Electronic modulation of nickel selenide by copper doping and in situ carbon coating towards high-rate and high-energy density lithium ion half/full batteries

Investigation of Solid Electrolyte Interphase Regarding Extra Capacity in Fe-Fe3C as a Superior Sodium-Ion Anode Material

Sodium-ion batteries (SIBs) offer promising advantages over lithium-ion batteries (LIBs) due to sodium's abundance and lower cost. However, challenges like thick solid electrolyte interphase (SEI) layers and the larger radius of sodium (1.02 Å vs. 0.76 Å for lithium) make graphite, the most common LIB anode, unsuitable for SIBs. To realize the maximum potential of carbon anode for SIBs, one of the main strategies is to fabricate carbon materials with tailored microstructures and to enhance redox reactivity by incorporating catalytic metals. In this work, the Fe-Fe3C nanoparticles embedded in worm-like graphitic carbon (Fe-Fe3C@GC) were synthesized by a simple chemical vapor deposition. This hybrid structure promotes the catalytic activity to achieve additional capacities through the reversible SEI layer formation, in detail, by the reversible interconversion of ester and ether derivatives as well as conductivity enhancement. Furthermore, in situ formed Fe2O3 from Fe(0) contributed extra capacity. The Fe-Fe3C@GC showed a large reversible discharge capacity of 376.2 mAh g-1 with a fading rate of 0.013% per cycle after 1000 cycles at a current density of 50 mA g-1. A full cell coupled with an FeOF cathode delivered a high energy density of 602.8 Wh kg-1.

Heterogeneous Engineering Strategy Derived In Situ Carbon-Encased Nickel Selenides Enabling Superior LIBs/SIBs with High Thermal Safety

Nowadays, the extended usage of lithium/sodium ion batteries (LIBs/SIBs) encounters nerve-wracking issues, including a lack of suitable reservoirs and high thermal runaway hazards. Although using TiO2 and Li4Ti5O12 has been confirmed to be effective in improving battery safety, their low theoretical capacities inevitably cause damage to the electrochemical performance of the battery. Achieving win-win results has become an urgent necessity. This study designed a metal-organic framework (MOF)-derived in situ carbon-coated metal selenide (Ni-Se@G@C) as the anode. When the current density is 0.1-0.3 A g-1, the initial capacity of LIBs reaches 993.2 mAh g-1, which increases to 1478.9 mAh g-1 after running 800 cycles. When running at 2 A g-1, the cell also offers a relatively high capacity of 458.3 mAh g-1 after 1500 cycles. After the replacement of graphite with Ni-Se@G@C, the self-heating temperature (T0) and thermal runaway triggering temperature (T1) of half and full cells are significantly increased. Meanwhile, the maximum thermal runaway temperature (T2) and maximal heating release rate (HRRmax) are significantly reduced. Of note, the usage of Ni-Se@G@C enables the battery with superior cycling and rate performance. When used in SIBs, the cell gives an initial discharge capacity of 624.9 mAh g-1, which still remains at 269.4 mAh g-1 after running 200 cycles at 1 A g-1. Notably, Ea of the Ni-Se@G@C cell is 5.6 times higher than that of the graphite cell, corroborating the promoted safety performance. This work provides a new paradigm for MOF-derived micro/nanostructures, enabling the battery with an excellent electrochemical and safety performance portfolio.

Fabrication of a Stable and Highly Effective Anode Material for Li-Ion/Na-Ion Batteries Utilizing ZIF-12

Transition metal selenides (TMSs) are receiving considerable interest as improved anode materials for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) due to their considerable theoretical capacity and excellent redox reversibility. Herein, ZIF-12 (zeolitic imidazolate framework) structure is used for the synthesis of Cu2Se/Co3Se4@NPC anode material by pyrolysis of ZIF-12/Se mixture. When Cu2Se/Co3Se4@NPC composite is utilized as an anode electrode material in LIB and SIB half cells, the material demonstrates excellent electrochemical performance and remarkable cycle stability with retaining high capacities. In LIB and SIB half cells, the Cu2Se/Co3Se4@NPC anode material shows the ultralong lifespan at 2000 mAg-1, retaining a capacity of 543 mAhg-1 after 750 cycles, and retaining a capacity of 251 mAhg-1 after 200 cycles at 100 mAg-1, respectively. The porous structure of the Cu2Se/Co3Se4@NPC anode material can not only effectively tolerate the volume expansion of the electrode during discharging and charging, but also facilitate the penetration of electrolyte and efficiently prevents the clustering of active particles. In situ X-ray difraction (XRD) analysis results reveal the high potential of Cu2Se/Co3Se4@NPC composite in building efficient LIBs and SIBs due to reversible conversion reactions of Cu2Se/Co3Se4@NPC for lithium-ion and sodium-ion storage.

Fabricating a high-performance anode by coating a carbon layer on a yolk-shell bimetallic selenide microsphere for enhanced lithium storage

The rational synthesis of an electrode material with a highly active and stable architecture is very critical to achieving high-performance electrochemical energy storage. Herein, N-doped carbon restricting yolk-shell CoSe2/Ni3Se4 (CoSe2/Ni3Se4@NC) flower-like microspheres were successfully synthesized from solid CoNi-glycerate microspheres using a coating technology as an anode material for lithium-ion batteries (LIBs). The unique yolk-shell CoSe2/Ni3Se4@NC microspheres with hierarchical pores can increase the contact area with the electrolyte and provide enough transfer channels for the diffusion of Li+. The carbon layer on the surface of CoSe2/Ni3Se4@NC can not only improve the conductivity of the electrode but also provide the protective effect of active nanosheets during the process of synthesis, avoiding the overall structure collapse during the charge/discharge process of LIBs. Benefiting from the high conductivity, hollow structure, and elastic NC shell bestowed by the unique architecture, the yolk-shell CoSe2/Ni3Se4@NC anode shows excellent lithium storage performances, such as an excellent reversible specific capacity of 319 mA h g-1 at a current density of 1000 mA g-1 after 500 cycles and excellent cycling stability. This synthesis strategy provides a new way to optimize the lithium storage performance of transition metal compound electrode materials, which is helpful to the design of the next generation of high-performance LIBs.

The Effect of Ni Doping on FeOF Cathode Material for High-Performance Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have emerged as a promising alternative to lithium-ion batteries for large-scale energy storage systems due to the abundance and low price of sodium. Until recently, the low theoretical capacities of intercalation-type cathodes less than 250 mAh g-1 have limited the energy density of SIBs. On the other hand, iron oxyfluoride (FeOF) has a high theoretical capacity of ≈885 mAh g-1 as a conversion-type cathode material for SIBs. However, FeOF suffers from poor cycling stability, rate capability, and low initial Coulombic efficiency caused by its low electrical conductivity and slow ionic diffusion kinetics. To solve these problems, doping aliovalent Ni2+ on FeOF electrodes is attempted to improve the electronic conductivity without using a carbon matrix. The ionic conductivity of FeOF is also enhanced due to the formation of oxygen defects in the FeOF crystal structure. The FeOF-Ni1 electrode shows an excellent cycling performance with a reversible discharge capacity of 450.4 mAh g-1 at 100 mAh g-1 after 100 cycles with a fading rate of 0.20% per cycle. In addition, the FeOF-Ni1//hard carbon full cell exhibited a high energy density of 876.9 Wh kg-1 cathode with a good cycling stability.

Tetrahedral Bonding Structure (Ni3 -Se) Induced by Lattice-Distortion of Ni to Achieve High Catalytic Activity in Na-Se Battery

Fabrication of transition-metal catalytic materials is regarded as a promising strategy for developing high-performance sodium-selenium (Na-Se) batteries. However, more systematic explorations are further demanded to find out how their bonding interactions and electronic structures can affect the Na storage process. This study finds that lattice-distorted nickel (Ni) structure can form different bonding structures with Na2 Se4 , providing high activity to catalyze the electrochemical reactions in Na-Se batteries. Using this Ni structure to prepare electrode (Se@NiSe2 /Ni/CTs) can realize rapid charge transfer and high cycle stability of the battery. The electrode exhibits high storage performance of Na+ ; i.e., 345 mAh g⁻1 at 1 C after 400 cycles, and 286.4 mAh g⁻1 at 10 C in rate performance test. Further results reveal the existence of a regulated electronic structure with upshifts of the d-band center in the distorted Ni structure. This regulation changes the interaction between Ni and Na2 Se4 to form a Ni3 -Se tetrahedral bonding structure. This bonding structure can provide higher adsorption energy of Ni to Na2 Se4 to facilitate the redox reaction of Na2 Se4 during the electrochemical process. This study can inspire the design of bonding structure with high performance in conversion-reaction-based batteries.

Ant-nest-like Cu2-xSe@C with biomimetic channels boosts the cycling performance for lithium storage

Controlling the microstructure and composition of electrodes is crucial to enhance their rate capability and cycling stability for lithium storage. Inspired by the highly interconnected network and good mechanical integrity of an ant-nest architecture, herein, a biomimetic strategy is proposed to enhance the electrochemical performance of Cu2-xSe. After facile carbonization and selenization treatments, the 3D Cu-MOF is successfully transformed into the final ant-nest-like Cu2-xSe@C (AN-Cu2-xSe@C). The AN-Cu2-xSe@C is composed of interconnected Cu2-xSe channels with amorphous carbon coated on the outer surface. The 3D interconnected channels within the AN-Cu2-xSe@C provide fast charge transport pathways and enhanced structural integrity to tolerate the large volume fluctuations of Cu2-xSe during cycling. When applied as the anode for lithium storage, the AN-Cu2-xSe@C shows remarkable electrochemical performance with a high capacity of 1452 mA h g-1 after 1200 cycles at 1.0 A g-1 and 879 mA h g-1 after 2500 cycles at 10.0 A g-1, respectively. Mechanism investigations demonstrate that the AN-Cu2-xSe@C experiences complicated conversion-intercalation co-existence reactions upon cycling. The existence of capacitive behaviour (74%) also contributes to the extended cycling performance. Our work offers a new avenue for designing a high performance electrode using the biomimetic concept.

High potassium ion storage capacity with long cycling stability of sustainable oxygen-rich carbon nanosheets

The development of carbon materials for potassium storage is limited by their low specific capacity and poor cycling stability due to the sluggish kinetics of K ions. Herein, fucoidan-derived oxygen-rich carbon nanosheets are reported as a fantastic anode for potassium ion batteries. Attributed to its 2D porous sheet-like structure (morphology engineering), rich oxygen doping (defect engineering), and dilated graphitic layer in an amorphous structure (structure engineering), a competitive capacity of 392 mA h g-1 at 0.05 A g-1 and a long cycling span over 2500 cycles at 2 A g-1 was achieved for the carbon anode, outperforming most of the reported carbons. The kinetic analyses reveal that rich active sites and a porous nanosheet structure account for the superb rate performance and cycling stability of the material. Ex situ X-ray photoelectron spectroscopy measurements demonstrate that the introduction of C[double bond, length as m-dash]O greatly promotes K+ adsorption, and that the improvement of the C[double bond, length as m-dash]O bonds during cycling contributes to enhancement in the capacity. The fabricated potassium ion hybrid capacitor displays an exceptional energy/power density of 193 W h kg-1/22 324 W kg-1, and a promising cycling stability with 99.3% capacity retention over 2000 cycles. This work provides a large-scale synthesis strategy for preparing oxygen-rich carbon nanosheets for advanced potassium ion storage.