Polyethylene separator: stretched and coated with porous nickel oxide nanoparticles for enhancement of its efficiency in Li-ion batteries

Sodium Super Ionic Conductor-Type Hybrid Electrolytes for High Performance Lithium Metal Batteries

Composite solid electrolytes (CSEs), composed of sodium superionic conductor (NASICON)-type Li_1+xAl_xTi_2-x(PO₄)₃ (LATP), poly (vinylidene fluoride-hexafluoro propylene) (PVDF-HFP), and lithium bis (trifluoromethanesulfonyl)imide (LiTFSI) salt, are designed and fabricated for lithium-metal batteries. The effects of the key design parameters (i.e., LiTFSI/LATP ratio, CSE thickness, and carbon content) on the specific capacity, coulombic efficiency, and cyclic stability were systematically investigated. The optimal CSE configuration, superior specific capacity (~160 mAh g^-1), low electrode polarization (~0.12 V), and remarkable cyclic stability (a capacity retention of 86.8%) were achieved during extended cycling (>200 cycles). In addition, with the optimal CSE structure, a high ionic conductivity (~2.83 × 10^-4 S cm^-1) was demonstrated at an ambient temperature. The CSE configuration demonstrated in this work can be employed for designing highly durable CSEs with enhanced ionic conductivity and significantly reduced interfacial electrolyte/electrode resistance.

Formation of Nanochannels Using Polypropylene and Acetylcellulose for Stable Separators

In this study, a polymer separator with enhanced thermal stability is prepared to solve the problem of thermal durability of lithium-ion battery separators. This separator is manufactured by coating a solution of acetyl cellulose and glycerin on polypropylene. The added glycerin reacts with the acetyl cellulose chains, helping the chains become flexible, and promotes the formation of many pores in the acetyl cellulose. To improve the thermal stability of the separator, a mixed solution of acetyl cellulose and glycerin was coated twice on the PP membrane film. Water pressure is applied using a water treatment equipment to partially connect the pores of a small size in each layer and for the interaction between the PP and acetyl cellulose. SEM is used to observe the shape, size, and quantity of pores. TGA and FT-IR are used to observe the interactions. Average water flux data of the separators is 1.42 LMH and the decomposition temperature increases by about 60 °C compared to the neat acetyl cellulose. It is confirmed that there is an interaction with PP between the functional groups of acetyl cellulose.

Preparation of Poly-1-butene Nanofiber Mat and Its Application as Shutdown Layer of Next Generation Lithium Ion Battery

Nonwoven nanofiber webs from polyolefin show great potential in various fields such as nanofilters, high performance membranes and separators in lithium ion batteries (LiB). Although nonwoven microfiber webs can be obtained by the well-established melt-blown method, it is relatively difficult to produce nonwoven nanofiber web using polyolefin (polyethylene and polypropylene). There have been several reports on the preparation of polyolefin nanofibers by melt-electrospinning, although this approach presents several intrinsic disadvantages, i.e., high processing costs, the requirement of complex equipment, and poor control over pore size or fiber diameter. Solution-based electrospinning has the potential to overcome the drawbacks of melt-electrospinning, but the solubility of most polyolefin is poor. In this study, we found that poly-1-butene, a member of the poly(alpha-olefin) family, can be used in the electrospinning process. We set the concentration of the polymeric solution for electrospinning at 0.65–1.7 g/mL. Here, we report on the fabrication of nonwoven fiber webs composed of poly-1-butene and their copolymers. The diameter of the nonwoven fiber mat was 0.2–0.4 μm, which can be applicable for shutdown layer. As a representative application, we prepared a poly-1-butene nanofiber separator with an appropriate pore size by electrospinning for use as the shut-down layer of a next-generation LiB. The PB-based nanofiber mat provided shutdown ability at around 100 to 120 °C.

Phase-Inversion Polymer Composite Separators Based on Hexagonal Boron Nitride Nanosheets for High-Temperature Lithium-Ion Batteries

By preventing electrical contact between anode and cathode electrodes while promoting ionic transport, separators are critical components in the safe operation of rechargeable battery technologies. However, traditional polymer-based separators have limited thermal stability, which has contributed to catastrophic thermal runaway failure modes that have conspicuously plagued lithium-ion batteries. Here, we describe the development of phase-inversion composite separators based on carbon-coated hexagonal boron nitride (hBN) nanosheets and poly(vinylidene fluoride) (PVDF) polymers that possess high porosity, electrolyte wettability, and thermal stability. The carbon-coated hBN nanosheets are obtained through a scalable liquid-phase shear exfoliation method using ethyl cellulose as a polymer stabilizer and source of the carbon coating following thermal pyrolysis. When incorporated within the PVDF matrix, the carbon-coated hBN nanosheets promote favorable interfacial interactions during the phase-inversion process, resulting in porous, flexible, free-standing composite separators. The unique chemical composition of these carbon-coated hBN separators implies high wettability for a wide range of liquid electrolytes. This combination of high porosity and electrolyte wettability enables enhanced ionic conductivity and lithium-ion battery electrochemical performance that exceeds incumbent polyolefin separators over a wide range of operating conditions. The hBN nanosheets also impart high thermal stability, providing safe lithium-ion battery operation up to 120 °C.

A Review on Inorganic Nanoparticles Modified Composite Membranes for Lithium-Ion Batteries: Recent Progress and Prospects

Separators with high porosity, mechanical robustness, high ion conductivity, thin structure, excellent thermal stability, high electrolyte uptake and high retention capacity is today's burning research topic. These characteristics are not easily achieved by using single polymer separators. Inorganic nanoparticle use is one of the efforts to achieve these attributes and it has taken its place in recent research. The inorganic nanoparticles not only improve the physical characteristics of the separator but also keep it from dendrite problems, which enhance its shelf life. In this article, use of inorganic particles for lithium-ion battery membrane modification is discussed in detail and composite membranes with three main types including inorganic particle-coated composite membranes, inorganic particle-filled composite membranes and inorganic particle-filled non-woven mates are described. The possible advantages of inorganic particles application on membrane morphology, different techniques and modification methods for improving particle performance in the composite membrane, future prospects and better applications of ceramic nanoparticles and improvements in these composite membranes are also highlighted. In short, the contents of this review provide a fruitful source for further study and the development of new lithium-ion battery membranes with improved mechanical stability, chemical inertness and better electrochemical properties.

Preparation of high performance lithium-ion batteries with a separator–cathode assembly

Comparison of the lithium-ion batteries with conventional separator (A) and separator–cathode assembly (B).