An Ultrahigh-Capacity Dual-Ion Battery Based on a Free-Standing Graphite Paper Cathode and Flower-Like Heterojunction Anode of Tin Disulfide and Molybdenum Disulfide

Dual-ion batteries have been considered as a competitive energy-storage device. However, owing to the lack of suitable high-capacity density and rapid-charging electrode materials, designing a cost-effective and high-performance dual-ion battery is still a great challenge. Herein, an ultrahigh-capacity dual-ion battery is constructed based on a carbon-nanotubes (CNTs) containing SnS2 -MoS2 @CNTs heterojunction anode and highly crystalline free-standing graphite paper serves as cathode. The SnS2 -MoS2 @CNTs heterojunction consisting of ultrathin nanosheets was prepared via a facile two-step hydrothermal method and shows flower-like morphology and high crystallinity. Benefiting from the unique design concept, the graphite paper/SnS2 -MoS2 @CNTs dual-ion battery delivers a high capacity of 274.2 mAh g-1 at 100 mA g-1 and has an outstanding capacity retention of 95 % after 300 cycles under 400 mA g-1 . Even at a high current density of 2 A g-1 the battery still retains a considerable capacity of 112.3 mAh g-1 . More importantly, the battery shows an extremely low self-discharge of 0.006 % h-1 after resting for 24 h. Characterization using SEM and XRD further demonstrate the excellent cycling stability and good reversibility. Consequently, this constructed dual-ion battery could be a promising energy storage device and provide new insights for the design of high-performance dual-ion batteries.

A montmorillonite-modification strategy enabling long cycling stability of dual-ion batteries

Lithium‖graphite dual-ion batteries (DIBs) have received widespread attention due to their low cost and high operating voltage (nearly 5 V). However, DIBs face several challenges such as decomposition of the electrolyte under high voltage and structural deterioration of graphite. Herein, montmorillonite (MMT) is employed to generate a favorable and robust cathode electrolyte interface (CEI) layer on the graphite surface. As a result, the DIBs exhibit a 100% capacity retention for 500 cycles at 2C. Even after 1000 cycles at 5C, the capacity retention is still as high as 99%.

Stable and High-Power Calcium-Ion Batteries Enabled by Calcium Intercalation into Graphite

Calcium-ion batteries (CIBs) are considered to be promising next-generation energy storage systems because of the natural abundance of calcium and the multivalent calcium ions with low redox potential close to that of lithium. However, the practical realization of high-energy and high-power CIBs is elusive owing to the lack of suitable electrodes and the sluggish diffusion of calcium ions in most intercalation hosts. Herein, it is demonstrated that calcium-ion intercalation can be remarkably fast and reversible in natural graphite, constituting the first step toward the realization of high-power calcium electrodes. It is shown that a graphite electrode exhibits an exceptionally high rate capability up to 2 A g^-1 , delivering ≈75% of the specific capacity at 50 mA g^-1 with full calcium intercalation in graphite corresponding to ≈97 mAh g^-1 . Moreover, the capacity stably maintains over 200 cycles without notable cycle degradation. It is found that the calcium ions are intercalated into graphite galleries with a staging process. The intercalation mechanisms of the "calciated" graphite are elucidated using a suite of techniques including synchrotron in situ X-ray diffraction, nuclear magnetic resonance, and first-principles calculations. The versatile intercalation chemistry of graphite observed here is expected to spur the development of high-power CIBs.