Water-Based Organic–Inorganic Hybrid Coating for a High-Performance Separator

Abstract

With the development of electric vehicles, the traditional polyolefin separators can not meet the increasing requirements of lithium ion batteries with high power density, high energy density, and high safety performance. Herein, a novel water-based binder is synthesized by grafting carboxyl groups onto cellulose diacetate. When the polyethylene (PE) separator is coated by this binder and SiO 2 nanoparticles, the thermal shrinkage of the modified separator is observed to be almost 0% after exposure at 200°C for 30 min. The puncture strength significantly increase from 5.10 MPa (PE separator) to 7.64 MPa. More importantly, the capacity retention of the cells assembled with modified separators after 100 cycles at 0.5 C increase from 73.3% (cells assembled with PE separator) to 81.6%, owing to the excellent electrolyte uptake and the good compatibility with lithium electrode. Besides, the modified separator shows excellent surface stability after 100 cycles. Considering the above excellent properties, this composite separator shows high potential to be used in lithium ion batteries with high power density and safety.

Tough and Flexible, Super Ion‐Conductive Electrolyte Membranes for Lithium‐Based Secondary Battery Applications

“…Owing to the good electrolyte affinity of SiO 2 combined with a water‐based cellulose diacetate (CDA) coating on the PE separator, the prepared SiO 2 /CDA@PE possesses a higher electrolyte wettability and uptake as well as Li + transport ability, as evidenced by an improved t Li + (from 0.33 in PE to 0.36) (code 1–7). [ 66 ] The same group of researchers also attached the SiO 2 /CDA composite to both sides of the PE surface via a dip‐coating process. [ 67 ] They found that the pore structure of the coating layer is regulated by the weight ratio of the SiO 2 precursor tetraethoxysilane (TEOS) to CDA in the coating solution (Figure 2d).…”

“…For example, a separator coated with heat‐resistant SiO 2 nanoparticles with the help of polymeric binders exhibits reduced thermal shrinkage regardless of the type of SiO 2 when exposed to the same conditions (code 2–1–2–3). [ 62,63,66 ] Wang and co‐workers [ 66 ] investigated separator impedance with increasing temperature for a more detailed analysis of the thermal behavior of SiO 2 ‐coated separators ( Figure a). They found that a bare PE separator breaks down at 175 °C, while a SiO 2 ‐coated PE can maintain mechanical integrity until 200 °C, indicating that the SiO 2 coating is beneficial for separators that may be subjected to the self‐protecting stage for longer periods of time.…”

“…Reproduced with permission. [ 66 ] Copyright 2016, American Chemical Society. b) Temperature‐dependent shrinkage curves of the bare PE and AlOOH/PVA@PE separators.…”

A SuperLEphilic/Superhydrophobic and Thermostable Separator Based on Silicone Nanofilaments for Li Metal Batteries

“…In contrast, surface grafting of functional groups and/or polymers could minimize the thickness increase and maintain the microporous structure (Yu et al., 2016). Although the modified polyolefin separators show improved wettability and thermostability, they are also hydrophilic (Chen et al., 2016, Dai et al., 2016, Ryou et al., 2011). Thus, moisture uptake is inevitable during the use and storage periods, which is unfavorable for the assembly and performance of Li batteries, especially for Li metal batteries.…”

Physicochemical Properties of Cellulose Separators for Lithium Ion Battery: Comparison with Celgard2325

“…The separator is a crucial component of LIBs. Its properties and structure play an indirect but key role in influencing the cell performance, including service life, energy density, power density, and safety [8,9]. Hence, several factors must be considered while choosing suitable separators for LIBs.…”