Linear poly(n-butyl acrylate)-gradient-poly(methyl methacrylate) (PBA-grad-PMMA) copolymers and SiO 2 -g-PBA-grad-PMMA particle brushes were synthesized by activator regenerated by electron transfer atom transfer radical polymerization via a semibatch copolymerization method in which the methyl methacrylate (MMA) monomer was slowly fed to the polymerizing n-butyl acrylate (BA) solutions. The effects of initial BA concentration and the MMA feeding rate on the polymerization were investigated. Controlled gradient compositions were achieved at relatively low conversion, <20%. Two gradient copolymer particle brushes, with grafting densities of 0.55 and 0.126 chains/nm 2 , and one linear gradient copolymer were prepared with the same composition. Significant changes were observed after attaching the gradient copolymer ligands onto the surface of SiO 2 nanoparticles, in both thermal and mechanical properties. Greater heterogeneity and microphase separation were introduced after the addition of SiO 2 nanoparticles, and the nanocomposites displayed more complex glass transition temperature (T g ) behavior and a broader T g range. An improvement in mechanical properties (strength and stiffness) was observed as the SiO 2 nanoparticle content increased in gradient copolymer particle brushes; however, the damping property was compromised with increasing stiffness of the materials, especially under low frequency conditions.
Dendrites and dead lithium formation over prolonged cycling have long been challenges that hinder the safe implementation of metallic Li anodes. Herein, we employ polymer-stabilized liquid metal nanoparticles (LM-P NPs) of eutectic gallium indium (EGaIn) to create uniform Li nucleation sites enabling homogeneous lithium electrodeposition. Block copolymers of poly(ethylene oxide) and poly(acrylic acid) (PEO-b-PAA) were grafted onto the EGaIn surface, forming stabilized, well-dispersed NPs. Using a scalable spray coating approach, LM-P NPs were fabricated on copper current collectors, providing lithiophilic PEO sites and interactive carboxyl groups to guide Li deposition. The Li-EGaIn alloying process greatly reduced the Li+ diffusion barrier, enabling fast Li transport through the coating layer, resulting in decreased nucleation overpotential. Therefore, about five times lower Li nucleation overpotential was obtained on the LM-P modified Cu with an optimal composition of the polymers than the bare Cu substrates. DFT computations was used to reveal the binding properties between the LM-P layer and Li. Due to the regulated Li plating/stripping process, as-obtained 30 μm Li anodes paired with LiNi0.8Co0.1Mn0.1O2 (NCM811) with a negative/positive electrode capacity (N/P) ratio ∼ 10 exhibited stable cycling performance at 0.5C for over 250 cycles, with an average Coulombic efficiency of 99.55%. Ultrathin Li (1 μm) anodes with an N/P ratio ∼ 0.6 were also demonstrated in Li|LiFePO4 cells, which examined the stabilization of Li by LM-P NPs and monitored practical loadings of Li anodes that are close to anode-free systems.
This present study illustrates the synthesis and preparation of polyoxanorbornene‐based bottlebrush polymers with poly(ethylene oxide) (PEO) side chains by ring‐opening metathesis polymerization for solid polymer electrolytes (SPE). In addition to the conductive PEO side chains, the polyoxanorbornene backbones may act as another ion conductor to further promote Li‐ion movement within the SPE matrix. These results suggest that these bottlebrush polymer electrolytes provide impressively high ionic conductivity of 7.12 × 10−4 S cm−1 at room temperature and excellent electrochemical performance, including high‐rate capabilities and cycling stability when paired with a Li metal anode and a LiFePO4 cathode. The new design paradigm, which has dual ionic conductive pathways, provides an unexplored avenue for inventing new SPEs and emphasizes the importance of molecular engineering to develop highly stable and conductive polymer electrolytes for lithium‐metal batteries (LMB).
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