An integrated separator/anode assembly based on electrospinning technique for advanced lithium-ion batteries

Study on the lignin-derived sp2-sp3 hybrid hard carbon materials and the feasibility for industrial production

Hard carbon has been widely used in anode of lithium/sodium ion battery, electrode of supercapacitor, and carbon molecular sieve for CO2 capture and hydrogen storage. In this study the lignin derived hard carbon products are investigated, and the conclusions are abstracted as follows. (1) The lignin derived hard carbon products consist of microcrystal units of sp2 graphene fragments, jointed by sp3 carbon atoms and forming sp2-sp3 hybrid hard carbon family. (2) From the lignin precursors to the sp2-sp3 hybrid hard carbon products, most carbon atoms retain their original electron configurations (sp2 or sp3) and keep their composition in lignin. (3) The architectures of lignin-derived hard carbon materials are closely dependent on the forms of their lignin precursors, and could be preformed by different pretreatment techniques. (4) The carbonization of lignin precursors follows the mechanism "carbonization in situ and recombination nearby". (5) Due to the high carbon ratio and abundant active functional groups in lignin, new activation techniques could be developed for control of pore size and pore volume. In general lignin is an excellent raw material for sp2-sp3 hybrid hard carbon products, a green and sustainable alternative resource for phenolic resin, and industrial production for lignin derived hard carbon products would be feasible.

Manipulating the Nanophase Separation of a Polymer-Salt Microfluid Generates an Advanced In Situ Separator for Component-Integrated Energy Storage Devices

A polymer separator plays a pivotal role in battery safety, overall electrochemical performance, and cell assembly process. Traditional separators are separately produced from the electrodes and dominated by porous polyolefin thin films. In spite of their commercial success, today's separators are facing growing challenges with the increasing demand on the device safety and performance. As an attempt to address this urgent need, here, we propose a concept of in situ separator technology by manipulating the two-dimensional (2D) microfluid nanophase separation (2D-MFPS) of a poly(vinylidene difluoride)/lithium salt solution during drying. Particularly, nanophase separation is effectively regulated by low humidity, salt type, and compositions. For application studies, this 2D-MFPS is directly performed onto commercial electrodes under drying conditions with low humidity to fabricate a high-performance in situ separator with thickness and porous structures comparable to those of commercial Celgard separators. This in situ separator shows superior performance in high-temperature stability and wetting capability to a variety of liquid electrolytes. Finally, pouch cells with this in situ separator technology are successfully assembled with an extremely simplified separator-stacking-free process and demonstrate stable cycle performance due to the well-controlled porous structures and electrode-separator interface.

Solution plasma synthesis of bacterial cellulose acetate derived from nata de coco waste incorporated with polyether block amide

Cellulose acetate (CA), one of the most important cellulose derivatives, is used in various applications especially in membranes, films, fibers, filters, and polymers. Because of the tough and flexible character and resistance to acids of CA, bacterial cellulose acetate (BCA) has been used as reinforcement for high performance separator purposes. In this study, BCA was synthesized through the heterogeneous acetylation in acetic solution with H₂SO₄ as catalyst by solution plasma process (SPP) of bacterial cellulose (BC) extracted form nata de coco waste. The SPP was considered as mild, simple, and fast method for many kinds of synthesis. The solution plasma time was studied to obtain considerably high DS values (in this work, DS = 1.95). The high DS values are an important feature when considering an environmental factor, good liquid transport and excellent absorption. Furthermore, the BCA incorporated with poly ether block amide by electrospinning method is successfully fabricated as nanofibrous membranes. The proposed PEBAX/BCA nanofibrous membranes display superior sufficient porosity (74.7%), exceptional liquid electrolyte uptake (364.6%), sufficient thermal dimensional stability at 150 °C, great electrochemical stability (discharge capacity at 0.2C = 102.14 mAh g^-1), and high ionic conductivity (9.12 × 10^-3 S/cm). Furthermore, the PEBAX/BCA nanofibrous membranes can be used as high-performance separators enhancing its safety for Li-ion battery applications.