Initial Coulombic Efficiency Research Articles

Redefining closed pores in carbons by solvation structures for enhanced sodium storage

Closed pores are widely accepted as the critical structure for hard carbon negative electrodes in sodium-ion batteries. However, the lack of a clear definition and design principle of closed pores leads to the undesirable electrochemical performance of hard carbon negative electrodes. Herein, we reveal how the evolution of pore mouth sizes determines the solvation structure and thereby redefine the closed pores. The precise and uniform control of the pore mouth sizes is achieved by using carbon molecular sieves as a model material. We show when the pore mouth is inaccessible to N2 but accessible to CO2 molecular probes, only a portion of solvent shells is removed before entering the pores and contact ion pairs dominate inside pores. When the pore mouth is inaccessible to CO2 molecular probes, namely smaller than 0.35 nm, solvent shells are mostly sieved and dominated anion aggregates produce a thin and inorganic NaF-rich solid electrolyte interphase inside pores. Closed pores are accordingly redefined, and initial coulombic efficiency, cycling and low-temperature performance are largely improved. Furthermore, we show that intrinsic defects inside the redefined closed pores are effectively shielded from the interfacial passivation and contribute to the increased low-potential plateau capacity.

Achieving High Reversible Anionic Redox Activity of Li‐Rich Layered Oxides via Mg and Mo Co‐Doping

AbstractLi‐rich layered oxides (LLO) exhibit a distinctive anionic redox capability, enabling them to deliver exceptionally high specific capacity. However, the irreversibility of anionic redox in LLO gives rise to significant issues, including oxygen release and structure phase transitions. These challenges adversely affect performance, resulting in capacity and voltage degradation, thereby hindering the commercialization of LLO. Here, density functional theory (DFT) is employed to explore the electronic structure of LLO, and reveal that the incorporation of Mg and Mo elements into LLO enhances the overlap between the O 2p nonbonding orbital and the (TM─O)* antibonding orbital, thereby boosting anionic redox reversibility. Experimental results corroborate the theoretical predictions, demonstrating that the initial Coulombic efficiency rises from 80.8% to 90.1%, while capacity retention increases from 70.8% to 95.3% after 300 cycles at 1 C. Additionally, the full cell delivers a reversible capacity of 262.6 mAh g−1 at 0.1 C. This work presents a novel method for modifying the electronic structure of LLO through Mg and Mo co‐doping, offering new insights for the development of high‐performance lithium‐ion batteries.

Rapid Formation Strategy for Enhanced Electrochemical Performance of Hard Carbon Anodes in Sodium-Ion Batteries.

The conventional formation process of sodium-ion batteries (SIBs), which relies on low-current cycling, is one of the most energy-intensive and time-consuming steps in battery production, significantly contributing to overall manufacturing costs. This study systematically evaluates the formation of SIB pouch cells under different protocols and demonstrates that high-rate formation can achieve superior electrochemical performance. Our optimized high-rate formation process reduces formation time by 52.3% compared to the conventional method, presenting a cost-effective and efficient approach to SIB production. Notably, the accelerated formation process promotes the development of a denser, more uniform, and highly stable solid-electrolyte interphase (SEI) on the anode surface, enhancing initial Coulombic efficiency, capacity retention, and long-term cycling stability. These findings provide a promising strategy for improving the scalability and economic viability of SIB technology.

Realizing Environmentally Scalable Pre-Lithiation via Protective Coating of LiSi Alloys to Promote High-Energy-Density Lithium-Ion Batteries

Pre-lithiation using Li–Si alloy-type additives is a promising technical approach to address the drawbacks of Si-based anodes, such as a low initial Coulombic efficiency (ICE) and inevitable capacity decay during cycling. However, its commercial application is limited by the air sensitivity of the highly reactive Li–Si alloys, which demands improved environmental stability. In this work, a protective membrane is constructed on Li13Si4 alloys using low-surface-energy paraffin and highly conductive carbon nanotubes through liquid-phase deposition, exhibiting enhanced hydrophobicity and improved Li+/e− conductivity. The Li13Si4@Paraffin/carbon nanotubes (Li13Si4@P-CNTs) composite achieves a high pre-lithiation capacity of 970 mAh g−1 and superb environmental stability, retaining 92.2% capacity after exposure to ambient air with 45% relative humidity. DFT calculations and in situ XRD measurements reveal that the paraffin-dominated coating membrane, featuring weak dipole–dipole interactions with water molecules, effectively reduces the moisture-induced oxidation kinetics of Li13Si4@P-CNTs in air. Electrochemical kinetic analysis and XPS depth profiling reveal the enhancement in charge transfer dynamics and surface Li+ transport kinetics (SEI rich in inorganic lithium salts) in P-SiO@C pre-lithiated by Li13Si4@P-CNTs pre-lithiation additives. Benefitting from pre-lithiation via Li13Si4@P-CNTs, the pre-lithiated SiO@C(P-SiO@C) delivers high ICE (103.7%), stable cycling performance (981 mAh g−1 at 200 cycles) and superior rate performance (474.5 mAh g−1 at 3C) in a half-cell system. The LFP||P-Gr pouch-type full cell exhibits a capacity retention of 83.2% (2500 cycles) and an energy density of 381 Wh kg−1 after 2500 cycles. The Li13Si4@P-CNTs additives provide valuable design concepts for the development of pre-lithiation materials.

Research progress of silicon-based anode materials for lithium-ion batteries.

In recent years, with the rapid development of fields such as portable electronic devices, electric vehicles, and energy storage systems, the performance requirements for lithium-ion batteries have been continuously rising. Among the numerous key components of lithium-ion batteries, the performance of the anode materials plays a crucial role, as it is directly related to core indicators such as the energy density, cycle life, and safety of the batteries. Among them, silicon-based anode materials have stood out among many anode materials by virtue of their extremely high theoretical specific capacity, becoming one of the hot research directions in the field of lithium-ion battery anode materials at present. However, silicon-based anode materials have problems such as severe volume expansion, poor electrical conductivity, low initial coulombic efficiency, and unstable solid electrolyte interphase during the charging and discharging process, which limit their wide application and urgently require the seeking of new solutions. This paper comprehensively and in-depth introduces the research progress of silicon-based anode materials for lithium-ion batteries in recent years, focusing on the failure mechanisms and modification methods of silicon-based anodes, and provides effective solutions to the severe challenges faced in the commercialization process of silicon-based anodes.

Research Progress Of Polyacrylate Binders For Silicon-based Anodes In Lithium-ion Batteries.

Silicon (Si) has emerged as a preeminent candidate for next-generation lithium-ion batteries (LIBs) anodes, primarily attributed to its exceptionally high specific capacity. Nevertheless, the substantial volumetric expansion accompanying lithium alloying reactions has long posed a critical challenge to the commercial viability of silicon-based anodes. Binders as connectors between the active Si particles, conductive agents, and current collectors, playing a crucial role in stabilizing the structure of silicon anodes in LIBs. Polyacrylic acid (PAA) water-based binders contain abundant carboxyl groups (-COOH) that can enhance adhesive strength. However, simple linear PAA does not adequately accommodate the significant volume expansion of silicon anodes. To address this issue, various structural optimization strategies have been applied to modify PAA binders. In this context, a comprehensive review is conducted on the recently developed PAA-based binders, which cover linear, branched, and three-dimensional network configurations. A meticulous comparison is carried out regarding their initial coulombic efficiency, areal capacity, and material costs. Moreover, in-depth insights are offered to elucidate the mechanisms by which these structural modifications augment the properties of the binders and the performance of the cells. Ultimately, the prospective directions for the evolution of PAA-based binders designed for Si-based anodes in high-energy-density LIBs are deliberated.

Engineering Alkali Lignin Structure Modification: Enhanced Hard Carbon Electrolyte Interface Toward Practical Sodium Ion Batteries.

Hard carbon (HC) exhibits great potential as a promising candidate for sodium-ion batteries owing to its inherent advantages. However, the main challenges in utilizing HC stem from its low initial coulombic efficiency (ICE) and poor rate performance caused by its excessive surface defects. In this study, an effective strategy of employing alkali lignin (AL) is proposed, derived from pulp waste, as a binder for HC to create a uniform and inorganically enriched solid electrolyte interface. AL can modify the surface defects of HC through strong π-π interactions between the aromatic ring of AL and HC, while ingeniously grafting abundant active ─OH and ─COOH groups onto the electrode surface. The strong binder force between AL and electrolyte salts facilitates the formation of an ultra-thin NaF-rich solid electrolyte interface (SEI) layer (10 nm), thereby achieving an exceptional ICE of 91%. Furthermore, owing to its electrochemical activity, AL enables HC anode to exhibit an increasing slope capacity during cycling, compensating for capacity decay at high current densities. Consequently, when assembled into a full battery configuration, excellent rate performance is achieved with a reversible capacity of 282 mAh g-1 even at a current density of 5A g-1.

Double‑carbon protected pre-lithiated SiOx anode for lithium-ion storage with high initial Coulombic efficiency and long cycle life

Double‑carbon protected pre-lithiated SiOx anode for lithium-ion storage with high initial Coulombic efficiency and long cycle life

Construction of Cu4SnS4/CuS@C nanorods with high initial coulombic efficiency for lithium-ion batteries

Construction of Cu4SnS4/CuS@C nanorods with high initial coulombic efficiency for lithium-ion batteries

Revealing the storage mechanism of plateau-dominated S-doped hard carbon as high-performance anode for sodium-ion batteries

Revealing the storage mechanism of plateau-dominated S-doped hard carbon as high-performance anode for sodium-ion batteries

Synergistic Prelithiation and In Situ Nitrogen Doping via Li3N in SiO Anodes: A Dual-Benefit Pathway to Achieving Enhanced Li+ Kinetics and High Initial Coulombic Efficiency.

Silicon monoxide (SiO) has garnered significant attention as a promising anode material for high-energy-density lithium-ion batteries due to its lower volume expansion relative to pure silicon (Si) and its higher capacity compared to graphite. Nevertheless, the poor intrinsic electronic/ionic conductivity and the low initial Coulombic efficiency (ICE) of SiO result in inferior rate capability and inadequate practical energy density, hindering its commercial viability. Here, a simultaneous prelithiation and in situ nitrogen (N) doping approach for SiO utilizing lithium nitride (Li3N), which significantly enhances both the ICE and lithium-ion (Li+) diffusion kinetics, is proposed. N atoms are not only incorporated into the carbon layer on the surface of SiO but also form a uniformly distributed amorphous Li2SiN2 phase within the SiO, facilitating Li+ transport. Molecular dynamics simulations demonstrate that the Li+ diffusion coefficient of amorphous Li2SiN2 is significantly higher than that of other crystalline phases present in the prelithiated SiO matrix. The 1.5 Ah pouch cells further validate that the SiON-0.175/graphite||NCM811 exhibits a high ICE of 88.06%, and it retains 51.5% of its capacity even under 4C fast charging conditions. This study offers new insights into the development of next-generation SiO anode materials with high ICE and high-rate performance.

Surface and Interfacial Modulation of Lithium-Rich Manganese Layered Oxide Cathode Materials: Progress and Challenges.

Exhibiting exceptional energy density and capacity, lithium-rich manganese-based layered oxide (LLOs) cathode materials have garnered considerable attention and are emerging as strong contenders for future lithium-ion battery systems. However, the manner in which they are employed in practice is hindered by several challenges, such as voltage fading, exhibiting a low initial coulombic efficiency, and suboptimal cycling stability, mainly attributed to oxygen depletion and phase transformation phenomena. The current review primarily centers on recent progress in addressing these issues through surface and interfacial modification techniques, including surface doping, coating, and oxygen vacancy engineering. Other strategies, such as spinel phase engineering and hybrid coating layers, are also discussed as potential solutions to enhance electrochemical performance, stability, and capacity retention. Additionally, exploration advancements in electrolyte design aimed at stabilizing the LLOs/electrolyte interface, reducing side reactions, and enabling the development of a stable solid electrolyte interphase (CEI). The review concludes by highlighting ongoing challenges, particularly in improving long-term cycling stability, and proposes prospective research directions aimed at further unlocking the potential of LLOs cathode materials for practical battery applications.

Universal Single Atom Engineering Enhances Coulombic Efficiency of Ion Storage in Carbon Materials.

Metal single atoms are widely used to optimize the microstructure of carbon materials to improve their ion storage capacity and rate performance, but the impact on another key parameter, Coulombic efficiency (CE), is not sufficiently addressed and confirmed. Herein, a universal phenomenon is reported that carbon-loaded asymmetric sulfur-modified metal-N4 moiety (MN4-S, M = Zn, Fe, Cu, and Ni) possesses higher CE than the symmetric MN4 moiety, and this phenomenon is applicable to various of carbon matrices, ions (Li+, Na+, and K+), charge and discharge rates, and electrolyte formulations. The carbon-loaded asymmetric MN4-S moiety exhibits larger CEs (0.03-0.46% higher of average CEs, 4.2-28.4% higher of the initial CEs) and smaller variance compared to the MN4 moiety, implying better reversible stability. The mechanism driving this phenomenon is revealed by the ZnN4-S sodium storage process. The asymmetric MN4-S coordination promotes the rapid ions diffusion kinetics by changing the charge density. Meanwhile, the MN4-S moiety can reduce the adsorption energy of ions and regulate the surface chemical reactivity of the material to increase the reversibility of surface ion storage, thereby achieving higher CE and better stability.

N/O/S Tri‐Doped Hard Carbon From Polyaniline With Boosted Sodium‐Ion Storage

ABSTRACTIn this study, N/O/S tri‐doped polyaniline‐based hard carbons (D‐PANI‐HCs) have been synthesized through a sequential process involving in situ aniline polymerization, rotary evaporation, and subsequent calcination. The residual ammonium persulfate functions as a critical multifunctional precursor, simultaneously enabling heteroatom doping and acting as an in situ gaseous template during the calcination process. The resulting D‐PANI‐HCs demonstrates superior structural properties compared to undoped PANI‐HCs, including larger interlayer spacing, more closed nanopores and active sites. Therefore, the electrochemical performances of D‐PANI‐HCs as anode materials for sodium‐ion batteries demonstrate significant enhancement compared to undoped PANI‐HCs. Specifically, the initial Coulombic efficiency of D‐PANI‐HCs increases to 67.9%, up from 46.9% of undoped PANI‐HCs, while the specific capacity of D‐PANI‐HCs at 0.05 A·g−1 reaches 318 mAh·g−1, a notable improvement over the 175 mAh·g−1 for un‐doped PANI‐HCs. Furthermore, D‐PANI‐HCs exhibits excellent cycling stability, retaining 295 mAh·g−1 (92.5% retention) after 200 cycles at 0.05 A·g−1 and 171 mAh·g−1 (86.4% retention) after 1000 cycles at 0.3 A·g−1.

Catalysis-Induced Highly-Stable Interface on Porous Silicon for High-Rate Lithium-Ion Batteries

Silicon stands as a key anode material in lithium-ion battery ascribing to its high energy density. Nevertheless, the poor rate performance and limited cycling life remain unresolved through conventional approaches that involve carbon composites or nanostructures, primarily due to the un-controllable effects arising from the substantial formation of a solid electrolyte interphase (SEI) during the cycling. Here, an ultra-thin and homogeneous Ti doping alumina oxide catalytic interface is meticulously applied on the porous Si through a synergistic etching and hydrolysis process. This defect-rich oxide interface promotes a selective adsorption of fluoroethylene carbonate, leading to a catalytic reaction that can be aptly described as "molecular concentration-in situ conversion". The resultant inorganic-rich SEI layer is electrochemical stable and favors ion-transport, particularly at high-rate cycling and high temperature. The robustly shielded porous Si, with a large surface area, achieves a high initial Coulombic efficiency of 84.7% and delivers exceptional high-rate performance at 25 A g-1 (692 mAh g-1) and a high Coulombic efficiency of 99.7% over 1000 cycles. The robust SEI constructed through a precious catalytic layer promises significant advantages for the fast development of silicon-based anode in fast-charging batteries.

Confinement-Induced Stability Evolution of Na Clusters in Closed Pores of Hard Carbon: A DFT and AIMD Study.

Hard carbon (HC) is considered as the most promising anode material for sodium-ion batteries due to its disordered structure, high sodium storage capacity, and low cost. However, within the domain of low-voltage plateaus, the thermodynamic stability and kinetic evolution of Na clusters confined within microporous structures have remained inadequately characterized. In this work, the nucleation mechanisms as well as the thermodynamic stability of Na clusters are thoroughly investigated by density functional theory (DFT) and ab initio molecular dynamics (AIMD) methods based on a well-built disordered HC structure model. A new method to construct the HC model is applied by applying strain to achieve contraction of the carbon skeleton through DFT calculations to obtain the curved HC model. On the basis of the HC model, we calculated the confinement effect of the closed pore on the cluster by DFT calculations. We find that the bent carbon layer leads to an elevated electrostatic potential, which makes it easy to attract clusters, as well as a change in the configuration of the clusters, thus affecting the electron distribution within the clusters, leading to different cohesive energies and affecting the reversibility of the clusters. During the evolution of cluster dynamics, Na+ tends to form clusters in larger closed pores while it tends to fill the pore walls in smaller closed pores. This work provides theoretical guidance for improving the plateau capacity and initial Coulombic efficiency of sodium-ion batteries.

Polymer-Based Hard Carbons with Enhanced Initial Coulombic Efficiency for Practical Sodium Storage

Polymer-Based Hard Carbons with Enhanced Initial Coulombic Efficiency for Practical Sodium Storage

Direct Liquid-Phase Regeneration of Eluting Spent LiFePO4 Upgrade for Fast-Charging Cathodes Under Low Temperature and Ambient Pressure.

With the widespread adoption of lithium iron phosphate (LiFePO4, LFP)-based power batteries, it is anticipated that a huge volume of spent LFP cathodes will be generated in the near future. Therefore, it is imperative to develop advanced, ecofriendly, and efficient recycling technologies for spent LFP cathodes. In this work, a low-temperature direct hydrothermal regeneration strategy with a rapid eluting process is introduced for the spent LFP cathodes. This regeneration strategy can effectively achieve multiple goals, including supplementing Li+ ions, eliminating irreversible phase transitions, maintaining the bulk initial structure, and repairing the evenly carbon-coated layer. Moreover, the regenerated LFP can induce the formation of a thinner and more uniform CEI film during the initial charge-discharge process, achieving a fast Li+ ion diffusion rate, enhanced discharge capability, and improved structural stability. Thus, the regenerated LFP exhibits a high initial discharge capacity of 164.2 mAh g-1 at a 0.1 C rate with an initial Coulombic efficiency of 98% and 132 mAh g-1 at 5 C with a remarkable capacity retention rate of 93.1% after 800 cycles. Specifically, this direct regeneration method is shorter in process and lower in cost compared with the traditional hydrometallurgy, enabling an eco-friendly regeneration under a mild environment, which shows a huge development potential in industrial applications.

Microstructure and Electrochemical Performance of Li2CO3-Modified Submicron SiO as an Anode for Lithium-Ion Batteries.

Silicon monoxide (SiO) holds great potential as a next-generation anode material for commercial lithium-ion batteries due to its high theoretical specific capacity. However, poor cycling stability and low initial Coulombic efficiency (ICE) present substantial challenges for its practical application. Herein, we modified the structure of commercial SiO through ball milling, followed by heating with the addition of the network modifier Li2CO3. The submicrometer-sized SiO reduces Li+ diffusion pathways within the SiO bulk, facilitating the Li+ insertion/extraction process and enabling excellent rate performance. Controlling the size of silicon nanodomains within SiO enhances the structural stability of the material during cycling, thereby significantly improving its cycling stability. The increased crystallinity of SiO2 suppresses irreversible reactions, leading to a higher ICE. Moreover, Li+ ions trapped within the Si-O-Si network form a lithium silicate glass-like phase, which provides efficient pathways for Li+ diffusion within the material, thereby enhancing its electrochemical performance. The optimized submicrometer SiO was mixed with graphite and coated with carbon to produce a submicrometer SiO/graphite@carbon composite anode. When assembled into a half-cell, the composite anode exhibited an initial discharge specific capacity of 1277.0 mA h g-1 at 0.1 A g-1, with an ICE of 74.3%. And this anode demonstrated a capacity retention of 79.7% after 300 cycles at 0.5 A g-1. Furthermore, during rate capability testing, it achieved a discharge specific capacity of 428.9 mA h g-1 at 1.6 A g-1.

Molecular Stitching in Polysaccharide Precursor for Fabricating Hard Carbon with Ultra-High Plateau Capacity of Sodium Storage.

High energy density of sodium-ion batteries (SIBs) requires high low-voltage capacity and initial Coulombic efficiency for hard carbon. However, simultaneously achieving both characteristics is a substantial challenge. Herein, a unique molecular stitching strategy is proposed to edit the polymeric structure of common starch for synthesizing cost-effective hard carbon (STHC-MS). A mild air-heating treatment toward starch is employed to trigger the esterification reaction between carboxyl and hydroxy groups, which can effectively connect the branched polysaccharide chains thereby constructing a highly cross-linked polymeric network. In contrast with the pristine branched-chain starch, the cross-linking structured precursor evolves into highly twisted graphitic lattices creating a large population of closed ultramicro-pores (<0.3nm) enabling the storage of massive sodium clusters. Resultantly, STHC-MS delivers a reversible capacity of 348 mAh g-1 with a remarkable low-voltage (below 0.1V) capacity of 294 mAh g-1, which becomes more attractive by combining the high initial Coulombic efficiency of 93.3%. Moreover, STHC-MS exhibits outstanding stability of 0.008% decay per cycle over 4800 cycles at 1 A g-1. STHC-MS||Na3V2(PO3)4 full cells achieve an energy density of 266Wh kg-1, largely surpassing the commercial hard carbon-based counterpart. This work opens the avenue of molecular-level modulation in organic precursors for developing high-performance hard carbon in SIBs.