Enhanced Electrochemical Performance and Safety of Silicon by a Negative Thermal Expansion Material of ZrW₂O₈

Abstract

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.

Decreased Deformation and Heat as well as Improved Interface and Diffusion of Silicon To Enhance Electrochemical Performance and Safety by a Negative Thermal Expansion Material

“…There are two absorption peaks at 3440 and 1630 cm –1 in all curves, corresponding to −OH, mainly due to the presence of moisture in the sample or test environment using the KBr tablet method . There are three peaks at 1233, 1088, and 805 cm –1 in the curve of Si, which correspond to the Si–O–Si. , In the FT-IR curve of LTP, the peak observed at 1036 cm –1 belongs to the PO 4 3– stretching vibration, and the peak at 1237 cm –1 is attributed to the stretch vibration of O–P–O. The peaks at 650 and 580 cm –1 are ascribed to the Ti–O–P bond and the P–O–P bond, respectively.…”

“…The XPS full spectrum of SL3 before cycling in Figure a shows that the characteristic peaks of Si 2p, Si 2s, O 1s, and C 1s exist in the SL3 sample, and Ti 2p and P 2p can be detected from partial enlargement in Figure b,c, indicating the existence of Si and LTP in the SL3 sample. From the high-resolution spectra of Si 2p in Figure d, two peaks with binding energies of 103.1 and 99 eV are detected, corresponding to Si–O and Si–Si bonds on the surface of Si, respectively . From the high-resolution spectrum of Ti 2p in Figure e, Ti 2p consists of the Ti 2p 1/2 peak at 465.6 eV and the Ti 2p 3/2 peak at 460.5 eV, signals of Ti 4+ , referring to Ti-O bonds .…”

“…Contrary to general materials that expand on heating, negative thermal expansion (NTE) materials have attracted considerable attention because of their abnormal thermal shrinkage behavior. , NTE materials can greatly improve the electrochemical performance of different battery materials such as LiNi 0.8 Co 0.1 Mn 0.1 O 2, LiNi 0.6 Co 0.2 Mn 0.2 O 2, LiNi 0.88 Co 0.1 Al 0.02 O 2, and Si . However, the cost of the reported NTE materials is high besides the complex synthesis process, which is not beneficial for applications.…”

“…30,31 NTE materials can greatly improve the electrochemical performance of different battery materials such as LiNi 0.8 Co 0.1 Mn 0.1 O 2, 32 LiNi 0.6 Co 0.2 Mn 0.2 O 2, 33 Li-Ni 0.88 Co 0.1 Al 0.02 O 2, 34 and Si. 35 However, the cost of the reported NTE materials is high besides the complex synthesis process, which is not beneficial for applications. Thus, other low-cost and simply synthesized NTE materials need to be explored to improve the electrochemical performance of battery materials.…”

Low-Temperature Rapid Sintering of Dense Cubic Phase ZrW2−xMoxO8 Ceramics by Spark Plasma Sintering and Evaluation of Its Thermal Properties

“…Cubic phase ZrW 2−x Mo x O 8 (cubic-ZrW 2−x Mo x O 8 ) is a well-known substitutional solid solution material with unique negative thermal expansion (NTE) properties. It has been extensively considered for use in some applications such as precision mechanical engineering and optics that require precisely controllable thermal expansion [1][2][3][4][5][6][7][8][9]. Although some compounds (e.g., ice [10], SiO 2 [11], PbTiO 3 [12]) are known to exhibit anisotropic NTE over a limited temperature range.…”