Materials with nanosized dimensions exhibit different and interesting properties compared with their bulk counterpart, which is broadly applicable in several fields, including Li-ion batteries. These properties are intimately related to the morphological, compositional, and topographic features of the nanostructures, which are strongly dependent on the methods used to synthesize nanoparticles. Herein we present the synthesis of LiMn2O4 nanoparticles with controlled morphology by a thermal decomposition method of organometallic precursors followed by thermal treatment in air. The crystal structure, chemical composition, and morphology of the samples were analyzed by X-ray diffraction, transmission electron microscopy, electron diffraction, and electron energy-loss spectroscopy. By adjusting the reflux temperature and atmosphere we obtained nanoparticles and hollow nanostructures, while core-shell LiMn2O4/Li2O nanoparticles were obtained by adding a thermal decomposition stage.

Lithium oxosilicate has the highest proportion of lithium among lithium silicates, which is desirable for applications. Although Li8SiO6 is a stable phase, its obtention as a polycrystalline pure phase is not reported yet, probably because of the high sensitivity of the system Li2O–SiO2 to the synthesis conditions. In this work, we adapted a citrate-based route used for the synthesis of Li4SiO4 as a novel approach to the obtention of Li8SiO6. We found that the lowest amount of impurities is achieved by using a Li:C6H8O7 molar ratio of 2.8:1, a pH value of 8.5, and a lithium excess of 20%. In a complementary way, we used the solid-state reaction method as a function of the excess of lithium and optimized the conditions that lead to a minimum amount of impurities. We found that the purest Li8SiO6 phase is obtained with low or no lithium excess. Samples obtained by both methods exhibited a higher purity compared to the reports available in literature. The crystal structure for this phase is confirmed by selected area electron diffraction.

Spinel LiMn2O4is a promising cathode material for lithium-ion batteries. However, bulk LiMn2O4commonly suffers from capacity fading due to the dissolution of Mn into the electrolyte during cycling. Moreover, bulk LiMn2O4exhibits a low Li+diffusion coefficient that limits the volume available to Li+storage. Herein, we report the synthesis of small hollow porous LiMn2O4nanostructures with a mean size of 51 nm exhibiting exposed (111) planes, assembled by nanoparticles of about 6 nm in size. The morphological features of these nanostructures ensure a large contact area between the material and the electrolyte, shorten the pathways for Li+diffusion and provide effective accommodation of the volume change during cycling. Therefore, these hollow nanostructures exhibit improved discharge capacity retention (nearly 82% after 200 cycles) and a greater Li+diffusion coefficient (3.46 × 10-7cm s-1) compared with that of bulk LiMn2O4.

Thermal neutron attenuation capacity of Li4SiO4 was evaluated to assess its potential capabilities as a beam shaping material for boron neutron capture therapy (BNCT) facilities. Samples of Li4SiO4 were prepared by two different synthesis methods, using different raw materials and were characterized using x-ray, electron diffraction and transmission electron microscopy. Neutron measurements were performed at the BNCT and the neutron radiography facilities of Centro Atómico Bariloche. Considering its natural isotopic abundance, Li4SiO4 proved to be remarkably effective in comparison with other neutron-absorbing materials. Given the availability of natural Lithium in local salt mines and the scalable feasibility, Li4SiO4 qualifies as a potential material for BNCT beam shaping applications.