Perfluoro Macrocyclic Ether as an Ambifunctional Additive for High-Performance SiO and Nickel 88%-Based High-Energy Li-ion Battery

State-of-the-art lithium (Li)-ion batteries employ silicon anode active material at a limited fraction while strongly relying on fluoroethylene carbonate (FEC) electrolyte additive exceeding 10 wt.% to enable stable cycling. The swelling issue of silicon in the aspect of solid electrolyte interphase (SEI) instability and a risk of safety hazards and high manufacturing cost due to FEC has motivated the authors to design a well-working fluorinated additive substitute. High-capacity cells employing nickel-rich oxide cathode are pursued by operating at > 4.2 V versus Li/Li+, for which anodic stability of electrolyte is required. Herein, a highly effective new ambifunctional additive of icosafluoro-15-crown 5-ether is proposed at a little fraction of 0.4 wt.% for the stabilized interfaces and reduced swelling of high capacity (3.5 mAh cm(-2)) 5 wt.% SiO-graphite anode and LiNi0.88Co0.08Mn0.04O2 cathode. Utilizing together with a lowered fraction of FEC, reversible long 300 cycles at 4.35 V and 1 C (225 mA g(-1)) are achieved. Material characterization results reveal that such stabilization is derived from the surface passivation of both anode and cathode with perfluoro ether, LiF, and LixPFy species. The present study gives insight into electrolyte formulation design with lower cost and both-side stabilization strategies for silicon and nickel-rich active materials and their interfaces.

Automated summary

The study proposes a new fluorinated additive, icosafluoro-15-crown 5-ether, which effectively reduces the swelling issue of the silicon anode in lithium-ion batteries, improves stability, and significantly reduces manufacturing cost. The additive also stabilizes the nickel-rich oxide cathode in high-capacity cells. When used together with a decreased fraction of FEC, reversible cycling for 300 cycles at high voltage and high rate was achieved. Material characterization results reveal that the stabilization is derived from the passivation of both anode and cathode surfaces.