High Initial Specific Capacity Research Articles

Facile Fabrication of Large-Area CuO Flakes for Sodium-Ion Energy Storage Applications

CuO is recognized as a promising anode material for sodium-ion batteries because of its impressive theoretical capacity of 674 mAh g−1, derived from its multiple electron transfer capabilities. However, its practical application is hindered by slow reaction kinetics and rapid capacity loss caused by side reactions during discharge/charge cycles. In this work, we introduce an innovative approach to fabricating large-area CuO and CuO@Al2O3 flakes through a combination of magnetron sputtering, thermal oxidation, and atomic layer deposition techniques. The resultant 2D CuO flakes demonstrate excellent electrochemical properties with a high initial reversible specific capacity of 487 mAh g−1 and good cycling stability, which are attributable to their unique architectures and superior structural durability. Furthermore, when these CuO flakes are coated with an ultrathin Al2O3 layer, the integration of the 2D structures with outer nanocoating leads to significantly enhanced electrochemical properties. Notably, even after 70 rate testing cycles, the CuO@Al2O3 materials maintain a high capacity of 525 mAh g−1 at a current density of 50 mA g−1. Remarkably, at a higher current density of 2000 mA g−1, these materials still achieve a capacity of 220 mAh g−1. Moreover, after 200 cycles at a current density of 200 mA g−1, a high charge capacity of 319 mAh g−1 is sustained. In addition, a full cell consisting of a CuO@Al2O3 anode and a NaNi1/3Fe1/3Mn1/3O2 cathode is investigated, showcasing remarkable cycling performance. Our findings underscore the potential of these innovative flake-like architectures as electrode materials in high-performance sodium-ion batteries, paving the way for advancements in energy storage technologies.

One-Step Molten-Salt-Assisted Approach for Direct Preparation and Regeneration of LiNi0.6Co0.2Mn0.2O2 Cathode.

Single-crystal lithium-nickel-manganese-cobalt-oxide (SC-NMC) is attracting increasing attention due to its excellent structural stability. However, its practical production faces challenges associated with complex precursor preparation processes and severe lithium-nickel cation mixing at high temperatures, which restricts its widespread application. Here, a molten-salt-assisted method is proposed using low-melting-point carbonates. This method obviates the necessity for precursor processes and simplified the synthetic procedure for SC-NMC down to a single isothermal sintering step. Multiple characterizations indicate that the acquired SC-LiNi0.6Mn0.2Co0.2O2 (SC-622) exhibits favorable structural capability against intra-granular fracture and suppressive Li+/Ni2+ cation mixing. Consequently, the SC-622 exhibits superior electrochemical performance with a high initial specific capacity (174 mAhg-1 at 0.1C, 3.0-4.3V) and excellent capacity retention (87.5% after 300 cycles at 1C). Moreover, this molten-salt-assisted method exhibits its effectiveness in directly regenerating SC-622 from spent NMC materials. The recovered material delivered a capacity of 125.4 mAhg-1 and retained 99.4% of the initial capacity after 250 cycles at 1 C. This work highlights the importance of understanding the process-structure-property relationships and can broadly guide the synthesis of other SC Ni-rich cathode materials.

Amorphous lithiophilic cobalt‐boride@rGO interlayer for dendrite‐free and highly stable lithium metal batteries

AbstractLithium metal batteries (LMBs) are recognized to be crucial for secondary battery technology targeting electric vehicles and portable electronic devices. However, the undesirable growth of lithium dendrites would result in reduced capacity, short‐circuit, and overheating, seriously hindering the practical applications of LMBs. To address this issue, a neoteric lithiophilic interlayer on a commercial polypropylene separator is presented for the first time, which is constructed by amorphous CoB nanoparticles decorated reduced graphene oxide nanosheets (CoB@rGO). Density Functional Theory calculations and experimental analysis reveal remarkable lithiophilicity features for CoB@rGO and provide multiple Li deposition sites and improved electrolyte wettability, which facilitates the formation of durable solid electrolyte interphase (SEI), reduces side reactions, and improves Li+ flux regulation for long‐term cycling stability in LMBs. Taking advantage of these merits, the symmetric Li//Li cell with CoB@rGO/PP separator exhibits stable cycling for up to 1600 h at 1 mA cm−2 with 1 mAh cm−2. Employed with CoB@rGO separator, the Li//LiFePO4 full cell with a high LiFePO4 loading of 11 mg cm−2 delivers a high initial specific capacity of 115.3 mAh g−1 and a low decay rate of 0.08% per cycle after 200 cycles even at a high rate of 2C.

Anionic chemistry regulation boosting the reversible redox in CoSexTey@C polyhedrons for sodium storage

CoTe2 as a potential electrode material for sodium-ion batteries (SIBs) suffers severe volume expansion and rapid capacity degradation. Herein, we propose an anionic chemistry regulation strategy to enhance the redox performance of CoTe2 by Se substitution which creates more porosity inside the structure to accommodate the volume expansion. Physical characterizations and theoretical calculations have studied the structural and dynamical influence of Se/Te ratio on the overall performance. As a result, CoSe1.33Te0.67@C with a 〈111〉 preferential growth direction exhibited the most balanced performance, which delivered a high initial specific capacity of 795 mAh/g at 0.05 A/g, a high rate performance of 5 A/g and a capacity retention of 370 mAh/g after 400 cycles at 0.5 A/g. Accordingly, a full SIB was constructed with a Na3V2(PO4)3 cathode and a CoSe0.67Te0.33@C anode, delivering a maximum energy density of 197.2 Wh kg−1. These results have proved that anionic chemistry regulation is quite efficient to synthesize metal tellurides with high redox activity and long life-span for SIB.

Copper/cobalt metal-organic framework composites for advanced anode material of lithium-ion battery

In this paper, two new types of metal-organic frameworks (MOFs) materials, namely Cu-IM and Co-MOF, have been successfully applied to the anode of lithium-ion batteries with LiPF6 (EC: DMC = 1:1, volume) electrolyte additive. Cu-IM and Co-MOF employed imidazole (IM) and 2-methylimidazole (2-MeIM) as organic ligands, respectively. The results revealed the synthesized MOFs exhibited high initial discharge specific capacities (Cu-IM: 1964.5 mAh g−1, Co-MOF: 1423.3 mAh g−1) as well as low internal resistances (Cu-IM: 146 Ω; Co-MOF: 236 Ω). To alleviate the issue of capacity decay in single MOFs, we attempted the dual-MOFs materials through the rational design of interfacial/surface properties and microstructure. Compared to Cu-IM, the prepared Cu-IM/Co-MOF composites have a higher specific surface area and pore volume. Furthermore, the charge transfer resistance of Cu-IM/Co-MOF composites (141 Ω) was lower than that of Cu-IM and Co-MOF respectively. After a heat treatment to Cu-IM/Co-MOF composites, the electrochemical performance of obtained Cu-IM/Co-MOF 250 dual-MOFs composites have been significantly improved. The Cu-IM/Co-MOF 250 dual-MOFs composites demonstrated excellent cycling stability and high discharge specific capacities at various current densities. The composites displayed stable discharge specific capacity retention of 834 mAh g−1 (50 mA g−1, 75 cycles), 710.5 mAh g−1 (200 mA g−1, 50 cycles), and 392.5 mAh g−1 (500 mA g−1, 50 cycles), highlighting their promising performance for energy storage applications. The synthesized Cu-IM/Co-MOF 250 dual-MOFs composites demonstrates exceptional cycling performance and rate capability, implying that it has the promising prospects as anode material for lithium-ion batteries.

Al-doped flower-like VO2(B) microspheres as high-performance cathode materials for lithium-ion batteries

VO2(B), as a potential cathode material for lithium-ion batteries (LIBs), is attracting extensive attention from researchers because of its great superiority in terms of theoretical specific capacity, energy density, and cost. Nevertheless, VO2(B), leads to irreversible decay of specific capacity during cycling for reasons including structural stability and inferior electrical conductivity. In this work, the electrochemical performance of VO2(B) electrode materials are further enhanced via Al ion doping. The results reveal that the prepared Al-doped 3D flower-like VO2(B) microspheres exhibit a high initial discharge specific capacity (as high as 314.8 mAh/g at 0.1 A/g current density) at an Al doping amount of n(Al3+)/n(V5+) = 6.0 %. Moreover, it displays a first discharge specific capacity of up to 229.2 mAh/g at a current density of 1 A/g with the capacity retention rate of 90.0 % after 120 cycles. As a result, Al-doped 3D flower-like VO2(B) microspheres provide enormous commercialization potential as cathode materials for LIBs.

Layered double Hydroxides-MXene heterointerfaces with abundant anion vacancies expediting sulfur redox kinetics for High‑Performance Lithium–Sulfur batteries

Lithium-sulfur batteries (LSBs) are increasingly seen as advanced battery systems of great promise, owing to their exceptional energy density and cost-effectiveness. Yet, designing efficient electrocatalysts that can both effectively mitigate the diffusion of soluble lithium polysulfides (LiPSs) and enhance redox kinetics still remains a significant challenge, particularly at high sulfur loadings and lean electrolyte conditions. In this work, we develop NiCo-layered double hydroxides (NiCo-LDHs) nanosheets featuring abundant oxygen vacancies (Vo), anchored on Ti3C2-MXene nanosheets (denoted as Vo-LDHs-MXenes), tailored specifically for high-performance LSBs. The heterointerfaces between MXenes and Vo-LDHs modify the electronic structure and enhance the catalytic activity of the LDHs and MXenes, yielding multifunctional synergistic effects. Our theoretical and electrochemical analyses indicate that the Vo-LDHs-MXenes heterostructures exhibit enhanced affinity for LiPSs and superior catalytic performances compared to individual LDHs. This improvement facilitates the efficient adsorption and conversion of LiPSs, as well as the nucleation and decomposition of Li2S. Consequently, the cell with the Vo-LDHs-MXenes modified separator delivers stable cycling performances with a high initial specific capacity of 938.9 mAh/g over 300cycles at 1.0C and good rate capabilities. Notably, it still achieves a high initial areal capacity of 6.09 mAh cm−2 under a high sulfur loading of 6.7 mg cm−2 and low electrolyte/sulfur (E/S) ratio of 6.0 μL mg−1 over 50cycles.

Coaxial Electrospinning of CoS1.097@C Core–Shell Fibers Anode Material for High-Performance Sodium-Ion Batteries

As an important component that affects the storage performance of sodium-ion batteries (SIBs), novel anode materials still need to be well explored. Herein, CoS1.097@C core–shell fibers as anode material were designed via coaxial electrospinning, stabilization, and carbonization. Specially, CoS1.097 powders are distributed in the inner shell of carbon fibers, and sufficient pore spaces are present among themselves. The unique encapsulation structure, porous characteristics, and one-dimensional conductive carbon shell can enable the CoS1.097@C core–shell fibers’ high initial specific capacity, excellent rate capability, and long cycle life. The initial charge and discharge capacities of the electrode at 50 mA g−1 are 386.0 and 830.9 mAh g−1, respectively. After 2000 cycles at 500 mA g−1, the discharge capacity is 216.3 mAh g−1. Even at 3000 mA g−1, the rate capacity can be maintained at 83.3 mAh g−1.

Improved cycle stability and high-rate capability of LiNbO3-coated Li3VO4 as anode material for lithium-ion battery

Lithium vanadate (Li3VO4) has garnered considerable attention as an alternative negative electrode material for non-aqueous lithium-ion batteries due to its high capacity, energy efficiency, and stable discharge voltage. Nonetheless, the Li3VO4 material displays a low rate capability, attributed mainly to its poor intrinsic electronic conductivity. Here, we report the synthesis of lithium niobate LiNbO3-coated Li3VO4 (LVO@LNO) using a one-pot sol-gel method. The resulting LVO@LNO demonstrates a high reversible capacity of approximately 530 mAh/g, which is more than double that of free Li3VO4. To explore the effect of the LNO coating process on the morphological and structural properties, Raman, XRD, operando XRD, XPS, SEM and HTEM analyses were conducted. To explain the enhancement of electronic conductivity in our modified material after a LiNbO3 coating, we conducted an Ex-Situ electrochemical impedance (EIS) and Density Functional Theory (DFT) computational study. Additionally, we designed a full cell utilizing a 1 wt% LNO-coated LVO anode and NMC-811 cathode. The cell yielded an output voltage of approximately 2.8 V with a high initial specific capacity of 350 mAh/g versus to the anode, at 1C with a capacity retention of 85 % after 100 cycles.

The ferrocene-bonding NH2-UIO-66 as an ion sieve to intercept polysulfides and screen Li+ for upgrading performance of lithium-sulfur batteries

Intercepting polysulfides and screening Li+ is one of the most effective methods to achieve high-performance lithium-sulfur (Li-S) batteries. This study focuses on the covalent anchoring of ferrocene into NH2-UIO-66 for the modification of polypropylene (PP) separator. The introduction of ferrocene enables the reduction of the pore size of NH2-UIO-66 from 5.1 Å to 3.9 Å, thereby blocking polysulfides anions and penetrating lithium cations at the molecular level, resulting in significant inhibition in the shuttle effect of polysulfides. The cell with this functional separator exhibits a high initial specific capacity of 1490 mA h g−1 with a capacity decay of 0.018 % after 1000 cycles at 2C. This work provides an effective method of separator modification for high-performance energy storage systems.

Co8NiS8/Ni3S2 heterostructure anchored on 3D carbon nanofiber networks as a high-efficiency polysulfide catalyst for lithium-sulfur batteries

The polar Co8NiS8/Ni3S2 heterostructures anchored on 3D carbon nanofiber networks (CNFs) were prepared as catalysts modifying the separator of lithium-sulfur batteries. The Co8NiS8/Ni3S2combining the synergistic chemisorption and catalysis effect, can effectively alleviate the shuttle effect, while the CNFs further accelerate the transfer of ions and electrons through the separator. Based on the synergistic effect, the modified Li-S battery delivers a high initial specific capacity of 1532.6 mA h g−1 at 0.1C and a high reversible discharge capacity of 519.7 mA h g−1 at 2C over 500 cycles with 0.061 % decay per cycle.

Anion-Reinforced Solvating Ionic Liquid Electrolytes Enabling Stable High-Nickel Cathode in Lithium-Metal Batteries.

Ionic liquid electrolytes (ILEs) are promising to develop high-safety and high-energy-density lithium-metal batteries (LMBs). Unfortunately, ILEs normally face the challenge of sluggish Li+ transport due to increased ions' clustering caused by Coulombic interactions. Here a type of anion-reinforced solvating ILEs (ASILEs) is discovered, which reduce ions' clustering by enhancing the anion-cation coordination and promoting more anions to enter the internal solvation sheath of Li+ to address this concern. The designed ASILEs, incorporating chlorinated hydrocarbons and two anions, bis(fluorosulfonyl) imide (FSI- ) and bis(trifluoromethanesulfonyl) imide (TFSI- ), aim to enhance Li+ transport ability, stabilize the interface of the high-nickel cathode material (LiNi0.8 Co0.1 Mn0.1 O2 , NCM811), and retain fire-retardant properties. With these ASILEs, the Li/NCM811 cell exhibits high initial specific capacity (203 mAh g-1 at 0.1 C), outstanding capacity retention (81.6% over 500 cycles at 1.0 C), and excellent average Coulombic efficiency (99.9% over 500 cycles at 1.0 C). Furthermore, an Ah-level Li/NCM811 pouch cell achieves a notable energy density of 386Wh kg-1 , indicating the practical feasibility of this electrolyte. This research offers a practical solution and fundamental guidance for the rational design of advanced ILEs, enabling the development of high-safety and high-energy-density LMBs.

Stabilizing Ni-rich Single-crystalline LiNi0.83 Co0.07 Mn0.10 O2 Cathodes using Ce/Gd Co-doped High-entropy Composite Surfaces.

Ni-rich layered oxides are promising lithium-ion batteries (LIBs) cathode materials for their high reversible capacity, but they suffer from fast structural degradation during cycling. Here, we report the Ce/Gd incorporated single-crystalline LiNi0.83 Co0.07 Mn0.10 O2 (SC-NCM) cathode materials with significantly enhanced cycling stability. The Gd ions are adequately incorporated in SC-NCM while Ce ions are prone to aggregate in the outer surface, resulting in the formation of a high-entropy zone in the near-surface of SC-NCM, including a Gd doped LiCeO2 (LCGO) shell and Ce/Gd dopant-concentrated layer. The high-entropy zone can effectively inhibit the oxygen evolution and prevent the formation of oxygen vacancies. Meanwhile, it leads to a greatly improved H2-H3 phase transformation reversibility and mitigated stress/strain caused by Li-ion extraction/insertion during (de)lithiation process. The synergetic effects of reduced oxygen vacancies concentration and mitigated stress/strain can effectively prevent the in-plane migration of TM ions, lattice planar gliding as well as the formation of intragranular nanocracks. Consequently, Ce/Gd incorporated SC-NCM (SC-NCM@CG2) delivers a high initial discharge specific capacity of 219.7 mAh g-1 at 0.1 C and an excellent cycling stability with a capacity retention of 90.2 % after 100 cycles at 1.0 C.

Stabilizing Ni‐rich Single‐crystalline LiNi0.83Co0.07Mn0.10O2 Cathodes using Ce/Gd Co‐doped High‐entropy Composite Surfaces

AbstractNi‐rich layered oxides are promising lithium‐ion batteries (LIBs) cathode materials for their high reversible capacity, but they suffer from fast structural degradation during cycling. Here, we report the Ce/Gd incorporated single‐crystalline LiNi0.83Co0.07Mn0.10O2 (SC‐NCM) cathode materials with significantly enhanced cycling stability. The Gd ions are adequately incorporated in SC‐NCM while Ce ions are prone to aggregate in the outer surface, resulting in the formation of a high‐entropy zone in the near‐surface of SC‐NCM, including a Gd doped LiCeO2 (LCGO) shell and Ce/Gd dopant‐concentrated layer. The high‐entropy zone can effectively inhibit the oxygen evolution and prevent the formation of oxygen vacancies. Meanwhile, it leads to a greatly improved H2‐H3 phase transformation reversibility and mitigated stress/strain caused by Li‐ion extraction/insertion during (de)lithiation process. The synergetic effects of reduced oxygen vacancies concentration and mitigated stress/strain can effectively prevent the in‐plane migration of TM ions, lattice planar gliding as well as the formation of intragranular nanocracks. Consequently, Ce/Gd incorporated SC‐NCM (SC‐NCM@CG2) delivers a high initial discharge specific capacity of 219.7 mAh g−1 at 0.1 C and an excellent cycling stability with a capacity retention of 90.2 % after 100 cycles at 1.0 C.

Design and Synthesis of Viologen-based Copolymers for High Performance Li-Dual-Ion Batteries.

Dual-ion batteries based on organic electrodes show great potential to break through the bottlenecks existed in conventional LIBs due to their high specific capacity, lifted working voltage, and environmental benignity. Herein, two innovative viologen-based bipolar copolymers poly(viologen-pyrene-4,5,9,10-tetrone dichloride) (PVPTOCl2 ) and poly(viologen-anthraquinone dichloride) (PVAQCl2 ) were synthesized and applied as high performance cathodes for lithium-dual-ion battery. Bearing the dual-ion storage capability of viologen and carbonyls, as well as the conjugated structure of pyrene-4,5,9,10-tetrone, the synthesized copolymers show remarkable electrochemical performances for LIBs. Compared to PVAQCl2 , PVPTOCl2 shows superior electrochemical performance with high initial specific capacity (235.0 mAh g-1 at 200 mA g-1 ), high reversibility (coulombic efficiency up to 99.96 % at 1 A g-1 ), excellent rate performance (150.3 mAh g-1 at 5 A g-1 ) and outstanding cycling stability (a reversible capacity of 197.5 mAh g-1 at a current density of 1 A g-1 and a low capacity loss per cycle of 0.11‰ during 3000 cycles). Moreover, the charge storage mechanism was systematically investigated by ex-situ FT-IR, ex-situ XPS and DFT calculations. The results clearly reveal the structure-property relationship of the bipolar-molecules, providing a new platform to develop efficient bipolar materials for dual-ion batteries.

High-vacancy-type titanium oxycarbide for large-capacity lithium-ion storage

Electrochemical processes involving the ion insertion/desertion are usually accompanied by composition variation and structural evolution of electrode materials. Here we propose a meaningful lattice regulation by inserting lithium ions to unlock an active crystalline plane from which high energy storage performance can be obtained. A rock-salt titanium oxycarbide featuring 12% titanium vacancies (Ti0.88□0.12C0.63O0.37) in high active (011) crystalline plane bears excellent electrochemical activity that enables additional reversible lithium insertion, providing a high initial specific capacity of 390 mAh g−1 at 0.05 A g−1. EPR, XAS, PDF and TEM measurements confirm abundant titanium vacancies, electrochemical studies combined with computational calculations demonstrate high activity of (011) crystalline plane as domain channels for lithium-ion insertion, and ex-situ XRD investigations disclose structural evolution during lithium-ion insertion/desertion. Notably, the repeated lithium-ion insertion/desertion promotes new exposure of (011) crystalline planes, leading to a capacity “negative fading” from the initial 120 to 325 mAh g−1 after 1100 cycles at 0.5 A g−1. The study presents the inner relationship between material microstructural transformation and electrochemical properties, providing a new perspective for mechanism re-understanding and structure development of ion-storage electrode materials.

Fine-Tuning Intrinsic and Doped Hydrogenated Amorphous Silicon Thin-Film Anodes Deposited by PECVD to Enhance Capacity and Stability in Lithium-Ion Batteries.

Silicon is a promising alternative to graphite as an anode material in lithium-ion batteries, thanks to its high theoretical lithium storage capacity. Despite these high expectations, silicon anodes still face significant challenges, such as premature battery failure caused by huge volume changes during charge-discharge processes. To solve this drawback, using amorphous silicon as a thin film offers several advantages: its amorphous nature allows for better stress mitigation and it can be directly grown on current collectors for material savings and improved Li-ion diffusion. Furthermore, its conductivity is easily increased through doping during its growth. In this work, we focused on a comprehensive study of the influence of both electrical and structural properties of intrinsic and doped hydrogenated amorphous silicon (aSi:H) thin-film anodes on the specific capacity and stability of lithium-ion batteries. This study allows us to establish that hydrogen distribution in the aSi:H material plays a pivotal role in enhancing battery capacity and longevity, possibly masking the significance of the conductivity in the case of doped electrodes. Our findings show that we were able to achieve high initial specific capacities (3070 mAhg-1 at the 10th cycle), which can be retained at values higher than those of graphite for a significant number of cycles (>120 cycles), depending on the structural properties of the aSi:H films. To our knowledge, this is the first comprehensive study of the influence of these properties of thin films with different doping levels and hydrogen distributions on their optimization and use as anodes in lithium-ion batteries.

Short-Process Regeneration of Highly Stable Spherical LiCoO2 Cathode Materials from Spent Lithium-Ion Batteries through Carbonate Precipitation.

High-efficacy recycling of spent lithium cobalt oxide (LiCoO2 ) batteries is one of the key tasks in realizing a global resource security strategy due to the rareness of lithium (Li) and cobalt (Co) resources. However, it is of great significance to develop the innovative recycle methods for spent LiCoO2 , simultaneously realizing the efficient recovery of valuable elements and the regeneration of high-performance LiCoO2 . Herein, a novel strategy of regenerating LiCoO2 cathode is proposed, which involves the preparation of micro-spherical aluminum (Al)-doped lithium-lacked precursor (Li2x Co1-x-y Al2/3y CO3, remarked as "PLCAC") via ammonium bicarbonate coprecipitation. The comprehensive conditions affecting particle growth kinetics, morphology and particle size the has been investigated in detail by physical characterizations and electrochemical measurements. And the optimized Al-doped LiCoO2 materials with high-density sphericity (LiCo1-z Alz O2 , remarked as "LCAO") shows a high initial specific capacity of 161 mAh g-1 at 0.1 C and excellent capacity retention of 99.5 % within 100 cycles at 1 C in the voltage range of 2.8 to 4.3 V. Our work provides valuable insights into the featured design of LiCoO2 precursors and cathode materials from spent LiCoO2 batteries, potentially guaranteeing the high-efficacy recycling and utilization of strategic resources.

Carbon-coated Ni0.5Mg0.5Fe1.7Mn0.3O4 nanoparticles as a novel anode material for high energy density lithium-ion batteries.

Lithium-ion batteries (LIBs) have gained considerable attention from the scientific community due to their outstanding properties, such as high energy density, low self-discharge, and environmental sustainability. Among the prominent candidates for anode materials in next-generation LIBs are the spinel ferrites, represented by the MFe2O4 series, which offer exceptional theoretical capacities, excellent reversibility, cost-effectiveness, and eco-friendliness. In the scope of this study, Ni0.5Mg0.5Fe1.7Mn0.3O4 nanoparticles were synthesized using a sol-gel synthesis method and subsequently coated with a carbon layer to further enhance their electrochemical performance. TEM images confirmed the presence of the carbon coating layer on the Ni0.5Mg0.5Fe1.7Mn0.3O4/C composite. The analysis of the measured X-ray diffraction (XRD) and Raman spectroscopy results confirmed the formation of nanocrystalline Ni0.5Mg0.5Fe1.7Mn0.3O4 before coating and amorphous carbon in the Ni0.5Mg0.5Fe1.7Mn0.3O4/C after the coating. The Ni0.5Mg0.5Fe1.7Mn0.3O4 anode material exhibited a much higher specific capacity than the traditional graphite material, with initial discharge/charge capacities of 1275 and 874 mA h g-1, respectively, at a 100 mA g-1 current density and a first coulombic efficiency of 68.54%. The long-term cycling test showed a slight capacity fading, retaining approximately 85% of its initial capacity after 75 cycles. Notably, the carbon-coating layer greatly enhanced the stability and slightly increased the capacity of the as-prepared Ni0.5Mg0.5Fe1.7Mn0.3O4. The first discharge/charge capacities of Ni0.5Mg0.5Fe1.7Mn0.3O4/C at 100 mA g-1 current density reached 1032 and 723 mA h g-1, respectively, and a first coulombic efficiency of 70.06%, with an increase of discharge/charge capacities to 826.6 and 806.2 mA h g-1, respectively, after 75 cycles (with a capacity retention of 89.7%), and a high-rate capability of 372 mA h g-1 at 2C. Additionally, a full cell was designed using a Ni0.5Mg0.5Fe1.7Mn0.3O4/C anode and an NMC811 cathode. The output voltage was about 2.8 V, with a high initial specific capacity of 755 mA h g-1 at 0.125C, a high rate-capability of 448 mA h g-1 at 2C, and a high-capacity retention of 91% after 30 cycles at 2C. The carbon coating layer on Ni0.5Mg0.5Fe1.7Mn0.3O4 nanoparticles played a crucial role in the excellent electrochemical performance, providing conducting, buffering, and protective effects.

Solid-state sodium batteries with P2-type Mn-based layered oxides by utilizing anionic redox

Solid-state sodium-metal batteries assembled with a composite solid-electrolyte separator and Na0.72Li0.24Mn0.75Si0.01O2 cathode, utilizing reversible cationic (Mn) and anionic (O) redox, achieve high initial specific capacity of 180 mA h g−1.