Interfacial Charge Transfer Research Articles

Heterostructure of perovskite coupled graphitic carbon nitride for enhanced photodegradation under visible light

This study aimed to prepare and characterize LaFeO3 nanoparticles loaded graphitic carbon nitride (LFO/g-C3N4) photocatalyst and investigate the degradation of organic pollutants under UV and natural sunlight exposure. It is observed that LFO nanoparticles of an average size of about 67 nm were distributed on g-C3N4 sheets through chemical bonding owing to the formation of a composite. Compared to LFO and g-C3N4, composite has a good absorption ability to harvest more UV and visible light due to its large surface area and pore size. The photocatalytic studies revealed that the g-C3N4/LFO composite exhibits higher catalytic efficiency and stability for methylene blue (MB) degradation under UV and visible light. Under UV irradiation, the degradation efficiency of LFO, g-C3N4, and g-C3N4/LFO composite in synthetic wastewater was found to be around 50, 80 and 93 % with corresponding rate constants 0.05, 0.02, and 0.1 min−1 in 30 min, respectively. Under natural sunlight, the composite degraded 97 % of MB in 180 min with a rate constant of 0.016 min1. The higher photocatalytic activity of the composite was attributed to the interfacial charge transfer between LaFeO3 and g-C3N4, which are responsible for effective charge separation in the composite. Further, it has been investigated that singlet oxygen species (1O2) and hydroxyl radicals (•OH) are the main reactive species that contributed considerably to the complete degradation of MB. The nanocomposite was also demonstrated to be a stable catalyst and can be reused without any further modification.

Enhanced charge transfer through defect and doping synergistic engineering for efficient hydrogen production

Simultaneous modification of catalysts by surface defects and atomic doping strategies can effectively inhibit the recombination of photogenerated carriers. In this study, the surface state of MoS2 was adjusted through the synergistic effects of sulfur defects and the doping of oxygen atoms, successfully constructing a type II heterojunction with hydrogen-substituted graphdiyne (H-GDY) for efficient photocatalytic hydrogen generation. The results showed that the H-GDY/O-MoS2-x exhibits the best hydrogen production performance (2272.97 μmol/g/h), which is about 25 times that of MoS2. And the synergistic effect of sulfur defects and oxygen doping engineering can modulate the energy band structure and increase the interfacial potential difference between H-GDY and O-MoS2-x, which enhances the driving force of electron transfer and improves the interfacial charge transfer and separation efficiency. This work shows that the synergistic effect of defect and doping engineering can effectively improve the photocatalytic performance and provides a new idea for the preparation of sulfide-based photocatalysts.

Investigating the role of internal electric fields on interfacial charge transfer dynamics in 2D MoSTe/WSeTe heterojunction for photocatalytic water splitting

Introducing the degrees of freedom brought by intrinsic dipole moments into heterojunctions allows for effective manipulation through the combination of different interfaces, thus offering more possibilities for designing high-performance photocatalysts. The influence of internal electric fields (EIN) in Janus materials on heterojunction interface charges is a crucial aspect of understanding the intrinsic mechanisms of charge transfer at interfaces. To address this, we construct four contact modes of MoSTe/WSeTe heterojunctions, considering the work function difference as a mediator to quantify two different electric fields. It is estimated that the influence of the interfacial electric field (EIF) on interfacial charge transfer is approximately 1.6 times that of the EIN (pointing outwards the interface). Moreover, the direction of the EIN varies, resulting in different impacts on interface charges. Subsequently, we also discuss the conditions under which different charge transfer modes are formed at different contact surfaces. On the other hand, the heterojunction of the Te-S mode can serve as a direct Z-Scheme photocatalyst for overall water splitting, and the presence of vacancies is necessary to address the issue of surface passivation. Our study not only refines the intrinsic mechanism of interfacial charge transfer in Janus-based heterojunctions but also predicts a direct Z-Scheme photocatalyst capable of achieving overall water splitting.

Harnessing the interfacial charge transfer in Mn-doped γ-Fe2O3@ZnO heterojunction for broad spectrum photocatalytic degradation of organic dyes

Developing affordable, sustainable, and environmentally friendly water remediation strategies is inevitable to achieve water security worldwide. To align with these challenges, this investigation successfully synthesized low-cost Mn-doped iron oxide and its heterojunction with Zinc Oxide (ZnO) as an efficient recovery mechanism for deteriorated water. Comprehensive characterization of Mn-doped γ-Fe2O3@ZnO heterojunction was performed using X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy, Energy dispersive X-ray, and Photoluminescence analysis. The electrical behaviors of all samples were characterized using Electrochemical impedance spectroscopy and Mott-Schottky analysis. This heterojunction showed distinct structural features along with a bandgap energy of 2.61 eV, confirming the formation of a heterojunction. The effectiveness of this heterojunction was assessed using Congo red (CR) and Crystal violet as model pollutants. The photodegradation capability using a small amount of as-synthesized photocatalyst (10 mg) reached 90.8 % for CR and 90.5 % for CV under natural sunlight for a duration of 105 min. The key findings of this report clearly demonstrated the effectiveness of the interfacial charge transfer mechanism of Mn-γ-Fe2O3@ZnO heterojunction towards the degradation of organic water contaminants.

Effect of interlayer twisting angle on electronic and optical properties of graphene/MoS2 heterostructure

Abstract Based on the first-principles calculation, the electronic and optical properties of the graphene/MoS2 heterostructure at different twisting angles are studied. The interface contact type changes from N-Schottky contact to Ohmic contact with the interlayer twisting angle of 40.90°, which is accompanied by the interfacial charge transfer from graphene to MoS2, and the increase of the contribution of Mo–d xy , Mo–d x 2−y2 orbitals in the conduction band and S–p z , Mo–s, Mo–p z and Mo–d z 2 orbitals in the valence band. Interestingly, the absorption coefficient, reflectivity and refractive index are improved in the infrared region when the twisting angle is 40.90°. In the visible light range, the absorption coefficient increases, while the refractive index decreases, and the reflectivity at 2.8 eV increases. In the ultraviolet region, the absorption coefficient reaches 1.2 × 106 cm−1 at 11.6 eV with a twisting angle of 30°. The results provide an effective way to apply materials in the photoelectric field.

Multifunctional Conductive MOFs Enhance the Photocatalytic Hydrogen Evolution Efficiency of S-Type Ni3(HITP)2/TiO2 Heterojunctions.

Despite their high surface area, remarkable porosity, and efficient charge transfer mechanisms, conductive MOFs have found limited utilization within the domain of photocatalysis. In this study, we synthesized a cutting-edge S-type Ni3(HITP)2/TiO2 heterojunction photocatalyst exhibiting outstanding light harvesting and prolonged lifetime of photogenerated electrons through an in situ synthesis approach. Compared with TiO2, the composite materials not only significantly increase the specific surface area by 4.07 times but also expand the visible light absorption edge from 400 to 1100 nm. The hydrogen production rate of Ti/Ni-3 reached 4.927 mmol·g-1·h-1, which is 4.51 times that of TiO2. The S-type interface charge transfer pathway of the Ni3(HITP)2/TiO2 composite material was inferred by band structure, in situ XPS, SPV, and free radical capture, which improves charge separation and extends the carrier lifetime to undergo directional migration driven by an IEF. This is the main reason for the improved photocatalytic performance of Ni3(HITP)2/TiO2 composite materials.

Ambient Air-Synthesized CsPbBr3 Nanocrystals Coupled with TiO2 Film as an Efficient Hybrid Photoanode for Photoelectrochemical Methanol-to-Formaldehyde Conversion.

Due to its exceptional optoelectronic properties in the visible spectrum, cesium lead bromide (CsPbBr3) perovskite has attracted considerable attention in solar-driven organic transformations via photoelectrochemical (PEC) cells. However, the performance of the devices is adversely affected by electron-hole recombination occurring between a transparent conductive substrate, such as fluorine-doped tin dioxide (FTO), and a perovskite layer. Herein, to mitigate this issue, a compact layer of titanium dioxide (TiO2) was employed as both an electron transport layer and a hole blocking layer to diminish charge recombination while facilitating electron transfer in such perovskite material. At the oxidation peak potential of 0.70 V vs Ag/AgNO3, a hybrid photoanode of CsPbBr3/TiO2/FTO exhibited a significant increase in photocurrent density, from 15 to 41 μA/cm2, compared to a configuration without a TiO2 layer. Furthermore, the introduction of methanol as a hole scavenger in the PEC system using the hybrid photoanode facilitated the separation of electron-hole pairs, which led to an enhanced photocurrent density of 60 μA/cm2 and promoted the production of formaldehyde. High-performance liquid chromatography (HPLC) confirmed the generation of formaldehyde at a concentration of 26.69 μM with a Faradaic efficiency of 92% under an applied potential of 0.50 V vs Ag/AgNO3 for 60 min of PEC reaction. In addition to the enhanced PEC performance achieved from this hybrid photoanode, CsPbBr3 nanocrystals (NCs) in this work were synthesized by the modified one-pot method under ambient air, where highly uniform and high-purity NCs were obtained. This work signifies the groundbreaking exploration of CsPbBr3 NCs with TiO2 as a photoelectrode material in the organic-based PEC cells, which efficiently improved the interfacial charge transfer within the photoanode for the conversion of methanol to formaldehyde, marking a significant advancement in the field.

Charge-transfer dipole low-frequency vibronic excitation at single-molecular scale.

Scanning tunneling microscopy (STM) vibronic spectroscopy, which has provided submolecular insights into electron-vibration (vibronic) coupling, faces challenges when probing the pivotal low-frequency vibronic excitations. Because of eigenstate broadening on solid substrates, resolving low-frequency vibronic states demands strong decoupling. This work designs a type II band alignment in STM junction to achieve effective charge-transfer state decoupling. This strategy enables the successful identification of the lowest-frequency Hg(ω1) (Raman-active Hg mode) vibronic excitation within single C60 molecules, which, despite being notably pronounced in electron transport of C60 single-molecule transistors, has remained hidden at submolecular level. Our results show that the observed Hg(ω1) excitation is "anchored" to all molecules, irrespective of local geometry, challenging common understanding of structural definition of vibronic excitation governed by Franck-Condon principle. Density functional theory calculations reveal existence of molecule-substrate interfacial charge-transfer dipole, which, although overlooked previously, drives the dominant Hg(ω1) excitation. This charge-transfer dipole is not specific but must be general at interfaces, influencing vibronic coupling in charge transport.

Nanoflower-like NiCoFe layered hydroxide by in-situ electrochemical corrosion as highly efficient electrocatalyst for water oxidation

Layered double hydroxides have been widely applied for oxygen evolution reaction (OER) in the alkaline water electrolysis. However, the issues of poor connection between the catalyst and nickel foam and the specific mechanisms for active sites has not been fully documented. In this study, the in-situ nickel foam etching in a mixed solution of ferric chloride and cobalt nitrate at low temperatures was adopted for NiCoFe layered ternary hydroxides (NiCoFe LTHs) synthesis with a better tight integration. Physicochemical characterization indicated that the NiCoFe LTHs could grow directly through corroding nickel foam with a nano-flower-like morphology and structures. That is favorable for electron transfer from the catalytic layer to the conductive substrate. With the transition metal ions interaction and the tight integration construction, NiCo1Fe4-LTH-T60/NF presented an enhanced electrolysis performance with the overpotential of 234 mV (1.464 V vs. RHE) at current density of 100 mA cm−2 in 1 M KOH electrolyte. The Tafel slope for NiCo1Fe4-LTH-T60/NF electrode was 36.19 mV dec−1 for an enhanced OER kinetics. Besides, it demonstrated faster interfacial charge transfer process, better intrinsic electrochemical activity and stability in large current stability testing. It was revealed that the synergistic effect of the transition metal ions interaction enhancement and the mechanism of oxygen evolution elementary reaction for NiCo1Fe4-LTH-T60/NF during the water electrolysis by the electrochemical and theoretical calculation. This work provides theoretical basis and experimental support for the design and synthesis of future OER catalyst and substrate, which is significant for hydrogen and oxygen generation from water electrolysis.

The coupling effect of polarization and lattice strain on charge transfer between quintuple-layer Al2X3/Al2Y3 (X, Y = O, S, Se, Te; X ≠ Y) interfaces

The electronic properties of two-dimensional (2D) polar semiconductor heterostructures are closely related to the degree of interlayer charge transfer. Taking 2D quintuple-layer (QL)-Al2S3 and QL-Al2O3 semiconductor as examples, we study the electronic properties and interlayer charge transfer of QL-Al2S3/Al2O3 interfaces by first-principles calculations. The driving force of the directional interlayer charge transfer is the polarization electric field. The kinetic process of interface charge transfer is related to the charge (strain) distribution of QL-Al2S3 and QL-Al2O3. By changing the strain distribution of QL-Al2S3/Al2O3 interfaces with same polarization arrangement, the electronic properties and interfacial charge transfer of heterojunctions can be adjusted. Our work is an important indicator for understanding the dynamic process of interlayer charge transfer between 2D polar semiconductors. In addition, we propose one method for regulating the electronic properties of heterojunctions by coupling polarization and lattice strain.

Ultrafast Charge Transfer-Induced Unusual Nonlinear Optical Response in ReSe2/ReS2 Heterostructure.

Ultrafast charge transfer in van der Waals heterostructures can effectively engineer the optical and electrical properties of two-dimensional semiconductors for designing photonic and optoelectronic devices. However, the nonlinear absorption conversion dynamics with the pump intensity and the underlying physical mechanisms in a type-II heterostructure remain largely unexplored, yet hold considerable potential for all-optical logic gates. Herein, two-dimensional ReSe2/ReS2 heterostructure is designed to realize an unusual transition from reverse saturable absorption to saturable absorption (SA) with a conversion pump intensity threshold of approximately 170 GW/cm2. Such an intriguing phenomenon is attributed to the decrease of two-photon absorption (TPA) of ReS2 and the increase of SA of ReSe2 with the pump intensity. Based on the characterization results of X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, femtosecond transient absorption spectrum, Kelvin probe force microscopy, and density functional theory calculation, a type-II charge-transfer-energy level model is proposed combined with the TPA of ReS2 and SA of ReSe2 processes. The results reveal the critical role of ultrafast interfacial charge transfer in tuning the unusual nonlinear absorption and improving the SA of ReSe2/ReS2 under different excitation wavelengths. Our finding deepens the understanding of nonlinear absorption physical mechanisms in two-dimensional heterostructure materials, which may further diversify the nonlinear optical materials and photonic devices.

Halogen-Bonded Hole-Transport Material Enhances Open-Circuit Voltage of Inverted Perovskite Solar Cells.

Interfacial properties of a hole-transport material (HTM) and a perovskite layer are of high importance, which can influence the interfacial charge transfer dynamics as well as the growth of perovskite bulk crystals particularly in inverted structure. The halogen bonding (XB) has been recognized as a powerful functional group to be integrated with new small molecule HTMs. Herein, a carbazole-based halo (iodine)-functional HTM (O1), is synthesized for the first time, demonstrating a high hole mobility and suitable energy levels that align well with those of perovskites. The strong interaction between O1 and perovskite, i.e., I···I-, induces the formation of an ordered interlayer, which are verified by both theoretical and experimental studies. Compared to the reference HTM (O2) without any halo-function, the XB-induced interlayer effectively enhances the interfacial charge extraction efficiency, while significantly hindering the non-radiative charge recombination by reducing the surface traps upon the strong passivation effect. This is reflected as a big increase in the open-circuit voltage by up to 114mV in the fabrication of inverted devices with the highest power conversion efficiency of 22.34%. Moreover, the ordered XB-driven interlayer at the interface of O1 and perovskite is mainly responsible for the extended lifespan under the operational conditions.

Molecular-Level Pore Tuning in 2D Conductive Metal-Organic Frameworks for Advanced Supercapacitor Performance.

Two-dimensional (2D) electrically conductive metal-organic frameworks (MOFs) have emerged as viable candidates for active electrode materials in supercapacitors due to their high electrical conductivity, high specific surface area, and intrinsic redox-active sites. Despite their promising electrochemical performance, their pseudocapacitive behavior via fast and reversible charge transfer reactions remains yet to be fully exploited. Here, we investigate the electrochemical energy storage mechanism of Cu3(HHTATP)2 (HHTATP = 2,3,6,7,10,11-hexahydroxy-1,5,9-triaminotriphenylene), a 2D conductive MOF featuring characteristic redox-active pendant aromatic amines. Cu3(HHTATP)2 exhibited pseudocapacitive charge storage with an average gravimetric capacitance of 340 ± 15 F g-1 at a discharge rate of 0.2 A g-1 and maintained a capacitance retention over 90% after 7000 galvanostatic cycles at 5 A g-1. The polar pendant amines not only enhanced capacitance via additional amine/imine redox activity but also reduced interfacial charge transfer resistance through modified electrode-electrolyte interactions. These results highlight the potential of molecular-level pore environment tuning as a strategic approach in materials design for energy storage applications.

CsPbBr3 and Cs2AgBiBr6 Composite Thick Films with Potential Photodetector Applications

This paper investigates the optoelectronic properties of CsPbBr3, a lead-based perovskite, and Cs2AgBiBr6, a lead-free double perovskite, in composite thick films synthesized using mechanochemical and hot press methods, with poly(butyl methacrylate) as the matrix. Comprehensive characterization was conducted, including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–visible spectroscopy (UV–Vis), and photoluminescence (PL). Results indicate that the polymer matrix does not significantly impact the crystalline structure of the perovskites but has a direct impact on the grain size and surface area, enhancing the interfacial charge transfer of the composites. Optical characterization indicates minimal changes in bandgap energies across all different phases, with CsPbBr3 exhibiting higher photocurrent than Cs2AgBiBr6. This is attributed to the CsPbBr3 superior charge carrier mobility. Both composites showed photoconductive behavior, with Cs2AgBiBr6 also demonstrating higher-energy (X-ray) photon detection. These findings highlight the potential of both materials for advanced photodetector applications, with Cs2AgBiBr6 offering an environmentally Pb-free alternative.

Charge Transfer Plasmonics in Bespoke Graphene/α-RuCl3 Cavities.

Surface plasmon polaritons (SPPs) provide a window into the nano-optical, electrodynamic response of their host material and its dielectric environment. Graphene/α-RuCl3 serves as an ideal model system for imaging SPPs since the large work function difference between these two layers facilitates charge transfer that hole dopes graphene with n ∼ 1013 cm-2 free carriers. In this work, we study the emergent THz response of graphene/α-RuCl3 heterostructures using our home-built cryogenic scanning near-field optical microscope. Using phase-resolved imaging, we clearly observe long wavelength, heavily damped THz SPPs in a series of variable-size graphene cavities. From this, we extract the plasmonic wavelength and scattering rate in the graphene/α-RuCl3 heterostructures. We determine that the measured plasmon wavelength and electronic scattering rate match our heterostructures' theoretically predicted values. Our results demonstrate that shaping graphene into bespoke cavity structures enables observation and quantification of SPPs in heavily doped graphene that are largely not addressable with other experimental techniques. Moreover, the manifest lack of metallicity observed in the adjacent doped α-RuCl3 layer provides significant constraints on the nature of the interfacial charge transfer in this 2D heterostructure.

Fabrication of pyridine incorporated and O-doped g-C3N4/COF: A type-II heterojunction for enhanced hydrogen production under visible light irradiation

The fabrication of heterojunction photocatalysts is important for achieving highly efficient electron transfer, charge separation, and catalytic activity. In this study, we report the successful creation of a type II heterojunction between pyridine incorporated and O-doped g-C3N4 (POCN) and a covalent organic framework (COF). The heterojunction formation significantly reduced the fluorescence intensity of the POCN/COF, indicating effective separation of electron-hole pairs. Additionally, POCN/COF demonstrated excellent interface charge transfer resistance and photocurrent response. Its hydrogen production rate was remarkably high at 3500 μmol g⁻1 h⁻1, about 1.6 times that of pure COF (2200 μmol g⁻1 h⁻1) and 3.5 times that of the physical mixture (1000 μmol g⁻1 h⁻1), and it also exhibited enhanced stability. This indicates that it can be effectively fabricated into a heterojunction of POCN and COF. The optimal value for adding POCN was approximately 5 wt% of COF. This demonstrates greater activity compared to other composite catalysts made from graphitic carbon nitride and COF. This study presents a valuable approach for fabricating reusable heterojunction photocatalytic systems and efficiently generating hydrogen from natural energy sources.

Eliminating Charge Transfer at Cathode-Electrolyte Interface for Ultrafast Kinetics in Na-Ion Batteries.

Sodium-ion batteries suffer from kinetic problems stemming from sluggish ion transport across the electrode-electrolyte interface, causing rapid energy decay during fast-charging or low-temperature operation. One exciting prospect to enhance kinetics is constructing neuron-like electrodes that emulate fast signal transmission in a nervous system. It has been considered that these bioinspired designs enhance electron/ion transport of the electrodes through carbon networks. However, whether they can avoid sluggish charge transfer at the electrode-electrolyte interface remains unknown. By connecting the openings of carbon nanotubes with the surface of carbon-coated Na3V2O2(PO4)2F cathode nanoparticles, here we use carbon nanotubes to trap Na+ ions released from the nanoparticles during charge. Therefore, Na+ movement is confined only inside the neuron-like cathode, eliminating ion transport between the electrolyte and cathode, which has been scarcely achieved in conventional batteries. As a result, a 14-fold reduction in interfacial charge transfer resistance is achieved when compared to unmodified cathodes, leading to superior fast-charging performance and excellent cyclability up to 200C, and surprisingly, reversible operation at low temperatures down to -60 °C without electrolyte modification, surpassing other Na3V2O2(PO4)2F-based batteries reported to date. As battery operation has relied on charge transfer at the electrode-electrolyte interface for over 200 years, our approach departs from this traditional ion transport paradigm, paving the way for building better batteries that work under harsh conditions.

Enhanced Ferroelectric Polarization in Au@BaTiO3 Yolk-in-Shell Nanostructure for Synergistic Boosting Visible-Light- Piezocatalytic CO2 Reduction.

Developing efficient photo-piezocatalytic systems to achieve the conversion of renewable energy to chemical energy emerges enormous potential. However, poor catalytic efficiency remains a significant obstacle to future practical applications. Herein, a series of unique Au@BaTiO3 (Au@BT) yolk-shell nanostructure photo-piezocatalyst is constructed with single Au nanoparticle (Au NP) embedded in different positions within ferroelectric BaTiO3 hollow nanosphere (BT-HNS). This special structure showcases excellent mechanical force sensitivity and provides ample plasmon-induced interfacial charge-transfer pathways. In addition, the powerful piezoelectric polarization electric field induced by the enhanced ferroelectric polarization electric field via corona poling treatment in BT-HNS further promotes charge separation, CO2 adsorption and key intermediate conversion. Notably, BT with single Au NP encapsulated into hollow nanosphere shell with reinforced polarization (Au@BT-1-P) shows synergistically improved photo-piezocatalytic CO2 reduction activity for producing CO with a high production rate of 31.29 µmol g-1 h-1 under visible light irradiation and ultrasonic vibration. This work highlights a generic tactic for optimized design of high-performance and multifunctional nanostructured photo-piezocatalyst. Meanwhile, these yolk-in-shell nanostructures with single Au nanoparticle as an ideal model may hold great promise to inspire in-depth exploration of carrier dynamics and mechanistic understanding of the catalytic reaction.

Interface Synergy of Exposed Oxygen Vacancy and Pd Lewis Acid Sites Enabling Superior Cooperative Photoredox Synthesis.

Photo-driven cross-coupling of o-arylenediamines and alcohols has emerged as an alternative for the synthesis of bio-active benzimidazoles. However, tackling the key problem related to efficient adsorption and activation of both coupling partners over photocatalysts towards activity enhancement remains a challenge. Here, we demonstrate an efficient interface synergy strategy by coupling exposed oxygen vacancies (VO) and Pd Lewis acid sites for benzimidazole and hydrogen (H2) coproduction over Pd-loaded TiO2 nanospheres with the highest photoredox activity compared to previous works so far. The results show that the introduction of VO optimizes the energy band structure and supplies coordinatively unsaturated sites for adsorbing and activating ethanol molecules, affording acetaldehyde active intermediates. Pd acts as a Lewis acid site, enhancing the adsorption of alkaline amine molecules via Lewis acid-base pair interactions and driving the condensation process. Furthermore, VO and Pd synergistically promote interfacial charge transfer and separation. This work offers new insightful guidance for the rational design of semiconductor-based photocatalysts with interface synergy at the molecular level towards the high-performance coproduction of renewable fuels and value-added feedstocks.

Unraveling the contribution of nucleation to the intercalation energy barrier for phase-transforming Li-ion battery materials

Phase-transforming intercalation compounds, such as LiFePO4 (LFP) and Li4Ti5O12 (LTO), are widely utilized in Li-ion batteries, particularly for applications requiring high power and operation at low temperatures. However, the impact of phase transformation kinetics on energy density losses under extreme conditions has been largely unexplored. Specifically, the role of nucleation, the initial stage of phase transformation, in contributing to battery performance losses has not been previously investigated. In this study, we not only quantified the significance of material-level factors, such as interfacial charge transfer, in the low-temperature and high-rate performance of LFP and LTO materials, but also provided the first estimates of the apparent activation energies of nucleation. Our findings revealed that nucleation, particularly in the case of LFP, contributes significantly to overpotential, highlighting its pivotal role among material-level factors. Furthermore, our analysis allowed us to differentiate between material-level and particle-level limitations for the LTO/LFP cell, emphasizing the paramount importance of controlling the porosity of secondary particles to ensure high tolerance towards high-rate/low-temperature discharge.