Ultrahigh Power Density and Safety Induced by Ultrathin Electrode Design and Bi-Salt Electrolyte Tailored Lithium Ion Batteries toward Durable 48 V Start/Stop Application

It is a bottleneck issue for state-of-the-art start/stop batteries used in commercialized electrical vehicles to have a long cycling life, high power output, and understanding safety performance. In this work, we fabricate prismatic cells to unravel how these tradeoffs can be balanced based on the material and cell design. Small-particle Li[Ni1/3Co1/3Mn1/3]O2 ternary materials with surface modification and isotropous graphite are respectively employed as cathode and anode to provide super power density. Ceramic-coated separators with high permeability and wide-temperature electrolytes with high conductivities enable the safety and cold cranking performance. Ultrathin-coating electrodes and whole poles are achieved to shorten the transferring distance of Li ions and promote the efficiency of Li intercalation and deintercalation kinetics, which demonstrates the lower internal resistance and current density. By unlocking charge transfer limitations, the cell presents a high discharge power density of >5000 W/kg at 25 °C, a 50% SOC (state of charge), and excellent cold cranking characteristics at −30 °C. A capacity retention of 3 C (100% depth of discharge, DoD) cycling approaches 80% over 6800 cycles at 25 °C and 4300 cycles at 45 °C. Also, a capacity retention of cycling at room temperature according to worldwide light vehicle test procedures reaches up to 92.3% over 6000 cycles with the energy throughput of 614.5 kWh and direct charge internal resistance does not soar with the cycling ongoing. The mechanism of the capacity loss is dissolved Ni, Co, and Mn, which results in irreversible loss of Li. The cell shows high safety characteristics by passing the 3 C overcharge and nail penetration tests. It is evident that the reported cell can be a promising commercialized candidate for 48 V start/stop and hybrid electric vehicle solutions.