High Initial Coulombic Efficiency Research Articles

Storage Stability of pre-lithiation agent Li6CoO4: Exposed to components of dry air and moist gases

Pre-lithiation is a critical technology in the field of lithium-ion batteries (LIBs). The unfavorable storage conditions of the pre-lithiation agent Li6CoO4 (LCO) lead to harmful surface reactions, resulting in poor electrochemical performance and limiting its practical application. In this work, we have synthesized LCO with high initial charge capacity (826.5 mAh g-1) and low coulombic efficiency (6.5%). Ex-situ XRD reveals the structural evolution of the LCO material during the first charge and the O2 evolution was measured by differential electrochemical mass spectrometry (DEMS), and the de-lithiation mechanism of LCO was proposed. On the other hand, the formation of non-active LiOH and Li2CO3 impurities on the surface of the material under different storage conditions was revealed by Raman spectroscopy. According to the results of LCO materials stored in different air components, it can be found that moisture and CO2 are the key factors causing the degradation of LCO materials, and LCO materials in dry environment or protective atmosphere have good storage stability.

Solid-Liquid-Solid Growth of Doped Silicon Nanowires for High-Performance Lithium-Ion Battery Anode

Silicon nanowires (SiNWs) have great potential in electronic devices, sensors, energy storage, and conversion devices. Despite various ways to synthesize SiNWs, however, the growth of SiNWs directly from stable, abundant, sustainable silica sources has yet to be achieved. Herein, we report a modified alumino-reduction process of the silica to produce tin (Sn)-doped SiNWs that can be initiated at low temperature (250 °C) based on a solid-liquid-solid growth mechanism in analogy to the well-known vapor-liquid-solid (VLS). In this growth process, the reduced silicon atoms migrate freely in the molten salt and alloy with pre-reduced Sn. The supersaturation of silicon in the Sn-Si alloy leads to the precipitation of single-crystal SiNWs. The prepared SiNWs are of excellent crystallinity and doped with high non-equilibrium concentration (~3.0at.%) of Sn. This process with the solid-liquid-solid mechanism can also be extended to produce other group IV elements-based nanowires such as germanium. In addition, the prepared Sn-doped SiNWs as the anode material in lithium-ion batteries exhibit excellent performance with a high initial Coulombic efficiency of 85.4%, and a substantial reversible capacity of 1133 mAh g-1 even after 500 cycles at 4Ag-1. By utilizing the solid-liquid-solid mechanism, this modified alumino-reduction process offers a novel route for synthesizing doped SiNWs, holding promise for diverse applications.

Spatially confined transition metals boost high initial coulombic efficiency in alloy anodes.

Alloy-type materials hold significant promise as high energy density anodes for lithium-ion batteries. However, the initial coulombic efficiency (ICE) is significantly hindered by the poor reversibility of the conversion reaction and volume expansion. Here, the NiO/SnO2 multilayers with a hybrid interface of alloy and transition metal oxides are proposed to generate Ni nanoparticles within confined layers, catalyzing Li2O decomposition and suppressing the coarsening of Sn or Li2O particles. Supported by density functional theory (DFT) calculations and revealed by operando magnetometry, the spatially confined, well maintained Ni active sites lower the energy barrier for Li-O bond rupture and enhance the migration dynamics of Li+. The enhanced reaction kinetics lead to achievement of an impressive ICE of 92.3% and a large capacity of 1247 mA h g-1 with 97% retention after 800 cycles. Furthermore, the NiO/SnO2 anode exhibits excellent electrochemical performances in both Na/K-ion batteries. Notably, when constructed with the same framework, SiO2 also delivers significantly improved lithium storage properties with ultra-high ICEs. This work paves the way for advanced designs of alloy-type anodes that satisfy both ICE and overall electrochemical performance.

Strategies for designing high-performance hard carbon anodes with enhanced lithium-ion diffusion and rate capability

The performance of the electrodes is closely related to the structure of the electrode sheet, and the construction of advanced electrodes is crucial for the lithium-ion diffusion process in high-performance lithium-ion batteries (LIBs). Hard carbon, with its irregular polycrystalline microstructure, is an ideal candidate material for the anode electrode of LIBs. However, its have some drawbacks such as low initial coulombic efficiency (ICE), low capacity and poor rate performance. In this work, two electrode casting approaches are proposed and tested in pouch cells, which are double-layer blade coated electrode and patterned coated electrode. The results show that both coating methods show a combination of high ICE and rate capability, exceeding the performance of conventional single-coated electrodes composed of the same material. The designed coating method improves the dynamics of lithium ion diffusion process in the electrode, and the magnification performance and comprehensive electrochemical performance are improved. The research has a wide application prospect and can provide design guidance for obtaining high-power batteries.

Mechanically Induced Surface Defect Engineering in Expanded Graphite to Boost the Low-Voltage Intercalation Kinetics for Advanced Potassium-Ion Batteries

Enhancing carbon materials' low-potential K+ intercalation capacity is an essential topic in potassium-ion batteries (PIBs). Nevertheless, conventional methods effectively improve performance by increasing the surface area and active sites, but always at the expense of initial coulombic efficiency (ICE). Herein, an efficient and convenient strategy is proposed to construct self-doped defective carbon nanosheets (SDCS) using the mechanical ball-milling technique. This in situ defect engineering increases K+ intercalation sites and shortens the ionic pathway, enhancing the ionic intercalation kinetics, specific capacity, and ICE. As expected, the SDCS-24 electrode delivers an ultra-high low-potential capacity of 314.3 mAh g-1 below 0.5 V, high ICE of 76.1%, and long-term cycle stability (300.1 mAh g-1 after 1800 cycles at 1 C). The K+ storage mechanism is determined by ex situ XRD and in situ Raman. The full-cell with 3,4,9,10-Perylenetetracarboxylic dianhydride cathode and SDCS-24 anode further confirms its promising application. This work presents a strategy for designing self-doped defective carbons in situ and provides insights into the potassium storage mechanism at low potential.

Nonporous TiO2@C microsphere with a highly integrated structure for high volumetric lithium storage and enhance initial coulombic efficiency

To enhance the volumetric energy density and initial coulombic efficiency (ICE) of titanium oxide (TiO2) as anode electrode material for lithium-ion batteries (LIB), this study employed a surface-confined in-situ inter-growth mechanism to prepare a TiO2 embedded carbon microsphere composite. The results revealed that the composite exhibited a highly integrated structure of TiO2 with oxygen vacancies and carbon, along with an exceptionally small specific surface area of 11.52 m2/g. Due to its unique microstructure, the composite demonstrated remarkable lithium storage properties, including a high ICE of 75%, a notable capacity of 426.8 mAh/g after 200 cycles at 0.2 A/g, superior rate performance of 210.1 mAh/g at 5 A/g, and an outstanding cycle life, with a capacity decay rate of only 0.003% per cycle over 2000 cycles. Furthermore, electrochemical kinetic studies further validated the advantages of this microstructure.

Dual-Substitution Strategy Utilizing Cation Chelation and Assembly Process to Realize Solid Solution Reaction in Layered Oxide Cathode for Na-Ion Batteries.

Na0.67Ni0.33Mn0.67O2 (NNM) is regarded as a promising cathode material for Na-ion batteries (NIBs), but suffers from irreversible phase transformations characterized by multiple voltage plateaus, resulting in poor cycle stability and inferior rate capability. To address these issues, the Na0.67Ni0.18Cu0.10Zn0.05Mn0.67O2 (NNCZM) cathode material is synthesized by a cation chelation and reassembly process, which can promote a more uniform element distribution than that prepared by the solid-state method (S-NNCZM), resulting in better Na+ diffusion kinetics and rate capability. Replacing Ni2+ with a small amount of Zn2+ prevents the P2-O2 phase transformation, while replacing Ni2+ with an appropriate amount of electrochemically active Cu2+ eliminates Na-vacancy ordering and additionally contributes to capacity. Thus, the dual substitution of Cu2+ and Zn2+ for Ni2+ makes the NNCZM electrode synergistically achieve a complete solid solution reaction and better cycling stability. Accordingly, it exhibits a large discharge capacity (110.2 mA h g-1 at 10 mA g-1) with a high initial coulombic efficiency (97.3%), remarkable cycle stability with 84.1% capacity retention over 200 cycles at 200 mA g-1, and excellent rate capability with a discharge capacity of 61.0 mA h g-1 at 2000 mA g-1, significantly outperforming the NNM and S-NNCZM electrodes.

An Advanced 3D Crosslinked Conductive Binder for Silicon Anodes: Leveraging Glycerol Chemistry for Superior Lithium‐Ion Battery Performance

AbstractSilicon (Si) anodes hold great promise for high‐capacity lithium‐ion batteries (LIBs), yet their practical application is hindered by severe volume expansion and mechanical degradation. To tackle these challenges, we present an innovative 3D crosslinked conductive polyoxadiazole (POD) binder engineered with glycerol (GL) to form a robust network of covalent and hydrogen bonds. This unique chemical architecture not only enhances adhesion and mechanical resilience to effectively dissipate the stresses induced by Si's volumetric changes but also constructs a robust conductive framework to facilitate electron transfer. The dynamic interplay between strong covalent and flexible hydrogen bonds in the POD‐c‐GL binder enables superior structural integrity and stable solid‐electrolyte interphase (SEI) during cycling. The Si@POD‐c‐GL anode exhibits remarkable electrochemical performance, including a high initial Coulombic efficiency, impressive rate capability, and outstanding cycling stability. This work highlights the potential of harnessing in situ crosslinking chemistry to develop advanced binders, paving the way for the next generation of high‐performance Si anodes in LIBs.

Long‐Durable Potassium Ion Batteries Enabled by Medium‐Entropy Lattice Engineering on Prussian Blue Analogues Cathodes

AbstractGiven their structural merits and electrochemical benefits, Prussian blue analogues (PBAs) hold great promise as cathode materials for potassium ion batteries (PIBs). However, these cathodes face formidable hurdles by structural failure and poor rate capability, primarily resulting from significant volumetric changes and sluggish kinetics during repeated intercalation/deintercalation of bulky K+ ions. Theoretically, the study reveals explicitly that quaternary medium‐entropy PBAs (Q‐ME‐PBAs), composed of Fe, Ni, Co, and Cu, demonstrate minimal lattice volume variations and low diffusion barriers during K+ ion interactions. This endows Q‐ME‐PBA with favorable ability to induce significant 3D lattice distortion, enabling the material to endure structural alterations during K+ ion movements and reinforce phase stability. Consequently, leveraging the structural and compositional advantages, the resultant Q‐ME‐PBAs cathode showcases exceptional cycling performance, maintaining over 90% capacity retention after 300 cycles at 0.25 C with a high initial coulombic efficiency of 94.4% and retaining 74.7% capacity even after an ultra‐long 10 000 cycles at 3.75 C over 147 days. Notably, full cells paired with hard carbon and graphite anodes show outstanding cycling stability and rate capability. This study charts fresh design directions for crafting high‐performance and durable cathodes through medium‐entropy lattice engineering for advanced PIBs.

Electrolyte Engineering of Hard Carbon for Sodium‐Ion Batteries: From Mechanism Analysis to Design Strategies

AbstractThe hard carbon (HC) anodes with desirable electrochemical performances including high initial Coulombic efficiency, superior rate performance and long‐term cycling play an indispensable role in the practical application of sodium ion batteries (SIBs), which are closely related to the electrolytes them matched. Fully analyzing the mechanism of electrolyte engineering for HC anodes is crucial for promoting the commercialization of SIBs, but is still lacking. In this review, the correlation between physicochemical properties of the electrolyte and the electrochemical performance of HC is first summarized. And point out the crucial role of electrolyte properties, including ion conductivity, de‐solvation energy, and interface passivation ability for the Na+ storage in HC. Then, the formation process, composition, as well as structure of solid electrolyte interphase (SEI) on HC surface are mainly discussed, and the structure‐activity relationship of SEI is analyzed in depth. Moreover, based on the mechanism analysis, relevant electrolyte design strategies have been summarized. Finally, the challenges and future development directions of the electrolyte engineering of HC are proposed. This review is expected to provide professional theoretical guidance for the development of electrolyte and contribute to the rational design of high‐performance HC anodes, promoting the industrialization of SIBs.

Chiral electrolytes for rechargeable metal batteries

Charge transfer at the liquid (electrolyte)-solid (metal) interfaces is of fundamental importance to metal electrochemical deposition that further determines the reversibility and kinetics of energy-dense rechargeable metal batteries (RMBs). We demonstrate the fast charge transfer at the electrolyte-metal interfaces for lithium metal by designing and synthesizing electrolytes with chiral solvents: R (or S)-1,2-dimethoxypropane (R-DMP or S-DMP) and R (or S)-4-methyl-1,3-dioxolane (R-MDOL or S-MDOL). The chiral-induced spin selectivity is considered to produce spin-polarized metal surfaces, enabling the improvement in charge transfer rate and efficiency. The deposited Li metal in chiral electrolytes shows smooth and uniform morphologies, as well as high initial (>95%) and average (∼99.2%) Coulombic efficiency for Li metal stripping/plating process, thus prolonging the life-span of batteries using thin lithium anode (50 μm) to 400 cycles till 80% capacity retention. This work provides a distinct approach to regulate metal deposition beyond the limitation of ion de-solvation.

Enhanced lithium-ion storage through anchoring nanocrystalline MoO2/C microspheres in rGO nanosheets: Boosting pseudocapacitance and facilitating rapid conversion

Both crystalline and amorphous MoO2 exhibit distinct advantages for lithium-ion battery applications, with the former favoring lithium-ion intercalation and the latter undergoing complete lithiation via a conversion reaction. However, their sluggish lithium-ion insertion rates and inadequate charge transfer kinetics hinder their full potential. To address these challenges, we have developed a controllable approach that integrates liquid-phase dispersion of the HxMoO3/C and graphene oxides (GO) precursors followed by freeze-drying and low-temperature calcinations, aiming to merit the ionic conductivity of MoO2/C nanocrystallite and the electronic conductivity of reduce graphene oxides (rGO), respectively. This facile method yields bubble-sheet-like MoO2/C@rGO composites, where the quantitatively strategic incorporation of rGO can effectively mitigate recrystallization and surface oxidation of MoO2 nanocrystals. Furthermore, the approximately 70 % volume shrinkage of HxMoO3/C precursors into MoO2/C can create a flexible void space between the microspheres and the rGO coating for better accommodating volume variations during lithiation. Electrochemical measurements show that MoO2/C@rGO delivers high initial coulombic efficiency (ICE, e.g., up to 71.3 % at 100 mA g⁻¹), impressive rate performance (e.g., achieving 60 mA h g⁻¹ at 1 A g⁻¹, and 34.1 % retention from 0.1 to 2 A g⁻¹) and excellent cyclability (e.g., retaining 98.9 % of its capacity after 200 cycles) when employed as an intercalation-type anode material above 1.00 V (vs. Li/Li⁺). Remarkably, electrochemical analysis indicates that the capacitive contribution is dominant during high-rate applications (e.g., up to 73.06 % ratio at a scan rate of 0.50 mV s⁻¹), exhibiting a pseudocapacitive behavior. Additionally, MoO2/C@rGO exhibits enhanced ICE (e.g., up to 76.9 % at 100 mA g⁻¹), accelerated activation (e.g., achieving peak performance within 10 cycles at 100 mA g⁻¹), superior rate performance (e.g., achieving 446 mA h g⁻¹ at 2 A g⁻¹), and remarkable cyclability (e.g., maintaining 510 mA h g⁻¹ with 88.9 % capacity retention over 600 cycles at 1 A g⁻¹) when applied as a conversion-type anode material at between 1.00 and 3.00 V (vs. Li/Li⁺). To elucidate the mechanisms underlying the high-rate performance and the increased capacity, ex-situ XRD, ex-situ SEM, ex-situ TEM, and electrochemical analysis were carried out. No evident phase transition or material pulverization can be observed upon cycling above 1.00 V; therefore, the structural evolution is entirely single-phase or solid-solution, which accompanies with pseudocapacitive characteristic. However, the diffraction peaks downshift, the eminent of LixMoO2+δ, the pulverization, and the gradual amorphization of MoO2 can be observed upon cycling, indicating an sequential intercalation-to-conversion activation from a crystalline state to an amorphous state.

Molecular Engineering Chemical Pre-lithiation Reagent with Low Redox Potential for Graphite Anode Enables High Coulombic Efficiency.

Graphite (Gr) is a low-cost and high-stability anode for lithium-ion batteries (LIBs). However, Gr anode exhibits an obstinate drawback of low initial Coulombic efficiency (ICE), owing to the active lithium loss for the solid electrolyte interphase (SEI) layer. Herein, a straightforward and effective chemical pre-lithiation strategy is proposed to compensate for the lithium loss. A molecular engineering phenanthrene-based lithium-arene complex (Ph-based LAC) reagent is designed by density functional theory (DFT) calculations. The engineering Ph-based reagent enhances the stability of the π-electron system and the electron-donating capacity, resulting in a reduced redox potential to facilitate lithium transfer. The electrochemical distinct of the Ph-based reagent is illustrated, the prelithiation process in a low Li-insertion platform, and the lithiation degree is controllable with the dipping time (ICE = 102%, 3min). Notably, a denser and homogeneous SEI layer has pre-formed to enhance the Li+ transport and interface stability. Moreover, the lithium-ion full batteries assemble with LiFePO4 and NCM811 cathode, which exhibits high ICE (96.5% and 90.3%) and energy density (310 and 333Whkg-1). These findings present a facile and controllable pre-lithiation strategy to compensate for the lithium of LIBs, providing new valuable insights into the design and optimization of battery manufacture.

Impact of Na-Carboxymethyl Cellulose Binder Type on Hard Carbon Performance and SEI Formation in Sodium-Ion Batteries.

The development of hard carbon (HC) electrodes using biobased binders, formulated in water solvent, is of great interest for Na-ion batteries. Five Na-carboxymethyl cellulose (CMC) binders with different molecular weights and degrees of substitution were investigated. The increase in the CMC molecular weight led to an increase in the volume of water necessary for slurry preparation and a decrease in the electrode mass loading. Moreover, the adhesion of the slurry was strongly impacted by the aluminum current collector properties. A high initial Coulombic efficiency, iCE (up to ∼90%), and reversible capacity (up to 334 mAh g-1 at C/10) were obtained in Na half-cells. Post-mortem XPS analyses performed on several electrodes under various conditions allowed a better understanding of the formation and composition of the solid electrolyte interphase (SEI) layer. The genesis of SEI was initially chemically driven: to a small extent, by HC and to a greater extent, by the Na metal. However, SEI formation was mainly governed by the electrochemical-driven degradation of the electrolyte salt and solvent. The SEI layer composed of an inorganic-rich core and an organic-rich shell significantly decreased the resistance of the HC electrode, allowing superior iCE while maintaining high capacity retention (96.2%), after 100 cycles at 1C.

In-situ construction of dual-coated silicon/carbon composite anode for fast-charging Li-ion batteries

Silicon (Si) is regarded as a promising candidate anode for next-generation high-energy–density batteries due to its ultrahigh theoretical capacity of 4200 mAh g−1. However, silicon anodes face tremendous challenges during cycling, including huge volume expansion, highly unstable interfaces and inherently low conductivity. In this study, the dual-coated silicon/carbon composite anode (Si@SiOx@C) with high silicon content of 85 % is obtained by high-energy ball milling and combined with phenolic resin-assisted encapsulation. The amorphous SiOx layer (∼3 nm) facilitates the rapid Li+ transport and mitigates the volume expansion, while the hard carbon layer (∼3 nm) improves the electronic conductivity and helps to protect against silicon oxide layer erosion from electrolyte, synergistically contributing to the fast-charging performance. With the synergistic effect of dual coating, the Si@SiOx@C anode shows a high initial Coulombic efficiency of 91 % and maintains a high capacity of 1250 mAh g−1 even after 500 cycles at a high rate of 4 A/g. Moreover, the volume expansion of silicon anode during cycling is significantly reduced. This work provides a novel strategy for high silicon content anode in developing fast-charging batteries through dual-coating regulation.

Bridging sodium storage behavior and microstructure in broad-leaf lignin hard carbon for sodium-ion batteries

Hard carbon (HC) has emerged as the most promising anode material for the sodium ion battery because high theoretical capacity and cost-effective properties. However, unsatisfactory specific capacity and initial Coulombic efficiency (ICE) significantly impede its further advancement. Moreover, the correlation between the microstructure and electrochemical performance has been not thoroughly elaborated. Here, a straightforward approach to regulate the closed nanopore and defect structure in the hard carbon matrix by adjusting the pyrolysis temperatures. Higher pyrolysis temperature will promote the growth of a long carbon chain and further fold and shrink generating more closed nanopores, which was beneficial to improve the Na+ plateau capacity. The long-range ordered turbostratic graphite domain structure should be avoided, as it can lead to a reduction in reversible capacity. Through detailed analysis of the hard carbon microstructure evolution and electrochemical performance, the relationship of which has been established. Simultaneously, the optimized hard carbon pyrolyzed at 1500 °C displays a remarkable reversible specific capacity of 338 mAh g-1 at 0.1 C with a high ICE of 87%. Based on the detailed analysis, a microstructure-dependent mechanism ‘adsorption-intercalation-filling’ was proposed for a comprehensive understanding of the sodium ion storage behavior. More significantly, fabricated 18650 cylindrical batteries demonstrate a high reversible capacity of 1175 mAh at 0.1 C with outstanding cycle stability (82.9% after 225 cycles at 0.5 C), outperforming commercial hard carbon counterparts. Our work provides deep insight into the rational design of the hard carbon structure and provides the possibility of building practical SIBs with high performance.

Enabling High-Voltage Stability in Solid-State Battery Cathodes with ALD Coatings

Solid-state batteries (SSBs) promise improved safety and energy density by using solid electrolytes (SEs) and high-voltage cathodes. However, the SEs are unstable at high voltages, leading to oxidative chemical decomposition at the SE/CAM (cathode active material) interface, resulting in the formation of an insulating cathode-electrolyte interface (CEI) on CAM particles [1]. The layered oxide cathodes (LiNixMnyCozO2; NMC), when cycled at elevated voltages (>4.3V), undergo irreversible structural and chemical deformations, including the formation of kinetically less active phases (spinel and rock-salt), oxygen evolution, and mechanical degradation (intergranular or intraparticle cracking) [2]. The instability of the SE, CAM particles, and SE/CAM interface, collectively, results in inferior electrochemical performance, including low initial Coulombic efficiency (CE), increased cell polarization and impedance, reduced rate capability, and capacity fade during extended cycling.Therefore, it is crucial to stabilize the SE/CAM interface and preserve the CAM structure in SSB cathodes, particularly during high-voltage cycling. This is primarily achieved by developing a protective coating on CAM particles. Niobium (Nb)-based coatings are promising to protect the SE/CAM interface, mostly developed by wet chemical and solid-state processing routes that involve high-temperature annealing. On the other hand, atomic layer deposition (ALD) is a powerful technique for coatings, providing precise thickness and composition control [3]. Unfortunately, these coatings may have ‘hot spots’ for local current focusing (crystalline defects, i.e., grain boundaries) and oxygen release (pinholes at particle-particle contacts) [4].In the present study, we developed an Nb-based thin conformal amorphous coating on single crystal NMC CAM particles using ALD equipped with a rotary bed attachment. Unlike traditional stationary ALD reactors, ALD with a rotary bed attachment ensures a pinhole-free continuous coating on CAM powders. The low-temperature ALD process results in an amorphous coating (chemically and structurally isotropic), which is expected to effectively withstand the volumetric changes occurring in CAM particles during repetitive charge/discharge cycling. Comparing the performance of uncoated and coated samples tested at high voltages (≥4.5V) shows that the coated cathodes display significant improvements, including high initial Coulombic efficiency (91% vs. 83%), enhanced rate capability (10x higher accessible capacity at a 2C rate), and improved capacity retention during extended cycling (99.4% after 500 cycles). These enhancements are attributed to reduced cell polarization and interfacial impedance in coated samples. Post-mortem electron microscopy and XRD analysis confirm that the coating remains intact, inhibiting oxygen release from the CAM structure and the formation of inactive phases (spinel and rock-salt), thereby preventing CAM particle cracking. These findings pave the way for stable and high-performance SSBs with high-voltage cathodes.Keywords: Solid-state batteries, composite cathodes, Nb-based coating, atomic layer deposition (ALD), high voltage stability.Reference: Xiao et al. Understanding interface stability in solid-state batteries. Nat. Rev. Mater. 5 (2020) 105.Wang et al. Single crystal cathodes enabling high-performance all-solid-state lithium-ion batteries. Energy Storage Mater. 30 (2020) 98.Koshtyal et al. Applications and Advantages of Atomic Layer Deposition for Lithium-Ion Batteries Cathodes: Review. Batteries 8 (2022) 184.Cheng et al. Materials Design Principles of Amorphous Cathode Coatings for Lithium-Ion Battery Applications. J. Mater. Chem. A 10 (2022) 22245.

MgSiO3 doped, carbon-coated SiOx anode with enhanced initial coulombic efficiency for lithium-ion battery

Silicon suboxide (SiOx) is considered as a potential negative material for next-generation lithium-ion battery (LIB). However, the relative low initial coulombic efficiency (ICE) hindered the development of SiOx. Herein, we report a two-step magnesiothermic reduction method to synthesize carbon-coated MgSiO3 doped SiOx particles (MgSiO3–SiOx@C), endowing it with superb properties as the anode of LIB. Comprehensive characterization demonstrates the as-prepared MgSiO3–SiOx@C can increase the ICE and releasing volume expansion. As such, the MgSiO3–SiOx@C nano-architectures exhibit a high ICE of 85.4 %, meanwhile, it also shows relatively stable cycling performance of 759.2 mAh g−1 after 100 cycles at 0.5C with the capacity retention of 59.8 %. The lithium ion full battery with LiNi0.8Mn0.1Co0.1O2 as positive electrode proves the feasibility of its practical application, which delivers a stable reversible capacity of 89.2 mAh g−1 after 150 cycles at 1C with a capacity retention of 62.7 %.

Si anodes via dual strategies of coating Si with a rigid polymer and employing a polymer binder with improved mechanical properties

Si undergoes significant volume change over cycles which degrades the structural integrity and stability of the electrode. This volume change is the primary barrier to the commercialization of Si anodes, and it is more pronounced for Si particle sizes over 150 nm. In this study, a crosslinked polymer binder is developed using poly(acrylic acid-co-acrylamide) (PAAM) with enhanced elasticity compared to the widely used poly(acrylic acid). PAAM is further grafted with boronic acid and dopamine, yielding PAAM-B-D, a binder with improved adhesion due to its 3D crosslinked network. Additionally, 350-nm Si is coated with cyclized polyacrylonitrile (cPAN) and heat-treated to form a conjugated structure. The cPAN-coated Si (cSi) exhibits enhanced conductivity and mechanical stiffness and is used as an active material. The developed Si anode effectively combines cPAN-coated Si with the crosslinked network formed in the PAAM-B-D polymer for enhanced adhesion. The cSi@PAAM-B-D electrode sufficiently maintains its structural integrity and mitigates the Si volume change even with the large-sized 350-nm Si. The cSi@PAAM-B-D exhibits a high initial Coulombic efficiency of 86.5 %, at a Si mass loading of 2 mg cm−2. It also shows a capacity retention of 83.6 % and a high areal capacity of 3 mAh cm−2 after 50 cycles.

Electrolyte Reconfiguration by Cation/Anion Cross‐coordination for Highly Reversible and Facile Sodium Storage

AbstractHard carbon (HC) materials are promising anodes for sodium‐ion batteries (SIBs) owing to low cost, high specific capacity and low working potential. However, the poor compatibility of the electrolyte with HC leads to low initial coulombic efficiency (ICE) and sluggish Na+ transport kinetics. Here, we propose an electrolyte reconfiguration strategy based on the hard and soft acid and base (HSAB) theory by introducing methyltriphenylphosphonium bromide (MTPPB). MTPPB can realize a spontaneous cross‐coordination solvation structure with NaPF6 by selective affinity, synchronously optimizing the interfacial chemistry and sodium storage process. The advantages of the chemical π–π bridging of MTPP+‐HC and interaction of MTPP+‐PF6− contribute to preferential and oriented reduction of PF6−, forming a low‐resistance supramolecular SEI. Additionally, Na+‐Br− coordination weakens the Na+‐solvent interactions, facilitating Na+ de‐solvation kinetics. Consequently, the HC||Na cell achieves a superior ICE of 96.6 %, desirable rate capability under 25 °C and invisible capacity decay after 500 cycles at 1 C under −20 °C. The Na4Fe3(PO4)2P2O7||HC pouch battery displays a high ICE of 90.3 % and a 15 % increment of energy density under 25 °C. This work provides a guidance through electrolyte reconfiguration engineering for designing practical HC‐based SIBs with high energy/power density and long‐life span in the extended operating‐temperature range.