Sustainable Lignin-Derived Cross-Linked Graft Polymers as Electrolyte and Binder Materials for Lithium Metal Batteries

Green Electrochemical Point-of-Care Devices: Transient Materials and Sustainable Fabrication Methods

The spread of point-of-care (PoC) diagnostic tests using electrochemical sensors poses a significant environmental challenge, especially in limited-resource settings due to the lack of waste management infrastructure. This issue is expected to intensify with the emergence of the Internet of Medical Things (IoMT), necessitating eco-friendly solutions for disposable devices. This review discusses efforts to develop green and sustainable PoC diagnostic devices, clarifying terms like biodegradability and transient electronics. It explores potential transient and biodegradable materials and fabrication technologies, emphasizing sustainable electronics with low-energy consumption and low-carbon footprint techniques, particularly favoring printing methods. The review highlights examples of necessary electronic components containing biodegradable materials for electrochemical PoC devices and discusses their role in device sustainability. Finally, it examines the feasibility of integrating these components and technologies into comprehensive biodegradable PoC devices, addressing the imminent need for eco-friendly solutions in diagnostic testing. This comprehensive discussion serves as a guide for researchers and developers striving to mitigate the environmental impact of PoC testing in the era of IoMT and personalized medicine.

Synthesis of lignin-based elastomers via ARGET ATRP: Exceptional mechanical strength, adhesion, and self-repair properties

In this study, ARGET ATRP method was employed to graft two functional monomers from lignin, resulting in the synthesis of a series of Lignin-graft-poly(lauryl methacrylate-co-cyclohexyl methacrylate) (Lignin-g-P(LMA-co-CMA)) copolymers with varying feed ratios and lignin content. The results demonstrate that by varying the feed ratios of the two monomers, the glass transition temperature of lignin-based elastomers can be finely tuned. Importantly, the introduction of lignin and CMA imparts outstanding mechanical properties to the lignin-based elastomers, with a maximum tensile strength reaching 20.13 MPa. The elastic recovery rate of the lignin-based elastomers was exceptional, with the elastic recovery coefficient (ER) of Lignin0.52-PLMA500 exceeding 90 %. Adhesion tests on various substrates revealed the remarkable adhesion properties of these copolymers. In particular, Lignin0.52-PLMA500 exhibited strong adhesion on both iron plate and glass substrate, with adhesion strengths of 2.23 MPa and 2.33 MPa, respectively. Notably, Lignin0.52-PLMA500 demonstrated significant self-healing ability after damage. Furthermore, the lignin-based elastomer exhibited exceptional ultraviolet absorption performance. In conclusion, the incorporation of lignin opens up a novel pathway for the development of high-strength and tough lignin-based elastomers. However，more effort still needs to be paid for increasing the adhesive properties aiming to explore more potential application field.

Toward Sustainable Polymer Materials for Rechargeable Batteries: Utilizing Natural Feedstocks and Recycling/Upcycling of Polymer Waste

The ever-increasing demand for rechargeable battery systems in the era of electric vehicles has spurred extensive research into developing polymeric components for batteries, such as separators, polymer electrolytes, and binders. However, current battery systems rely on expensive and nonrenewable resources, which potentially have a negative environmental impact. Therefore, polymer materials derived from natural resources have gained significant attention, primarily due to their cost-effective and environmentally sustainable features. Moreover, natural feedstocks often possess highly polar functional groups and high molecular weights, offering desirable electro-chemo-mechanical features when applied as battery materials. More recently, various recycling and upcycling strategies for polymeric battery components have also been proposed given the substantial waste generation from end-of-life batteries. Recycling polymeric materials includes an overall process of recovering the components from spent batteries followed by regeneration into new materials. Polymer upcycling into battery materials involves transforming daily-used plastic waste into high-value-added battery components. This review aims to give a state-of-the-art overview of contemporary methods to develop sustainable polymeric materials and recycling/upcycling strategies for various battery applications.

One-Pot Reversible Complexation-Mediated Polymerization (RCMP) from Benzylic Alcohols for Facile Access to Polymer-Grafted Lignin

One-pot synthesis of methacrylic and acrylic polymers from benzylic alcohols (R-OH) used as initiating moieties was developed. R-OH was converted to alkyl iodide (R-I), and the generated R-I was used as an initiator without purification or isolation in the subsequent reversible complexation mediated polymerization (RCMP), leading to one-pot RCMP from R-OH. As a useful application, this technique was exploited for one-pot polymer-grafting from lignin that is the second most abundant renewable carbon-source on earth and bears benzylic alcohols. The direct initiation from lignin eliminates tedious initiator attachment and purification, offering a facile access to polymer-grafted lignin. The obtained polymer-grafted lignin was utilized to form an efficient UV-absorbing film with high transparency in visible region. One-pot RCMP may serve as a practical method to obtain value-added functional lignin-polymer composites.

Biomass Separators as a "Lifesaver" for Safe and Long-Life Lithium Metal Batteries

The growth of lithium dendrites and the shuttle of polysulfides in lithium metal batteries (LMBs) have hindered their development. In LMBs, the cathode and anode are separated by a separator, although this does not solve the battery's issues. The use of biomass materials is widespread for modifying the separator due to their porous structure and abundant functional groups. LMBs perform more electrochemically when lithium ions are deposited uniformly and polysulfide shuttling is reduced using biomass separators. In this review, we analyze the growth of lithium dendrite and the shuttle of polysulfide in LMBs, summarize the types of biomass separator materials and the mechanisms of action (providing mechanical barriers, promoting uniform deposition of metal ions, capturing polysulfides, shielding polysulfide). The prospect of developing new separator materials from the perspective of regulating ion transport and physical sieving efficiency as well as the application of advanced technologies such as synchrotron radiation to characterize the mechanism of action of biomass separators is also proposed.

Radical-Scavenging Activatable and Robust Polymeric Binder Based on Poly(acrylic acid) Cross-Linked with Tannic Acid for Silicon Anode of Lithium Storage System

The design of a novel binder is required for high-capacity silicon anodes, which typically undergo significant changes during charge/discharge cycling. Hence, in this study, a stable network structure was formed by combining tannic acid (TAc), which can be cross-linked, and poly(acrylic acid)(PAA) as an effective binder for a silicon (Si) anode. TAc is a phenolic compound and representative substance with antioxidant properties. Owing to the antioxidant ability of the C-PAA/TAc binder, side reactions during the cycling were suppressed during the formation of an appropriate solid-electrolyte interface layer. The results showed that the expansion of a silicon anode was suppressed compared with that of a conventional PAA binder. This study demonstrates that cross-linking and antioxidant capability facilitate binding and provides insights into the behavior of binders for silicon anodes. The Si anode with the C-PAA/TAc binder exhibited significantly improved cycle stability and higher Coulombic efficiency in comparison to the Si anode with well-established PAA binders. The C-PAA/TAc binder demonstrated a capacity of 1833 mA h g^-1_Si for 100 cycles, which is higher than that of electrodes fabricated using the conventional PAA binder. Therefore, the C-PAA/TAc binder offers better electrochemical performance.

Bifunctional Solid-State Copolymer Electrolyte with Stabilized Interphase for High-Performance Lithium Metal Battery in a Wide Temperature Range

Solid-state polymer electrolytes (SPEs) are expected to guarantee safe and durable operations of lithium metal batteries (LMBs). Herein, inspired by the salutary poly(vinyl ethylene carbonate) (PVEC) component in the solid electrolyte interphase, cross-linking vinyl ethylene carbonate and ionic liquid copolymers were synthesized by in-situ polymerization to serve as polymer electrolyte for LMBs. On one hand, due to rich ester bonds of PVEC, Li⁺ could transfer by coupling/decoupling with oxygen atoms. On the other hand, the imidazole ring of ionic liquid could facilitate the dissociation of lithium salt to promote the free movement of Li⁺ . The bifunctional component synergistically increased the ionic conductivity of the SPE to 1.97×10^-4  S cm^-1 at 25 °C. Meanwhile, it also showed a wide electrochemical window, superior mechanical properties, outstanding non-combustibility, and excellent interfacial compatibility. The bifunctional copolymer-based LiFePO₄ batteries could normally operate at 0 to 60 °C, making them a promising candidate for wide-temperature-rang LMBs.

Lignin-Based Materials for Sustainable Rechargeable Batteries

This review discusses important scientific progress, problems, and prospects of lignin-based materials in the field of rechargeable batteries. Lignin, a component of the secondary cell wall, is considered a promising source of biomass. Compared to cellulose, which is the most extensively studied biomass material, lignin has a competitive price and a variety of functional groups leading to broad utilization such as adhesive, emulsifier, pesticides, polymer composite, carbon precursor, etc. The lignin-based materials can also be applied to various components in rechargeable batteries such as the binder, separator, electrolyte, anode, and cathode. This review describes how lignin-based materials are adopted in these five components with specific examples and explains why lignin is attractive in each case. The electrochemical behaviors including charge-discharge profiles, cyclability, and rate performance are discussed between lignin-based materials and materials without lignin. Finally, current limitations and future prospects are categorized to provide design guidelines for advanced lignin-based materials.

Polyacrylic acid and β-cyclodextrin polymer cross-linking binders to enhance capacity performance of silicon/carbon composite electrodes in lithium-ion batteries

Binders play a key role in maintaining the integrity of high-capacity silicon anodes, which otherwise experience serious capacity decay during cycling caused by huge volume variation of the silicon. With an aim to developing a highly efficient polymeric binder to mitigate this capacity decay, we present a novel binder synthesized from polyacrylic acid (PAA) and polymerized β-cyclodextrin (β-CDp) for Si anodes for the lithium-ion batteries. This PAA-β-CDp binder has a 3D network structure, which provides strong adhesion between the active material and the current collector. PAA-β-CDp binder makes silicon anode achieve a specific capacity of 2326.4 mAhg^-1 at the current density of 0.2 A g^-1 with a capacity retention of 64.6% after 100 cycles. The experimental results show that the PAA-β-CDp binder can effectively mitigate the huge volume change and improve the capacity and cycling performance of Si anodes.

Application of Guar Gum and its Derivatives as Green Binder/Separator for Advanced Lithium-Ion Batteries

Since their first commercialization in the 1990s,lithium-ion batteries (LIBs) have become an indispensible part of our everyday life in particular for portable electronic devices. LIBs have been considered as the most promising sustainable high energy density storage device. In recent years, there is a strong demand of LIBs for hybrid electric and electric vehicles to lower carbon footprint and mitigate climate change. However, LIBs have several issues, for example, high cost and safety issues such as over discharge, intolerance to overcharge, high temperature operation etc. To address these issues several new types of electrodes are being studied. Traditional binder PVDF is costly, difficult to recyle, undergoes side reactions at high temperature and cannot stabilize high energy density electrodes. To overcome these challenges, diiferent binders have been introduced with these electrodes. This minireview is focused on the application of guar gum as a binder for different electrodes and separator. The electrochemical performance of electrodes with guar gum has been compared with other binders.

Enhanced ionic conduction in composite polymer electrolytes filled with plant biomass “lignin”

A small amount of lignin was used as a filler for composite polymer electrolytes and provided surprisingly improved ion-conductive behavior, exhibiting application potential for flexible batteries with low environmental impact.

Lithium-Conducting Branched Polymers: New Paradigm of Solid-State Electrolytes for Batteries

The past decades have witnessed rapid development of lithium-based batteries. Significant research efforts have been progressively diverted from electrodes to electrolytes, particularly polymer electrolytes (PEs), to tackle the safety concern and promote the energy storage capability of batteries. To further increase the ionic conductivity of PEs, various branched polymers (BPs) have been rationally designed and synthesized. Compared with linear polymers, branched architectures effectively increase polymer segmental mobility, restrain crystallization, and reduce chain entanglement, thereby rendering BPs with greatly enhanced lithium transport. In this Mini Review, a diversity of BPs for PEs is summarized by scrutinizing their unique topologies and properties. Subsequently, the design principles for enhancing the physical properties, mechanical properties, and electrochemical performance of BP-based PEs (BP-PEs) are provided in which the ionic conduction is particularly examined in light of the Li⁺ transport mechanism. Finally, the challenges and future prospects of BP-PEs in this rapidly evolving field are outlined.

Viability of Low Molecular Weight Lignin in Developing Thiol-Ene Polymer Electrolytes with Balanced Thermomechanical and Conductive Properties

Polymer electrolytes with high aromatic content are prepared through thiol-ene polymerization with functionalized, low molecular weight fractions of softwood pine Kraft lignin, and wheat straw/Sarkanda grass soda lignin. Differing solubility, functionality, and aromatic content of the lignin fractions vary the glass transition temperatures of the resulting polymers and the suitability for electrolyte applications. The softwood pine Kraft lignin is used as a precursor for a gel polymer electrolyte (GPE) with room temperature conductivity of 72 × 10^-7 S cm^-1 , while the wheat straw/Sarkanda grass soda lignin is utilized in solid polymer electrolytes (SPEs) with room temperature conductivity values in the range of 5 × 10^-5 - 7 × 10^-5 S cm^-1 . The lignin-based GPE displays similar conductivity but improved thermal stability to a comparable, recently reported GPE containing an allylated, monophenolic, lignin-derived, vanillin-derived monomer. The lignin-based SPEs exhibit excellent cationic transport with ion transference values up to 0.90. The promising conductivity and ion transference results reveal the potential for use of functionalized, low molecular weight wheat straw/Sarkanda grass soda lignin in SPE applications as a way to improve thermal stability, electrochemical performance, and incorporate an abundant, sustainable resource in a high performance application.

Mechanical Integrity of Conductive Carbon-Black-Filled Aqueous Polymer Binder in Composite Electrode for Lithium-Ion Battery

The mechanical stability of aqueous binder and conductive composites (BCC) is the basis of the long-term service of composite electrodes in advanced secondary batteries. To evaluate the stress evolution of BCC in composite electrodes during electrochemical operation, we established an electrochemical–mechanical model for multilayer spherical particles that consists of an active material and a solid-electrolyte-interface (SEI)-enclosed BCC. The lithium-diffusion-induced stress distribution was studied in detail by coupling the influence of SEI and the viscoelasticity of inorganic-filler-doped polymeric bonding material. It was found that tensile hoop stress plays a critical role in determining whether a composite electrode is damaged or not—and circumferential cracks may primarily initiate in BCC, rather than in other electrode components. Further, the peak tensile stress of BCC is at the interface with SEI and does not occur at full lithiation due to the relaxation nature of polymer composite. Moreover, mechanical damage would be greatly misled if neglecting the existence of SEI. Finally, the structure integrity of the binder and conductive system can be effectively improved by (1) increasing the carbon black content as much as possible in the context of meeting cell capacity requirements—it is greater than 27% and 50% for sodium alginate and the mixtures of carboxy styrene butadiene latex and sodium carboxymethyl cellulose, respectively, for composite graphite anode; (2) reducing the elastic modulus of SEI to less than that of BCC; (3) decreasing the lithiation rate.