Copolymer-assisted Polypropylene Separator for Fast and Uniform Lithium Ion Transport in Lithium-ion Batteries

Interfacial Engineering of Polymer Solid-State Lithium Battery Electrolytes and Li-Metal Anode: Current Status and Future Directions

A combination of material innovations, advanced manufacturing, battery management systems, and regulatory standards is necessary to improve the energy density and safety of lithium (Li) batteries. High-energy-density solid-state Li-batteries have the potential to revolutionize industries and technologies, making them a research priority. The combination of improved safety and compatibility with high-capacity electrode materials makes solid-stateLi-batteries with polymer solid-electrolytes an attractive option for applications where energy density and safety are critical. While polymer-based solid-state Li-batteries hold enormous promise, there are still several challenges that must be addressed, particularly regarding interface between polymer solid-electrolyte and Lianode. There are significant advancements in improving the performance of solid-state Li batteries, and researchers continue to explore new methods to address these challenges. These improvements are critical for enabling the widespread adoption of solid-state Li-batteries invariety of applications, from electrical vehicles to portable electronics. Here, common polymer solid-electrolyte and its interface challenges with Lianode are first introduced, highlighting the trend in polymer solid-state-electrolyte research toward enhancing stability, safety, and performance of solid-state Li-batteries. This includes developing novel polymer materials with improved properties, exploring advanced fabrication techniques, and integrating these electrolytes into battery designs that optimize both safety and energy density.

Halloysite nanotubes enhanced polyimide/oxidized-lignin nanofiber separators for long-cycling lithium metal batteries

The high energy density and robust cycle properties of lithium-ion batteries contribute to their extensive range of applications. Polyolefin separators are often used for the purpose of storing electrolytes, hence ensuring the efficient internal ion transport. Nevertheless, the electrochemical performance of lithium-ion batteries is constrained by its limited interaction with electrolytes and poor capacity for cation transport. This work presents the preparation of a new bio-based nanofiber separator by combining oxidized lignin (OL) and halloysite nanotubes (HNTs) with polyimide (PI) using an electrospinning technique. Analysis was conducted to examine and compare the structure, morphology, thermal characteristics, and EIS of the separator with those of commercially available polypropylene separator (PP). The results indicate that the PI@OL and PI-OL@ 10 % HNTs separators exhibit higher lithium ion transference number and ionic conductivity. Moreover, the use of HNTs successfully impeded the proliferation of lithium dendrites, hence exerting a beneficial impact on both the cycle performance and multiplier performance of the battery. Consequently, after undergoing 300 iterations, the battery capacity of LiFePO4|PI-OL@ 10 % HNTs|Li stays at 92.1 %, surpassing that of PP (86.8 %) and PI@OL (89.6 %). These findings indicate that this new bio-based battery separator (PI-OL@HNTs) has the great potential to serve as a substitute for the commonly used PP separator in lithium metal batteries.

Constructing an Anion-Braking Separator to Regulate Local Li+ Solvation Structure for Stabilizing Lithium Metal Batteries

Lithium metal batteries (LMBs) offer significant advantages in energy density and output voltage, but they are severely limited by uncontrollable Li dendrite formation resulting from uneven Li+ behaviors and high reactivity with potential co-solvent plating. Herein, to uniformly enhance the Li behaviors in desolvation and diffusion, the local Li+ solvation shell structure is optimized by constructing an anion-braking separator, hence dynamically reducing the self-amplifying behavior of dendrites. As a prototypal, two-dimensional lithiated-montmorillonite (LiMMT) is blade-coated on the commercial separator, where abundant -OH groups as Lewis acidic sites and electron acceptors could selectively adsorb corresponding FSI- anions, regulating the solvation shell structure and restricting their migration. Meanwhile, the weakened anion mobility delays the time of breaking electrical neutrality, and the Li nucleation density is quantified through the respective experimental, theoretical and spectroscopical results, providing a comprehensive understanding of modifying anion and cation behaviors on dendritic growth suppression. As anticipated, a long Li plating/stripping lifespan up to 1800 h and a significantly increased average Coulombic efficiency of 98.8% are achieved under 3.0 mAh cm-2. The fabricated high-loading Li-LFP or Li-NCM523 full-cells display the cycle durability with enhanced capacity retention of nearly 100%, providing the instructive guide towards realizing dendrite-free LMBs.

Engineering Polymer-Based Porous Membrane for Sustainable Lithium-Ion Battery Separators

Due to the growing demand for eco-friendly products, lithium-ion batteries (LIBs) have gained widespread attention as an energy storage solution. With the global demand for clean and sustainable energy, the social, economic, and environmental significance of LIBs is becoming more widely recognized. LIBs are composed of cathode and anode electrodes, electrolytes, and separators. Notably, the separator, a pivotal and indispensable component in LIBs that primarily consists of a porous membrane material, warrants significant research attention. Researchers have thus endeavored to develop innovative systems that enhance separator performance, fortify security measures, and address prevailing limitations. Herein, this review aims to furnish researchers with comprehensive content on battery separator membranes, encompassing performance requirements, functional parameters, manufacturing protocols, scientific progress, and overall performance evaluations. Specifically, it investigates the latest breakthroughs in porous membrane design, fabrication, modification, and optimization that employ various commonly used or emerging polymeric materials. Furthermore, the article offers insights into the future trajectory of polymer-based composite membranes for LIB applications and prospective challenges awaiting scientific exploration. The robust and durable membranes developed have shown superior efficacy across diverse applications. Consequently, these proposed concepts pave the way for a circular economy that curtails waste materials, lowers process costs, and mitigates the environmental footprint.

Fabrication of Composite Gel Electrolyte and F-Doping Carbon/Silica Anode from Electro-Spun P(VDF-HFP)/Silica Composite Nanofiber Film for Advanced Lithium-Ion Batteries

The aim of this work is to effectively combine the advantages of polymer and ceramic nanoparticles and improve the comprehensive performance of lithium-ion batteries (LIBs) diaphragm. A flexible film composed of electro-spun P(VDF-HFP) nanofibers covered by a layer of mesoporous silica (P(VDF-HFP)@SiO₂) was synthesized via a sol-gel transcription method, then used as a scaffold to absorb organic electrolyte to make gel a electrolyte membrane (P(VDF-HFP)@SiO₂-GE) for LIBs. The P(VDF-HFP)@SiO₂-GE presents high electrolyte uptake (~1000 wt%), thermal stability (up to ~350 °C), ionic conductivity (~2.6 mS cm^-1 at room temperature), and excellent compatibility with an active Li metal anode. Meanwhile, F-doping carbon/silica composite nanofibers (F-C@SiO₂) were also produced by carbonizing the P(VDF-HFP)@SiO₂ film under Ar and used to make an electrode. The assembled F-C@SiO₂|P(VDF-HFP)@SiO₂-GE|Li half-cell showed long-cycle stability and a higher discharge specific capacity (340 mAh g^-1) than F-C@SiO₂|Celgard 2325|Li half-cell (175 mAh g^-1) at a current density of 0.2 A g^-1 after 300 cycles, indicating a new way for designing and fabricating safer high-performance LIBs.

Functional separators towards the suppression of lithium dendrites for rechargeable high-energy batteries

Lithium metal battery (LMB) is considered to be one of the most promising electrochemical energy storage devices due to the high theoretical specific capacity and the lowest redox potential of metallic lithium; however, some key issues caused by lithium dendrites on the lithium metal anode seriously hinder its real-world applications. As an indispensable part of LMBs, the separator could serve as a physical barrier to prevent direct contact of the two electrodes and control ionic transport in batteries; it is an ideal platform for the suppression of lithium dendrites. In this review, the mechanism of lithium dendrite nucleation and growth are firstly discussed and then some advanced techniques are introduced for the precise characterization of lithium dendrites. On the basis of dendritic nucleation and growth principle, several feasible strategies are summarized for suppressing lithium dendrites by utilizing functional separators, including providing a mechanical barrier, promoting homogeneous lithium deposition, and regulating ionic transport. Finally, some challenges and prospects are proposed to clear the future development of functional separators. We anticipate that this paper will provide a new insight into the design and construction of functional separators for addressing the issues of lithium dendrites in high-energy batteries.