Rechargeable lithium/iodine (Li/I) batteries have attracted much attention because of their high gravimetric/volumetric energy densities, natural abundance and low cost. However, problems of the system, such as highly unstable iodine species under high temperature, their subsequent dissolution in electrolyte and continually reacting with lithium anode prevent the practical use of rechargeable Li/I cells. A polymer-iodine composite (polyvinylpyrrolidone-iodine) with high thermostability is employed as cathode material in rechargeable Li/I battery with an organic electrolyte. Because of the chemical interaction between polyvinylpyrrolidone (PVP) and polyiodide, most of the polyiodide in the cathode could be effectively trapped during charging/discharging. In-situ Raman observation revealed the evolution of iodine species in this system could be controlled during the process of I ↔ I ↔ I. Herein, the Li/I battery delivered a high discharge capacity of 278 mAh g at 0.2 C and exhibited a very low capacity decay rate of 0.019% per cycle for prolonged 1100 charge/discharge cycles at 2 C. More importantly, a high areal capacity of 4.1 mAh cm was achieved for the electrode with high iodine loading of 21.2 mg cm. This work may inspire new approach to design the Li/I (or Li/polyiodide) system with long cycle life.
HIGHLIGHTS • N-Ti 3 C 2 @CNT microspheres are successfully synthesized by the simple spray drying and one-step pyrolysis. • Within the microsphere, MXene nanosheets intimately interact with CNTs constructing porous and highly conductive network, which can provide strong immobilization for polysulfides. • N-Ti 3 C 2 @CNT microsphere/S cathode shows highly cycling stability in lithium-sulfur battery. ABSTRACT Herein, N-Ti 3 C 2 @CNT microspheres are successfully synthesized by the simple spray drying method. In the preparation process, HCl-treated melamine (HTM) is selected as the sources of carbon and nitrogen. It not only realizes in situ growth of CNTs on the surface of MXene nanosheets with the catalysis of Ni, but also introduces efficient N-doping in both MXene and CNTs. Within the microsphere, MXene nanosheets interconnect with CNTs to form porous and conductive network. In addition, N-doped MXene and CNTs can provide strong chemical immobilization for polysulfides and effectively entrap them within the porous microspheres. Above-mentioned merits enable N-Ti 3 C 2 @CNT microspheres to be ideal sulfur host. When used in lithium-sulfur (Li-S) battery, the N-Ti 3 C 2 @CNT microspheres/S cathode delivers initial specific capacity of 927 mAh g −1 at 1 C and retains high capacity of 775 mAh g −1 after 1000 cycles with extremely low fading rate (FR) of 0.016% per cycle. Furthermore, the cathode still shows high cycling stability at high Crate of 4 C (capacity of 647 mAh g −1 after 650 cycles, FR 0.027%) and high sulfur loading of 3 and 6 mg cm −2 for Li-S batteries.
We introduced the nanoconcept in the oxide solid electrolyte Li7La3Zr2O12 (LLZO). All-solid-state Li/LiFePO4 (LFPO) cell using this solid electrolyte with thickness of several micrometers was assembled with appropriate solvent, dispersant, adhesives, and surfactant without cold- or hot-pressing. At room temperature, the Li/LLZO/LFPO cell showed the first discharge capacity of 160.4 mAh g–1, which was 94.4% of the theoretical capacity of LFPO, and the cell provided a discharge capacity of 136.8 mAh g–1 after 100 cycles. At 60 °C, the battery presented more stable electrochemical performance. The capacity loss during cycles 2–100 was only 0.06% (0.7 mAh g–1). The excellent performance could be attributed to the ultrathin solid electrolyte film.
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