Crystal alignment of a LiFePO4 cathode material for lithium ion batteries using its magnetic properties

We suggest a way to control the crystal orientation of LiFePO₄ using a magnetic field to obtain an advantageous structure for lithium ion conduction. We examined the magnetic properties of LiFePO₄ such as magnetism and magnetic susceptibility, which are closely related to the crystal rotation in an external magnetic field, and considered how to use these properties for desired crystal orientation; thus, we successfully fabricated the crystal-aligned LiFePO₄, in which the b-axis was highly aligned perpendicular to the surface of a current collector. Considering the low lithium ion conductivity of LiFePO₄ inherently originated from its one-dimensional path for lithium ion diffusion, the crystal-aligned LiFePO₄ potentially facilitates favorable transport kinetics for lithium ions during the charge/discharge process in lithium ion batteries. The crystal-aligned LiFePO₄ should afford lower electrode polarization than pristine LiFePO₄, and thus the former consistently exhibited higher reversible capacity than the latter.

The crystal orientation of LiFePO₄ was controlled by using a magnetic field to facilitate favorable transport kinetics for lithium ions.     

Investigation of Cu doped flake-NiO as an anode material for lithium ion batteries

Cu foil is widely used in commercial lithium ion batteries as the current collector of anode materials with excellent conductivity and stability. In this research, commercial Cu foil was chosen as the current collector and substrate for the synthesis of Cu doped flake-NiO via a traditional hydrothermal method. The effect of the ratio of Cu and the calcination temperature on the electrochemical performance of NiO was investigated. The structure and phase composition of the Cu doped flake-NiO electrode were studied through X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and inductive coupled plasma emission spectrometry (ICP). The electrochemical properties of the Cu doped flake-NiO electrode were studied through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and a galvanostatic charge–discharge cycling technique. According to the results, the Cu-doped NiO electrode, calcined at 400 °C with a molar ratio of Cu : Ni = 1 : 8, exhibited a high reversible charge capacity. The good cycling stability and rate performance indicate that the as-prepared electrode can be applied as a potential anode for lithium ion batteries.

Cu doped flake-NiO shows excellent electrochemical performance as anode materials for lithium ion batteries.     

The electrochemical performance of fluorinated ketjenblack as a cathode for lithium/fluorinated carbon batteries

The inferior rate capacity of lithium/fluorinated carbon (Li/CF_x) batteries limits their application in the field, requiring large discharge current and high power density. Herein, we report a novel type of fluorinated carbon with superior performance through gas-phase fluorination of ketjenblack. The investigation shows that the F/C ratio of the fluorinated ketjenblack (FKB) increases with the fluorination temperature, whereas the discharge voltage decreases due to the lowered content of semi-ionic C–F bonds. Accordingly, a suitable fluorination temperature of 520 °C was selected, under which the product exhibits the largest specific capacity of 924.6 mA h g⁻¹ with discharge potential exceeding 3.1 V (vs. Li/Li⁺) and the highest energy density of 2544 W h kg⁻¹ with power density of 27 493 W kg⁻¹. This energy density is higher than the theoretical energy density of commercial fluorinated graphite (2180 W h kg⁻¹). In addition, the sample delivers good rate capability demonstrated by a specific capacity retention ratio of 79.5% even at a current density of 20C. Therefore, the FKB material may have very promising practical applications in lithium primary batteries.

Fluorinated kejtenblack as the cathode of Li/CF_x batteries exhibits excellent energy density and power density with high rate capability.     

Highly crystalline nickel hexacyanoferrate as a long-life cathode material for sodium-ion batteries

Prussian blue analogs (PBAs) are attractive cathode candidates for high energy density, including long life-cycle rechargeable batteries, due to their non-toxicity, facile synthesis techniques and low cost. Nevertheless, traditionally synthesized PBAs tend to have a flawed crystal structure with a large amount of [Fe(CN)₆]⁴⁻ openings and the presence of crystal water in the framework; therefore the specific capacity achieved has continuously been low with poor cycling stability. Herein, we demonstrate low-defect and sodium-enriched nickel hexacyanoferrate nanocrystals synthesized by a facile low-speed co-precipitation technique assisted by a chelating agent to overcome these problems. As a consequence, the prepared high-quality nickel hexacyanoferrate (HQ-NiHCF) exhibited a high specific capacity of 80 mA h g⁻¹ at 15 mA g⁻¹ (with a theoretical capacity of ∼85 mA h g⁻¹), maintaining a notable cycling stability (78 mA h g⁻¹ at 170 mA g⁻¹ current density) without noticeable fading in capacity retention after 1200 cycles. This low-speed synthesis strategy for PBA-based electrode materials could be also extended to other energy storage materials to fabricate high-performance rechargeable batteries.

A low-speed synthesis strategy was designed to fabricate Prussian blue analog based electrode materials for high-performance rechargeable batteries.     

Synthesis of manganese-based complex as cathode material for aqueous rechargeable batteries

A low-cost and eco-friendly system based on a manganese-based complex cathode and zinc anode was demonstrated. The cathode is able to reversibly (de-)insert Zn²⁺ ions, providing a high capacity of 248 mA h g⁻¹ at 0.1 A g⁻¹. Ex situ TEM and XRD were utilized to determine the electrochemical mechanism of this high capacity cathode. Moreover, the contribution of pre-added Mn²⁺ in electrolyte to the capacity was revealed, and nearly 18.9% of the capacity is ascribed to the contribution of pre-added Mn²⁺. With the help of additive, this aqueous rechargeable battery shows outstanding electrochemical property. Its cycling performance is good with 6% capacity loss after 2000 cycles at 4.0 A g⁻¹, highlighting it as a promising system for aqueous rechargeable battery applications.

Manganese-based complex with high energy density shows a capacity retention of 94% over 2000 cycles.     

Heterogeneous synthesis and electrochemical performance of LiMnPO4/C composites as cathode materials of lithium ion batteries

In this study, a facile yet efficient interfacial hydrothermal process was successfully developed to fabricate LiMnPO₄/C composites. In this strategy, the walls of carbon nanotubes were employed as heterogeneous nucleation interfaces and biomass of phytic acid (PA) as an eco-friendly phosphorus source. By comparing the experimental results, a reasonable nucleation-growth mechanism was proposed, suggesting the advantages of interfacial effects. Meanwhile, the as-synthesized LiMnPO₄/C samples exhibited superior rate performances with discharge capacities reaching 161 mA h g⁻¹ at C/20, 134 mA h g⁻¹ at 1C, and 100 mA h g⁻¹ at 5C. The composites also displayed excellent cycling stabilities by maintaining 95% of the initial capacity over 100 continuous cycles at 1C. Electrochemical impedance spectroscopy showed that the superior electrochemical performances were attributed to the low charge-transfer resistance and elevated diffusion coefficient of lithium ions. In sum, the proposed approach for the preparation of LiMnPO₄/C composites looks promising for future production of composite electrode materials for high-performance lithium-ion batteries.

A heterogeneous nucleation technique was used to prepare LiMnPO₄/C. The walls of carbon nanotubes were employed as nucleation interfaces and phytic acid as an eco-friendly phosphorus source. The product exhibits superior electrochemical performance.     

Ferrocene-functionalized polyheteroacenes for the use as cathode active material in rechargeable batteries

Herein we report the synthesis and characterization of new conjugated polymers bearing redox-active pendant groups for applications as cathode active materials in secondary batteries. The polymers comprise a ferrocene moiety immobilized at a poly(cyclopenta[2,1-b:3,4-b′]dithiophene) (pCPDT, P1) or a poly(dithieno[3,2-b:2′,3′-d]pyrrole) (pDTP, P2) backbone via an ester or an amide linker. Electrochemical and oxidative chemical polymerizations were performed in order to investigate the redox behaviour of the obtained polymers P1 and P2 and to synthesize materials on gram-scale for battery tests, respectively. During galvanostatic cycling in a typical battery environment, both polymers showed high reversible capacities of 90% and 87% of their theoretical capacity and excellent capacity retentions of 84% and 97% over 50 cycles.

Redox-active ferrocene moieties were immobilized on conjugated polyheteroacenes for the application as cathode active material in organic secondary batteries.     

NaV6O15 microflowers as a stable cathode material for high-performance aqueous zinc-ion batteries

Reversible aqueous zinc-ion batteries (ZIBs) have great potential for large-scale energy storage owing to their low cost and safety. However, the lack of long-lifetime positive materials severely restricts the development of ZIBs. Herein, we report NaV₆O₁₅ microflowers as a cathode material for ZIBs with excellent electrochemical performance, including a high specific capacity of ∼300 mA h g⁻¹ at 100 mA g⁻¹ and 141 mA h g⁻¹ maintained after 2000 cycles at 5 A g⁻¹ with a capacity retention of ∼107%. The high diffusion coefficient and stable tunneled structure of NaV₆O₁₅ facilitate Zn²⁺ intercalation/extraction and long-term cycle stability.

NaV₆O₁₅ microflowers were synthesized as a stable cathode material for aqueous zinc ion batteries, which show a high specific capacity and excellent long-term cycling performance.     

Application of soot discharged from the combustion of marine gas oil as an anode material for lithium ion batteries

Many studies have recently investigated the characteristics of combustion products emitted from ships and onshore plant facilities for use as energy sources. Most combustion products that have been reported until now are from heavy oils, however, no studies on those from light oils have been published. This study attempted to use the combustion products from the light oils from naval ships as anode materials for lithium ion batteries (LIBs). These products have a carbon black morphology and were transformed into highly crystalline carbon structures through a simple heat treatment. These new structured materials showed reversible capacities of 544, 538, 510, 485, 451 and 395 mA h g⁻¹ at C-rates of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0C, respectively, and excellent rate performance. These findings were the result of a combination hierarchical pores ranging from the meso- to macroscale and the high capacitive charge storage behavior of the soot. The results of this study prove that annealed soot with a unique multilayer graphite structure shows promising electrochemical performance suitable for the production of low-cost, high-performance LIB anode materials.

Many studies have recently investigated the characteristics of combustion products emitted from ships and onshore plant facilities for use as energy sources.     

Structure and electrochemical performance modulation of a LiNi0.8Co0.1Mn0.1O2 cathode material by anion and cation co-doping for lithium ion batteries

Ni-rich layered transition metal oxides show great energy density but suffer poor thermal stability and inferior cycling performance, which limit their practical application. In this work, a minor content of Co and B were co-doped into the crystal of a Ni-rich cathode (LiNi_0.8Co_0.1Mn_0.1O₂) using cobalt acetate and boric acid as dopants. The results analyzed by XRD, TEM, XPS and SEM reveal that the modified sample shows a reduced energy barrier for Li⁺ insertion/extraction and alleviated Li⁺/Ni²⁺ cation mixing. With the doping of B and Co, corresponding enhanced cycle stability was achieved with a high capacity retention of 86.1% at 1.0C after 300 cycles in the range of 2.7 and 4.3 V at 25 °C, which obviously outperformed the pristine cathode (52.9%). When cycled after 300 cycles at 5C, the material exhibits significantly enhanced cycle stability with a capacity retention of 81.9%. This strategy for the enhancement of the electrochemical performance may provide some guiding significance for the practical application of high nickel content cathodes.

Ni-rich layered transition metal oxides show great energy density but suffer poor thermal stability and inferior cycling performance, which limit their practical application.     

Nitridation effect on lithium iron phosphate cathode for rechargeable batteries

A novel oxynitride Li_0.94FePO_3.84N_0.16 with olivine structure (space group Pnma, no. 62) has been synthesized by heating a parent LiFePO₄ precursor obtained by citrate chemistry in flowing ammonia at 650 °C. The polycrystalline sample has been characterized by X-ray and neutron powder diffraction (NPD), elemental and thermal analysis, scanning electron microscopy (SEM) and electrochemical measurements. Based on the existing contrast between the scattering lengths of the N and O species, a Rietveld refinement of the structure from NPD data revealed that N preferentially occupies the O2 positions, as likely required to fulfil the bonding power of N ions. The refined crystallographic formula implies an oxidation state of 2.2+ for Fe cations. The differential thermal analysis, in still air, shows a strong exothermic peak at 520–540 °C due to the combustion of C contents, which are embedding the olivine particles, as observed by SEM. The electrochemical measurements suggest a better performance for the nitrided sample relative to the unnitrided LiFePO₄ material, as far as capacity and cyclability are concerned. A bond-valence energy landscape study reveals a decrease in the percolation activation energy of about 6% upon nitridation, concomitant with the better electrochemical properties of the oxynitride compound. Additionally, ceramic samples prepared under NH₃ flow could be obtained as pure and well-crystallized olivine phases at milder temperatures (650 °C) than those usually described in literature.

A better-performing oxynitride with LFP olivine structure as an appealing intercalation cathode for lithium-ion batteries.     

Electroless plating of a Sn–Ni/graphite sheet composite with improved cyclability as an anode material for lithium ion batteries

A Sn–Ni/graphite sheet composite is synthesized by a simple electroless plating method as an anode material for lithium ion batteries (LIBs). The microstructure and electrochemical properties of the composite are characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), and AC impedance spectroscopy. The results show that the as-prepared composite has Sn–Ni nanoparticles around 100 nm in size, where metallic Ni acts as an “anchor” to fix metallic Sn. The reunion phenomenon of Sn is alleviated by adding metallic Ni between the metallic Sn and graphite sheets. The Sn–Ni/graphite sheet electrode exhibits a good rate performance with a capability of 637.4, 586.3, 466.7, 371.5, 273.6, 165.3 and 97.3 mA h g⁻¹ at a current density of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0 and 10 A g⁻¹, respectively. The good electrical conductivity of Ni, high specific capacity of Sn and excellent cycling capability of the graphite sheets have a synergistic effect and are the main reasons behind the superior electrochemical performance. Furthermore, the as-prepared composite exhibits excellent lithium storage capacity and the reversible capacity increased as the cycle number increased.

A Sn–Ni/graphite sheet composite is synthesized by a simple electroless plating method as an anode material for lithium ion batteries (LIBs).     

Porous lithium cobalt oxide fabricated from metal–organic frameworks as a high-rate cathode for lithium-ion batteries

Porous materials have many applications, such as energy storage, as catalysts and adsorption etc. Nevertheless, facile synthesis of porous materials remains a challenge. In this work, porous lithium cobalt oxide (LiCoO₂) is fabricated directly from Co-based metal–organic frameworks (MOFs, ZIF-67) and lithium salt via a facile solid state annealing approach. The temperature affect on the microstructure of LiCoO₂ is also investigated. The as-prepared LiCoO₂ shows a uniform porous structure. As a cathode for a lithium-ion battery (LIB), the LiCoO₂ delivers excellent stability and superior rate capability. The as-prepared porous LiCoO₂ delivers a reversible capacity of 106.5 mA h g⁻¹ at 2C and with stable capacity retention of 96.4% even after 100 cycles. This work may provide an alternative pathway for the preparation of porous materials with broader applications.

Porous lithium cobalt oxide is fabricated directly from Co-based metal–organic frameworks and lithium salt via a facile solid state annealing approach.     

Binder-free and high-loading sulfurized polyacrylonitrile cathode for lithium/sulfur batteries

Sulfurized polyacrylonitrile (SPAN) is a promising active material for Li/S batteries owing to its high sulfur utilization and long-term cyclability. However, because SPAN electrodes are synthesized using powder, they require large amounts of electrolyte, conducting agents, and binder, which reduces the practical energy density. Herein, to improve the practical energy density, we fabricated bulk-type SPAN disk cathodes from pressed sulfur and polyacrylonitrile powders using a simple heating process. The SPAN disks could be used directly as cathode materials because their π–π structures provide molecular-level electrical connectivity. In addition, the electrodes had interconnected pores, which improved the mobility of Li⁺ ions by allowing homogeneous adsorption of the electrolyte. The specific capacity of the optimal electrode was very high (517 mA h g_electrode⁻¹). Furthermore, considering the weights of the anode, separator, cathode, and electrolyte, the Li/S cell exhibited a high practical energy density of 250 W h kg⁻¹. The areal capacity was also high (8.5 mA h cm⁻²) owing to the high SPAN loading of 16.37 mg cm⁻². After the introduction of 10 wt% multi-walled carbon nanotubes as a conducting agent, the SPAN disk electrode exhibited excellent cyclability while maintaining a high energy density. This strategy offers a potential candidate for Li/S batteries with high practical energy densities.

A simple synthesis procedure to prepare bulk-type SPAN electrodes toward the realization of Li/S batteries with enhanced practical energy densities.     

The design of a multifunctional separator regulating the lithium ion flux for advanced lithium-ion batteries

Herein, we design a controllable approach for preparing multifunctional polybenzimidazole porous membranes with superior fire-resistance, excellent thermo-stability, and high wettability. Specifically, the recyclable imidazole is firstly utilized as the eco-friendly template for micropores formation, which is an interesting finding and has tremendous potential for low-cost industrial production. The unique backbone structure of the as-prepared polybenzimidazole porous membrane endows the separator with superb thermal dimensional stability at 300 °C. Most significantly, the inherent flame retardancy of polybenzimidazole can ensure the high security of lithium-ion batteries, and the existence of polar groups of imidazole can regulate the Li⁺ flux and improve the ionic conductivity of lithium ions. Notably, the cell with a polybenzimidazole porous membrane presents higher capability (131.7 mA h g⁻¹) than that of a commercial Celgard membrane (95.4 mA h g⁻¹) at higher charge–discharge density (5C), and it can work normally at 120 °C. The fascinating comprehensive properties of the polybenzimidazole porous membrane with excellent thermal-stability, satisfying wettability, superb flame retardancy and good electrochemical performance indicate its promising application for high-safety and high-performance lithium-ion batteries.

A multifunctional PBI porous membrane with superior fire-resistance, excellent thermo-stability and high wettability is designed.     

Transition metal oxides as a cathode for indispensable Na-ion batteries

The essential requirement to harness well-known renewable energy sources like wind energy, solar energy, etc. as a component of an overall plan to guarantee global power sustainability will require highly efficient, high power and energy density batteries to collect the derived electrical power and balance out variations in both supply and demand. Owing to the continuous exhaustion of fossil fuels, and ever increasing ecological problems associated with global warming, there is a critical requirement for searching for an alternative energy storage technology for a better and sustainable future. Electrochemical energy storage technology could be a solution for a sustainable source of clean energy. Sodium-ion battery (SIB) technology having a complementary energy storage mechanism to the lithium-ion battery (LIB) has been attracting significant attention from the scientific community due to its abundant resources, low cost, and high energy densities. Layered transition metal oxide (TMO) based materials for SIBs could be a potential candidate for SIBs among all other cathode materials. In this paper, we discussed the latest improvement in the various structures of the layered oxide materials for SIBs. Moreover, their synthesis, overall electrochemical performance, and several challenges associated with SIBs are comprehensively discussed with a stance on future possibilities. Many articles discussed the improvement of cathode materials for SIBs, and most of them have pondered the use of Na_xMO₂ (a class of TMOs) as a possible positive electrode material for SIBs. The different phases of layered TMOs (Na_xMO₂; TM = Co, Mn, Ti, Ni, Fe, Cr, Al, V, and a combination of multiple elements) show good cycling capacity, structural stability, and Na⁺ ion conductivity, which make them promising cathode material for SIBs. This review discusses and summarizes the electrochemical redox reaction, structural transformations, significant challenges, and future prospects to improve for Na_xMO₂. Moreover, this review highlights the recent advancement of several layered TMO cathode materials for SIBs. It is expected that this review will encourage further development of layered TMOs for SIBs.

Na⁺ ion intercalated layered metal oxides have tremendous applications as the cathode materials for SIBs owing to their superior electrochemical performance compared to other types of cathode materials.     

Synthesis of nano-sized urchin-shaped LiFePO4 for lithium ion batteries

In this article, the facile synthesis of sea urchin-shaped LiFePO₄ nanoparticles by thermal decomposition of metal-surfactant complexes and application of these nanoparticles as a cathode in lithium ion secondary batteries is demonstrated. The advantages of this work are a facile method to synthesize interesting LiFePO₄ nanostructures and its synthetic mechanism. Accordingly, the morphology of LiFePO₄ particles could be regulated by the injection of oleylamine, with other surfactants and phosphoric acid. This injection step was critical to tailor the morphology of LiFePO₄ particles, converting them from nanosphere shapes to diverse types of urchin-shaped nanoparticles. Electron microscopy analysis showed that the overall dimension of the urchin-shaped LiFePO₄ particles varied from 300 nm to 2 μm. A closer observation revealed that numerous thin nanorods ranging from 5 to 20 nm in diameter were attached to the nanoparticles. The hierarchical nanostructure of these urchin-shaped LiFePO₄ particles mitigated the low tap density problem. In addition, the nanorods less than 20 nm attached to the edge of urchin-shaped nanoparticles significantly increased the pathways for electronic transport.

In this article, the facile synthesis of sea urchin-shaped LiFePO₄ nanoparticles by thermal decomposition of metal-surfactant complexes and application of these nanoparticles as a cathode in lithium ion secondary batteries is demonstrated.     

Amorphous red phosphorus incorporated with pyrolyzed bacterial cellulose as a free-standing anode for high-performance lithium ion batteries

Amorphous red phosphorus/pyrolyzed bacterial cellulose (P-PBC) free-standing films are prepared by thermal carbonization and a subsequent vaporization-condensation process. The distinctive bundle-like structure of the flexible pyrolyzed bacterial cellulose (PBC) matrix not only provides sufficient volume to accommodate amorphous red-phosphorus (P) but also restricts the pulverization of red-P during the alternate lithiation/delithiation process. When the mass ratio of raw materials, red-P to PBC, is 70 : 1, the free-standing P-PBC film anode exhibits high reversible capacity based on the mass of the P-PBC film (1039.7 mA h g⁻¹ after 100 cycle at 0.1C, 1C = 2600 mA g⁻¹) and good cycling stability at high current density (capacity retention of 82.84% after 1000 cycles at 2C), indicating its superior electrochemical performances.

A novel freestanding anode was prepared by combining amorphous red-P with a pyrolyzed bacterial cellulose (PBC) matrix for the first time.     

Application of MoS2 in the cathode of lithium sulfur batteries

Molybdenum disulfide (MoS₂) with a two-dimensional layered structure can effectively inhibit the shuttle effect of lithium–sulfur batteries (Li–S batteries). It contains metal–sulfur bonds and combines with polysulfides through electrostatic bonds or chemical bonds. In this paper, the structure and properties of MoS₂ are briefly introduced, and the research progress on the design, preparation, structure and properties of MoS₂ as a cathode material for Li–S batteries in recent years is reviewed. The effects of MoS₂ structure and its composition with carbon materials or metallic oxides on the performance of the electrode materials are analyzed. Finally, the existing problems and possible future research directions are pointed out.

Molybdenum disulfide (MoS₂) with a two-dimensional layered structure can effectively inhibit the shuttle effect of lithium–sulfur batteries (Li–S batteries).     

Rod-like anhydrous V2O5 assembled by tiny nanosheets as a high-performance cathode material for aqueous zinc-ion batteries

Aqueous zinc-ion batteries offer a low-cost and high-safety alternative for next-generation electrochemical energy storage, whereas suitable cathode materials remain to be explored. Herein, rod-like anhydrous V₂O₅ derived from a vanadium-based metal–organic framework is investigated. Interestingly, this material is assembled by tiny nanosheets with a large surface area of 218 m² g⁻¹ and high pore volume of 0.96 cm³ g⁻¹. Benefiting from morphological and structural merits, this material exhibits excellent performances, such as high reversible capacity (449.8 mA h g⁻¹ at 0.1 A g⁻¹), good rate capability (314.3 mA h g⁻¹ at 2 A g⁻¹), and great long-term cyclability (86.8% capacity retention after 2000 cycles at 2 A g⁻¹), which are significantly superior to the control sample. Such great performances are found to derive from high Zn²⁺ ion diffusion coefficient, large contribution of intercalation pseudocapacitance, and fast electrochemical kinetics. The ex situ measurements unveil that the intercalation of Zn²⁺ ion is accompanied by the reversible V⁵⁺ reduction and H₂O incorporation. This work discloses a direction for designing and fabricating high-performance cathode materials for zinc-ion batteries and other advanced energy storage systems.

V₂O₅ with intriguing micro/nano-hierarchical structure is fabricated via the pyrolysis of MIL-47 (a MOF material) and displays great performances as the cathode material for aqueous zinc-ion batteries.