The raw material selected for this research was Brazil chestnut shells (BCs), which were utilized to gain porous carbon as a positive electrode for lithium–sulfur batteries (LSBs). The effects of N/S co-doped on the electrochemical properties of porous carbon materials were studied using thiourea as nitrogen and sulfur sources. The experimental results indicate that the N/S co-doped carbon materials have a higher mesopore ratio than the undoped porous carbon materials. The porous carbon material NSPC-2 has a lotus-like structure with uniform pore distribution. The N and S doping contents are 2.5% and 5.4%. The prepared N/S co-doped porous carbon materials were combined with S, respectively, and three kinds of sulfur carbon composites were obtained. Among them, the composite NSPC-2/S can achieve the initial specific discharge capacity of 1018.6 mAh g− 1 at 0.2 C rate. At 1 C rate, the initial discharge capacity of the material is 730.6 mAh g− 1, and the coulomb efficiency is 98.6% and the capacity retention rate is 71.5% after 400 charge–discharge cycles.

In response to the growing demand for high-performance lithium-ion batteries, this study investigates the crucial role of different carbon sources in enhancing the electrochemical performance of lithium iron phosphate ( LiFePO4) cathode materials. Lithium iron phosphate ( LiFePO4) suffers from drawbacks, such as low electronic conductivity and low lithium-ion diffusion coefficient, which hinder its industrial development. Carbon is a common surface coating material for LiFePO4, and the source, coating method, coating amount, and incorporation method of carbon have a significant impact on the performance of LiFePO4 materials. In this work, iron phosphate was used as the iron and phosphorus source, and lithium carbonate was used as the lithium source. Glucose, phenolic resin, ascorbic acid, and starch were employed as carbon sources. Ethanol was utilized as a dispersing agent, and ball milling was employed to obtain the LiFePO4 precursor. Carbon-coated LiFePO4 cathode materials were synthesized using the carbothermal reduction method, and the effects of different carbon sources on the structure and electrochemical performance of LiFePO4 materials were systematically investigated. The results showed that, compared to other carbon sources, LiFePO4 prepared with glucose as the carbon source not only had a higher discharge specific capacity but also better rate cycle performance. Within a voltage range of 2.5–4.2 V, the initial discharge specific capacities at 0.1, 0.5, and 1 C rates were 154.6, 145.6, and 137.6 mAh/g, respectively. After 20 cycles at a 1 C rate, the capacity retention rate was 98.7%, demonstrating excellent electrochemical performance.

The complexation of silicon with carbon materials is considered an effective method for using silicon as an anode material for lithium-ion batteries. In the present study, carbon frameworks with a 3D porous structure were fabricated using metal–organic frameworks (MOFs), which have been drawing significant attention as a promising material in a wide range of applications. Subsequently, the fabricated carbon frameworks were subjected to CVD to obtain silicon-carbon complexes. These siliconcarbon complexes with a 3D porous structure exhibited excellent rate capability because they provided sufficient paths for Li-ion diffusion while facilitating contact with the electrolyte. In addition, unoccupied space within the silicon complex, combined with the stable structure of the carbon framework, allowed the volume expansion of silicon and the resultant stress to be more effectively accommodated, thereby reducing electrode expansion. The major findings of the present study demonstrate the applicability of MOF-based carbon frameworks as a material for silicon complex anodes.

The high level of lithium storage in synthetic porous carbons has necessitated the development of accurate models for estimating the specific capacity of carbon-based lithium-ion battery (LIB) anodes. To date, various models have been developed to estimate the storage capacity of lithium in carbonaceous materials. However, these models are complex and do not take into account the effect of porosity in their estimations. In this paper, a novel model is proposed to predict the specific capacity of porous carbon LIB anodes. For this purpose, a new factor is introduced, which is called normalized surface area. Considering this factor, the contribution of surface lithium storage can be added to the lithium stored in the bulk to have a better prediction. The novel model proposed in this study is able to estimate the lithium storage capacity of LIB anodes based on the porosity of porous carbons for the first time. Benefiting porosity value (specific surface area) makes the predictions quick, facile, and sensible for the scientists and experts designing LIBs using porous carbon anodes. The predicted capacities were compared with that of the literature reported by experimental works. The remarkable consistency of the measured and predicted capacities of the LIB anodes also confirms the validity of the approach and its reliability for further predictions.

In this study, soybean oil, which is used in a large variety of processed foods, is used as a carbon source. Soybean oil is successfully coated onto the surface of LiNi1/ 3Co1/3Mn1/3O2 (NCM) by a simple method. The physical and electrochemical properties of NCM/C hybrid materials are determined. As a result, a 5 nm thickness carbon coating layer is formed on the surface of the NCM, resulting in improved capability and cyclic performance in the battery. The NCM/C battery shows an initial discharge capacity of 159 mAh g−1 and 95% capacity retention after 100 cycles (a discharge capacity of 120 mAh g−1 and 94% retention are observed after 100 cycles for the NCM cathode).

We reported the synthesis of dendrite-like carbon nanotube-confined polymeric sulfur composite by modifying the surface of carbon nanotubes (CNTs) with trithiocyanuric acid (TTCA) and then copolymerizing with sulfur. DSC results show the successfully formation of robust chemical bonds between sulfur and TTCA modified CNTs, which effectively avoid the dissolution of polysulfide when used as cathodes for lithium–sulfur batteries. The composite with a high sulfur content of 78 wt% exhibits an initial charge capacity of 698 mAh g− 1 and the residual capacity of 553 mAh g− 1 after 1000 cycles at a rate of 1 C.

We fabricated a Li-S battery with post-treated carbon nanotube (CNT) films which offered better support for sulfur, and investigated the effect of the surface properties and pore structure of the post-treated CNT films on Li-S battery performance. Post-treatments, i.e., acid treatment, unzip process and cetyltrimethylammonium bromide (CTAB) treatment, effectively modified the surface properties and pore structure of the CNT film. The modified pore structure impacted the ability of the CNT films to accommodate the catholyte, resulting in an increase in initial discharge capacity.

In this study, several kinds of active carbons with high specific surface area and micro pore structure were prepared from the coconut shell charcoal using chemical activation method. The physical property of prepared active carbon was investigated by experimental variables such as activating chemical agents to char coal ratio, flow rate of inert gas and temperature. It was shown that chemical activation with KOH and NaOH was successfully able to make active carbons with high surface area of 1900~2500 m2/g and mean pore size of 1.85~2.32 nm. The coin cell using water-based binder in the electrolyte of LiPF6 dissolved in mixed organic solvents (EC:DMC:EMC=1:1:1 vol%) showed better capacity than that of oil-based binder. Also, it was found that the coin cell of water-based binder shows an improved cycling performance and coulombic efficiency.

Silicon-carbon composite was prepared by the magnesiothermic reduction of mesoporous silica and subsequent impregnation with a carbon precursor. This was applied for use as an anode material for high-performance lithium-ion batteries. Well-ordered mesoporous silica(SBA-15) was employed as a starting material for the mesoporous silicon, and sucrose was used as a carbon source. It was found that complete removal of by-products (Mg2Si and Mg2SiO4) formed by side reactions of silica and magnesium during the magnesiothermic reduction, was a crucial factor for successful formation of mesoporous silicon. Successful formation of the silicon-carbon composite was well confirmed by appropriate characterization tools (e.g., N2 adsorption-desorption, small-angle X-ray scattering, X-ray diffraction, and thermogravimetric analyses). A lithium-ion battery was fabricated using the prepared silicon-carbon composite as the anode, and lithium foil as the counter-electrode. Electrochemical analysis revealed that the silicon-carbon composite showed better cycling stability than graphite, when used as the anode in the lithium-ion battery. This improvement could be due to the fact that carbon efficiently suppressed the change in volume of the silicon material caused by the charge-discharge cycle. This indicates that silicon-carbon composite, prepared via the magnesiothermic reduction and impregnation methods, could be an efficient anode material for lithium ion batteries.

Si-C composite with hollow spherical structure was synthesized using ultrasonic treatment of organosilica powder formed by hydrolysis of phenyltrimethoxysilane. The prepared powder was pyrolyzed at various temperatures ranging from 900 to 1300 ˚C under nitrogen atmosphere to obtain optimum conditions for Li-ion battery anode materials with high capacity and cyclability. The XRD and elemental analysis results show that the pyrolyzed Si/C composite at 1100 ˚C has low oxygen and nitrogen levels, which is desirable for increasing the electrochemical capacity and reducing the irreversible capacity of the first discharge. The solid Si-C composite electrode shows a first charge capacity of ~500 mAhg-1 and a capacity fade within 30 cycles of 0.93% per cycle. On the other hand, the electrochemical performance of the hollow Si-C composite electrode exhibits a reversible charge capacity of ~540 mAhg-1 with an excellent capacity retention of capacity loss 0.43% per cycle up to 30 cycles. The improved electrochemical properties are attributed to facile diffusion of Li ions into the hollow shell with nanoscale thickness. In addition, the empty core space provides a buffer zone to relieve the mechanical stresses incurred during Li insertion.

Carbon/silicon composites were synthesized by mixing silicon powders with petroleum pitch and subsequent heat-treatment. The resultant composites were composed of carbon and nano-size crystalline silicon identified by XRD and EDX. FIB images and SEM images were taken respectively to detect the existence of silicon impregnated in carbon and the distribution of silicon on the carbon surface. The obtained carbon/silicon materials were assembled as half cell anodes for lithium ion secondary battery and their electrochemical properties were tested. The pitch/silicon composite (3 : 1 wt. ratio) heat treated at 1000℃ and mixed with 55.5 wt.% of graphite showed relatively good electrochemical properties such as the initial efficiency of 78%, the initial discharge capacity of 605 mAh/g, and the discharge capacity of 500 mAh/g after 20 cycles.

Carbon materials of various morphologies were synthesized by pyrolysis of Soap-nut seeds (Sapindus mukorossi), Jack Fruit seeds (Artocarpus heterophyllus), Date-seeds (Phoenix dactylifera), Neem seeds (Azadirachta indica), Tea leaves (Ehretia microphylla), Bamboo stem (Bambusa bambus) and Coconut fiber (Cocos nucifera), without using any catalyst. Carbon materials thus formed were characterized by SEM XRD and Raman. Carbon thus synthesized varied in size (in μm) but all showed highly porous morphology. These carbon materials were utilized as the anode in Lithium secondary battery. Amongst the various precursors, carbon fibers obtained from Soap-nut seeds (Sapindus mukorossi) and Bamboo stem (Bambusa bambus), even after 100th cycles, showed the highest capacity of 130.29 mAh/g and 92.74 mAh/g respectively. Morphology, surface areas and porosity of carbon materials obtained from these precursors were analyzed to provide interpretation for their capacity to intercalate lithium. From the Raman studies it is concluded that graphitic nature of carbon materials assist in the intercalation of lithium. Size of cavity (or pore size of channels type structure) present in carbon materials were found to facilitate the intercalation of lithium.

In order to improve the lithium ion battery's performance, the carbon nanofibers were introduced to the anode electrode fabricated with natural graphite particles. The influence of structural adjustment of the particles by the introduction method of carbon nanofibers and the content of carbon nanofibers on the electrical property and charge/discharge characteristics of the electrode were investigated. The electrode fabricated with the mixture of 10 wt% of carbon nanofibers grown separately and 90 wt% of graphite particles showed an excellent discharge capacity of 400 mAh/g and the improved cycle performance. The improved performance could be explained by that the carbon nanofibers shortened and uniformly distributed on the surface of graphite particles by ball milling increased the stability for the intercalation/deintercalation of lithium ion and increased the electrical conductivity due to the closed packing between graphite particles.

The electrochemical behavior of the LiCoO2 electrode, containing carbon black as a conductor, depends upon the nature and characteristics of carbon black. In this study, six different kinds of carbon blacks were employed to investigate the relationship between the properties of carbon blacks and electrochemical characteristics of the electrode. The larger amount of surface oxygen functional groups brought the lower electrical conductivity for the carbon blacks. The electrical conductivity of carbon blacks was closely related to the impurities such as ash and volatile content. The rate capability and cyclability of the electrode were improved with the higher conductivity of carbon blacks used. So, it can be concluded that high conductive carbon black plays an important role as a conductor for high rate of charge-discharge capability and initial efficiency.