Carvalho Diogo Vieira, Loeffler Nicholas, Kim Guk-Tae, Marinaro Mario, Wohlfahrt-Mehrens Margret, Passerini Stefano
Helmholtz Institute Ulm (HIU), Helmholtzstrasse 11, 89081 Ulm, Germany.
Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021 Karlsruhe, Germany.
Polymers (Basel). 2016 Aug 2;8(8):276. doi: 10.3390/polym8080276.
This work elucidates the manufacturing of lithium titanate (Li₄Ti₅O, LTO) electrodes via the aqueous process using sodium carboxymethylcellulose (CMC), guar gum (GG) or pectin as binders. To avoid aluminum current collector dissolution due to the rising slurries' pH, phosphoric acid (PA) is used as a pH-modifier. The electrodes are characterized in terms of morphology, adhesion strength and electrochemical performance. In the absence of phosphoric acid, hydrogen evolution occurs upon coating the slurry onto the aluminum substrate, resulting in the formation of cavities in the coated electrode, as well as poor cohesion on the current collector itself. Consequently, the electrochemical performance of the coated electrodes is also improved by the addition of PA in the slurries. At a 5C rate, CMC/PA-based electrodes delivered 144 mAh·g, while PA-free electrodes reached only 124 mAh·g. When GG and pectin are used as binders, the adhesion of the coated layers to the current collector is reduced; however, the electrodes show comparable, if not slightly better, electrochemical performance than those based on CMC. Full lithium-ion cells, utilizing CMC/PA-made Li[NiMnCo]O₂ (NMC) cathodes and LTO anodes offer a stable discharge capacity of ~120 mAh·g with high coulombic efficiencies.
本工作阐明了通过水相法使用羧甲基纤维素钠（CMC）、瓜尔胶（GG）或果胶作为粘合剂来制造钛酸锂（Li₄Ti₅O，LTO）电极。为避免由于浆料pH值升高导致铝集流体溶解，使用磷酸（PA）作为pH调节剂。对电极的形态、粘附强度和电化学性能进行了表征。在没有磷酸的情况下，将浆料涂覆到铝基板上时会发生析氢现象，导致涂覆电极中形成空洞，以及集流体本身的内聚力较差。因此，在浆料中添加PA也提高了涂覆电极的电化学性能。在5C倍率下，基于CMC/PA的电极放电容量为144 mAh·g，而不含PA的电极仅为124 mAh·g。当使用GG和果胶作为粘合剂时，涂层与集流体的粘附力降低；然而，这些电极的电化学性能与基于CMC的电极相当，甚至略好。使用由CMC/PA制成的Li[NiMnCo]O₂（NMC）阴极和LTO阳极的全锂离子电池具有约120 mAh·g的稳定放电容量和高库仑效率。
