Identifying rate limitation and a guide to design of fast-charging Li-ion battery

Abstract

Fast-charging is highly demanded for applications requiring short charging time. However, fast-charging triggers serious problems, leading to decline in charge acceptance and energy efficiency, accelerated capacity degradation, and safety risk. In this work, a three-electrode coin cell with a Li metal reference electrode is designed to individually record the potential of two electrodes, and measure the impedance of each electrode by using a power-optimized graphite-LiNi0.80Co0.15Al0.05O2 electrode couple. It is shown that regardless of the state-of-charge the Li-ion cell's impedance is contributed predominantly by the cathode, and that the cathode's impedance is dominated by the charge-transfer resistance. In consistence with the impedance results, polarization of the Li-ion cell is dominated by the cathode. It is surprised to find that no Li plating occurs on the graphite anode even if the charging rate is increased to 10 C (1 C = 1.30 mA cm−2). The results of this work indicate that low overall impedance with a high cathode-to-anode impedance ratio is the key to enabling safe fast-charging, and that fast-charging Li-ion batteries without Li plating on the graphite anode is possible if the cathode and graphite anode are optimistically engineered. (Figure presented.).