Effect of continuous pressures on electrochemical performance of Si anodes

The large volume change of nearly 300% during the lithiation and delithiation cycles of Si anodes leads to rapid capacity fading due to the continuous powder pulverization and the resulting loss of electrical contact. Under such conditions, the application of external pressure on the Si anodes is expected to relieve the aforementioned problem. Effects of continuous pressures within a range from 0 to 3.0 MPa on the electrochemical performance of Si anodes are investigated. It indicates that a pressure of approximately 0.6 MPa is suitable to reduce the interfacial resistance and improve the specific capacity, Coulombic efficiency, and cycle stability. With increasing pressure up to 1.0 MPa or 2.0 MPa, the specific capacity of Si anodes is further increased, whereas the notable overcharge and shortcircuit appear. This is attributed to the deficient electrolytes caused by the excessive pressures. The situation of which gets worse with the large volume variation of Si. The resulting increase of polarization leads to uneven deposition of lithium, forming dendrites initially locally and consequently thoroughly. The results here demonstrate that application of suitable continuous pressure on the Si anodes is a powerful tool to solve the problem of large volume variation.