Mehran Javanbakht

In this study, a novel S-based compound, methyl p-toluene sulfonate (MPTS) has been investigated as film forming additive in Li/graphite cells. According to the density functional theory (DFT) investigation of electron affinity energy of MPTS and carbonate solvents, MPTS has more negative electron affinity energy of -2.17 eV, whilst it is only − 1.03 eV for ethylene carbonate (EC) and − 0.73 eV for dimethyl carbonate (DMC). It confirms the highest reductive activity of MPTS, which was consistent with the CV test result. The physicochemical features of the graphite electrode were studied using Fourier-transform infrared (FTIR) spectroscopy, field-emission scanning microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) analysis, transmission electron microscopy (TEM), The electrochemical tests results showed that the battery with 1.5% wt% MPTS exhibited a low impedance on the electrode interface and remarkable cyclability, maintaining 93.17% of its initial capacity at 0.2 C after 100 cycles, approximately 11% more than the conventional electrolyte. These outstanding performances are ascribed to the preferential absorption of MPTS and the as-created interface. TEM and XPS analysis confirmed that MPTS forms a thinner SEI layer containing sulfur on the graphite electrode, predicted by recommended mechanism via theoretical calculations. This protective sulfur-containing film promotes faster lithium intercalation/deintercalation kinetics via declining the charge transfer resistance.

A binder-free composite electrode of LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811)/multi-walled carbon nanotube (MWCNT) with an extremely high NMC811 mass ratio (91 wt%) is prepared using an electrophoretic deposition process in a quick time (∼3 min). The spherical NMC811 particles are homogenously incorporated in the network created by MWCNTs, with desirable contact between these two components of the composite. The NMC811/MWCNT composite electrode showed a high first discharge capacity of 1.89 mAh cm⁻² (163.4 mAh g⁻¹) and 1.67 mAh cm⁻² after 150 cycles at 0.1C with 88.3% capacity retention in the charge-discharge process. Compared with the conventional NMC811 electrodes prepared by the electrophoretic process (with carbon black and polyvinylidene fluoride) or doctor-blade strategy, superior electrochemical performance achieved in the binder-free composite NMC811/MWCNT electrode prepared by the electrophoretic process. This improvement is possible because the NMC811/MWCNT composite electrode could allow for a higher surface area and conductivity of the cathode material, a reactive interphase and adjustable available space in the electrode, and a homogenous distribution of the NMC particles in the MWCNT network. This scale-able, simple, binder and NMP-free, time-saving method with controllable growth deposit can be used to fabricate a variety of electrodes in storage systems.

In this work, a facile and accurate method is reported for the delocalization of negative charge on fluorinated polymers to obtain high-performance single-ion conducting polymer electrolytes (SICPs) based on brush copolymers with simultaneous high ionic conductivity and t _Li+ . The poly(styrene sulfonate) (PSSA) single ion-conducting moieties were grafted-from C–F linkages to the fluorinated polymer’s backbone via the atom transfer radical polymerization method. The chemical structure characterization of the synthesized brush copolymers via ¹ H-NMR and thermal gravimetric analyses (TGA) confirmed 25% grafting of PSSA to the poly(vinylidene fluoride) backbone. In continue, the pristine and single-ion fluorinated polymer membranes with bi-continuous honeycomb-like morphology structures were prepared via the vapor-induced phase inversion (VIPS) method. After immersing in a liquid electrolyte, the prepared SICP demonstrated promising ionic conductivity ( σ ), t _Li+ , and electrochemical stability of 1.9 × 10 ⁻³ Scm ⁻¹ , 0.82, and 5.2 V (vs Li ⁺ /Li), respectively. The assembled Li/SICP/LiMn ₂ O ₄  half-cells revealed an improved discharge capacity of 168 mA hg ⁻¹ at 0.1C. The charge-discharge studies revealed that the ohmic-resistance and polarization resistance of fluorinated polymer electrolytes could be decreased by the effect of PSSA-grafted moieties. The results of this work confirmed the promising capability of these new SICPs for high-safety LIBs.