High-capacity storage in Li-ion batteries with graphite anodes remains a challenge at low temperature. By contrast, metal-based composite anode materials, including Sn metal, have shown good lithium storage capabilities at low temperature. However, the suitable low temperature electrolyte is still infancy to achieve high efficiency capacity of Sn-based anode in ultra-low temperature. Herein, a 2-methytetrahydrofuran (2Me-THF)-based low temperature electrolyte is proven to support the excellent lithium capability of Sn-based anode at ultra-low temperatures. The formulated 2Me-THF electrolyte exhibited small changes in viscosity and ionic conductivity with decreasing temperature. A SnO 2 -LiF-G (graphite) electrode with 1 M lithium bis(trifluoromethanesulfonyl)imide-(2Me-THF) electrolyte maintained 80% of the room temperature reversible capacity at -30°C and delivered a reversible capacity of 650 mAh g −1 , even at -50°C, under a current density of 100 mA g −1 . Furthermore, a detailed characterization based on Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy and Time-of-flight Secondary ion Mass Spectrometry confirmed that the formed inorganic-rich solid electrolyte interphase on the electrode surface effectively maintained the solid-liquid interfacial stability at low temperature. This work provided design concepts for ultralow temperature electrolytes for metal-based anodes, which were especially helpful for further promoting batteries for low temperature applications.
Sn is considered as a promising anode for lithium-ion batteries due to its low cost and high theoretical capacity (992 mA h g −1 with Li 4.4 Sn). However, the volume expansion (∼300%) during lithiation/delithiation process can result in the continuous pulverization of active materials and exfoliation from current collector, deteriorating the capacity and cycling performance. Here Co/Co 3 SnC 0.7 N-doped carbon nanofibers are successfully synthesized by a feasible electrospinning method. And the materials as the self-standing anode for lithium-ion batteries reveal a high-rate performance as delivering reversible capacities of 480 mA h g −1 at 100 mA g −1 and 290 mA h g −1 at 2000 mA g −1 . In addition, the specific capacity can still maintain 320 mA h g −1 at 500 mA g −1 even after 900 cycles, showing the outstanding cycling stability. The inactive metal Co and one-dimensional N-doped carbon nanofibers synergistically promote the electrochemical performance of the Sn-based anode by inhibiting the aggregation of the nanoparticles and buffering volume variation during lithiation/delithiation process.
Shi Chonghua,Liu Xinyu,Fu Hang,Wang Jing,Yao Shaowei
As one of the most promising high-capacity anode materials for lithium-ion batteries, Sn-based anode materials have the advantages of high capacity (994 mAh g −1 ) and low price. But the anode material has large volume expansion during the cycle process, resulting in battery capacity attenuation. Therefore, carbon wrapping is used to alleviate this problem. In this work, SnO 2 nanoparticles are coated by electrospinning technology, and microspherical Sn@C composite materials are obtained after further heat treatment. The results show that when the content of SnO 2 nanoparticles is 0.13 g, the obtained Sn@C microsphere electrode material still has a high reversible discharge specific capacity of 616.90 mAh g −1 after 100 cycles at a current density of 100 mA g −1 . When the current density is 500 mA g −1 , the specific capacity is still as high as 558.20 mAh g −1 after 500 cycles, and the Sn@C microsphere electrode material exhibits excellent electrochemical performance. This provides an idea for developing high performance anode materials for lithium-ion batteries.
Nanometerization of tin-based materials is beneficial to alleviate the volume effect, and thus improving the cycle stability of tin-based materials. Meanwhile, the smaller size can enhance the reversibility of the conversion reaction, which is crucial for increasing the capacity of tin-based materials. Therefore, reducing the size of tin-based materials may bring the advantages of cycle stability and specific capacity. In this work, we tried to disperse tin ions with organic skeleton to maximize the dispersion of active materials. Tin-based anode material based on polyethyleneimine‑sodium xanthogenate is synthesized by in-situ method at room temperature , and the thiocarboxyl group of polyethyleneimine‑sodium xanthogenate greatly increases the dispersion of metal ions . Carbon nanotubes (CNTs) are further introduced to improve the conductibility of tin-based materials owing to the existence of non-conductive organic groups. The anode material exhibits a long cycle life which delivers a specific capacity of 560 mAh g −1 after 1000 cycles. By analyzing the differential charge capacity (dQ/dV) curves, we find that the conversion reaction of tin-based materials is highly reversible.
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