High energy density lithium-ion batteries with preferable cycling stability are critical for the development of all-electric vehicles. Silicon (Si) has demonstrated a remarkable potential for application as anode materials due to its superior capacity performance and worldwide abundance. However, Si intrinsically undergoes substantial volume fluctuation during repeated lithiation/delithiation processes, which pulverizes the Si particles and undermines the integrity of the electrode structures, thus resulting in frustrating cycling stability. We developed a polymer binder with a highly stretchable and elastic network structure that can accommodate volume variation of Si. This was realized by an in situ cross-linking of polyacrylic acid (PAA) with isocyanate-terminated polyurethane oligomers that consist of polyethylene glycol (PEG) chains and 2-ureido-4-pyrimidinone (UPy) moieties through the reaction between isocyanate and carboxyl during the electrode preparation process. In this binder network, PAA could strongly adhere to the Si particles by forming hydrogen bonding with the surface hydroxyl groups. The PEG chains induce the flexibility of the polymer network, while the UPy moieties endow the polymer network with desirable mechanical strength through the formation of reversible and strong quadruple H-bonding cross-linkers. This binder not only can sufficiently accommodate the volume change of Si but can also provide a strong mechanical support to effectively sustain the integrity for the Si anode, consequently enhancing cycle stability and rate performance.
To alleviate the predicament of resource shortage and environmental pollution, efficiently using abundant solar energy is a great challenge. Herein, we prepared unique photothermal conversion phase-change materials, namely, CNT@PCMs, by introducing carbon nanotubes (CNTs) used as photothermal conversion materials into the recyclable matrix of phase-change materials (PCMs). These devised CNT@PCMs cleverly combine the photothermal conversion capability of CNTs and the thermal energy storage capability of traditional PCMs. Especially, the surface temperature of the prepared CNT@PCMs can be raised to 100 °C within 165 s under the solar simulator (150 mW cm −2 ), showing a surprising heating rate that is much higher than that of the reported works and achieving a higher photothermal conversion efficiency for solar energy in this work. Furthermore, these CNT@ PCMs can hold high melting latent heat with a maximum value at 110.0 J g −1 , exhibiting remarkable thermal storage ability aside from preeminent photothermal conversion capability. Intriguingly, the introduction of dynamic oxime group−carbamate bonds into the molecular structure can endow CNT@PCMs with an outstanding self-healing performance and recyclability. The broken CNT@PCMs sample can be healed in 2 min under IR-laser irradiation. Importantly, the phase-change and mechanical properties and photothermal conversion efficiency of CNT@PCMs can also remain virtually unchanged after multiple recycles. It is of great significance to design this style of CNT@PCMs for achieving the efficient utilization of solar energy and environmental protection.
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