Class of Boehmite/Polyacrylonitrile Membranes with Different Thermal Shutdown Temperatures for High-Performance Lithium-Ion Batteries

Abstract

Nowadays, lithium-ion batteries are required to have a higher energy density and safety because of their wide applications. Current commercial separators have poor wettability and thermal stability, which significantly impact the performance and safety of batteries. In this study, a class of boehmite particles with different grain sizes was synthesized by adjusting hydrothermal temperatures and used to fabricate boehmite/polyacrylonitrile (BM/PAN) membranes. All of these BM/PAN membranes can not only maintain excellent thermal dimensional stability above 200 °C but also have good electrolyte wettability and high porosity. More interestingly, the BM/PAN membranes' thermal shutdown temperature can be adjusted by changing the grain size of boehmite particles. The lithium-ion batteries assembled with BM/PAN separators exhibit different thermal stability phenomena at 150 °C and have excellent rate performance and cycle stability at room temperature. After 120 cycles at 1C, the LiFePO 4 half-cell assembled by the best BM/PAN separator has almost unchanged discharge capacity, whereas the capacity retention of Celgard 2325 is only about 85%. Meanwhile, the NCM523 half-cell assembled with the best BM/PAN separator shows superb cycle stability after 500 cycles at 8C, with a capacity retention of 79% compared with 56% for Celgard 2325.

Different-grain-sized boehmite nanoparticles for stable all-solid-state lithium metal batteries

“…This further demonstrates that boehmite can reduce the crystallinity of the solid-state electrolytes, which, in turn, increases the movement of PEO chains at room temperature. 32 The TG curves in Fig. 3b demonstrate the thermal stability of BPEs.…”

“…† All adsorption/desorption isotherms of boehmite nanoparticles exhibit characteristic features of a typical IV isotherm, accompanied by obvious type H3 hysteresis loops. 32 The mesopores are formed by the gaps in the boehmite nanoparticle stack, and the pore size distribution of boehmite particles grows broader as the synthesis temperature rises, due to the stack of the bigger-grain-sized boehmite. 35 The multistage pore structure of boehmite particles is conducive to the transport of lithium ions.…”

“…[28][29][30] Boehmite, a variant of aluminum oxide, has lower hardness and specific gravity, weak water absorption, and excellent performance in lithium ion batteries. [31][32][33] In this work, we prepared different-grain-sized boehmite nanoparticles by modulating the hydrothermal temperature (200-280 °C) and manufactured them into boehmite/polyethylene oxide (BM/PEO) solid-state polymer electrolytes by a solution-casting method, as shown in Scheme 1.…”