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Spinel LiMn2O4 is one of the most important cathode materials but it still suffers from rapid capacity degradation during electrochemical cycling. Beside surface coating to improve the electrochemical performances, controlling the bulk morphology of LiMn2O4 (LMO) is another effective strategy. In this work, porous LiMn2O4 microspheres composed of numerous primary nanoparticles are synthesized by micro-emulsion and co-precipitation methods. The porous structure and the primary nanoparticles size of LiMn2O4 are effected by the concentration of micro-emulsion and the precursor of Mn2+. The well-established porous LiMn2O4 microspheres with abundant ionic channels and good contact with electrolyte endow the spinel a remarkable electrochemical performance. After 300 cycles, 0.50 M-LMO sample presents excellent reversible capacity of 112.8 mAh g−1 at 0.5 C rate. After 1000 cycles, 0.50 M-LMO sample presents the highest capacity of 97.9 mAh g−1 and remains 54.2 mAh g−1 at the current rate of 10 C. The porous spherical structure of cathode materials is essential to improve the rate performance due to the good contact between the active material and electrolyte. [ABSTRACT FROM AUTHOR]

In this paper, a novel adhesive prepared by blending lithium-ion functionalized epoxy resin (ionized oligomer) with poly(vinylidenedifluoride) (PVdF) is used to fabricate the cathode electrode of LiCoO2. The properties of the blending adhesive are studied by Fourier transform infrared spectroscopy, differential scanning calorimeter, and thermogravimetric analysis, and the morphology and performance of the composite cathodes are characterized by using X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy, electrochemical impedance spectroscopy, and galvanostatic charge-discharge. With the blended ionized oligomer, the crystallinity behavior of PVdF is decreased effectively, which will be beneficial to the movement of conducting ions. An appropriate amount of ionized oligomer effectively improves the conductivity and charge-transfer capability of the cathode material. When the amount of ionized oligomer to the PVdF binder is 10 wt%, the LiCoO2-based composite cathode delivers the highest charge−discharge capacity (178 mAh g−1) and the capacity retention is up to 82.2 % after 100 cycles. [ABSTRACT FROM AUTHOR]

Abstract: Olivine structure LiMnPO4 has been considered as one of the very promising electrodes for lithium-ion batteries because of their low cost, low toxicity and high voltage plateau compared with LiFePO4. In order to improve the electrochemical performance a key challenge in the field of lithium-ion battery, is to explore and invent suitable synthetic route to control the size and morphology of LiMnPO4. Here a detailed study exploring the novel route of microwave-hydrothermal (MH) synthesis for successfully obtaining LiMnPO4 crystals within few minutes is reported and the reaction process discussed in detail. Variation of the synthetic parameters show that a decrease in reactant concentration could lead to LiMnPO4 nano-platelets orientated in the ac plane with a very high electrochemical performance. The effect of the starting precursor (like, Mn) concentration as a means to tailor LiMnPO4 electrochemical performance is discussed. The effect of alteration of size, morphology, lattice parameters and crystal structure induced by addition of additives like citric acid (H3cit) and sodium dodecyl benzene sulfonate (SDBS) is further described and an example of the first reversible discharge of a product treated with H3cit obtained by MH route as high as 89.0mAh/g, is shown. The general investigation demonstrates that there is a relationship among microwave irradiation condition, crystal structure, morphology and electrochemical performance that can be exploited for the design of next generation lithium batteries. [Copyright &y& Elsevier]

Abstract: To investigate the crystal structure and electrochemical performance of samples synthesized under different microwave solid-state synthesis condition, a series of Li3V2(PO4)3 samples has been synthesized at five different temperatures for 3–5min and at 750°C for various time. The as-synthesized Li3V2(PO4)3 samples are characterized and studied by ICP-AES analysis, X-ray diffraction (XRD), Rietveld analysis, scanning and transmission electron microcopy (SEM and TEM). At relatively lower temperature (650°C) and very short reaction time (3min), pure phase of Li3V2(PO4)3 could be synthesized in microwave irradiation field. The crystal structure and Li atomic fractional coordinate present a significant deviation upon the change of microwave irradiation temperature and time. Relatively, the diffusion ability of lithium cations and the electrochemical performance are affected. Under the proper reaction temperature and time, the carbon-free samples MW750C5m and MW850C3m show the best specific discharge capacity 126.4 and 132mAhg−1 at the voltage range of 3.0–4.3V, near the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133mAhg−1). At the voltage range of 3–4.8V, the sample MW750C5m presents the best initial specific charge capacity of 197mAhg−1, equivalent to the reversible cycling of three lithium ions per Li3V2(PO4)3 formula unit (197mAhg−1). The initial discharge capacity, the samples MW750C5m and MW850C3m present high specific discharge capacity 183.4 and 175.7mAhg−1, respectively. The relationship among microwave irradiation condition, crystal structure, lithium atomic fractional coordinates and the electrochemical performance have been discussed in detail. [Copyright &y& Elsevier]

Abstract: Rod-like orthorhombic LiMnO2 nanocrystals were successfully synthesized using temperature-controlled microwave hydrothermal route (TCMH) in a short time (30min) at a temperature as low as 160°C. o-LiMnO2 obtained by two different methods was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemistry test. SEM revealed that the product obtained in case of TCMH was rod-like with a diameter of 40nm, while the nanoparticles with 200nm diameter were obtained by traditional hydrothermal route (TH). The dramatic formation of o-LiMnO2 in the microwave hydrothermal field influenced the morphology and crystal structure of the final products. The formation and preferred growth orientation mechanism of o-LiMnO2 in the microwave irradiation process was discussed. Electrochemistry performance exhibited that the as-synthesized o-LiMnO2 nanorods reached the maximum discharge capacity of 194.2mAhg−1 at 0.1C rate after several cycles between 2.2 and 4.4V vs. Li+/Li at room temperature, which was higher than the electrochemical performance of o-LiMnO2 obtained by TH. The experimental results showed that the TCMH method provided an effective way for preparing o-LiMnO2 cathode material in lithium-ion batteries. [Copyright &y& Elsevier]

Abstract: Monoclinic Li3V2(PO4)3 can be rapidly synthesized at 750°C for 5min (MW5m) by using temperature-controlled microwave solid-state synthesis method (TCMS). The carbon-free sample MW5m presents well electrochemical properties. In the cut-off voltage 3.0–4.3, MW5m presents a charge capacity 132mAhg−1, almost equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133mAhg−1), and discharge capacity 126.4mAhg−1. In the cut-off voltage 3.0–4.8V, MW5m shows an initial discharge capacity of 183.4mAhg−1, near to the theoretical discharge capacity. In the cycle performance, the capacity fade of Li3V2(PO4)3 is dependent on the cut-off voltage and the preparation method. [Copyright &y& Elsevier]

Abstract Li 1.147 K 0.026 Mn 0.582 Ni 0.25 O 2 (LKMNO) sample is successfully prepared by doping K+ ions into Li slab without changing the original structure of Li 1.167 Mn 0.575 Ni 0.25 O 2 (LMNO). LKMNO sample delivers the capacities of 160.2 and 135.1 mAh g−1 at 1 and 5 C rates, respectively, but LMNO sample only delivers 135.1 and 0 mAh g−1. After 100 cycles at 1 C rate, LMNO and LKMNO samples respectively remain 67.4% and 93.0% of their initial capacities. The effects of K+ doping on the relationship between the charging-discharging process and phase change are detailed studied by the incremental capacity curves (d Q/ d V) at the various cycles. K+ doping in LKMNO sample plays an essential role in rate performance and cyclic performance, because it effectively hinders the formation of spinel structure and stabilizes the host layered structure. Considering the irreversible extraction of Li and O from the Li 2 MnO 3 region occurred beyond 4.6 V, after the charging/discharging are collected for 1–5 cycles at 2.5–4.9 V and 6–300 cycles at 2.5–4.6 V, LKMNO sample further reveals a remarkable improvement in cycling performance. In the full cell state (pouch cell), the discharge capacity of LKMNO is 194.6 and 115.4 mAh g−1 at 0.1 and 1 C rates, respectively, which are much higher than 175.5 and 79.7 mAh g−1 of LMNO sample. The capacity retention of LMNO and LKMNO samples is respective 48.8% and 74.9% of their initial capacity after 100 cycles. Graphical abstract Image 1 Highlights • Li 1.147 K 0.026 Mn 0.582 Ni 0.25 O 2 is successfully prepared by doping K+ into Li slab. • K+ doping results in Mn3+ state and is essential in rate and cyclic performance. • After 100 cycle LMNO and LKMNO remain 67.4% and 93.0% of their initial capacities. • K+ doping hinders the formation spinel structure and stabilizes the host structure. • In full cell LKMNO delivers two times capacity than LMNO at 1 C rate. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) contain a variety of toxic inorganic and organic compounds, and the spent cathode materials are high quality resources of Ni, Co, Mn, and Li elements. In this case, how to efficiently deal with spent materials has become an urgent problem. In this work, the regeneration of spent ternary materials via molten salt solid-liquid method and traditional solid-solid method are studied comparatively. Ordered and uniform crystals in MS-NCM are successfully grown in liquid medium of molten salts. The regenerated TS-NCM by traditional sintering method still presents inhomogeneous larger and smaller crystals. Moreover, only regeneration by molten salt method effectively removes F-contained impurity on the surface of spent materials, and the Ni3+ and Mn3+ on the crystal surface of MS-NCM are close to the values in commercial sample (Com-NCM). After 100 cycles at 0.2 C rate, MS-NCM and TS-NCM respectively deliver 149.1 mA h g−1 and 123.2 mA h g−1, maintaining 98.1% and 84.4% of their initial capacity. MS-NCM presenting better electrochemical performance than TS-NCM is attributed to the efficient regeneration of the spent cathode material in liquid medium of molten salts. [Display omitted] • Spent NCM regeneration via solid-liquid better than traditional via solid-solid. • Uniform NCM crystals successfully re-grown in liquid medium of molten salts. • Regeneration in molten salts effectively supplement Li+ and remove F-impurity. • MS-NCM delivers much higher capacity than TS-NCM after 100 cycle. [ABSTRACT FROM AUTHOR]

Abstract: To substitute minor Mn2+ by the transition metal ion M=Mg2+, V3+, Fe2+, Co2+, or Gd3+, LiMn0.95M0.05PO4 samples are synthesized by a solid-state reaction route. The interpretation of doping effects is complicated by the interrelations between doping microstructure and morphology, because the crystal structure would be affected by the doped elements. The lattice structure and deviation of Li–O bond lengths of the doped LiMnPO4 are refined by XRD refinement. All the samples present a couple of oxidation and reduction peaks in cyclic voltammetry, corresponding to a redox Mn3+/Mn2+ reaction coupled with the extraction/reinsertion process of Li+ in LiMnPO4 structure. During charge/discharge process, the electron flowing and Li+ cation diffusion in the various doped LiMnPO4 samples should be different thermodynamic and kinetic process. For further studying which step in thermodynamic and kinetic process would affect or control the electrochemical performance, the initial charge/discharge capacities and cycleability of doped LiMnPO4 samples are obtained under different voltage range (from 2.7 to the upper cut-off voltage 4.4, 4.6 and 4.8V, respectively) and different environment temperatures (0, 25, and 50°C). At relative higher measuring temperature, the discharge capacity of Co-doped LiMnPO4 shows 151.9mAhg−1. [Copyright &y& Elsevier]

Lithium-rich cathode materials have the potential for applications in high energy lithium-ion batteries, but they suffer from a low rate performance and an inferior cycling stability. In this work, Li 1.167- x K x Mn 0.583 Ni 0·25 O 2 (x = 0, 0.025, 0.05 and 0.075) samples are synthesized and characterized. In addition, K+ doping results in small perturbations in the crystal structure of Li 1.167- x K x Mn 0.583 Ni 0·25 O 2 , such as the Li–O bond lengths, lattice parameters and the oxidation states of manganese, which effectively improves the lithium diffusion ability and hinders the detrimental interphase growth of the spinel phase during cycling. In a half-cell, Li 1·117 K 0·05 Mn 0·583 Ni 0·25 O 2 (LK2MNO) with an optimized doping quantity of K+ delivers the best capacities of 152.0 mAh g−1 after 100 cycles at a 1C rate and 82.9 mAh g−1 after 300 cycles at a 10C rate, in comparison with Li 1·167 Mn 0·583 Ni 0·25 O 2 , which has a capacity of only 126.0 and 33.3 mAh g−1. In the full-cell with graphite as the negative electrode, LK2MNO delivers an initial capacity of 249.9 mAh g−1 at a 0.1C rate and retains 90.8% of its initial capacity after 100 cycles. The surface chemical states of the positive electrode and negative electrodes after 100 cycles is studied by ex situ SEM and XPS measurements, and the results reveal that an appropriate K+ doping amount effectively hinders the dissolution of Mn2+ from the cathode material and decreases the decomposition of electrolytes to some degree. K+ doping in Mn-based lithium-rich cathode materials improves the lithium diffusion ability and hinders the detrimental interphase growth of the spinel phase during cycling. In full cell, the LK2MNO sample delivers an initial capacity of 249.9 mAh g−1 at a 0.1C rate and retains 90.8% of its initial capacity after 100 cycles. The surface chemical state of the positive and negative electrodes after 100 cycles reveal that K+ doping effectively suppresses side reactions and electrolyte decomposition. Image 1 • K+ doping results in small perturbations in Li 1.167- x K x Mn 0.583 Ni 0·25 O 2 structure. • Potassium doping decreases the detrimental interphase growth of spinel phase during cycling. • Expanding interlayer spacing by K+ provide fast conductive channel for Li+ diffusion. • LK2MNO delivers 249.9 mAh g−1 and remains 90.8% of initial capacity after 100 cycles. • K+ doping suppresses side reactions and electrolyte decomposition during cycling. [ABSTRACT FROM AUTHOR]