Interfacially stable and high-safety lithium batteries enabled by porosity engineering toward cellulose separators

Recent Advances in Polyphenylene Sulfide-Based Separators for Lithium-Ion Batteries

Polyphenylene sulfide (PPS)-based separators have garnered significant attention as high-performance components for next-generation lithium-ion batteries (LIBs), driven by their exceptional thermal stability (>260 °C), chemical inertness, and mechanical durability. This review comprehensively examines advances in PPS separator design, focusing on two structurally distinct categories: porous separators engineered via wet-chemical methods (e.g., melt-blown spinning, electrospinning, thermally induced phase separation) and nonporous solid-state separators fabricated through solvent-free dry-film processes. Porous variants, typified by submicron pore architectures (<1 μm), enable electrolyte-mediated ion transport with ionic conductivities up to >1 mS·cm-1 at >55% porosity, while their nonporous counterparts leverage crystalline sulfur-atom alignment and trace electrolyte infiltration to establish solid-liquid biphasic conduction pathways, achieving ion transference numbers >0.8 and homogenized lithium flux. Dry-processed solid-state PPS separators demonstrate unparalleled thermal dimensional stability (<2% shrinkage at 280 °C) and mitigate dendrite propagation through uniform electric field distribution, as evidenced by COMSOL simulations showing stable Li deposition under Cu particle contamination. Despite these advancements, challenges persist in reconciling thickness constraints (<25 μm) with mechanical robustness, scaling solvent-free manufacturing, and reducing costs. Innovations in ultra-thin formats (<20 μm) with self-healing polymer networks, coupled with compatibility extensions to sodium/zinc-ion systems, are identified as critical pathways for advancing PPS separators. By addressing these challenges, PPS-based architectures hold transformative potential for enabling high-energy-density (>500 Wh·kg-1), intrinsically safe energy storage systems, particularly in applications demanding extreme operational reliability such as electric vehicles and grid-scale storage.

Cellulose-Based Materials and Their Application in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are promising candidates for next-generation energy storage due to their high energy density, cost-effectiveness, and environmental friendliness. However, their commercialization is hindered by challenges, such as the polysulfide shuttle effect, lithium dendrite growth, and low electrical conductivity of sulfur cathodes. Cellulose, a natural, renewable, and versatile biopolymer, has emerged as a multifunctional material to address these issues. In anode protection, cellulose-based composites and coatings mitigate dendrite formation and improve lithium-ion diffusion, extending cycle life and enhancing safety. As separators, cellulose materials exhibit high ionic conductivity, thermal stability, and excellent wettability, effectively suppressing the polysulfide shuttle effect and maintaining electrolyte stability. For the cathode, cellulose-derived carbon frameworks and binders improve sulfur loading, conductivity, and active material retention, resulting in higher energy density and cycling stability. This review highlights the diverse roles of cellulose in Li-S batteries, emphasizing its potential to enable sustainable and high-performance energy storage. The integration of cellulose into Li-S systems not only enhances electrochemical performance but also aligns with the goals of green energy technologies. Further advancements in cellulose processing and functionalization could pave the way for its broader application in next-generation battery systems.

Environmental Sustainability of Natural Biopolymer-Based Electrolytes for Lithium Ion Battery Applications

Biopolymer based electrolytes can overcome current performance limitations of lithium-ion batteries (LIBs). Biopolymers enable electrolytes with high ionic conductivities and wide electrochemical stability windows. While the biobased character of natural materials is claimed as an inherent advantage in meeting current environmental sustainability challenges, further research is required to quantify and compare their environmental impacts as electrolytes. The challenge is addressed by identifying the most promising biopolymer electrolytes for LIBs, measuring ionic conductivities and electrochemical stability windows, and quantifying environmental impacts using life cycle assessment. The environmental impacts of the cost to isolate cellulose derivatives, nanocelluloses, chitin/nanochitin, chitosan, lignin, agar, and silk are reported for climate change, acidification, freshwater ecotoxicity, marine eutrophication, human toxicity, and water use. Material criticality, circularity index, and material circularity indicator, emerging impact categories are prioritized to help integrate biopolymers into circular and sustainable materials. The electrochemical properties and environmental impacts of natural biopolymer membrane-liquid electrolyte pairs, gel electrolytes, and solid electrolytes are quantified and benchmarked against conventional fossil-based electrolytes, providing consistent and comparable electrochemical properties of the most relevant biopolymer electrolytes fabricated so far. This study highlights the significant functional and environmental benefits of biopolymer electrolytes and identifies the most electrochemically competitive biopolymer electrolytes in LIBs.

A Full Green, Sustainable Paper-Based Packaging Material with High-Strength, Water Resistance, and Thermal Insulation

Paper-based packaging materials have gained attention from academia and industry for their outstanding environmental sustainability advantages. However, they still encounter major challenges, such as low mechanical strength and inadequate functionality, hindering the replacement of unsustainable packaging materials. Inspired by the remarkable strength of trees provided by cellulose fibers and the water and heat protection of trees provided by bark, this study developed a new biomass-based packaging material (SNC-C) that combines strength, thermal insulation, and water resistance. The material was created by simply blending straw nanocellulose (SNC) with oak bark (i.e., cork), which naturally provides water-resistant, thermal insulation, and unique regenerative properties. The dense layered structure formed entirely by SNC generates a tensile strength reaching up to 60.93 MPa. With the cork cavity structure, the heat transfer rate of the obtained material is reduced to 2.90-3.01 °C/(cm·min). The combining of the closed-cell structure and the suberin component of the cork results in a low water vapor transmission rate (WVTR) of the material of 400.30 g/(m2·24 h). This all-biomass material with excellent performance and low environmental footprint offers a promising solution for the development of sustainable multifunctional packaging materials.

Bio-Based Aerogels in Energy Storage Systems

Bio-aerogels have emerged as promising materials for energy storage, providing a sustainable alternative to conventional aerogels. This review addresses their syntheses, properties, and characterization challenges for use in energy storage devices such as rechargeable batteries, supercapacitors, and fuel cells. Derived from renewable sources (such as cellulose, lignin, and chitosan), bio-based aerogels exhibit mesoporosity, high specific surface area, biocompatibility, and biodegradability, making them advantageous for environmental sustainability. Bio-based aerogels serve as electrodes and separators in energy storage systems, offering desirable properties such as high specific surface area, porosity, and good electrical conductivity, enhancing the energy density, power density, and cycle life of devices. Recent advancements highlight their potential as anode materials for lithium-ion batteries, replacing non-renewable carbon materials. Studies have shown excellent cycling stability and rate performance for bio-aerogels in supercapacitors and fuel cells. The yield properties of these materials, primarily porosity and transport phenomena, demand advanced characterization methods, and their synthesis and processing methods significantly influence their production, e.g., sol-gel and advanced drying. Bio-aerogels represent a sustainable solution for advancing energy storage technologies, despite challenges such as scalability, standardization, and cost-effectiveness. Future research aims to improve synthesis methods and explore novel applications. Bio-aerogels, in general, provide a healthier path to technological progress.

12.6 μm-Thick Asymmetric Composite Electrolyte with Superior Interfacial Stability for Solid-State Lithium-Metal Batteries

Solid-state lithium metal batteries (SSLMBs) show great promise in terms of high-energy-density and high-safety performance. However, there is an urgent need to address the compatibility of electrolytes with high-voltage cathodes/Li anodes, and to minimize the electrolyte thickness to achieve high-energy-density of SSLMBs. Herein, we develop an ultrathin (12.6 µm) asymmetric composite solid-state electrolyte with ultralight areal density (1.69 mg cm-2) for SSLMBs. The electrolyte combining a garnet (LLZO) layer and a metal organic framework (MOF) layer, which are fabricated on both sides of the polyethylene (PE) separator separately by tape casting. The PE separator endows the electrolyte with flexibility and excellent mechanical properties. The LLZO layer on the cathode side ensures high chemical stability at high voltage. The MOF layer on the anode side achieves a stable electric field and uniform Li flux, thus promoting uniform Li+ deposition. Thanks to the well-designed structure, the Li symmetric battery exhibits an ultralong cycle life (5000 h), and high-voltage SSLMBs achieve stable cycle performance. The assembled pouch cells provided a gravimetric/volume energy density of 344.0 Wh kg-1/773.1 Wh L-1. This simple operation allows for large-scale preparation, and the design concept of ultrathin asymmetric structure also reveals the future development direction of SSLMBs.

Exploitation of function groups in cellulose materials for lithium-ion batteries applications

Cellulose, an abundant and eco-friendly polymer, is a promising raw material to be used for preparing energy storage devices such as lithium-ion batteries (LIBs). Despite the significance of cellulose functional groups in LIBs components, their structure-properties-application relationship remains largely unexplored. This article thoroughly reviews the current research status on cellulose-based materials for LIBs components, with a specific focus on the impact of functional groups in cellulose-based separators. The emphasis is on how these functional groups can enhance the mechanical, thermal, and electrical properties of the separators, potentially replacing conventional non-renewal material-derived components. Through a meticulous investigation, the present review reveals that certain functional groups, such as hydroxyl groups (-OH), carboxyl groups (-COOH), carbonyl groups (-CHO), ester functions (R-COO-R'), play a crucial role in improving the mechanical strength and wetting ability of cellulose-based separators. Additionally, the inclusion of phosphoric group (-PO3H2), sulfonic group (-SO3H) in separators can contribute to the enhanced thermal stability. The significance of comprehending the influence of functional groups in cellulose-based materials on LIBs performance is highlighted by these findings. Ultimately, this review explores the challenges and perspectives of cellulose-based LIBs, offering specific recommendations and prospects for future research in this area.

Electrospun Benzimidazole-Based Polyimide Membrane for Supercapacitor Applications

A benzimidazole-containing diamine monomer was prepared via a simple one-step synthesis process. A two-step procedure involving polycondensation in the presence of aromatic dianhydrides (4,4'-oxydiphthalic anhydride, ODPA) followed by thermal imidization was then performed to prepare a benzimidazole-based polyimide (BI-PI). BI-PI membranes were fabricated using an electrospinning technique and were hot pressed for 30 min at 200 °C under a pressure of 50 kgf /cm². Finally, the hot-pressed membranes were assembled into supercapacitors, utilizing high-porosity-activated water chestnut shell biochar as the active material. The TGA results showed that the BI-PI polymer produced in the two-step synthesis process had a high thermal stability (T_d5% = 527 °C). Moreover, the hot-press process reduced the pore size in the BI-PI membrane and improved the pore-size uniformity. The hot-press procedure additionally improved the mechanical properties of the BI-PI membrane, resulting in a high tensile modulus of 783 MPa and a tensile strength of 34.8 MPa. The cyclic voltammetry test results showed that the membrane had a specific capacitance of 121 F/g and a capacitance retention of 77%. By contrast, a commercial cellulose separator showed a specific capacitance value of 107 F/g and a capacitance retention of 49% under the same scanning conditions. Finally, the membrane showed both a small equivalent series resistance (R_s) and a small interfacial resistance (R_ct). Overall, the results showed that the BI-PI membrane has significant potential as a separator for high-performance supercapacitor applications.