Tungsten Boride Stabilized Single-Crystal LiNi0.83Co0.07Mn0.1O2 Cathode for High Energy Density Lithium-Ion Batteries: Performance and Mechanisms

Transition metal doped LiNiO₂ layered compounds have attracted significant interest as cathode materials for lithium-ion batteries (LIBs) in recent years due to their high energy density. However, a critical issue of LiNiO₂-based cathodes is caused particularly at highly delithiated state by irreversible phase transition, initiation/propagation of cracks, and extensive reactions with electrolyte. Herein, a tungsten boride (WB)-doped single-crystalline LiNi_0.83Co_0.07Mn_0.1O₂ (SNCM) cathode is reported that affectively addresses these drawbacks. In situ/ex situ microscopic and spectroscopic evidence that B³⁺ enters the bulk of the SNCM, enlarging the interlayer spacing, thus facilitating Li⁺ diffusion, while W³⁺ forms an amorphous surface layer consisting of Li_xW_yO_z (LWO) and Li_xB_yO_z (LBO), which aids the construction of a robust cathode-electrolyte interphase (CEI) film, are shown. It is also shown that WB doping is effective in controlling the degree of the c-axis contraction and release of oxygen-containing gases at high voltages. The best doping concentration of WB is 0.6 wt.%, at which the capacity retention rate of the SNCM reaches 93.2% after 200 cycles at 2.7–4.3 V, while the morphology and structure of the material remain largely unchanged. The presented modification strategy offers a new way for the design of new stable SNCM cathodes for high-energy-density LIBs.     

Highly Reversible Anion Redox of Manganese-Based Cathode Material Realized by Electrochemical Ion Exchange for Lithium-Ion Batteries

Anion energy storage provides the possibility to achieve higher specific capacity in lithium-ion battery cathode materials, but the problems of capacity attenuation, voltage degradation, and inconsistent redox behavior are still inevitable. In this paper, a novel O2-type manganese-based layered cathode material Li_x[Li_0.2Mn_0.8]O₂ with a ribbon superlattice structure is prepared by electrochemical ion exchange, which realizes the highly reversible redox of anions and excellent cycle performance. Through low-voltage pre-cycling treatment, the specific capacity of the material can reach 230 mAh g⁻¹ without obvious voltage attenuation. During the electrochemical ion exchange, the precursor with P2 structure transforms into Li_x[Li_0.2Mn_0.8]O₂ with O2 structure through the slippage and shrink of adjacent slabs, and the special superlattice structure in Mn slab is still retained. Simultaneously, a certain degree of lattice mismatch and reversible distortion of the MnO₆ octahedron occur. In addition, the anion redox catalyzes the formation of the solid electrolyte interface, stabilizing the electrode/electrolyte interface and inhibiting the dissolution of Mn. The mechanism of electrochemical ion exchange is systematically studied by comprehensive structural and electrochemical characterization, opening an attractive path for the realization of highly reversible anion redox.     

New Insight into Microstructure Engineering of Ni-Rich Layered Oxide Cathode for High Performance Lithium Ion Batteries

Ni-rich layered LiNi_xCo_yMn_1−x−yO₂ (LNCM) with Ni content over >90% is considered as a promising lithium ion battery (LIB) cathode, attributed by its low cost and high practical capacity. However, Ni-rich LNCM inevitably suffers rapid capacity fading at a high state of charge due to the mechanochemical breakdown; in particular, the microcrack formation has been regarded as one of the main culprits for Ni-rich layered cathode failure. To address these issues, Ni-rich layered cathodes with a textured microstructure are developed by phosphorous and boron doping. Attributed by the textured morphology, both phosphorous- and boron-doped cathodes suppress microcrack formation and show enhanced cycle stability compared to the undoped cathode. However, there exists a meaningful capacity retention difference between the doped cathodes. By adapting the various analysis techniques, it is shown that the boron-doped Ni-rich layered cathode displays better cycle stability not only by its ability to suppress microcracks during cycling but also by its primary particle morphology that is reluctant to oxygen evolution. The present work reveals that not only restraint of particle cracks but also suppression of oxygen release by developing the oxygen stable facets is important for further improvements in state-of-the-art Li ion battery Ni-rich layered cathode materials.     

新型锂离子电池正极材料LiNi_(0.5)Mn_(1.5)O_4的形貌与组分分析

针对新型锂离子电池正极材料Li Ni0.5Mn1.5O4,采用SEM、EDS等手段进行分析,确定了导致电池性能不同的原因。同时,证明了扫描电镜和能谱仪能够应用于新材料的分析中。     

Electrically Coupled Electrolyte Engineering Enables High Interfacial Stability for High-Voltage Sodium-Ion Batteries

Sodium-ion batteries (SIBs) suffer from severe capacity decay as the harmful substances caused by the violent decomposition of electrolyte under high voltages continue to erode the cathodes. Therefore, the design of high-voltage electrolyte and construction of robust cathode–electrolyte interface (CEI) are critical for long-life SIBs. Herein, an electrically coupled composite electrolyte that takes the merits of cross-linked gel polymers and s well-tuned antioxidant additive (4-trifluoromethylphenylboronic acid, TFPBA) is proposed. Through an electrical coupling effect, TFPBA can be anchored by the cross-linked polymer framework to immobilize the PF₆⁻ anion and adsorb onto cathode surface spontaneously, both of which promote the formation of a robust CEI layer to facilitate Na⁺ transportation and suppress subsequent side reactions and corrosive cracking. As a result, the cells integrating high-voltage P2/O3 cathode and well-tailored gel polymer electrolyte achieve stable cycling over 550 cycles within 1.8–4.2 V with a capacity retention of 71.0% and a high-rate discharge capacity of 77.4 mAh g⁻¹ at 5 C. The work paves the way for the development of functionalized quasi-solid electrolyte for practical next generation high-voltage SIBs.     

Carbon Nanotube‐Encapsulated Noble Metal Nanoparticle Hybrid as a Cathode Material for Li‐Oxygen Batteries

Although Li‐oxygen batteries offer extremely high theoretical specific energy, their practical application still faces critical challenges. One of the main obstacles is the high charge overpotential caused by sluggish kinetics of charge transfer that is closely related to the morphology of discharge products and their distribution on the cathode. Here, a series of noble metal nanoparticles (Pd, Pt, Ru and Au) are encapsulated inside end‐opened carbon nanotubes (CNTs) by wet impregnation followed by thermal annealing. The resultant cathode materials exhibit a dramatic reduction of charge overpotentials compared to their counterparts with nanoparticles supported on CNT surface. Notably, the charge overpotential can be as low as 0.3 V when CNT‐encapsulated Pd nanoparticles are used on the cathode. The cathode also shows good stability during discharge–charge cycling. Density functional theory (DFT) calculations reveal that encapsulation of “guest” noble metal nanoparticles in “host” CNTs is able to strengthen the electron density on CNT surfaces, and to avoid the regional enrichment of electron density caused by the direct exposure of nanoparticles on CNT surface. These unique properties ensure the uniform coverage of Li₂O₂ nanocrystals on CNT surfaces instead of localized distribution of Li₂O₂ aggregation, thus providing efficient charge transfer for the decomposition of Li₂O₂.     

CoFe–Cl Layered Double Hydroxide: A New Cathode Material for High‐Performance Chloride Ion Batteries

Chloride ion batteries (CIBs) are regarded as promising energy storage systems due to their large theoretical volumetric energy density, high abundance, and low cost of chloride resources. Herein, the synthesis of CoFe layered double hydroxide in the chloride form (CoFe–Cl LDH), for use as a new cathode material for CIBs, is demonstrated for the first time. The CoFe–Cl LDH exhibits a maximum capacity of 239.3 mAh g^?1 and a high reversible capacity of ≈160 mAh g^?1 over 100 cycles. The superb Cl^? ion storage of CoFe–Cl LDH is attributed to its unique topochemical transformation property during the charge/discharge process: a reversible intercalation/deintercalation of Cl^? ions in cathode with slight expansion/contraction of basal spacing, accompanied by chemical state changes in Co²⁺/Co³⁺ and Fe²⁺/Fe³⁺ couples. First‐principles calculations reveal that CoFe–Cl LDH is an excellent Cl^? ion conductor, with extremely low energy barriers (0.12?0.25 eV) for Cl^? diffusion. This work opens a new avenue for LDH materials as promising cathodes for anion‐type rechargeable batteries, which are regarded as formidable competitors to traditional metal ion‐shuttling batteries.     

空投型雷达发射机阴极高压电源设计

阴极高压电源纹波是影响发射机频谱的关键因素,针对空投型雷达强冲击、低气压、安装空间受限的应用环境,提出了一种空投型雷达发射机阴极高压电源设计方法。采用软开关谐振技术减少功率开关管损耗,以串级式倍压电路输出高压,采取有效措施减小输出高压纹波,提高了系统可靠性,并对强冲击和低气压环境有较好的适应性。该阴极高压电源小型化效果...     

Freestanding Bilayer Carbon–Sulfur Cathode with Function of Entrapping Polysulfide for High Performance Li–S Batteries

Li–S batteries benefit from numerous advantages such as high theoretical capacity, high energy density, and availability of an abundance of sulfur. However, commercialization of Li–S batteries has been impeded because of low loading amount of active materials and poor cycle performance. Herein, a freestanding bilayer carbon–sulfur (FBCS) cathode is reported with superior electrochemical performance at a high sulfur loading level (3 mg cm^?2). The top component of the FBCS cathode is composed of interlacing multiwalled carbon nanotubes (MWCNT) and the bottom component is made up of a mixed layer of sulfur imbedded in MWCNT and N‐doped porous carbon (NPC). The MWCNT layer (top part of FBCS cathode) blocks polysulfide migration from the cathode to the anode, and NPC in the bottom part of the FBCS cathode not only provides spacious active sites but also absorbs polysulfide by the nitrogen functional group. The designed novel FBCS cathode delivered a high initial discharge capacity of 964 and 900 mAh g^?1 at 0.5 and 1 C, respectively. It also displayed an excellent capacity retention of 83.1% at 0.5 C and 83.4% at 1 C after 300 cycles.     

Understanding the Origin of Li2MnO3 Activation in Li‐Rich Cathode Materials for Lithium‐Ion Batteries

Li‐rich layered cathode materials have been considered as a family of promising high‐energy density cathode materials for next generation lithium‐ion batteries (LIBs). However, although activation of the Li₂MnO₃ phase is known to play an essential role in providing superior capacity, the mechanism of activation of the Li₂MnO₃ phase in Li‐rich cathode materials is still not fully understood. In this work, an interesting Li‐rich cathode material Li_1.87Mn_0.94Ni_0.19O₃ is reported where the Li₂MnO₃ phase activation process can be effectively controlled due to the relatively low level of Ni doping. Such a unique feature offers the possibility of investigating the detailed activation mechanism by examining the intermediate states and phases of the Li₂MnO₃ during the controlled activation process. Combining powerful synchrotron in situ X‐ray diffraction analysis and observations using advanced scanning transmission electron microscopy equipped with a high angle annular dark field detector, it has been revealed that the subreaction of O₂ generation may feature a much faster kinetics than the transition metal diffusion during the Li₂MnO₃ activation process, indicating that the latter plays a crucial role in determining the Li₂MnO₃ activation rate and leading to the unusual stepwise capacity increase over charging cycles.     

Novel Cathode Materials for Na‐Ion Batteries Composed of Spoke‐Like Nanorods of Na[Ni0.61Co0.12Mn0.27]O2 Assembled in Spherical Secondary Particles

The development of high‐energy and high‐power density sodium‐ion batteries is a great challenge for modern electrochemistry. The main hurdle to wide acceptance of sodium‐ion batteries lies in identifying and developing suitable new electrode materials. This study presents a composition‐graded cathode with average composition Na[Ni_0.61Co_0.12Mn_0.27]O₂, which exhibits excellent performance and stability. In addition to the concentration gradients of the transition metal ions, the cathode is composed of spoke‐like nanorods assembled into a spherical superstructure. Individual nanorod particles also possess strong crystallographic texture with respect to the center of the spherical particle. Such morphology allows the spoke‐like nanorods to assemble into a compact structure that minimizes its porosity and maximizes its mechanical strength while facilitating Na⁺‐ion transport into the particle interior. Microcompression tests have explicitly verified the mechanical robustness of the composition‐graded cathode and single particle electrochemical measurements have demonstrated the electrochemical stability during Na⁺‐ion insertion and extraction at high rates. These structural and morphological features contribute to the delivery of high discharge capacities of 160 mAh (g oxide)^?1 at 15 mA g^?1 (0.1 C rate) and 130 mAh g^?1 at 1500 mA g^?1 (10 C rate). The work is a pronounced step forward in the development of new Na ion insertion cathodes with a concentration gradient.     

Atomic Structure and Kinetics of NASICON NaxV2(PO4)3 Cathode for Sodium‐Ion Batteries

Na₃V₂(PO₄)₃ is one of the most important cathode materials for sodium‐ion batteries, delivering about two Na extraction/insertion from/into the unit structure. To understand the mechanism of sodium storage, a detailed structure of rhombohedral Na₃V₂(PO₄)₃ and its sodium extracted phase of NaV₂(PO₄)₃ are investigated at the atomic scale using a variety of advanced techniques. It is found that two different Na sites (6b, M1 and 18e, M2) with different coordination environments co‐exist in Na₃V₂(PO₄)₃, whereas only one Na site (6b, M1) exists in NaV₂(PO₄)₃. When Na is extracted from Na₃V₂(PO₄)₃ to form NaV₂(PO₄)₃, Na⁺ occupying the M2 site (CN = 8) is extracted and the rest of the Na remains at M1 site (CN = 6). In addition, the Na atoms are not randomly distributed, possibly with an ordered arrangement in M2 sites locally for Na₃V₂(PO₄)₃. Na⁺ ions at the M1 sites in Na₃V₂(PO₄)₃ tend to remain immobilized, suggesting a direct M2‐to‐M2 conduction pathway. Only Na occupying the M2 sites can be extracted, suggesting about two Na atoms able to be extracted from the Na₃V₂(PO₄)₃ structure.     

Multifunctional Chitosan–rGO Network Binder for Enhancing the Cycle Stability of Li–S Batteries

Although Li–S batteries are currently receiving great interest, due to their high energy density and the low cost of sulfur, practical applications are still inhibited by capacity fading that is caused by various undesirable processes. In this study, a new multifunctional network binder composed of chitosan and reduced graphene oxide (rGO) is introduced to enhance the capacitive performance of Li–S batteries. Chitosan is reacted with graphene oxide in aqueous solution to produce a homogenous network, which effectively enhances the redox system by entrapping lithium polysulfides, reinforces the mechanical properties, and allows electrical conductivity through the binder system. Collaborative relationship‐based chitosan–rGO network binder allows noteworthy improvement in the capacity decay of 0.016% per cycle at 1 C for 1000 cycles.     

Self‐Doping Cathode Interfacial Material Simultaneously Enabling High Electron Mobility and Powerful Work Function Tunability for High‐Efficiency All‐Solution‐Processed Polymer Light‐Emitting Diodes

A variety of N ‐hydrogenated/N ‐methylated pyridinium salts are elaborately designed and synthesized. Thermogravimetric and X‐ray photoelectron spectra analysis indicate the intensities of the N? H covalent bonds are strengthened step‐by‐step from 3,3′‐(5′‐(3‐(pyridin‐3‐yl)phenyl)‐[1,1′:3′,1″‐terphenyl]‐3,3″‐diyl)dipyridine (Tm)‐HCl to Tm‐HBr and then Tm‐TfOH, which results in gradually improved cathode interfacial modification abilities. The larger dipole moments of N⁺? H containing moieties compared to those of the N⁺? CH₃ endow them with more preferable interfacial modification abilities. Electron paramagnetic resonance signals reveal the existence of radical anions in the solid state of Tm‐TfOH, which enables its self‐doping property and high electron mobility up to 1.67 × 10^?3 cm² V^?1 s^?1. Using the Tm‐TfOH as the cathode interfacial layers (CILs), the phenyl‐substituted poly(para ‐phenylene vinylene)‐based all‐solution‐processed polymer light‐emitting diodes (PLEDs) achieve more preferable device performances than the poly[(9,9‐bis(3′‐(N ,N ‐dimethylamino)propyl)‐2,7‐fluorene)‐alt ‐2,7‐(9,9‐dioctylfluorene)]‐based ones, i.e., high current density of nearly 300 mA cm^?2, very high luminance over 15 000 cd m^?2 at a low bias of 5 V. Remarkably, the thickness of the CILs has little impact on the device performance and high efficiencies are maintained even at thicknesses up to 85 nm, which is barely realized in PLEDs with small‐molecule‐based electron transporting layers.     

Inorganic Filler Enhanced Formation of Stable Inorganic-Rich Solid Electrolyte Interphase for High Performance Lithium Metal Batteries

Lithium metal (LM) is a promising anode material for next generation lithium ion based electrochemical energy storage devices. Critical issues of unstable solid electrolyte interphases (SEIs) and dendrite growth however still impede its practical applications. Herein, a composite gel polymer electrolyte (GPE), formed through in situ polymerization of pentaerythritol tetraacrylate with fumed silica fillers, is developed to achieve high performance lithium metal batteries (LMBs). As evidenced theoretically and experimentally, the presence of SiO₂ not only accelerates Li⁺ transport but also regulates Li⁺ solvation sheath structures, thus facilitating fast kinetics and formation of stable LiF-rich interphase and achieving uniform Li depositions to suppress Li dendrite growth. The composite GPE-based Li||Cu half-cells and Li||Li symmetrical cells display high Coulombic efficiency (CE) of 90.3% after 450 cycles and maintain stability over 960 h at 3 mA cm⁻² and 3 mAh cm⁻², respectively. In addition, Li||LiFePO₄ full-cells with a LM anode of limited Li supply of 4 mAh cm⁻² achieve capacity retention of 68.5% after 700 cycles at 0.5 C (1 C = 170 mA g⁻¹). Especially, when further applied in anode-free LMBs, the carbon cloth||LiFePO₄ full-cell exhibits excellent cycling stability with an average CE of 99.94% and capacity retention of 90.3% at the 160th cycle at 0.5 C.     

Active Regulation Volume Change of Micrometer-Size Li2S Cathode with High Materials Utilization for All-Solid-State Li/S Batteries through an Interfacial Redox Mediator

Low electronic and ionic transport, limited cathode active material utilization, and significant volume change have pledged the practical application of all-solid-state Li/S batteries (ASSLSBs). Herein, an unprecedented Li₂S-Li_xIn₂S₃ cathode is designed whereby In₂S₃ reacts with Li₂S under high-energy ball milling. In situ electron diffraction and ex situ XPS are implanted to probe the reaction mechanism of Li₂S-Li_xIn₂S₃ in ASSLSBs. The results indicate that Li_xIn₂S₃ serves as a mobility mediator for both charge-carriers (Li⁺ and e⁻) and redox mediator for Li₂S activation, ensuring efficient electronic and ionic transportation at the cathode interface and inhibiting ≈ 70% relative volumetric change in the cathode, as confirmed by in situ TEM. Thus, the Li₂S-Li_xIn₂S₃ cathode delivers an initial areal capacity of 3.47 mAh cm⁻² at 4.0 mg_Li2S cm⁻² with 78% utilization of Li₂S. A solid-state cell with Li₂S-Li_xIn₂S₃ cathode carries 82.35% capacity retention over 200 cycles at 0.192 mA cm⁻² and a remarkable rate capability up to 0.64 mA cm⁻² at RT. Besides, Li₂S-Li_xIn₂S₃ exhibits the highest initial areal capacity of 4.08 mAh cm⁻² with ≈74.01% capacity retention over 50 cycles versus 6.6 mg_Li2S cm⁻² at 0.192 mA cm⁻² at RT. The proposed strategy of the redox mediator minimized volumetric change and realized outstanding electrochemical performance for ASSLSBs.     

A Family of High‐Performance Cathode Materials for Na‐ion Batteries,Na3(VO1−xPO4)2 F1+2x (0 ≤ x ≤ 1): Combined First‐Principles and Experimental Study

Room‐temperature Na‐ion batteries (NIBs) have recently attracted attention as potential alternatives to current Li‐ion batteries (LIBs). The natural abundance of sodium and the similarity between the electrochemical properties of NIBs and LIBs make NIBs well suited for applications requiring low cost and long‐term reliability. Here, the first successful synthesis of a series of Na₃(VO_1?x PO₄)₂F_1+2x (0 ≤ x ≤ 1) compounds as a new family of high‐performance cathode materials for NIBs is reported. The Na₃(VO_1?x PO₄)₂F_1+2x series can function as high‐performance cathodes for NIBs with high energy density and good cycle life, although the redox mechanism varies depending on the composition. The combined first‐principles calculations and experimental analysis reveal the detailed structural and electrochemical mechanisms of the various compositions in solid solutions of Na₃(VOPO₄)₂F and Na₃V₂(PO₄)₂F₃. The comparative data for the Na _y (VO_1?x PO₄)₂F_1+2x electrodes show a clear relationship among V³⁺/V⁴⁺/V⁵⁺ redox reactions, Na⁺?Na⁺ interactions, and Na⁺ intercalation mechanisms in NIBs. The new family of high‐energy cathode materials reported here is expected to spur the development of low‐cost, high‐performance NIBs.