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In this work, nanorod lithium iron phosphate (LiFePO₄) materials are synthesized by a liquid-phase method using iron powder, H₃PO₄, and LiOH$\cdot$H₂O as source materials. The crystal structure, morphology and electrochemical performance are characterized. The results illustrate that the molar ratio of Li:Fe:P plays a significant role in regulating the morphology and structure of LiFePO₄. When the molar ratio is Li:Fe:P $=$ 3:1:1 it shows irregular nanoparticles, and when the molar ratio is Li:Fe:P $=$ 3:1:1.5 it transforms into rod-like particles. Furtherly, The LiFePO₄/C (Li:Fe:P $=$ 3:1:1.5) material, adding carbon coating at 180${}^{\circ }$C for 12h, displays a discharge capacity of 120mAh/g at 1C, and even after 200 cycles with the capacity retention of above 95.7%. Our findings provide a simple, economical and environmentally friendly way to produce LiFePO₄ cathode material for outstanding performance in lithium-ion battery (LIB).

${\mathrm{\text{LiFePO}}}_4/\mathrm{\text{C}}$ samples were obtained via high-temperature ball milling route with different mixing processes. Ultrasonic radiation and wet mechanical agitation were used as mixing processes, respectively. The effects of different mixing processes on the structure and electrochemical performance of ${\mathrm{\text{LiFePO}}}_4/\mathrm{\text{C}}$ were investigated. The results exhibited that ${\mathrm{\text{LiFePO}}}_4/\mathrm{\text{C}}$ prepared by high-temperature ball milling with ultrasonic irradiation as mixing processes displayed the best rate capability and cycle stability among all the samples: it delivered discharge capacities of $151\pm 2$ (0.1 C), $112\pm 2$ (5.0 C) and $99\pm 2$ (10 C) ${\mathrm{\text{mAh g}}}^{-1}$, respectively. The discharge capacity was $136\pm 2$${\mathrm{\text{mAh g}}}^{-1}$ at 0.5 C-rate over 100 cycles with capacity retention of 95.0%. It is concluded that ultrasonic irradiation is an effective mixing process for the preparation of ${\mathrm{\text{LiFePO}}}_4$ cathode material via high-temperature ball milling route.

It was precisely because LiNi${}_{0.5}$Mn${}_{1.5}$O₄ cathode material had many advantages, including high voltage, high power, no pollution, low cost, etc., that it became a research hotspot for lithium-ion cathode materials. Although LiNi${}_{0.5}$Mn${}_{1.5}$O₄ has a three-dimensional Li${}^{+}$ diffusion channel, there are still some problems that lead to capacity decay and reduced cycling stability, limiting its commercial application. In this paper, the LiNi${}_{0.5}$Mn${}_{1.5}$O₄ cathode material was prepared by the freezing precipitation method. We studied the effects of different drying methods, such as blast drying, water bath drying and freeze-drying on the structure, morphology and electrochemical properties of LiNi${}_{0.5}$Mn${}_{1.5}$O₄ cathode materials. The study found that the LiNi${}_{0.5}$Mn${}_{1.5}$O₄ cathode material prepared by the precipitation-freeze-drying method had a complete crystal form, a stable structure and no Li_xNi${}_{1-x}$O impurity peak. The SEM image showed that the particles were smaller and had a smooth surface. The initial discharge-specific capacity at 0.1C was 105.2mAh⋅g${}^{-1}$. After 50 cycles, its specific discharge capacity was 99.4mAh⋅g${}^{-1}$ and the capacity retention rate was 94.5%. Compared with LiNi${}_{0.5}$Mn${}_{1.5}$O₄ materials prepared by other methods, it had better electrochemical performance.

Single-crystal precursor of hybrid oxides NiO–MnCo₂O₄–Ni₆MnO₈ (SCNCM) is synthesized via an improved continuous two-step spray pyrolysis system (CTSP). This kind of mixed oxide is to be regarded as an ideal precursor for the single-crystal Ni-rich Li[Ni${}_{0.6}$Co${}_{0.2}$Mn${}_{0.2}$]O₂ cathode materials (SCLNCM). The new pilot plant (30 t/a), method, and chlorate in this work could extremely improve the lengthy process, reducing segregation of metal element, excessive sintering temperature, high water consumption, non-polluting, and production efficiency of the SCLNCM. The resulting SCLNCM powders have a type of fine particle size and porous structure with a typical $\alpha$-NaFeO₂ lamellar structure. It also has a type of better cyclic stability, safety, rate capability, crystallinity, and surface area than polycrystalline cathode materials. It delivers an initial discharge capacity of 184 mAh/g at 0.1 C (18 mA/g) with a capacity retention of 91% after 100 cycles in the voltage window of 2.8–4.3 V.

The high nickel ternary LiNi${}_{0.8}$Co${}_{0.1}$Mn${}_{0.1}$O₂ (NCM811) cathode material has attracted much attention owing to its advantages of high capacity and low price. However, NCM811 suffers from surface side reactions and cation mixing, which results in an unstable crystal structure and lower Coulomb efficiency and capacity in lithium ion batteries. In this work, Mo-doped cathode material NCM811 is effectively synthesized by high-temperature solidification approach. The characterization results show that the doped NCM811 can form a coating layer on the surface, preventing electrolyte side reactions with the electrode. As the cathode for lithium ion batteries, the Mo-doped NCM811 electrode shows an initial discharge capacity of 185.21mAh/g and obtains 156.33mAh/g with a capacity retention of 84.5% after 100 cycles at 1C. This study provides a simple and reliable method of fabricating high-performance NCM811 cathode materials.

In this paper, polyaniline/FeFe(CN)₆(PANI-FeFe(CN)₆) composites were prepared by a simple in-situ oxidation polymerization in perchloric acid (HClO₄) solution in which the obtained polyaniline (PANI) self-assembled to form the tube-like morphology, while FeFe(CN)₆ with perfect face-centered cubic lattice (FCC)-type structure was well-dispersed in the obtained PANI matrix. As the cathode of lithium ion battery, PANI-FeFe(CN)₆ composite demonstrates the improved specific capacity, cycling stability and current rate performances. For PANI-FeFe(CN)₆ composite prepared by feed mass ratio of FeFe(CN)${}_{6:}$ Aniline to 80:100 (PANI-FeFe(CN)₆(80%)), it still remained 95.7mAh/g of discharge capacity after 100 cycles, indicating its excellent cycling performances. Especially, its specific capacities were 95.9, 98.8, 91.4, 83.6 and 72mAh/g at the current density of 20, 50, 100, 200 and 500mA/g, which were obviously higher than that of PANI or FeFe(CN)₆, respectively. The improved thermal stability and electrochemical performances for PANI-FeFe(CN)₆ composites could be ascribed to the formed interaction between PANI and FeFe(CN)₆ components and the enhanced electrical conductivity, which made it a potential candidate as the cathode of lithium battery.

To overcome the structural failure of Manganese-based Prussian blue analogue (Mn-HCF) as a cathode material of sodium ion batteries caused by Mn ion dissolution induced by Jahn–Teller effect, we coated Mn-HCF with iron-based Prussian blue (Fe-HCF) to prepare the core–shell Mn-HCF@Fe-HCF cathode material for sodium ion batteries through co-precipitation method. The research results indicate that this structure effectively blocks the direct contact between Mn-HCF and electrolyte, thereby minimizing the dissolution of ${\text{Mn}}^{3+}$ in the electrolyte and significantly improving the cycling stability and rate performance. The discharge capacity of this material at a current density of 0.1C (14mA${\text{g}}^{-1})$ is 129.7mAh${\text{g}}^{-1}$. It still has a capacity of 87.4mAh${\text{g}}^{-1}$ at a current density of 2C (280mA${\text{g}}^{-1})$, and still has a capacity retention rate of 84.3% (91mAh${\text{g}}^{-1})$ after 100 cycles at a current density of 0.5C (70mA${\text{g}}^{-1})$. Compared with the capacity retention rate of 51.5% of Mn-HCF 100 cycles before coating, the cycle stability of Mn-HCF@Fe-HCF is greatly improved.

The LiFePO₄/C composite was prepared by carbothermal reduction method (CTR) with FePO₄ ⋅ 2H₂O, Li₂CO₃ as starting materials, and acetylene black or polyethylene glycol (PEG; mean molecular weight of 10,000) as carbon sources. The structural and electrochemical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), and charge–discharge tests. The results showed that LiFePO₄/C is olivine-type phase, and the addition of carbon reduced the LiFePO₄ grain size with uniform distribution. The carbon is dispersed between the grains, forming a good electronic contact. The synthesized LiFePO₄ composites showed excellent electrochemical performance with initial discharge capacity of 161, 142 and 96 mAh ⋅ g^-1 at 0.1 C, 1 C and 5 C, respectively and displays a robust rate capacity and stable cycling life.

The cathode materials Li_1.05Cr_xMn_1.95-xO₄(x = 0, 0.05, 0.10) for lithium ion batteries were synthesized by sol–gel method and calcined at 650, 700 and 750°C, respectively. The synthesized materials were characterized with X-ray diffraction (XRD). The electrochemical performances of the materials were tested by constant-current cyclic testing at room temperature for 38 cycles. The XRD results showed that the samples of cathode materials synthesized by the method possessed pure spinel phase. The Li_1.05Cr_0.1Mn_1.85O₄ powder with better cyclic performance of initial specific discharge capacity of 113.7 mAh ⋅ g^-1 can be obtained at the calcination temperature of 700°C for 12 h, with an capacity retention of 95.5% after 38 cycles. It was evident that codoping of Li⁺ and Cr³⁺ can improve the stability of spinel structure and cycling performance.

In this work, we present an evaluation of the layered perovskite materials with chemical composition GdBaCo_2-xFe_xO_5.5-δ (x = 0.0, 0.3, 0.6) as a cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC). We first present results concerning their crystal structure and oxygen nonstoichiometry, and then give results concerning their electrical conductivity and performance in button-type SOFCs.

Lithium silicates Li₂MnSiO₄ (where M is a 3d metal) with their theoretical capacity up to 333 mAh⋅g^-1 and high chemical stability, thanks to a presence of strong covalent bonds Si–O, seem to be a good potential cathode material for Li-ion batteries. The main drawback of those materials is their low electric conductivity which can be enhanced by coating the material with conductive carbon layer (CCL). This work concerns the synthesis of CCL/Li₂MnSiO₄ composite material and investigation of its physicochemical properties. The material was successfully produced using sol-gel Pechini method. In order to find the best way of receiving Li₂MnSiO₄ product various synthesis conditions were applied. CCL/Li₂MnSiO₄ composite was produced in a one-step process using organic precursor matrix as a source of carbon. Both Li₂MnSiO₄ material and CCL/Li₂MnSiO₄ composite were investigated using thermal analysis (EGA-TGA/DTG/SDTA), X-ray diffraction (XRD) and electrical conductivity measurements to find the relations between structure, morphology and electrochemical properties.

The effect of annealing of nanosized LiFePO₄ powder on microstructure, phase composition, iron valence state and electrical conductivity has been studied. Careful microstructural characterization of the as-prepared powder using high resolution TEM revealed presence of {010}-type crystal planes at the surface of crystallites, which seem to be beneficial to electrochemical activity. The second part of the work is focused on explanation of presence and evolution of Fe³⁺ detected in the material. Transmission and CEMS modes of Mössbauer spectroscopy together with TEM allowed for ruling out concept of amorphous layers containing Fe³⁺ ions covering crystalline LiFePO₄ grains.

Many transition-metal oxides in elevated valence states [e.g. Mn(V), Co(IV), Ni(III), Cu(III)] present a metastable character and, given the difficulty of their synthesis, have been relatively little studied. However, they are very interesting materials presenting strong electronic correlations that are bound to exotic properties such as superconductivity, metal behavior, metal–insulator transitions or colossal magnetoresistance. The metastability of these compounds requires special synthesis conditions such as the application of high pressure. In the last years, we have prepared and investigated a good number of materials belonging to several families such as RNiO₃ (R = rare earths), Ba₃Mn₂O₈, (Ba,Sr)CoO₃, La₂(Ni,Co)O_4+δ, etc. In the study and correct characterization of these oxides it has been decisive the use of elastic neutron diffraction, most of the times in powder samples. This technique has allowed us to access the structural details typically related to the octahedral tilting in perovskite structures, the oxygen stoichiometry and order–disorder of the oxygen sublattice, the distinction between close elements in the Periodic Table, the resolution of magnetic structures and, in general, the establishment of a correlation between the structure and the properties of interest. This letter is organized around the binomial "high-pressure synthesis" and "characterization by neutron diffraction" and illustrated with some selected examples among the metastable materials above mentioned.

Hollandite-type MnO₂ and its Co-substituted samples have been synthesized by hydrothermal method from MnSO₄, CoSO₄ and K₂S₂O₈ solutions. The hydrothermal products from MnSO₄ and K₂S₂O₈ solutions consisted of the hollandite-type [2 × 2] tunnel structure at 100°C–150°C for 12 h, which was transformed to pyrolusite-type [1 × 1] tunnel structure by hydrothermal treatment at 150°C for longer times of 24–48 h or at a higher temperature of 180°C. On the other hand, the hydrothermal products from MnSO₄, CoSO₄ and K₂S₂O₈ solutions at 150°C–180°C for 12–48 h consisted of the hollandite-type MnO₂ phase. The Co-substituted samples showed higher initial discharge capacity (180–200 mAh (g-oxide)^-1) than that of non-substituted hollandite-type MnO₂ (130–160 mAh (g-oxide)^-1) at 50 mA g^-1.

Polyanionic cathode materials for lithium-ion batteries start to be considered as potential alternative for layered oxide materials. Among them, Li₂CoSiO₄, characterized by outstanding capacity and working voltage, seems to be an interesting substitute for LiFePO₄ and related systems. In this work, structural and electrical investigations of Li₂CoSiO₄ obtained by sol–gel synthesis were presented. Thermal decomposition of gel precursor was studied using EGA (FTIR)-TGA method. Chemical composition of the obtained material was confirmed using X-ray diffraction and energy-dispersive X-ray spectroscopy. The morphology of β-Li₂CoSiO₄ was studied using transmission electron microscopy. High temperature electrical conductivity of Li₂CoSiO₄ was measured for the first time. Activation energies of the electrical conductivity of two Li₂CoSiO₄ polymorphs (β and γ) were determined. The room temperature electrical conductivity of those materials was estimated as well.

Pure Li_1.1Ni_0.35Co_0.35Mn_0.30O₂ nanosized powders have been successfully synthesized by improved hydroxide co-precipitation method, and characterized with X-ray powder diffraction and scanning electron microscopy (SEM). The electrochemical properties of cathodes and Li_1.1Ni_0.35Co_0.35Mn_0.30O₂/Li₄Ti₅O₁₂ full cells have been studied by charge–discharge tests and cyclic voltammetry. The Li_1.1Ni_0.35Co_0.35Mn_0.30O₂ powders have a typical layered hexagonal crystal structure with an average particle size of about 780 nm. The cathodes exhibit high capacities and good cycling performance. The initial discharge capacity of the cathodes is 154.8 mAhg^-1 at 0.5 C between 2.5 V and 4.3 V, and the capacity retention keeps 80.6% after 50 charge–discharge cycles. The Li_1.1Ni_0.35Co_0.35Mn_0.30O₂/Li₄Ti₅O₁₂ cells also deliver high specific capacities, good cycling stability and rate capability. This work demonstrates that Li_1.1Ni_0.35Co_0.35Mn_0.30O₂ is a promising cathode material for lithium-ion batteries.

In this paper, we present exsitu observations of a structure of particular Li₂MnSiO₄ grains at different states of charge (SOC). The goal of these studies is structural analysis of Li₂MnSiO₄ cathode material for Li-ion batteries at different stages of electrochemical reaction using transmission electron microscopy. Performed analysis suggests that amorphization process of Li₂MnSiO₄ is not directly connected with lithium ions deintercalation but with additional electrochemical reactions running in the working cell.

FeF${}_x•y$H₂O/C composite is prepared by using ferric citrate (FeC₆H₅O${}_7)$ as precursor via carbonization and fluoridation. When evaluated as cathode materials for lithium batteries, the as-prepared FeF${}_x•y$H₂O/C composite can retain a capacity of 116mAhg${}^{-1}$ at 40mAg${}^{-1}$ after 300 cycles in the voltage range of 2.0–4.5 V. The cycling performance should be attributed to Fe₂F${}_5•2$H₂O as a main component and carbon decoration. The electrical conductivity of Fe₂F${}_5•2$H₂O is higher than other iron fluorides, and it also possesses an open framework in its crystal structure for facilitating the transport of Li${}^{+}$. The simple preparation, unique crystal structure and superior electrochemical performance of FeF${}_x•y$H₂O/C composite show its great potential of being an alternative cathode material for lithium batteries.

P2-type Na${}_{0.67}$Ni${}_{0.33}$Mn${}_{0.67-x}$Ti_xO₂$(0\le x\le 0.4)$ have been synthesized as cathode materials for sodium-ion batteries, and the effect of Ti substitution on the structural evolution and electrochemical properties of Na${}_{0.67}$Ni${}_{0.33}$Mn${}_{0.67}$O₂ are investigated in detail. Analysis results indicate that an appropriate substituted amount of Mn with Ti in the MO₂ layers effectively stabilize the crystal lattice of these layered electrodes during the Na${}^{+}$ insertion/extraction process, which significantly improves their electrochemical performances between 2.5 and 4.4V. The discharge/charge patterns and in situ X-ray diffraction measurements expound the successful suppression of Na${}^{+}$/vacancy ordering and multiphase transition during the de-sodiation/sodiation process to resist the structure-induced degradation, which provide possible guidelines for exploring high performances sodium-ion batteries.

In order to explore novel vanadium-based amorphous materials, a series of Li₂O–V₂O₅–Fe₂O₃ amorphous materials were prepared with the low-cost melting-quenching method in this report. As the main framework of amorphous materials, VO₄ is connected with FeO₄ and FeO₆ to form a disordered network structure. 20Li₂O–60V₂O₅–20Fe₂O₃ amorphous material had a stable structure and Li-ion migration channel. In the electrochemical performance test, the second cycle discharge capacity was 150.7 mAh/g at a current density of 100 mA/g and the capacity retention rate was still 80% after 100 cycles because the redox reaction between vanadium and iron ions promoted the electrochemical performance. Li₂O–V₂O₅–Fe₂O₃ amorphous materials are promising lithium-ion battery cathode materials.