Facile Deposition of the LiFePO4 Cathode by the Electrophoresis Method.

Lithium iron phosphate (LiFePO4, LFP) is one of the most advanced commercial cathode materials for Li-ion batteries and is widely applied as battery cells for electric vehicles. In this work, a thin and uniform LFP cathode film on a conductive carbon-coated aluminum foil was besieged by the electrophoretic deposition (EPD) technique. Along with the LFP deposition conditions, the impact of two types of binders, poly(vinylidene fluoride) (PVdF) and poly(vinylpyrrolidone) (PVP), on the film quality and electrochemical results has been studied. The results revealed that the LFP_PVP composite cathode had a highly stable electrochemical performance compared with the LFP_PVdF counterpart due to the negligible influence of the PVP on the pore volume and size and retaining high surface area of LFP. The LFP_PVP composite cathode film unveiled a high discharge capacity of 145 mAh g-1 at 0.1C and performed over 100 cycles with capacity retention and Coulombic efficiency of 95 and 99%, respectively. The C-rate capability test also revealed a more stable performance of LFP_PVP compared to LFP_PVdF.

Photo-crosslinked lignin/PAN electrospun separator for safe lithium-ion batteries.

A novel crosslinked electrospun nanofibrous membrane with maleated lignin (ML) and poly(acrylonitrile) (PAN) is presented as a separator for lithium-ion batteries (LIBs). Alkali lignin was treated with an esterification agent of maleic anhydride, resulting in a substantial hydroxyl group conversion to enhance the reactivity and mechanical properties of the final nanofiber membranes. The maleated lignin (ML) was subsequently mixed with UV-curable formulations (up to 30% wt) containing polyethylene glycol diacrylate (PEGDA), hydrolyzed 3-(Trimethoxysilyl)propyl methacrylate (HMEMO) as crosslinkers, and poly(acrylonitrile) (PAN) as a precursor polymer. UV-electrospinning was used to fabricate PAN/ML/HMEMO/PEGDA (PMHP) crosslinked membranes. PMHP membranes made of electrospun nanofibers feature a three-dimensional (3D) porous structure with interconnected voids between the fibers. The mechanical strength of PMHP membranes with a thickness of 25 µm was enhanced by the variation of the cross-linkable formulations. The cell assembled with PMHP2 membrane (20 wt% of ML) showed the maximum ionic conductivity value of 2.79*10-3 S cm-1, which is significantly higher than that of the same cell with the liquid electrolyte and commercial Celgard 2400 (6.5*10-4 S cm-1). The enhanced LIB efficiency with PMHP2 membrane can be attributed to its high porosity, which allows better electrolyte uptake and demonstrates higher ionic conductivity. As a result, the cell assembled with LiFePO4 cathode, Li metal anode, and PMHP2 membrane had a high initial discharge specific capacity of 147 mAh g-1 at 0.1 C and exhibited outstanding rate performance. Also, it effectively limits the formation of Li dendrites over 1000 h. PMHP separators have improved chemical and physical properties, including porosity, thermal, mechanical, and electrochemical characteristics, compared with the commercial ones.

Effect of a layer-by-layer assembled ultra-thin film on the solid electrolyte and Li interface.

Advanced all-solid-state batteries are considered as the most preferable power source for the next generation devices. Such batteries demand consumption of electrode materials with high energy and power density. One of the excellent solutions is the utilization of Li metal as anode which provides opportunity to fulfill such requirements. Yet, obstacles such as interfacial impedance and reactivity of Li metal with promising solid electrolytes prevent the consumption of the Li anode. Despite its outstanding stability under ambient conditions, high ionic conductivity and facile synthesis methods, NASICON-type Li1.3Al0.3Ti1.7(PO4)3 also suffers from the above mentioned problems. In this work, these critical issues were resolved by applying an artificial protective interlayer. Herein, the layer-by-layer polymer assembly approach of the ultra-thin interlayer of (PAA/PEO)30 on either side of solid electrolyte pellets simultaneously is presented. The introduction of the protective layer prevented a formation of mixed conduction interphase and effectively decreased the interfacial impedance. A symmetric cell with Li metal electrodes performed over 600 hours at 0.1 mA cm-2. Furthermore, an all-solid-state Li metal battery, assembled with the modified LATP solid electrolyte and LiFePO4 cathode, demonstrated an excellent electrochemical performance with an initial discharge capacity of 115 mA h g-1 and a capacity retention of 93% over 20 cycles with a coloumbic efficiency of almost 100%. The LATP with the (PAA/PEO)30 coating exhibited electrochemical stability up to 5 V.