Antisite Defects Research Articles

Multi-chalcogenides CuAg-II-IV-VI: a first-principles exploration of promising absorbing materials for solar cell applications

Cu2ZnSnS4 quaternary chalcogenides have attracted considerable attention owing to their remarkable photoelectric properties. However, the presence of antisite defects poses a significant obstacle to the further advancement of these chalcogenides. In this study, we employed a first-principles approach to assess 540 CuAg-II-IV-VI compounds based on structural stability, band gap, effective mass, and optical properties. The objective was to identify promising candidate materials for solar absorption. As indicated by the results, CuAgZnGeSe4, CuAgBeSnSe4, CuAgBeGeSe4, CuAgZnSiTe4, and CuAgBeSiTe4 exhibit ideal band gaps ranging from 1.45 to 1.58 eV, low effective masses, and high absorption coefficients in the visible light spectrum, comparable to the benchmark material Cu2ZnSnS4. The findings of this study present novel insights for the development of highly efficient multi-chalcogenide solar cells.

Effect of Starting Powder Particle Size on the Thermoelectric Properties of Hot-Pressed Bi0.3Sb1.7Te3 Alloys.

P-type Bi0.3Sb1.7Te3 polycrystalline pellets were fabricated using different methods: melting and mechanical alloying, followed by hot-press sintering. The effect of starting powder particle size on the thermoelectric properties was investigated in samples prepared using powders of different particle sizes (with micro- and/or nano-scale dimensions). A peak ZT (350 K) of ~1.13 was recorded for hot-pressed samples prepared from mechanical alloyed powder. Moreover, hot-pressed samples prepared from ≤45 μm powder exhibited similar ZT (~1.1). These high ZT values are attributed both to the presence of high-density grain boundaries, which reduced the lattice thermal conductivity, as well as the formation of antisite defects during milling and grinding, which resulted in lower carrier concentrations and higher Seebeck coefficient values. In addition, Bi0.3Sb1.7Te3 bulk nanocomposites were fabricated in an attempt to further reduce the lattice thermal conductivity. Surprisingly, however, the lattice thermal conductivity showed an unexpected increasing trend in nanocomposite samples. This surprising observation can be attributed to a possible overestimation of the lattice thermal conductivity component by using the conventional Wiedemann-Franz law to estimate the electronic thermal conductivity component, which is known to occur in nanocomposite materials with significant grain boundary electrical resistance.

A first principles investigation of defect energetics and diffusion in actinide dioxides

In this work, we have studied the formation and migration of various neutral intrinsic defects in AnO2. The non-stoichiometric defects such as vacancy defect, interstitial defect, and antisite defect as well as stoichiometric defects such as Schottky defect and Frenkel pairs has been considered for investigation. The formation energies of point defects are much higher in ThO2 as compared to UO2 and PuO2. The binding energy of defect clusters indicate that formation of Frenkel pair and Schottky defect is favorable over individual defects in ThO2. In case of UO2 and PuO2, hyper-stoichiometric defects are more stable than hypo-stoichiometric defects. The results obtained in this work are in good agreement with experimental results.

Double perovskite Sr2FeMo0.6Mg0.25Ga0.15O6−δ as high-performance fuel electrode for reversible solid oxide cell

B-site double perovskite Sr2FeMo0.6Mg0.25Ga0.15O6−δ (SFMMG) is reported as a promising fuel electrode for reversible solid oxide cell. The SFMMG material shows excellent structural stability in both oxidizing and reducing atmospheres, possesses an appropriate thermal expansion coefficient, as well as excellent redox cycle stability. The result confirms that the Mg2+ and Ga3+ tend to occupy the B-site while some Fe ions moves to the B′-site, creating lots of FeB–O–FeB’ anti-site defects in the lattice. As a result, a high electrical conductivity value of 36.0 S cm−1 is obtained at 800 °C in H2. Besides, the SFMMG electrode exhibits good catalytic activity toward hydrogen oxidation/evolution reaction, as confirmed by the low polarization resistance of 0.237 Ω cm2 at 800 °C in H2. With SFMMG as the fuel electrode, the La0.8Sr0.2Ga0.8Mg0.2O3-δ (300 μm)-supported single cell exhibits a peak power density of 1073 mW cm−2 in fuel cell mode and an electrolysis current density of 1192 mA cm−2 in electrolysis cell mode at 900 °C. In addition, the single cell shows stable performance during 100 h operation under 0.75 V at 800 °C.

Defect structure regulation and thermoelectric transfer performance in n-type Bi<sub>2–<i>x</i></sub> Sb<sub><i>x</i></sub>Te<sub>3–<i>y</i></sub>Se<sub><i>y</i></sub>-based compounds

Bi<sub>2</sub>Te<sub>3</sub>-based compounds are thermoelectric materials with the best performance near room temperature. The existence of a large number of complex defects makes defect engineering a core stratagem for adjusting and improving the thermoelectric performance. Therefore, understanding and effectively controlling the existence form and concentration of defects is crucial for achieving high-thermoelectric performance in Bi<sub>2</sub>Te<sub>3</sub>-based alloy. Herein, a series of Cl doped n-type quaternary Bi<sub>2–<i>x</i></sub> Sb<sub><i>x</i></sub>Te<sub>3–<i>y</i></sub>Se<sub><i>y</i></sub> compounds is synthesized by the zone-melting method. The correlation between defect evolution process and thermoelectric performance is systematically investigated by first-principles calculation and experiments. Alloying Sb on Bi site and Se on Te site induce charged structural defects, leading to a significant change in the carrier concentration. For Bi<sub>2–<i>x</i></sub> Sb<sub><i>x</i></sub>Te<sub>2.994</sub>Cl<sub>0.006</sub> compounds, alloying Sb on Bi site reduces the formation energy of the <inline-formula><tex-math id="M6">\begin{document}${\mathrm{S}}{{\text{b}}_{{\mathrm{Te}}}}_{_2}$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M6.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M6.png"/></alternatives></inline-formula> antisite defect, which generates the antisite defect <inline-formula><tex-math id="M7">\begin{document}${\mathrm{S}}{{\text{b}}_{{\mathrm{Te}}}}_{_2}$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M7.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M7.png"/></alternatives></inline-formula> and accompanied with the increase of the minority carrier concentration from 2.09×10<sup>16</sup> to 3.99×10<sup>17</sup> cm<sup>–3</sup>. The increase of the minority carrier severely deteriorates the electrical transport properties. In contrast, alloying Se in the Bi<sub>1.8</sub>Sb<sub>0.2</sub>Te<sub>2.994–<i>y</i></sub>Se<sub><i>y</i></sub>Cl<sub>0.006</sub> compound significantly lowers the formation energy of the complex defect <inline-formula><tex-math id="M8">\begin{document}${\mathrm{S}}{{\mathrm{e}}_{{\mathrm{Te}}}}$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M8.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M8.png"/></alternatives></inline-formula>+<inline-formula><tex-math id="M9">\begin{document}${\mathrm{S}}{{\mathrm{b}}_{{\mathrm{Bi}}}}$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M9.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M9.png"/></alternatives></inline-formula>, which becomes more energetically favorable and suppresses the formation of the antisite defect <inline-formula><tex-math id="M10">\begin{document}${\mathrm{S}}{{\text{b}}_{{\mathrm{Te}}}}_{_2}$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M10.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20240098_M10.png"/></alternatives></inline-formula>. As a result, the concentration of minority carriers decreases to 1.46×10<sup>16</sup> cm<sup>–3</sup>. This eliminates the deterioration effect of the minority carrier on the electrical transport properties of the material and greatly improves the power factor. A maximum power factor of 4.49 mW/(m·K<sup>2</sup>) is achieved for Bi<sub>1.8</sub>Sb<sub>0.2</sub>Te<sub>2.944</sub>Se<sub>0.05</sub>Cl<sub>0.006</sub> compound at room temperature. By reducing thermal conductivity through intensifying the phonon scattering via alloying Sb and Se, the maximum <i>ZT</i> value of 0.98 is attained for Bi<sub>1.8</sub>Sb<sub>0.2</sub>Te<sub>2.844</sub>Se<sub>0.15</sub>Cl<sub>0.006</sub> compound at room temperature. Our finding provides an important guidance for adjusting point defects, carrier concentrations, and thermoelectric performances in Bi<sub>2</sub>Te<sub>3</sub>-based compounds with complex compositions.

Enhanced magnetic anisotropy of iridium dimers on antisite defects of two-dimensional transition-metal dichalcogenides.

The combination of transition-metal (TM) elements with two-dimensional (2D) transition-metal dichalcogenides (TMDs) provides an effective route to realizing a 2D controllable magnetic order, leading to significant applications in multifunctional nanospintronics. However, in most TM atoms@TMDs nanostructures, it is challenging for the magnetic anisotropy energy (MAE) to exceed 30 meV when affected by the crystal field. Hence, the stronger magnetic anisotropy of TMDs has yet to be developed. Here, utilizing first-principle calculations based on density functional theory (DFT), a feasible method to enhance the MAEs of TMDs via configurating iridium dimers (Ir2) on 2D traditional and Janus TMDs with antisite defects is reported. Calculations revealed that 28 of the 54 configurations considered possessed structure-dependent MAEs of >60 meV per Ir2 in the out-of-plane direction, suggesting the potential for applications at room temperature. We also showed the ability to tune the MAE further massively by applying a biaxial strain as well as the surface asymmetric polarization reversal of Janus-type substrates. This approach led to changes to >80 meV per Ir2. This work provides a novel strategy to achieve tunable large magnetic anisotropy in 2D TMDs. It also extends the functionality of antisite-defective TMDs, thereby providing theoretical support for the development of magnetic nanodevices.

Rational control of the typical surface defects of hybrid perovskite using tetrahexylammonium iodide.

There are numerous defects existing on the surface and grain boundary of perovskite, which adversely affect the performance and stability of perovskite solar cell devices. Systematic first-principles calculations show that the I vacancy (VI), Pb vacancy (VPb), Pb-I antisite (PbI), and I-Pb antisite (IPb) defects can significantly affect the electronic properties of the surface of formamidinium lead triiodide (FAPbI3); in particular the VPb, PbI and IPb surface defects can introduce defect energy levels in the band gap. Tetrahexylammonium iodide (THAI) that is strongly adsorbed on the (1 0 0) surface of FAPbI3 by forming Pb-I coordination bonds and I⋯H hydrogen bonds could eliminate or reduce the defect states near the band edge or in the band gap by transferring electrons between THAI and the surface of FAPbI3. In particular, the defect states introduced by VPb could be completely eliminated after the adsorption of THAI. This study shows an in-depth understanding of the influence of defects on the electronic properties of the surface of FAPbI3, as well as the passivation mechanism of organic salts on the surface defects of perovskite.

Achieving a Cr6+-free Cr3+-activated spinel phosphor by a one-step solid-state reaction

Co-doping of Bi3+ into the spinel ZnAl2O4 reduces the density of anti-site defects and further inhibits the formation of the Cr(vi) impurity, leading to a Cr6+-free Cr3+-activated ZnAl2O4:Cr3+,Bi3+ phosphor.

First-principles calculation of intrinsic point defects and doping performance of MoSi<sub>2</sub>N<sub>4</sub>

MoSi<sub>2</sub>N<sub>4</sub> is an emergent two-dimensional (2D) material, which has received much attention because of its excellent performance over semiconductors, including excellent environmental stability and high carrier mobility. However, the formation of intrinsic defects in semiconductors is often inevitable and can significantly affect device performance. By using density functional theory (DFT), we analyze the properties and effects of intrinsic point defects in MoSi<sub>2</sub>N<sub>4</sub>. We first confirm the consistency of our results with current experimental data. After that, the formation energy values of twelve native defects reveal that the antisite defect of molybdenum substituting for silicon (Mo<sub>Si</sub>) defect dominates in all intrinsic defects. Under the constraint of overall charge neutrality, self-consistent Fermi level calculations reveal that MoSi<sub>2</sub>N<sub>4</sub> with only intrinsic defects exhibits intrinsic characteristics, highlighting its potential as a semiconductor device material. However, this intrinsic nature contradicts the p-type characteristics observed in two-dimensional MoSi<sub>2</sub>N<sub>4</sub>. In the subsequent defect concentrations, we find that both n-type and p-type behavior can be easily realized by doping appropriate impurities without being compensated by native defects. This suggests that the p-type characteristics of MoSi<sub>2</sub>N<sub>4</sub> during growth may result from p-type impurities introduced under non-equilibrium growth conditions or silicon vacancy defects. Our findings not only demonstrate the potential applications of MoSi<sub>2</sub>N<sub>4</sub> in semiconductor devices but also provide valuable guidance for future studying the defect mechanisms of this material.

Computational prediction of high thermoelectric performance in As2Se3 by engineering out-of-equilibrium defects.

We employed first-principles calculations to investigate the thermoelectric transport properties of the compound As2Se3. Early experiments and calculations have indicated that these properties are controlled by a kind of native defect called antisites. Our calculations using the linearized Boltzmann transport equation within the relaxation time approximation show good agreement with the experiments for defect concentrations of the order of 1019 cm-3. Based on our total energy calculations, we estimated the equilibrium concentration of antisite defects to be about 1014 cm-3. These results suggest that the large concentration of defects in the experiments is due to kinetic and/or off-stoichiometry effects and in principle it could be lowered, yielding relaxation times similar to those found in other chalcogenide compounds. In this case, for relaxation time higher than 10 fs, we obtained high thermoelectric figures of merit of 3 for the p-type material and 2 for the n-type one.

Engineering the passivation routes of perovskite films towards high performance solar cells.

Passivation treatment is an effective method to suppress various defects in perovskite solar cells (PSCs), such as cation vacancies, under-coordinated Pb2+ or I-, and Pb-I antisite defects. A thorough understanding of the diversified impacts of different defect passivation methods (DPMs) on the device performance will be beneficial for making wise DPM choices. Herein, we choose a hydrophobic Lewis acid tris(pentafluorophenyl)borane (BCF), which can dissolve in both the perovskite precursor and anti-solvent, as the passivation additive. BCF treatment can immobilize organic cations via forming hydrogen bonds. Three kinds of DPMs based on BCF are applied to modify perovskite films in this work. It is found that the best DPM with BCF dissolved in anti-solvent can not only passivate multiple defects in perovskite, but also inhibit δ phase perovskite and improve the stability of devices. Meanwhile, DPM with BCF dissolved in both the perovskite precursor and anti-solvent can cause cracks and voids in perovskite films and deteriorate device performance, which should be avoided in practical applications. As a result, PSCs based on optimal DPMs of BCF present an increased efficiency of 22.86% with negligible hysteresis as well as improved overall stability. This work indicates that the selection and optimization of DPMs have an equally important influence on the photovoltaic performance of PSCs as the selection of passivation additives.

Impact of Underlying Insulators on the Crystallinity and Antisite Defect Formation in PVD-MoS2 Films

Impact of Underlying Insulators on the Crystallinity and Antisite Defect Formation in PVD-MoS2 Films

The Effect of Point Defects on Young’s Modulus of the Off-Stoichiometric Al3X (X = Li, Sc, and Zr) Phases: A First-Principles Study

L12-Al3X (X = Li, Sc, and Zr) precipitates are the main strengthened phases of high-strength aluminum alloys and are critical for aerospace structural materials. Point defects and substitutional ternary elements change the mechanical properties of Al3X. In this paper, the effect of point defects, including vacancy, antisite, and substitutional element addition defects on the elastic modulus of the off-stoichiometric Al3X (X = Li, Sc, and Zr) phase were investigated by using first-principle calculations. The formation enthalpies of the defective Al3X alloy and isolated point defects in Al3X were calculated, and the results showed that the defects have an effect on the structure and elasticity of the off-stoichiometric Al3X phases. The lattice distortion, elastic constants, and elastic moduli were further investigated. It was found that the point defects increased the Young’s modulus for Al3Zr, and the doping of Er improved the Young’s modulus for off-stoichiometric Al3Li and Al3Sc. Adjusting the position of vacancies can improve the elastic modulus. In addition, the doping of substitutional elements (especially Sc, Ti, Zr, Hf, Ta, Mn, Ir, and Cf) can greatly increase the Young’s modulus of off-stoichiometric Al3Li.

Modeling of Crystal Structure in Li-Rich Layered Oxides for Rechargeable Lithium Cells

Lithium-Ion Batteries (LIBs) require further development in terms of safety and performance to establish also in the automotive market and new materials at both electrode sides as well as at the electrolyte side are necessary to overcome the state of-the-art and the commercial benchmarks. [1] The positive electrode materials constitute the bottleneck for present LIBs. They are based on layered structures (LiCoO2, NMC, NMA), spinel (LiMn2O4) and olivine LiFePO4, with rather moderate specific capacities (120–180 mAhg−1). [2] Therefore, the resulting specific energies are insufficient to meet market demand. Over-stoichiometric Li-rich layered oxides (LRLOs) are a family of positive electrode materials with promising theoretical electrochemical performance. [3] Indeed, they have received widespread attention due to their extremely high specific capacity (>250 mAhg−1) and low cost. Their extraordinary capacity has been confirmed to originate not only from the redox activities of transition metals, but also from the redox activities of oxygen anions. The crystal structure of LRLOs is an open playground of debate. There are two main hypotheses: a) a two phase nano-domain and b) a single phase solid solution. In this framework, the modeling of the crystal structure is quite challenging. Usually, the description of the structure of LRLOs can be done with rhombohedral or monoclinic unit cell. Nevertheless, the use of convention unit cells leads to a bad representation of the crystal structure because of the missing of structure features in the superstructure region (20<θ<30 in typical diffraction pattern with Cu Kα). In this communication, we demonstrate that extensive defectivities play a key role in the shape and intensity of diffractograms of LRLOs. In particular, we show how the use of supercells or defects (antisite defects and stacking faults) can help in the description of crystal structure of this class of materials.[1] Zubi, G.; Dufo-López, R.; Carvalho, M.; Pasaoglu, G. The Lithium-Ion Battery: State of the Art and Future Perspectives. Renewable and Sustainable Energy Reviews 2018, 89, 292–308.[2] Casas-Cabanas, M.; Ponrouch, A.; Palacín, M.R. Blended Positive Electrodes for Li-Ion Batteries: From Empiricism to Rational Design. Isr J Chem 2021, 61, 26–37.[3] Nie, L.; Chen, S.; Liu, W. Challenges and Strategies of Lithium-Rich Layered Oxides for Li-Ion Batteries. Nano Res 2022.

Antisite-Defects Control of Magnetic Properties in MnSb2Te4.

The intrinsic magnetic topological materials Mn(Sb/Bi)2n+2Te3n+4 have attracted extensive attention due to their topological quantum properties. Although, the Mn-Sb/Bi antisite defects have been frequently reported to exert significant influences on both magnetism and band topology, their formation mechanism and the methods to manipulate their distribution and concentration remain elusive. Here, we present MnSb2Te4 as a typical example and demonstrate that Mn-Sb antisite defects and magnetism can be tuned by controlling the crystal growth conditions. The cooling rate is identified as the primary key parameter. Magnetization and chemical analysis demonstrate that a slower cooling rate would lead to a higher Mn concentration, a higher magnetic transition temperature, and a higher saturation moment. Further analysis indicates that the Mn content at the original Mn site (MnMn, 3a site) varies more significantly with the cooling rate than the Mn content at the Sb site (MnSb, 6c site). Based on experimental observations, magnetic phase diagrams regarding MnMn and MnSb concentrations are constructed. With the assistance of first-principles calculations, it is demonstrated that the Mn-Sb mixing states primarily result from the mixing entropy and the growth kinetics. The present findings offer valuable insights into defects engineering for preparation of two-dimensional quantum materials.

Bound States of a Short-Range Defect on the Surface of an Intrinsic Antiferromagnetic Topological Insulator in a Noncollinear Phase

The features of electronic states on the surface of an intrinsic antiferromagnetic topological insulator (AFM TI) containing defects are theoretically investigated. Our approach takes into account the role of the electrostatic potential and the variation in the orientation of magnetic moments in the near-surface layers. A change in the spectral characteristics of the surface states under the transformation of magnetization from an equilibrium AFM phase of A-type to a ferromagnetic phase through a noncollinear texture is described. It is shown that in AFM TI with uniaxial anisotropy, an external magnetic field applied along the easy axis can cause a significant modulation of the exchange gap size in the spectrum of surface states and even invert the gap sign. Modeling the single defect effect as a surface potential perturbation over a finite scale, we analytically investigate the formation of a bound state and its behavior depending on the strength of potential and exchange scattering by the defect and the exchange gap size. The energy level of the bound state is demonstrated to experience a sharp shift in the vicinity of the spin-flop transition. The theoretical results obtained allow us to provide a consistent explanation of recent experimental data on scanning tunneling spectroscopy of antisite defects on the surface of the prototype AFM TI MnBi2Te4 in an external magnetic field.

Enhancement of the thermoelectric performance of half-metallic full-Heusler Mn2VAl alloys via antisite defect engineering and Si partial substitution

A half-metallic full-Heusler Mn2VAl alloy is a potential p-type thermoelectric material that can directly generate electricity from waste heat via the Seebeck effect. For practical use, the Seebeck coefficient S of Mn2VAl should be increased while maintaining a high electrical conductivity σ from its half-metallic character. Herein, we achieved this objective through antisite defect engineering. Theoretically, it was predicted that the S was maximized by regulating partial density of states of majority-spin sp-electrons through the control of the fraction of antisite defect, fAD, between V and Al atoms in Mn2VAl. Experimentally, a significant increase in S and a slight decrease in σ were observed for an Mn2VAl sample with an optimal fAD = 33%, enhancing the thermoelectric power factor PF by 2.7 times from an Mn2VAl sample with fAD = 14%. Furthermore, we combined the antisite defect engineering with a partial substitution method. An Mn2V(Al0.96Si0.04) sample with fAD = 33% exhibited the highest PF = 4.5 × 10−4 W·m−1·K−2 at 767 K among the samples. The maximum dimensionless figure-of-merit zT of the Mn2V(Al0.96Si0.04) sample with fAD = 33% was measured to be 3.4 × 10−2 at 767 K, which is the highest among the p-type half-metallic full-Heusler alloys.

Defect Synergistic Regulations of Li&Na Co-Doped Flexible Cu2 ZnSn(S,Se)4 Solar Cells Achieving over 10% Certified Efficiency.

Ion doping is an effective strategy for achieving high-performance flexible Cu2 ZnSn(S,Se)4 (CZTSSe) solar cells by defect regulations. Here, a Li&Na co-doped strategy is applied to synergistically regulate defects in CZTSSe bulks. The quality absorbers with the uniformly distributed Li and Na elements are obtained using the solution method, where the acetates (LiAc and NaAc) are as additives. The concentration of the harmful CuZn anti-site defects is decreased by 8.13% after Li incorporation, and that of the benign NaZn defects is increased by 36.91% after Na incorporation. Synergistic Li&Na co-doping enhances the carrier concentration and reduces the interfacial defects concentration by one order of magnitude. As a result, the flexible CZTSSe solar cell achieves a power conversion efficiency (PCE) of 10.53% with certified 10.12%. Because of the high PCE and the homogeneous property, the Li&Na co-doped device is fabricated to a large area (2.38 cm2 ) and obtains 9.41% PCE. The co-doping investigation to synergistically regulate defects provides a new perspective for efficient flexible CZTSSe solar cells.

A Multifunctional Amino Acid Enables Direct Recycling of Spent LiFePO4 Cathode Material.

Lithium iron phosphate (LiFePO4 , LFP) batteries are extensively used in electric vehicles and energy storage due to their good cycling stability and safety. However, the finite service life of lithium-ion batteries leads to significant amounts of retired LFP batteries, urgently required to be recycled by environmentally friendly and effective methods. Here, a direct regeneration strategy using natural and low-cost L-threonine as a multifunctional reductant is proposed. The hydroxyl groups and amino groups in L-threonine act as electron donors and nitrogen sources, respectively. The reductive environment created by L-threonine not only aids in converting the degraded FePO4 phase back to a single LFP phase but also facilitates the elimination of detrimental Li-Fe anti-site defects; thus, reconstructing fast Li+ diffusion channels. Meanwhile, N atoms derived from amino groups are able to dope into carbon layers, generating more active sites and enhancing the conductive properties of LFP particles. The regenerated LFP shows great electrochemical performance with a discharge capacity of 147.9 mAh g-1 at 1 C and a capacity retention of 86% after 500 cycles at 5 C. Further, this approach is also feasible for LFP black mass sourced from practical industrial dismantling lines, providing considerable prospects for the large-scale recycling of LFP batteries.

Engineering Vacancies for the Creation of Antisite Defects in Chemical Vapor Deposition Grown Monolayer MoS2 and WS2 via Proton Irradiation.

It is critical to understand the laws of quantum mechanics in transformative technologies for computation and quantum information science applications to enable the ongoing second quantum revolution calls. Recently, spin qubits based on point defects have gained great attention, since these qubits can be initiated, selectively controlled, and read out with high precision at ambient temperature. The major challenge in these systems is controllably generating multiqubit systems while properly coupling the defects. To address this issue, we began by tackling the engineering challenges these systems present and understanding the fundamentals of defects. In this regard, we controllably generate defects in MoS2 and WS2 monolayers and tune their physicochemical properties via proton irradiation. We quantitatively discovered that the proton energy could modulate the defects' density and nature; higher defect densities were seen with lower proton irradiation energies. Three distinct defect types were observed: vacancies, antisites, and adatoms. In particular, the creation and manipulation of antisite defects provides an alternative way to create and pattern spin qubits based on point defects. Our results demonstrate that altering the particle irradiation energy can regulate the formation of defects, which can be utilized to modify the properties of 2D materials and create reliable electronic devices.