Niobium doping of Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials with enhanced structural stability and electrochemical performance

Lithium-rich layered oxides with high energy density have been intensively investigated as advanced lithium-ion batteries cathode materials. However, capacity degradation and voltage decay caused by irreversible lattice oxygen loss and structural transformation during cycling restrict their application. Herein, we proposed a high valance cations Nb⁵⁺ doping strategy and synthesized a series of Li_1.2Mn_0.54-x/3Ni_0.13-x/3Co_0.13-x/3Nb_xO₂ (x = 0, 0.01, 0.02 and 0.03) cathode materials. The effects of Nb⁵⁺ doping on crystallographic structure and electrochemical property were systematically studied. In virtue of the large ionic radii and strengthened Nb–O bonds, the doped samples present commendable structural stability and expanded interlayer spacing for Li-ions migration, which ensures the upgraded cyclic stability and rate performance. In particular, the electrode with x = 0.02 delivers a discharge specific capacity of 265.8 mAh g^-1 at 0.2 C with decelerated voltage decay, while 86.9% capacity are remained after long-term cycles. Moreover, excellent discharge specific capacity of 153.4 mAh g⁻¹ is still attained at 5 C accompanied with enhanced Li-ion diffusion kinetics.     

Flower-like hierarchical Li1.2Ni0.13Co0.13Mn0.54O2 by architectural design for lithium-ion batteries with superior capacity retention

In this work, hierarchical flower-like Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ (LNCM) with exposed {010} planes assembled and double-sphere Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ without {010} planes as a comparison were successfully synthesized via a simple solvothermal method. The diffusion of Li⁺ could be enhanced in the flower-like LNCM with exposed {010} active planes, and the cathode exhibits a superior electrochemical performance especially in long-term cycling stability even at high current densities. The initial discharge capacity of this sample is 274 mA h g⁻¹ at 0.1C (25 mA g⁻¹), with corresponding initial coulombic efficiencies of 77%. Especially, the capacity retention reaches up to 98% at 1250 mA g⁻¹ current density after 100 cycles. By comparing with other LNCM materials reported recently, our optimal cathode has a pretty outstanding electrochemical performance, which is promising for the next generation lithium ion batteries.     

Effect of ZIF-67 derivative Co3O4 on Li-rich Mn-based cathode material Li1.2Mn0.54Ni0.13Co0.13O2

The zeolitic imidazolate frameworks 67 (ZIF-67) derivative Co₃O₄ composite lithium-rich manganese-based layered oxide was successfully synthesized by a simple solid-phase sintering method and systematically studied. The introduction of the derivatives does not excessively induce changes in the transition metal layered oxide structure as tested by XRD, SEM, TEM, and XPS. The electrochemical test and analysis show that the high surface area and porous structure of the ZIF-67 derivative Co₃O₄ can promote the contact efficiency of the electrode and the electrolyte, thereby delaying the structural phase change which caused by the long cycle process and suppressing the voltage attenuation. In particular, a composite ratio of 10:1 samples can most effectively improve the first coulomb efficiency, cycling stability, and structural stability of lithium-rich materials. The discharge specific capacity at 0.1 C is 258.9 mAh/g, and the first coulomb efficiency is 74.93%. Especially, the discharge specific capacity at 0.5 C is 234.1 mAh/g, and the capacity retention rate is 86.28% after 100 cycles.     

SmPO4-coated Li1.2Mn0.54Ni0.13Co0.13O2 as a cathode material with enhanced cycling stability for lithium ion batteries

SmPO₄ coated Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode materials were prepared by the precipitation method and calcined at 450 °C. The crystal structures and electrochemical properties of the pristine and coated samples are studied by X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, electron diffraction spectroscopy, galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). It has been found that the electrochemical performances of the Li-rich cathode material have been substantially improved by SmPO₄ surface coating. Especially, the 2 wt% SmPO₄-coated sample demonstrates the best cycling performance, with capacity retention of 88.4% at 1 C rate after 100 cycles, which is much better than that of 72.3% in the pristine sample. The improved electrochemical properties have been ascribed to the SmPO₄ coating layer, which not only stabilizes the cathode structure by decreasing the loss of oxygen, but also protects the Li-rich cathode material from side reaction with the electrolyte and increases the Li⁺ migration rate at the cathode interface.     

Fast Li-ion conductor Li1+yTi2-yAly(PO4)3 modified Li1.2[Mn0.54Ni0.13Co0.13]O2 as high performance cathode material for Li-ion battery

In the material of xLi₂MnO₃ ·(1-x) LiMO₂ (0 < x < 1), the Li₂MnO₃ component is used to stabilize the layered LiMO₂ structure. However, the electrochemical inactive Li₂MnO₃ makes Li-ion diffusion difficult, leading to a sluggish rate capability. In this work, Li_1.3Ti_1.7Al_0.3(PO₄)₃ (LTA0.3), a NASICON-type Li-ion conductor, is applied to modified Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ to overcome the above shortcoming. Additionally, the Li-ion conductivity of LiTi₂(PO₄)₃ can be improved effectively by replacing tetravalent cation Ti⁴⁺ with trivalent Al³⁺ at the optimal ratio. At 1C rate, the LR cathode with 3 wt% LTA0.3 delivers 200 mAh g^?1 after 170 cycles and maintains 140 mAh g^?1 after 500 cycles. Moreover, the modified cathode shows an enhanced rate performance of 169.7 mAh g^?1 at 5C. Enhanced cycle durability and rate capability are aroused by the 3D skeletal framework of LTA0.3, which is suitable for Li-ion diffusion. The LTA0.3 coating layer displays a robust shell which not only avoids the corrosion of electrode materials but also effectively facilitates Li-ion diffusion.     

Surface modification of Li rich Li1.2Mn0.54Ni0.13Co0.13O2 cathode particles

Li-rich Mn-based layered oxide Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (LMNCO) has received great interest due to its high discharge capacity. However, the fast capacity attenuation seriously hinders its wide application. LMNCO particles are synthesized via a co-precipitation method. To enhance the cycle stability, (Ni_0.4Co_0.2Mn_0.4)_1-xTi_x(OH)_2+2x surface layer is deposited on LMNCO precursor particles by a second co-precipitation process. Due to the mutual diffusion of elements during sintering, Ti is distributed in the 2–3 μm shell of particles. The cells are cycled in a voltage window of 2.0–4.8 V at 0.5C. After 200 cycles, LMNCO exhibits a capacity retention of 43%, and LMNCO particles have been pulverized by the cycle process. In contrast, the structural integrity of coated particles is maintained, and therefore the cycle stability is evidently improved.     

Investigation on performances of Li1.2Co0.4Mn0.4O2 prepared by self-combustion reaction as stable cathode for lithium-ion batteries

Poor rate capability and cycling performance are the major barriers for Li-rich layered cathode materials to be applied as the next generation cathode materials for lithium-ion batteries. In our work, Li_1.2Co_0.4Mn_0.4O₂ has been successfully synthesized via a self-combustion reaction (SCR) and a calcination procedure. Compared with the material produced by the solid state method (SSM), the one by SCR exhibits both better rate capability and cycling performance. Its initial discharge capacity is 166.01 mA h g⁻¹ with the capacity retention of 85.98% after 50 cycles at a current density of 200 mA h g⁻¹. Its remarkable performance is attributed to a thin carbon coating layer, which not only slows down the transformation rate of layered to spinel structure, but provides a good electronic pathway to increase the Li⁺ diffusion coefficient.     

Ultrathin-Y2O3-coated LiNi0.8Co0.1Mn0.1O2 as cathode materials for Li-ion batteries: Synthesis,performance and reversibility

Nickel-rich lithium material LiNi_xCo_yMn_1-x-yO₂(x > 0.6) becomes a new research focus for the next-generation lithium-ion batteries owing to their high operating voltage and high reversible capacity. However, the rate performance and cycling stability of these cathode materials are not satisfactory. Inspired by the characteristics of Y₂O₃ production, a new cathode material with ultrathin-Y₂O₃ coating was introduced to improve the electrochemical performance and storage properties of LiNi_0.8Co_0.1Mn_0.1O₂ for the first time. XRD, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS) and XPS were used to mirror the crystal and surface of LiNi_0.8Co_0.1Mn_0.1O₂ particles, results i that a uniform interface formed on as-prepared material. The impacts on the electrochemical properties with or without Y₂O₃ coating are discussed in detail. Notably, galvanostatic discharge-charge tests appear that Y₂O_3-coated sample especially 3% coating displayed a better capacity retention rate of 91.45% after 100 cycles than the bare one of 85.07%.     

Effect of molybdenum substitution on electrochemical performance of Li[Li0.2Mn0.54Co0.13Ni0.13]O2 cathode material

Molybdenum doping is introduced to improve the electrochemical performance of lithium-rich manganese-based cathode material. X-ray diffraction (XRD) results illustrate that the crystallographic parameters a, c and lattice volume V become larger with the increase of Mo content. The scanning electron microscope (SEM) shows that the molybdenum substitution increases the crystallinity of the primary particles. When evaluated as cathode material, the as-prepared Li[Li_0.2Mn_0.54-x/3Ni_0.13-x/3Co_0.13-x/3Mo_x]O₂ (x = 0.007) delivers a discharge capacity of 155.5 mA h g⁻¹ at 5 C (1 C = 250 mA g⁻¹) and exhibits the capacity retention of 81.8% at 1 C after 200 cycles. The results of cyclic voltammetry (CV) and electronic impedance spectroscopy (EIS) tests reflect that the molybdenum substitution is able to significantly reduce the electrode polarization and lower the charge-transfer resistance. Within appropriate amount of Mo doping, the lithium ion diffusion coefficient of the material can reach to 8.92 × 10^–15 cm² s⁻¹, which is ~ 30 times higher than that of pristine materials (2.65 × 10^–16 cm² s⁻¹).     

无人机用锂离子电池正极材料Li1.20Mn0.54Ni0.13Co0.13O2的Mo6+掺杂改性研究

采用碳酸盐共沉淀法和高温烧结工艺将一定量的Mo⁶⁺掺杂到Li_1.20Mn_0.54Ni_0.13Co_0.13O₂正极材料中。利用XRD、SEM、EDS和恒流测试仪研究Mo⁶⁺掺杂对Li_1.20Mn_0.54Ni_0.13Co_0.13O₂正极材料的晶体结构、微观形貌和电化学性能的影响。结果显示,Li_1.20Mn_0.52Ni_0.13Co_0.13Mo_0.02O₂表现出更低的阳离子混排和优异的电化学性能。经过Mo⁶⁺掺杂后的正极,由于Li⁺高速的迁移速率,使得首次不可逆容量损失降低,并展现出更好的高倍率性能和优异的循环稳定性。在0.5C倍率下循环100周后,Li_1.20Mn_0.52Ni_0.13Co_0.13Mo_0.02O₂的容量保持率达到92.2%,远远大于Li_1.20Mn_0.54Ni_0.13Co_0.13O₂的87.5%。另外,当放电倍率增大到5C时,Li_1.20Mn_0.54Ni_0.13Co_0.13O₂的放电比容量要比Li_1.20Mn_0.52Ni_0.13Co_0.13Mo_0.02O₂低21.0 mA·h/g。因此,采用Mo⁶⁺掺杂改性Li_1.20Mn_0.54Ni_0.13Co_0.13O₂正极材料,可以有效提高锂电池的循环保持率和高倍率放电性能。     

Self-standing flexible cathode of V2O5 nanobelts with high cycling stability for lithium-ion batteries

Self-standing V₂O₅ nanobelt electrode free of binders, conductive carbon or current collectors was successfully prepared via a simple one-step hydrothermal reaction. The length of V₂O₅ nanobelts was up to several hundreds micrometers and the thickness was around 40 nm. Ultralong nanobelts as building blocks and internal voids provide a robust mechanical flexibility and shortened ion/electron transport pathway. The self-standing electrode delivered an initial specific capacity of 127.4 mA h g⁻¹ at a current density of 60 mA g⁻¹ and exhibited excellent cycling stability with capacity retention up to 89.8% after 200 cycles. The outstanding cycling performance can be attributed to the excellent network stability, shortened Li-ion diffusion pathway and the high surface area between electrolyte/electrode interfaces.     

Li_(1.2)Mn_(0.54)Co_(0.13)Ni_(0.13)O_2/V_2O_5复合材料的制备及电化学性能

实验采用NH_4VO_3对富锂锰基材料Li_(1.2)Mn_(0.54)Co_(0.13)Ni_(0.13)O_2(Lirich)进行表面修饰。使用扫描电镜(SEM)、X射线衍射(XRD)以及电化学方法等手段进行了表征。TEM显示在材料表面形成10 nm左右的包覆层。XRD结果发现,包覆后的Li_(1.2)Mn_(0.54)Co_(0.13)Ni_(0.13)O_2(Lirich-V_2O_5)晶体中出现Li_3VO_4。Lirich-V_2O_5的首次充放电效率为103.1%,说明V_2O_5包覆层对Li Mn_(0.54)Co_(0.13)Ni_(0.13)O_2起到了预活化的作用。Lirich循环20圈之后的容量保持率为71.4%,而Lirich-V_2O_5的容量保持率则达到了90.4%,说明V_2O_5包覆层有效抑制材料与电解液的副反应。     

ZrO2-coated Li3V2(PO4)3/C nanocomposite: A high-voltage cathode for rechargeable lithium-ion batteries with remarkable cycling performance

In this study, we show that the poor cycling performance which seriously hinders the application of Li₃V₂(PO₄)₃/C for rechargeable lithium-ion batteries is overcome by amorphous ZrO₂ nano-coating. The ZrO₂-coated Li₃V₂(PO₄)₃/C was synthesized via a conventional solid-state method followed by the application of wet coating. The crystalline structure, morphology and electrochemical performance of the as-synthesized samples were investigated by XRD, SEM, TEM, EDS, galvanostatic charge/discharge and EIS measurements. Compared with the pristine Li₃V₂(PO₄)₃/C, the structure of ZrO₂-coated Li₃V₂(PO₄)₃/C sample had no change, and the existence of ZrO₂ nano-coating effectively enhanced the cycling performance. From the above results, it is believed that the improved cycling performance is attributed to the ability of ZrO₂ layer in preventing direct contact of the active material with the electrolyte resulting in a decrease of electrolyte decomposition reactions.     

Graphene nanosheet and carbon layer co-decorated Li4Ti5O12 as high-performance anode material for rechargeable lithium-ion batteries

In this study, we report a facile strategy for anchoring Li₄Ti₅O₁₂ (LTO) particles wrapped within carbon shells onto graphene nanosheet (GNS) using the freeze-drying assisted microwave irradiation method. In this designed structure, a conductive three-dimensional network can be formed by connecting the GNS and carbon layer which is benefit for the transport of electron and Li⁺-ion. When used as anode material for lithium-ion batteries, this hybrid composite exhibits an excellent high-rate performance with specific capacities of 171.5, 168.2, 160.1, 151.7 and 136.4 mAh g⁻¹ at various current rates of 1, 2, 5, 10 and 20 C, respectively. Furthermore, the specific capacity of the obtained anode still retains 99.6% of the initial value after 20 cycles at 20 C. The enhanced battery performance can be attributed to the improved electronic conductivity of each LTO grain via uniform carbon coating and GNS wrapping. As a consequence, this novel strategy developed in this study may open a new way to fabricate other electrodes for advanced renewable energy conversion and storage applications.     

Enhanced Li-storage performance of In-doped Li1.21[Mn0.54Ni0.125Co0.125]O2 as Li- and Mn-rich cathode materials for lithium-ion batteries

Journal of Applied Electrochemistry - Lithium manganese-rich nickel–manganese–cobalt oxides (LMR-NMCs) are promising candidates for cathodes in Li-ion batteries (LIBs) due to their high...     

Enhanced electrochemical performance of core-shell Li4Ti5O12/PTh as advanced anode for rechargeable lithium-ion batteries

A nanocomposite of Li₄Ti₅O₁₂ particles coated with polythiophene (PTh) was fabricated as advanced anode for rechargeable lithium-ion batteries. The conducting PTh layer was successfully coated on the surface of Li₄Ti₅O₁₂ through the in-situ oxidative polymerization method. Benefiting from the core-shell structure, specific capacities as high as 171.5, 168.2 and 151.1 mA h g⁻¹ at 0.2, 1 and 10 C are obtained in the Li₄Ti₅O₁₂/PTh composite. The electrochemical results also show that the Li₄Ti₅O₁₂/PTh exhibits remarkably improved cycling performance as compared with the Li₄Ti₅O₁₂ anode. Moreover, the charge-transfer resistance of Li₄Ti₅O₁₂/PTh electrode is much lower than that of the bare Li₄Ti₅O₁₂, revealing that the PTh coating can significantly increase the electron conductivity between the Li₄Ti₅O₁₂ particles. The excellent electrochemical performance of the as-fabricated Li₄Ti₅O₁₂/PTh composite can be ascribed to the PTh layer which can suppress the dissolution of active material into the LiPF₆ electrolyte and enhance the electron conductivity of Li₄Ti₅O₁₂ nanocrystals. Thus, the Li₄Ti₅O₁₂/PTh composite is an advanced anode for use in high performance lithium-ion batteries application.     

锂离子二次电池新型正极材料LiMPO4(M=Fe、Co、Ni等)的研究进展

综述了锂离子二次电池新型正极材料LIMPO4(M=Fe、Co、Ni、Mn等)的研究进展。重点对该材料的结构、结构与电化学性能的关系、多种阳离子掺杂对材料性能的影响以及多种合成方法进行了较详细的评述,并对该材料的应用前景进行了展望。     

In-situ synthesis of reduced graphene oxide wrapped Mn3O4 nanocomposite as anode materials for high-performance lithium-ion batteries

We report a novel in-situ symbiosis method to prepare reduced graphene oxide wrapped Mn₃O₄ nanoparticles (rGO/Mn₃O₄) with uniform size about 50 nm as anodes for lithium-ion batteries (LIBs), which can simplify the preparation process and effectively reduce pollution. The rGO/Mn₃O₄ nanocomposite exhibited a reversible specific capacity of 795.5 mAh g^?1 at 100 mA g^?1 after 200 cycles (capacity retention: 87.4%), which benefits from the unique structural advantages and the synergistic effect of rGO and Mn₃O₄. The Mn₃O₄ nanoparticles encapsulated among the rGO nanosheets exhibited good electrochemical activity, and the multilayer wrinkled rGO sheets provided a stable 3D conduction channel for Li⁺/e^? transport. The rGO/Mn₃O₄ nanocomposite is a promising anode candidate for advanced LIBs with excellent cycling performance and rate performance. Furthermore, this new preparation method can be extended to green and economical synthesis of advanced graphene/manganese-based nanocomposites.     

Nanoparticles constructed mesoporous coral-like Mn2O3 as high performance anode for lithium-ion batteries

As well established, the morphology and architecture of electrode materials greatly contribute to the electrochemical properties. Herein, a novel structure of mesoporous coral-like manganese (III) oxide (Mn₂O₃) is synthesized via a facile solvothermal method coupled with the carbonization under air. When fabricated as anode electrode for lithium-ion batteries (LIBs), the as-prepared Mn₂O₃ exhibits good electrochemical properties, showing a high discharge capacity of 1090.4 mAh g^?1 at 0.1 A g^?1, and excellent rate performance of 410.4 mAh g^?1 at 2 A g^?1. Furthermore, it maintains the reversible discharge capacity of 1045 mAh g^?1 at 0.1 A g^?1 after 380 cycles, and 755 mAh g^?1 at 1 A g^?1 after 450 cycles. The durable cycling stability and outstanding rate performance can be attributed to its unique 3D mesoporous structure, which is favorable for increasing active area and shortening Li⁺ diffusion distance.     

Enhanced electrochemical performance of Li1.2(Ni0.17Co0.07Mn0.56)O2 via constructing double protection layers by facile phytic acid treatment

As one of the most promising cathode materials for next-generation of lithium-ion batteries, Li-rich Mn-based oxides are still hindered by inferior cycling properties and poor rate performance. Surface modification is proved to be feasible to tackle these problems. Herein, we chose phytic acid to construct spinel and Li₃PO₄ double protection layers on the Li_1.2(Ni_0.17Co_0.07Mn_0.56)O₂ cathode material via a simple synchronous approach. The 3 wt% phytic acid treated sample achieves markedly enhanced electrochemical performance, such as elevated initial Coulombic efficiency reaching 90.0%, increased capacity retention of 87.8% after 150 cycles at 1 C and alleviated average discharge voltage drop of 1.63 mV per cycle. These impressive electrochemical properties can be ascribed to the designed hierarchical interface, which not only can synergistically retain structural stability but also provide fast Li⁺ transport channels. Taken together, this work employs a facile and novel route to enhance the electrochemical performance of Li_1.2(Ni_0.17Co_0.07Mn_0.56)O₂, which may afford inspiration to the commercialization of Li-rich cathode materials.