Buffering Volume Change in Solid-State Battery Composite Cathodes with CO2-Derived Block Polycarbonate Ethers

CO2-crosslinked cellulose for radiative-cooling-driven passive thermoelectric devices: one stone, two birds

Radiative-cooling-driven passive thermoelectric devices (RC-TEDs) offer a potentially sustainable energy solution. However, most RC-TED strategies utilize unsustainable polymers. Herein, a green and sustainable CO2-crosslinked cellulose (Pulp-CO2) was developed for simultaneous use as a passive radiative cooling membrane and an ionogel thermoelectric scaffold. The incorporation of CO2 in the form of carbonate group linkages in the cellulose backbone resulted in a superior passive radiative cooling effect of the membrane and improved the thermoelectric efficiency of the ionogel compared to the pure pulp. The integrated RC-TED, comprising the Pulp-CO2 membranes and ionogels, exhibited an impressive thermal voltage output of 1200 mV with a subambient temperature reduction of 5.0 °C under simulated solar radiation (280 W m-2), highlighting its potential in low-grade energy harvesting. Thus, this all-cellulose inspired RC-TED device showcases a promising and sustainable strategy for converting solar energy into electricity cost-effectively.

Quantifying the interfacial contact of active material-solid electrolyte interfaces in all-solid-state lithium-ion batteries

All-solid-state batteries (ASSBs) are being actively researched worldwide as promising next-generation alternatives to lithium-ion batteries (LIBs). To further enhance the performance of ASSBs, it is essential to quantitatively understand the contact interface between the active material and the solid electrolyte (SE) in the electrode. However, there is no established method to quantitatively evaluate this contact interface. In this study, we assessed the contact interface between the active material and the SE-which is challenging to quantify under constrained test fixture conditions-using electrochemical impedance spectroscopy (EIS). The capacitance obtained from EIS measurements served as a quantifiable indicator. We demonstrated that approximation methods enable accurate capacitance quantification under practical EIS measurement conditions (up to approximately 10 mHz) for battery development. An electrode composite, prepared using a cathode active material and a sulfide-based SE, exhibited increased capacitance with longer mixing times, confirming an improved contact interface between the active material and the SE. Capacitance was highlighted as a critical parameter, exhibiting a correlation with the forming and stacked pressures in ASSBs, and was strongly linked to cell performance. To the best of our knowledge, this study is the first to quantify the contact interface between the active material and the SE in solid-state batteries using capacitance as an indicator.

Understanding the Electrochemical Window of Solid-State Electrolyte in Full Battery Application

In recent years, solid-state Li batteries (SSLBs) have emerged as a promising solution to address the safety concerns associated. However, the limited electrochemical window (ECW) of solid-state electrolytes (SEs) remains a critical constraint full battery application. Understanding the factors that influence the ECW is an essential step toward designing more robust and high-performance electrochemical systems. This review provides a detailed classification of the various "windows" of SEs and a comprehensive understanding of the associated interfacial stability of SEs in full battery application. The paper begins with a historical overview of SE development, followed by a detailed discussion of their structural characteristics. Next, examination of various methodologies used to calculate and measure the ECW is presented, culminating in the proposal of standardized testing procedures. Furthermore, a comprehensive analysis of the numerous parameters that influence the thermodynamic ECW of SEs is provided, along with a synthesis of strategies to address these challenges. At last, this review concludes with an in-depth exploration of the interfacial issues associated with SEs exhibiting narrow ECWs in full SSLBs.

Ionic Liquid-Inspired Highly Aligned Fibrous Ionogel for Boosted Thermoelectric Harvesting

Ionogels represent promising materials for thermoelectric generators that efficiently convert low-grade heat into electricity due to their flexibility, stability, nonvolatility, and high thermopower. However, improving their thermoelectric performance presents challenges stemming from the complex interplay between ionic conductivity and thermal conduction. In this study, we developed a highly oriented nanofibrous ionogel membrane through the electrospinning of poly(ethylene oxide) (PEO) blended with a linear CO2-derived polycarbonate oligomer and an ionic liquid, ethylmethylimidazolium dicyanamide. The ionic liquid facilitated the formation of highly aligned nanofiber structures, which demonstrated superior ionic conductivity and reduced thermal conduction compared to the bulk counterparts, primarily due to the size effect inherent in nanofibers. Additionally, the incorporation of CO2-derived polycarbonate can increase the amorphous region of the PEO matrix and strengthen the ion-polymer interaction without compromising the orientation of the nanofibers thanks to its compatibility with PEO and its abundance of electron-withdrawing carbonate groups. This strategy effectively decouples ionic conductivity from thermal conduction, thereby enhancing the thermoelectric efficiency of ionogels. This advancement paves the way for the development of nanofibrous ionogels for use in flexible electronics and energy harvesting applications.

Toward High-Performance, Flexible, Photo-Assisted All-Solid-State Sodium-Metal Batteries: Screening of Solid-Polymer-Based Electrolytes Coupled with Photoelectrochemical Storage Cathodes

The advancement of photo-assisted rechargeable sodium-metal batteries with high energy efficiency, lightweight structure, and simplified design is crucial for the growing demand in portable electronics. However, addressing the intrinsic safety concerns of liquid electrolytes and the sluggish reaction kinetics in existing photoelectrochemical storage cathodes (PSCs) remains a significant challenge. In this work, functionalized light-driven composite solid electrolyte (CSE) fillers are systematically screened, and optimized PSC materials are employed to construct advanced photo-assisted solid-state sodium-metal battery (PSSMB). To further enhance the mechanical properties and poly(ethylene oxide) compatibility of the CSE, natural lignocellulose is incorporated, enabling the fabrication of flexible PSSMBs. In situ tests and density functional theory calculations reveal that the light-driven electric field facilitated sodium salt dissociation, reduced interfacial resistance, and improved ionic conductivity (0.1 mS cm-1). Meanwhile, energy-level matching of the PSC maximized the utilization of photogenerated carriers, accelerating reaction kinetics and enhancing interface compatibility between the electrolyte and cathode. The resulting flexible pouch-type PSSMB demonstrates a remarkable discharge capacity of 117 mAh g-1 and outstanding long-term cycling stability, retaining 89.1% of its capacity and achieving an energy storage efficiency of 96.8% after 300 cycles at 1 C. This study highlights a versatile strategy for advancing safe, high-performance solid-state batteries.

Toward Practical All-Solid-State Batteries: Current Status of Functional Binders

All-solid-state batteries (ASSBs) are promising candidates for next-generation energy storage devices due to their high energy density and enhanced safety. Binder plays an irreplaceable role in stabilizing the electrode structure, enhancing carrier transport and modulating solid electrolyte interfaces by connecting each component of the electrode. The development of functional binders is seen as a key strategy to achieve higher energy densities of ASSBs. This review systematically examines recent progress in binder development, focusing on their roles, impacts, and failure mechanisms in ASSBs. It begins by outlining the specific functionalities required of binders in ASSBs and provides a comprehensive summary of their applications across different components, including the anode, cathode, and solid electrolyte. Furthermore, the review highlights innovative binder design principles while also summarizing key testing methods and advanced characterization techniques for evaluating binder performance. This review proposes future directions for binder design based on current developments and emerging technologies, with the aim of creating optimal binder systems for high-energy-density applications.

Graft-to/Graft-From Synthesis of Janus Graft Copolymers for Bottlebrush Polymer Electrolytes

Janus graft copolymers, which combine the characteristics of block and graft copolymers, have been used in the fields of reaction catalysis, surface modification, and drug delivery, but their applications in lithium batteries have rarely been reported. Herein, Janus graft copolymers with polyethylene glycol (PEG) and polystyrene (PS) side chains are synthesized by combining reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) methods and doped with lithium salts to fabricate Janus bottlebrush polymer electrolytes (PEG-J-PS). The PEG side chains of the brush polymers impart good ion-conducting properties to the electrolytes, while the PS side chains improve the mechanical strength and thermal and chemical stability of the electrolytes. Notably, the PEG-J-PS can effectively improve the motility of the polymer chain segments compared to the conventional block copolymer electrolytes (PEG-b-PS). The prepared PEG-J-PS exhibits a considerable ionic conductivity of 2.06 × 10-5 S cm-1 at 30 °C and high tensile stress (2.39 MPa) and tensile strain (143%) of the PEG45-J-PS20 owing to its Janus graft structure.

Challenges and Strategies of Low-Pressure All-Solid-State Batteries

All-solid-state batteries (ASSBs) are regarded as promising next-generation energy storage technology owing to their inherent safety and high theoretical energy density. However, achieving and maintaining solid-solid electronic and ionic contact in ASSBs generally requires high-pressure fabrication and high-pressure operation, posing substantial challenges for large-scale production and application. In recent years, significant efforts are made to address these pressure-related challenges. In this review, the impact of pressure on ASSBs is explored. First, the categories, origins, and challenges associated with pressure in ASSBs are outlined. Second, an overview of recent advancements in addressing pressure-related issues in ASSBs is provided, focusing on electrode materials and their interfaces with various solid-state electrolytes (SSEs). Third, advanced characterizations and simulations employed to unravel the intricate electrochemical-mechanical interactions in ASSBs are examined. Finally, existing strategies and the insights on achieving low-stack-pressure ASSBs are presented.

Lithium Borate Polycarbonates for High-Capacity Solid-State Composite Cathodes

Improving composite cathode function is key to the success of the solid-state battery. Maximizing attainable cathode capacity and retention requires integrating suitable polymeric binders that retain a sufficiently high ionic conductivity and long-term chemo-mechanical stability of the cathode active material-solid-electrolyte-carbon mixture. Herein, we report block copolymer networks composed of lithium borate polycarbonates and poly(ethylene oxide) that improved the capacity (200 mAh g-1 at 1.75 mA cm-2) and capacity retention (94 % over 300 cycles) of all-solid-state composite cathodes with nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode active material, Li6PS5Cl solid electrolyte, and carbon. Tetrahedral B(OR)2(OH)2 - anions immobilized on the polycarbonate segments provide hydrogen-bonding chain crosslinking and selective Li-counterion conductivity, parameterized by Li-ion transference numbers close to unity (tLi+~0.94). With 90 wt % polycarbonate content and a flexible low glass transition temperature backbone, the single-ion conductors achieved high Li-ion conductivities of 0.2 mS cm-1 at 30 °C. The work should inform future binder design for improving the processability of cathode composites towards commercializing solid-state batteries, and allow use in other cell configurations, such as lithium-sulphur cathode designs.

Bridging polymer architecture, printability, and properties by digital light processing of block copolycarbonates

CO2-based aliphatic polycarbonates (aPCs), produced through the alternating copolymerization of epoxides with CO2, present an appealing option for sustainable polymeric materials owing to their renewable feedstock and degradable characteristics. An ongoing challenge in working with aPCs is modifying their mechanical properties to meet specific demands. Herein, we report that monomer ratio and polymer architecture of aPCs impact not only printability by digital light processing (DLP) additive manufacturing, but also dictate the thermomechanical and degradation properties of the printed objects. We found that block copolymers exhibit tailorable thermomechanical properties ranging from soft elastomeric to strong and brittle as the proportion of hard blocks increases, whereas the homopolymer blend failed to print objects and statistical copolymers delaminated or overcured, displaying the weakest mechanical properties. In addition, the hydrolytic degradation of the prints was demonstrated under various conditions, revealing that BCP prints containing a higher proportion of hard blocks had slower degradation and that statistical copolymer prints degraded more slowly than their BCP counterparts. This study underscores that polymer composition and architecture both play key roles in resin printability and bulk properties, offering significant prospects for advancing sustainable materials in additive manufacturing through polymer design.

Cyclic ether and anhydride ring opening copolymerisation delivering new ABB sequences in poly(ester-alt-ethers)

Poly(ester-alt-ethers) are interesting as they combine the ester linkage rigidity and potential for hydrolysis with ether linkage flexibility. This work describes a generally applicable route to their synthesis applying commercial monomers and yielding poly(ester-alt-ethers) with variable compositions and structures. The ring-opening copolymerisation of anhydrides (A), epoxides (B) and cyclic ethers (C), using a Zr(iv) catalyst, produces either ABB or ABC type poly(ester-alt-ethers). The catalysis is effective using a range of commercial anhydrides (A), including those featuring aromatic, unsaturated or tricyclic monomers, and with different alkylene oxides (epoxides, B), including those featuring aliphatic, alkene or ether substituents. The range of effective cyclic ethers (C) includes tetrahydrofuran, 2,5-dihydrofuran (DHF) or 1,4-bicyclic ether (OBH). In these investigations, the catalyst:anhydride loadings are generally held constant and deliver copolymers with degrees of copolymerisation of 25, with molar mass values from 4 to 11 kg mol-1 and mostly with narrow dispersity molar mass distributions. All the new copolymers are amorphous, they show the onset of thermal decomposition between 270 and 344 °C and variable glass transition temperatures (-50 to 48 °C), depending on their compositions. Several of the new poly(ester-alt-ethers) feature alkene substituents which are reacted with mercaptoethanol, by thiol-ene processes, to install hydroxyl substituents along the copolymer chain. This strategy affords poly(ether-alt-esters) featuring 30, 70 and 100% hydroxyl substituents (defined as % of monomer repeat units featuring a hydroxyl group) which moderate physical properties such as hydrophilicity, as quantified by water contact angles. Overall, the new sequence selective copolymerisation catalysis is shown to be generally applicable to a range of anhydrides, epoxides and cyclic ethers to produce new families of poly(ester-alt-ethers). In future these copolymers should be explored for applications in liquid formulations, electrolytes, surfactants, plasticizers and as components in adhesives, coatings, elastomers and foams.

Polymer design for solid-state batteries and wearable electronics

Solid-state batteries are increasingly centre-stage for delivering more energy-dense, safer batteries to follow current lithium-ion rechargeable technologies. At the same time, wearable electronics powered by flexible batteries have experienced rapid technological growth. This perspective discusses the role that polymer design plays in their use as solid polymer electrolytes (SPEs) and as binders, coatings and interlayers to address issues in solid-state batteries with inorganic solid electrolytes (ISEs). We also consider the value of tunable polymer flexibility, added capacity, skin compatibility and end-of-use degradability of polymeric materials in wearable technologies such as smartwatches and health monitoring devices. While many years have been spent on SPE development for batteries, delivering competitive performances to liquid and ISEs requires a deeper understanding of the fundamentals of ion transport in solid polymers. Advanced polymer design, including controlled (de)polymerisation strategies, precision dynamic chemistry and digital learning tools, might help identify these missing fundamental gaps towards faster, more selective ion transport. Regardless of the intended use as an electrolyte, composite electrode binder or bulk component in flexible electrodes, many parallels can be drawn between the various intrinsic polymer properties. These include mechanical performances, namely elasticity and flexibility; electrochemical stability, particularly against higher-voltage electrode materials; durable adhesive/cohesive properties; ionic and/or electronic conductivity; and ultimately, processability and fabrication into the battery. With this, we assess the latest developments, providing our views on the prospects of polymers in batteries and wearables, the challenges they might address, and emerging polymer chemistries that are still relatively under-utilised in this area.

Poly(ethylene oxide)- and Polyzwitterion-Based Thermoplastic Elastomers for Solid Electrolytes

In this article, ABA triblock copolymer (tri-BCP) thermoplastic elastomers with poly(ethylene oxide) (PEO) middle block and polyzwitterionic poly(4-vinylpyridine) propane-1-sulfonate (PVPS) outer blocks were synthesized. The PVPS-b-PEO-b-PVPS tri-BCPs were doped with lithium bis-(trifluoromethane-sulfonyl) imide (LiTFSI) and used as solid polyelectrolytes (SPEs). The thermal properties and microphase separation behavior of the tri-BCP/LiTFSI hybrids were studied. Small-angle X-ray scattering (SAXS) results revealed that all tri-BCPs formed asymmetric lamellar structures in the range of PVPS volume fractions from 12.9% to 26.1%. The microphase separation strength was enhanced with increasing the PVPS fraction (fPVPS) but was weakened as the doping ratio increased, which affected the thermal properties of the hybrids, such as melting temperature and glass transition temperature, to some extent. As compared with the PEO/LiTFSI hybrids, the PVPS-b-PEO-b-PVPS/LiTFSI hybrids could achieve both higher modulus and higher ionic conductivity, which were attributed to the physical crosslinking and the assistance in dissociation of Li+ ions by the PVPS blocks, respectively. On the basis of excellent electrical and mechanical performances, the PVPS-b-PEO-b-PVPS/LiTFSI hybrids can potentially be used as solid electrolytes in lithium-ion batteries.

Electrochemical coupling in subnanometer pores/channels for rechargeable batteries

Subnanometer pores/channels (SNPCs) play crucial roles in regulating electrochemical redox reactions for rechargeable batteries. The delicately designed and tailored porous structure of SNPCs not only provides ample space for ion storage but also facilitates efficient ion diffusion within the electrodes in batteries, which can greatly improve the electrochemical performance. However, due to current technological limitations, it is challenging to synthesize and control the quality, storage, and transport of nanopores at the subnanometer scale, as well as to understand the relationship between SNPCs and performances. In this review, we systematically classify and summarize materials with SNPCs from a structural perspective, dividing them into one-dimensional (1D) SNPCs, two-dimensional (2D) SNPCs, and three-dimensional (3D) SNPCs. We also unveil the unique physicochemical properties of SNPCs and analyse electrochemical couplings in SNPCs for rechargeable batteries, including cathodes, anodes, electrolytes, and functional materials. Finally, we discuss the challenges that SNPCs may face in electrochemical reactions in batteries and propose future research directions.

Advances in All-Solid-State Lithium-Sulfur Batteries for Commercialization

Solid-state batteries are commonly acknowledged as the forthcoming evolution in energy storage technologies. Recent development progress for these rechargeable batteries has notably accelerated their trajectory toward achieving commercial feasibility. In particular, all-solid-state lithium-sulfur batteries (ASSLSBs) that rely on lithium-sulfur reversible redox processes exhibit immense potential as an energy storage system, surpassing conventional lithium-ion batteries. This can be attributed predominantly to their exceptional energy density, extended operational lifespan, and heightened safety attributes. Despite these advantages, the adoption of ASSLSBs in the commercial sector has been sluggish. To expedite research and development in this particular area, this article provides a thorough review of the current state of ASSLSBs. We delve into an in-depth analysis of the rationale behind transitioning to ASSLSBs, explore the fundamental scientific principles involved, and provide a comprehensive evaluation of the main challenges faced by ASSLSBs. We suggest that future research in this field should prioritize plummeting the presence of inactive substances, adopting electrodes with optimum performance, minimizing interfacial resistance, and designing a scalable fabrication approach to facilitate the commercialization of ASSLSBs.

Current Trends and Perspectives of Polymers in Batteries

This Perspective aims to present the current status and future opportunities for polymer science in battery technologies. Polymers play a crucial role in improving the performance of the ubiquitous lithium ion battery. But they will be even more important for the development of sustainable and versatile post-lithium battery technologies, in particular solid-state batteries. In this article, we identify the trends in the design and development of polymers for battery applications including binders for electrodes, porous separators, solid electrolytes, or redox-active electrode materials. These trends will be illustrated using a selection of recent polymer developments including new ionic polymers, biobased polymers, self-healing polymers, mixed-ionic electronic conducting polymers, inorganic-polymer composites, or redox polymers to give some examples. Finally, the future needs, opportunities, and directions of the field will be highlighted.

Functional and Degradable Polyester-co-polyethers from CO2, Butadiene, and Epoxides

Carbon dioxide (CO2), as a renewable and nontoxic C1 feedstock, has been recognized as an ideal comonomer to prepare sustainable materials. In this regard, substantial focus has been dedicated to the ring-opening copolymerization of CO2 and epoxides, which results in the creation of aliphatic polycarbonates in most cases. Here, we report an unprecedented strategy to synthesize functional and degradable polyester-co-polyethers from CO2, butadiene, and epoxides via a CO2/butadiene-derived δ-valerolactone intermediate (EVP). Utilizing a chromium salen complex as the catalyst, the copolymerization of EVP and epoxides was successfully achieved to produce CO2/butadiene/epoxide terpolymers. The obtained polyester-co-polyethers with varied 39-93 mol % EVP content (equal to 18-28 wt % CO2 incorporation) show high thermal stability, tunable glass-transition temperatures, on-demand functionality, and good chemical degradability. This method extends the potential to access functional CO2-based polymers.

Towards Efficient Polymeric Binders for Transition Metal Oxides-based Li-ion Battery Cathodes

Transition metal oxide cathodes (TMOCs) such as LiNi0.8Mn0.1Co0.1O2 and LiMn1.5Ni0.5O4 have been widely employed in Li-ion batteries (LIBs) owing to superior operating voltages, high reversible capacities and relatively low cost. Nevertheless, despite significant advancements in practical application, TMOC-based LIBs face great challenges such as transition metal dissolution and volume expansion during cycling, which jeopardizes the future advance of high-voltage TMOCs. As a critical component of cathode, polymeric binder acts as a crucial part in maintaining the mechanical and ion/electron conductive integrity between active particles, carbon additives, and the aluminum collector, hence minimizing cathode pulverization during battery cycling. Moreover, Polymeric binder with specialized functions is thought to offer a new solution to enhancing the electrochemical stability of the TMOCs. Therefore, this review aims at providing a comprehensive summary of the ideal requirements, design strategies and recent progress of polymeric binders for TMOCs. Future design perspectives and promising research technologies for advanced binders for high-voltage TMOCs are introduced.

Alternatives to fluorinated binders: recyclable copolyester/carbonate electrolytes for high-capacity solid composite cathodes

Optimising the composite cathode for next-generation, safe solid-state batteries with inorganic solid electrolytes remains a key challenge towards commercialisation and cell performance. Tackling this issue requires the design of suitable polymer binders for electrode processability and long-term solid-solid interfacial stability. Here, block-polyester/carbonates are systematically designed as Li-ion conducting, high-voltage stable binders for cathode composites comprising of single-crystal LiNi0.8Mn0.1Co0.1O2 cathodes, Li6PS5Cl solid electrolyte and carbon nanofibres. Compared to traditional fluorinated polymer binders, improved discharge capacities (186 mA h g-1) and capacity retention (96.7% over 200 cycles) are achieved. The nature of the new binder electrolytes also enables its separation and complete recycling after use. ABA- and AB-polymeric architectures are compared where the A-blocks are mechanical modifiers, and the B-block facilitates Li-ion transport. This reveals that the conductivity and mechanical properties of the ABA-type are more suited for binder application. Further, catalysed switching between CO2/epoxide A-polycarbonate (PC) synthesis and B-poly(carbonate-r-ester) formation employing caprolactone (CL) and trimethylene carbonate (TMC) identifies an optimal molar mass (50 kg mol-1) and composition (wPC 0.35). This polymer electrolyte binder shows impressive oxidative stability (5.2 V), suitable ionic conductivity (2.2 × 10-4 S cm-1 at 60 °C), and compliant viscoelastic properties for fabrication into high-performance solid composite cathodes. This work presents an attractive route to optimising polymer binder properties using controlled polymerisation strategies combining cyclic monomer (CL, TMC) ring-opening polymerisation and epoxide/CO2 ring-opening copolymerisation. It should also prompt further examination of polycarbonate/ester-based materials with today's most relevant yet demanding high-voltage cathodes and sensitive sulfide-based solid electrolytes.

Polymerizable Deep Eutectic Solvent-Based Polymer Electrolyte for Advanced Dendrite-Free, High-Rate, and Long-Life Li Metal Batteries

The recently developed advanced electrolytes possess many crucial qualities, including robust stability, Li dendrite-free, and comparable interface compatibility, for the manufacturing of Li metal batteries with a high energy density. In this study, lithium bis(trifluoromethane)sulfonimide, acrylamide, and succinonitrile were first used to design a polymerizable monomer. Then, it went through in situ thermal polymerization to attain a new solid polymer electrolyte [named poly(PDES)]. The synthesized poly(PDES) electrolyte achieved higher ionic conductivity (∼1.89 × 10-3 S cm-1), oxidation potential (∼5.10 V versus Li+/Li), and a larger lithium-ion transfer number (∼0.63). Moreover, poly(PDES) was nonflammable and could effectively inhibit the formation of Li dendrites. As a result, the assembled batteries using the poly(PDES) electrolyte for both Li||LiFePO4 and Li||LiNi0.8Co0.1Mn0.1O2 exhibited excellent interface compatibility and electrochemical performances. This poly(PDES) electrolyte has promising potential for broad application in lithium-metal batteries with elevated energy density and safety performance in the near future.

Correlating Metal Redox Potentials to Co(III)K(I) Catalyst Performances in Carbon Dioxide and Propene Oxide Ring Opening Copolymerization

Carbon dioxide copolymerization is a front-runner CO2 utilization strategy but its viability depends on improving the catalysis. So far, catalyst structure-performance correlations have not been straightforward, limiting the ability to predict how to improve both catalytic activity and selectivity. Here, a simple measure of a catalyst ground-state parameter, metal reduction potential, directly correlates with both polymerization activity and selectivity. It is applied to compare performances of 6 new heterodinuclear Co(III)K(I) catalysts for propene oxide (PO)/CO2 ring opening copolymerization (ROCOP) producing poly(propene carbonate) (PPC). The best catalyst shows an excellent turnover frequency of 389 h-1 and high PPC selectivity of >99 % (50 °C, 20 bar, 0.025 mol% catalyst). As demonstration of its utility, neither DFT calculations nor ligand Hammett parameter analyses are viable predictors. It is proposed that the cobalt redox potential informs upon the active site electron density with a more electron rich cobalt centre showing better performances. The method may be widely applicable and is recommended to guide future catalyst discovery for other (co)polymerizations and carbon dioxide utilizations.

Tuning the Covalent Coupling Degree between the Cathode and Electrolyte for Optimized Interfacial Resistance in Solid-State Lithium Batteries

The development of promising solid-state lithium batteries has been a challenging task mainly due to the poor interfacial contact and high interfacial resistance at the electrode/solid-state electrolyte (SSE) interface. Herein, we propose a strategy for introducing a class of covalent interactions with varying covalent coupling degrees at the cathode/SSE interface. This method significantly reduces interfacial impedances by strengthening the interactions between the cathode and SSE. By adjusting the covalent coupling degree from low to high, an optimal interfacial impedance of 33 Ω cm^-2 was achieved, which is even lower than the interfacial impedance using liquid electrolytes (39 Ω cm^-2). This work offers a fresh perspective on solving the interfacial contact problem in solid-state lithium batteries.

One-pot synthesis of hyperbranched polymers via visible light regulated switchable catalysis

Switchable catalysis promises exceptional efficiency in synthesizing polymers with ever-increasing structural complexity. However, current achievements in such attempts are limited to constructing linear block copolymers. Here we report a visible light regulated switchable catalytic system capable of synthesizing hyperbranched polymers in a one-pot/two-stage procedure with commercial glycidyl acrylate (GA) as a heterofunctional monomer. Using (salen)CoIIICl (1) as the catalyst, the ring-opening reaction under a carbon monoxide atmosphere occurs with high regioselectivity (>99% at the methylene position), providing an alkoxycarbonyl cobalt acrylate intermediate (2a) during the first stage. Upon exposure to light, the reaction enters the second stage, wherein 2a serves as a polymerizable initiator for organometallic-mediated radical self-condensing vinyl polymerization (OMR-SCVP). Given the organocobalt chain-end functionality of the resulting hyperbranched poly(glycidyl acrylate) (hb-PGA), a further chain extension process gives access to a core-shell copolymer with brush-on-hyperbranched arm architecture. Notably, the post-modification with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) affords a metal-free hb-PGA that simultaneously improves the toughness and glass transition temperature of epoxy thermosets, while maintaining their storage modulus.