Silicon (Si) faces big challenges in serious volume changes for applications in spite of its high theoretical capacity. Herein, a novel and facile method was proposed to decrease the volume change by simultaneously in situ absorbing the generated heat of only Si using a negative thermal expansion (NTE) material of ZrW 2 O 8 . The Si modified with 2 wt % of ZrW 2 O 8 exhibits excellent structural integrity, electrochemical performance, and safety under various conditions, especially at elevated temperatures. Its reversible capacities can remain 1187.2 mA h g −1 after 50 cycles and 643.8 mA h g −1 after 100 cycles at 2 A g −1 (∼199 and ∼190% higher than that of Si, respectively) at 25 °C. In addition, 930.6 mA h g −1 is maintained after 50 cycles at 60 °C (∼219% higher than that of Si). As current densities increase to 2 and 4 A g −1 , the values still remain 1389.4 and 757.5 mA h g −1 , respectively, much higher than that of Si. Furthermore, the strain of Si is reduced by 37.2% using ZrW 2 O 8 at 60 °C. Various products were analyzed, and the possible enhanced mechanism was discussed using multiple techniques. These findings exhibit significant potential for the improvement of energy materials using NTE materials by combining thermal effects and volume changes as well as the improved interface behavior.

Heat and deformation are responsible for poor performance and safety of batteries, but they cannot always be avoided. To address these two issues, ZrW 2 O 8 , a negative thermal expansion (NTE) material, was adopted to modify LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) to decline deformation via in situ absorption of the generated heat. The reversible capacity of NCM811 modified with 5 wt % of ZrW 2 O 8 can remain at 180.6 mAh/g after 100 cycles at 60 °C and 1.0 C current rate, which increases the retention ratio of NCM811 by 14.8%, while the voltage difference between main redox peaks, R ct , strain after cycles, and heat from DSC of NCM811 are reduced about 47.8%, 81.0%, 28.2%, and 76.0%, respectively. According to various analysis results, the side reactions are also suppressed, and the enhancing mechanisms of ZrW 2 O 8 for NCM811 were discussed. A general strategy is developed for the management of deformation using heat to improve performance and safety of batteries.

No abstract

No abstract

Metal-air batteries are promising for the next-generation energy storage because of attractive energy density, but they also face great challenges for applications. To intensify transfer and increase reaction active sites as well as decrease polarization, binder-free flexible three-dimensional porous oxygen electrodes were prepared by in situ deposition and decomposition of ZIF-67 on graphite foam (GF). Compared with GF, the modified sample has a much more stable discharge platform, lower charge/discharge polarization, higher reversibility, and higher reaction activity during oxygen reduction reaction and oxygen evolution reaction processes. The current densities of the reduction peak and oxidation peak of the pristine GF can be improved by a ZIF-67 derivative about 794 and 1367%, respectively. After 100 cycles at 0.1 mA·cm–2, the R ct of GF is decreased about 52% by the ZIF-67 derivative. The work paves a promising strategy for oxygen electrodes by combining absorption and electrocatalysis.