Reciprocal irreversibility compensation of LiNi0.2Co0.2Al0.1Mn0.45O2 cathode and silicon oxide anode in new Li-ion battery

Abstract

A layered LiNi0.2Co0.2Al0.1Mn0.45O2 cathode is herein synthetized and investigated. Scanning electron microscopy (SEM) shows the layered morphology of the composite powder, while energy dispersive X-ray spectroscopy (EDS) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) confirm the achieved stoichiometry. X-ray diffraction (XRD) well identifies the layered structure unit cell, and Raman spectroscopy displays the corresponding M-O bonds motions. The cycling voltammetry (CV) of LiNi0.2Co0.2Al0.1Mn0.45O2 in lithium half-cell reveals an electrochemical process characterized by a remarkable irreversible oxidation taking place at 4.6 V vs. Li+/Li during the first scan, and subsequent reversible Li (de)intercalation centered at 3.8 V vs. Li+/Li with interphase resistance limited to 16 Ω upon activation as indicated by electrochemical impedance spectroscopy (EIS). The relevant irreversibility during first charge is also detected by galvanostatic cycling in a lithium half-cell subsequently operating at an average voltage of 3.8 V with a stable trend, and a maximum specific capacity of 130 mAh g−1. The initial irreversible capacity of the layered cathode is advantageously exploited for compensating the pristine inefficiency of the Li-alloying composite anode in a proof-of-concept Li-ion battery achieved by combining the LiNi0.2Co0.2Al0.1Mn0.45O2 with a silicon oxide composite (SiOx-C) without any preliminary pre-treatment of the electrodes. The full-cell displays a cycling behavior strongly influenced by the anode/cathode ratio, and the corresponding EIS performed both on the single electrodes and on the Li-ion cell by using an additional lithium reference suggests a controlling role of the anode interphase and possible enhancements through a slight excess of cathode material.