X-ray diffraction study on phase transition of orthorhombic LiMnO2 in electrochemical conversions

Orthorhombic LiMnO₂ was synthesized by hydrothermal reaction. Phase transition during electrochemical process has been investigated using the high-resolution X-ray diffraction. Contrary to numerous earlier reports, phase analysis of the orthorhombic LiMnO₂ electrode cycled for three times evidences the irreversible structure transition from orthorhombic LiMnO₂ (Pmnm) to spinel LiMn₂O₄ (Fd3m) and rock salt Li_0.5Mn_0.5O (Fm \( \overline{3} \) m). Here, the spinel structure with a cell parameter a?=?8.241 (1) Å has a large cationic disorder on lithium and manganese sites, i.e., about 9% of the Li positions are occupied by Mn and vice versa. For Li_0.5Mn_0.5O, the cell parameter is a?=?4.121 (3) Å, and both Li⁺ and Mn³⁺ cations occupy the octahedral 4a sites with mole ratio 1:1. The quantity of Li_0.5Mn_0.5O phase is greatly dependent on cycling rate, namely, the higher the current density is, the larger the quantity of formed-rock salt structure is.     

Suppression of charge imbalance via Li+-Mn4+ co-incorporated Sr2YSbO6 red phosphors for warm w-LEDs

Mn⁴⁺-activated double perovskite phosphors with composition diversity have presented excellent luminescent performances. However, the charge imbalance between Mn⁴⁺ and matrix cations would increase non-radiative recombination and reduce the structural stability. Here, novel high-efficiency stable Li⁺/Mn⁴⁺ co-incorporated Sr₂YSbO₆ red phosphors are successfully synthesized via a solid-state reaction method for warm w-LEDs, where the Li⁺ ions have the effect of charge balance for Sr₂YSbO₆:Mn⁴⁺ and reduce the non-radiative energy transfer among Mn⁴⁺ ions. It is demonstrated that the substitution of Li⁺–Mn⁴⁺ pairs for Sb⁵⁺ can enhance the bonding with low-shifted diffraction peaks and high emission intensity, and prolong the decay lifetime, compared with those of Mn⁴⁺ single-doped ones. Impressively, the thermal stability is enhanced to 89.72% from 84.61% at the original value of 303 K. Finally, a w-LED device based on the optimal phosphor Sr₂YSbO₆:0.01Mn⁴⁺/0.01Li⁺ red component exhibits a correlated color temperature of 4487 K and color rendering index of 80.2. Therefore, the incorporated Li⁺ ions serve as both charge compensator and co-activator in Mn⁴⁺-activated double perovskite phosphors with the aim of high luminescent performance and thermal stability.     

Synthesis of Li[Li0.2Ni0.2Mn0.6]O2 by radiated polymer gel method and impact of deficient Li on its structure and electrochemical properties

Layered Li[Li_0.16Ni_0.21Mn_0.63]O₂ and Li[Li_0.2Ni_0.2Mn_0.6]O₂ compounds were successfully synthesized by radiated polymer gel (RPG) method. The effect of deficient Li on the structure and electrochemical performance was investigated by means of X-ray diffraction, X-ray absorption near-edge spectroscopy and electrochemical cell cycling. The reduced Ni valence in Li[Li_0.16Ni_0.21Mn_0.63]O₂ leads to a higher capacity owing to faster Li⁺ chemical diffusivity relative to the baseline composition Li[Li_0.2Ni_0.2Mn_0.6]O₂. Cyclic voltammograms (CV) and a simultaneous direct current (DC) resistance measurement were also performed on Li/Li[Li_0.16Ni_0.21Mn_0.63]O₂ and Li/Li[Li_0.2Ni_0.2Mn_0.6]O₂ cells. Li[Li_0.16Ni_0.21Mn_0.63]O₂ shows better electrochemical performance with a reversible capacity of 158 mA hg⁻¹ at 1C rate at 20 °C.     

Variation of the composition and properties of lithium manganese oxide spinel in lithiation-delithiation cycles

The behavior of the variable-composition spinel Li_{1 + x} Mn_{2 ? x} O₄ is examined in repeated cycles consisting of lithiation in 0.2 M LiOH and delithiation in 0.3 M HNO₃. For 0 < x < 0.33, delithiation is accompanied by the redox reaction 2Mn³⁺ → Mn⁴⁺ + Mn²⁺ and Li⁺ ? H⁺ ion exchange. The spinel undergoes partial conversion into λ-□MnO₂. Vacancies (□) build up at the 8a sites of the spinel structure. Mn²⁺ ions pass into the solution, and, accordingly, the spinel dissolves. Lithiation is accompanied by the redox reaction 4Mn⁴⁺ → 3Mn³⁺ + Mn⁷⁺ and ion exchange, and the proportion of vacancies □ at the 8a sites of the spinel structure decreases. The spinel undergoes partial dissolution because of Mn²⁺ and MnO _? ⁴ ions passing into the solution. The Li⁺ selectivity of the spinel is the property of the crystallite core. The crystallite surface is capable of sorbing Na⁺ ions.     

Boosting Li-ion storage in Li2MnO3 by unequal-valent Ti4+-substitution and interlayer Li vacancies building

Lithium rich layered oxide (LRLO) has been considered as one of the promising cathodes for lithium-ion batteries (LIBs). The high voltage and large capacity of LRLO depend on Li₂MnO₃ phase. To ameliorate the electrochemical performance of Li₂MnO₃, also written as Li(Li_1/3Mn_2/3)O₂, we propose a strategy to substitute Mn⁴⁺ and Li⁺ in Mn/Li transition metal layer with Ti⁴⁺, which can stabilize the structure of Li₂MnO₃ by inhibiting the excessive oxidation of O^2? above 4.5 V. More significantly, the unequal-valent substitution brings about the emergence of interlayer Li vacancies, which can promote the Li-ion diffusion based on the enlarged interlayer and increase the capacity by activating the Mn^3+/4+ redox. We designed Li_0.7[Li_1/3Mn_2/3]_0.7Ti_0.3O₂ with high interlayer Li vacancies, which presents a high capacity (290 mAh/g at 10 mA/g) and stable cycling performance (84% over 60 cycles at 50 mA/g). We predict that this strategy will be helpful to further improve the electrochemical performance of LRLOs.     

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.     

Li3PO4表面修饰提高球形LiNi0.5Mn1.5O4正极材料的性能

通过共沉淀法制备了球形LiNi_0.5Mn_1.5O₄@Li₃PO₄复合材料,并采用X射线衍射(XRD)、扫描电镜(SEM)、红外光谱(FT-IR)、循环伏安(CV)、电化学阻抗谱(EIS)及充放电测试研究了其结构与电化学性能。XRD和SEM表明,Li₃PO₄包覆影响了球形LiNi_0.5Mn_1.5O₄的晶格常数。CV和EIS表明,质量百分数5% Li₃PO₄包覆的LiNi_0.5Mn_1.5O₄具有比纯LiNi_0.5Mn_1.5O₄更高的锂离子嵌脱可逆性,更大的锂离子扩散系数和更小的电荷转移电阻,说明在锂离子扩散过程中,质量百分数5%Li₃PO₄包覆的LiNi_0.5Mn_1.5O₄具有更高的电子电导率。充放电测试表明,原位Li₃PO₄改性提高了材料的电子电导率、电化学活性,进而提高了高倍率放电容量。质量百分数5% Li₃PO₄包覆的LiNi_0.5Mn_1.5O₄提高的电化学性能归因于Li₃PO₄的包覆、纳米颗粒组成球形的粒径引起的高的电子电导率和小的电化学极化。     

Synthesis of orthorhombic LiMnO2 by solid-phase reaction under steam atmosphere and a study of its heat and acid-treated phases

Low crystalline orthorhombic LiMnO₂ (o-LiMnO₂) samples were synthesized by reacting either γ-MnOOH or Mn₂O₃ with LiOH·H₂O in the solid phase under steam atmosphere at 120°C. In the closed system, the vapor arising from LiOH·H₂O may strengthen the reactivity of LiOH at the surface of MnOOH or Mn₂O₃ particles, which may enable slow diffusion of Li⁺ ions forming LiMnO₂. These samples were compared with crystalline o-LiMnO₂ prepared by a solid-state reaction method at 700°C in nitrogen gas. The powder X-ray diffraction patterns of low crystalline samples after heating at 400°C in air revealed the formation of a single phase of cubic Li_1.6Mn_1.6O₄, but the crystalline sample revealed a mixed phase of o-LiMnO₂ and LiMn₂O₄ after heating at 400°C in air. The Li⁺/H⁺ exchange in the Li_1.6Mn_1.6O₄ sample progressed topotactically, while maintaining the crystal structure and morphology of the precursor. But heat-treated crystalline o-LiMnO₂ showed a disproportionation reaction with dissolution of Mn²⁺ ions.     

球形PVC-MnO2离子筛的制备及锂吸附性能

本实验室前期所制备的Li4Mn5O12超细粉末在卤水体系中对Li+具有较大的吸附容量和良好的选择性。但由于超细粉体的流动性和渗透性差,无法直接应用于固定床,需对粉末吸附材料进行成型造粒,以便于实际应用。本论文采用聚氯乙烯为粘结剂,制备出粒径约为2.0~3.5 mm的球形PVC-Li4Mn5O12,经盐酸处理后得到球形PVC-MnO2离子筛。并通过扫描电镜(SEM)、X射线衍射仪(XRD)、静态和动态连续锂吸附实验研究了球形离子筛形貌和锂离子吸附性能。结果表明,球形离子筛对Li+的吸附容量高达5.28 mmol.g-1,在混合溶液中对Li+具有良好的选择性,这对于在盐湖卤水或海水提锂具有重要的实用意义。     

High-capacity Li(Ni0.5Co0.2Mn0.3)O2 lithium-ion battery cathode synthesized using a green chelating agent

Quasi-spherical (Ni_0.5Co_0.2Mn_0.3)(OH)₂ precursor is prepared via a continuous hydroxide co-precipitation method using sodium lactate as the green chelating agent. A layered structure Li(Ni_0.5Co_0.2Mn_0.3)O₂ is synthesized by calcining the mixture of as-prepared precursor and Li₂CO₃ in air. X-ray photoelectron spectroscopy (XPS) indicates that Ni, Co, and Mn exist in the oxidation states of +2/+3, +3 and +4, respectively. The influence of calcination temperature on the structural, morphological, electrochemical properties of Li(Ni_0.5Co_0.2Mn_0.3)O₂ oxides are investigated in detail. As a result, the sample calcined at 850 °C shows excellent electrochemical performance, which could be ascribed to its good crystal structure, low cation disorder, appropriate crystallinity. This sample delivers an initial discharge capacity of 192.6 mA h g^?1 with a coulombic efficiency of 89.5 % at a current density of 20 mA g^?1, and exhibits good rate capability and stable cyclability. Finally, the electrochemical performance of the sodium lactate-derived sample is briefly compared with those of the oxalic acid-derived and ammonia-derived oxide.     

Ag/C包覆对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响

运用共沉淀和元素化学沉积相结合的方法,制备出了具有Ag/C 包覆层的层状富锂固溶体材料Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂. 通过X 射线衍射（XRD）、场发射扫描电子显微镜（SEM）、透射电子显微镜（TEM）、恒流充放电、循环伏安（CV）,电化学阻抗谱（EIS）和X 射线能量散射谱（EDS）方法,研究了Ag/C 包覆层对Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂电化学性能的影响. 结果表明,Ag/C 包覆层的厚度约为25 nm,Ag/C 包覆在保持了固溶体材料α-NaFeO₂ 六方层状晶体结构的前提下,显著地改善了Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ 的电化学性能. 在2.0-4.8 V（vs Li/Li⁺）的电压范围内,首次放电（0.05C）容量由242.6 mAh·g^-1提高到272.4 mAh·g^-1,库仑效率由67.6%升高到77.4%;在0.2C倍率下,30 次循环后,Ag/C 包覆的电极材料容量为222.6 mAh·g^-1,比未包覆电极材料的容量高出14.45%;包覆后的电极材料在1C下的容量仍为0.05C下的81.3%. 循环伏安及电化学交流阻抗谱研究表明,Ag/C包覆层抑制了材料在充放电过程中氧的损失,有效降低了Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂颗粒的界面膜电阻与电化学反应电阻.     

Synthesis and phase transition of Li-Mn-O spinels with high Li/Mn ratio by thermo-decomposition of LiMnC2O4(Ac)

LiMnC₂O₄(Ac) precursor in which Li⁺ and Mn²⁺ were amalgamated in one molecule was prepared by solid-state reaction at room-temperature using manganese acetate, lithium hydroxide and oxalic acid as raw materials. By thermo-decomposition of LiMnC₂O₄(Ac) at various temperatures, a series of Li_1+y[Mn_2−xLi_x]_16dO₄ spinels were prepared with Li₂MnO₃ as impurities. The structure and phase transition of these spinels were investigated by XRD, TG/DTA, average oxidation state of Mn and cyclic voltammeric techniques. Results revealed that the Li-Mn-O spinels with high Li/Mn ratio were unstable at high temperature, and the phase transition was associated with the transfer of Li⁺ from octahedral 16c sites to 16d sites. With the sintering temperature increasing from 450 to 850 °C, the phase structure varied from lithiated-spinel Li₂Mn₂O₄ to Li₄Mn₅O₁₂-like to LiMn₂O₄-like and finally to rock-salt LiMnO₂-like. A way of determining x with average oxidation state of Mn and the content of Li₂MnO₃ was also demonstrated.     

Lithium extraction/insertion process on cubic Li-Mn-O precursors with different Li/Mn ratio and morphology

The cubic phase LiMn₂O₄ precursors are prepared by high-temperature calcinations (1003 K) of LiOH⋅H₂O and MnO₂ mixture with Li/Mn molar ratio = 0.55. The Li₄Mn₅O₁₂ precursors are synthesized via low-temperature solid-phase reaction (673 K) of LiNO₃ and MnO₂ mixture with Li/Mn molar ratio = 1.0. The ion-sieves counterparts (named SMO-H and SMO-L, respectively) are obtained by the acid treatment of Li-Mn-O precursors. The structure, chemical stability, morphology, ion-exchange property and mechanism of Li-Mn-O precursors and MnO₂ ion-sieve were systematically examined via X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), Infrared Spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and lithium ion selective adsorption measurements. The result shows the more compact Mn-O lattice makes the Li₄Mn₅O₁₂ spinel more stable after the Li⁺ is extracted. The results of IR and XPS show adsorption process of SMO-H exists ion-exchange between the Li⁺ and protons, and redox reaction, but only exists ion-exchange between the Li⁺ and protons in SMO-L. Agglomeration is well-improved by low calcination temperature and the morphology of the Li₄Mn₅O₁₂ precursor and final MnO₂ ion-sieve are effectively controlled within low-dimensional structure. The maximum pH titration capacity of SMO-L for Li⁺ is 6.76 mmol⋅g⁻¹, but only 3.47 mmol⋅g⁻¹ for SMO-H. The ion-sieve obtained from Li₄Mn₅O₁₂ precursor is promising in the lithium extraction from brine or seawater.     

Synthesis,non-isothermal kinetic and thermodynamic studies of the formation of LiMnPO4 from NH4MnPO4·H2O precursor

NH₄MnPO₄·H₂O was successfully synthesized by precipitating method. The LiMnPO₄ was successfully generated through solid state reaction between synthesized NH₄MnPO₄·H₂O precursor and Li₂CO₃. The morphologies were observed to depend on the reaction temperatures. The thermal decomposition of NH₄MnPO₄·H₂O and the formation process of LiMnPO₄ were confirmed by TG/DTG/DTA, FTIR, AAS/AES, XRD and SEM methods. The average crystallite size of NH₄MnPO₄·H₂O, Mn₂P₂O₇ and LiMnPO₄ were found to be around 51.2, 44.9 and 48.1 nm, respectively. The non–isothermal kinetic parameters (kinetic triplet: E_α, A, g(α)) of the formation process of LiMnPO₄ were evaluated from TG data by using Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods. The iterative methods of both equations were carried out to determine the exact values of E_α. The Coats–Redfern equation and kinetic compensation effects were successfully applied to confirm the activation energy and the most probable mechanism functions of the formation of LiMnPO₄. The thermodynamic functions (ΔH^≠, ΔS^≠, ΔG^≠) of the transition state complexes of the formation of LiMnPO₄ were calculated from the kinetic parameters for the first time.     

Effect of the high pressure on the structure and intercalation properties of lithium-nickel-manganese oxides

Lithium-nickel-manganese oxides (Li_1+x(Ni_1/2Mn_1/2)_1−xO₂, x=0 and 0.2), having different cationic distributions and an oxidation state of Ni varying from 2+ to 3+, were formed under a high-pressure (3 GPa). The structure and cationic distribution in these oxides were examined by powder X-ray diffraction, infrared (IR) and electron paramagnetic resonance (EPR) in X-band (9.23 GHz) and at higher frequencies (95 and 285 GHz). Under a high pressure, a solid-state reaction between NiMnO₃ and Li₂O yields LiNi_0.5Mn_0.5O₂ with a disordered rock-salt type structure. The paramagnetic ions stabilized in this oxide are mainly Ni²⁺ and Mn⁴⁺ together with Mn³⁺ (about 10%). The replacement of Li₂O by Li₂O₂ permits increasing the oxidation state of Ni ions in lithium-nickel-manganese oxides. The higher oxidation state of Ni ions favours the stabilization of the layered modification, where the Ni-to-Mn ratio is preserved: Li(Li_0.2Ni_0.4Mn_0.4)O₂. The paramagnetic ions stabilized in the layered oxide are mainly Ni³⁺ and Mn⁴⁺ ions. The disordered and ordered phases display different intercalation properties in respect of lithium. The changes in local Ni,Mn-environment during the electrochemical reaction are discussed on the basis of EPR and IR spectroscopy.     

Water-in-oil microemulsion method preparation and capacitance performance study of Li4Mn5O12

Spinel Li₄Mn₅O₁₂ nanoparticles are successfully prepared by water-in-oil microemulsion method and characterized by X-ray diffraction and scanning electron microscopy. The Li₄Mn₅O₁₂ nanoparticles have sphere-like morphology with particle size less than 50 nm. The Li₄Mn₅O₁₂ and activated carbon (AC) were used as electrodes of Li₄Mn₅O₁₂/AC supercapacitor, respectively. The electrochemical capacitance performance of the supercapacitor was investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The results showed that the single electrode was able to deliver specific capacitance 252 F g^?1 within potential range 0–1.4 V at a scan rate of 5 mV s^?1 in 1 mol L^?1 Li₂SO₄ solution, and it also showed high coulombic efficiency close to 100%. This material exhibited a good cycling performance.     

Origin of the irreversible plateau (4.5 V) of Li[Li0.182Ni0.182Co0.091Mn0.545]O2 layered material

Layered LiNi_0.4Co_0.2Mn_0.4O₂, Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂, Li[Li_1/3Mn_2/3]O₂ powder materials were prepared by rheological phase method. XRD characterization shows that these samples all have analogous structure to LiCoO₂. Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂ can be considered to be the solid solution of LiNi_0.4Co_0.2Mn_0.4O₂ and Li[Li_1/3Mn_2/3]O₂. Detailed information from XRD, ex situ XPS measurement and electrochemical analysis of these three materials reveals the origin of the irreversible plateau (4.5 V) of Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂ electrode. The irreversible oxidation reaction occurred in the first charging above 4.5 V is ascribed to the contribution of Li[Li_1/3Mn_2/3]O₂ component, which maybe extract Li⁺ from the transition layer in Li[Li_1/3Mn_2/3]O₂ or Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂ through oxygen release. This step also activates Mn⁴⁺ of Li[Li_1/3Mn_2/3]O₂ or Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂, it can be reversibly reduced/oxidized between Mn⁴⁺ and Mn³⁺ in the subsequent cycles.     

The tunnel manganese oxide Na4.32Mn9O18: a new Na+ site discovered by single‐crystal X‐ray diffraction

The title compound, tetrasodium nonamanganese octadecaoxide, Na_4.32Mn₉O₁₈, was synthesized by reacting Mn₂O₃ with NaCl. One Mn atom occupies a site of 2/m symmetry, while all other atoms sit on mirror planes. The compound is isostructural with Na₄Ti₄Mn₅O₁₈ and suggestive of Mn³⁺/Mn⁴⁺ charge ordering. It has a double‐tunnel structure built up from double and triple chains of MnO₆ octahedra and single chains of MnO₅ square pyramids by corner sharing. Disordered Na⁺ cations occupy four crystallographic sites within the tunnels, including an unexpected new Na⁺ site discovered inside the large S‐shaped tunnel. A local‐ordering model is used to show the possible Na⁺ distribution, and the unit‐cell evolution during charging/discharging is explained on the basis of this local‐ordering model.     

双相碳改性硅酸铁锂正极材料研究

以活化的天然石墨为碳源,采用固相辅助回流法成功合成了双相碳改性的Li₂FeSiO₄复合材料。采用XRD、SEM、HRTEM和Raman光谱分析了Li₂FeSiO₄/(C+G)复合材料的物相、形貌及其微观结构;并研究了活化石墨用量对Li₂FeSiO₄/(C+G)复合材料的电化学性能的影响。结果表明：活化石墨以石墨微晶和无定形碳的形态共存于Li₂FeSiO₄/(C+G)材料中,活化石墨用量为5%时所得样品的首次放电容量较高(170.3mAh·g^-1),循环50次后其容量保持率为88.7%,表现出了良好的电化学性能。     

Partially substituted lithium manganese oxides as 3 V cathode materials for secondary lithium batteries

Low temperature synthesis and electrochemical properties of partially substituted lithium manganese oxides are reported. We demonstrate various metallic cations (Cu²⁺, Ni²⁺, Fe³⁺, Co³⁺) can be incorporated in the 3 V layered cathodic material Li_0.45MnO_2.1. New compounds Li_0.45Mn_0.88Fe_0.12O_2.1, Li_0.45Mn_0.84Ni_0.16O_2.05, Li_0.45Mn_0.79Cu_0.21O_2.3, Li_0.45Mn_0.85Co_0.15O_2.3 are prepared. These 3 V cathode materials are characterized by the same shape of discharge-charge profiles but different values of the specific capacity, between 90 mAh g⁻¹ and 180 mAh g⁻¹. The best results in terms of capacity and cycle life are obtained with the selected content of 0.15 Co per mole of oxide, as the optimum composition. The high kinetics of Li⁺ transport in Li_0.45Mn_0.85Co_0.15O_2.3 compared to that in the Co-free material is consistent with a substitution of Mn(III) by Co(III) in MnO₂ sheets.