Properties of LiMnBO3 glasses and nanostructured glass-ceramics

Abstract

Polycrystalline LiMnBO3 is a promising cathode material for Li-ion batteries. In this work, we investigated the thermal, structural and electrical properties of glassy and nanocrystallized materials having the same chemical composition. The original glass was obtained via a standard meltquenching method. SEM and 7 Li solid-state NMR indicate that it contains a mixture of two distinct glassy phases. The results suggest that the electrical conductivity of the glass is dominated by the ionic one. The dc conductivity of initial glass was estimated to be in the order of 10 −18 S.cm −1 at room temperature. The thermal nanocrystallization of the glass produces a nanostructured glass-ceramics containing MnBO3 and LiMnBO3 phases. The electric conductivity of this glass-ceramics is increased by 6 orders of magnitude, compared to the starting material at room temperature. Compared to other manganese and borate containing glasses reported in the literature, the conductivity of the nanostructured glass ceramics is higher than that of the previously reported glassy materials. Such improved conductivity stems from the facilitated electronic transport along the grain boundaries.

Synthesis, thermal, structural and electrical properties of vanadium-doped lithium-manganese-borate glass and nanocomposites

“…The presence of two exothermic peaks indicates multiphase character of the material after annealing. The glass transition temperature is quite similar to the value obtained for LiMnBO 3 glass (T g = 411 • C), whereas the main crystallisation appeared at the temperature ∼60 • C higher [13]. This is in agreement with our previous studies on LiFe 1−5x/2 V x PO 4 nanomaterials, where T c increased with an increasing content of vanadium dopant [4].…”

“…This measurement is also presented separately in Fig. 9 and compared with values for undoped LiMnBO 3 [13]. One can see that the addition of vanadium caused boost in the conductivity value by 3 orders of magnitude.…”

“…All of the values calculated from the measurements are presented in Table 3. The highest conductivity value was obtained for the nanocrystallisation at 700 • C and reached 2.6 × 10 −9 Scm −1 (at RT) what gives increase in the [13] conductivity by 2×10 6 . This measurement is also presented separately in Fig.…”

“…Moreover, B 2 O 3 is a very well-known glass former. Therefore, it was natural to synthesise a glassy analogue of LiMnBO 3 and try to improve its modest electrical conductivity by thermal nanocrystallisation [13]. Despite many efforts and comprehensive studies, the final values of electrical conductivity have been unsatisfactory.…”

Effect of PVP Coating on LiMnBO3 Cathodes for Li-Ion Batteries

“…It was discovered to have a reversible capacity in 2001, but only 2% of its theoretical capacity could be delivered, which is attributed to large polarization [14]. To improve the performance of LiMnBO 3 , several approaches have been proposed, including carbon coating [15][16][17][18][19], particle size reduction [20][21][22][23], and cation doping or substitution [9,[24][25][26]. Although the performance of LiMnBO 3 can be enhanced by doping and fine particles, it needs to be coated with carbon at the same time [15][16][17][18][19].…”