N‐Containing Carbon‐Coated <i>β</i>‐Si<sub>3</sub>N<sub>4</sub> Enhances Si Anodes for High‐Performance Li‐Ion Batteries
Rahmandhika Firdauzha Hary Hernandha, B. Umesh, Purna Chandra Rath, Lê Thị Trang, Ju‐Chao Wei, Yu‐Chun Chuang, Ju Li, Jeng‐Kuei Chang
Abstract
Abstract The lithiation/delithiation properties of α ‐Si 3 N 4 and β ‐Si 3 N 4 are compared and the carbon coating effects are examined. Then, β ‐Si 3 N 4 at various fractions is used as the secondary phase in a Si anode to modify the electrode properties. The incorporated β ‐Si 3 N 4 decreases the crystal size of Si and introduces a new NSiO species at the β ‐Si 3 N 4 /Si interface. The nitrogen from the milled β ‐Si 3 N 4 diffuses into the surface carbon coating during the carbonization heat treatment, forming pyrrolic nitrogen and CNO species. The synergistic effects of combining β ‐Si 3 N 4 and Si phases on the specific capacity are confirmed. The operando X‐ray diffraction and X‐ray photoelectron spectroscopy data indicate that β ‐Si 3 N 4 is partially consumed during lithiation to form a favorable Li 3 N species at the electrode. However, the crystalline structure of the hexagonal β ‐Si 3 N 4 is preserved after prolonged cycling, which prevents electrode agglomeration and performance deterioration. The carbon‐coated β ‐Si 3 N 4 /Si composite anode shows specific capacities of 1068 and 480 mAh g −1 at 0.2 and 5 A g −1 , respectively. A full cell consisting of the carbon‐coated β ‐Si 3 N 4 /Si anode and a LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode is constructed and its properties are evaluated. The potential of the proposed composite anodes for Li‐ion battery applications is demonstrated.