Aluminum Diethylphosphinate-Incorporated Flame-Retardant Polyacrylonitrile Separators for Safety of Lithium-Ion Batteries

Electrospun Poly(vinyl Alcohol)/Chitin Nanofiber Membrane as a Sustainable Lithium-Ion Battery Separator

Commercial battery separators are made of polyolefin polymers due to their desired mechanical strength and chemical stability. However, these materials are not biodegradable and are challenging to recycle. Considering the environmental issues from polyolefins, biodegradable polymers can be developed as separators to reduce the potential waste from polyolefin separators. In this work, we investigated the potential of poly(vinyl alcohol)/chitin nanofiber (PVA/CHNF) nanofiber as a sustainable lithium-ion battery separator, which was successfully fabricated via the electrospinning and cross-linking method. The PVA/CHNF separator is biodegradable and has an ionic conductivity (1.41 mS cm-1), desirable porosity (86%), good thermal stability (1.4% shrinkage upon heating at 90 °C for 1 h), as well as high electrolyte uptake (388%). The PVA/CHNF separator is also evaluated in the assembled Li//LiFePO4 cells, showing an improved performance compared to the cell with the commercial separator. It shows a discharge capacity of 142 mAh g-1, which is stable throughout 120 charge-discharge cycles. Hence, according to these resulting properties, the PVA/CHNF separator shows promise as a sustainable and environmentally friendly lithium-ion battery separator, offering a high-value use of waste chitin materials.

Composition regulation of polyacrylonitrile-based polymer electrolytes enabling dual-interfacially stable solid-state lithium batteries

The polyacrylonitrile (PAN) is an attractive matrix of polymer electrolytes owing to its wide electrochemical window and strong coordination with Li salts. However, the PAN-based electrolytes undergo severe interfacial problems from both cathode and anode sides, including uneven ionic transfer induced by high rigidity of dry PAN-based polymer, as well as inferior stability against Li-metal anode. Herein, the composition regulation of PAN-based electrolytes is proposed by introducing succinonitrile (SN) plastic crystal and LiNO3 salt for the construction of interfacially stable solid-state lithium batteries. The plastic nature of SN enables the rapid ionic transfer in electrolytes, along with the establishment of conformally interfacial contacts. Meanwhile, a stable solid-electrolyte-interface (SEI) layer consisting of Li3N and LiNO2 is in-situ formed at Li/electrolyte interface, contributing to the inhibition of uncontrol reactions between PAN and Li-metal. Consequently, the resultant Li symmetric cell delivers an extended critical current density of 1.7 mA cm-2 and an outstanding cycling lifespan of 700 h at 0.1 mA cm-2. Moreover, the corresponding solid-state LiNi0.6Co0.2Mn0.2O2/Li full cell shows an initial discharge capacity of 161 mAh/g followed by an outstanding capacity retention of 88.7 % after 100 cycles at 0.1C. This work paves the way for application of PAN-based electrolytes in the field of solid-state batteries by facile composition regulation.

Recent Development in Novel Lithium-Sulfur Nanofiber Separators: A Review of the Latest Fabrication and Performance Optimizations

Lithium-Sulfur batteries (LSBs) are one of the most promising next-generation batteries to replace Li-ion batteries that power everything from small portable devices to large electric vehicles. LSBs boast a nearly five times higher theoretical capacity than Li-ion batteries due to sulfur's high theoretical capacity, and LSBs use abundant sulfur instead of rare metals as their cathodes. In order to make LSBs commercially viable, an LSB's separator must permit fast Li-ion diffusion while suppressing the migration of soluble lithium polysulfides (LiPSs). Polyolefin separators (commonly used in Li-ion batteries) fail to block LiPSs, have low thermal stability, poor mechanical strength, and weak electrolyte affinity. Novel nanofiber (NF) separators address the aforementioned shortcomings of polyolefin separators with intrinsically superior properties. Moreover, NF separators can easily be produced in large volumes, fine-tuned via facile electrospinning techniques, and modified with various additives. This review discusses the design principles and performance of LSBs with exemplary NF separators. The benefits of using various polymers and the effects of different polymer modifications are analyzed. We also discuss the conversion of polymer NFs into carbon NFs (CNFs) and their effects on rate capability and thermal stability. Finally, common and promising modifiers for NF separators, including carbon, metal oxide, and metal-organic framework (MOF), are examined. We highlight the underlying properties of the composite NF separators that enhance the capacity, cyclability, and resilience of LSBs.