Sn-doped Li<Subscript>1.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>O<Subscript>2</Subscript> cathode materials for lithium-ion batteries with enhanced electrochemical performance

Sn-doped Li-rich layered oxides of Li_1.2Mn_0.54-x Ni_0.13Co_0.13Sn _x O₂ have been synthesized via a sol-gel method, and their microstructure and electrochemical performance have been studied. The addition of Sn⁴⁺ ions has no distinct influence on the crystal structure of the materials. After doped with an appropriate amount of Sn⁴⁺, the electrochemical performance of Li_1.2Mn_0.54-x Ni_0.13Co_0.13Sn _x O₂ cathode materials is significantly enhanced. The optimal electrochemical performance is obtained at x = 0.01. The Li_1.2Mn_0.53Ni_0.13Co_0.13Sn_0.01O₂ electrode delivers a high initial discharge capacity of 268.9 mAh g^?1 with an initial coulombic efficiency of 76.5% and a reversible capacity of 199.8 mAh g^?1 at 0.1 C with capacity retention of 75.2% after 100 cycles. In addition, the Li_1.2Mn_0.53Ni_0.13Co_0.13Sn_0.01O₂ electrode exhibits the superior rate capability with discharge capacities of 239.8, 198.6, 164.4, 133.4, and 88.8 mAh g^?1 at 0.2, 0.5, 1, 2, and 5 C, respectively, which are much higher than those of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (196.2, 153.5, 117.5, 92.7, and 43.8 mAh g^?1 at 0.2, 0.5, 1, 2, and 5 C, respectively). The substitution of Sn⁴⁺ for Mn⁴⁺ enlarges the Li⁺ diffusion channels due to its larger ionic radius compared to Mn⁴⁺ and enhances the structural stability of Li-rich oxides, leading to the improved electrochemical performance in the Sn-doped Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode materials.     

Improving rate performance of cathode material Li<Subscript>1.2</Subscript>Mn<Subscript>0.54</Subscript>Co<Subscript>0.13</Subscript>Ni<Subscript>0.13</Subscript>O<Subscript>2</Subscript> via niobium doping

As a promising Li-ion battery cathode active material, lithium-rich manganese-based layer-structured oxides suffer from inferior cycle performance and poor rate capability. Herein, Nb-doped Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ is prepared by a sol-gel method, and the effects of Nb doping on its electrochemical performance are investigated. It is concluded that the Nb-doped Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, has a good layered structure along c-axis independent on the amount of Nb dopant and little cationic mixing. Nb doping for Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ has no obvious influence on its morphology. It is found that Nb doping can enhance the electrochemical activity of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, such as improved rate performance and cycle performance under high rate conditions. Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ doped with 0.015 Nb shows the best cycle performance under the high rate with the capacity maintenance of 95.4% after 100 cycles under 5 C rate, which is higher than that of the undoped one by 10.5%.

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Graphical abstract Rate performance of Li_1.2Mn_0.54-xCo_0.13Ni_0.13Nb _x O₂ materials

     

Effect of the Synthesis Method on the Functional Properties of Lithium-Rich Complex Oxides Li<Subscript>1.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>O<Subscript>2</Subscript>

Layered Li-rich transition metal oxides are considered among the most promising cathode materials for high energy density lithium-ion batteries. It was studied how the method and conditions of synthesis of Li-rich oxides Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ affect their electrochemical properties. Coprecipitation methods and modified Pechini process were used. It was shown that it is necessary to carefully choose the synthesis conditions when using the modified Pechini method because of their significant effect on the morphology of Li-rich oxides. Samples were obtained with high electrochemical characteristics: capacity discharge of 260–270 mAh/g (16 mA/g) and 60–70 mAh/g (988 mA/g) within the voltage range of 2.5–4.8 V.     

Synthesis and electrochemical performance of the Li-rich cathode material Li<Subscript>1.17</Subscript>Ni<Subscript>0.12</Subscript>Co<Subscript>0.13</Subscript>Mn<Subscript>0.58</Subscript>O<Subscript>2</Subscript> for lithium-ion batteries

Lithium-riched cathode material for lithium-ion batteries, Li_1.17Ni_0.12Co_0.13Mn_0.58O₂, was synthesized via crystallization from a solution of metal acetates, followed by a thermal treatment of the material obtained as a powder. The phase, elemental, and granulometric compositions of the material were examined, as well as the morphology of the powder particles obtained. The discharge capacity of the material in relation to the charging voltage was found from the results of electrochemical tests, and endurance tests were performed. The discharge capacity upon 85 charge/discharge cycles at voltages in the range 2.8–4.8 and a current of 0.1C was about 180 mA h g^–1.     

Ammonium tungstate modified Li-rich Li<Subscript>1+x</Subscript>Ni<Subscript>0.35</Subscript>Co<Subscript>0.35</Subscript>Mn<Subscript>0.30</Subscript>O<Subscript>2</Subscript> to improve rate capability and productivity of lithium-ion batteries

LiNi_1-x-yCo_xMn_yO₂ (NCM) with excessive lithium is known to exhibit high rate capability and charge–discharge cycling durability. However, the practical usage of NCM is difficult, because the positive electrode slurry is unstable and battery cells swell due to the alkaline residual lithium compound generated on the surface of NCM particles. To reduce the residual lithium compound, ammonium metatungstate (AMT) added to NCM is studied, and the effect is investigated by scanning electron microscopy, aberration-corrected scanning transmission electron microscopy, X-ray diffractometry, synchrotron X-ray diffractometry, and several electrochemical measurements. It is found that the AMT modification reduces the amount of alkaline residual lithium compound and improves the rate capability due to the ~1-nm-thick W-rich layer generated on the NCM surface.

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Graphical abstract ?

     

Facile synthesis of hollow Ti<Subscript>2</Subscript>Nb<Subscript>10</Subscript>O<Subscript>29</Subscript> microspheres for high-rate anode of Li-ion batteries

Titanium niobium oxides emerge as promising anode materials with potential for applications in lithium ion batteries with high safety and high energy density. However, the innate low electronic conductivity of such a composite oxide seriously limits its practical capacity, which becomes a serious concern especially when a high rate charge/discharge capability is expected. Here, using a modified template-assisted synthesis protocol, which features an in-situ entrapment of both titanium and niobium species during the formation of polymeric microsphere followed by a pyrolysis process, we succeed in preparing hollow microspheres of titanium niobium oxide with high efficiency in structural control. When used as an anode material, the structurally-controlled hollow sample delivers high reversible capacity (103.7 mA h g^?1 at 50 C) and extraordinary cycling capability especially at high charge/discharge currents (164.7 mA h g^?1 after 500 cycles at 10 C).     

Layered LiNi<Subscript>0.80</Subscript>Co<Subscript>0.15</Subscript>Al<Subscript>0.05</Subscript>O<Subscript>2</Subscript> as cathode material for hybrid Li<Superscript>+</Superscript>/Na<Superscript>+</Superscript> batteries

LiNi_0.80Co_0.15Al_0.05O₂ (NCA) is explored to be applied in a hybrid Li⁺/Na⁺ battery for the first time. The cell is constructed with NCA as the positive electrode, sodium metal as the negative electrode, and 1 M NaClO₄ solution as the electrolyte. It is found that during electrochemical cycling both Na⁺ and Li⁺ ions are reversibly intercalated into/de-intercalated from NCA crystal lattice. The detailed electrochemical process is systematically investigated by inductively coupled plasma-optical emission spectrometry, ex situ X-ray diffraction, scanning electron microscopy, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy. The NCA cathode can deliver initially a high capacity up to 174 mAh g^?1 and 95% coulombic efficiency under 0.1 C (1 C?=?120 mA g^?1) current rate between 1.5–4.1 V. It also shows excellent rate capability that reaches 92 mAh g^?1 at 10 C. Furthermore, this hybrid battery displays superior long-term cycle life with a capacity retention of 81% after 300 cycles in the voltage range from 2.0 to 4.0 V, offering a promising application in energy storage.     

Synthesis and electrochemical properties of Li-rich Li[Ni<Subscript>0.5</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.3</Subscript>]O<Subscript>2</Subscript> for pouch-typed cell

Layered transition metal oxide LiNi _x Co _y MnzO₂ cathode materials with different Li amount were successfully synthesized via co-precipitation method. Monodispersed Li[Ni_0.5Co_0.2Mn_0.3]O₂ and Li-rich Li_1.1[Ni_0.5Co_0.2Mn_0.3]O₂ spherical agglomeration consisted of secondary particles, which is favorable for the higher tap-density of materials, can be easily obtained. The pouch-typed cells with obtained materials were assembled to investigate electrochemical performance at level of full-cell. The results show that the assembled pouch-typed full-cells with Li-rich sample present higher capacity, better rate capability and cycle life.     

Al,B, and F doped LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> as cathode material of lithium-ion batteries

A series of the mixed transition metal compounds, Li[(Ni_1/3Co_1/3Mn_1/3)_1–x-y Al _x B _y ]O_2-z F _z (x = 0, 0.02, y = 0, 0.02, z = 0, 0.02), were synthesized via coprecipitation followed by a high-temperature heat-treatment. XRD patterns revealed that this material has a typical α-NaFeO₂ type layered structure with R3^- m space group. Rietveld refinement explained that cation mixing within the Li(Ni_1/3Co_1/3Mn_1/3)O₂ could be absolutely diminished by Al-doping. Al, B and F doped compounds showed both improved physical and electrochemical properties, high tap-density, and delivered a reversible capacity of 190 mAh/g with excellent capacity retention even when the electrodes were cycled between 3.0 and 4.7 V.     

Rational design of double-confined Mn<Subscript>2</Subscript>O<Subscript>3</Subscript>/S@Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocube cathodes for lithium-sulfur batteries

Due to the high specific capacities and environmental benignity, lithium-sulfur (Li-S) batteries have shown fascinating potential to replace the currently dominant Li-ion batteries to power portable electronics and electric vehicles. However, the shuttling effect caused by the dissolution of polysulfides seriously degrades their electrochemical performance. In this paper, Mn₂O₃ microcubes are fabricated to serve as the sulfur host, on top of which Al₂O₃ layers of 2 nm in thickness are deposited via atomic layer deposition (ALD) to form Mn₂O₃/S (MOS) @Al₂O₃ composite electrodes. The MOS@Al₂O₃ electrode delivers an excellent initial capacity of 1012.1 mAh g^?1 and a capacity retention of 78.6% after 200 cycles at 0.5 C, and its coulombic efficiency reaches nearly 99%, giving rise to much better performance than the neat MOS electrode. These findings demonstrate the double confinement effect of the composite electrode in that both the porous Mn₂O₃ structure and the atomic Al₂O₃ layer serve as the spacious host and the protection layer of sulfur active materials, respectively, for significantly improved electrochemical performance of the Li-S battery.     

Highly porous disk-like shape of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> as an anode material for lithium ion batteries

A novel disk-like shape of Co₃O₄ with high porosity was synthesized by a facile hydrothermal approach followed by calcination at 485 °C for 2 h. In order to further confirm the crystal structure, morphology, particle size, surface area, and porosity of the sample, a series of corresponding characterization techniques were used. The disk-like shape of Co₃O₄ as an anode delivered excellent rate capability such as 510.5 mAh g^?1 at 4.0 C, which is much higher than the theoretical capacity of commercial graphite anode (372 mAh g^?1). However, the electrode could not recover the high capacity during the long-term cycling at various higher current rates due to the deformation of the structure as confirmed by the ex situ studies. It is believed that the obtained remarkable structural feature with numerous void pores within the structure may be helpful for short-term cycling due to the large contact areas between the electrode and the electrolyte and a shorter diffusion length for lithium ion insertion but unable to act as a buffer to relax the volume expansion/contraction and alleviate the structural damage of the electrode during long-term cycling.     

Preparation and electrochemical performance of nano-structured Li<Subscript>2</Subscript>Mn<Subscript>4</Subscript>O<Subscript>9</Subscript> for supercapacitor

Nano-structured spinel Li₂Mn₄O₉ powder was prepared via a combustion method with hydrated lithium acetate (LiAc·2H₂O), manganese acetate (MnAc₂·4H₂O), and oxalic acid (C₂H₂O₄·2H₂O) as raw materials, followed by calcination of the precursor at 300 °C. The sample was characterized by X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectroscopy techniques. Electrochemical performance of the nano-Li₂Mn₄O₉ material was studied using cyclic voltammetry, ac impedance, and galvanostatic charge/discharge methods in 2 mol L⁻¹ LiNO₃ aqueous electrolyte. The results indicated that the nano-Li₂Mn₄O₉ material exhibited excellent electrochemical performance in terms of specific capacity, cycle life, and charge/discharge stability, as evidenced by the charge/discharge results. For example, specific capacitance of the single Li₂Mn₄O₉ electrode reached 407 F g⁻¹ at the scan rates of 5 mV s⁻¹. The capacitor, which is composed of activated carbon negative electrode and Li₂Mn₄O₉ positive electrode, also exhibits an excellent cycling performance in potential range of 0–1.6 V and keeps over 98% of the maximum capacitance even after 4,000 cycles.     

Correlation between the structural,electrical and electrochemical performance of layered Li(Ni<Subscript>0.33</Subscript>Co<Subscript>0.33</Subscript>Mn<Subscript>0.33</Subscript>)O<Subscript>2</Subscript> for lithium ion battery

The Li(Ni_0.33Co_0.33Mn_0.33)O₂ (LNCMO) cathode material is prepared by poly(vinyl pyrrolidone) (PVP)-assisted sol-gel/hydrothermal and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly (ethylene glycol) (Pluronic-P123)-assisted hydrothermal methods. The compound prepared by PVP-assisted hydrothermal method shows a comparatively higher electrical conductivity of ~2?×?10^?5 S cm^?1 and exhibits a discharge capacity of 152 mAh g^?1 in the voltage range of 2.5 to 4.4 V, for a C-rate of 0.2 C, whereas the compounds prepared by P123-assisted hydrothermal method and PVP-assisted sol-gel method show a total electrical conductivity in the order of 10^?6 S cm^?1 and result in poor electrochemical performance. The structural and electrical properties of LNCMO (active material) and its electrochemical performance are correlated. The difference in percentage of ionic and electronic conductivity contribution to the total electrical conductivity is compared by transference number studies. The cation disorder is found to be the limiting factor for the lithium ion diffusion as determined from ionic conductivity values.     

Facile synthesis of Fe@Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> core-shell nanowires as O<Subscript>2</Subscript> electrode for high-energy Li-O<Subscript>2</Subscript> batteries

Fe@Fe₂O₃ core-shell nanowires were synthesized via the reduction of Fe³⁺ ions by sodium borohydride in an aqueous solution with a subsequent heat treatment to form Fe₂O₃ shell and employed as a cathode catalyst for non aqueous Li-air batteries. The synthesized core-shell nanowires with an average diameter of 50–100 nm manifest superior catalytic activity for oxygen evolution reaction (OER) in Li-O₂ batteries with the charge voltage plateau reduced to ～3.8 V. An outstanding performance of cycling stability was also achieved with a cutoff specific capacity of 1000 milliampere hour per gram over 40 cycles at a current density of 100 mA g^?1. The excellent electrochemical properties of Fe@Fe₂O₃ as an O₂ electrode are ascribed to the high surface area of the nanowires’ structure and high electron conductivity. This study indicates that the resulting iron-containing nanostructures are promising catalyst in Li-O₂ batteries.     

Facile synthesis of single-crystalline Co<Subscript>3</Subscript>O<Subscript>4</Subscript> cubes as high-performance anode for lithium-ion batteries

Transition metal oxides have great potential as anode for lithium-ion batteries (LIBs), owing to their high theoretical capacity and low cost. However, the poor cycling stability and electron conductivity have limited the widely expected application of transition metal oxides. In this work, highly single-crystalline Co₃O₄ cubes with 400 nm in the average side length are successfully synthesized by a facile hydrothermal method. When used as anode for LIBs, the Co₃O₄ single-crystalline cubes exhibit highly stable and substantial discharge capacities of the amount to 877 mA h g^?1 at 200 mA g^?1 after 110 cycles with remarkable capacity retention of 98%, and 576 mA h g^?1 even at a high rate of 2000 mA g^?1. The scalability of the preparation method and the impressive results achieved here demonstrate the potential for the application to the future development of transition metal oxides anodes. These results suggest that the single-crystalline Co₃O₄ is a promising electrode material for the high-performance energy storage devices.     

Electrospun Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript>/Li<Subscript>2</Subscript>TiO<Subscript>3</Subscript> composite nanofibers for enhanced high-rate lithium ion batteries

Li₄Ti₅O₁₂/Li₂TiO₃ composite nanofibers with the mean diameter of ca. 60 nm have been synthesized via facile electrospinning. When the molar ratio of Li to Ti is 4.8:5, the Li₄Ti₅O₁₂/Li₂TiO₃ composite nanofibers exhibit initial discharge capacity of 216.07 mAh g^?1 at 0.1 C, rate capability of 151 mAh g^?1 after being cycled at 20 C, and cycling stability of 122.93 mAh g^?1 after 1000 cycles at 20 C. Compared with pure Li₄Ti₅O₁₂ nanofibers and Li₂TiO₃ nanofibers, Li₄Ti₅O₁₂/Li₂TiO₃ composite nanofibers show better performance when used as anode materials for lithium ion batteries. The enhanced electrochemical performances are explained by the incorporation of appropriate Li₂TiO₃ which could strengthen the structure stability of the hosted materials and has fast Li⁺-conductor characteristics, and the nanostructure of nanofibers which could offer high specific area between the active materials and electrolyte and shorten diffusion paths for ionic transport and electronic conduction. Our new findings provide an effective synthetic way to produce high-performance Li₄Ti₅O₁₂ anodes for lithium rechargeable batteries.     

Influence of Li source on tap density and high rate cycling performance of spherical Li[Ni<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>]O<Subscript>2</Subscript> for advanced lithium-ion batteries

Spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode materials with different microstructure have been prepared by a continuous carbonate co-precipitation method using LiOH⋅H₂O, Li₂CO₃, CH₃COOLi⋅2H₂O and LiNO₃ as lithium source. The effects of Li source on the physical and electrochemical properties of Li[Ni_1/3Co_1/3Mn_1/3]O₂ are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The results show that the morphology, tap density and high rate cycling performance of Li[Ni_1/3Co_1/3Mn_1/3]O₂ spherical particles are strongly affected by Li source. Among the four Li sources used in this study, LiOH⋅H₂O is beneficial to enhance the tap density of Li[Ni_1/3Co_1/3Mn_1/3]O₂, and the tap density of as-prepared sample reaches 2.32 g cm⁻³. Meanwhile, Li₂CO₃ is preferable when preparing the Li[Ni_1/3Co_1/3Mn_1/3]O₂ with high rate cycling performance, upon extended cycling at 1 and 5C rates, 97.5% and 92% of the initial discharge capacity can be maintained after 100 cycles.     

Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>/carbon nanotubes nanocomposites as improved anode materials for lithium-ion batteries

Mn₃O₄ and Mn₃O₄ (140)/CNTs have been investigated as high-capacity anode materials for lithium-ion batteries (LIBs) applications. Nanoparticle Mn₃O₄ samples were synthesized by hydrothermal method using Mn(Ac)₂ and NH₃·H₂O as the raw materials and characterized by XRD, TG, EA, TEM, and SEM. Its electrochemical performances, as anode materials, were evaluated by galvanostatic discharge-charge tests. The Mn₃O₄ (140)/CNTs displays outstanding electrochemical performances, such as high initial capacity (1942 mAh g^?1), stable cycling performance (1088 mAh g^?1 and coulombic efficiency remain at 97% after 60 cycles) and great rate performance (recover 823 mAh g^?1 when return to initial current density after 44 cycles). Compared to pure Mn₃O₄ (140), the improving electrochemical performances can be attributed to the existence of very conductive CNTs. The Mn₃O₄ (140)/CNTs with excellent electrochemical properties might find applications as highly effective materials in electromagnetism, catalysis, microelectronic devices, etc. The process should also offer an effective and facile method to fabricate many other nanosized metallic oxide/CNTs nanocomposites for low-cost, high-capacity, and environmentally benign materials for LIBs.     

Ammonia gas sensor based on a spinel semiconductor,Co<Subscript>0.8</Subscript>Ni<Subscript>0.2</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanomaterial

Thick film of nanocrystalline Co_0.8Ni_0.2Fe₂O₄ was obtained by sol–gel citrate method for gas sensing application. The synthesized powder was characterized by X-ray diffraction (XRD) and transmission electron microscopy. The XRD pattern shows spinel type structure of Co_0.8Ni_0.2Fe₂O₄. XRD of Co_0.8Ni_0.2Fe₂O₄ revels formation of solid solution with average grain size of about 30 nm. From gas sensing properties it observed that nickel doping improves the sensor response and selectivity towards ammonia gas and very low response to LPG, CO, and H₂S at 280 °C. Furthermore, incorporation of Pd improves the sensor response and stability of ammonia gas and reduced the operating temperature upto 210 °C. The sensor is a promising candidate for practical detector of ammonia.     

Preparation and adsorption of magnetic Co<Subscript>0.5</Subscript>Ni<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>-chitosan nanoparticles

In this paper, magnetic chitosan microspheres were prepared by the emulsification cross-linking technique, with glutaraldehyde as the cross-linking agent, liquid paraffin as the dispersant, and the Span-80 as emulsifier. The time of cross-linking and the ratio of Co_0.5Ni_0.5Fe₂O₄/chitosan were investigated. The morphology was studied by different instruments. The adsorption performance was investigated and the effects of initial concentration of methyl orange, the time of cross-linking, and the amount of adsorbent were discussed. It is found that the product has uniform morphology when the ratio of magnetic Co_0.5Ni_0.5Fe₂O₄/chitosan is 1 : 2 and the time of cross-linking is 5 h; At room temperature, magnetic Co_0.5Ni_0.5Fe₂O₄–chitosan has a good adsorption toward methyl orange when the magnetic Co_0.5Ni_0.5Fe₂O₄/chitosan dosage is 20 mg.