Biobinder Nanocoating for Upgrading the Assembling Structures of High-Capacity Composite Electrodes with a Robust Polymeric Artificial Solid Electrolyte Interphase.

The success of next-generation lithium-ion batteries (LIBs) fundamentally depends on the rational design of not only the microstructure of an individual component but the component assembling structures on the electrode level. However, building advanced assembling structures for especially high-capacity electrodes is an urgent but a challenging task due to the lacking of in-depth understanding and effective strategies. Here, we propose a functional nanocoating biobinder using the well-known poly(lactic acid) to address the above need. It is found that the composite electrodes with this nanocoating biobinder are upgraded with uniform and robust assembling structures, including the electron-transportation network, ion-transportation network, and interfaces. Importantly, the nanocoating finally works as a new type of polymeric artificial cathode electrolyte interphase (poly-CEI) to protect the active particles. Therefore, a remarkable improvement in the electrochemical performance has been achieved for high-capacity electrodes (LiFePO4, lithium nickel cobalt manganite (NCM), and lithium nickel cobalt aluminum acid (NCA)). In particular, the LFP cathode can deliver a high discharge capacity of 74.6 mA h g-1 at 10C and a high capacity retention of 95.5% even after 850 cycles at 2C. For NCA and NCM cathodes, the cycling stability is dramatically improved due to the protection by the poly-CEI. In short, this study may reshape the essential roles of a binder in composite electrodes by highlighting its critical link to assembling structures.

Celluloses in an ionic liquid: the rheological properties of the solutions spanning the dilute and semidilute regimes.

The ionic liquid of 1-allyl-3-methylimidazolium chloride ([amim]Cl) was used as the good solvent to dissolve celluloses. Cellulose concentration covers the range of 0.1-3.0 wt %, spanning both the dilute and semidilute regimes. The rheological properties of the cellulose ionic liquid solutions have been investigated by steady shear and oscillatory shear measurements in this study. In the steady shear measurements, all the cellulose solutions show a shear thinning behavior at high shear rates; however, the dilute cellulose solutions show another shear thinning region at low shear rates, which may reflect the characteristics of the [amim]Cl solvent. In the oscillatory shear measurements, for the dilute regime, the reduced dimensionless moduli are obtained by extrapolation of the viscoelastic measurements for the dilute solutions to infinite dilution. The frequency dependences of the reduced dimensionless moduli are intermediate between the predictions from the Zimm model and elongated rodlike model theories, while the fitting by using a hybrid model combining these two model theories agrees well with the experimental results. For the semidilute regime, the frequency dependences of moduli change from the Zimm-like behavior to the Rouse-like behavior with increasing cellulose concentration. In the studied concentration range, the effects of molecular weight and temperature on solution viscoelasticities and the relationship between steady shear viscosity and dynamic shear viscosity are presented. Results show that the solution viscoelasticity greatly depends on the molecular weight of cellulose; the empirical time-temperature superposition principle holds true at the experimental temperatures, while the Cox-Merz rule fails for the solutions investigated in this study.