Advances in silicon-carbon composites anodes derived from agro wastes for applications in lithium-ion battery: A review

Recently, the growing demand for high-performing batteries and different environmental challenges (such include global warming and climate change) have increased the requirement and demand for Lithium-ion batteries (LIBs) used in advanced technologies (i.e., electric cars and many others). To meet this increasing demand, there is an urgent need for more advanced technologies and materials. In the pursuit of developing anode materials, silicon has emerged as the utmost favourable choice for the next generation of LIBs, aiming to substitute the commonly used graphite. Carbon is commonly used to render silicon (Si) suitable for use since Si cannot be used directly as the electrode in LIBs. One of the recently discovered techniques in the development of high-performance LIBs is the use of inexpensive, sustainable, renewable, and eco-friendly materials. Agro-waste-derived silicon and carbon are often used as long as they don't negatively affect the LIB anode's performance. This review paper presents the advances in the development of silicon-carbon (Si/C) composite anodes sourced from agro-waste for applications in LIBs. It provides an overview of agro-waste-derived silicon-based anode materials and techniques for extracting silica from agricultural wastes. Next, the outline explains the preparation technique of Si/C composites obtained from agricultural residues for use in LIBs. Additionally, the paper delves into recent research challenges and the potential prospects of materials derived from agro-waste in the advancement of sophisticated LIBs battery materials.

Surface nitridation of Li4Ti5O12 by thermal decomposition of urea to improve quick charging capability of lithium ion batteries

As the application of lithium-ion batteries in electric vehicles increases, the demand for improved charging characteristics of batteries is also increasing. Lithium titanium oxide (Li₄Ti₅O₁₂, LTO) is a negative electrode material with high rate characteristics, but further improvement in rate characteristics is needed for achieving the quick-charging performance required by electric vehicle markets. In this study, the surface of LTO was coated with a titanium nitride (TiN) layer using urea and an autogenic reactor, and electrochemical performance was improved (initial Coulombic efficiency and the rate capability were improved from 95.6 to 4.4% for pristine LTO to 98.5% and 53.3% for urea-assisted TiN-coated LTO, respectively. We developed a process for commercial production of surface coatings using eco-friendly material to further enhance the charging performance of LTO owing to high electronic conductivity of TiN.

Ti-Based Oxide Anode Materials for Advanced Electrochemical Energy Storage: Lithium/Sodium Ion Batteries and Hybrid Pseudocapacitors

Titanium-based oxides including TiO₂ and M-Ti-O compounds (M = Li, Nb, Na, etc.) family, exhibit advantageous structural dynamics (2D ion diffusion path, open and stable structure for ion accommodations) for practical applications in energy storage systems, such as lithium-ion batteries, sodium-ion batteries, and hybrid pseudocapacitors. Further, Ti-based oxides show high operating voltage relative to the deposition of alkali metal, ensuring full safety by avoiding the formation of lithium and sodium dendrites. On the other hand, high working potential prevents the decomposition of electrolyte, delivering excellent rate capability through the unique pseudocapacitive kinetics. Nevertheless, the intrinsic poor electrical conductivity and reaction dynamics limit further applications in energy storage devices. Recently, various work and in-depth understanding on the morphologies control, surface engineering, bulk-phase doping of Ti-based oxides, have been promoted to overcome these issues. Inspired by that, in this review, the authors summarize the fundamental issues, challenges and advances of Ti-based oxides in the applications of advanced electrochemical energy storage. Particularly, the authors focus on the progresses on the working mechanism and device applications from lithium-ion batteries to sodium-ion batteries, and then the hybrid pseudocapacitors. In addition, future perspectives for fundamental research and practical applications are discussed.

Nickel molybdate nanorods supported on three-dimensional, porous nickel film coated on copper wire as an advanced binder-free electrode for flexible wire-type asymmetric micro-supercapacitors with enhanced electrochemical performances

Wire-shaped micro-supercapacitors attracted extensive attentions in next-generation portable and wearable electronics, due to advantages of miniature size, lightweight and flexibility. Herein, NiMoO₄ nanorods supported on Ni film coated Cu wire are successfully fabricated thorough direct deposition of Ni film onto Cu wire as the conductive substrate, followed by growth of the NiMoO₄ nanorods on Ni film coated Cu wire substrate by means a hydrothermal annealing process. The prepared 3D, porous electrode demonstrates extremely high areal specific capacitance of 12.03F cm^-2 at the current density of 4 mA cm^-2 and retained capacitance of 8.23 F cm^-2 at a much higher current density of 80 mAcm^-2. The electrode, also, shows an excellent cycling stability with capacitance retention of 99.3% after 3000 cycles. The superior electrochemical performance can be attributed to the high area surface, low contact resistance between NiMoO₄ nanorods and Cu wire current collector and presence of a 3D and porous structure provides many electroactive sites and sufficient open space for easy diffusion of the electrolyte ions during redox reactions. Benefiting from their structural features, a fiber shaped asymmetric micro-supercapacitor based on NiMoO₄/Ni film/Cu wire as the positive electrode and carbon fiber coated with reduced graphene oxide as the negative electrode is assembled. The fabricated fiber device presents a wide potential window between 0 and 1.7 V and exhibits high specific capacitance of 0.504F cm^-2 (38.8F cm^-3) at a current density of 4.8 mA cm^-2 with a high energy density of 202 µWh cm^-2 (15.6 mWh cm^-3) at a power density of 4050 µW cm^-2 (313 mWh cm^-3). The energy density retains 124 µWh cm^-2 (9.54 mWh cm^-3) when the power density is increased to 13530 µW cm^-2 (1040.73 mWh cm^-3). In addition, the asymmetric device exhibits an outstanding cycling stability (98.5% capacitance retention after 1000 consecutive cycles) and good mechanical stability. Therefore, this work suggested the promising potential of NiMoO₄ nanorods supported on Ni film coated Cu wire as an advanced electrode material for construction of flexible and portable next-generation energy storage micro-devices with superior electrochemical performances.

Improving the electrochemical performance of Li4Ti5O12 anode by phosphorus reduction at a relatively low temperature

A novel and efficient method is demonstrated to improve the electrochemical performance of Li4Ti5O12 and metal-oxide anodes. In contrast to other methods, inexpensive red phosphorus powder is used as a reducing reagent, and the reduction is conducted at a relatively low temperature of 400 °C. This method offers a low cost and effective way for Li4Ti5O12 and metal-oxide anode applications.

Hybrid porous bamboo-like CNTs embedding ultrasmall LiCrTiO4 nanoparticles as high rate and long life anode materials for lithium ion batteries

Compared with Li₄Ti₅O₁₂, LiCrTiO₄ with the same spinel structure exhibits superior conductivity and Li⁺ diffusion properties. However, there has been no extensive study on LiCrTiO₄ as an anode material in lithium ion batteries, due to its pulverization, loss of electrical contact, and particle aggregation. A unique architecture based on hybrid porous CNTs embedding ultrasmall LiCrTiO₄ nanoparticles (6 ± 2 nm) was designed by using a facile sol-gel process combined with subsequent heat treatment. As an anode for lithium ion batteries, due to the absence of the aforementioned problems, the electrode exhibited high reversible capacity, excellent rate capability and superior long-term cycling stability at high current densities. Such nanocomposites should be competitive candidates to replace Li₄Ti₅O₁₂-based anode materials.

Li4 Ti5 O12 Anode: Structural Design from Material to Electrode and the Construction of Energy Storage Devices

Spinel Li₄ Ti₅ O₁₂ , known as a zero-strain material, is capable to be a competent anode material for promising applications in state-of-art electrochemical energy storage devices (EESDs). Compared with commercial graphite, spinel Li₄ Ti₅ O₁₂ offers a high operating potential of ∼1.55 V vs Li/Li⁺ , negligible volume expansion during Li⁺ intercalation process and excellent thermal stability, leading to high safety and favorable cyclability. Despite the merits of Li₄ Ti₅ O₁₂ been presented, there still remains the issue of Li₄ Ti₅ O₁₂ suffering from poor electronic conductivity, manifesting disadvantageous rate performance. Typically, a material modification process of Li₄ Ti₅ O₁₂ will be proposed to overcome such an issue. However, the previous reports have made few investigations and achievements to analyze the subsequent processes after a material modification process. In this review, we attempt to put considerable interest in complete device design and assembly process with its material structure design (or modification process), electrode structure design and device construction design. Moreover, we have systematically concluded a series of representative design schemes, which can be divided into three major categories involving: (1) nanostructures design, conductive material coating process and doping process on material level; (2) self-supporting or flexible electrode structure design on electrode level; (3) rational assembling of lithium ion full cell or lithium ion capacitor on device level. We believe that these rational designs can give an advanced performance for Li₄ Ti₅ O₁₂ -based energy storage device and deliver a deep inspiration.

Dual-phase spinel Li4Ti5O12/anatase TiO2 nanosheet anchored 3D reduced graphene oxide aerogel scaffolds as self-supporting electrodes for high-performance Na- and Li-ion batteries

Self-supporting LTO-AT/RGO composite as anode materiel was prepared via a facile hetero-assembly, freeze-drying, mechanical compression and annealing. They exhibit excellent electrochemical capability when used for LIBs and SIBs.

Facile synthesis of an Al-doped carbon-coated Li4Ti5O12 anode for high-rate lithium-ion batteries

Sol–gel synthesized LTAO/C composites demonstrated capacity retention of 97.9% at 20C after 100 cycles.

Structure and electrochemical properties of Sm-doped Li4Ti5O12 as anode material for lithium-ion batteries

Sm doping has a great impact on discharge capacity, rate capability and cycling performance of LTO anode materials for lithium-ion batteries.

Sb doped Li4Ti5O12 hollow spheres with enhanced lithium storage capability

The Sb doped Li₄Ti₅O₁₂ hollow spheres with an average diameter of around 3.5 μm were synthesized successfully via through a two-step process. Sb⁵⁺ doping can improve the capacity and maintain the cycling stability.

Controlling Solid-Electrolyte-Interphase Layer by Coating P-Type Semiconductor NiOx on Li4Ti5O12 for High-Energy-Density Lithium-Ion Batteries

Li4Ti5O12 is a promising anode material for rechargeable lithium batteries due to its well-known zero strain and superb kinetic properties. However, Li4Ti5O12 shows low energy density above 1 V vs Li(+)/Li. In order to improve the energy density of Li4Ti5O12, its low-voltage intercalation behavior beyond Li7Ti5O12 has been demonstrated. In this approach, the extended voltage window is accompanied by the decomposition of liquid electrolyte below 1 V, which would lead to an excessive formation of solid electrolyte interphase (SEI) films. We demonstrate an effective method to improve electrochemical performance of Li4Ti5O12 in a wide working voltage range by coating Li4Ti5O12 powder with p-type semiconductor NiOx. Ex situ XRD, XPS, and FTIR results show that the NiOx coating suppresses electrochemical reduction reactions of the organic SEI components to Li2CO3, thereby promoting reversibility of the charge/discharge process. The NiOx coating layer offers a stable SEI film for enhanced rate capability and cyclability.

Hollow Ball-in-Ball CoxFe3-xO4 Nanostructures: High-Performance Anode Materials for Lithium-Ion Battery

The intrinsic electronic conductivity can be improved by doping efficiently. CoxFe3-xO4 nanostructures have been synthesized for the first time to improve the conductivity of lithium battery electrode. The solid solution CoxFe3--xO4 were characterized by X-ray diffraction pattern (XRD), Raman spectrum, scanning electron microscopy (SEM), transmission electron microscope (TEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The results show that the doping enlarge the lattice spacing but the structure of Co3O4 is stable in the Li-ion intercalation/deintercalation process. The AC impedance spectrum reveals the conductivity is well improved. In addition, the solid solution CoxFe3-xO4 exhibit excellent electrochemical characteristics. The electrodes with 20% molar ratio of Fe ions own a reversible capacity of 650.2 mA h g(-1) at a current density of 1 A g(-1) after 100 cycles.

The combustion behavior of large scale lithium titanate battery

Safety problem is always a big obstacle for lithium battery marching to large scale application. However, the knowledge on the battery combustion behavior is limited. To investigate the combustion behavior of large scale lithium battery, three 50 Ah Li(Ni_xCo_yMn_z)O₂/Li₄Ti₅O₁₂ batteries under different state of charge (SOC) were heated to fire. The flame size variation is depicted to analyze the combustion behavior directly. The mass loss rate, temperature and heat release rate are used to analyze the combustion behavior in reaction way deeply. Based on the phenomenon, the combustion process is divided into three basic stages, even more complicated at higher SOC with sudden smoke flow ejected. The reason is that a phase change occurs in Li(Ni_xCo_yMn_z)O₂ material from layer structure to spinel structure. The critical temperatures of ignition are at 112–121°C on anode tab and 139 to 147°C on upper surface for all cells. But the heating time and combustion time become shorter with the ascending of SOC. The results indicate that the battery fire hazard increases with the SOC. It is analyzed that the internal short and the Li⁺ distribution are the main causes that lead to the difference.

The improved effect of co-doping with nano-SiO2and nano-Al2O3on the performance of poly(methyl methacrylate-acrylonitrile-ethyl acrylate) based gel polymer electrolyte for lithium ion batteries

We report a novel gel polymer electrolyte (GPE) for lithium ion batteries, which is prepared using P(MMA-AN-EA) as a polymer matrix and doping with nano-SiO₂and nano-Al₂O₃simultaneously.

Ti3+ self-doped Li4Ti5O12 nanosheets as anode materials for high performance lithium ion batteries

Ti³⁺ self-doped Li₄Ti₅O1₂ (S-LTO) nanosheets exhibit high specific capacity, excellent rate performance and outstanding cycling stability.

High rate capabilities of Li4Ti5−xVxO12 (0 ≤ x ≤ 0.3) anode materials prepared by a sol–gel method for use in power lithium ion batteries

The electrochemical performance results show that the highest capacities, 208 (0.2 C), 198 (0.5 C), 189 (1 C), 179 (2 C), 157 mA h g⁻¹ (5 C), are obtained from the LTOV06 electrode, which are higher than those of the LTO electrodes reported.

Improvement of the Ar/N2 binary plasma-treated carbon passivation layer deposited on Li4Ti5O12 electrodes for stable high-rate lithium ion batteries

Improvement of the Ar/N₂ binary plasma-treated carbon passivation layer deposited on Li₄Ti₅O₁₂ electrodes for stable high-rate lithium ion battery.

PO43− doped Li4Ti5O12 hollow microspheres as an anode material for lithium-ion batteries

PO₄³⁻ doped Li₄Ti₅O₁₂ hollow microspheres present stable cycling stability and outstanding high-rate capability due to the slight increase in the number of diffusion paths for lithium ions by doping with large PO₄³⁻ anions.

Rapid charge-discharge property of Li4Ti5O12-TiO2 nanosheet and nanotube composites as anode material for power lithium-ion batteries

Well-defined Li4Ti5O12-TiO2 nanosheet and nanotube composites have been synthesized by a solvothermal process. The combination of in situ generated rutile-TiO2 in Li4Ti5O12 nanosheets or nanotubes is favorable for reducing the electrode polarization, and Li4Ti5O12-TiO2 nanocomposites show faster lithium insertion/extraction kinetics than that of pristine Li4Ti5O12 during cycling. Li4Ti5O12-TiO2 electrodes also display lower charge-transfer resistance and higher lithium diffusion coefficients than pristine Li4Ti5O12. Therefore, Li4Ti5O12-TiO2 electrodes display lower charge-transfer resistance and higher lithium diffusion coefficients. This reveals that the in situ TiO2 modification improves the electronic conductivity and electrochemical activity of the electrode in the local environment, resulting in its relatively higher capacity at high charge-discharge rate. Li4Ti5O12-TiO2 nanocomposite with a Li/Ti ratio of 3.8:5 exhibits the lowest charge-transfer resistance and the highest lithium diffusion coefficient among all samples, and it shows a much improved rate capability and specific capacity in comparison with pristine Li4Ti5O12 when charging and discharging at a 10 C rate. The improved high-rate capability, cycling stability, and fast charge-discharge performance of Li4Ti5O12-TiO2 nanocomposites can be ascribed to the improvement of electrochemical reversibility, lithium ion diffusion, and conductivity by in situ TiO2 modification.

Carbon-decorated Li₄Ti₅O₁₂/rutile TiO₂ mesoporous microspheres with nanostructures as high-performance anode materials in lithium-ion batteries

Li4Ti5O12/rutile TiO2 (LTO-RT) composites with Li/Ti molar ratios of 3:5, 4:5 and 4.5:5 have been successfully synthesized with TiO2 microspheres as a precursor. Furthermore, C-coated LTO-RT mesoporous microspheres with a molar ratio of 4:5 (C/4-5-LTO-RT) have been prepared based on the LTO-RT composite through a hydrothermal method and high temperature calcination. After various characterizations, it is found that carbon plays a pivotal role in retaining the porous nanostructure of the original as-prepared TiO2 precursor in the overall process. Substantially, C/4-5-LTO-RT still shows a high specific surface area of 63.70 m(2) g(-1) even after high temperature treatment at 800 °C. Since the porous nanostructure offers open and direct channels for the diffusion of Li ions and electrons and carbon decoration also efficiently improves the electrical conductivity, the sample of C/4-5-LTO-RT shows an enhanced electrochemical performance. In addition, the presence of nanosized rutile TiO2 in C/4-5-LTO-RT has an important contribution to the high electrochemical performance, as does the fast lithium ion diffusion along the [001] direction.

Zr4+ doping in Li4Ti5O12 anode for lithium-ion batteries: open Li+ diffusion paths through structural imperfection

One-dimensional nanomaterials have short Li(+) diffusion paths and promising structural stability, which results in a long cycle life during Li(+) insertion and extraction processes in lithium rechargeable batteries. In this study, we fabricated one-dimensional spinel Li4Ti5O12 (LTO) nanofibers using an electrospinning technique and studied the Zr(4+) doping effect on the lattice, electronic structure, and resultant electrochemical properties of Li-ion batteries (LIBs). Accommodating a small fraction of Zr(4+) ions in the Ti(4+) sites of the LTO structure gave rise to enhanced LIB performance, which was due to structural distortion through an increase in the average lattice constant and thereby enlarged Li(+) diffusion paths rather than changes to the electronic structure. Insulating ZrO2 nanoparticles present between the LTO grains due to the low Zr(4+) solubility had a negative effect on the Li(+) extraction capacity, however. These results could provide key design elements for LTO anodes based on atomic level insights that can pave the way to an optimal protocol to achieve particular functionalities.

Stabilization of oxygen-deficient structure for conducting Li4Ti5O12-δ by molybdenum doping in a reducing atmosphere

Li4Ti5O12 (LTO) is recognized as being one of the most promising anode materials for high power Li ion batteries; however, its insulating nature is a major drawback. In recent years, a simple thermal treatment carried out in a reducing atmosphere has been shown to generate oxygen vacancies (VO) for increasing the electronic conductivity of this material. Such structural defects, however, lead to re-oxidization over time, causing serious deterioration in anode performance. Herein, we report a unique approach to increasing the electronic conductivity with simultaneous improvement in structural stability. Doping of LTO with Mo in a reducing atmosphere resulted in extra charges at Ti sites caused by charge compensation by the homogeneously distributed Mo(6+) ions, being delocalized over the entire lattice, with fewer oxygen vacancies (VO) generated. Using this simple method, a marked increase in electronic conductivity was achieved, in addition to an extremely high rate capability, with no performance deterioration over time.

Oxidative stability and reaction mechanism of lithium bis(oxalate)borate as a cathode film-forming additive for lithium ion batteries

The most possible oxidative decomposition reaction path of EC–BOB⁻cluster.

Carbon-encapsulated F-doped Li4Ti5O12 as a high rate anode material for Li+ batteries

TiO2 nanoparticles aggregated into a regular ball-in-ball morphology were synthesized by hydrothermal processing and converted to carbon-encapsulated F-doped Li4Ti5O12 (LTO) composites (C-FLTO) by solid state lithiation at high temperatures. Through the careful control of the amount of carbon precursor (D(+)-glucose monohydrate) used in the process, LTO encapsulated with a continuous layer of nanoscale carbon was formed. The carbon encapsulation served a dual function: preserving the ball-in-ball morphology during the transformation from TiO2 to LTO and decreasing the external electron transport resistance. The fluoride doping of LTO not only increased the electron conductivity of LTO through trivalent titanium (Ti(3+)) generation, but also increased the robustness of the structure to repeated lithiation and delithiation. The best-performing composite, C-FLTO-2, therefore delivered a very satisfying performance for a LTO anode: a high charge capacity of ∼158 mA h g(-1) at the 1 C rate with negligible capacity fading for 200 cycles and an extremely high rate performance up to 140 C.