Novel Thermotolerant and Flexible Polyimide Aerogel Separator Achieving Advanced Lithium‐Ion Batteries

Abstract

Separators are vital parts of all lithium-ion batteries (LIBs), and they play a critical role in their thermal safety and electrochemical performance. Considering the low thermal stability and inferior electrolyte wettability of commercial polyolefin membranes, in this study, a novel thermotolerant polyimide aerogel (PIA) separator is designed. This is the first report on the use of chemically cross-linked PIA separators for LIBs. The outstanding porosity (78.35%) and electrolyte absorption (321.66%) of PIA separators contribute to the low internal resistance and outstanding electrochemical performance of LIBs, which can retain a high specific capacity of 118 mAh g −1 after 1000 cycles at a current density of 1 C. In addition, The LiFePO 4 |Li metal batteries with PIA separators are extremely stable at 90 °C (>300 cycles), and maintain stability even at 120 °C. More importantly, for pouch batteries, PIA separators result in higher thermal runaway temperatures compared with Celgard separators. In this paper, the pyrolysis mechanism and thermodynamic process of PIA separators are clarified by DFT calculations and in situ synchrotron vacuum UV photoionization mass spectrometry experiments.

Polyimide Aerogels with Excellent Thermal Insulation, Hydrophobicity, Machinability, and Strength Evolution at Extreme Conditions

“…14 Despite all of the advantages, their inherent fragility also affects any application. 15,16 Therefore, polyimide aerogels (PIA) are of great interest due to their ability to withstand high temperatures, 17,18 their exceptional thermal stability, 19 and their favorable mechanical properties, making PIA the material of choice in the thermal insulation field in the aerospace industry. 20,21 At present, the matrix of PIA has the problems of large drying shrinkage and insufficient thermal insulation performance.…”

“…Silica aerogels are the most welcome and the darling among these aerogels which have excellent properties such as high specific area, high porosity, and extremely low thermal conductivity . Despite all of the advantages, their inherent fragility also affects any application. , Therefore, polyimide aerogels (PIA) are of great interest due to their ability to withstand high temperatures, , their exceptional thermal stability, and their favorable mechanical properties, making PIA the material of choice in the thermal insulation field in the aerospace industry. , …”

Quasi-Solid-State Polymer Electrolyte Based on Electrospun Polyacrylonitrile/Polysilsesquioxane Composite Nanofiber Membrane for High-Performance Lithium Batteries

“…The SPEs can also act as the separator between the cathode and anode in LBs [ 19 ]. Commercialized polyolefin membranes have many shortcomings, such as poor thermal and dimensional stability, poor wettability and low porosity (<50%), which will lead to a high level of internal resistance, low ionic conductivity, Li dendrite growth and even short circuits occurring [ 20 , 21 , 22 ]. Great effort has been devoted to improving the performance of the polyolefin membrane [ 23 , 24 , 25 ], such as the surface modification of it [ 26 , 27 , 28 ] or developing various diaphragms from other sources such as PAN, PVDF and polyurethane [ 29 , 30 , 31 ].…”

Design of a hydrolysis‐supported coating layer on the surface of Ni‐rich cathodes in secondary batteries

“…Furthermore, when a high-Ni LNCM material is exposed to a humid environment, Ni 3+ on the surface changes to Ni 2+ , and the formation of residual Li compounds is accelerated, of which those present on the cover of the LNCM material cause the following problems. [12][13][14][15][16][17] (1) When the residual Li compound is dissolved in the solvent, that is, N-methyl-2-pyrrolidone (NMP), during the electrode casting process, the solvent is basified, following which it is mixed with the binder, polyvinylidene fluoride (PVdF), to gelate the slurry, making it impossible to fabricate the electrode. (2) The carbonate component of the residual Li is easily attacked by HF generated by a negligible number of water molecules present in the electrolyte and decompose to generate gas, which causes the battery to explode.…”

“…For this reason, Li that is not located in the Li layer reacts with CO 2 present in the air during the heat treatment process to form Li 2 CO 3 or reacts with water to form LiOH, which are referred to as residual Li compounds. Furthermore, when a high‐Ni LNCM material is exposed to a humid environment, Ni 3+ on the surface changes to Ni 2+ , and the formation of residual Li compounds is accelerated, of which those present on the cover of the LNCM material cause the following problems 12‐17 . (1) When the residual Li compound is dissolved in the solvent, that is, N‐methyl‐2‐pyrrolidone (NMP), during the electrode casting process, the solvent is basified, following which it is mixed with the binder, polyvinylidene fluoride (PVdF), to gelate the slurry, making it impossible to fabricate the electrode.…”