A low cost shutdown sandwich-like composite membrane with superior thermo-stability for lithium-ion battery

Functionalized Separators Boosting Electrochemical Performances for Lithium Batteries

The growing demands for energy storage systems, electric vehicles, and portable electronics have significantly pushed forward the need for safe and reliable lithium batteries. It is essential to design functional separators with improved mechanical and electrochemical characteristics. This review covers the improved mechanical and electrochemical performances as well as the advancements made in the design of separators utilizing a variety of techniques. In terms of electrolyte wettability and adhesion of the coating materials, we provide an overview of the current status of research on coated separators, in situ modified separators, and grafting modified separators, and elaborate additional performance parameters of interest. The characteristics of inorganics coated separators, organic framework coated separators and inorganic-organic coated separators from different fabrication methods are compared. Future directions regarding new modified materials, manufacturing process, quantitative analysis of adhesion and so on are proposed toward next-generation advanced lithium batteries.

Highly Stretchable Polyurethane Porous Membranes with Adjustable Morphology for Advanced Lithium Metal Batteries

A highly flexible, tunable morphology membrane with excellent thermal stability and ionic conductivity can endow lithium metal batteries with high power density and reduced dendrite growth. Herein, a porous Polyurethane (PU) membrane with an adjustable morphology was prepared by a simple nonsolvent-induced phase separation technique. The precise control of the final morphology of PU membranes can be achieved through appropriate selection of a nonsolvent, resulting a range of pore structures that vary from finger-like voids to sponge-like pores. The implementation of combinatorial DFT and experimental analysis has revealed that spongy PU porous membranes, especially PU-EtOH, show superior electrolyte wettability (472%), high porosity (75%), good mechanical flexibility, robust thermal dimensional stability (above 170 °C), and elevated ionic conductivity (1.38 mS cm-1) in comparison to the polypropylene (PP) separator. The use of PU-EtOH in Li//Li symmetric cell results in a prolonged lifespan of 800 h, surpasing the longevity of PU or PP cells. Moreover, when subjected to a high rate of 5 C, the LiFePO4/Li half-cell with a PU-EtOH porous membrane displayed better cycling performance (115.4 mAh g-1) compared to the PP separator (104.4 mAh g-1). Finally, the prepared PU porous membrane exhibits significant potential for improving the efficiency and safety of LMBs.

Side Reactions/Changes in Lithium-Ion Batteries: Mechanisms and Strategies for Creating Safer and Better Batteries

Lithium-ion batteries (LIBs), in which lithium ions function as charge carriers, are considered the most competitive energy storage devices due to their high energy and power density. However, battery materials, especially with high capacity undergo side reactions and changes that result in capacity decay and safety issues. A deep understanding of the reactions that cause changes in the battery's internal components and the mechanisms of those reactions is needed to build safer and better batteries. This review focuses on the processes of battery failures, with voltage and temperature as the underlying factors. Voltage-induced failures result from anode interfacial reactions, current collector corrosion, cathode interfacial reactions, overcharge, and over-discharge, while temperature-induced failure mechanisms include SEI decomposition, separator damage, and interfacial reactions between electrodes and electrolytes. The review also presents protective strategies for controlling these reactions. As a result, the reader is offered a comprehensive overview of the safety features and failure mechanisms of various LIB components.

Recent Development in Topological Polymer Electrolytes for Rechargeable Lithium Batteries

Solid polymer electrolytes (SPEs) are still being considered as a candidate to replace liquid electrolytes for high-safety and flexible lithium batteries due to their superiorities including light-weight, good flexibility, and shape versatility. However, inefficient ion transportation of linear polymer electrolytes is still the biggest challenge. To improve ion transport capacity, developing novel polymer electrolytes are supposed to be an effective strategy. Nonlinear topological structures such as hyperbranched, star-shaped, comb-like, and brush-like types have highly branched features. Compared with linear polymer electrolytes, topological polymer electrolytes possess more functional groups, lower crystallization, glass transition temperature, and better solubility. Especially, a large number of functional groups are beneficial to dissociation of lithium salt for improving the ion conductivity. Furthermore, topological polymers have strong design ability to meet the requirements of comprehensive performances of SPEs. In this review, the recent development in topological polymer electrolytes is summarized and their design thought is analyzed. Outlooks are also provided for the development of future SPEs. It is expected that this review can raise a strong interest in the structural design of advanced polymer electrolyte, which can give inspirations for future research on novel SPEs and promote the development of next-generation high-safety flexible energy storage devices.

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

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 LiFePO₄ 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.

Low-Cost Mass Manufacturing Technique for the Shutdown-Functionalized Lithium-Ion Battery Separator Based on Al2O3 Coating Online Construction during the β-iPP Cavitation Process

A shutdown-functionalized lithium-ion battery separator plays a pivotal role in preventing thermal runaway as cells experience electrical abuse, overcharge, and external short circuit. In this article, the trilayer separator endowed with shutdown function was fabricated by ingenious co-extrusion and bidirectional drawing based on the nano-Al₂O₃ coating online construction during the β-iPP cavitation process. The middle layer composed of nano-Al₂O₃, polyethylene, and polypropylene offers a shutdown temperature of 130 °C, and skin polypropylene layers with nano-Al₂O₃ coating hold optimized dimensional stability below the meltdown temperature. Crystal structure measurement and pore structure diagnosis disclose that nano-Al₂O₃ thins coarse fibrils and makes the porous structure uniform. De-bonding of nano-Al₂O₃/β-iPP interfaces retains nano-Al₂O₃ not only on the top surface of the separator but also on the pore intine to realize nano-Al₂O₃ coating online construction, consequently strengthening tensile capacity, dimensional stability to heating, and electrolyte affinity. Electrochemical tests further disclose that nano-Al₂O₃ coating stabilizes solid electrolyte interphase germination and heightens lithium-ion migration numbers, confining cell resistances and granting optimal high-rate performance and cycling ability. The proposed approach features simple technics, environment-friendly, continuous fabrication, and coating online construction, which can offer new ideas for the mass fabricating of the high-end separator.

Thermal-Responsive and Fire-Resistant Materials for High-Safety Lithium-Ion Batteries

As one of the most efficient electrochemical energy storage devices, the energy density of lithium-ion batteries (LIBs) has been extensively improved in the past several decades. However, with increased energy density, the safety risk of LIBs becomes higher too. The frequently occurred battery accidents worldwide remind us that safeness is a crucial requirement for LIBs, especially in environments with high safety concerns like airplanes and military platforms. It is generally recognized that the catastrophic thermal runaway (TR) event is the major cause of LIBs related accidents. Tremendous efforts have been devoted to coping with the TR concerns in LIBs, and thus enhance battery safety. This review first gives an introduction to the fundamentals of LIBs and the origins of safety issues. Then, the authors summarize the recent advances to improve the safety of LIBs with a unique focus on thermal-responsive and fire-resistant materials. Finally, a perspective is proposed to guide future research directions in this field. It is anticipated this review will stimulate inspiration and arouse extensive studies on further improvement in battery safety.

Stop Four Gaps with One Bush: Versatile Hierarchical Polybenzimidazole Nanoporous Membrane for Highly Durable Li-S Battery

Lithium-sulfur (Li-S) batteries are considered as one of the most prospective candidates for electric vehicles, due to their superior theoretical energy density and low cost. However, the issues of polysulfide ion (PS) shuttling and uncontrollable Li dendrite growth hindered their further application. Herein, a multifunctional nanoporous polybenzimidazole (PBI) membrane with well-controllable morphology was successfully designed and fabricated to address the aforementioned obstacles. In this design, the PBI membrane could offer strong chemical binding interaction with PS, thus applying dynamic adsorption toward PS as well as stable sulfur electrochemistry, which is further verified by experiments and density functional theory (DFT) simulation. Moreover, PBI membranes with high porosity and high electrolyte uptake capability can provide ample lithium storage space and abundant Li⁺ supplements to facilitate Li deposition and improve Li metal batteries' cyclic stability. Besides that, the PBI membrane has excellent mechanical and thermal stability and exclusive flame resistance, which guarantees the safety of the Li-S battery as well. As a result, Li-S batteries assembled with an as-developed PBI membrane demonstrated a remarkable rate capability of 780 mAh g^-1 at 2C and an impressive reversible capacity of 523 mAh g^-1 at 0.5C after 400 cycles, which is much higher than the commercial separators. More importantly, even with a lofty sulfur loading of 3 mg cm^-2, a high discharge capacity of 744 mAh g^-1 (capacity retention 93.96%, at 0.1C after 100 cycles) can also be achieved. Overall, the current study highlighted a robust material platform for stable, safe, and efficient multifunctional separators for high-performance Li-S batteries.

Crystalline Al2O3 modified porous poly(aryl ether ketone) (PAEK) composite separators for high performance lithium-ion batteries via an electrospinning technique

The thermostability and wettability of a separator play key roles in improving the safety and electrochemical properties of lithium-ion batteries (LIBs).

A facile non-solvent induced phase separation process for preparation of highly porous polybenzimidazole separator for lithium metal battery application

The drawbacks of low porosity, inferior electrolyte wettability, low thermal dimensional stability and permissive lithium dendrite growth of the conventional microporous polyolefin-based separators hinder their widely application in the high power density and safe Lithium ion batteries. Herein, highly porous polybenzimidazole-based separator is prepared by a facile non-solvent induced phase separation process (NIPS) using water, ethanol, chloroform and ethyl acetate as the coagulation bath solvent, respectively. It was found that the ethanol is suitable to fabricate uniform morphology macroporous separator with the porosity of 92%, electrolyte uptake of 594 wt.%, and strong mechanical strength of 15.9 MPa. In addition, the experimental tests (electrochemical analysis and XPS test) and density functional theory calculation suggest that the electron-rich imidazole ring of polybenzimidazle can enhance Li⁺ mobility electrostatic attraction interaction while the block the PF₆⁻ mobility via electrostatic repulsion interaction. Therefore, high Li⁺ transference number of 0.76 was obtained for the neat polybenzimidazole-based polymer electrolyte. As a proof of concept, the Li/LiFePO₄ cell with the polybenzimidazole-based polymer electrolyte/1.0 M LiPF₆⁻ ethylene carbonate/dimethyl carbonate (v:v = 1:1) electrolyte exhibits excellent rate capability of >100 mAh g⁻¹ at 6 C (1 C = 170 mA g⁻¹) and superior cycle stability of 1000 cycles.