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To explore the influence of cation doping with cation radius variation on LiNi0.8Co0.1Mn0.1O2, a series of layered Li0.99M0.01Ni0.8Co0.1Mn0.1O2 (M-NCM, M=Ca, Sr, Ba) cathode materials were synthesized. Through density functional theory (DFT) calculations, all doped models have low band gaps and more relative electrons near the Fermi energy level than the pristine model. With increasing cation radius, the improvement in electronic conductivity diminishes. X-ray diffraction data and structural refinement results show that lattice parameters and lithium layer increase with increasing doping cation radius. The Ba-NCM sample, which has the largest radius, has the highest initial capacity (246.6 mAh·g−1) at 0.1 C. The Ca-NCM sample, with the least doping cation radius, has the highest capacity retention, which reaches to 90.06% after 100 cycles at 1 C. The Sr-NCM sample exhibits the highest remaining capacity, which could retain 146.5 mAh·g−1 at 5 C and 158.7 mAh·g−1 after 100 cycles at 1 C. This is attributed to the highest Li+ diffusion coefficient (8.49 × 10−11 cm2·s−1) and moderate electronic conductivity and radius of Sr2+. Doping Li sites in LiNi0.8Co0.1Mn0.1O2 with divalent cations of proper radius could be effectively improved the comprehensive electrochemical performance. This effect is based on not only the pillar effect and high electronic conductivity but also the trade-off between the expansion of lithium layer thickness and introduction of steric hindrance, as a consequence of the cations doping. [ABSTRACT FROM AUTHOR]

Summary: To improve the electrochemical performances of high voltage LiCoMnO4 spinel cathode material at 5.3 V, Cr doped LiCoMn1‐xCrxO4 (x = 0, 0.025, 0.050, 0.075) materials were synthesized by a one‐step solid‐state at 750°C. Rietveld refinement results showed that the phase purity of spinel is promoted with the increase in Cr concentration, which can be explained by the strong CrO bond that reduces oxygen deficiency and eliminates Li2MnO3 impurity phase during the synthesis process. Such change in phase purity further causes the improvement in specific capacity, and the 5.0%Cr doped sample displays the best result with a value of 123.0 mAh/g at 0.1°C and 93.3 mAh/g at 10°C. For a comparison, the pristine sample only releases a capacity of 112.6 mAh/g at 0.1°C and 54.8 mAh/g at 10°C. Improved capacity retention, from 83.1% to 90.1% after 100 cycles at 1°C, is also observed due to the suppressed volume change during the redox process after the incorporation of Cr cations in the lattice. Promoted rate performance, attributed from the improved Li ion diffusion coefficient, is also confirmed in the experiment. The improvement of those electrochemical properties could be explained by high‐phase purity and superior structural stability benefited from Cr‐doping. Novelty statement: LiCoMn1‐xCrxO4 (x = 0, 0.025, 0.050, 0.075) materials were synthesized by a one‐step solid‐state at 750°C, Chromium had been confirmed to reduce oxygen loss during LiCoMnO4 synthesis due to high oxygen affinity of Cr, which improves phase purity. As a result, the specific capacity was increased. Cr‐doping enhances the structural stability so that capacity retention was promoted due to higher bond energy of CrO than MnO; rate performance was also enhanced due to the improved diffusion coefficient. [ABSTRACT FROM AUTHOR]

Lithium-iron phosphate (LiFePO 4) monocrystalline platelets (LFP-P) with ac facet-preferred growing were obtained by a solvothermal method. Based on its anisotropy, a LiFePO 4 cathode (LFP-PM) with the b axis-oriented aligning was prepared by magnetic orientation. The structure, morphology and magnetic performance of the LFP-P were studied by X-ray diffractometry, scanning-electron microscopy, transmission-electron microscopy and superconducting quantum-interference device technologies. The LFP-P exhibited paramagnetic behavior and its b axis had the largest magnetic susceptibility, which made the LFP-P stack parallel to the magnetic field. It resulted in a higher lithium-ion diffusion coefficient of the LFP-PM (1.6855 × 10−11 cm2 s−1) compared with that of the LiFePO 4 cathode (LFP-PU) prepared without magnetic orientation (1.2538 × 10−11 cm2 s−1). The faster lithium-ion diffusion was contributed to a higher reversibility at 0.1 mV s−1 and higher discharge capacities of the LFP-PM at high rates ≥2 C. For the first time, LiFePO 4 monocrystalline platelets were made to align along b axis through magnetic orientation. It was proved to be an effective means of enhancing high rate performance. Unlabelled Image • LiFePO 4 monocrystalline platelets of ac facet preferred (LFP-P) were synthesized. • B axis oriented-aligning of LFP-P was carried out by magnetic orientation. • SQUID results showed that the LFP-PM had the most magnetic susceptibility. • The LFP-PM exhibited a 13.2% greater discharge capacity than LFP-PU at 10 C. • Magnetic orientation gave LFP-PM a higher D Li + (1.6855 × 10−11 cm2 s−1). [ABSTRACT FROM AUTHOR]

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 LiNi 0.90 Co 0.04 Mn 0.03 Al 0.03 O 2 (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. [ABSTRACT FROM AUTHOR]

Two different LiFePO 4 microplates grown in parallel with (010) and (001) lattice planes were obtained using a controllable hydrothermal process. The as-synthesized materials were characterized physically and electrochemically. XRD, SEM and HRTEM investigations confirmed the preferred growth and two corresponding growth mechanisms based on nucleation and recrystallization process were proposed. The calculation of Li ion diffusion coefficient along [001] and [010] directions using CV and EIS results revealed that (010) microplates have a higher diffusion coefficient than the (001) ones, implying a good electrochemical performance for (010) microplates over the (001) ones. Capacity tests confirmed the above assumption. Both the two cathode materials showed high specific capacities, and the (010) microplates exhibit a value around 158 mAh g −1 at a rate of 0.5C, showing a great advantage of (010) microplates for future application in LIBs for EV application. [ABSTRACT FROM AUTHOR]

Abstract: The electronic structures of a LiFePO4 (010) surface adsorbed with C are studied by a first-principles method based on DFT. The results show that the system is more stable when the LiFePO4 (010) surface is cut through Li atoms. PDOS analysis shows that the electronic structure of atoms in the sub-surface is similar to that of atoms in the bulk. The unpaired electrons in Fe-d orbital play a key role in the changes in the microelectronic structure; these changes lower the band gap and generate new bands that favor the transfer of electrons. Atom C reacts with Fe by chemisorptions when C is adsorbed on the outermost layer. Therefore, the materials may have better electrochemical properties by the improvement of diffusion of both electrons and Li ions when limiting the crystal growth with C coating. [Copyright &y& Elsevier]

Abstract: LiFePO4 has become a highly promising cathode material for use in the next generation of lithium-ion batteries, in which metal-doping is typically employed to improve the electrochemical properties. However, it is always difficult to resolve the issue that how the doping element and its position cause the microstructural changes and eventually influence the material properties. In this work, the X-ray diffraction (XRD) patterns of a series of metal-doped LiFePO4 were simulated by software MS Reflex to investigate those factors since XRD is a typical technique for the study of crystal structures. The effect of simulation conditions, doping position, and types of doping elements were discussed. The results revealed that: (1) the suitable step size should be 0.02° or less, and the simulation position had little influence on the XRD pattern; (2) the peak intensity changed with doping position, and had been affected more evidently at the Li-site compare with the Fe-site; (3) there was a close relationship between the doping elements and peak intensities in XRD patterns, and the variation degree of the peak intensity increased linearly with the atomic number of doping elements. [ABSTRACT FROM AUTHOR]

New anode materials (Co x /Li 3 Ti 4 Co 1−x CrO 12 ) had been successfully prepared via a high temperature solid-state method. Pure phase Co-Cr replaced solid solution (Li 3 Ti 4 CoCrO 12 ) was obtained by calcinating the precursor under air atmosphere while the Co modified solid solutions (Co x /Li 3 Ti 4 Co 1−x CrO 12 ) were prepared under a reducing atmosphere. Various methods, such as XRD, SEM, EDX mapping, cyclic testing, EIS, CV, XPS and EPR were employed to characterize the powder samples and investigate their electrochemical behavior. SEM results showed spherical shape of the products with nano sized primary crystals. EDX mapping further confirmed the different existence of the Co element, uniform distribution of Co 2+ ions within the spinel lattice and separated metallic Co on the particle surface. Cyclic tests revealed that the Co modified samples showed great promotion in their electrochemical performance. For the sample with x = 0.1, the best results with an initial capacity of 157.6 mA h/g and a capacity retention of 96.4% after 100 runs were observed. Such promotion can be explained by the improved electronic conductivity and enhanced Li + diffusion coefficient confirmed by the EIS and CV simulation, which was caused by the oxygen vacancy produced during the calcination under the reducing atmosphere. [ABSTRACT FROM AUTHOR]

This study presents a novel modification strategy involving the replacement of Mn with Sc in the cathode of NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM). The results of this study confirmed that Sc doping introduced strong Sc–O bonds to enhance the bonding between transition metal ions and O2−. Additionally, Sc doping reduced the proportion Mn3+ in the material (from 50.23% to 47.46%), thereby inhibiting the material structural distortion due to the Jahn–Teller effect induced by Mn3+. These factors were the main contributors to the improved cycling performance of the modified material. Furthermore, the introduction of Sc decreased the band gap of the material (1.7416–1.6706 eV) and the Na+ activation barrier energy (0.773–0.732 eV). These changes not noly facilitated the de-embedding of Na+ in the material lattice but also significantly enhanced the material electronic conductivity, leading to an excellent rate performance of the modified material. These results indicate that the NFM-Sc0.01 sample maintained an ultra-high capacity retention of 86.45% after 200 cycles at 1 C. At 5 C, the discharge capacity of NFM-Sc0.01 significantly increased from 79.3 mAh g−1 in NFM to 93.4 mAh g−1, demonstrating great potential for industrialized applications. • Sc3+ of stronger Sc-O binding energy was used to partally replace Mn in NFM. • Sc doping can inhibit NFM structural distortion caused by the Jahn-Teller effect. • Sc doping reduced the Na+ activation barrier energy from 0.773 to 0.732 eV. • The discharge capacity of NFM-Sc0.01 at 5 C was enhanced to 93.4 mAh g−1. [ABSTRACT FROM AUTHOR]

A new compound Li 3 Ti 4 CoCrO 12 , used as an anodic material for LIBs, was successfully prepared by nano-milling enhanced solid-state reaction method. Retrieved refinement of the X-ray diffraction (XRD) profile indicated that the material crystallizes in an ordinary Fd-3m lattice space group in which the substituted ions Co2+ and Cr3+ occupy the original Li+ and Ti4+ lattice positions, respectively. Upon cyclic voltammetry (CV) measurement, the sample showed a pair of redox process peaking at 1.44 V/1.53 V, implying that only Ti3+/Ti4+ redox pair was involved in the electrochemical process. Electrochemical impedance spectroscopy (EIS) test suggested that both the low interfacial resistance (8.56Ω) and the high Li ion diffusion (9.86 × 10−10 cm2·S−1), caused by the mesoporous nature of the anode powder, could be regarded as the important factors for the outstanding electrochemical behavior of the new anode material. The results imply that the synthesized compound Li 3 Ti 4 CoCrO 12 has high potential for the application in lithium secondary batteries. (a) Crystal structure of Li 3 Ti 4 CoCrO 12 build on software Ball & Stick., (b) Electrochemical behavior of Li 3 Ti 4 CoCrO 12 material cycling performance, (c) Electrochemical behavior of Li 3 Ti 4 CoCrO 12 material rate performance. Image 1 • A new spinel compound Li 3 Ti 4 CoCrO 12 was synthesized to serve as anode material. • Co2+ and Cr3+ occupy the lattice positions of the original Li+ and Ti4+ cations. • The material displayed excellent electrochemical performance for LIB application. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Si x Sb immiscible alloy was synthesized by chemical reduction-mechanical alloying methods. [•] The Si0.8Sb anodes exhibit the best electrochemical and cycle performances. [•] The volume expansion can be whittled by making lithiation products buffering matrices for each other. [•] The lithiation and delithiation reaction mechanism are investigated. [ABSTRACT FROM AUTHOR]

Abstract: Co3O4/MWCNTs composites have been synthesized by a simple hydrothermal method using a surfactant (CTAB) and a precipitation agent (urea). The samples were characterized by XRD, SEM and BET methods. The electrochemical properties of the samples as anode materials for lithium batteries were studied by EIS and Galvanostatic measurements. The Co3O4/MWCNTs composites displayed higher capacity and better cycle performance in comparison with the Co3O4 nanosheets. The remarkable improvement of electrochemical performance within the hybrid composites is probably related to the addition of MWCNTs that possesses improved properties such as excellent electric conductivity and large surface area, which helps to alleviate the effect of volume change, shorten the distance of lithium ion diffusion, facilitate the transmission of electron and keep the structure stable. [Copyright &y& Elsevier]

Cu-doped lithium-rich Li 1.27 Cr 0.2 Mn 0.53-x Cu x O 2 cathode materials were synthesized by a solid phase reaction. The X-ray diffraction (XRD) investigation showed that the doped Cu cations were incorporated into the hexagonal lattice, and that no impurity phase was generated. Scanning electron microscopy (SEM) observation also implied that the crystal growth was suppressed when Cu ions were introduced. Further investigation with Electron spin resonance (ESR) confirmed that oxygen vacancies were generated due to the non-equal valence substitution of Cu in the transition metal slab. The vacancy containing Li 1.27 Cr 0.2 Mn 0.50 Cu 0.03 O 2 material showed the best results, with an initial discharge capacity of 230.6 mAh·g−1, and a capacity retention of 91.8% after 100 cycles. When compared to the data of the pristine sample without Cu doping, obvious improvements of 22% and 7.4% were confirmed. Such improvement can be ascribed to the higher electronic conductivity (1.761 × 10−7 S cm−1 vs 3.51 × 10−8 S cm−1), and faster Li ion diffusion (1.081 × 10−10 cm2 s−1 vs 2.423 × 10−11 cm2 s−1), caused by the existence of the oxygen vacancies. The excellent electrochemical behavior of the materials prepared by our approach, shows their high potential for future application in the lithium ion battery (LIB) field. [ABSTRACT FROM AUTHOR]