Abstract
The development of highly porous and thin separator is a great challenge for lithium-ion batteries (LIBs). However, the inevitable safety issues always caused by poor mechanical integrity and internal short circuits of the thin separator must be addressed before this type of separator can be applied to lithium-ion batteries. Here, we developed a novel multilayer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane with a highly porous and lamellar structure, through a combination of evaporation-induced phase separation and selective solvent etching methods. The developed membrane is capable of a greater amount of electrolyte uptake and excellent electrolyte retention resulting from its superior electrolyte wettability and highly porous structure, thereby offering better electrochemical performance compared to that of a commercial polyolefin separator (Celgard). Moreover, benefiting from the layered configuration, the tensile strength of the membrane can reach 13.5 MPa, which is close to the mechanical strength of the Celgard type along the transversal direction. The elaborate design of the multilayered structure allows the fabrication of a new class of thin separators with significant improvements in the mechanical and electrochemical performance. Given safer operation, the developed multilayer membrane may become a preferable separator required for high-power and high-energy storage devices.
Highlights
The development of porous polymer membranes has attracted remarkable attention in such fields as separation, energy storage, and crystallization [1,2,3]
Abundant functional polar groups appearing on nanomaterials may not be electrochemically stable against the strong oxidizing and reducing environments posed by the active electrodes under charge/discharge cycles, which can interfere with the functions of the battery
To overcome the disadvantage mentioned above, we developed a unique layered configuration which offers a variety of potential benefits with which to address issues related to the mechanical integrity and electrochemical stability of gel polymer electrolytes made with a thin separator
Summary
The development of porous polymer membranes has attracted remarkable attention in such fields as separation, energy storage, and crystallization [1,2,3]. This type of nonwoven mat can provide good mechanical strength and useful thermal shutdown properties, it causes an increment in the thickness and a reduction in the porosity of the composite separator [11,12] These disadvantages limit the electrochemical performance and life cycle of high-power LIBs. in some cases, prior to use nonwoven materials in producing a composite separator, additional prerequisite complex steps are required leading to an increase in production cost [11]. Membranes 2021, 11, 41 while introducing a high probability of puncture formation during the cell assembly These issues lead to unreliable operation of LIBs. the development of a new highly porous multilayer separator with superior mechanical and structural integrity is a major challenge. The obtained results provide an efficient and reliable approach for the construction of high-power and high-energy storage devices
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