-cyclodextrin-acrylic acid and adamantane-acrylic acid copolymers as potential supramolecular complementary binders for the self-healing of silicon anodes in Li-Ion batteries

R. MARTIN-TRASANCOS; M.G. ORTIZ ; M.A. SANSERVINO; A. VISINTIN; G. DEL C. PIZARRO; M. V. TUNDIDOR-CAMBA; D. P. OYARZÚN; C. ZÚÑIGA

Santiago de Chile

Workshop; - 9th International Workshop on Lithium, Industrial Minerals and Energy, IWLiME; 2022

Universidad de Antofagasta

The active material of anode of commercial Lithium-ion batteries (LIBs) is carbon graphite which has a theoretical gravimetric capacity of 372 mAhg-1.1 Theoretically, silicon (Si) can enhance in one order the capacity of carbon (4200 mAhg-1). Nevertheless, their use as anode material have been hampered due to its great volume expansion (>300) upon full lithiation and the consequent looseness of contact between the electrode components and the pulverization of the material after successive cycles.2 Polymer binders capable of self-healing the Si after its expansion, is the key factor to go straightforward in use these as anode material in commercial LIBs. In this work, we synthetized and characterized linear copolymers of -cyclodextrin-polyacrylic acid (CD-PAA) and an adamantane-polyacrylic acid (Adm-PAA) as supramolecular complementary entities for the self-healing of silicon anodes in Li-ion batteries. The copolymers were synthetized via free radical polymerization by reacting mono-(6-amidoacryloyl-6-deoxy)--cyclodextrin as host, and N-(2-acrylamidoethyl)adamantane-1-carboxamide (Adm), as guest; both with acrylic acid (AA) in a molar ratio of 1/10. Water-based and N-methyl-2-pyrrolidone-based (NMP) slurries with CD-PAA and Adm-PAA as binders, silicon nanoparticles (SiNPs; 100 nm) as active anode material and carbon superP, were prepared. The slurries were deposited on copper foil (Scheme 1) and the corresponding half-cell with Li as counter electrode, were assembled. Independently of the solvent used, two cathodic peaks (0.21 V and 0.28 V) and two anodic peaks (0.34 V and 0.52 V) were observed in the cyclic voltammograms of cells. These peaks correspond to the two-step phase transition from amorphous -Si into -LixSi during lithiation and delithiation process, respectively. 3 This result indicates that the polymer binder did not hinders the access of lithium to the SiNPs. After 20 cycles at 0.1C-rate, the water-base prepared electrodes showed a gravimetric capacity of 1121 mAhg-1; a value five times higher than when uses NMP (280 mAhg-1). These results demonstrate not only the feasibility of CD-PAA and Adm-PAA as binders by using water in preparing the electrodes, but also its higher self-healing capacity with respects to the electrode prepared using NMP as solvent.