Cross-Linked Chitosan as an Efficient Binder for Si Anode of Li-ion Batteries

We investigate the use of chitosan (CS) as a new cross-linkable and water-soluble binder for the Si anode of Li-ion batteries. In contrast to the traditional binder utilizing a hydrogen bond and/or van der Waals force-linked anode electrodes, CS can easily form a 3D network to limit the movement of Si particles through the cross-linking between the amino groups of CS and the dialdehyde of glutaraldehyde (GA). Chemical, mechanical, and morphological analyses are conducted by Fourier transform infrared spectroscopy, tensile testing, and scanning electron microscopy. The cross-linked Si/CS-GA anode exhibits an initial discharge capacity of 2782 mAh g^–1 with a high initial Coulombic efficiency of 89% and maintained a capacity of 1969 mAh g^–1 at the current density of 500 mA g^–1 over 100 cycles

Geometry-Controllable Graphene Layers and Their Application for Supercapacitors

A facile and ultrafast method for geometry controllable and vertically transformative 3D graphene architectures is demonstrated. The 2D stacked graphene layers produced by exfoliation of graphite were transformed, e.g., from horizontal to vertical, by applying electric charge (−2 V with 1–3 μAh/cm²). The three-dimensionally transformed graphene layers have maximized surface area as well as high specific capacitance, 410 F g^–1 in LiClO₄/PC electrolyte, which is 4.4 times higher than that of planar (stacked) graphene layers. Furthermore, they can remarkably exhibit 87% of retained capacitance as the scan rate is increased from 100 to 1000 mV s^–1, unlike planar graphene, which displays 61% retention under the same conditions

Epoxidized Natural Rubber/Chitosan Network Binder for Silicon Anode in Lithium-Ion Battery

Polymeric binder is extremely important for Si-based anode in lithium-ion batteries due to large volume variation during charging/discharging process. Here, natural rubber-incorporated chitosan networks were designed as a binder material to obtain both adhesion and elasticity. Chitosan could strongly anchor Si particles through hydrogen bonding, while the natural rubber could stretch reversibly during the volume variation of Si particles, resulting in high cyclic performance. The prepared electrode exhibited the specific capacities of 1350 mAh/g after 1600 cycles at the current density of 8 A/g and 2310 mAh/g after 500 cycles at the current density of 1 A/g. Furthermore, the cycle test with limiting lithiation capacity was conducted to study the optimal binder properties at varying degree of the volume expansion of silicon, and it was found that the elastic property of binder material was strongly required when the large volume expansion of Si occurred