NiSb/nitrogen-doped carbon derived from Ni-based framework as advanced anode for lithium-ion batteries

Realizing fast-charging capability of silicon anode via ternary doping and structural disorder

Silicon (Si) is a potential fast-charging anode material for lithium-ion batteries (LIBs) due to its high energy density and suitable lithium insertion potential. However, the slow kinetics and significant volume changes during lithiation/delithiation hinder its practical application. High-entropy alloying of silicon enhances electronic conductivity and mitigates volume expansion, leading to improved rate performance. Nevertheless, the synergistic effects of high-entropy alloying and crystal structure on silicon-based anodes remain underexplored. Herein, a ternary doping alloy (Si-FeTiP) anode material with an amorphous structure was prepared via high-energy ball milling. The uniformly distributed microcrystalline phases of FeSi2 and TiP enhanced the electronic conductivity and structural stability of the Si anode. The local disordered structure of the amorphous silicon phase mitigates lithiation-induced stress, while the isotropic nature of the amorphous structure facilitates excellent Li+ diffusion kinetics in the Si-FeTiP composite. As a result, the Si-FeTiP anode exhibits an excellent rate capability of 658 mAh g-1 at 10 A g-1 and a capacity retention of 80.3 % after 500 cycles at 2 A g-1. This study enhances our understanding of how crystal structure influences ion transport and electrochemical performance. Furthermore, it provides valuable insights for the design of multivariate fast-charging silicon-based anode materials.

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.

Porous carbon with the synergistic effect of cellulose fibers and MOFs as the anode for high-performance Li-ion batteries

The commercial graphene for Li ion batteries (LIBs) has high cost and low capacity. Therefore, it is necessary to develop a novel carbon anode. The cellulose nanowires (CNWs), which has advantages of low cost, high carbon content, is thought as a good carbon precursor. However, direct carbonization of CNWs leads to low surface area and less mesopores due to its easy aggregation. Herein, the metal-organic frameworks (MOFs) have been explored as templates to prepare porous carbon due to their 3D open pore structures. The porous carbon was developed with the coordination effect of CNWs and MOFs. The precursor of MOFs coordinates with the -OH and - COOH groups in the CNWs to provide stable structure. And the MOFs was grown in situ on CNWs to reduce aggregation and provide higher porosity. The results show that the porous carbon has high specific capacity and fast Li+/electronic conductivity. As anode for LIBs, it displays 698 mAh g-1 and the capacity retention is 85 % after 200 cycles. When using in the full-battery system, it exhibits energy density of 480 Wh kg-1, suggesting good application value. This work provides a low-cost method to synthesize porous carbon with fast Li+/electronic conductivity for high-performance LIBs.

NiM (Sb, Sn)/N-doped hollow carbon tube as high-rate and high-capacity anode for lithium-ion batteries

Alloy-type materials are regarded as prospective anode replacements for lithium-ion batteries (LIBs) owing to their attractive theoretical capacity. However, the drastic volume expansion leads to structural collapse and pulverization, resulting in rapid capacity decay during cycling. Here, a simple and scalable approach to prepare NiM (M: Sb, Sn)/nitrogen-doped hollow carbon tubes (NiMC) via template and substitution reactions is proposed. The nanosized NiM particles are uniformly anchored in the robust hollow N-doped carbon tubes via NiNC coordination bonds, which not only provides a buffer for volume expansion but also avoids agglomerating of the reactive material and ensures the integrity of the conductive network and structural framework during lithiation/delithiation. As a result, NiSbC and NiSnC exhibit high reversible capacities (1259 and 1342 mAh/g after 100 cycles at 0.1 A/g) and fascinating rate performance (627 and 721 mAh/g at 2 A/g), respectively, when employed as anodes of LIBs. The electrochemical kinetic analysis reveals that the dominant lithium storage behavior of NiMC electrodes varies from capacitive contribution to diffusion contribution during the cycling corresponding to the activation of the electrode exposing more NiM sites. Meanwhile, M (Sb, Sn) is gradually transformed into stable NiM during the de-lithium process, making the NiMC structure more stable and reversible in the electrochemical reaction. This work brings a novel thought to construct high-performance alloy-based anode materials.

Oxygen Defect and Cl--Doped Modulated TiNb2O7 Compound with High Rate Performance in Lithium-Ion Batteries

TiNb2O7 has attracted extensive attention from lithium-ion battery researchers due to its superior specific capacity and safety. However, its poor ion conductivity and electron conductivity hinder its further development. To improve the ion/electron transport of TiNb2O7, we report that chlorine doping and oxygen vacancy engineering regulate the energy band and crystal structure simultaneously through a simple solid-phase method. NH4Cl was used to realize Cl- doping and oxygen vacancy production. A Rietveld refinement demonstrates an effective substitution of Cl in the O sites of Nb-O octahedra, with an enlarged crystal plane spacing. The oxygen vacancies provide more active sites for lithium intercalation. The diffusion coefficient of Li+ is inceased from 2.39 × 10-14 to 1.50 × 10-13 cm2 s-1, which reveals the positive influence of Cl- doping and oxygen vacancies on the promoted Li+ transport behavior. Charge compensation is introduced by the doping of Cl- and the generation of oxygen vacancies, leading to the formation of Ti3+ and Nb4+ and the adjustment of the electronic structure. DFT calculations reveal that TiNb2O7 with Cl- doping and an O vacancy shows a metallic property with a finite value at the Fermi level, which is conducive to electron transfer in the electrode material. Benefiting from these advantages, the modified TiNb2O7 presents superior rate performance with a commendable capacity of 172.82 mAh g-1 at 50 C. This work provides guidance to design high-performance anode materials for high-rate lithium-ion batteries.

High-Rate-Capacity Cathode Based on Zn-Doped and Carbonized Polyacrylonitrile-Coated Na4MnV(PO4)3 for Sodium-Ion Batteries

Na₄MnV(PO₄)₃ (NMVP) is a promising cathode material for sodium-ion batteries (SIBs) because of its extraordinary three-dimensional structure that provides plenty of channels for sodium-ion migration. However, the unsatisfied electrical conductivity of NMVP limits its utilization in SIBs. Herein, Zn-doped NMVP with a uniform carbonized polyacrylonitrile (PAN) coating layer, named NMZVP@cPAN, was synthesized via a sol-gel method, and carbonized PAN was uniformly distributed on the surface of NMVP. Therefore, the NMZVP@cPAN cathodes exhibited an outstanding discharge capacity of 70.6 mA·h·g^-1 at 30 C and remarkable cycling stability with an admirable retention of 89.64% after 1000 cycles at 5 C. Rietveld refinement and ex situ X-ray diffraction analyses were performed to determine the change in the crystal structure. Density functional theory calculations were performed to determine the effects of Zn doping on the density of states and the migration energy barriers. Finally, the NMZVP@cPAN cathodes were successfully modified and could be used in SIBs as NMVP cathodes.

Boosting cycling stability through Al(PO3)3 loading in a Na4MnV(PO4)3/C cathode for high-performance sodium-ion batteries

Mn-based NASICON-type Na₄MnV(PO₄)₃ (NMVP) has been widely investigated as one of the most promising alternatives to Na₃V₂(PO₄)₃ cathodes for sodium-ion batteries (SIBs) due to its higher energy density, higher abundance, and lower cost and toxicity compared to V. However, electrochemical performance for large-scale applications is limited by NMVP's inferior conductivity and structural degradation during cycling. Herein, a facile strategy to modify the surface/interphase properties of NMVP/C was reported using the thermally stable Al(PO₃)₃ precursor with a wet process followed by heat treatment to enhance the interface stability of electrodes. The nanomodified layer has the benefits of an ionic conductor (slight NaPO₃) and robust composite (Al(PO₃)₃), which can facilitate the stability of Mn-based cathode materials and ionic conductivity. These merits endow 1 wt% Al(PO₃)₃-loaded NMVP/C cathodes with a high rate performance (102/61 mAh g^-1 at 0.2/50 C) and impressive cyclability (88.5%/89.7% at 5 C/10 C after 3000/4000 cycles) in Na-ion batteries at 2.5-3.8 V. Moreover, when the cutoff voltage is raised to 4 V, improved electrochemical properties (111.6/50.8 mAh g^-1 at 0.2/10 C and 71.4% after 1000 cycles at 5 C) are also realized. Such an enhancement indicates that facial surface modification engineering limits organic electrolyte erosion, inhibits transition metal dissolution and suppresses surface lattice degradation, which is confirmed by ex situ X-ray diffractometry and transmission electron microscopy. Therefore, the Al(PO₃)₃ surface modification strategy combined with mechanism analysis can provide a possible reference for advanced electrochemical properties in energy storage devices.

Pulsed Current Boosts the Stability of the Lithium Metal Anode and the Improvement of Lithium-Oxygen Battery Performance

Lithium-oxygen batteries have received extensive attention due to their high theoretical specific capacity, but problems such as high charging overpotential and poor cycling performance hinder their practical application. Herein, a pulsed current, which merits its relaxation phenomenon, is applied during the charging cycle to address the abovementioned problems. Pulsed charging can not only reduce the charging overpotential, but also control the mass transfer and distribution of lithium ions. As a result, the uniform deposition of lithium ions on the anode surface is realized, the repeated rupture and formation of the solid electrolyte interphase is reduced, and the growth of the lithium dendrites is successfully suppressed, thereby achieving the purpose of protecting lithium metal from excessive consumption. When the pulsed charging duty ratio (Ton/Toff) is 1:1, after 25 cycles, the lithium-oxygen battery anode still presents a relatively flat and dense deposition surface, which is obviously better than the loose and rough surface after normal cycling. In addition, the protective effect of pulsed charging on the lithium metal anodes of lithium-oxygen batteries is also verified by the construction of other lithium-based batteries.