Lithium polyacrylate-coated LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> cathode materials with excellent performance for lithium ion batteries

A novel facile approach to coat LiMn₂O₄ by lithium polyacrylate (PAALi) is demonstrated. The PAALi-coated LiMn₂O₄ (LMO@2%PAALi) and LiMn₂O₄ (LMO) are characterized by charge–discharge tests, X-ray diffraction (XRD), PAALi dissolving experiment, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and inductively coupled plasma optical emission spectrometer (ICP-OES). XRD and FTIR analyses indicate that there are no clear differences between LMO@2%PAALi and LMO. PAALi dissolving experiment indicates that PAALi is indissolvable in LiPF₆-EC/DMC/EMC electrolyte. TEM results reveal that LiMn₂O₄ particles are coated by PAALi. ICP-OES results indicate that this stable PAALi coating can prevent the Mn ions dissolving from active LiMn₂O₄ materials and then the stability of LiMn₂O₄ crystals in electrolyte are greatly enhanced. These unique features ensure that LMO@2%PAALi possesses much better rate performance, higher discharge capacity, better cycling performance, and lower charge transfer resistance over LMO. The discharge capacity of LMO@2%PAALi at 0.2 C reaches up to 127.2 mAh g^?1 at room temperature.     

An approach to improve the electrochemical performance of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> at high temperature

In order to overcome the severe capacity decay of LiMn₂O₄ at high temperature, TiN is used as an active materials additive in this paper. The XRD and XPS test results indicate that the TiN can effectively prevent Mn from dissolving in electrolyte; galvanostatic charge-discharge test shows that LiMn₂O₄ electrode with TiN exhibits remarkably improved capacity retention at high temperature with capacity of 105.1 mAh g^?1 at 1 C in the first cycle at 55 °C and the capacity maintains 88.9% retention after 150 cycles. And the electrochemical impedance spectroscopy result demonstrates TiN’s effectiveness in easing the increase of charge-transfer resistance during cycling. Therefore, we can conclude that TiN, as an addictive, made obvious contribution to the greatly improved electrochemical cycling performance of LiMn₂O₄.     

Elevated electrochemical property of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> originated from nano-sized Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>

By employment of nano-sized pre-prepared Mn₃O₄ as precursor, LiMn₂O₄ particles have been successfully prepared by facile solid state method and sol-gel route, respectively. And the reaction mechanism of the used precursors of Mn₃O₄ is studied. The structure, morphology, and element distribution of the as-synthesized LiMn₂O₄ samples are characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Compared with LiMn₂O₄ synthesized by facile solid state method (SS-LMO), LiMn₂O₄ synthesized by modified sol-gel route (SG-LMO) possesses higher crystallinity, smaller average particle size (~175 nm), higher lithium chemical diffusion coefficient (1.17 × 10^?11 cm² s^?1), as well as superior electrochemical performance. For example, the cell based on SG-LMO can deliver a capacity of 85.5 mAh g^?1 at a high rate of 5 °C, and manifests 88.3% capacity retention after 100 cycles at 0.5 °C when cycling at 45 °C. The good electrochemical performance of the cell based on SG-LMO is ascribed mainly to its small particle size, high degree of dispersion, and uniform element distribution in bulk material. In addition, the lower polarization potential accelerates Li⁺ ion migration, and the lower atom location confused degree maintains integrity of crystal structure, both of which can effectively improve the rate capability and cyclability of SG-LMO.     

Thermoeletrochemical study on LiNi<Subscript>0.8</Subscript>Co<Subscript>0.1</Subscript>Mn<Subscript>0.1</Subscript>O<Subscript>2</Subscript> with in situ modification of Li<Subscript>2</Subscript>ZrO<Subscript>3</Subscript>

To improve the electrochemical performance of Nickel-rich cathode material LiNi_0.8Co_0.1Mn_0.1O₂, an in situ coating technique with Li₂ZrO₃ is successfully applied through wet chemical method, and the thermoelectrochemical properties of the coated material at different ambient temperatures and charge-discharge rates are investigated by electrochemical-calorimetric method. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests demonstrate that the Li₂ZrO₃ coating decreases the electrode polarizatoin and reduces the charge transfer resistance of the material during cycling. Moreover, it is found that with the ambient temperatures and charge-discharge rates increase, the specific capacity decreases, the amount of heat increases, and the enthalpy change (ΔH) increases. The specific capacity of the cells at 30 °C are 203.8, 197.4, 184.0, and 174.5 mAh g^?1 at 0.2, 0.5, 1.0, and 2.0 C, respectively. Under the same rate (2.0 C), the amounts of heat of the cells are 381.64, 645.32, and 710.34 mJ at 30, 40, and 50 °C. These results indicate that Li₂ZrO₃ coating plays an important role to enhance the electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ and reveal that choosing suitable temperature and current is critical for solving battery safety problem.     

Low content Ni and Cr co-doped LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> with enhanced capacity retention

Nanoparticles of the pure and Ni–Cr co-doped lithium manganese oxides Li[Ni_xCr_yMn_2-x-y]O₄ (x = y = 0.01–0.05) have been synthesized by sol–gel method using citric acid as a chelating agent. The effect of low-content doping was noted reflecting the faster ionic movement in the cathode material. The phase structure and morphology of the materials are characterized by XRD, FTIR, SEM and TEM. Electrochemical and impedance measurements established that low-content Ni–Cr substitution substantially improves the structural stability and high rate cycling performance of LiMn₂O₄. Among all the investigated compositions, LiNi_0.01Cr_0.01Mn_1.98O₄ demonstrated the best electrochemical performance. At a substantially high current rate of 5 C, 82% of the initial discharge capacity at 0.1 C is retained. Remarkably, after deep cycling at high rates, a discharge capacity of 104 mAhg^?1 is resumed upon reducing the current rate to 0.1 C which is 91% of the specific capacity in the first cycle.     

Influence of cooling mode on the electrochemical properties of Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode materials for lithium-ion batteries

Li₄Ti₅O₁₂ (LTO) was synthesized with two different cooling methods by solid-state method, namely fast cooling and air cooling. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), galvanostatic charge–discharge test, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), respectively. XRD revealed that the basic LTO structure was not changed. FESEM images showed that fast cooling effectively reduced the particle sizes and the agglomeration of particles. Galvanostatic charge–discharge test showed that the air cooling sample exhibited a mediocre performance, having an initial discharge capacity of 136.3mAh?·?g^?1 at 0.5 C; however, the fast cooling sample demonstrated noticeable improvement in both of its discharge capacity and rate capability, with a high initial capacity value of 142.7 mAh?·?g^?1 at 0.5 C. CV measurements also revealed that fast cooling enhanced the reversibility of the LTO. EIS confirmed that fast cooling resulted in lower electrochemical polarization and a higher lithium-ion diffusion coefficient. Therefore, fast cooling have a great impact on discharge capacity, rate capability, and cycling performance of LTO anode materials for lithium-ion batteries.     

Improved electrochemical performance of Li<Subscript>1.2</Subscript>Ni<Subscript>0.2</Subscript>Mn<Subscript>0.6</Subscript>O<Subscript>2</Subscript> cathode material with fast ionic conductor Li<Subscript>3</Subscript>VO<Subscript>4</Subscript> coating

Layered lithium-enriched nickel manganese oxides Li_1.2Ni_0.2Mn_0.6O₂ have been synthesized and coated by fast ionic conductor Li₃VO₄ with varying amounts (1, 3, and 5 wt%) in this paper. The effect of Li₃VO₄ on the physical and electrochemical properties of Li_1.2Ni_0.2Mn_0.6O₂ has been discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), discharge, cyclic performance, rate capability, and electrochemical impedance spectroscopy (EIS). The discharge capacity and coulomb efficiency of Li_1.2Ni_0.2Mn_0.6O₂ in the first cycle have been improved after Li₃VO₄ coating. And, the 3 wt% Li₃VO₄-coated Li_1.2Ni_0.2Mn_0.6O₂ shows the best discharge capacity (246.8 mAh g^?1), capacity retention (97.3 % for 50 cycles), and rate capability (90.4 mAh g^?1 at 10 C). Electrochemical impedance spectroscopy (EIS) results show that the R _ct of Li_1.2Ni_0.2Mn_0.6O₂ electrode decreases after Li₃VO₄ coating, which is due to high lithium ion diffusion coefficient of Li₃VO₄, is responsible for superior rate capability.     

A lithium salt additive Li<Subscript>2</Subscript>ZrF<Subscript>6</Subscript> for enhancing the electrochemical performance of high-voltage LiNi<Subscript>0.5</Subscript>Mn<Subscript>1.5</Subscript>O<Subscript>4</Subscript> cathode

In this work, Li₂ZrF₆, a lithium salt additive, is reported to improve the interface stability of LiNi_0.5Mn_1.5O₄ (LNMO)/electrolyte interface under high voltage (4.9 V vs Li/Li⁺). Li₂ZrF₆ is an effective additive to serve as an in situ surface coating material for high-voltage LNMO half cells. A protective SEI layer is formed on the electrode surface due to the involvement of Li₂ZrF₆ during the formation of SEI layer. Charge/discharge tests show that 0.15 mol L^?1 Li₂ZrF₆ is the optimal concentration for the LiNi_0.5Mn_1.5O₄ electrode and it can improve the cycling performance and rate property of LNMO/Li half cells. The results obtained by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) demonstrate that Li₂ZrF₆ can facilitate the formation of a thin, uniform, and stable solid electrolyte interface (SEI) layer. This layer inhibits the oxidation decomposition of the electrolyte and suppresses the dissolution of the cathode materials, resulting in improved electrochemical performances.     

One-step solid-state synthesis of nanosized LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> cathode material with power properties

A simple one-step solid state reaction way of preparing nanosized LiMn₂O₄ powders with high-rate properties is investigated. Oxalic acid is used as a functional material to lose volatile gases during the process of calcining in order to control the morphology and change the particle size of materials. The results of X-ray diffraction and scanning electron microscopy show that particle size of materials decreases with the increase of the oxalic acid content. The electrochemical test results indicate that optimal LiMn₂O₄ particles (S_0.5) is synthesized when the molar ratios of oxalic acid and total Mn source are 0.5:1. It also manifests that LiMn₂O₄ sample with middle size has the optimal electrochemical performance among five samples instead of the smallest LiMn₂O₄ sample. The obtained sample S_0.5 with middle size exhibits a high initial discharge capacity of 125.8 mAh g^?1 at 0.2C and 91.4% capacity retention over 100 cycles at 0.5C, superior to any one of other samples. In addition, when cycling at the high rate of 10C, the optimal S_0.5 in this work could still reach a discharge capacity of 80.8 mAh g^?1. This observation can be addressed to the fact that the middle size particles balance the contradictory of diffusion length in solid phase and particle agglomeration, which leads to perfect contacts with the conductive additive, considerable apparent Li-ion diffusion rate, and the optimal performance of S_0.5.     

Enhanced electrochemical properties of ZnO-coated LiMnPO<Subscript>4</Subscript> cathode materials for lithium ion batteries

We demonstrated the effect of ZnO (different wt%)-coated LiMnPO₄-based cathode materials for electrochemical lithium ion batteries. ZnO-coated LiMnPO₄ cathode materials were prepared by the sol-gel method. X-ray diffraction (XRD) analysis indicates that there is no change in structure caused by ZnO coating, and field emission scanning electron microscopy (FESEM) images depict the closely packed particles. Galvanostatic charge-discharge tests show the ZnO-coated LiMnPO₄ sample has an enhanced electrochemical performance as compared to pristine LiMnPO₄. The 2 wt% of ZnO-based LiMnPO₄ exhibited maximum discharge capacity of 102.2 mAh g^?1 than pristine LiMnPO₄ (86.2 mAh g^?1) and 1 wt% of ZnO-based LiMnPO₄ (96.3 mAh g^?1). The maximum cyclic stability of 96.3 % was observed in 2 wt% of ZnO-based LiMnPO₄ up to 100 cycles. This work exhibited a promising way to develop a surface-modified LiMnPO₄ using ZnO for enhanced electrochemical performance in device application.     

Modification research of LiAlO<Subscript>2</Subscript>-coated LiNi<Subscript>0.8</Subscript>Co<Subscript>0.1</Subscript>Mn<Subscript>0.1</Subscript>O<Subscript>2</Subscript> as a cathode material for lithium-ion battery

The LiNi_0.8Co_0.1Mn_0.1O₂ with LiAlO₂ coating was obtained by hydrolysis–hydrothermal method. The morphology of the composite was characterized by SEM, TEM, and EDS. The results showed that the LiAlO₂ layer was almost completely covered on the surface of particle, and the thickness of coating was about 8–12 nm. The LiAlO₂ coating suppressed side reaction between composite and electrolyte; thus, the electrochemical performance of the LiAlO₂-coated LiNi_0.8Co_0.1Mn_0.1O₂ was improved at 40 °C. The LiAlO₂-coated sample delivered a high discharge capacity of 181.2 mAh g^?1 (1 C) with 93.5% capacity retention after 100 cycles at room temperature and 87.4% capacity retention after 100 cycles at 40 °C. LiAlO₂-coated material exhibited an excellent cycling stability and thermal stability compared with the pristine material. These works will contribute to the battery structure optimization and design.     

Hierarchical LiMn<Subscript>0.5</Subscript>Fe<Subscript>0.5</Subscript>PO<Subscript>4</Subscript>/C nanorods with excellent electrochemical performance synthesized by rheological phase method as cathode for lithium ion battery

The hierarchical LiMn_0.5Fe_0.5PO₄/C (LMFP) nanorods were first successfully synthesized by rheological phase method using polyethylene glycol 4000 (PEG 4000) as a template reagent. The physical and electrochemical properties of the LiMn_0.5Fe_0.5PO₄/C were characterized by TG-DTG, XRD, FTIR, SEM, TEM, EIS and galvanostatic charge-discharge measurements. The results reveal that the PEG-LMFP/C synthesized with the assistance of PEG 4000 shows unique bundle-type shape assembled of nanorods, while the LMFP/C synthesized without PEG 4000 presents a platelet-like shape with some agglomeration. Besides, a uniformly carbon layer coating on the surface of the PEG-LMFP/C can be seen from TEM images. The PEG-LMFP/C exhibits high specific capacity and superior rate performance with discharge capacities of 162, 133, 108, 95, and 78 mAh?·?g^?1 at 0.1, 1, 5, 10, and 20 C rates, respectively. It is demonstrated that the synthesis of LMFP/C with PEG 4000 can significantly decrease the characteristic sizes of the crystals, resulting in improved electrochemical performance.     

Influence of co-precipitation temperature on microstructure and electrochemical properties of Li[Li<Subscript>0.2</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

The layered Li-rich Mn-based cathode materials Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ were prepared by using co-precipitation technique at different temperatures, and their crystal microstructure and particle morphology were observed and analyzed by XRD and SEM. The electrochemical properties of these samples were investigated by using charge-discharge tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), respectively. The results indicated that all samples are of high purity. When the precursors were co-precipitated at 50 °C, their cathode materials have the most uniform and full particles and exhibit the highest initial discharge capacity (289.4 mAh/g at 0.1C), the best cycle stability (capacity retention rate of 91.2 % after 100 cycles at 0.5C), and the best rate performance. The EIS results show that the lower charge transfer resistance of 50 °C sample is responsible for its superior discharge capacity and rate performance.     

Synthesis and lithium-ion storage performances of LiFe<Subscript>0.5</Subscript>Co<Subscript>0.5</Subscript>PO<Subscript>4</Subscript>/C nanoplatelets and nanorods

Carbon-coated olivine-structured LiFe_0.5Co_0.5PO₄ solid solution was synthesized by a facile rheological phase method and applied as cathode materials of lithium-ion batteries. The nanostructure’s properties, such as morphology, component, and crystal structure for the samples, characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer, Emmett, and Teller (BET) determination, X-ray photoelectron spectroscopy (XPS), and the electrochemical performances were evaluated using constant current charge/discharge tests and electrochemical impedance spectroscopy (EIS). The results indicate that nanoplatelet- and nanorod-structured LiFe_0.5Co_0.5PO₄/C composites were separately obtained using stearic acid or polyethylene glycol 400 (PEG400) as carbon source, and the surfaces of particles for the two samples are ideally covered by full and uniform carbon layer, which is beneficial to improving the electrochemical behaviors. Electrochemical tests verify that the nanoplatelet LiFe_0.5Co_0.5PO₄/C shows a better capacity capability, delivering a discharge specific capacity of 133.8, 112.1, 98.3, and 74.4 mAh g^?1 at 0.1, 0.5, 1, and 5 C rate (1 C?=?150 mA g^?1); the corresponding cycle number is 5th, 11th, 15th, 20th, and 30th, respectively, whereas the nanorod one possesses more excellent cycling ability, with a discharge capacity of 83.3 mAh g^?1 and capacity retention of 86.9% still maintained after cycling for 100 cycles at 0.5 C. Results from the present study demonstrate that the LiFe_0.5Co_0.5PO₄ solid solution nanomaterials with favorable carbon coating effect combine the characteristics and advantage of LiFePO₄ and LiCoPO₄, thus displaying a tremendous potential as cathode of lithium-ion battery.     

Acacia gum-assisted co-precipitating synthesis of LiNi<Subscript>0.5</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.3</Subscript>O<Subscript>2</Subscript> cathode material for lithium ion batteries

LiNi_0.5Co_0.2Mn_0.3O₂ particles of uniform size were prepared through carbonate co-precipitation method with acacia gum. The precursor of carbonate mixture was calcined at 800 °C, and a well-crystallized Ni-rich layered oxide was got. The phase structure and morphology were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The micro-sized particles delivered high initial discharge capacity of 164.3 mA h g^?1 at 0.5 C (1 C?=?200 mA g^?1) between 2.5 and 4.3 V with capacity retention of 87.5 % after 100 cycles. High reversible discharge capacities of 172.4 and 131.4 mA h g^?1 were obtained at current density of 0.1 and 5 C, respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to further study the LiNi_0.5Co_0.2Mn_0.3O₂ particles. Anyway, the excellent electrochemical performances of LiNi_0.5Co_0.2Mn_0.3O₂ sample should be attributed to the use of acacia gum.     

Hydrothermal synthesis of pure LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> from nanostructured MnO<Subscript>2</Subscript> precursors for aqueous hybrid supercapacitors

Pure LiMn₂O₄ samples with high crystallinity (LMO-1# and LMO-2#) were successfully synthesized by a facile hydrothermal method using δ-MnO₂ nanoflowers and α-MnO₂ nanowires as the precursors. The as-prepared samples were analyzed by XRD, SEM, and Brunauer-Emmett-Teller (BET), and their capacitive properties were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge test. Two LiMn₂O₄ samples showed good capacitive behavior in aqueous hybrid supercapacitors. AC//LMO-1# and AC//LMO-2# delivered the initial specific capacitance of 45.4 and 40.7 F g^?1 in 1 M Li₂SO₄ electrolyte at a current density of 200 mA g^?1 in the potential range of 0～1.5 V, respectively. After 1000 cycles, the capacitance retention was 97.6% for AC//LMO-1# and 93.7% for AC//LMO-2#. Obviously, LMO-1# from δ-MnO₂ nanoflowers exhibited higher specific capacitance and better cycling performance than LMO-2#, so LMO-1# was more suitable as the positive electrode material in hybrid supercapacitors.     

Electrochemical properties of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> prepared with tartaric acid chelating agent

Lithium manganese oxide (LiMn₂O₄) has been prepared using sol-gel technique under acidic (pH = 5.8) and alkaline (pH = 9) conditions with tartaric acid as chelating agent. X-ray studies show that under acidic condition, an Mn₂O₃ peak was observed indicating the presence of impurities. No impurity was observed for LiMn₂O₄ under alkaline conditions. The particle size is mostly in the range of 124 to 185 nm from HR-TEM. The lithium diffusion coefficient, D _Li+ in LiMn₂O₄ is of the order 10^?9 cm² s^?1. By using density functional theory (DFT) calculations, structural properties have been obtained. The specific discharge capacity of the cells with LiMn₂O₄ prepared under alkaline condition and with LiMn₂O₄ prepared under acidic condition discharged at 0.5 C is in the ranges of 132 to 142 and 128 to 139 mAh g^?1, respectively.     

Pr-modified Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> nanofibers as an anode material for lithium-ion batteries with outstanding cycling performance and rate performance

Pr-doped Li₄Ti₅O₁₂ in the form of Li_4?x/3Ti_5?2x/3Pr_xO₁₂ (x = 0, 0.01, 0.03, 0.05, and 0.07) was synthesized successfully by an electrospinning technique. ICP shows that the doped samples are closed to the targeted samples. XRD analysis demonstrates that traces of Pr³⁺ can enlarge the lattice parameter of Li₄Ti₅O₁₂ from 8.3403 to 8.3765 Å without changing the spinel structure. The increase of lattice parameter is beneficial to the intercalation and de-intercalation of lithium-ion. XPS results identify the existence form of Ti is mainly Ti⁴⁺ and Ti³⁺ in minor quantity in Li_4?x/3Ti_5?2x/3Pr_xO₁₂ (x = 0.05) samples due to the small amount of Pr³⁺. The transition from Ti⁴⁺ to Ti³⁺ is conducive to the electronic conductivity of Li₄Ti₅O₁₂. FESEM images show that all the nanofibers are well crystallized with a diameter of about 200 nm and distributed uniformly. The results of electrochemical measurement reveal that the 1D Li_4?x/3Ti_5?2x/3Pr_xO₁₂ (x = 0.05) nanofibers display enhanced high-rate capability and cycling stability compared with that of undoped nanofibers. The high-rate discharge capacity of the Li_4?x/3Ti_5?2x/3Pr_xO₁₂ (x = 0.05) samples is excellent (101.6 mAh g^?1 at 50 °C), which is about 58.48 % of the discharge capacity at 0.2 °C and 4.3 times than that of the bare Li₄Ti₅O₁₂ (23.5 mA g^?1). Even at 10 °C (1750 mA g^?1), the specific discharge capacity is still 112.8 mAh g^?1 after 1000 cycles (87.9 % of the initial discharge capacity). The results of cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) illustrate that the Pr-doped Li₄Ti₅O₁₂ electrodes possess better dynamic performance than the pure Li₄Ti₅O₁₂, further confirming the excellent electrochemical properties above.     

Surfactant-assisted synthesis of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> particles as high-rate and long-life cathode materials for lithium-ion batteries

Herein, we reported the synthesis of uniform LiMn₂O₄ submicroparticles by surfactant-assisted preparation of spherical MnCO₃ precursor followed by solid-state reaction. Polyethylene glycol (Mw = 1000) was used as surfactant to control the morphology and size of the MnCO₃ precursor as well as the MnO₂ intermediate and LiMn₂O₄ product. The influence of particle size, homogeneity, and crystallinity on the electrochemical performance of LiMn₂O₄ was intensively investigated. The test results indicate that the LiMn₂O₄ sample using polyethylene glycol with weight as 10% of reactants shows the best rate capability and long-term cyclability. Due to the homogeneous particles with the average size of ca. 250 nm and high crystallinity, the discharge capacities are as high as 125, 118, 114, and 100 mAh g^?1 at 1, 10, 20, and 50 C rates, respectively, along with high capacity retention of 74% after 1000 cycles at 20 C.     

CeO<Subscript>2</Subscript> coating to improve the performance of Li[Li<Subscript>0.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>]O<Subscript>2</Subscript>

The Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ coated with CeO₂ has been fabricated by an ionic interfusion method. Both the bare and the CeO₂-coated samples have a typical layered structure with R-3m and C2/m space group. The results of XRD and TEM images display that the CeO₂ coating layer on the precursor could enhance the growth of electrochemically active surface planes ((010), (110), and (100) planes) in the following ionic interfusion process. The results of galvanostatic cycling tests demonstrate that the CeO₂-coated sample has a discharge capacity of 261.81 mAh g^?1 with an increased initial Coulombic efficiency from 62.4 to 69.1% at 0.05 °C compared with that of bare sample and delivers an improved capacity retention from 71.7 to 83.4% after 100 cycles at 1 °C (1 °C?=?250 mA g^?1). The results of electrochemical performances confirm that the surface modification sample exhibits less capacity fading, lower voltage decay, and less polarization.