Electrochemical evaluation of mixed oxide electrode for Li-ion secondary batteries: Li_(1.1)Mn_(1.9)O_4 and LiNi_(0.8)Co_(0.15)Al_(0.05)O_2

摘要

In attempt to utilize spinel compound, a blend type of positive electrode, Li_(1.1)Mn_(1.9)O_4 and LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 (1:1 in weight), was representatively investigated. Though spinel Li_(1.1)Mn_(1.9)O_4 is modified by Li replacement at Mn sites, its capacity fading was inevitable by HF attack into the electrolyte at 25 deg C and especially at 60 deg C. The specific discharge capacity of the mixed positive electrode, Li_(1.1)Mn_(1.9)O_4 and LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 (1:1 in weight), had a sum average value of Li_(1.1)Mn_(1.9)O_4 and LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 electrodes. Interestingly, the mixed positive electrode had greatly improved capacity retention even at 60 deg C. The capacity fading was only of about 8 mAh g~(-1) by applying 1 C rate (150mA g~(-1)) during 100 cycles. In the full cell test utilizing graphite as the negative electrode, the retained capacity was about 96 percent of its initial capacity by applying 1 C current at 25 deg C. It is suggested that the mixed electrode is considered to be a quite promising positive electrode material to be applied for lithium-ion batteries.