A hydrophilic poly(methyl vinyl ether-alt-maleic acid) polymer as a green, universal, and dual-functional binder for high-performance silicon anode and sulfur cathode

Binders could play crucial or even decisive roles in the fabrication of low-cost, stable and high-capacity electrodes. This is especially the case for the silicon (Si) anodes and sulfur (S) cathodes that undergo large volume change and active material loss in lithium-ion batteries during prolonged cycles. Herein, a hydrophilic polymer poly(methyl vinyl ether-alt-maleic acid) (PMVEMA) was explored as a dual-functional aqueous binder for the preparation of high-performance silicon anode and sulfur cathode. Benefiting from the dual functions of PMVEMA, i.e., the excellent dispersion ability and strong binding forces, the as-prepared electrodes exhibit improved capacity, rate capability and long-term cycling performance. In particular, the as-prepared Si electrode delivers a high initial discharge capacity of 1346.5 mAh g^(−1) at a high rate of 8.4 A/g and maintains 834.5 mAh g^(−1) after 300 cycles at 4.2 A/g, while the as-prepared S cathode exhibits enhanced cycling performance with high remaining discharge capacities of 663.4 mAh g^(−1) after 100 cycles at 0.2 C and 487.07 mAh g^(−1) after 300 cycles at 1 C, respectively. These encouraging results suggest that PMVEMA could be a universal binder to facilitate the green manufacture of both anode and cathode for high-capacity energy storage systems.

Housing Sulfur in Polymer Composite Frameworks for Li–S Batteries

Extensive efforts have been devoted to the design of micro-, nano-, and/or molecular structures of sulfur hosts to address the challenges of lithium–sulfur(Li–S) batteries, yet comparatively little research has been carried out on the binders in Li–S batteries. Herein, we systematically review the polymer composite frameworks that confine the sulfur within the sulfur electrode, taking the roles of sulfur hosts and functions of binders into consideration. In particular, we investigate the binding mechanism between the binder and sulfur host(such as mechanical interlocking and interfacial interactions), the chemical interactions between the polymer binder and sulfur(such as covalent bonding, electrostatic bonding, etc.), as well as the beneficial functions that polymer binders can impart on Li–S cathodes, such as conductive binders, electrolyte intake, adhesion strength etc. This work could provide a more comprehensive strategy in designing sulfur electrodes for long-life, large-capacity and high-rate Li–S battery.

Poly(thiourea triethylene glycol) as a multifunctional binder for enhanced performance in lithium-sulfur batteries

A mechanically strong binder with polar functional groups could overcome the dilemma of the large volume change during charge/discharge processes and poor cyclability of lithium-sulfur batteries(LSBs).In this work,for the first time,we report the use of poly(thiourea triethylene glycol)(PTTG)as a multifunctional binder for sulfur cathodes to enhance the performance of LSBs.As expected,the PTTG binder facilitates the high performance and stability delivered by the Sulfur-PTTG cathode,including a higher reversible capacity of 825 mAh g^(-1) at 0.2 C after 80 cycles,a lower capacity fading(0.123%per cycle)over 350 cycles at 0.5 C,a higher areal capacity of 2.5 mAh cm^(-2) at 0.25 mA cm^(-2),and better rate capability of 587 mAh g^(-1) at 2 C.Such superior electrochemical performances could be attributed to PTTG's strong chemical adsorption towards polysulfides which may avoid the lithium polysulfide shuttle effect and excellent mechanical characteristics which prevents electrode collapse during cycling and allows the Sulfur-PTTG electrode to maintain robust electron and ion migration pathways for accelerated redox reaction kinetics.