An in-situ polymerization strategy for gel polymer electrolyte Si||Ni-rich lithium-ion batteries

Abstract

Coupling the Si-based anodes with nickel-rich LiNi_xMn_yCo_1−x−yO₂ cathodes (x ≥ 0.8) in the energy-dense cell prototype suffers from the mechanical instability of the Li-Si alloys, cathode collapse upon the high-voltage cycling, as well as the severe leakage current at elevated temperatures. More seriously, the cathode-to-anode cross-talk effect of transitional metal aggravates the depletion of the active Li reservoir. To reconcile the cation utilization degree, stress dissipation, and extreme temperature tolerance of the Si-based anode||NMC prototype, we propose a gel polymer electrolyte to reinforce the mechanical integrity of Si anode and chelate with the transitional cations towards the stabilized interfacial property. As coupling the conformal gel polymer electrolyte encapsulation with the spatial arranged Si anode and NMC811 cathode, the 2.7 Ah pouch-format cell could achieve the high energy density of 325.9 Wh kg⁻¹ (based on the whole pouch cell), 88.7% capacity retention for 2000 cycles, self-extinguish property as well as a wide temperature tolerance. Therefore, this proposed polymerization strategy provides a leap toward the secured Li batteries.

The cycling performance of Li-ion batteries based on silicon and Ni-rich oxide electrodes is limited by undesired phenomena including Si pulverization, cross talk, and interfacial instability. Here, the authors report in-situ polymerization to improve the stability of gel polymer Li-ion batteries.