Doping Modification Research Articles

A 3D printable and self‐healing polydimethylsiloxane elastomer

AbstractSilicone elastomers are broadly used in various fields because of their unique properties, such as flexibility, durable dielectric insulation, and excellent stability in hash environments. As a result, three‐dimensional (3D) printing of silicone elastomers is frequently required to construct personalized structures. However, existing 3D‐printing of silicone elastomers are less accurate, difficult to maintain shape, or require doping modification with thixotropic agents. Moreover, common 3D‐printable silicone elastomers do not have self‐healing capability, so they have to be discarded upon damaging. Herein, by introducing hydrogen bonds to improve the shape retention ability and induce network reversibility, we have developed a self‐healing polydimethylsiloxane elastomer, which can be readily 3D‐printed by fused deposition modeling (FDM) technology. We believe that this new silicone elastomer would be useful in the field of biomedical materials, flexible electronics, medical inserts, soft robots and so on.

Fluorescent Quantum Dots and Its Composites for Highly Sensitive Detection of Heavy Metal Ions and Pesticide Residues: A Review

Quantum dots nanomaterials have attracted extensive interest for fluorescence chemical sensors due their attributes, such as excellent optical characteristics, quantum size effects, interface effects, etc. Moreover, the fluorescence properties of quantum dots can be adjusted by changing their structure, size, morphology, composition, doping, and surface modification. In recent years, quantum dots nanomaterials have been considered the preferred sensing materials for the detection of heavy metal ions and pesticide residues by the interactions between quantum dots and various analytes, showing excellent sensitivity, selectivity, and interference, as well as reducing the cost of equipment compared with traditional measurement methods. In this review, the applications and sensing mechanisms of semiconductor quantum dots and carbon-based quantum dots are comprehensively discussed. The application of semiconductor quantum dots, carbon quantum dots, graphene quantum dots, and their nanocomposites that are utilized as fluorescence sensors are discussed in detailed, and the properties of various quantum dots for heavy metal ion and pesticide residue determination are also presented. The recent advances in and application perspectives regarding quantum dots and their composites are also summarized.

Enhanced thermoelectric performance of Sb-doped Mg2Si0.4Sn0.6via doping, alloying and nanoprecipitation

With the advantages of eco-friendliness, low cost, and low density, Mg2(Si,Sn) solid solutions are promising candidates for thermoelectric applications. In this work, Sb-doped Mg2Si0.4Sn0.6 bulks were prepared with a combined method of solid-state reaction and high pressure synthesis, followed by spark plasma sintering. Our investigations show that Sb doping optimizes the carrier concentration, while Si/Sn alloying effectively suppresses the lattice thermal conductivity and induces a convergence of the two lowest-lying conduction bands. Additionally, numerous coherent Sn-rich nanoprecipitates are formed within micron-sized grains. All these factors contribute synergistically to improving the thermoelectric properties of Mg2Si0.4Sn0.6. The optimal Mg2(Si0.4Sn0.6)0.985Sb0.015 exhibits a power factor higher than 4 000 μW·m−1·K−2 and a lattice thermal conductivity less than 0.8 W·m−1·K−1 at temperatures higher than 600 K, leading to the highest ZT of 1.61 at 823 K. Current work demonstrates an effective approach to enhancing the thermoelectric performance of n-type Mg2X solid solutions through doping, alloying, and microstructure modification.

Sulfuric acid-doped conjugated microporous poly(aniline)s enabled unconventional Hg (II) adsorption from aqueous solution

New strategies are required to modify adsorbents that possess numerous accessible chelating sites with high utilization, in order to achieve both rapid uptake and high capacity for the contaminants, which are still urgently needed. This study introduces a novel integration of a conjugated microporous polymer (CMP) material with conventional polyaniline, representing the first instance of such a combination. By amalgamating the doping properties of polyaniline with the highly stable structure and extensive microporous attributes of CMP, we achieve a synergistic effect. The conjugated microporous polyaniline is subjected to a concentrated sulfuric acid modification (SD-CMPA), enabling simultaneous oxidation, doping, and pore channel modification in a single step. The resulting SD-CMPA exhibits a record-breaking maximum adsorption capacity for Hg2+, reaching as high as 1720 mg·g−1, as well as a benchmark distribution coefficient of 2.5 × 108 mL·g−1. Moreover, it demonstrates robust reusability, retaining over 96% of its adsorption capacity for at least six cycles. These remarkable features enable the achievement of ultra-deep-water purification to 0.452 ppb in an effective manner. The impressive performance of SD-CMPA can be attributed to the abundance of nitrogen-containing groups, particularly the tertiary amine nitrogen in the material skeleton, as supported by X-ray photoelectron spectroscopy and density functional theory calculations. The results presented in this study demonstrate the exceptional potential of SD-CMPA for high-performance environmental remediation.

Transition metal modified manganese-based catalysts for soot oxidation promoted by noncompetitive adsorption of oxygen: Experiments and DFT calculations

A series of manganese-based oxide catalysts were synthesized by the hydrothermal method. By adjusting the doping amounts of W and Cu in the system to study the catalytic performance of transition metal-doped manganese oxides on soot combustion. They were deeply studied through various characterizations and theoretical calculations. The results show that W and Cu doping modifications can significantly improve the activity of manganese-based oxides in soot oxidation. W-Cu0.1/MnOx prepared by co-modification of W and Cu at 395 °C can convert 90% of soot into CO2. The multiple characterization results show that by adjusting the doping amount of copper and tungsten, the nano-flower-like morphology can be obtained and the crystal plane can be reconstructed, which is helpful to increase the specific surface area, Mn3+ content, and oxygen vacancy content. The theoretical calculation results show that the oxygen vacancy on the surface of the catalyst shows the ability to activate O2 and H2O, and they show non-competitive adsorption. In addition, W-Cu0.1/MnOx has a good application prospect in the catalytic oxidation of soot because of its excellent catalytic stability. This work provides a reference for the design and preparation of non-noble metal-based catalysts for the elimination of soot particles from diesel engine exhaust.

Photocatalytic Conversion of Methane: Current State of the Art, Challenges, and Future Perspectives.

With 28-34 times the greenhouse effect of CO2 over a 100-year period, methane is regarded as the second largest contributor to global warming. Reducing methane emissions is a necessary measure to limit global warming to below 1.5 °C. Photocatalytic conversion of methane is a promising approach to alleviate the atmospheric methane concentrations due to its low energy consumption and environmentally friendly characteristics. Meanwhile, this conversion process can produce valuable chemicals and liquid fuels such as CH3OH, CH3CH2OH, C2H6, and C2H4, cutting down the dependence of chemical production on crude oil. However, the development of photocatalysts with a high methane conversion efficiency and product selectivity remains challenging. In this review, we overview recent advances in semiconductor-based photocatalysts for methane conversion and present catalyst design strategies, including morphology control, heteroatom doping, facet engineering, and cocatalysts modification. To gain a comprehensive understanding of photocatalytic methane conversion, the conversion pathways and mechanisms in these systems are analyzed in detail. Moreover, the role of electron scavengers in methane conversion performance is briefly discussed. Subsequently, we summarize the anthropogenic methane emission scenarios on earth and discuss the application potential of photocatalytic methane conversion. Finally, challenges and future directions for photocatalytic methane conversion are presented.

Bi(Ⅲ) and Ce(Ⅳ) functionalized carbon nitride photocatalyst for antibiotic degradation: Synthesis, toxicity, and mechanism investigations

Graphite-phase carbon nitride (g-C3N4) has shown great potential for antibiotic wastewater treatment due to its unique electronic structure and corresponding to visible light. In this study, a series of Bi/Ce/g-C3N4 photocatalysts with different doping amount were developed by direct calcination method for Rhodamine B and sulfamethoxazole photocatalytic degradation. The experiment result shows that the photocatalytic performance of Bi/Ce/g-C3N4 catalysts were better than that of single component samples. Under the optimal experimental conditions, the degradation rates of RhB (20 min) and SMX (120 min) by 3Bi/Ce/g-C3N4 reached 98.3% and 70.5%, respectively. The theoretical calculation results of DFT show that after Bi and Ce doping modification, the band-gap width of g-C3N4 is reduced to 1.215 eV and carrier migration rate is greatly improved. The enhanced photocatalytic activity was mainly attributed to the capture of electrons after doping modification, which inhibition of photogenerated carriers recombination and reduced the gap width. The cyclic treatment experiment of sulfamethoxazole showed that Bi/Ce/g-C3N4 catalysts had good stability. Ecosar evaluation and leaching toxicity test showed that Bi/Ce/g-C3N4 can be safely used for wastewater treatment. This study provides a perfect strategy for modifying g-C3N4 and a new way to improve the photocatalytic performance.

X‐Ray‐Activated Long Afterglow Double‐Perovskite Scintillator for Detection and Extension Imaging

AbstractX‐ray flat‐panel detectors are widely used for nondestructive detection of internal information in medical radiography and industrial applications. However, a persisting challenge is the application of radiography on highly curved 3D objects to realize flexibility and information storage for the fabrication of flexible large‐area X‐ray detectors. This study demonstrates a halide‐based double perovskite Cs2Na0.9Ag0.1LuCl6:Dy3+ by a hydrothermal reaction. The as‐prepared crystals exhibit afterglow features through a co‐doping strategy of Dy3+ and Ag+ ions. The double perovskite material with doping modification exhibits excellent scintillation properties with high sensitivity, low detection limit, and high radiation stability. In addition, flexible scintillator detectors are fabricated with an area of 8.0 × 6.0 cm2 by the blade‐coating strategy, which has a high spatial resolution of 11.2 lp mm−1@MTF = 0.2. Based on the long afterglow properties, the Cs2Na0.9Ag0.1LuCl6:Dy3+ flexible film exhibits thermoluminescence after turning off the X‐ray, thereby having strong potential for X‐ray imaging of nonflat and irregular objects.

Defect-rich selenium doped graphitic carbon nitride for high-efficiency hydrogen evolution photocatalysis

Graphitic carbon nitride (g-C3N4) has been demonstrated as a promising non-metal material for photocatalytic hydrogen evolution (PHE), while its photocatalytic activity is greatly limited due to the narrow visible light response-ability and the intrinsic severe charge deep trapping and recombination effects. Herein, a co-functionalized g-C3N4 system by Se doping and nitrogen vacancies modification is developed through a Se vapor-assisted-chemical vapor deposition synthetic strategy. Advanced characterization results revealed that Se dopants promote the visible-light absorption ability of g-C3N4, while nitrogen defects-induced shallow trap states are constructive to improving charge separation/transportation efficiency by effectively retarding the detrimental charge deep trapping and recombination. As a result, the synergistic effect of the Se dopants and nitrogen defects leads to a highly efficient PHE performance of g-C3N4. The integrated engineering strategy and mechanism understanding provided in this work may offer new insights into developing other novel photocatalysts for various applications.

Synergistic role of Sb doping and surface modification in high performance ultrahigh-nickel layered oxides cathode materials

Before the ultrahigh-nickel LiNixCoyMnzO2 (NCM, x + y + z = 1, x ≥ 0.9) layered oxides are able to be used as a commercial electrode material for Li+ batteries, problems such as structural instability and capacity degradation due to repeated cycling need to be overcome. In this essay, we designed and prepared the Sb-modified LiNi0.92Co0.04Mn0.04O2 (Sb-NCM) materials, which simultaneously realize synergistic role of Sb doping and surface modification. The discharge capacity of the Sb-NCM materials is 206.0 mA h g−1 at 0.5 C between 2.7 V and 4.3 V. The capacity maintenance is 82.9 % after 125 cycles at 5 C, compared with 50.1 % of the pristine sample. It also demonstrates excellent rate performance, exhibiting the capacity at 5 C equal to 88.5 % at 0.1 C, while the pristine sample is only 83.7 %. According to the in situ X-ray diffractometer (XRD) test, the higher stability of Sb-NCM materials is mainly manifested in the strain mitigation induced by the absorption of anisotropic lattice shrinkage / extraction, which inhibits the formation of microcracks during charge-discharge test. Therefore, simultaneous Sb doping and Sb oxides coating layer are positive solution to stabilize layered structure and improve electrochemical properties.

Facet-Controlled Cu-doped and K-promoted Fe2O3 nanosheets for efficient CO2 hydrogenation to liquid hydrocarbons

Hydrogenation of CO2 into liquid hydrocarbons is an attractive route for chemical utilization of CO2, but suffers from limited product selectivity. By controlling the exposed surface atoms of metal catalyst, purposefully enhancing the reaction rate of bottleneck steps for CO2 activation and C-C coupling is expected to solve this problem. Here, we tuned the exposed surface atoms of catalysts separately and simultaneously by facet control, doping and promoter modification; a nanosheet-shaped Fe2O3 rich in oxygen vacancies was first constructed to enhance the adsorption and activation of CO2. Cu doping and K promoter were further used to promote the formation of active χ-Fe5C2 phase and facilitate the coupling of C-C bond to form long chain fuels. The optimized K-promoted and Cu-doped Fe2O3 nanosheets (3 K/6Cu-Fe-S) exhibited high CO2 conversion (46.5%) and C5+ hydrocarbons selectivity (53.6%), accompanied with low CO (5.3%) and CH4 selectivity (12.2%) at 300 °C, outperforming other reported Fe-based catalysts significantly. Meanwhile, a 205 h on stream test indicated the excellent stability of 3 K/6Cu-Fe-S. The effects of each tuning method on catalytic activity and product selectivity were further studied by combining the change of the phase and surface electronic structure of the catalyst before and after the reaction. Cu doping and K promoter were verified to have a synergistic enhancement effect on the hydrogenation performance of CO2, rather than just the sum of the two. These findings would be beneficial for the rational design of CO2 hydrogenation catalysts.

Simple Synchronous Dual-Modification Strategy with Zr4+ Doping and CeO2 Nanowelding to Stabilize Layered Ni-Rich Cathode Materials

A Ni-rich layered oxide, one promising cathode for lithium-ion batteries (LIBs), exhibits the advantages of low cost and high capacity but suffers from rapid capacity loss due to bulk structural instability and surface side reactions. Herein, a simple synchronous dual-modification strategy with Zr4+ doping and CeO2 nanowelding is proposed to address such issues. Utilizing the migration energy difference of Zr and Ce ions in layered structures, one-step high-temperature sintering of LiNi0.8Co0.1Mn0.1O2 particles with Zr and Ce nitrate distributions enables simultaneous doping of Zr ions in the bulk and CeO2 surface modification. Therein, Zr ions in the bulk occupying the Li sites can improve the Li+ diffusion rate and stabilize the crystal structure, while CeO2 on the surface provides nanowelding between the grain boundaries and resistance to electrolyte erosion. Theoretical calculations and a series of structure/composition characterizations (i.e., neutron scattering, in situ X-ray diffraction, etc.) validated the proposed strategy and its role in stabilizing the Ni-rich cathodes. The synergistic effect of Zr4+ doping and CeO2 nanowelding enables an impressive initial capacity of 187.2 mAh g–1 (2.7–4.3 V vs Li/Li+) with 86.1% retention after 200 cycles at 1 C and rate capabilities of 146.6 and 127.3 mAh g–1 at 5 and 10 C, respectively. Upon increasing the testing temperature to 60 °C, the dual-modified Ni-rich cathode exhibits an initial discharge capacity of 203.5 mAh g–1 with a good retention of 80.8% after 100 cycles at 0.5 C. The present strategy utilizing the migration energy difference of metal ions to achieve synchronous bulk doping and surface modification will offer fresh insights to stabilize layered cathode materials for LIBs, which can be widely used in other kinds of batteries with various cathode materials.

Sludge Biochar Modified by B-doped and Its Adsorption Behavior and Mechanism of 1,2-DCA in Water

Sludge biochar (BC600) and B-doped sludge biochar (BBC600) were prepared with the boric acid doping modified co-pyrolysis method using municipal sludge as precursors, and the materials were structurally characterized by SEM, BET, FTIR, and Zeta potential and static contact angle to investigate the adsorption behavior, mechanism of BC600 and BBC600 on 1,2-DCA in water, and the influencing factors. The results of structural characterization showed that the B element content, specific surface area, and pore volume of biochar increased by 76%, 48%, and 30%, respectively, after the B doping modification; the effect of B doping modification on the surface charge and hydrophobicity of biochar was not significant. The results of adsorption experiments showed that the adsorption of 1,2-DCA by BBC600 was better than that by BC600 due to the larger specific surface area and higher strength of oxygen-containing functional groups of BBC600; the pseudo-first-order kinetic equation could better describe the adsorption of 1,2-DCA by BC600, and the pseudo-second-order kinetic equation could better fit the adsorption of 1,2-DCA by BBC600. The intraparticle diffusion was not the only rate-limiting step affecting the adsorption rate; the biochar material was more dispersed and stable under alkaline conditions, and its oxygen-containing functional groups were deprotonated and had enhanced electron-donating ability, which was beneficial to the adsorption of 1,2-DCA. Humic acid (HA) showed a low concentration-promoting and high concentration-inhibiting effect on the adsorption of 1,2-DCA by BC600, whereas both low and high concentrations of HA showed an inhibitory effect on the adsorption of 1,2-DCA by BBC600. The adsorption of 1,2-DCA by BC600 was inhibited by both low and high concentrations of HA, and HA competed with 1,2-DCA for adsorption; Cl-, SO42-, and NO3- all inhibited the adsorption of 1,2-DCA by biochar, and the degree of inhibition ordered from small to large was Cl-<SO42-<NO3-. The main mechanisms of 1,2-DCA adsorption by biochar were pore filling and π-π interaction.

The high nano-domain improves the piezoelectric properties of KNN lead-free piezo-ceramics

Due to their high Curie temperature and large dielectric constant, potassium sodium niobate-based lead-free piezo-ceramics (KNN) are regarded as one of the most hopeful piezo-ceramics candidate materials. Herein, (1-x) (K0.5Na0.5)(Nb0.96Sb0.04)O3 - x (Ba0.5Sr0.25)ZrO3 [abbreviated as (1-x) KNNS - x BSZ, x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05] lead-free piezo-ceramics are prepared through chemical doping using the traditional solid phase method. The phase structure, domain structure, and microstructure of KNN ceramics have been thoroughly examined. Doping of BZS causes the formation of R-O-T phase boundaries and increases the proportion of polar nano-domains within the crystals, thus increasing the rate of motion of the domain walls and making the domains more easily deflected. The piezoelectric and dielectric properties of the material are improved simultaneously. When x = 0.04, the piezoelectric properties of ceramics reach the optimal value (d33 = 351 pC/N, TC = 305 °C, Kp = 43% and εr = 41267). This work offers a fresh concept for enhancing the overall performance of lead-free piezo-ceramics and aids in understanding the nature of doping modification of lead-free piezo-ceramics.

Construction of an La-BiVO4/O-Doped g-C3N4 Heterojunction Photocatalyst Embedded in Electrospinning Nanofibers

BiVO4 has been widely used in the field of photocatalysis due to its nontoxic and moderate band gap. However, single BiVO4 has the disadvantages of a high recombination rate of photogenerated carriers and weak response to visible light, inhibiting its photocatalytic applications. To explore viable solutions, a hybrid material composed of lanthanum-doped bismuth vanadate (La-BiVO4) and oxygen-doped porous graphite carbon nitride (O-doped g-C3N4), i.e., La-BiVO4/O-doped g-C3N4 powder, was prepared by a facile hydrothermal reaction and low-temperature calcination. Then, the powder was loaded on polyacrylonitrile nanofibers (NFs) through the electrospinning fiber technique. Various surface science characterizations, including transmission electron microscopy and nitrogen absorption and desorption analysis, confirmed the successful synthesis of a mesoporous heterojunction material. The La3+-doping as well as the porous morphologies and larger specific surface area of the O-doped g-C3N4 ultimately improve the photocatalytic abilities via a proposed Z-scheme heterojunction mechanism. The roles of La3+-doping and morphology modification in promoting the separation of the photogenerated carriers and broadening the optical absorption range were experimentally discussed. The RhB degradation experiment indicated that the La-BiVO4/O-doped g-C3N4 powder has excellent photocatalytic activity, which is about 2.85 and 2 times higher than that of the pure BiVO4 and O-doped g-C3N4, respectively. Meanwhile, the La-BiVO4/O-doped g-C3N4 NF shows good stability and recoverability after a 10-cycle testing. Such a hybrid photocatalyst with a proposed Z-scheme heterojunction mechanism and good plasticity might pave a feasible way to fabricate a new library of photocatalysts.

Noise Mitigation Strategies for Silicon-Based Active Neural Optrode

In recent years, optogenetic-based neural regulation technologies have attracted extensive attention. Among them, the active neural optrode integrated with optical stimulating micro-laser diode (LD)/light emitting diode (LED) and electrical recording microelectrodes presents significant advantages. However, the performance of the neural optrode is still hindered by high amplitude noises generated by micro-LD/LED and silicon substrate. A silicon optrode with heavy doped probes, LD coupled optical fiber and electrochemical modified microelectrodes is herein developed for low-noise and high-fidelity optical modulation. Firstly, the electromagnetic interference (EMI) free and high efficiency optical stimulation is realized by adopting optical coupling module with microfabricated locating slot. Secondly, the photovoltaic (PV) noise and the photo-electrochemical (PEC) noise are significantly decreased by an order of magnitude through combination of heavy doping and electrochemical modification of the optrode. More importantly, it is confirmed for the first time that the PV and PEC noise can be further reduced by an order of magnitude through LD driving pulse shaping. Lastly, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-vivo</i> acute recording experiments show that the light-induced photoelectric noise (<50 μV) has little influence on the firing rate (1.2 spikes/s) and signal to noise (SNR=4.9) of the recorded signals accompanied by optical stimulation. The results indicate that the developed noise mitigation strategies are promising for optogenetics based neural circuits research.

Advances in atomic oxygen resistant polyimide composite films

Polyimide (PI) film is an attractive space material used in low Earth orbit (LEO) environment, owing to its extraordinary thermal, chemical stability, flexibility, excellent mechanical and insulating properties. These superior properties and versatility make PI one of the indispensable materials ensure the normal operation of spacecraft, which are unparalleled by most other polymers. Hydrocarbon-based PI, however, cannot withstand the erosion of atomic oxygen (AO) in LEO. Up to now, many strategies including coating, matrix modification and structural design have been utilized to improve the AO resistance of PI film. This review summarizes the state-of-the-art works on the PI composite films with AO resistance, and discusses the advantages and disadvantages of different strategies for protecting PI matrix from AO erosion. First, we discuss the conventional coatings protection, which contains inorganic, organic and organic–inorganic coatings. Then, the focus is attached to improving the inherent anti-AO capacity of PI film through matrix modifications, such as intrinsic, blending and doping modification strategies. Finally, the structural design strategies including Janus structure and bioinspired microstructure are also discussed. Fundamental parameters of PI composite films, such as mass loss, erosion yield, as well as mechanical properties, are highlighted to evaluate their anti-AO ability. Inspired by investigations over the past decades, a roadmap is also carefully depicted for the future of AO-resistant PI composite films in fundamental research.

Enhanced protection of manganese-doped zinc molybdate with synergistic corrosion resistance effects

Zinc molybdate (ZM) materials modified with different elements have a variety of properties, and therefore the study of metal elements modification for improvement in corrosion protection of ZM can be meaningful in practical applications. Herein, the manganese-doped zinc molybdate (Mn-ZM) material with synergistic anticorrosion effects was prepared through a one-step hydrothermal method. The total impedance value of Mn-ZM coating has increased by 341.6 % and 415.2 % in comparison with that of the ZM coating and pure epoxy coating after immersion in 3.5 wt% NaCl solution for 72 h, showing the best corrosion protection performance. The synergistic corrosion protection effects of Mn-ZM material were based on the multiplayer passive films, the permeation retarding effect and the improvement of hydrophobic and dispersion properties, which could cooperate with each other to delay the electrochemical corrosion processes. Herein, this work provides a new reference for the further study in elemental doping modification of other inorganic anticorrosion materials in applications.

Suppressing the H2–H3 phase transition of LiNi0.90Co0.04Mn0.03Al0.03O2 cathodes via Ta doping towards improved electrochemical performance upon 4.5V

Nowadays, Ni-rich cathodes act as a strong contender for high performance lithium-ion batteries cathodes due to their high capacities. Rapid capacity degradation and poor rate performance at high working voltages hinder their commercialization. This study reports a strategy for Ta5+ doping modification in LiNi0.90Co0.04Mn0.03Al0.03O2 (NCMA) cathode via a solid-state route. This study confirmed that the introduction of strong Ta–O bond is beneficial to degrade H2–H3 phase transition during cycling. Subsequently, the polarization of electrodes and internal resistance have been alleviated since the H2–H3 phase transition of the Ta-doped NCMA cathode is suppressed, which eventually leads to a high cyclability. Moreover, it also confirmed that the diffusion of Li ions has been accelerated since the space of Li layer is enhanced. As a consequence, the Ta-NCMA cathode displays a high initial discharge capacity of 222.6 mA h·g−1 and outperforms the benchmarking cathodes in 100th capacity retention (from 43.7% to 91.8%) between 2.8 and 4.5 V. Besides, compared to pristine NCMA cathodes, the rate capability of Ta5+-doped NCMA cathodes cycling at 5C also increase from 112.2 mA h·g−1 to 167.2 mA h·g−1. Hence, Ta doped Ni-rich cathode should be a potential cathode to realize both high capacity and stability structure.

Enabling high ionic conductivity in yttrium-based lithium halide electrolytes by composition modulation for all-solid-state batteries

Chloride electrolytes have again become a focus of research in recent years due to the oxidative stability at high potential. Y-based chlorides such as Li3YCl6 have a considerable ionic conductivity of ∼10−4 S/cm. The ionic conductivity of a solid-state electrolyte (SSE) is closely related to its crystal structure. Low lithium concentration composition is beneficial for lithium-ion conduction structure. Due to the presence of more free octahedral sites, the crystal structure with Pnma space group has a better ion diffusion compared to the crystal structure with P-3m1 space group with hexagonal close-packed structure (hcp). In addition to this, the doping of cations with higher valence states results in more lithium vacancy compensation in the crystal structure, which is a significant modification to improve the ionic conductivity of the chloride. Herein, ab initio molecular dynamics (AIMD) simulations were performed to investigate the effects of the lithium-deficient state configuration and the cation Nb5+ doping modification on the ion conduction of LiaYClb solid-state electrolytes. The lithium-deficient state composition structure has shifted the material space group structure from P-3m1 to Pnma, which facilitates the diffusion of lithium ions. The Nb5+ doping has increased the chance of lithium ion co-diffusion and disordered the lithium ion sites near the Y(Nb) cation site, resulting in a lower ab-plane diffusion barrier and a significant improvement of lithium ion migration. A series of lithium-deficient state compositions and Nb-doped chlorides were synthesized. Li2.31Y0.98Nb0.02Cl5.31 is obtained by solid sintering preparation with an ionic conductivity close to 1.0 × 10−3 S/cm and high electrochemical stability. The full cell of Li2.31Y0.98Nb0.02Cl5.31 matched with bare LiCoO2 maintains stability for 100 cycles.