of Li 2 MnO 3 material and delivered a high discharge capacity of 256 mAh g -1 at 20 mAh g -1 (4.8-2.0 V).

Sodium-Ion-Assisted Hydrothermal Synthesis of γ-MnO2 and Its Electrochemical Performance

National Natural Science Foundation of China [20433060, 20473068, 29925310]; National Basic Research Program (973 Program)