As
the classic cathode material, lithium cobalt oxide (LiCoO2, LCO) suffers from severe structural and interfacial degradation
at voltage >4.5 V, which induces fast capacity decay of the cells.
Herein, we adopt a simple and effective method, doping aluminum (Al)
cations in precursors, to improve the structural stability of LCO
and systematically investigate the effect of Al doping on the electrochemical
performances. Doping in precursors rather than bulk particles is beneficial
to realize uniform Al ions distribution. Even at 4.5 V charging voltage,
the LCO/graphite pouch cells with high Al doping levels (8500 ppm)
deliver initial and reversible discharge capacities of 386 and 369
mAh after 500 cycles, respectively. The capacity retention is as high
as 95.5%. When the cutoff voltage reaches 4.55 V, the pouch cell maintains
79.0% of the first-cycle discharge capacity after 500 cycles. With
optimized electrolyte, the pouch cell realizes 87.3% of the initial
discharge capacity after 500 cycles at 45 °C. Moreover, the thermal
safety performance of the pouch cells with Al doping is promising.
Our work displays an excellent inspiration for developing high-voltage,
long-cycle, and safe LCO cathode for commercial lithium-ion batteries.