Titanium Dioxide-Based Nanocomposites: Properties, Synthesis, and Their Application in Energy Storage

Abstract

Energy storage technology is a valuable tool for storing and utilizing newly generated energy. Lithium-based batteries have proven to be effective energy storage units in various technological devices due to their high-energy density. However, a major obstacle to developing lithium-based battery technology is the lack of high-performance electrode materials with a long lifespan, superior rate capability, and high safety standards. Thus, the rational design of highly reliable electrode materials is crucial when considering the development of high-performance lithium-based batteries for sustainable energy storage. As a result, titanium dioxide-based nanocomposites have gained a lot of interest as potential electrode materials for lithium-based batteries due to their unique properties such as structural characteristics, low cost, safety, and environmental friendliness. Therefore, this chapter gives an overview of the properties, preparation methods, and application of titanium dioxide-based nanocomposites as anode and cathode active materials for high-performance lithium-based batteries.

1. Introduction

The need for energy is predicted to increase globally in the foreseeable future due to substantial population growth and technological advancements. Currently, more than 80% of the energy needed globally comes from fossil fuels [1, 2]. The widespread use of fossil fuels leads to massive emissions of greenhouse gases, such as carbon dioxide, which exacerbate climate change [3]. In addition, the significant growth in cities has led to increased use of transportation, which has raised pollution levels and other major environmental issues since conventional vehicles rely on the burning of fossil fuels [4]. Therefore, the transition from using conventional vehicles to environmentally friendly electrical vehicles (EVs) has hastened to prevent the worsening of the issues above.

Electric vehicles are predicted to replace a significant portion of today’s fleet, and several governments have already pledged to reduce the utilization of gasoline and diesel-powered vehicles by 2030 [5]. Energy storage technologies have become increasingly desirable due to the heavy reliance of EVs on energy storage devices. The energy storage markets are also striving to acquire more sustainable and eco-friendly materials to fulfill the increased demand of the electrified transportation sector [6]. Furthermore, the development of energy storage devices has surged rapidly due to the policies implemented by numerous countries to promote the development of clean energy. So, rechargeable electrochemical energy storage (EES) devices, which include flow batteries, lead (Pb)-acid batteries, lithium-based batteries, nickel-metal hydride (Ni-MH), and nickel-cadmium (Ni-Cd) batteries (Figure 1), are the most practical and effective energy storage options among other energy storage technologies [8].

Figure 1.

Different types of rechargeable batteries with respect to energy density. Reproduced with permission from ref. [7]. Copyright © 2022 Asep Suryatna et al.

Figure 1 illustrates that most rechargeable batteries are currently on the market, with the remainder being in various stages of research and development. The components of lithium-based batteries typically include an anode, a cathode, an electrolyte, and a separator that permits lithium ions (Li⁺) to pass through while preventing electron transfers within the anode and cathode. Those batteries store energy via the reversible intercalation/de-intercalation of Li⁺ between the anode and cathode. Most of those batteries are inadequate for high-energy applications like electric vehicles. Lithium-ion (Li-ion) batteries (Figure 2), which were first commercialized by Sony in 1991, have transformed portable electronics and are extensively utilized in various industries because of their enhanced performance in comparison to other battery types [5, 10, 11]. Though Li-ion batteries have more advantages than other types of batteries, their performance and strength in EVs are inadequate due to their low theoretical energy density (less than 350 Wh Kg⁻¹) [4, 12]. Furthermore, several obstacles stand in the way of their advancement, such as the unstable nature of the constituent parts, the short cycle life of existing designs, and the requirement for effective catalysts to expedite oxygen reactions [1, 13]. In response to the ever-increasing energy demand, the academic and industrial sectors are searching for novel battery chemistries beyond the existing Li-ion intercalation.

Figure 2.

Lithium-ion battery. Reproduced with permission from ref. [9]. Copyright © 2013 American Chemical Society.

To date, other lithium-based batteries, like lithium-sulfur (Li-S) and lithium-oxygen (Li-O₂), are being developed [7, 14]. Those batteries are anticipated to supplement or even replace Li-ion batteries in high-energy applications like electric vehicles due to their higher energy densities. However, those batteries also have some challenges such as sluggish kinetics during the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) which limit their practical applicability [15, 16]. Furthermore, the electrodes passivate as a result of low electrical conductivity and poor reversibility, further impairing the cycle stability and rate performance. Therefore, to realize their full potential and achieve their theoretical energy densities, their cathode and anode materials still require development [17].

It is noteworthy that electrochemical reactions that take place on the electrode surface are the main factors regulating battery performance [17]. As a result, the cathode and anode materials are essential to the battery’s overall functionality. When considering the use of lithium-based batteries for long-term, renewable energy storage, the development of practical and affordable electrodes is essential. The following are some typical requirements for battery electrode materials: (i) high electron and ion transport mobility to provide high power; (ii) excellent reversible storage capacity of energy and an appropriate operating voltage window for allowing high-energy storage density; and (iii) outstanding structural durability upon phase changes during redox reactions over several charging/discharging cycles to facilitate a long battery life [18, 19]. However, it is challenging to meet all the requirements utilizing single-material electrodes. Therefore, the development of electrode materials that can integrate several functional constituents and constructively exercise a synergistic impact to meet the requirements mentioned above at the same time is crucial.

From the perspective of electrode materials design, several electrocatalysts have been developed, and carbon materials (such as carbon nanotubes, graphene, black carbon, and their derivatives) are the most often utilized electrocatalysts because of their large surface area, porosity, and superior electrical conductivity [20, 21]. However, carbon-based materials show significant polarization following a few cycles, which is attributed to their poor catalytic activity and instability during the charging and discharging processes. As alternatives, metal oxides are currently being employed as electrodes, and among them, nanostructured titanium dioxide (TiO₂) has received much attention, but it does not fully satisfy all application requirements [20, 22]. Regarding this, titanium dioxide-based nanocomposites are regarded as promising electrode materials and have garnered a lot of interest since they can improve the functionality of already existing devices, such as the Li-ion battery and make future-oriented devices such as Li-O₂ and Li-S battery, more practical [22, 23, 24]. In this chapter, we present the work conducted on titanium dioxide-based nanocomposites in the area of electrochemical energy storage with more emphasis on lithium-based batteries. We pay particular attention to their properties, methods of synthesis, and application as anode and cathode materials for high-performance batteries.

2. TiO₂ properties

For many years, researchers have investigated the potential of TiO₂ as an effective semiconductor for use in dye-sensitized solar cells [25], photocatalytic water splitting [26], batteries [27], capacitors [28], and photocatalytic pollutants decomposition [29]. This broad spectrum of applications results from its unique material properties such as high chemical stability, nontoxicity, low production cost, commercial availability, and high resistance to photo-corrosion [30]. TiO₂ is typically found in nature in a variety of polymorphs, including rutile, anatase, brookite, and TiO₂(B) (B = Bronze), as shown in Figure 3 [31, 32].

Figure 3.

Polymorphs of Titania: Anatase, rutile, Brookite, and TiO₂-B. Reproduced with permission from ref. [31], open access. Copyright © 2023, licensee: MDPI, Basel, Switzerland.

All four forms of TiO₂ consist of TiO₆ octahedra, but each varies in its distortion of octahedron units and assembly of octahedra chains. Octahedra in anatase are arranged in zigzag chains along the (221) plane, sharing four edges; in rutile, the octahedra are arranged in linear chains parallel to the (001) plane, sharing only two edges; while brookite, on the other hand, both corners and edges are connected [33]. Also, TiO₂-B is primarily composed of layered titanate, and its structure is comparable to that of its layered precursor, which is made up of corrugated sheets that share edges and corners with TiO₆ octahedra as shown in Figure 3 [34]. These variations in lattice structures lead to discrepancies in mass densities and electronic band structures. Table 1 summarizes the physical properties of different TiO₂ polymorphs.

	Anatase	Rutile	Brookite	TiO2-B
Theoretical Density (g/cm^3)	3.84	4.26	4.11	3.64
Unit Cell Volume (Å^3)	34.02	31.12	32.20	35.27
Band Gap (eV)	3.20	3.00	3.30	3.29
Space group	I41/amd	P42/mnm	Pbca	C2/m
Crystal structure	Tetragonal	Tetragonal	Orthorhombic	Monoclinic

Table 1.

Physical properties of anatase, rutile, brookite, and TiO₂-B [33].

Additionally, a variety of physicochemical forms of TiO₂ such as nanoparticles, nanowires, nanorods, nanotubes, and nanofibers have been produced. Their distinct physical and chemical properties vary based on their crystallization, grain size, morphology, specific surface area, surface state, and porosity. These properties have been essential in the development of high-tech devices like rechargeable batteries [35]. However, despite TiO₂ remarkable qualities, its slow transport kinetics, poor conductivity, and particle agglomeration limit its use in energy storage, particularly in batteries [20, 22]. Thus, in order to promote the utilization of TiO₂ as an advanced electrode material in batteries, it is essential to alter its structural and morphological properties. To date, various strategies such as modification by metal or nonmetal doping, coupling with other materials, chemical or electrochemical reduction, and defect engineering have been proposed to modify TiO₂ to overcome the above-mentioned drawbacks [36, 37]. Although various strategies have been reported for modifying TiO₂, this chapter will focus solely on coupling TiO₂ with other materials as a way to improve its electrochemical properties.

3. TiO₂-based nanocomposites

It has been proposed that the electrochemical properties of TiO₂ as electrodes can be enhanced by coupling TiO₂ with other materials to form TiO₂-based nanocomposites [38]. These nanocomposites consist of metal sulfide, metal oxide, nitride, conductive polymer, and carbon materials, among others. Even though a wide range of materials have been identified as TiO₂ support materials, this section will only focus on coupling TiO₂ with carbon materials and other metal oxides. Table 2 presents various TiO₂-based nanocomposite electrodes for lithium-based batteries, their synthesis methods, and their electrochemical performance.

Composites	Synthesis route	Battery type	Capacity (mAh g^−1)	Reversible Cycles	Ref
ZnO/TiO2	Sol–gel	Li-ion	610	1000	[39]
TiO2–graphene	Hydrothermal	Li-ion	250	200	[40]
TiO2-C-Ts	Solvothermal	Li-ion	534	100	[41]
CNTs@TiO2	Solvothermal	Li-ion	212	1000	[42]
WO3/TiO2	Hydrothermal	Li-O2	—	150	[43]
TiO2/α-MnO2	Bio synthesis	Li-O2	6100	130	[20]
SiO2/TiO2	Electrolysis	Li-ion	1410.5	50	[44]
Graphene/TiO2	Precipitation	Li-ion	150	10	[45]
TiO2(B) nanowires/CNTs	Hydrothermal	Li-ion	330.18	200	[34]
TiO2-TiO-TiN@SnO2	Anodization	Li-ion	455.8	101	[46]
TiO2-TiO-TiN@MoO3			255.4
S@void@TiO2		Li-S	766	1000	[47]
Vo-TiO2/Ti3C2Tx	Ethanol-thermal treatment	Li-O2	13.87	100	[48]
Co3O4/3DOM-TiO2	In situ embedding	Li-O2	7635.9	288	[24]
TiO2@yV2O5	Sol–gel	Li-S	1408.6	200	[49]

Table 2.

Different TiO₂-based nanocomposites: Synthesis methods, battery type, and their electrochemical performances.

3.1 TiO₂-supported carbon-based nanocomposite

Coupling TiO₂ with carbon materials such as graphene, carbon nanotubes, and hard carbon has been reported to effectively improve the electrochemical performance of TiO₂. Carbon networks reduce the agglomeration and accumulation of TiO₂ nanostructures, improving the electrode’s overall electrical conductivity and facilitating Li⁺ and electron diffusion [22, 50]. For instance, Lin et al. [41] prepared hierarchically porous one-dimensional (1D) TiO₂-carbon tubular composites (TiO₂-C-Ts) featuring interconnected nanoflakes on the porous tube walls using a simple solvothermal alcoholysis followed by a subsequent calcination process. The as-synthesized composites exhibit high electrical conductivity, providing quick ion/electron transport pathways and ample space for storing the electrolyte while buffering the volume change during the Li⁺ insertion/extraction process. Huang et al. [51] synthesized TiO₂ hierarchical hollow tubes modified with disordered carbon (HT-TiO₂/C) via a facile hydrothermal process followed by calcination at 600°C for high-performance Li-ion batteries. The prepared HT-TiO₂/C shows outstanding rate performance and eminent long-cycle performance, which was ascribed to the short length of Li⁺ diffusivity, great structural stability, and enhanced conductivity due to the presence of carbon material.

Also, graphene is a carbon relative that shows outstanding mobility for electrons, making it an intriguing candidate for the incorporation of TiO₂ [40, 52]. Farooq et al. [40] developed a TiO₂-graphene nanocomposite via a microwave hydrothermal method for use in Li-ion batteries. During the Li⁺ insertion/extraction process, the synthesized nanocomposite exhibited a remarkably stable cycle life and high-rate capability performance due to the presence of carbon networks. When graphene is attached to TiO₂ nanoparticles, it creates channels for electron transport that increase electrical conductivity and overcome TiO₂’s internal resistance. Additionally, by acting as barrier layers, these conductive boundaries safeguard the TiO₂ from the electrolyte, resulting in better stability of the active materials and reduced parasitic electrolyte consumption [53, 54].

In addition, carbon nanotubes (CNTs) are widely utilized as an excellent candidate to synthesize highly valuable TiO₂ nanocomposite owing to their high conductivity, stability, and ease of manufacturing [42, 55]. Zhao et al. [42] demonstrate the importance of coupling TiO₂ with multiwall CNTs for high-rate and long-life Li-ion batteries using the solvothermal process. The excellent high-rate performance and cyclic stability of the produced nanocomposite have been credited to the synergistic contribution of pseudocapacitance and the electronic and ionic fast conductive network generated by CNTs in composites.

3.2 TiO₂-supported metal oxide nanocomposites

Another common modification method for TiO₂ is to use the good electrical conductivity of metal oxides to increase the capacity and cycling stability of electrodes. Numerous studies on the coupling of TiO₂ with metal oxides such as SnO₂ [56], SiO₂ [44], WO₃ [43], ZnO [39], etc. to enhance the materials’ electrochemical performance have been published. For instance: Wang et al. [56] synthesized SnO₂/TiO₂ nanoparticle structures utilizing a pulsed laser deposition (PLD) system for Li-ion batteries. The synthesized nanocomposites demonstrate high reversible capacity and high-rate capability as a result of the effective shortening of diffusion distance of lithium ions and restrict the electrode structure’s alteration during the reaction process, thereby greatly enhancing the electrode structure’s stability and integrity during the circulation process. Xue et al. [43] prepare a WO₃/TiO₂ heterojunction via hydrothermal reaction for a high-performance photo-assisted Li-O₂ battery. The prepared electrode demonstrates good cycling stability and rate capability due to the excellent structure of hetero-material features, low recombination rate, and high electronic conductivity. Core–shell TiO₂/α-MnO₂ nanocomposite was created by Pakseresht et al. [20] as an effective catalyst electrode for Li-O₂ batteries. Due to the dual catalytic activity of TiO₂ and α-MnO₂ combined with urchin-like MnO₂ nanostructures, the synthesized electrode showed a lower overpotential and a higher specific capacity than the bare TiO₂ electrode.

Moreover, Ma [39] developed ZnO/TiO₂ core–shell nanocomposites for lithium-ion batteries on a copper substrate utilizing the sol–gel technique. The nanocomposites exhibited outstanding reversibility, long-life cycling performance, greater capacity, coulombic efficiencies, and more stable behavior. The remarkable outcome was ascribed to the enhancement of Li-ion diffusion into the anode as a result of the formation of a high surface area, short diffusion path for Li-ions, and high electron transportation rate. Zhou et al. [44] utilized the direct electrolysis method to synthesize SiO₂/TiO₂ nanocomposite for Li-ion batteries. The synthesized nanocomposite exhibits improved reversible specific capacity and good cycling stability due to enhanced conductivity and the nanosized structures of the nanocomposite.

Overall, the above nanocomposites’ exceptional performance can be ascribed to large pore volume and specific surface area, improved electronic conductivity and ionic diffusivity, ability to prevent nanomaterial aggregation, and the conductive networks’ ability to mitigate structural changes, which are all desired for high-performance lithium batteries.

4. TiO₂-based nanocomposites synthesis methods

TiO₂-based nanocomposites have recently been synthesized via a variety of synthesis routes, as displayed in Table 2 [57]. It has been shown that synthesis techniques have substantial effects on the characteristics of materials. This section will highlight selected synthesis methods that are commonly utilized for the synthesis of nanocomposite materials of TiO₂-based. Table 3 summarizes the benefits and drawbacks of selected synthetic methods.

Process	Benefits	Drawbacks	Ref
Sol–gel	Cost-effectiveness,; Simplicity; Ease of scaling up	Time-consuming process; Formation of secondary phases; High annealing temperatures	[58]
Precipitation	Low cost; Ease of scaling up; Absence of harsh reaction conditions	Difficult in controlling the size and shape of the particles; Aggregation of the nanoparticles; Impurities	[58, 59]
Hydrothermal	Wide range of temperatures for a wide range of reactions; Controlled composition of the reactant	Require high pressure; High temperature	[58, 60]
Electrochemical Anodization	Simple and easy to handle; Impurity-free; Efficient and controlled process; Low-cost process	Incompatible with various substrates including silicon and glass	[61, 62]

Table 3.

Comparison of various fabrication processes.

4.1 Sol–get

The sol–gel process is a wet chemical technique used to produce porous and asymmetric nanoparticles. Metal alkoxide precursors are hydrolyzed and condensed to form a liquid solution (sol), which is then heated and stirred to form a solid-phase gel. The solid-phase gel is then dried based on desired properties and applications. This method can synthesize nanomaterials at low temperatures and is cost-effective, simple, quick, and easy to scale up. However, high annealing temperatures are necessary, which can compromise the structural stability of the synthesized materials [57, 58]. Thus, Ma [39] utilized sol-gel to synthesize ZnO/TiO₂ core-shell nanocomposites as an anode for Li-ion batteries. The produced nanocomposite exhibits excellent cycling performance, reversibility, and stability due to the core-shell structure that has the advantages of high surface area, high electron transportation rate, and short lithium-ion diffusion path.

4.2 Precipitation

The precipitation process is a reliable and safe chemical method to produce single or mixed electrocatalysts. The precipitation forms from a homogeneous solution through nucleation and particle growth. This method offers various benefits such as low cost, ease of scaling up, and the absence of harsh reaction conditions, like high synthesis temperatures. However, it has some limitations, such as controlling the size and shape of the particles and the possibility of nanoparticles aggregating due to the high surface-to-volume ratio. In addition, there is a chance that trace impurities may precipitate alongside the product during mixed oxide precipitation [58]. Diang et al. [45] utilize an in situ precipitation method to synthesize a large-scale production of graphene/TiO₂ nanocomposites. The synthesized nanocomposite exhibits exceptional electrochemical performance as an anode material for Li-ion batteries due to the large surface area of graphene/TiO₂ and the fast Li insertion/extraction in composites.

4.3 Hydrothermal

The hydrothermal process is an effective method for producing oxides and their nanocomposites with tunable structures. In this process, nanomaterials are dissolved and recrystallized in an autoclave by heating an aqueous fluid to extremely high temperature and pressure. The reaction pressure can be varied to control the morphology of the resulting nanomaterials. This method has been utilized to prepare numerous TiO₂-based nanomaterials [58, 60]. For example, Jiang, Luo, and Wen [34] employ hydrothermal synthesis to fabricate TiO₂(B) nanowires/CNTs as anode material for high-performance Li-ion batteries. The synthesized nanocomposites exhibit unique features of TiO₂(B) nanowires twined with CNTs. The findings imply that the exceptional electrochemical performance of the nanocomposites is caused by their distinct nanostructure and highly conductive carbon nanotubes, making them a viable anode candidate for Li-ion batteries.

4.4 Electrochemical anodization

Anodization is an electrolytic passivation process that is often used on metal surfaces to produce an oxide layer when exposed to air. This method utilizes two electrode configuration cells in the presence of an electrolyte to produce an oxide layer on the surface of the titanium foil upon the application of adequate voltage. It also allows for the control of stoichiometry and produces homogeneous materials. Due to its low cost and simple preparation methodology, this method has been widely used in the synthesis of TiO₂ nanotubes [61, 63]. During the synthesis process, titanium foil is utilized as the working electrode while platinum foil is used as the counter electrode. Prior to the electrochemical reaction, titanium foil precursors are pretreated in alcohol to remove impurities. Then, an oxidation reaction occurs by the migration of titanium ions to the electrolyte, forming the titanium dioxide layer. The competing dissolution reaction occurs on the newly formed TiO₂ layer and is caused by the diffusion of electrolyte ions through the oxide layer, resulting in porous nanotube morphology [64]. The applied potential and the choice of electrolyte influence nanotube diameter and tube length.

Kure-Chu et al. [46] conducted a study on the properties of TiO₂-TiO-TiN@SnO₂ and TiO₂-TiO-TiN@MoO₃ nanocomposite films created using the hybrid anodization method, which was used for high-safety Li-ion battery anodes. The synthesized composite films exhibited superior discharge capacities, which was attributed to the deposition of nanocrystalline SnO₂ and MoO₃ nanoparticles in the TiO₂-TiO-TiN films, as well as the existence of nanoporous structures that provided appropriate Li⁺ transfer pathways and reaction sites, resulting in extraordinary charge-transfer and extra capacity. This hybrid anodization method provides a viable technique to develop high-power-density and high-safety anode materials for Li-ion batteries.

5. Applications of TiO₂-based nanocomposites in energy storage

TiO₂-based nanocomposites have been extensively studied in various fields, particularly in energy conversion and storage devices. In this section, we will discuss different TiO₂-based nanocomposites that have been used as anode and cathode materials for high-performance lithium-based batteries.

5.1 TiO₂-based nanocomposites as anode materials

Anode is an essential component of lithium-based batteries, which play a significant role in the overall performance of the device [65]. An optimal anode material should fulfill the subsequent specifications such as (i) large pore size and short paths for fast Li⁺ diffusion; (ii) low volume change during Li⁺ insertion/desertions process; (iii) high specific surface area; (iv) minimal internal resistance; (v) low Li intercalation potential [11, 19, 65]. Table 4 gives some examples of TiO₂-based nanocomposites utilized as anode materials. Over the decade, TiO₂-based nanocomposite materials have been identified as promising anode materials because of their exceptional cycling stability and high-rate capacity [38, 69].

Material	Battery type	Capacity and Cycling Performance	Remarks	Ref
TiO2@Co-CNT-NC	Li-ion	300 mAh g^−1 after 1100 cycles	Through the use of nanocomposite materials, energy storage and conversion systems can rationally design high-performance anode materials for industrial use.	[66]
TiO2@CNTs	Li-ion	177.5 mAh g^−1, at 1.0 A g^−1 after 600 cycles	When compared to other materials, nanocomposite exhibits the best rate and cycling performance.	[67]
Vo-TiO2/Ti3C2Tx composite	Li-O2	~10 mAh cm^−2; over 750 h	Provide better rate performance and increased cycling stability.	[48]
Yolk-shell TiO2 (S@void@TiO2)	Li-S	766 mAh g^−1 after 1000 cycles	The optimized inner voids helped to decrease the volume variation of sulfur and the dissolution of polysulfides which results in enhanced activities.	[47]
TiO2 nanotubes	Li-O2	0.041 mAh cm^−2 (amorphous) and 0.031 mAh cm^−2 (anatase)	The amorphous TiO2 nanotubes exhibited structural and chemical detects, which function as Li^+ ion traps and increase the capacity.	[68]

Table 4.

TiO₂-based nanocomposites as anode electrode for lithium-based batteries.

Wang et al. [52] synthesize TiO₂ nanotube@graphene composites via a single-step hydrothermal synthesis which exhibits high storage capacity of 357 mAh g⁻¹ at 10 mA g⁻¹ when utilized as anodes in Li-ion batteries. The excellent performance was credited to the tubular structure of TiO₂ and the good electronic properties of graphene. Sidoli et al. [54] demonstrate the performance of new negative electrodes for Li-ion batteries based on defective graphene produced by scalable thermal exfoliation of graphite oxide and embellished with TiO₂ nanoparticles. After extensive and requiring cycling, the constructed composites show a reversible capacity of more than 180 mAh g⁻¹. This outcome surpasses the reversible capacity of pure TiO₂ electrodes by 327%. Furthermore, Ahmed et al. [70] synthesize graphitic carbon interfaced TiO₂ (TMGCs) from biowaste using a simple biogenic single precursor method, which they then use as the anode for Li-ion batteries. Compared to pristine materials, the prepared nanocomposite shows better Li⁺ ion storage capabilities. At a current density of 100 mA g⁻¹, the hybrid composite anode from TMGCs demonstrates an initial discharge capacity of 597 mAh g⁻¹, along with exceptional restoration (~ 100% at 0.1 A g⁻¹) and retention (94% at 0.5 A g⁻¹) capabilities. The enhanced electrical conductivity and effective Li⁺ ion transport of the TMGCs composite were ascribed to its higher specific surface area, which is due to the mesopores TiO₂ morphology and the distorted carbon sheets.

Moreover, Wu et al. [71] prepare double core–shell structure H-TiO₂/C/Fe₃O₄@rGO for Li-ion batteries anodes. The prepared composite exhibits exceptional electrochemical capabilities (867 mAh g⁻¹ after 200 cycles at 0.3 A g⁻¹), and long-cycle performance (505 mAh g⁻¹ after 700 cycles at 1.0 A g⁻¹). Zhou et al. [72] synthesized oxygen-deficient ZnTiO₃/TiO₂/C composite as an anode material for Li-ion battery using a bimetallic zeolite imidazole framework ZIF-8 (Zn, Ti) as the sacrificial template. At a current density of 300 mA g⁻¹, the synthesized composite exhibits an impressive reversible capacity of 357.6 mAh g⁻¹ after 400 cycles, and after 1500 cycles, it demonstrates exceptional rate performance with a reversible capacity of 155 mAh g⁻¹ at an elevated current density of 500 mA g⁻¹. The remarkable performance was attributed to the preservation of the nanostructure from the MOF precursor, the distinct electronic characteristic offered by the plentiful oxygen vacancies, and the combined influence of the multiphase composition reversibility. It should be noted that TiO₂-based nanocomposites display exceptional electrochemical performance not only as anode material for Li-ion batteries but also as an anode material for Li-O₂ and Li-S batteries, as highlighted in Table 4.

5.2 TiO₂-based nanocomposites as cathode materials

In addition to anode materials, the cathode also remains a crucial element in lithium-based batteries, impacting overall battery performance [73, 74]. Various TiO₂-based nanocomposites have been developed to date, and some examples are summarized in Table 5. Additionally, Yang et al. [79] use atomic layer deposition to synthesize amorphous oxygen-deficient TiO₂-x on carbon nanotubes for use as cathode materials in Li-O₂ batteries. The prepared cathode exhibits exceptional electrocatalytic activity toward electrode reactions, due to the presence of oxygen-deficient TiO₂-x in the nanocomposites. Together with excellent cycling performance and cyclic retention of over 90 cycles, the nanocomposite exhibits high discharge/charge capacities. The results offer valuable insights regarding the impact of TiO₂ oxygen vacancies on electrochemical efficiency.

Material	Battery type	Capacity and Cycling Performance	Remarks	Ref
Ru/TiO2/CNTs	Li-O2	Fixed capacity of 500 mAh g^−1; at a current density of 100 mA g^−1 after 110 cycles	When discharged, the synthetic cathode showed a porous state and was able to catalyze the creation of Li2O2 that resembled snow. This meant that it would be very friendly throughout the subsequent cycling and charging process.	[13]
Co3O4@3DOM-TiO2	Li-O2	Specific capacity of 7635.9 mAh g^−1 at 100 mA g^−1, better rate capability and cycling durability (288 cycles at 200 mA g^−1)	The remarkable catalytic performances are primarily attributable to the mutual benefits among the diverse constituents within the nanocomposite.	[24]
TiO2@yV2O5 (y = 0.025–0.045)	Li-S	High capacity retention of 91% and 93% at 0.5 C and 1 C after 50 cycles	An insight into the development of long-life Li–S batteries may be gained from the remarkable cycle stability of the nanocomposite material with high sulfur loading as the cathode.	[49]
S@TiO2/Ti2C	Li-S	The initial discharge-specific capacity was 1408.6 mAh g^−1 at 0.2 C with a high sulfur content of 78.4 wt.%. At a high current rate of 2 C and 5 C, the batteries still maintained a capacity of up to 464.0 and 227.3 mAh g^−1 after 200 cycles, respectively	The synergistic effect between the conductivity and relieving the volumetric expansion of Ti2C for cathode materials and the encapsulation and adsorption of TiO2 for active sulfur was primarily responsible for the enhanced electrochemical properties of the composites.	[75]
TiO2 NTs@Ni	Li-S	Capacity of 719 mAh g^−1 after 100 cycles	TiO2 NTs with large surface areas offer plenty of space for reactions and quick channels for ions and electrons to transfer, while nickel improves the cathode’s electric conductivity and polysulfide adsorption capacity.	[76]
TiS2-TiO2 (anatase) hybrid sheets	Li-ion	A high capacity of 100 mAh g^−1 is after 100 cycles	Strong photoelectron generation is guaranteed by TiS2-TiO2 nanosheets because of their enhanced electron conductivity and high Li-ion diffusion.	[77]
TiO2 coated Li2MnO3	Li-ion	Highest capacity of 125.2 mAh g^−1 after 100 cycles	High specific capacity, improved high-rate cycling performance, and excellent cycle life were ascribed to the low interface resistance and high diffusion coefficient of lithium ions.	[78]

Table 5.

TiO₂-based nanocomposites as cathode electrodes for lithium-based batteries.

Furthermore, Li et al. [80] fabricate CoS₂-TiO₂@carbon core–shell fibers as a cathode host material for high-performance Li-S batteries through a combination of coaxial electrospinning and selective vulcanization method. The synthesized core–shell fibers demonstrate exceptional electrochemical performance with an initial specific capacity of 1181.1 mAh g⁻¹ and a high capacity of 736.5 mAh g⁻¹ after 300 cycles with high coulombic efficiency over 99.5% (capacity decay of 0.06% per cycle). The study provides an alternative way to solve the limitation of high-performance sulfur electrode materials. Moreover, Cai et al. [81] synthesize a cocklebur-like sulfur host with the TiO₂-VO_x heterostructure (CTVHs) for long-life Li–S batteries. Because of the heterostructure, the high adsorption energy heterojunction interface serves as a capturing center for lithium polysulfides (LiPSs), ensuring quick diffusion to VO_x. With high catalytic activity toward LiPSs and quick lithium-ion migration, the defect-rich spiny VO_x can efficiently carry out one-step adsorption diffusion transformation. The synthesized cathode achieves nearly 100% coulombic efficiency at 0.5 C (Coulomb) over 1400 cycles with a slow capacity decay rate of 0.029% per cycle. This suggested approach offers numerous opportunities to support LiPS adsorption conversion for long-life Li–S batteries.

Also, Yuan et al. [82] created a novel nanotube-in-tube CNT@void@TiO₂@C material with long cycling stability and outstanding ultrahigh rate capability for Li-ion storage. The synthesized material shows remarkable electrochemical performance, with a notable ultrahigh rate capability of 55 mAh g⁻¹ at 300 C (Coulomb), a high reversible capacity of 601 and 468 mAh g⁻¹ at 0.5 C (Coulomb), and exceptional long-term cycling stability of 180.3 mAh g⁻¹ up to 3000 cycles with a capacity loss rate of 0.013% annually at 10 C (Coulomb). The discharge capacity was observed to recover to 90% of the initial 1 C (Coulomb) after a series of ultrahigh rate tests, indicating good structural stability and considerable reversibility. The resolution of cathode passivation in Li-O₂ batteries with an amination SiO₂/TiO₂ functional separator was proposed by Li et al. [83]. The outcomes show that the Li-O₂ cells with super p–carbon and catalyst-free cathode, which benefit from the separator, have improved electrochemical capacity (5645 mAh g⁻¹ at a current density of 200 mA g⁻¹), excellent charging capability (discharge voltage of 2.43 V at a current density of 1.5 A g⁻¹), and particularly superior cycle stability up to 268 cycles. These results offer a possible way to stop batteries from dying too soon.

6. Conclusion

To sum up, the development and implementation of ecologically friendly energy storage technologies have been acknowledged as an unquestionable way to deal with unparalleled environmental imbalances. Energy storage technology plays a vital role in addressing energy and environmental issues in energy systems. This technology lays the groundwork for the energy system, ensuring that energy supply and demand are balanced and enabling a range of cutting-edge services. TiO₂-based nanocomposites have been extensively researched due to their unique physical and chemical properties in order to maximize their effectiveness as anode or cathode materials for lithium-based batteries. The findings demonstrate that TiO₂-based nanocomposites with effective Li⁺ ion transport and high electronic conductivity are ideal electrode materials for high-performance lithium-based batteries. Although there has been a significant breakthrough in the development of TiO₂-based nanocomposite electrode materials, further research is still required to realize their full potential and achieve their theoretical energy densities.

Acknowledgments

The authors appreciate the support from the Catalysis group of the Advanced Materials Division at Mintek.

Funding statements

The authors appreciate the financial support received from Mintek’s parliamentary grant.

Declaration of competing interest

The authors declare no conflict of interest.