Structure and electrochemical performance modulation of a LiNi0.8Co0.1Mn0.1O2 cathode material by anion and cation co-doping for lithium ion batteries

Ni-rich layered transition metal oxides show great energy density but suffer poor thermal stability and inferior cycling performance, which limit their practical application. In this work, a minor content of Co and B were co-doped into the crystal of a Ni-rich cathode (LiNi_0.8Co_0.1Mn_0.1O₂) using cobalt acetate and boric acid as dopants. The results analyzed by XRD, TEM, XPS and SEM reveal that the modified sample shows a reduced energy barrier for Li⁺ insertion/extraction and alleviated Li⁺/Ni²⁺ cation mixing. With the doping of B and Co, corresponding enhanced cycle stability was achieved with a high capacity retention of 86.1% at 1.0C after 300 cycles in the range of 2.7 and 4.3 V at 25 °C, which obviously outperformed the pristine cathode (52.9%). When cycled after 300 cycles at 5C, the material exhibits significantly enhanced cycle stability with a capacity retention of 81.9%. This strategy for the enhancement of the electrochemical performance may provide some guiding significance for the practical application of high nickel content cathodes.

Ni-rich layered transition metal oxides show great energy density but suffer poor thermal stability and inferior cycling performance, which limit their practical application.     

3D web freestanding RuO2–Co3O4 nanowires on Ni foam as highly efficient cathode catalysts for Li–O2 batteries

The mechanism of Li–O₂ batteries is based on the reactions of lithium ions and oxygen, which hold a theoretical higher energy density of approximately 3500 W h kg⁻¹. In order to improve the practical specific capacity and cycling performance of Li–O₂ batteries, a catalytically active mechanically robust air cathode is required. In this work, we synthesized a freestanding catalytic cathode with RuO₂ decorated 3D web Co₃O₄ nanowires on nickel foam. When the specific capacity was limited at 500 mA h g⁻¹, the RuO₂–Co₃O₄/NiF had a stable cycling life of up to 122 times. The outstanding performance can be primarily attributed to the robust freestanding Co₃O₄ nanowires with RuO₂ loading. The unique 3D web nanowire structure provides a large surface for Li₂O₂ growth and RuO₂ nanoparticle loading, and the RuO₂ nanoparticles help to promote the round trip deposition and decomposition of Li₂O₂, therefore enhancing the cycling behavior. This result indicates the superiority of RuO₂–Co₃O₄/NiF as a freestanding highly efficient catalytic cathode for Li–O₂ batteries.

Freestanding RuO₂–Co₃O₄ nanowires on Ni foam were synthesized and applied as a cathode in Li–O₂ battery. This cathode can deliver a high capacity of 9620 mA h g⁻¹ and stable long-term operation exceeding 122 cycles at 100 mA g⁻¹.     

Role of Al-doping with different sites upon the structure and electrochemical performance of spherical LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries

Al-doped spinel LiNi_0.5Mn_1.5O₄ materials with different sites and contents were synthesized by rapid precipitation combined with hydrothermal treatment and calcination. The roles of Al on structural stability and electrochemical performance were studied by utilizing a series of techniques. XRD patterns indicated lower ion diffusion and no impure phased in doped samples. FT-IR and CV results reveal that Al-doped materials possess a Fd$\bar{3}$m space group with increased disorder and increasing amounts of Mn³⁺. SEM and TEM equipped with EDS were used to characterize the regular morphology accompanied by a complete crystal structure and homogeneous distribution of elements. The Al content at the Ni, Mn, and Ni/Mn sites was optimized to be 5%, 3% and 5% (in total), respectively. The cycling stability was considerably enhanced at an ambient temperature (25 °C) and high temperature (55 °C). A typical Al dual-doped sample at Ni/Mn sites with 5% content delivered a reversible capacity of 113.5 mA h g⁻¹ after 200 cycles at 0.5C. The discharge capacity at 5, 10 and 20C was 127.3, 125.5 and 123.1 mA h g⁻¹, respectively. The discharge capacity remained at 126 mA h g⁻¹ after 50 cycles (55 °C, 0.5C). Subsequent EIS and analytical results of the cycled electrode showed improved structural stability with a lower resistance, stable cathode/electrolyte interface, and reduced dissolution of Mn. These data further demonstrated the feasibility and reliability of preparing high-performance spinel LiNi_0.5Mn_1.5O₄ cathode materials by doping with a suitable amount of Al.

Al-doped spinel LiNi_0.5Mn_1.5O₄ materials with different sites and contents were synthesized by rapid precipitation combined with hydrothermal treatment and calcination.     

Influence of morphology of monolithic sulfur–poly(acrylonitrile) composites used as cathode materials in lithium–sulfur batteries on electrochemical performance

Solvent-induced phase separation (SIPS) and thermally-induced phase separation (TIPS) derived poly(acrylonitrile) (PAN) based monoliths with different morphology and specific surface area were prepared and thermally converted into monolithic sulfur–poly(acrylonitrile) (SPAN) materials for use as active cathode materials in lithium–sulfur batteries. During thermal processing, the macroscopic monolithic structure fully prevailed while significant changes in porosity were observed. Both the monomer content in the precursor PAN-based monoliths and the tortuosity of the final monolithic SPAN materials correlate with the electrochemical performance of the SPAN-based cathodes. Overall, percolation issues predominate. In percolating SPAN-based cathode materials, the specific capacity of the SPAN-based cells increases with decreasing tortuosity. All monolithic SPAN materials provided highly reversible and cycle stable cathodes reaching reversible discharge capacities up to 1330 mA h g_sulfur⁻¹ @ 0.25C, 900 mA h g_sulfur⁻¹ @ 2C and 420 mA h g_sulfur⁻¹ @ 8C.

Influence of SPAN-based cathode materials with a defined morphology on the electrochemical behavior of Li–S-cells.     

Comparison of electrochemical performance of LiNi1−xCoxO2 cathode materials synthesized from coated (1−x)Ni(OH)2@xCo(OH)2 and doped Ni1−xCox(OH)2 precursors

LiNi_1−xCo_xO₂ cathode materials were successfully synthesized from coated (1−x)Ni(OH)₂@xCo(OH)₂ and doped Ni_1−xCo_x(OH)₂ precursors, and the effects of the Co site and content in the precursor and final cathode material on the structure, morphology, and electrochemical performance of the cathodes were investigated using X-ray diffraction, scanning electron microscopy, and charge–discharge tests. The electrochemical performance of the materials prepared from the coated precursor was generally better than that of the materials prepared from the doped precursor. However, with increasing Co content, the performance difference gradually decreased. Among the as-prepared samples, the sample coated with 12 mol% Co delivered an excellent reversible capacity of 213.8 mA h g⁻¹ at 0.1C and the highest capacity retention of 88.5% after 100 cycles at 0.2C in the voltage range of 2.75–4.3 V. High-performance LiNi_1−xCo_xO₂ materials were successfully synthesized, and our findings clearly reveal the differences in the electrochemical properties of the materials prepared from the two different precursors with increasing Co content, thereby providing a valuable reference for the synthesis of high-performance Ni-rich layered cathode materials for Li-ion batteries.

The effects of Co site and content on electrochemical performance of LiNi_1−xCo_xO₂ cathodes materials were investigated.     

High performance sol–gel synthesized Ce0.9Sr0.1(Zr0.53Ti0.47)O4 sensing membrane for a solid-state pH sensor

In this paper, we developed a high-performance solid-state pH sensor using a Ce_0.9Sr_0.1(Zr_0.53Ti_0.47)O₄ (CSZT) membrane through a very simple sol–gel spin-coating process. The structural properties of the CSZT membrane are correlated with its sensing characteristics. The CSZT based EIS sensor exhibited a high pH sensitivity of 92.48 mV pH⁻¹, which is beyond the Nernst limit (59.4 mV pH⁻¹), and good reliability in terms of a low hysteresis voltage of 1 mV and a small drift rate of 0.15 mV h⁻¹. This behaviour is attributed to the incorporation of Sr in the CSZT sensing membrane, which promotes change in the Ce oxidation state from Ce⁴⁺ to Ce³⁺.

We developed a high-performance solid-state pH sensor using a Ce_0.9Sr_0.1(Zr_0.53Ti_0.47)O₄ (CSZT) membrane through a very simple sol–gel spin-coating process.     

Effectively enhanced structural stability and electrochemical properties of LiNi0.5Mn1.5O4 cathode materials via poly-(3,4-ethylenedioxythiophene)-in situ coated for high voltage Li-ion batteries

Spinel LiNi_0.5Mn_1.5O₄ shows promise as a potential candidate for Li-ion batteries due to its high energy density and high rate performance. However, LiNi_0.5Mn_1.5O₄ (LNMO) spinel oxides usually deliver poor cycle life because of the increasing impedance and gradually dissolving Mn resulting in the destruction of crystal structure. Here, a conductive polymer poly-(3,4-ethylenedioxythiophene) (PEDOT) surface modified strategy is introduced to settle the above challenges. The main purpose is to construct a uniform and dense shell film on the surface of LiNi_0.5Mn_1.5O₄ (Industrial Grade), which is prepared by a simple chemical in situ oxidative polymerization method. The Mn dissolving from the lattice during the long-term cycling is well inhibited as the polymer shell protects LiNi_0.5Mn_1.5O₄ from direct exposure to the highly active electrolyte. As expected, the 3 wt% poly-(3,4-ethylenedioxythiophene) coated sample reveals long cycle life with acceptable capacity of 114.5 mA h g⁻¹ and high capacity retention of 91.6% after 200 cycles, compared to 70.9 mA h g⁻¹ and 56.5%, respectively, for the bare LiNi_0.5Mn_1.5O₄ sample. Furthermore, the coated sample demonstrates a higher capacity of 110 mA h g⁻¹ and 63 mA h g⁻¹ at 5C and 10C rate respectively. The improved performance is believed to be attributed to the formation of high conductivity and stable interface structure between electrolyte and LNMO, which is beneficial to suppress the destruction of crystalline structure due to the Mn dissolution and undesired side-reaction between electrolyte and LiNi_0.5Mn_1.5O₄ in long cycle, and improve simultaneously the conductivity and interface stability of LiNi_0.5Mn_1.5O₄ for high voltage lithium-ion batteries.

PEDOT coating on LNMO surface effectively improves it''s the crystal structure stability and electrochemical properties.     

Structural,electrical, and multiferroic characteristics of lead-free multiferroic: Bi(Co0.5Ti0.5)O3–BiFeO3 solid solution

A solid solution of bismuth cobalt titanate [Bi(Co_0.5Ti_0.5)O₃] and bismuth ferrite (BiFeO₃) with a composition Bi(Co_0.40Ti_0.40Fe_0.20)O₃ (abbreviated as BCTF80/20) was synthesized via a cost effective solid-state technique. Phase identification and basic structural symmetry of the samples were determined by analyzing powder X-ray diffraction data. Field emission scanning electron micrograph (FE-SEM) and energy dispersive X-ray (EDX) spectra were analyzed to evaluate the micro-structural aspects (shape and size, distribution of grains) as well as a quantitative evaluation of the sample. The average crystallite (particle) and grain size were found to be ∼30 nm and ∼1–2 micron, respectively. The electrical parameters (dielectric constant, tangent loss, impedance, modulus, and conductivity) of as-synthesized material were obtained in a temperature range of 300 to 773 K and frequency range of 1 kHz and 1000 kHz. The strong correlation of microstructure (i.e., grains, grain boundary, etc.) and electrical parameters of this material were observed. The frequency dependence of electrical impedance and modulus exhibited a deviation from an ideal Debye-like relaxation process. The dependence of dielectric relaxation mechanism on frequency and temperature is discussed in detail. The field dependent polarization (P–E hysteresis loop) of BCTF80/20 exhibited an enhanced value of remnant polarization as compared to that of BiFeO₃ (referred as BFO). At room temperature (300 K), the magnetic hysteresis loop measurements also showed a significant improvement in the magnetization of BCTF80/20. Thus, based on these enhanced values of remnant polarization and magnetic parameters, we can assume that BCTF80/20 may be considered as a promising candidate for some new generations of electronic devices.

A solid solution of bismuth cobalt titanate [Bi(Co_0.5Ti_0.5)O₃] and bismuth ferrite (BiFeO₃) with a composition Bi(Co_0.40Ti_0.40Fe_0.20)O₃ (abbreviated as BCTF80/20) was synthesized via a cost effective solid-state technique.     

Peculiarities of the microwave properties of hard–soft functional composites SrTb0.01Tm0.01Fe11.98O19–AFe2O4 (A = Co,Ni, Zn,Cu, or Mn)

Herein, we investigated the correlation between the chemical composition, microstructure, and microwave properties of composites based on lightly Tb/Tm-doped Sr-hexaferrites (SrTb_0.01Tm_0.01Fe_11.98O₁₉) and spinel ferrites (AFe₂O₄, A = Co, Ni, Zn, Cu, or Mn), which were fabricated by a one-pot citrate sol–gel method. Powder XRD patterns of products confirmed the presence of pure hexaferrite and spinel phases. Microstructural analysis was performed based on SEM images. The average grain size for each phase in the prepared composites was calculated. Comprehensive investigations of dielectric properties (real (ε′) and imaginary parts (ε′′) of permittivity, dielectric loss tangent (tan(δ)), and AC conductivity) were performed in the 1–3 × 10⁶ Hz frequency range at 20–120 °C. Frequency dependency of microwave properties were investigated using the coaxial method in frequency range of 2–18 GHz. The non-linear behavior of the main microwave properties with a change in composition may be due to the influence of the soft magnetic phase. It was found that Mn- and Ni-spinel ferrites achieved the strongest electromagnetic absorption. This may be due to differences in the structures of the electron shell and the radii of the A-site ions in the spinel phase. It was discovered that the ionic polarization transformed into the dipole polarization.

Paper presents the correlation between the composition, microstructure, and microwave properties of composites based on Tb/Tm-doped Sr-hexaferrites and spinel ferrites (AFe₂O₄), which were fabricated by a one-pot citrate sol–gel method.     

Integrated Cr and S poisoning of a La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode for solid oxide fuel cells

Strontium segregation in a La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) electrode reacts with Cr and S in a solid oxide fuel cell (SOFC), which can cause cell performance deterioration. Integrated Cr and S poisoning for LSCF cathodes of SOFC was studied at 800 °C of 200 mA cm⁻² (cathodic) for 20 h. After polarization in Cr and S at 800 °C for 20 h, polarization and ohmic resistances for LSCF were 2.4 Ω cm² and 3.4 Ω cm², which were larger than those for LSCF electrodes after Cr deposition only and S deposition only, respectively. The results illustrated that Cr and S deposition occurred on the surface of LSCF, which could form SrCrO₄ and SrSO₄. Compared to Cr deposition only and S deposition only, integrated Cr and S deposition was unsystematic, and the degradation phenomenon of Cr and S poisoning was more severe. The integrated Cr and S deposition of the LSCF electrodes was induced via interactions among CrO, SO₂ and segregated SrO from LSCF.

Strontium segregation in a La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) electrode reacts with Cr and S in a solid oxide fuel cell (SOFC), which can cause cell performance deterioration.     

Structures and properties of Mg0.95Mn0.01TM0.04O (TM = Co,Ni, and Cu) nanoparticles synthesized by sol–gel auto combustion technique

The room temperature structural, optical and dielectric properties of Mg_0.95Mn_0.05O and Mg_0.95Mn_0.01TM_0.04O (TM = Co, Ni, and Cu) nanoparticles are reported. All transition metal nanocrystalline samples were successfully prepared by sol–gel auto combustion method. X-ray powder diffraction patterns at room temperature confirmed the formation of single-phase cubic structure with an Fm$\bar{3}$m space group for all prepared samples. Slight variation in the lattice parameter of TM doped Mg_0.95Mn_0.05O has been observed. Using Rietveld refinement of XRD data, the space group and lattice parameters are determined. Scanning electron microscopy (SEM) measurements were performed to understand the morphology and grain size of the Mg_0.95Mn_0.01TM_0.04O (TM = Co, Ni, and Cu) nanocrystals. The estimated band gaps as calculated by using UV-Vis spectroscopy are found to be 3.59, 3.61, 5.63 and 3.55 eV for Mg_0.95Mn_0.05O and Mg_0.95Mn_0.01TM_0.04O (TM = Co, Ni, and Cu) nanocrystals, respectively. Both dielectric constant and dielectric loss is found to decrease due to TM (transition metal) doping. The ac conductivity is found to increase with increase in frequency. Electric modulus spectra reflect the contributions from grain effects: the large resolved semicircle arc caused by the grain effect. The results obtained in this study were discussed comparatively with those cited in the literature.

The room temperature structural, optical and dielectric properties of Mg_0.95Mn_0.05O and Mg_0.95Mn_0.01TM_0.04O (TM = Co, Ni, and Cu) nanoparticles are reported.     

Synthesis and characterization of AFe2O4 (A: Ni,Co, Mg)–silica nanocomposites and their application for the removal of dibenzothiophene (DBT) by an adsorption process: kinetics,isotherms and experimental design

The kinetics, equilibrium, and statistical aspects of the sulfur removal process from hydrocarbon fuels by AFe₂O₄–silica nanocomposites (A: Ni, Mg, and Co) have been investigated in the present study. Nanocomposites were prepared via the auto-combustion sol–gel method and then employed in the adsorptive desulfurization (ADS) process. Next, the prepared samples were characterized by different analytical methods including XRD, SEM, TEM, FT-IR, TGA, and BET. The contributions of conventional parameters including adsorbent dosage and contact time were then studied by central composite design (CCD) under response surface methodology (RSM). Based on the statistical investigations, optimum conditions for ADS were an adsorbent dosage of 7.82 g per 50 ml of the model fuel and a contact time of 32 min. The adsorption amounts reached 38.6 mg g⁻¹ for DBT. The quadratic model was applied for the analysis of variance. Based on the experimental data, the pseudo-first-order (PFO) model could explain the adsorption kinetics of the compounds. Furthermore, the Langmuir isotherm demonstrated considerable agreement with the experimental equilibrium data. According to the results, the NiFe₂O₄–SiO₂ nanocomposite showed the best performance compared to other compounds. The sulfur removal efficiency increased from 63 to 94% upon increasing the NiFe₂O₄–SiO₂ dosage from 3 to 9 g per 50 ml of the model fuel.

Among the methods for adsorptive desulfurization (ADS) represents a promising alternative method of removing sulfur by adsorption.     

Correction: Synthesis and characterization of AFe2O4 (A: Ni,Co, Mg)–silica nanocomposites and their application for the removal of dibenzothiophene (DBT) by an adsorption process: kinetics,isotherms and experimental design

Correction for ‘Synthesis and characterization of AFe₂O₄ (A: Ni, Co, Mg)–silica nanocomposites and their application for the removal of dibenzothiophene (DBT) by an adsorption process: kinetics, isotherms and experimental design’ by Fahimeh Vafaee et al., RSC Adv., 2021, 11, 22661–22676, https://doi.org/10.1039/D1RA02780H.

The authors regret an error in Fig. 4 where a section of the XRD for 4(a) and (b) is identical.Open in a separate windowFig. 4(a) The XRD pattern of sample 3 after adsorption of DBT. (b) The XRD pattern of sample 3 before adsorption of DBT.The authors have repeated the experiment and provided new data for Fig. 4. An independent expert has viewed the new data and has concluded that it is consistent with the discussions and conclusions presented. The correct Fig. 4 is shown below:The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Recyclable MFe2O4 (M = Mn,Zn, Cu,Ni, Co) coupled micro–nano bubbles for simultaneous catalytic oxidation to remove NOx and SO2 in flue gas

NO_x can be efficiently removed by micro–nano bubbles coupling with Fe³⁺ and Mn²⁺, but the catalyst cannot be reused and the adsorption wastewater should be treated. This work developed a new technology that uses micro–nano bubbles and recyclable MFe₂O₄ to simultaneously remove NO_x and SO₂ from flue gas, and clarified the effectiveness and reaction mechanism. MFe₂O₄ (M = Mn, Zn, Cu, Ni and Co) prepared by a hydrothermal method was characterized. The results show that MFe₂O₄ can be activated to produce ˙OH which can accelerate the oxidation absorption of NO_x. Compared with no catalyst, the NO_x conversion rate increased from 32.85% to 83.88% in the NO_x–SO₂–MFe₂O₄-micro–nano bubble system, while the removal rate of SO₂ can reach 100% at room temperature. The catalytic activities of MFe₂O₄ showed the following trend: CuFe₂O₄ > ZnFe₂O₄ > MnFe₂O₄ > CoFe₂O₄ > NiFe₂O₄. The results provide a new idea for the application of advanced oxidation processes in flue gas treatment.

NO_x-SO₂-MFe₂O₄-micro–nano bubbles system for NO_x removal.     

Thermodynamics of the double sulfates Na2M2+(SO4)2·nH2O (M = Mg,Mn, Co,Ni, Cu,Zn, n = 2 or 4) of the blödite–kröhnkite family

The double sulfates with the general formula Na₂M²⁺(SO₄)₂·nH₂O (M = Mg, Mn, Co, Ni, Cu, Zn, n = 2 or 4) are being considered as materials for electrodes in sodium-based batteries or as precursors for such materials. These sulfates belong structurally to the blödite (n = 4) and kröhnkite (n = 2) family and the M cations considered in this work were Mg, Mn, Co, Ni, Cu, Zn. Using a combination of calorimetric methods, we have measured enthalpies of formation and entropies of these phases, calculated their Gibbs free energies (Δ_fG°) of formation and evaluated their stability with respect to Na₂SO₄, simple sulfates MSO₄·xH₂O, and liquid water, if appropriate. The Δ_fG° values (all data in kJ mol⁻¹) are: Na₂Ni(SO₄)₂·4H₂O: −3032.4 ± 1.9, Na₂Mg(SO₄)₂·4H₂O: −3432.3 ± 1.7, Na₂Co(SO₄)₂·4H₂O: −3034.4 ± 1.9, Na₂Zn(SO₄)₂·4H₂O: −3132.6 ± 1.9, Na₂Mn(SO₄)₂·2H₂O: −2727.3 ± 1.8. The data allow the stability of these phases to be assessed with respect to Na₂SO₄, MSO₄·mH₂O and H₂O(l). Na₂Ni(SO₄)₂·4H₂O is stable with respect to Na₂SO₄, NiSO₄ and H₂O(l) by a significant amount of ≈50 kJ mol⁻¹ whereas Na₂Mn(SO₄)₂·2H₂O is stable with respect to Na₂SO₄, MnSO₄ and H₂O(l) only by ≈25 kJ mol⁻¹. The values for the other blödite–kröhnkite phases lie in between. When considering the stability with respect to higher hydrates, the stability margin decreases; for example, Na₂Ni(SO₄)₂·4H₂O is still stable with respect to Na₂SO₄, NiSO₄·4H₂O and H₂O(l), but only by ≈20 kJ mol⁻¹. Among the phases studied and chemical reactions considered, the Na–Ni phase is the most stable one, and the Na–Mn, Na–Co, and Na–Cu phases show lower stability.

The double sulfates with the general formula Na₂M²⁺(SO₄)₂·nH₂O (M = Mg, Mn, Co, Ni, Cu, Zn, n = 2 or 4) are being considered as materials for electrodes in sodium-based batteries or as precursors for such materials.     

Comment on “Structural,electrical, and multiferroic characteristics of lead-free multiferroic: Bi(Co0.5Ti0.5)O3–BiFeO3 solid solution” by N. Kumar,A. Shukla,N. Kumar,R. Choudhary and A. Kumar,RSC Adv., 2018, 8, 36939”

My comments concern the significant errors in the crystallographic part of the commented paper. It was found that the studied crystal is of the sillenite type and the correct formula should be Bi₂₅FeO₃₉ : Co,Ti instead of BiFeO₃. Moreover, the type of unit cell is not correct. Due to the double doping the new type of unit cell, previously unknown, was proposed for such crystals. Furthermore, the authors did not find that the studied sample contains two slightly different phases, both of the sillenite type. The actual chemical composition of the studied crystals is not known.

The significant errors in the crystallographic part of the commented paper are described. The new chemical formula of the studied crystal is proposed: Bi₂₅FeO₃₉ : Co,Ti. The coexistence of two sillenite type phases is evidenced.