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In this study, we present improved power characteristics and suppressed phase transition by incorporating elemental doping into a P2-type cathode of sodium ion batteries. A Cu-doped Fe–Mn based P2-type Na0.67Cu0.125Fe0.375Mn0.5O2 cathode was designed based on the calculations of the electronic structure and then examined experimentally. Using first principles, we introduced instrinsic p-type conductivity by elemental doping with Cu. Introduction of Cu generated electron holes above the Fermi level in the electronic structure, which is typical of p-type semiconductors. Charge analyses suggested that the hole generation was driven primarily by the greater reduced characteristics of Cu as compared with those of Fe and Mn. In addition, introduction of Cu retaining high reduced property also suppressed phase transition from the P2 to Z phase by Fe migration to empty Na layers mainly. Electrochemical experiments revealed improved power characteristics upon the introduction of p-type conductivity. This could be attributed to the increase in the electronic conductivity by hole generation in the valence band. This study suggests that the introduction of p-type conductivity could be a rational tactic for the development of promising cathode materials for high performance sodium ion batteries.

In this study, we present improved power characteristics and suppressed phase transition by incorporating elemental doping into a P2-type cathode of sodium ion batteries. A Cu-doped Fe-Mn based P2-type Na0.67Cu0.125Fe0.375Mn0.5O2 cathode was designed based on the calculations of the electronic structure and then examined experimentally. Using first principles, we introduced instrinsic p-type conductivity by elemental doping with Cu. Introduction of Cu generated electron holes above the Fermi level in the electronic structure, which is typical of p-type semiconductors. Charge analyses suggested that the hole generation was driven primarily by the greater reduced characteristics of Cu as compared with those of Fe and Mn. In addition, introduction of Cu retaining high reduced property also suppressed phase transition from the P2 to Z phase by Fe migration to empty Na layers mainly. Electrochemical experiments revealed improved power characteristics upon the introduction of p-type conductivity. This could be attributed to the increase in the electronic conductivity by hole generation in the valence band. This study suggests that the introduction of p-type conductivity could be a rational tactic for the development of promising cathode materials for high performance sodium ion batteries.

Recently, the substitution of inactive elements has been reported as a promising strategy for improving the structural stability and electrochemical performance of layered cathode materials for sodium-ion batteries (SIBs). In this regard, we investigated the positive effects of inactive Ti substitution into O3-type NaFe0.25Ni0.25Mn0.5O2 based on first-principles calculations and electrochemical experiments. After Ti substitution, Na[Ti0.03(Fe0.25Ni0.25Mn0.5)0.97]O2 exhibits improved capacity retention and rate capability compared with Ti-free NaFe0.25Ni0.25Mn0.5O2. Such an improvement is primarily attributed to the enhanced structural stability and lowered activation energy for Na+ migration, which is induced by Ti substitution in the host structure. Based on first-principles calculations of the average net charges and partial densities of states, we suggest that Ti substitution effectively enhances the binding between transition metals and oxygen by increasing the oxygen electron density, which in turn lowers the energy barrier of Na+ migration, leading to a notable enhancement in the rate capability of Na[Ti0.03(Fe0.25Ni0.25Mn0.5)0.97]O2. Compared with other inactive elements (e.g., Al and Mg), Ti is a more suitable substituent for improving the electrochemical properties of layered cathode materials because of its large total charge variation contributing to capacity. The results of this study provide practical guidelines for developing highly reliable layered cathode materials for SIBs.

The power characteristics of lithium-ion batteries (LIBs) are crucial for the advent of commercialized, high-power applications, such as electric vehicles. Through both first-principles multiscale simulations and experiments, here, we present fundamental understanding on the power characteristics of the high-voltage spinel cathode correlated with its elastic softness and phase transformation in nanodomains for high-power LIBs. Atomic models of LiNi0.5Mn1.5O4 and LiNi0.5Mn1.5−xTixO4 are developed for multiscale phase field modeling based on structural information for the as-prepared nanopowders. The combined computational and experimental investigations suggest that the thermodynamic phase stability of LiNi0.5Mn1.5O4 can be effectively enhanced by the incorporation of Ti into the structure without any change to the redox mechanism. Ti incorporation provides a faster ionic mobility and the improved phase stability because of the reinforced Ti4+–O bonds. Based on the multiscale phase transformation kinetics, LiNi0.5Mn1.5−xTixO4 exhibits an enhanced elastic softness and slower phase separation than LiNi0.5Mn1.5O4 in the nanodomain during Li+ insertion and extraction. Such characteristics are mainly responsible for the improved electrochemical performance at higher current rates, as confirmed by electrochemical experiments. This fundamental understanding of the power characteristics with respect to the correlations with elastic softness and phase transformation will provide a guideline to develop and design advanced materials for high-power LIBs.

In lithium-ion batteries (LIBs) comprising spinel cathode materials, the dissolution of transition metals (TMs) in the cathodes causes severe cyclic degradation. We investigate the origin and mechanism of surface TM dissolution in high-voltage spinel oxide (LiNi0.5Mn1.5O4) nanoparticles to find a practical method for its mitigation. Atomic structures of the LiNi0.5Mn1.5O4 surfaces are developed, and the electronic structures are investigated by first-principles calculations. The results indicate that titanium is a promising dopant for forming a more stable surface structure by reinforcing metal–oxygen bonds in LiNi0.5Mn1.5O4. Experimentally synthesized LiNi0.5Mn1.5O4 with titanium surface doping exhibits improved electrochemical performance by suppressing undesirable TM dissolution during cycles. The theoretical prediction and experimental validation presented here suggest a viable method to suppress TM dissolution in LiNi0.5Mn1.5O4.

We have prepared a high-density polyaniline (PANI) paste (50 mg/mL), with similar physical properties to those of paints or pigments. The synthesis of PANI is confirmed by Fourier transform infrared (FT-IR) spectroscopy. The morphologies of PANI, doped PANI, and doped PANI paste are confirmed by scanning electron microscopy (SEM). Particles of doped PANI paste are approximately 40-50 nm in diameter, with a uniform and cubic shape. The electrochemical performances of doped PANI paste using both liquid and solid polymer electrolytes have been measured by galvanostatic charge and discharge process. The cell fabricated with doped PANI paste and the solid polymer electrolyte exhibits a discharge capacity of ~87 µAh/cm2 (64.0 mAh/g) at the second cycle and ~67 µAh/cm2 (50.1 mAh/g) at the 100th cycle.

Surface modified Li 3 V 2 (PO 4 ) 3 /C materials have been prepared by coating with AlF 3 and Al 2 O 3 via a conventional precipitation method. X-ray diffraction patterns indicate that the surface modification does not affect to the bulk structure of Li 3 V 2 (PO 4 ) 3 . Field emission scanning electron microscopy and field emission transmission electron microscopy show that an amorphous carbon layer and particles of AlF 3 and Al 2 O 3 are coated on the surface of Li 3 V 2 (PO 4 ) 3 particles. Both AlF 3 - and Al 2 O 3 -coated materials exhibit better cycling performance than the uncoated Li 3 V 2 (PO 4 ) 3 /C between 3.0 and 4.8 V. The capacity retention rates of LVP/C, LVP/C-AlF 3 , and LVP/C-Al 2 O 3 after 50 cycles at 0.2 C are 76.12, 85.39, and 84.99%, respectively.

Li 3-x Na x V 2-x Ti x (PO 4 ) 3 /C (x = 0, 0.01, 0.03, 0.05, and 0.07) have been prepared via a conventional sol–gel method. X-ray diffraction patterns indicate that Li 3-x Na x V 2-x Ti x (PO 4 ) 3 /C are successfully obtained with a monoclinic structure. X-ray photoelectron spectroscopy has been performed to investigate the valence states of the doped elements. The morphologies of Li 3-x Na x V 2-x Ti x (PO 4 ) 3 /C are investigated by field emission scanning electron microscopy. Li 2.97 Na 0.03 V 1.97 Ti 0.03 (PO 4 ) 3 /C exhibits the highest electrochemical properties among all the samples. It delivers an initial discharge capacity of 170.61 mAh g −1 and capacity retention of 72.66% after 100 cycles, while the uncoated Li 3 V 2 (PO 4 ) 3 /C only delivers an initial discharge capacity of 164.08 mAh g −1 and capacity retention of 71.59% in the voltage range of 3.0–4.8 V. In addition, the results of cyclic voltammetry and galvanostatic intermittent titration technique ensure that the ionic conductivity of Li 2.97 Na 0.03 V 1.97 Ti 0.03 (PO 4 ) 3 /C is increased compared with the uncoated Li 3 V 2 (PO 4 ) 3 /C.

Renewable biomass has attracted great attention for the production of biooil, biogas, and biochar, a carbon residual applicable for carbon sequestration and environmental remediation. Rice straw is one of the most common biomasses among agricultural wastes in South Korea. As part of our advanced and environmentally friendly research, we applied biochar derived from rice straw as the anode material for lithium-ion batteries (LIBs). Porous carbons with a high surface area were prepared from rice straw. Such porous carbons have exhibited particularly large reversible capacity and hence proven to be a candidate anode material for high-rate and high-capacity LIBs. Rice straw-derived biochars were synthesized at four different temperatures: 400, 550, 700, and 900 °C. The surface was modified by using HCl and H2O2 on the 550 °C biochar in order to increase the surface area. The resulting biochar was characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The surface area was measured by Brunauer-Emmett-Teller (BET) method. The electrochemical characterizations were investigated by galvanostatic charge-discharge (CD) curves, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). All samples exhibited reversible capacities of below 200 mAh g(-1). The surface-modified biochars exhibited improved cycle performance. Surface modification using HCl showed better cycle performance than H2O2. However, the capacities of the treated 550 °C biochar were similar to those of non-surface-modified biochar.

Li4Ti5O12/carbon (LTO/C) nanoparticles were synthesised by solution combustion method, and malic acid were used as carbon sources. The mixture of LTO pristine and carbon source was calcination sintered at low temperature (350°C). This temperature was relatively low temperature in comparison with previous sintering temperature (500–700°C). The physical characteristics of LTO/C nanoparticles were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and inductively coupled plasma spectroscopy. Their electrochemical performance was evaluated by electrochemical impedance spectroscopy, cyclic voltammograms, constant current charge–discharge and rate charge–discharge. As the results of the measurement, LTO/C-0·8 had discharge specific capacity of 71·1 mAh g−1 at high rate of 40C. The cycle performance of LTO/C-0·8 was excellent as 168·5 mAh g−1 (at ∼160 mA g−1) and 104·5 mAh g−1 (at ∼3200 mA g−1) after 50 cycles, and it keeps 98·9 and 96·0% of capacity at the second c...

Rice derived carbon coated silica powder with various silica/rice weight ratios was prepared by drying and then pyrolysing the co-milled slurry mixture thereof and incorporated into the anode as active material for lithium ion batteries. The crystallinity of the composites was characterized by X-ray diffraction analysis. Coin type cells (2032) were manufactured and galvanostatically tested, including charge-discharge characteristics, cyclic voltammograms and electrochemical impedance spectra. The composite anode with rice/silica ratio of 1:1 delivers a better initial discharge capacity, Coulombic efficiency and 10th-cycle capacity retention of 454.2 mAhg-1, 48.5% and 35.1%, respectively, at the potential window of 0.02-2.5 V and constant current density of 50 mAg-1. Good reversible capacity as high as 207.9 mAhg-1 and cyclic stability were achieved for the rice-carbon anode with rice precursor annealed at 700 oC/3 h, followed by 900 oC/1.5 h in argon atmosphere as active material.

The electrochemical performance for the corrosion of zinc anodes according to particle size and shape as anode in Zn/air batteries was study. We prepared five samples of Zn powder with different particle size and morphology. For analysis the particle size of theme, we measured particle size analysis (PSA). As the result, sample (e) had smaller particle size with than others. For measuring the electrochemical performance of them, we measured the cyclic voltammetry and linear polarization in three electrode system (half-cell). For measuring the morphology change of them before and after cyclic voltammetry, we measured Field Emission Scanning Electron Microscope (FE-SEM). From the cyclic voltammetry, as the zinc powder had small size, we knew that it had large diffusion coefficient. From the linear polarization, as the zinc powder had small size, it was a good state with high polarization resistance as anode in Zn/air batteries. From the SEM images, the particle size had increased due to the dendrite formation after cyclic voltammetry. Therefore, the sample (e) with small size would have the best electrochemical performance between these samples.

In lithium-ion batteries (LIBs) comprising spinel cathode materials, the dissolution of transition metals (TMs) in the cathodes causes severe cyclic degradation. We investigate the origin and mechanism of surface TM dissolution in high-voltage spinel oxide (LiNi

In this study, iron oxides obtained from used disposable heating pads are used as an anode material in lithium ion batteries. Fe3O4 and Fe2O3 phases are identified using XRD. Additionally, the existence of other substances, such as carbon and NaCl, are determined using EDS dot mapping. Purified powder (PP) is prepared by washing the obtained powder (OP) with distilled water and ethanol. Heat-treated powder (HP) is prepared by heating PP at 600 °C. The electrochemical result shows that PP delivers a discharge capacity of ∼700 mAh g(-1) after 50 cycles. HP delivers a higher initial capacity of 1170 mAh g(-1); however, the discharge capacity decreases drastically to 500 mAh g(-1). These results were similar to those determined for commercial iron oxide in previous studies.

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