Preparation and Capacity-Fading Investigation of Polymer-DerivedSilicon Carbonitride Anode for Lithium-Ion Battery

摘要

Polymer-derived silicon carbonitride (SiCN) materials have been synthesized via pyrolyzing from five poly(silylcarbondiimide)s with different contents of carbon (labeled as 1–5#). The morphological and structural measurements show that the SiCN materials are mixtures of nanocrystals of SiC, Si3N4, and graphite. The SiCN materials have been used as anodes for lithium-ion batteries. Among the five polymer-derived SiCN materials, 5#SiCN, derived from dichloromethylvinylsilane and di-n-octyldichlorosilane, has the best cycle stability and a high-rate performance at the low cutoff voltage of 0.01–1.0 V. In lithium-ion half-cells, the specific delithiation capacity of 5#SiCN anode still remains at 826.7 mA h g^–1 after 100 charge/discharge cycles; it can even deliver the capacity above 550 mA h g^–1 at high current densities of 1.6 and 2 A g^–1. In lithium-ion full cells, 5#SiCN anode works well with LiNi0.6Co0.2Mn0.2O2 commercial cathode. The outstanding electrochemical performance of 5#SiCN anode is attributed to two factors:(1) the formation of a stable and compact solid electrolyte interfacelayer on the anode surface anode, which protects the electrode fromcracking during the charge/discharge cycle; and (2) a large amountof carbon component and the less Si3N4 phasein the 5#SiCN structure, which provides an electrochemical reactiveand conductive environment in the SiCN structure, benefit the lithiation/delithiationprocess. In addition, we explore the reason for the capacity fadingof these SiCN anodes.