Self-Polymerized Dopamine Nanoparticles Modified Separators for Improving Electrochemical Performance and Enhancing Mechanical Strength of Lithium-Ion Batteries

Abstract

Separators in lithium-ion batteries (LIBs) play an important role for battery safety, so stable electrochemical performance and high mechanical strength of separators will always be of interest. On the basis of the fact that polydopamine (PDA) nanoparticles found in mussel have a strong adhesion ability, biomaterial surface nanoparticles modification methods are developed to increase electrochemical performance and enhance mechanical strength of polypropylene (PP) and polypropylene/polyethylene/polypropylene (PP/PE/PP) separators. The electrolyte uptake performance, ionic conductivities, discharging rate capabilities, yield stresses, and failure strains of PP and PP/PE/PP separators are all enhanced remarkably by PDA modification. Thermal shrinkage results show that thermal stabilities and the shrinkage percentage of PDA-modified separators are improved. The electrochemical testing results conclude that the discharging capacities of PP (increased by 3.77%~187.57%) and PP/PE/PP (increased by 2.31%~92.21%) separators increase remarkably from 0.1 C to 5.0 C. The ionic conductivities of PDA-modified PP and PP/PE/PP separators are 1.5 times and 6.1 times higher than that of unmodified PP and PP/PE/PP separators, which in turn increase the electrolyte uptake and ionic migration. In addition, mechanical properties of PP (yield stresses: 17.48%~100.11%; failure stresses: 13.45%~82.71%; failure strains: 4.08%~303.13%) and PP/PE/PP (yield stresses: 11.77%~296.00%; failure stresses: 12.50%~248.30%; failure strains: 16.53%~32.56%) separators are increased greatly.

Aramid Nanofibers Reinforced Cellulose Paper-Based Lithium-Ion Battery Separator with Improved Safety and Cycling Stability

“…Although PP membrane had a high tensile strength of 111 MPa along the machine direction (Fig. S3), its tensile strength at transverse direction was only recorded as 15 MPa, much lower than that of CF/ANF composite membranes due to the uniaxial stretching technology (Hao et al 2020). Besides, the introduction of ANFs also showed a reinforcing effect on Young's modulus of CF membrane, which was more advantageous relative to PP membrane (Fig.…”

Functional Separator Decorated with Polydopamine and Halloysite Nanotubes to Boost Li+ Transfer in Lithium Metal Batteries

“…PDA is an ideal polymeric binder because it can convert the entire hydrophobic polyethylene (PE) into hydrophilic, in contrast to other polymeric binders, which only change the surface characteristics of the separator, enhancing the lyophilicity of the PDA/HNTs/PE separator. [39][40][41][42] Furthermore, the PDA/HNTs/PE separator is expected to achieve a high Li + transference number because of the unique characteristics of HNTs. Because HNTs exhibit a three-dimensional structure composed of an inner octahedral layer of aluminum (À AlÀ OH, positively charged) and an external tetrahedral layer of silicon (À SiÀ OÀ Si, negatively charged), [43][44][45] two interactions between HNTs and electrolyte may occur in a PDA/HNTs/PE comprised system: 1) electrostatic attraction between the negatively-charged external layer of HNTs and Li + , and 2) dipole-dipole interaction between HNTs and electrolyte solvent in the Li + solvation structure, which induces facile Li + transfer through the separator, thereby achieving dendrite-free Li deposition.…”

“…As PDA/HNTs are introduced to the separator via a facile dip‐coating method, followed by the self‐polymerization of dopamine in an alkaline solution, complex treatment to introduce functional materials is not required. PDA is an ideal polymeric binder because it can convert the entire hydrophobic polyethylene (PE) into hydrophilic, in contrast to other polymeric binders, which only change the surface characteristics of the separator, enhancing the lyophilicity of the PDA/HNTs/PE separator [39–42] . Furthermore, the PDA/HNTs/PE separator is expected to achieve a high Li + transference number because of the unique characteristics of HNTs.…”

Mechanical Integrity of Conductive Carbon-Black-Filled Aqueous Polymer Binder in Composite Electrode for Lithium-Ion Battery

“…They are used as separators to separate positive and negative electrodes, and as adhesives for binding isolated active particles to the current collector [ 11 ]. For the former, microporous membranes based on semi-crystalline polyolefin materials such as polyethylene (PE), polypropylene (PP) and their blends are widely used in liquid electrolyte lithium-ion batteries [ 12 , 13 ]. As for all-solid-state batteries, with great efforts made by the scientific community, various poly(ethylene oxide) (PEO)-based solid polymer electrolytes obtained by crosslinking [ 14 , 15 , 16 ], blending [ 17 , 18 ] or grafting [ 19 ] have been applied.…”