Synthesis of porous hollow six-branched star-like MnO and its enhanced electrochemical properties as a lithium ion anode material

Novel structured porous hollow six-branched star-like MnO was synthesized via a facile, surfactant-free hydrothermal decomposition, which was followed by high-temperature heat treatment. Compared with the nonporous hollow six-branched star-like MnO₂, the porous hollow six-branched star-like MnO realized substantially higher electrochemical performance (844.8 mAh g⁻¹ at 0.5 A g⁻¹ after 200 cycles and 769.7, 741.7, 728.9, 713.2, and 704.4 mAh g⁻¹ at 0.1, 0.3, 0.5, 1, and 1.5 A g⁻¹, respectively, for porous star-like MnO, compared with 338.4 mAh g⁻¹ and 476.7, 392.4, 357, 303.4, and 269.9, respectively, under the same testing conditions for nonporous star-like MnO₂). The superior performance of the porous hollow six-branched star-like MnO is attributed to its enhanced electrode kinetics, which are due to an enlarged active contact area and shortened electron and Li⁺ conduction paths.     

One-step hydrothermal synthesis of 3D porous microspherical LiFePO4/graphene aerogel composite for lithium-ion batteries

Three-dimensional (3D) porous LiFePO₄/graphene aerogel (LFP/GA) composite was successfully prepared by an in-situ hydrothermal process. In this composite, the LiFePO₄ microspheres assembled by nanoparticles were embedded in a three-dimensional framework intertwined with the graphene sheets, which acts as a bridge for transfer of electron and diffusion of lithium ion. The large specific surface of the composite structure enables the increased infiltration area and utilization of the active material. The content of the graphene sheet is analyzed and is found important for the Li-storage characteristics of LiFePO₄. An aerogel composite with 10% of graphene displays the best electrochemical performance, with the specific discharge capacities of 168 mAh g⁻¹ and 155 mAh g⁻¹ at respectively 0.1C and 1C, and the capacity retains 96.3% for up to 800 cycles. This novel 3D porous aerogel composite is identified as a promising cathode material for the rechargeable Li battery, and the simple strategy may be applied to construct other high performing composite structure and materials.     

Phase structure and electrochemical performance of layered-spinel integrated LiNi0.5Mn0.5O2-LiMn1.9Al0.1O4 composite cathodes for lithium ion batteries

In recent years, multi-component integrated composite cathodes for lithium ion batteries have attracted considerable attention. In this work, novel layered-spinel integrated cathode materials of (1−x)LiNi_0.5Mn_0.5O₂-xLiMn_1.9Al_0.1O₄ were synthesized by a sol-gel method, and their phase structures, morphologies and electrochemical performance were investigated. The crystal structure of the (1−x)LiNi_0.5Mn_0.5O₂-xLiMn_1.9Al_0.1O₄ is changed from layered to spinel structure with increasing x. All the samples exhibit nanoscale grains with the minimum grain size of ~130 nm when x = 0.5. The composite electrode with x = 0.5 exhibits the optimal discharge capacity, presenting a large initial discharge capacity of 236 mAh g⁻¹ at the current density of 20 mA g⁻¹. Good rate capability is also obtained at the composite electrode with x = 0.5 where the electrode displays the relatively high discharge capacity of 64.9 mAh g⁻¹ at the high rate of 5 C. The improved electrochemical performance is related to the introduction of spinel structure into layered structure and small grain size. The spinel structure can stabilize the layered structure, which leads to the improvement in the electrochemical performance of the composites; and the small grain size in the sample with x = 0.5 provides short lithium ion diffusion way and thus enhances the electrochemical performance.     

Modified polysulfides conversion catalysis and confinement by employing La2O3 nanorods in high performance lithium-sulfur batteries

The development of lithium-sulfur batteries (LSB) was hindered due to the shuttling of Li-polysulfides in electrolytes and sluggish electrochemical kinetics of polysulfides. To address these stumbling blocks, we introduced La₂O₃ nanorods modification of ketjen black@sulfur (La₂O₃/KB@S) composite that adsorbs and provides sufficient sites with Li-polysufides interaction. The La₂O₃ nanorods play a key role in the adsorption and catalysis performance of the polysulfides, which further accelerate the redox kinetics. Consequently, the La₂O₃/KB@S cathode with sulfur loading of 3.1 mg cm⁻² attained a high initial discharge capacity of 833 mAh g⁻¹ at a 0.5C rate and displayed excellent cyclic stability with reversible capacity of 380 mAh g⁻¹ after 500 cycles with an average of 98% coulombic efficiency. Further, even with high sulfur loading of 5 mg cm⁻², the La₂O₃/KB@S cathode also presents a capacity of 4.9 mAh at 0.3C and still maintains a stable value of 3.87 mAh after 150 cycles. The results suggest the multifunction La₂O₃ nanorods anchoring effectively and catalyzing are beneficial to realize the goal of the large-scale application with high load active materials and high-performance LSB.     

Synergistic effect of bulk phase doping and layered-spinel structure formation on improving electrochemical performance of Li-Rich cathode material

In this study, La was doped into the lithium layer of Li-rich cathode material and formed a layered-spinel hetero-structure. The morphology, crystal structure, element valence and kinetics of lithium ion migration were studied by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The La doped lithium-rich cathode material exhibited similar initial discharge capacity of 262.8 mAh g^?1 at 0.1 C compared with the undoped material, but the discharge capacity retention rate can be obviously improved to 90% after 50 cycles at 1.0 C. Besides that, much better rate capability and Li⁺ diffusion coefficient were observed. The results revealed that La doping not only stabilized the material structure and reduced the Li/Ni mixing degree, but also induced the generation of spinel phase to provide three-dimensional diffusion channels for lithium ion migration. Moreover, the porous structure of the doped samples also contributed to the remarkable excellent electrochemical performance. All of these factors combined to significantly improve the electrochemical performance of the material.     

Characterization of structure and electrochemical properties of lithium manganese oxides for lithium secondary batteries hydrothermally synthesized from δ-KxMnO2

Lithium manganese oxides have attracted much attention as cathode materials for lithium secondary batteries in view of their high capacity and low toxicity. In this study, layered manganese oxide (δ-K_xMnO₂) has been synthesized by thermal decomposition of KMnO₄, and four lithium manganese oxide phases have been synthesized for the first time by mild hydrothermal reactions of this material with different lithium compounds. The lithium manganese oxides were characterized by powder X-ray diffraction (XRD), inductively coupled plasma emission (ICPE) spectroscopy, and chemical redox titration. The four materials obtained are rock salt structure Li₂MnO₃, hollandite (BaMn₈O₁₆) structure α-MnO₂, spinel structure LiMn₂O₄, and birnessite structure Li_xMnO₂. Their electrochemical properties used as cathode material for secondary lithium batteries have been investigated. Of the four lithium manganese oxides, birnessite structure Li_xMnO₂ demonstrated the most stable cycling behavior with high Coulombic efficiency. Its reversible capacity reaches 155 mAh g⁻¹, indicating that it is a viable cathode material for lithium secondary batteries.     

Electrochemical effect of graphite fluoride modification on Li-rich cathode material in lithium ion battery

Recently, Li-rich layered structure has been used in the cathode of lithium ion batteries because of its high specific capacity. However, this structure still has some problems including large irreversible capacity loss, significant deterioration of cycling performance and poor rate property. Therefore, in our study, graphite fluoride is used to modify the surface of Li_1.14Ni_0.133Co_0.133Mn_0.544O₂ through a facile solvent evaporating method. Due to conversion reaction of the graphite fluoride, the huge discharge capacity compensation during the first discharging can improve the coulombic efficiency significantly. As reaction products, the layer of LiF@carbon reduces the interfacial reactions and increases the reversible capacity. After modification by graphite fluoride, the discharge capacities are improved by 22% from 266 to 325?mAh?g^?1 at 0.1?C, and 13% at 2?C. After 100 cycles, the discharge capability at 1?C is increased by 13% from 180 to 203?mAh?g^?1.     

The influences of sodium sources on the structure evolution and electrochemical performances of layered-tunnel hybrid Na0.6MnO2 cathode

Manganese (Mn) based oxide materials are regarded as promising cathodes for sodium ion batteries (SIBs) due to their high energy density, low-cost and environmental benignity. Here, we focus on the influences of various sodium sources on the structure diversity and electrochemical performances changes of layered-tunnel hybrid Na_0.6MnO₂ cathode. The Na_0.6MnO₂ cathodes were prepared by precipitation method followed by grinding with different sodium sources and annealing in air. The XRD results evidenced that the mass ratio of layered and tunnel components would be markedly influenced by sodium source. Electrochemical test results also demonstrate distinctive performances of Na_0.6MnO₂ cathodes with various sodium sources. Na_0.6MnO₂ cathode with Na₂C₂O₄ exhibited the best performances with 90 mAh g⁻¹ retained after 100 cycles at 1.0C. Superior rate performance with average discharge capacities of 180, 159, 143, 126, 112 and 93 mAh g⁻¹ at 0.1, 0.5, 1.0, 2.0, 4.0 and 8.0C was also observed. Furthermore, the EIS demonstrate that Na_0.6MnO₂ cathode with Na₂C₂O₄ displayed smaller charge transfer and fast Na⁺ diffusion rate, which indicated enhanced electrochemical reaction kinetics. The excellent electrochemical performance of Na_0.6MnO₂ with Na₂C₂O₄ is mainly due to the appropriate proportion of layered-tunnel component and their synergistic effects, which are influenced by sodium sources.     

Preparation and performance of poly(ethylene oxide)-based composite solid electrolyte for all solid-state lithium batteries

Poly(ethylene oxide)-based solid electrolyte is attractive for using in all solid-state lithium batteries. However, the polymer has a certain degree of crystallization, which is adverse to the conduction of lithium ions. In order to overcome this drawback, a flexible composite polymer electrolyte (CPE) containing TiO₂ nanoparticles is elaborately designed and synthesized by tape casting method. The effects of different molar ratios of EO: Li and mass fraction of TiO₂ on the physical and electrochemical performances are carefully studied. The results show the CPE10 having 10 wt % TiO₂ has the lowest degree of crystallinity of 9.04%, the lowest activation energy of 8.63 × 10⁻⁵ eV mol⁻¹. Besides, the CPE10 shows a lower polarization and higher decomposition voltage. Thus, prepared all solid-state battery LiFePO₄/CPE10/Li shows a high initial capacity of 160 mAh g⁻¹ at 0.1 C, 134 mAh g⁻¹ at 0.5 C and higher capacity retention of 93.2% after 50 cycles at 0.5 C (1 C = 170 mAh g⁻¹). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47498.     

Hollow Co2SiO4 microcube with amorphous structure as anode material for construction of high performance lithium ion battery

To solve the problem of large volume expansion of cobalt silicate electrode during cyclic process and low electric conductivity, Co₂SiO₄ with amorphous, porous and hollow structure is firstly designed to act as high performance lithium ion battery (LIB) anode. Compared with crystalline materials, the amorphous Co₂SiO₄ microcube could facilitate Li⁺ diffusion to enhance their performance of LIBs because of isotropic characteristics. Here, the amorphous Co₂SiO₄ hollow microcube (named as a-Co₂SiO₄ HC) was prepared by mild hydrothermal method with use of MnCO₃ microcube as hard-template. Benefitting from the advantages of such structure, Li⁺ diffusion rate was greatly accelerated and the volume expansion can be alleviated. The as-prepared amorphous Co₂SiO₄ hollow microcube as anode material of LIBs exhibited significantly improved electrochemical performance of 610 mAh g⁻¹ even after 380 cycles at 500 mAh g⁻¹ than their crystalline counterpart (only 280 mAh g⁻¹ retained after 380 cycles). This work is a good try to employ amorphous metal silicate in LIBs and simultaneously motivate the exploration of other amorphous materials for high performance LIBs, SIBs, catalysts, etc.     

Binder-free carbon-coated TiO2@graphene electrode by using copper foam as current collector as a high-performance anode for lithium ion batteries

Anatase TiO₂ is widely used in lithium ion batteries (LIBs) due to its excellent safety and excellent structural stability. However, due to the poor ion and electron transport and low specific capacity (335 mAh g⁻¹) of TiO₂, its application in LIBs is severely limited. For the first time, we report a binder-free, carbon-coated TiO₂@graphene hybrid by using copper foam as current collector (TG-CM) to enhance the ionic and electronic conductivity and increase the discharge specific capacity of the electrode material without adding conductive carbon (such as super P, etc.) and a binder (such as polyvinylidene fluoride (PVDF), etc.). When serving as an anode material for LIBs, TG-CM displays excellent electrochemical performance in the voltage range of 0.01–3.0 V. Moreover, the TG-CM hybrid delivers a high reversible discharge capacity of 687.8 mAh g⁻¹ at 0.15 A g⁻¹. The excellent electrochemical performance of the TG-CM hybrid is attributed to the increased lithium ion diffusion rate due to the introduction of graphene and amorphous carbon layer, and the increased contact area between the active material and electrolyte, and small resistance with copper foam as the current collector without an additional binder (PVDF) and conductivity carbon (super P).     

Highly improved structural stability and electrochemical properties of Ni-rich NCM cathode materials

We report a simple, easy way using WO₃ to build a conductive protective coating layer on the surface of LiNi_0.8Co_0.1Mn_0.1O₂ cathode. The WO₃ coating layer can block direct contact between the LiNi_0.8Co_0.1Mn_0.1O₂ and electrolyte, resulting in suppress the transition metal dissolution and interfacial unwanted reaction on the particle surface. Moreover, WO₃ coating layer allows for the smooth and rapid lithium and electron kinetics. The WO₃ coating improves the electrochemical performance, especially, this way significantly enhances the rate capability of 166.2 mAh g⁻¹ at 6.0C and cyclability of 85.8% after 100 cycles. Therefore, WO₃ coating provides a new breakthrough to improve the structural stability and suppress the resistance for superior electrochemical performances of lithium ion batteries.     

Influence of different lithium sources on the morphology,structure and electrochemical performances of lithium-rich layered oxides

Lithium-rich layered oxides were synthesized via co-precipitation by using different lithium sources (LiOH, Li₂CO₃ and CH₃COOLi). Scanning electron microscope (SEM), Thermo gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), Inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD) and electrochemical measurements were used to investigate the morphology, reaction process, specific surface area, composition, structure and electrochemical performance of the lithium-rich oxides, respectively. The use of different lithium sources mainly affects the primary particle size and secondary particle morphology of the final product. Using LiOH as the lithium source, the maximum discharge capacity of sample can reach to 272.1 mA h g^–1 in the voltage range of 2.0–4.6 V at room temperature, even after 50 cycles, the retention rate is still reach 91.4%. The electrochemical impedance spectroscopy (EIS) results show that lithium-rich oxides using LiOH as the lithium source have the minimum value of impedance after 50 cycles. Therefore, the choice of appropriate lithium source is an effective way to improve the electrochemical properties of lithium-rich layered oxides.     

Synthesis of 1D-MoS2/graphene nanotubes aided with sodium chloride for reversible lithium storage

A novel negative material consisting of graphene nanotubes and ultrathin MoS₂ is synthesized by a simple one-step hydrothermal method assisted with Sodium chloride. The MoS₂/Graphene electrodes deliver a specific capacity of 1350 mAh g^?1 under 0.1 A g^?1 and high rate capability (retaining 85.5% capacity from 0.1 A g^?1 to 0.8 A g^?1). A high remarkable capacity of 820 mAh g^?1 can still be recovered at 0.5 A g^?1 after 500 cycles, and the average coulombic efficiency was as high as 99.98% during the additional 500 cycles. The excellent Li-ion storage performance of MoS₂/Graphene nanotubes may be attributed to the ultra-thin MoS₂ flakes and curled graphene nanotubes. This structural feature has a strong adsorption capacity for lithium ions, which can provide a broad space for ion storage. A large number of active sites dispersed in the layered molybdenum disulfide promote the kinetics of the electrochemical reaction, empowering the ultra-thin layered molybdenum disulfide to get a higher theoretical capacity. In addition, the existence of the tubular structure alleviates volume expansion and provides a way for the rapid movement of electrons and diffusion of Li⁺ during repeated cycles.     

Enhanced electrochemical performance of layered Li-rich cathode materials for lithium ion batteries via aluminum and boron dual-doping

Lithium-rich layer oxides can possess satisfactory specific capacity but suffer from severe voltage attenuation and poor cycle stability. In this work, Al-B dual-doping technique is introduced to modify Li-rich layered oxide cathode materials. Cross-section scanning electron microscopy, Energy Disperse Spectroscopy and X-ray photoelectron spectroscopy results confirm that Al and B successfully doped into the interior of the bulk Li_1.2Ni_0.2MnO₂ particles, and the High-resolution transmission electron microscopy and X-ray diffraction Rietveld refinement results reveal that the c-axis distance of LMR-AB increases. The Al-B co-doped sample shows greatly enhanced electrochemical performance. Specifically, it exhibits of a discharge capacity of 120?mAh?g^?1 at 5?C and a capacity retention of 89.12% after 100 cycles at 1?C. The voltage decay is also greatly alleviated. The enhanced electrochemical performance of LMR-AB is due to the synergistic effects bought by the Al-B dual-doping, where increase of c-axis distance decreases Li⁺ intercalation/deintercalation barrier. B³⁺ doping into the tetrahedral site block the migration of TM ions and Al³⁺ act as pillars in the octahedral site, stabilizing the structure and suppressing the phase transition during cycling.     

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.     

Dual carbon-confined Na2MnPO4F nanoparticles as a superior cathode for rechargeable sodium-ion battery

Na₂MnPO₄F has drawn worldwide attention as cathode materials for sodium-ion batteries with great promise due to its high theoretical capacity (124 mAh g⁻¹) and working voltage plateau (3.6 V). Unfortunately, its electrochemical performances are largely limited by the intrinsic low electron conductivity and sluggish diffusion of Na⁺. Herein, a reduced graphite oxide nanosheets and nano-carbon co-modified Na₂MnPO₄F nanocomposite is prepared via a simple hydrothermal method. And the composite possesses a three-dimensional “pellets-on-sheets” structure, in which core-shell structured nanoparticles (Na₂MnPO₄F nanoparticles coated by carbon coating layers) are uniformly anchored on the surface of well-dispersed reduced graphite oxide nanosheets. Such unique structure is favorable for fast Na⁺ and electron transports and supplies sufficient active sites for Na⁺ insertion. As the cathode of sodium-ion battery, the as-prepared dual carbon-modified Na₂MnPO₄F composite exhibits a super discharge capacity of 122 mAh g⁻¹ at 0.05 C and high rate-performance (42 mAh g⁻¹ at 2 C) as well as long cycle performance (77% capacity retention after 200 cycles at 0.1 C). Meanwhile, it presents two obvious potential platforms of about 3.7 V and 3.5 V during the charge and discharge process, respectively, revealing its potential applications in high energy density batteries.     

Facile fabrication of porous NiMoO4@C nanowire as high performance anode material for lithium ion batteries

Herein, porous NiMoO₄@C nanowire is purposefully synthesized using oleic acid as carbon source, and further evaluated as high performance anode material for Li-ion batteries (LIBs). Compared with the pure NiMoO₄, porous NiMoO₄@C nanowire exhibits high reversible charge/discharge specific capacity, excellent cycle stability and preeminent rate capability. A stable reversible lithium storage capacity of 975 mAh g⁻¹ can still be maintained after 100 cycles at 200 mA g⁻¹. When the current density decreases back from 3000 mA g⁻¹ to 100 mA g⁻¹, a high discharge specific capacity of 884 mAh g⁻¹ is recovered. The porous structure and carbon layers can enhance the electronic transmission and structural stability, shorten the path lengths for ion and electron transport, and provide a mechanical buffer space to accommodate the volume expansion/contraction during the repeated Li⁺ insertion/extraction processes. All the results highlight that the porous NiMoO₄@C nanowire composite would be a promising candidate for high performance anode material of LIBs owing to its excellent electrochemical properties.     

Rice husk-derived SiOx@carbon nanocomposites as a high-performance bifunctional electrode for rechargeable batteries

This paper we use ZnCl₂ to activates and reduces rice husks to produce SiO_x@N-doped carbon core-shell nanocomposites with inner voids is a facile and effective strategy to improve the electrochemical performance. As an anode material for the lithium-ion batteries, the composites exhibit a high reversible capacity (1315 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹) and long-term stability (584 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). Such outstanding cycling stability is attributed to the small size of the SiO_x particles with inner voids and the carbon layer coating can guarantee good structural integrity for long cycle stability. As a cathode material for Li–S batteries, the composite displays a high capacity and good stability (675 mAh g⁻¹ after 100 cycles at 0.1C). Its good performance and facile preparation will improve the utilization of rice husk waste.     

Highly enhanced electrochemical performances of LiNi0.815Co0.15Al0.035O2 by coating via conductively LiTiO2 for lithium-ion batteries

LiTiO₂ film-coated layered LiNi_0.815Co_0.15Al_0.035O₂ (NCA) material was successfully synthesised through in situ hydrolysis–lithiation to improve electrochemical properties. Herein, NCA was synthesised using solid state reaction, coated by hydrolysis of tetrabutyl titanate and subjected to lithiation process. The optimal molar ratio (LiTiO₂: NCA) was found to be 1.0 mol%, and the thickness of LiTiO₂ film coated on the surface of NCA of 18 nm was observed through HRTEM images. Compared with pristine NCA, 1.0 mol% LiTiO₂-coated NCA demonstrated better electrochemical performance with larger capacity of 20 mAh g⁻¹ under 1 C after 100 cycles. Its related capacity retention was 90.8%. The 1.0 mol% LiTiO₂-coated sample exhibited high discharge capacity of 157.6 mAh g⁻¹ at a current rate of 10 C, whereas the pristine sample only presented 145.3 mAh g⁻¹. The considerably improvement of the rate and cycling properties of the NCA cathode material is achieved using LiTiO₂ as a Li⁺-conductive coating layer. These new findings contribute towards the design of a stable-structured Ni-rich material for lithium-ion batteries.