Haibo Rong

Triple-shelled Mn2O3 hollow nanocubes: force-induced synthesis and excellent performance as the anode in lithium-ion batteries

In this paper, we report a novel structure of Mn2O3, the triple-shelled Mn2O3 hollow nanocube, as the anode material for high-energy lithium-ion batteries, synthesized through a programmed annealing treatment with cubic MnCO3 as precursor. This hierarchical structure is developed through the interaction between the contraction force from the decomposition of MnCO3 and the adhesion force from the formation of Mn2O3. The structure has been confirmed by characterization with XRD, FESEM, TEM, and HRTEM. The charge–discharge tests demonstrate that the resulting Mn2O3 exhibits excellent cycling stability and rate capability when evaluated as an anode material for lithium-ion batteries. It delivers a reversible capacity of 606 mA h g−1 at a current rate of 500 mA g−1 with a capacity retention of 88% and a remaining capacity of 350 mA h g−1 at 2000 mA g−1.

A novel electrolyte with the ability to form a solid electrolyte interface on the anode and cathode of a LiMn2O4/graphite battery

To improve the cyclability of a LiMn2O4/graphite lithium ion battery at elevated temperature, a carbonate-based electrolyte using prop-1-ene-1,3-sultone (PES) as additive was developed. The cycling performance of the LiMn2O4/graphite cell, based on the developed electrolyte at 60 °C, was evaluated by a constant current charge/discharge test, with comparison of the electrolyte using vinylene carbonate (VC) as additive. It was found that the cell based on the developed electrolyte exhibits better cyclability and exhibits better dimensional stability at elevated temperatures. The capacity retention is 91% and the swell value in thickness is 3.4% for the cell with PES after 150 cycles at 60 °C, while the respective values were 68% and 36.4% for the cell without additive, and 82% and 9.1% for the cell with VC. The results obtained from scanning electron spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermal gravimetric analysis, and molecular energy level calculations show that PES favors the formation of a stable solid electrolyte interphase, not only on the anode but also on the cathode of the LiMn2O4/graphite battery, effectively preventing electrolyte decomposition.

Crystallographic facet- and size-controllable synthesis of spinel LiNi0.5Mn1.5O4 with excellent cyclic stability as cathode of high voltage lithium ion battery

We report a novel synthesis of spinel LiNi0.5Mn1.5O4, in which cubic and porous Mn2O3 nanoparticles, obtained from cubic MnCO3, are used as templates to induce the formation of crystallographic facet- and size-defined spinel. This is done to accomplish excellent cyclic stability of the spinel as a cathode of a high voltage lithium ion battery. The uniformly dispersed pores in the template, whose size can be controlled by limiting the annealing time of MnCO3, facilitate the incorporation of lithium and nickel ions and ensure the formation of spinel with a predominant (111) facet, while the spinel inherits the particle size of the template under controlled temperatures. The characterizations from SEM, TEM and XRD confirm the structure and morphology of the precursors and the resulting product. The charge–discharge test demonstrates the excellent cyclic stability of the resulting products, especially at elevated temperatures: capacity retention of 78.1% after 3000 cycles with 10 C rate at room temperature and that of 83.2% after 500 cycles with 5 C rate at 55 °C.

Porous LiMn2O4 cubes architectured with single-crystalline nanoparticles and exhibiting excellent cyclic stability and rate capability as the cathode of a lithium ion battery

Porous LiMn2O4 was fabricated with cubic MnCO3 as precursor and characterized in terms of structure and performance as the cathode of a lithium ion battery. The characterizations from SEM, TEM and XRD demonstrate that the fabricated product has a cubic morphology with an average edge of 250 nm, which it inherits from the precursor, and a porous structure architectured with single-crystalline spinel nanoparticles of 50 nm, which imitates the Mn2O3 that results from the thermal decomposition of the precursor. The charge–discharge tests show that the synthesized product exhibits excellent rate capability and cyclic stability: delivering a reversible discharge capacity of 108 mA h g−1 at a 30 C rate and yielding a capacity retention of over 81% at a rate of 10 C after 4000 cycles. The superior performance of the synthesized product is attributed to its special structure: porous secondary cube particles consisting of primary single-crystalline nanoparticles. The nanoparticle reduces the path of Li ion diffusion and increases the reaction sites for lithium insertion/extraction, the pores provide room to buffer the volume changes during charge–discharge and the single crystalline nanoparticle endows the spinel with the best stability.