Zhanyu Li

Structure and electrochemical properties of Sm-doped Li4Ti5O12 as anode material for lithium-ion batteries

Sm-doped Li4Ti5O12 (LTO) in the form of Li4−x/3Ti5−2x/3SmxO12 (x = 0, 0.01, 0.03, 0.05 and 0.10) is synthesized successfully by a simple solid-state reaction in air. XRD analysis and Rietveld refinement demonstrate that traces of the doped Sm3+ ions have successfully entered the lattice structure of the bulk LTO and the Sm doping does not change the spinel structure of LTO. However, of interest is that the lattice parameter increases gradually with the increase of the Sm doping amount, which is potentially beneficial for intercalation and de-intercalation of lithium ions. XPS results further identify the existence of Ti3+ ions and the transition of a small quantity of Ti ions from Ti4+ to Ti3+, which will improve the conductivity of LTO. All materials are well crystallized with a uniform and narrow size distribution in the range of 0.5–1.2 μm. The results of electrochemical measurement reveal that the Sm doping can improve the rate capability and cycling stability of LTO. Among all samples, Li4−x/3Ti5−2x/3SmxO12 (x = 0.03) exhibits the best electrochemical properties. The specific capacities of the Li4−x/3Ti5−2x/3SmxO12 (x = 0.03) sample at charge and discharge rates of 5C and 10C are 131.1 mA h g−1 and 119.2 mA h g−1, respectively, compared with 64 mA h g−1 (5C) and 47 mA h g−1 (10C) for the pristine LTO in the potential range 1.0–2.5 V (vs. Li/Li+). This result can be attributed to Li4−x/3Ti5−2x/3SmxO12 (x = 0.03) with a diffusion coefficient of 1.3 × 10−12 cm2 s−1, which is higher than the 7.4 × 10−14 cm2 s−1 for the LTO electrode without Sm doping. In the meantime, the discharge capacity of Li4−x/3Ti5−2x/3SmxO12 (x = 0.03) can still reach 125.1 mA h g−1 even after 100 cycles and maintain 95.2% of its initial discharge capacity at 5C. Therefore, Sm doping has a great impact on discharge capacity, rate capability and cycling performance of LTO anode materials for lithium-ion batteries.

Rechargeable Aluminum-Ion Battery Based on MoS2 Microsphere Cathode

In recent years, a rechargeable aluminum-ion battery based on ionic liquid electrolyte is being extensively explored due to three-electron electrochemical reactions, rich resources, and safety. Herein, a rechargeable Al-ion battery composed of MoS2 microsphere cathode, aluminum anode, and ionic liquid electrolyte has been fabricated for the first time. It can be found that Al3+ intercalates into the MoS2 during the electrochemical reaction, whereas the storage mechanisms of the electrode material interface and internal are quite different. This result is confirmed by ex situ X-ray photoelectron spectroscopy and X-ray diffraction etching techniques. Meanwhile, this aluminum-ion battery also shows excellent electrochemical performance, such as a discharge specific capacity of 253.6 mA h g-1 at a current density of 20 mA g-1 and a discharge capacity of 66.7 mA h g-1 at a current density of 40 mA g-1 after 100 cycles. This will lay a solid foundation for the commercialization of aluminum-ion batteries.

A Novel Graphite-Graphite Dual Ion Battery Using an AlCl3-[EMIm]Cl Liquid Electrolyte

Herein, a novel graphite-graphite dual ion battery (GGDIB) based on a AlCl3 /1-ethyl-3-methylimidazole Cl ([EMIm]Cl) room temperature ionic liquid electrolyte, using conductive graphite paper as cathode and anode material is developed. The working principle of the GGDIB is investigated, that is, metallic aluminum is deposited/dissolved on the surface of the anode, and chloroaluminate ions are intercalated/deintercalated in the cathode material. The self-discharge phenomenon and pseudocapacitive behavior of the GGDIB are also analyzed. The GGDIB shows excellent rate performance and cycle performance due to the high ionic conductivity of ionic liquids. The initial discharge capacity is 76.5 mA h g-1 at a current density of 200 mA g-1 over a voltage window of 0.1-2.3 V, and the capacity remains at 62.3 mA h g-1 after 1000 cycles with a corresponding capacity retention of 98.42% at a current density of 500 mA g-1 . With the merits of environmental friendliness and low cost, the GGDIB has a great advantage in the future of energy storage application.