A bacterial cellulose-based separator with tunable pore size for lithium-ion batteries

Unveiling potential of cellulose gel electrolyte: Molecular engineering for enhanced electrostatic interactions with Mg adatoms in Mg-ion battery

The Mg-ion battery faces significant limitations due to its liquid electrolyte, which suffers from inherent issues such as leakage and the growth of Mg dendrites. In contrast, gel polymer electrolytes (GPEs) offer heightened safety, a wide voltage window, and excellent flexibility, making them a promising alternative with outstanding electrochemical performance. In this study, a cyano-modified cellulose (CEC) GPE was engineered to aim at enhancing ion transportation and promoting uniform ion-flux through interactions between N and Mg2+ ions. The resulting CEC-based GPE demonstrated a high ionic conductivity of 1.73 mS cm-1 at room temperature. Furthermore, it exhibited remarkable Mg plating/stripping performance (coulombic efficiency ∼96.7 %) and compatibility with electrodes. Importantly, when employed in a Mo6S8//Mg battery configuration, the CEC GPE displayed exceptional cycle stability, with virtually no degradation observed even after 650 cycles at 1C, thereby significantly advancing Mg-ion battery technology due to its excellent electrochemical properties. This study provides valuable insights into the molecular engineering of cellulose-based GPEs.

Long-Cycling Cellulose-Based Gel Polymer Electrolyte Utilizing Nanohydrotalcite as a Li+ Transport Redistributor

The hydroxyl groups on the surface of the cellulose-based gel polymer electrolyte lead to poor interfacial compatibility due to side reactions with lithium sheets. In this paper, a novel cellulose-based gel polymer electrolyte was prepared by uniformly coating the surface of a cellulose membrane with a nanohydrotalcite/PVDF-HFP composite using electrospinning technology. This cellulose-based gel polymer electrolyte exhibits good interfacial compatibility and excellent cycling stability (91.7% specific capacity retention after 500 cycles at 0.5C). Theory and experiments have shown that nanohydrotalcite on the surface of cellulose membrane can effectively prevent the contact of hydroxyl groups with lithium sheets to reduce the side reactions. In addition, nanohydrotalcite can also act as a Li+ transport redistributor to facilitate the uniform deposition of Li+ and reduce the formation of lithium dendrites to extend the cycle life.

Effects of heterogeneous surface characteristics on hemocompatibility and cytocompatibility of bacterial nanocellulose

The surface properties of cardiovascular biomaterials play a critical role in their biological responses. Although bacterial nanocellulose (BNC) materials have exhibited potential applications in cardiovascular implants, the impact of their surface characteristics on biocompatibility has rarely been studied. This study investigated the mechanism for the biocompatibility induced by the physicochemical properties of both sides of BNC. With greater wettability and smoothness, the upper BNC surface reduced protein adsorption by 25 % compared with the lower surface. This prolonged the plasma re-calcification time by 14 % in venous blood. Further, compared with the lower BNC surface, the upper BNC surface prolonged the activated partial thromboplastin time by 5 % and 4 % in arterial and venous blood, respectively. Moreover, the lower BNC surface with lesser rigidity, higher roughness, and sparser fiber structure promoted cell adhesion. The lower BNC surface enhanced the proliferation rate of L929 and HUVECs cells by 15 % and 13 %, respectively, compared with the upper BNC surface. With lesser stiffness, the lower BNC surface upregulated the expressions of CD31 and eNOS while down-regulating the ICAM-1 expression - This promoted the proliferation of HUVECs. The findings of this study will provide valuable insights into the design of blood contact materials and cardiovascular implants.

Eco-Friendly Lithium Separators: A Frontier Exploration of Cellulose-Based Materials

Lithium-ion batteries, as an excellent energy storage solution, require continuous innovation in component design to enhance safety and performance. In this review, we delve into the field of eco-friendly lithium-ion battery separators, focusing on the potential of cellulose-based materials as sustainable alternatives to traditional polyolefin separators. Our analysis shows that cellulose materials, with their inherent degradability and renewability, can provide exceptional thermal stability, electrolyte absorption capability, and economic feasibility. We systematically classify and analyze the latest advancements in cellulose-based battery separators, highlighting the critical role of their superior hydrophilicity and mechanical strength in improving ion transport efficiency and reducing internal short circuits. The novelty of this review lies in the comprehensive evaluation of synthesis methods and cost-effectiveness of cellulose-based separators, addressing significant knowledge gaps in the existing literature. We explore production processes and their scalability in detail, and propose innovative modification strategies such as chemical functionalization and nanocomposite integration to significantly enhance separator performance metrics. Our forward-looking discussion predicts the development trajectory of cellulose-based separators, identifying key areas for future research to overcome current challenges and accelerate the commercialization of these green technologies. Looking ahead, cellulose-based separators not only have the potential to meet but also to exceed the benchmarks set by traditional materials, providing compelling solutions for the next generation of lithium-ion batteries.

Construction of greenly biodegradable bacterial cellulose/UiO-66-NH2 composite separators for efficient enhancing performance of lithium-ion battery

The disposal of waste lithium batteries, especially waste separators, has always been a problem, incineration and burial will cause environmental pollution, therefore, the development of degradable and high-performance separators has become an important challenge. Herein, UiO-66-NH2 particles were successfully anchored onto bacterial cellulose (BC) separators by epichlorohydrin (ECH) as a crosslinker, then a BC/UiO-66-NH2 composite separator was prepared by vacuum filtration. The ammonia groups (-NH2) from UiO-66-NH2 can form hydrogen bonds with PF6- in the electrolyte, promoting lithium-ion transference. Additionally, UiO-66-NH2 can store the electrolyte and tune the porosity of the separator. The lithium ion migration number (0.62) of the battery assembled with BC/UiO-66-NH2 composite separator increased by 50 % compared to the battery assembled with commercial PP separator (0.45). The discharge specific capacity of the battery assembled with BC/UIO-66-NH2 composite separator after 50 charge and discharge cycles is 145.4 mAh/g, which is higher than the average discharge specific capacity of 114.3 mAh/g of the battery assembled with PP separator. When the current density is 2C, the minimum discharge capacity of the battery assembled with BC/UiO-66-NH2 composite separator is 85.3 mAh/g. The electrochemical performance of the BC/UiO-66-NH2 composite separator is significantly better than that of the commercial PP separator. In addition, -NH2 can offer a nitrogen source to facilitate degradation of the BC separators, whereby the BC/UiO-66-NH2 composite separator could be completely degraded in 15 days.

Redox-active NiS@bacterial cellulose nanofiber composite separators with superior rate capability for lithium-ion batteries

Separator is an essential component of lithium-ion batteries (LIBs), which is placed between the electrodes to impede their electrical contact and provide the transport channels for lithium ions. Traditionally, the separator contributes the overall mass of LIBs, thereby reducing the gravimetric capacity of the devices. Herein, a dual-layer redox-active cellulose separator is designed and fabricated to enhance the electrochemical performances of LIBs by introducing NiS. The presented separator is composed of an insulating bacterial cellulose (BC) nanofiber layer and a conductive, and redox-active NiS@BC/carbon nanotubes layer. By using the NiS@BC separator, the discharge capacity of the LiFePO4//Li half battery is enhanced to 117 mAh g-1 at a current of 2C owing to the redox-activity of NiS. Moreover, the functional separator-electrode interface can facilitate the homogenous Li stripping/plating and depress the polarization upon the repeated stripping/plating process. Consequently, the battery containing the redox-active separator exhibits outstanding cycle stability and rate capability. The present study contributes a novel strategy for the developments of functional separators to improve the electrochemical properties of LIBs.

Facile fabrication of regenerated cellulose-based separators for high-performance lithium-ion batteries by regulating degrees of polymerization

Cellulose-based separators have great application prospects in the field of lithium-ion batteries (LIBs) due to their excellent wettability and thermal stability. However, most current cellulose-based separators come from high-cost nanocellulose and bacterial cellulose. Herein, regenerated cellulose (RC) separators were prepared from dissolving pulp with different degrees of polymerization (DPs) by using the NaOH/urea/thiourea dissolution system as well as a nonsolvent-induced phase separation method. The results showed that the DP of cellulose had a significant influence on the mechanical properties, pore structure, and electrochemical properties of the resultant RC separator. An appropriate increase in the DP could improve the mechanical strength, porosity, and ionic conductivity of the separator. The RC separator with a DP of 599 exhibited the best performance with a porosity of 56.1 %, an average pore size of 305 nm, an electrolyte uptake of 339 %, a tensile strength of 38.3 MPa, and an ionic conductivity of 1.88 mS·cm-1. The lithium-ion battery prepared with the optimal RC separator had a specific capacity of 156.55 mAh/g for 100 cycles at a current density of 0.5 C and a coulombic efficiency of more than 96 %, which was a clear advantage over the commercially available Celgard2400 and cellulose separators. This work makes contributions to the development of high-performance LIBs separators from cellulose.

Chitosan nanofiber paper used as separator for high performance and sustainable lithium-ion batteries

Separators are indispensable components in lithium-ion batteries (LIBs), providing efficient pathways for lithium ions to travel and isolating the positive and negative electrodes to avoid short circuits. However, traditional polyolefin-based separators exhibit inferior electrolyte affinities, limited porosities, and low thermal stabilities. In this study, a novel method was developed to prepare chitosan micro/nanofiber membranes as LIB separators using natural materials. The pore sizes of the chitosan micro/nanofibers separators were modulated by changing the diameters of the chitosan fibers. The results demonstrated that the chitosan nanofiber separators (CSNFs) had superior electrolyte uptake (281 %), excellent thermal dimensional stability, and electrochemical performance in LiFePO4/Li half-cell, as indicated by the higher discharge capacity after 100 cycles, and higher rate capacity than commercial Celgard2325 separator. This study paves the way for the fabrication of eco-efficient and environment-friendly separators for high-performance LIBs.

Algae-Based Biopolymers for Batteries and Biofuel Applications in Comparison with Bacterial Biopolymers-A Review

Algae-based biopolymers can be used in diverse energy-related applications, such as separators and polymer electrolytes in batteries and fuel cells and also as microalgal biofuel, which is regarded as a highly renewable energy source. For these purposes, different physical, thermochemical, and biochemical properties are necessary, which are discussed within this review, such as porosity, high temperature resistance, or good mechanical properties for batteries and high energy density and abundance of the base materials in case of biofuel, along with the environmental aspects of using algae-based biopolymers in these applications. On the other hand, bacterial biopolymers are also often used in batteries as bacterial cellulose separators or as biopolymer network binders, besides their potential use as polymer electrolytes. In addition, they are also regarded as potential sustainable biofuel producers and converters. This review aims at comparing biopolymers from both aforementioned sources for energy conversion and storage. Challenges regarding the production of algal biopolymers include low scalability and low cost-effectiveness, and for bacterial polymers, slow growth rates and non-optimal fermentation processes often cause challenges. On the other hand, environmental benefits in comparison with conventional polymers and the better biodegradability are large advantages of these biopolymers, which suggest further research to make their production more economical.

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.

Enhanced porous membrane fabrication using cellulose acetate and citric acid: Improved structural integrity, thermal stability, and gas permeability

In this study, our primary objective was to enhance the properties of porous membranes by addressing the limitations associated with phase separation. We employed a non-solvent induced phase separation (NIPS) method, utilizing cellulose acetate (CA) in conjunction with citric acid to fabricate these membranes. Citric acid played a dual role: ensuring a uniform pore structure and cross-linking the CA polymer, thereby enhancing its mechanical strength. This approach resulted in the development of a more robust membrane with superior structural integrity. Thermogravimetric analysis (TGA) confirmed enhanced thermal stability, particularly up to 150 °C, as a result of citric acid's cross-linking effect. Beyond 150 °C, the decomposition temperatures of the CA/citric acid membrane were found to be comparable to those of pure CA. Remarkably, a CA/citric acid ratio of 1:0.05 exhibited the slowest decomposition rate as the temperature increased. Scanning electron microscopy (SEM) examination unveiled a sponge-like membrane structure with numerous evenly distributed fine pores. Through the use of citric acid as a plasticizer, we were able to effectively control the penetration of water molecules, preventing the formation of macrovoids and promoting the creation of fine pores. This resulted in the fabrication of a high-porosity membrane, boasting an impressive porosity measurement of 84.9 %. Furthermore, measurements of the Gurley value confirmed efficient gas permeation, a critical characteristic for applications requiring effective gas transport. Fourier transform infrared (FT-IR) spectroscopy attested to the presence of citric acid in the membrane post-phase separation, indicating its successful integration. Our work presents a novel approach to enhance porous membranes, providing improvements in mechanical strength, thermal stability, and gas permeability. These findings offer valuable insights for the development of advanced materials with diverse applications in various fields.

Suppressing Dendrite Growth with Eco-Friendly Sodium Lignosulfonate Additive in Quasi-Solid-State Li Metal Battery

The application of lithium metal batteries is limited by the drawbacks of safety problems and Li dendrite formation. Quasi-solid-state electrolytes (QSSEs) are the most promising alternatives to commercial liquid electrolytes due to their high safety and great compatibility with electrodes. However, Li dendrite formation and the slow Li+ diffusion in QSSEs severely hinder uniform Li deposition, thus leading to Li dendrite growth and short circuits. Herein, an eco-friendly and low-cost sodium lignosulfonate (LSS)-assisted PVDF-based QSSE is proposed to induce uniform Li deposition and inhibit Li dendrite growth. Li symmetric cells with 5%-LSS QSSE possess a high Li+ transfer number of 0.79, and they exhibit a long cycle life of 1000 h at a current density/areal capacity of 1 mA cm-2/5 mAh cm-2. Moreover, due to the fast electrochemical dynamics endowed by the improved compatibility of the electrodes and fast Li+ diffusion, the LFP/5%-LSS/Li full cells still maintain a high capacity of 110 mAh g-1 after 250 cycles at 6C. This work provides a novel and promising choice that uses eco-friendly LSS as an additive to PVDF-based QSSE in Li metal batteries.

A Light-Thin Chitosan Nanofiber Separator for High-Performance Lithium-Ion Batteries

With the development of portable devices and wearable devices, there is a higher demand for high-energy density and light lithium-ion batteries (LIBs). The separator is a significant component directly affecting the performance of LIBs. In this paper, a thin and porous chitosan nanofiber separator was successfully fabricated using the simple ethanol displacement method. The thickness of the CME15 separator was about half that of mainstream commercial Celgard2325 separators. Owing to its inherent polarity and high porosity, the obtained CME15 separator achieved a small contact angle (18°) and excellent electrolyte wettability (324% uptake). The CME15 separator could maintain excellent thermal dimensional stability at 160 °C. Furthermore, the CME15 separator-based LIBs exhibited excellent cycling performance after 100 cycles (117 mAh g-1 at 1 C). The present work offers a perspective on applying a chitosan nanofiber separator in light and high-performance lithium-ion batteries (LIBs).

Improvement in bacterial cellulose production by co-culturing Bacillus cereus and Komagataeibacter xylinus

Bacterial cellulose (BC) is a bio-produced nanostructure material widely used in biomedical, food, and paper-manufacturing industries. However, low production efficiency and high-cost have limited its industrial applications. This study aimed to examine the level of improvement in BC production by co-culturing Bacillus cereus and Komagataeibacter xylinus. The BC yield in corn stover enzymatic hydrolysate was found to be obviously enhanced from 1.2 to 4.4 g/L after the aforementioned co-culturing. The evidence indicated that acetoin (AC) and 2,3-butanediol (2,3-BD) produced by B. cereus were the key factors dominating BC increment. The mechanism underlying BC increment was that AC and 2,3-BD increased the specific activity of AC dehydrogenase and the contents of adenosine triphosphate (ATP) and acetyl coenzyme A (acetyl-CoA), thus promoting the growth and energy level of K. xylinus. Meanwhile, the immobilization of BC could also facilitate oxygen acquisition in B. cereus under static conditions. This study was novel in reporting that the co-culture could effectively enhance BC production from the lignocellulosic enzymatic hydrolysate.

Advanced Sustainable Trilayer Cellulosic "Paper Separator" Functionalized with Nano-BaTiO3 for Applications in Li-Ion Batteries and Supercapacitors

In the quest of developing a sustainable, low-cost and improved separator membrane for application in energy storage devices like lithium-ion batteries (LIBs) and supercapacitors (SCs), here we fabricated a trilayer cellulose-based paper separator engineered with nano-BaTiO₃ powder. A scalable fabrication process of the paper separator was designed step-by-step by sizing with poly(vinylidene fluoride) (PVDF), thereafter impregnating nano-BaTiO₃ in the interlayer using water-soluble styrene butadiene rubber (SBR) as the binder and finally laminating the ceramic layer with a low-concentration SBR solution. The fabricated separators showed excellent electrolyte wettability (216-270%), quicker electrolyte saturation, increased mechanical strength (43.96-50.15 MPa), and zero-dimensional shrinkage up to 200 °C. The electrochemical cell comprising graphite|paper separator|LiFePO₄ showed comparable electrochemical performances in terms of capacity retention at different current densities (0.05-0.8 mA/cm²) and long-term cycleability (300 cycles) with coulombic efficiency >96%. The in-cell chemical stability as tested for 8 weeks revealed a nominal change in bulk resistivity with no significant morphological changes. The vertical burning test as performed on a paper separator showed excellent flame-retardant property, a required safety feature for separator materials. To examine the multidevice compatibility, the paper separator was tested in supercapacitors, delivering a comparable performance to that of a commercial separator. The developed paper separator was also found to be compatible with most of the commercial cathode materials such as LiFePO₄, LiMn₂O₄, and NCM111.