A dual-functional gel-polymer electrolyte for lithium ion batteries with superior rate and safety performances

The ability to judiciously utilize gel-polymer electrolytes (GPEs) that replace liquid electrolytes is widely recognized as an attractive route to solving the safety concerns of Li-ion batteries (LIBs). In this context, novel LiNi_0.8Co_0.15Al_0.05O₂ (NCA)/graphite GPE and NCA/graphite-Si/C GPE batteries with high energy density and excellent electrochemical and safety performances are developed via in situ polymerization of pentaerythritol tetraacrylate (PETEA) in a liquid electrolyte. Notably, the capacity retention of NCA/graphite and NCA/graphite-Si/C GPE batteries after 200 cycles at the discharge rate of 5C is 92.5% and 81.2%, respectively, which are much larger than those implementing liquid electrolytes (i.e., only 55.9% and 51.4%, respectively). Interestingly, the GPE batteries also displayed considerably lower gas production, especially the graphite-Si/C anode battery, and did not undergo a violent combustion during the nail penetration test compared to the liquid electrolyte batteries. The markedly enhanced performances noted above can be attributed to the three-dimensional framework of the GPE which promoted the formation of a very tight protective film on the surface of the electrodes during cycling, thereby inhibiting the cyclable Li consumption and side reactions with the electrolyte. Furthermore, such a protective film effectively retained the structural integrity of the electrodes during the cycling process and reduced the heat reactions between the electrodes and electrolyte.