Next-generation Lithium-ion Batteries Research Articles

Constructing a Stable Integrated Silicon Electrode with Efficient Lithium Storage Performance through Multidimensional Structural Design.

Silicon (Si) stands out as a highly promising anode material for next-generation lithium-ion batteries. However, its low intrinsic conductivity and the severe volume changes during the lithiation/delithiation process adversely affect cycling stability and hinder commercial viability. Rational design of electrode architecture to enhance charge transfer and optimize stress distribution of Si is a transformative way to enhance cycling stability, which still remains a great challenge. In this work, we fabricated a stable integrated Si electrode by combining two-dimensional graphene sheets (G), one-dimensional Si nanowires (SiNW), and carbon nanotubes (CNT) through the cyclization process of polyacrylonitrile (PAN). The integrated electrode features a G/SiNW framework enveloped by a conformal coating consisting of cyclized PAN (cPAN) and CNT. This configuration establishes interconnected electron and lithium-ion transport channels, coupled with a rigid-flexible encapsulated coating, ensuring both high conductivity and resistance against the substantial volume changes in the electrode. The unique multidimensional structural design enhances the rate performance, cyclability, and structural stability of the integrated electrode, yielding a gravimetric capacity (based on the total mass of the electrode) of 650 mAh g-1 after 1000 cycles at 3.0 A g-1. When paired with a commercial LiNi0.5Co0.2Mn0.3O2 cathode, the resulting full cell retains 84.8% of its capacity after 160 cycles at 2.0 C and achieves an impressive energy density of 435 Wh kg-1 at 0.5 C, indicating significant potential for practical applications. This study offers valuable insights into comprehensive electrode structure design at the electrode level for Si-based materials.

Bubble Wrap-like Carbon-Coated Rattle-Type silica@silicon Nanoparticles as Hybrid Anode Materials for Lithium-Ion Batteries via Surface-Protected Etching

Severe volumetric expansion (~400%) limits practical application of silicon nanoparticles as anode materials for next-generation lithium-ion batteries (LIBs). Here, we describe the fabrication and characterization of a conformal polydopamine carbon shell encapsulating rattle-type silica@silicon nanoparticles (PDA–PEI@PVP–SiO2@Si) with a tunable void structure using a dual template strategy with TEOS and (3-aminopropyl)triethoxysilane (APTES) pretreated with polyvinylpyrrolidone (PVP K30) as SiO2 sacrificial template via a modified Stöber process. Polyethylene imine (PEI) crosslinking facilitated the construction of an interconnected three-dimensional bubble wrap-like carbon matrix structure through hydrothermal treatment, pyrolysis, and subsequent surface-protected etching. The composite anode material delivered satisfactory capacities of 539 mAh g−1 after 100 cycles at 0.1 A g−1, 512.76 mAh g−1 after 200 cycles at 1 A g−1, and 453 mAh g−1 rate performance at 5 A g−1, respectively. The electrochemical performance of PDA–PEI@PVP–SiO2@Si was attributed to the rattle-type structure providing void space for Si volume expansion, PVP K30-pretreated APTES/TEOS SiO2 seeds via catalyst-free, hydrothermal-assisted Stöber protecting Si/C spheres upon etching, carbon coating strategy increasing Si conductivity while stabilizing the solid electrolyte interface (SEI), and PEI carbon crosslinks providing continuous conductive pathways across the electrode structure. The present work describes a promising strategy to synthesize tunable yolk shell C@void@Si composite anode materials for high power/energy-density LIBs applications.

Facile in situ selenization synthesis of chemically bonded SnSe/r-GO composite with superior lithium storage performance

SnSe is regarded as one of the promising anodes for the next-generation lithium ion batteries (LIBs) due to high theoretical capacity and good conductivity. Herein, SnSe/r-GO composite is synthesized by in-situ selenization transformation from SnO2/r-GO and it displays the structure that SnSe nanorods are dispersed on the surface of r-GO homogeneously via the Sn–O–C and Sn–C bonds. The chemically bonded SnSe/r-GO demonstrates much better cycling and rate performance than SnO2/r-GO when used as LIBs anode. It can afford a high discharge capacity of 1196.4 mAh·g−1 in the first cycle and maintained at 606.6 mAh·g−1 after 100 cycles. Even at high current density of 1000 mA·g−1, the specific capacity of SnSe/r-GO can reach to 423.8 mAh·g−1. This work provides an in situ synthesis strategy for high-performance tin-based material in the application of energy storage.

Interface Engineering Enables Wide-Temperature Li-Ion Storage in Commercial Silicon-Based Anodes.

Silicon-based materials have been considered potential anode materials for next-generation lithium-ion batteries based on their high theoretical capacity and low working voltage. However, side reactions at the Si/electrolyte interface bring annoying issues like low Coulombic efficiency, sluggish ionic transport, and inferior temperature compatibility. In this work, the surface Al2 O3 coating layer is proposed as an artificial solid electrolyte interphase (SEI), which can serve as a physical barrier against the invasion of byproducts like HF(Hydrogen Fluoride) from the decomposition of electrolyte, and acts as a fast Li-ion transport pathway. Besides, the intrinsically high mechanical strength can effectively inhibit the volume expansion of the silicon particles, thus promoting the cyclability. The as-assembled battery cell with the Al2 O3 -coated Si-C anode exhibits a high initial Coulombic efficiency of 80% at RT and a capacity retention ratio up to ≈81.9% after 100 cycles, which is much higher than that of the pristine Si-C anode (≈74.8%). Besides, the expansion rate can also be decreased from 103% to 50%. Moreover, the Al2 O3 -coated Si-C anode also extends the working temperature from room temperature to 0 °C-60 °C. Overall, this work provides an efficient strategy for regulating the interface reactions of Si-based anode and pushes forward the practical applications at real conditions.

Mo Doping to Modify Lattice and Morphology of the LiNi0.9Co0.05Mn0.05O2 Cathode toward High-Efficient Lithium-Ion Storage.

The Ni-rich Co-poor layered cathode (LiNixCoyMn1-x-yO2, x ≥ 0.9) is a candidate for the next-generation lithium-ion batteries due to its high specific capacity and low cost. However, the inherent structural instability and slow kinetics of Li+ migration hinder their large-scale application. Mo doping is proposed to enhance the crystal structure stability of LiNi0.9Co0.05Mn0.05O2 and to ensure the preservation of the spherical secondary particles after the cycle. The characterization results indicate that Mo doping not only significantly relieves the lattice strain accompanied by H2 → H3 phase transition but also alleviates particle stress accumulation to avoid pulverization. The Mo-modification allows the generation of uniform fine primary particulates and further agglomeration into the smooth secondary particles to inhibit electrolyte penetration. Hence, the Mo-modified sample NCM90-1%Mo displays an excellent capacity retention of 85.9% after 200 cycles at 0.5 C current density, which is 23.8% higher than that of the pristine NCM90. In addition, with the expansion of the Li slab to accelerate Li+ diffusion and the fine primary particles to shorten the Li+ pathway, the NCM90-1%Mo sample exhibits a high discharge capacity of 150 mAh g-1 at 5 C current density. This work provides a new thought for the design and construction of high-capacity cathode materials for the next-generation lithium-ion batteries.

Effect of Sr and Ta co-substitution on microstructure and ionic conductivity of cubic-Li0.5La0.5TiO3 electrolyte for applications in Li batteries

All-solid-state lithium batteries (ASSBs) have gained significant attention in recent years because of their potential to offer higher energy density and enhanced safety compared to conventional liquid-electrolyte-based lithium-ion batteries (LIBs). Lithium lanthanum titanate (LLTO) is a promising solid electrolyte for next-generation lithium batteries owing to its high ionic conductivity of approximately 10−3 S·cm−1 at room temperature (RT). The Sr and Ta co-doped Li0.5-□La0.5−xSrxTi1−xTaxO3 perovskites were synthesized by solid-state reaction. In this study, Sr2+ and Ta5+ with larger ionic radii, were used for co-substitution in the La3+ and Ti4+ sites, respectively, to increase the bottleneck size of the A-site and expand the average bond length of the B-site on the perovskite structure (ABO3), thereby increasing the Li+ ion mobility. The LLSrxTTaxO3 (0 ≤ x ≤ 0.12) pellets have high relative densities, and high grain conductivities, where the total conductivity of LLSr0.09TTa0.09O3 reached 4.12 × 10−5 S·cm−1. Compared with the pure specimen, the total conductivities of the doped specimens are approximately more than 2.7 times at RT. The assembled semi-solid LFP/10 wt% LLSr0.09TTa0.09O3/Li full battery has a 0.1 C specific discharge capacity of 156 mAh⋅g−1 and a 1 C capacity retention rate of 86% after 290 cycles at RT.

In Situ Transmission Electron Microscopy Observation of Electrochemical Process Between Li–C Nanocomposites and Multilayer Graphene

AbstractPortable power supplies, particularly lithium‐ion batteries (LIBs), will play a key role in achieving sustainable development goals, and electrode active materials for the next generation of LIBs with higher energy density and longer life time is highly demanded. For this, in situ visualization of Li behavior during the charge/discharge process is essential, and transmission electron microscopy (TEM) will be promising for this purpose. Here, a quite simple experimental setup consisting of a newly developed Li–C nanocomposite film sputter‐deposited onto Au nanoprotrusions at room temperature and graphene synthesized on a W probe at 500 °C for the in situ TEM observation of the battery reaction is proposed. The preservation of the metallic Li in the Li–C film that is transferred to TEM without using any transfer vessels under atmospheric conditions is confirmed by high resolution TEM before the in situ electrochemical process in TEM. After the one cycle of the in situ electrochemical process, the intercalation of Li ions into graphene (lithiation) is clearly observed. Thus, it is concluded that the metallic Li stored in the Li–C film works well as the anode active material in the electrochemical process for solid state LIBs, implying the developed in situ experimental system is promising.

Three-dimensional dual-layered conductive binder enables stable and high performance of SiOx/C anodes

Among practical anode materials for next-generation lithium-ion batteries (LIBs), SiOx has garnered substantial attention owing to its relatively low volumetric variation and high theoretical capacity. Nevertheless, the volumetric change of micro-SiOx remains a formidable challenge for existing adhesives. Here, we propose an innovative design strategy that amalgamates both rigidity and flexibility, in which rigid anion gum Arabic (GA), flexible acrylic random copolymer (ARC), and carbon nanotubes (CNTs) interwoven into a 3D network with strong interfacial adhesion and excellent mechanical properties. These attributes effectively restrict SiOx particles and favor a stable solid electrolyte interphase (SEI) layer formed on SiOx. Here, GA plays a pivotal role in dispersing CNTs and maintaining their consistent proximity to SiOx, thereby establishing stable electron conduction networks. The SiOx electrode still sustains a specific capacity of 760 mAh g−1 after 350 cycles under a high current of 1C. Additionally, at 0.2C, the SiOx electrode attains a notably high capacity of 1105 mAh g−1 with a capacity retention of 72.9 % at the 300th cycle, while exhibiting an excellent areal capacity of 1.4 mAh cm−2 even after 400 cycles. This work develops a straightforward yet highly efficacious approach for fabricating high areal capacity electrodes and offers promising prospects for improving the stableness of Si-based anodes.

Lithium intercalation in two-dimensional penta-NiN2: insights from NiN2/NiN2 homostructure and G/NiN2 heterostructure.

High-energy-density lithium-ion batteries (LIBs) are essential to meet the requirements of emerging technologies for advanced power storage and enhanced device performance. The next generation of LIBs will require high-capacity anode materials that move beyond the lithium intercalation chemistry of conventional graphite electrodes. The use of two-dimensional (2D) bilayer structures offers immediate advantages in the development of LIBs. Herein, motivated by the recently synthesized 2D Cairo pentagon nickel diazenide (NiN2) material, we conduct a scrutiny of the intercalation process of lithium atoms in the interlayer gap of NiN2/NiN2 homostructure. Based on density functional theory (DFT), we demonstrate that the diffusion energy barrier of lithium move across the NiN2/NiN2 anode is relatively low, ranging from 0.058 to 0.52 eV, and the corresponding reversible capacity reaches a remarkable value of 499.0927 mA h g-1 per formula unit, surpassing that of graphite (372 mA h g-1). Furthermore, we investigate a 2D van der Waals (vdW) heterostructure composed of pre-strained structures of graphene and NiN2 for use as an anode material in LIBs. It is found that the introduction of graphene leads to improvements in both electrochemical activity and deformation characteristics. The presented results provide theoretical support for the potential of bilayer structures combining NiN2, suggesting them as promising candidates for the development of high-performance anode materials.

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.

The role of oxygen in automotive grade lithium-ion battery cathodes: an atomistic survey of ageing.

The rising demand for high-performance lithium-ion batteries, pivotal to electric transportation, hinges on key materials like the Ni-rich layered oxide LiNixCoyAlzO2 (NCA) used in cathodes. The present study investigates the redox mechanisms, with particular focus on the role of oxygen in commercial NCA electrodes, both fresh and aged under various conditions (aged cells have performed >900 cycles until a cathode capacity retention of ∼80%). Our findings reveal that oxygen participates in charge compensation during NCA delithiation, both through changes in transition metal (TM)-O bond hybridization and formation of partially reversible O2, the latter occurs already below 3.8 V vs. Li/Li+. Aged NCA material undergoes more significant changes in TM-O bond hybridization when cycling above 50% SoC, while reversible O2 formation is maintained. Nickel is found to be redox active throughout the entire delithiation and shows a more classical oxidation state change during cycling with smaller changes in the Ni-O hybridization. By contrast, Co redox activity relies on a stronger change in Co-O hybridization, with only smaller Co oxidation state changes. The Ni-O bond displays an almost twice as large change in its bond length on cycling as the Co-O bond. The Ni-O6 octahedra are similar in size to the Co-O6 octahedra in the delithiated state, but are larger in the lithiated state, a size difference that increases with battery ageing. These contrasting redox activities are reflected directly in structural changes. The NCA material exhibits the formation of nanopores upon ageing, and a possible connection to oxygen redox activity is discussed. The difference in interaction of Ni and Co with oxygen provides a key understanding of the mechanism and the electrochemical instability of Ni-rich layered transition metal oxide electrodes. Our research specifically highlights the significance of the role of oxygen in the electrochemical performance of electric-vehicle-grade NCA electrodes, offering important insights for the creation of next-generation long-lived lithium-ion batteries.

Interfacial degradation of silicon anodes in pouch cells

The practical application of silicon (Si) anodes in the next-generation high-energy lithium-ion batteries (LIBs) is largely hindered by their capacity loss due to the aggressive formation of a solid electrolyte interphase (SEI).

Defect engineering of air-stable Li5FeO4 towards an ultra-high capacity cathode prelithiation additive.

Antifluorite-type Li5FeO4 (LFO) belongs to a class of promising prelithiation materials for next-generation high-energy lithium-ion batteries. Unfortunately, the incomplete de-lithiation performance and inferior air stability hinder its application. In this work, ultra-high capacity is achieved by selective doping of Zr into the Fe sites (LFO-Zr) of LFO to form a large number of defects. The underlying defect formation mechanism is comprehensively investigated using density functional theory, revealing that such selective site doping not only enlarges the unit cell volume but also induces Li vacancies into the structure, both of which facilitate lithium-ion migration at a high-rate and promote the redox of oxygen anions. As a result, under 0.05 and 1C rates, the capacity of LFO-Zr reaches 805.7 and 624.5 mA h g-1, which are 69.0 and 262.0 mA h g-1 higher than those of LFO, translating to an increase of 9.4% and 73.3%, respectively. In addition, LFO-Zr exhibits excellent electrochemical performance in a humidity of 20%, with a high capacity of 577.6 mA h g-1 maintained. With the LFO-Zr additive, the full cell delivered 193.6 mA h g-1 for the initial cycle at 0.1C. The defect engineering strategy presented in this work delivers insights to promote ultra-high capacity and high-rate performance of air-stable LFO.

Over-lithiated NCM through Li5FeO4 for high energy silicon-based lithium-ion batteries.

Si/C composite material is a promising anode material for next-generation lithium-ion batteries due to its high capacity. However, it also exhibits significant initial capacity loss in a full cell due to the unstable SEI. To compensate for the loss of Li inventory, a pre-lithiation reagent, Li5FeO4 (LFO), is incorporated into the LiNi0.85Co0.12Mn0.03O2 (NCM85E) cathode for electrochemical evaluation. The results show that with the addition of LFO, the initial discharge capacity of SiC950/NCM85E full cells can increase from 151.0 mA h g-1 to 193.4 mA h g-1 by 28.1% with a high cathode loading up to about 20 mg cm-2. After 200 cycles, the specific capacity also increased by 25.1%.

Enhancing composite electrode performance: insights into interfacial interactions.

Propelled by the widespread adoption of portable electronic devices, electrochemical energy storage systems, particularly lithium-ion batteries (LIBs), have become ubiquitous in modern society. The electrode is the critical battery component, where intricate interactions between the materials govern both the energy output and the overall lifespan of the battery under operational conditions. However, the poor interfacial properties of traditional electrode materials fall short in meeting escalating performance demands. To facilitate the advent of next-generation lithium-ion batteries, attention must be devoted to the interfacial chemistry that dictates and modulates the various dynamic and transport processes across multiple length scales within the composite electrodes. Recent research has concentrated on systematically understanding the properties of distinct electrode components to engineer meticulously tailored electrode formulations. These are geared towards composite electrodes with heightened chemical stability, thermal robustness, enhanced local conductivities, and superior mechanical resilience. This review elucidates the latest advances in understanding the impact of interfacial interactions in achieving high-capacity, high-stability electrodes. Through comprehensive insights into the interfacial interactions between the various electrode components, we can create improved integrated systems that outperform those developed through empirical methods. In light of this, the adoption of a holistic approach to enhance the interactions among electrode materials becomes of paramount importance. This concerted effort ensures the attainment of heightened rate capability, facilitation of lithium-ion transport, and overall system stability throughout the entirety of the cyclic process.

Mixed-Dimensional (1D-2D) Carbon as a Conductive Additive and Enabler for Next Generation Lithium-Ion Batteries

The race to develop the next generation of lithium-ion batteries with higher performance metrics (e.g. energy density, power density, cyclability) has spurred interest in carbon allotropes, such as carbon nanotubes (1D) and graphene (2D). Herein, a new multi-dimensional carbon material, comprised of long and entangled 1D nanotubes that unfurl into a spanning network of 2D sheetlets, is investigated as a conductive additive in lithium-ion battery cathodes. Compared to conventional conductive additives, this so-called 1.5D carbon material improves both electrical and thermal pathways between battery active materials within the electrode.In this presentation, the electrical, thermal, and electrochemical properties of the mixed-dimensional (1.5D) carbon are compared to conventional additives such as carbon black and graphite. Higher active material loadings, less heat generation, and more energy-dense cells can be enabled by the improved electrical conductivity, where three times less carbon black results in one order of magnitude higher electrode conductivity. The thermal conductivity of these cathodes is also enhanced in both the through- and in-plane directions, which is beneficial for battery thermal management. For instance, using a third of the carbon amount results in more than 30% and 240% higher through- and in-plane thermal conductivity values, respectively. The combination of these properties translates to overall improvements in electrochemical performance metrics including rate capability, lower cell impedance, and higher achievable capacities. Compared to cells with conventional carbon black, there is a 20% reduction in ohmic resistance determined by electrochemical impedance spectroscopy. In terms of capacity retention and rate capability, full cells cycled at a 2C charge and 0.5C discharge rate demonstrated 2.5% higher initial capacity than carbon black with a retention of 95% vs 94.4% after 120 cycles.

Material Selection for Fundamental Investigation of High Temperature Processes in Lithium-Ion Cathode Production

Rapid upscaling of current and near-future lithium-ion battery (LIB) technologies is one of the main remaining challenges for road transport electrification. Among cathode materials high-Ni layered lithium transition metal oxides, Li(NixCoyMn1-x-y)O2 (LNMC, x ≥ 0.7), show large potential for application in next-generation LIB’s because of their high energy density, low cost, and superior electrochemical properties 1–3.To optimize current cathode production technologies, and to select the most optimal future technologies, a thorough understanding of the synthesis fundamentals of lithium-ion cathode calcination processes is a prerequisite. In this context, in-situ X-ray diffraction (XRD) and thermogravimetric analysis (TGA) have emerged as powerful tools for investigating the high-temperature reaction mechanism of the synthesis of these materials 4,5. However, most research does not address some challenges that come with studying complex high temperature synthesis reactions at the inherit small scale of these in-situ techniques. One issue, is that detailed information on the materials used for supporting the samples is seldomly mentioned, making it difficult to distinguish possible side reactions from the main reactions occurring during high temperature characterization. In only a limited number of studies on the high temperature interaction between ternary lithium-ion battery cathode materials and common substrate materials, evidence of direct contact-corrosion of refractory materials due to lithium compounds has been observed 6. To obtain meaningful insights from these in-situ techniques on the synthesis mechanism of LIB cathode materials that are transferable to mass production processes, these unwanted side reactions must be avoided as much as possible.The purpose of the current study is to select the optimal support material for high temperature in-situ characterization of LIB calcination processes. Several LNMC blends, containing a Li compound and a NMC precursor, were calcined in different crucible materials under a 100% O2 flow at 900 °C for 10-12 hours. The selected crucibles for this investigation include common oxide refractories: Al2O3, SiO2 (fiber and quartz) and MgO, as well as Au, as a frequently used inert material for lab scale experiments. Chemical composition of the precursor blend and calcined products are compared by inductively coupled plasma optical emission spectroscopy ICP-OES. Additionally, weight increase of each crucible material is tracked over multiple calcination cycles, and the formed corrosion products are characterized with SEM-EDS and XRD. The ICP-OES measurements show that the final Li:TM ratio of the calcined LNMC material is heavily influenced by the used crucible material, indicating that selecting an appropriate support material is crucial to avoid side reactions and thus ensure that small scale in situ characterization methods such as in-situ XRD and TGA provide relevant data. Nitta, N., Wu, F., Lee, J.T. & Yushin, G. Mater. Today 18, 252–264 (2015).Schipper, F. et al. J. Electrochem. Soc. 164, A6220–A6228 (2017).Julien, C.M. & Mauger, A. Energies 13, 6363 (2020).Wang, D. et al. Adv. Mater. 29, 1606715 (2017).Gao, M. et al. Ionics 27, 3729–3737 (2021).Zhai, P. et al. J. Eur. Ceram. Soc. 38, 2145–2151 (2018).

Elucidating the Lithium-Ion Storage Mechanism in Insertion-Available Hard Carbon with Abundant Closed Porosity: Toward a Practical Material for Batteries

Traditionally, standard lithium-ion batteries (LIBs) are composed of a positive electrode made of metal oxides and a negative electrode made of highly crystallized graphite materials. Graphite materials, with a theoretical capacity of 372 mAh g-1, are chosen as the negative electrode because lithium-ion storage in graphite materials involves lithium-ion intercalation/de-intercalation between graphitic interlayers, a characteristic of faradaic reactions. During galvanostatic charge/discharge (GCD), long plateau regions at low voltages (e.g., 0-0.1 V (vs. Li+/Li)) resulting from multi-staged ion intercalation/de-intercalation are achieved. The low voltage of this intercalation/de-intercalation reaction contributes to enhancing the nominal voltage of LIBs, leading to a higher energy density of the battery.On the other hand, sodium-ion batteries (SIBs) have been extensively researched over the past 10 years as alternative to LIBs to compensate for the gradual scarcity of lithium metal resources. Hard carbon (HC) materials, also known as amorphous non-graphitizable carbons, were introduced to be the negative electrode material for SIBs, since most HCs exhibit very similar electrochemical responses in sodium-ion storage as lithium-ion storage in graphite materials.However, when examining the application of HC materials in lithium-ion storage, it becomes apparent that the development has been significantly limited over the past 20 years. Recent research primarily focuses on biomass-derived HCs and heteroatom-doping on these carbons. This type of HC is abundant in heteroatoms (e.g., N, P, and S) inherited from the intrinsic properties of biomass precursors. While high capacities and excellent rate capabilities are claimed for these biomass-derived HCs, the electrochemical responses of lithium-ion storage in these HCs often exhibit capacitive reactions with a completely sloping region on their GCD curves. Consequently, the miscalculation of capacities can be induced by assessing reversible capacities beyond excessively high voltages (> 1.5 V), even reaching 3 V. The appropriate working voltage window for HCs should be lower than 1.5 V to match with the positive electrodes. Thus, if reevaluating these HCs in a normal voltage window, the obtained reversible capacities are relatively small, due to the deficiency of faradaic reactions signified by the plateau region at low voltages on GCD curves. Additionally, very low initial coulombic efficiencies are often obtained for these highly defected and heteroatom-doped HCs, attributed to the vigorous consumption of electrolyte during the SEI layer formation on their defective sites. As a result, in this work, we introduce a straightforward method to fabricate hard carbon microbeads with tunable microporous structures by carbonizing cross-linked phenolic-formaldehyde (PF) resin spheres, produced through microwave-assisted suspension polymerization. The ultimate goal is to transform HC into a practical battery material for the negative electrode in LIBs, which must possess several abilities similar to graphite (i.e., reversible faradaic reactions with an obvious plateau region at low voltages on GCD curves, low surface area to suppress SEI formation, and good cycling stability). Additionally, the lithium-ion storage mechanism in HCs with varying open/closed porosity is carefully elucidated. By probing the porosity of HC with multiple gas (N2, O2, and CO2) adsorptions, a solid correlation between porous properties and electrochemical responses has been successfully established. As displayed in Figure 1, the results indicate that carbon porosity can change with carbonization temperature. With increasing temperatures, open pores are initially transformed into closed pores, and ultimately, non-porous properties are detected. The electrochemical behaviors in these HCs with distinct porosity differ significantly as demonstrated by GCD curves in Figure 2.It has been found that ultra-micro closed pores (<0.7 nm) are capable of providing confined spaces for lithium ions to be inserted/extracted, characterized as faradaic reactions. Therefore, a plateau region at low voltages can be acquired, leading to additional reversible capacities. Unlike some reported methods, such as holding at a constant voltage, charging/discharging at a very small current density, or overcharging to negative voltage regions, these faradaic reactions are easily unlocked at a current density of 50 mA g-1 in a safe voltage window of 0-0.12 V. As a result, the optimized HC delivers a total reversible capacity of 550 mAh g-1 at 50 mA g-1 in the voltage range of 0-1.5 V. The excellent rate capability and cycling stability of optimized HC are also confirmed. Furthermore, by the post-treatment with hydrogen-assisted reduction, the performance is further enhanced, achieving a reversible capacity of 574 mAh g-1 and an initial coulombic efficiency of 75%. These breakthrough outcomes provide valuable insights for the rational design of hard carbon materials. The optimized hard carbon could be a promising candidate for replacing traditional graphite materials in next-generation LIBs. Figure 1

Enhanced Performances for Solid-State Lithium-Ion Batteries with Llzo Thin Electrolyte and Silicon-Nanowires Electrode

In the past decades, due to an always more electrification and the research of a greener environment, Li-ion Batteries (LIB) have taken an important place in worldwide research. Solid-state batteries (SSBs) have the potential to revolutionize the energy storage industry, offering superior safety and energy density in comparison to traditional LIBs[1, 2]. Our research aims to enhance the performance and safety of solid-state batteries at ambient temperature by incorporating electrodes with high specific capacity with a lithium lanthanum zirconate (LLZO) solid electrolyte.The integration of SiNW electrodes into the solid-state battery architecture offers several advantages. SiNWs are known for their large surface area and superior electrical conductivity and offer a strong platform for efficient lithium-ion transport and cell energy density optimization, theoretically almost 10 times the capacity of graphite[3, 4]. Furthermore, LLZO solid electrolytes are a stable and non-flammable alternative to conventional liquid electrolytes[2, 5], significantly improving battery safety.The main objectives of this study are to investigate the combined effects of silicon nanowires (SiNWs) electrodes and LLZO solid electrolyte and to determine the optimal amount of liquid electrolytes to improve cell safety.In this work, an LLZO thin solid electrolyte tape has been manufactured by casting technique. Precise volumes of liquid electrolyte have been added to the LLZO tape to improve surface contact and ion conductivity. Furthermore, the study will provide a view of the relationship between the quantity of liquid electrolytes introduced and their impact on cell stability and safety.Preliminary results show the preparation of a mechanically stable LLZO tape with high ionic conductivity (>10-4 S cm-1) through an easy and up-scalable procedure. Improvements have been reported in the electrochemical performance of SiNW-LLZO solid-state batteries compared to the relative Li-ion liquid cell.In conclusion, here we developed a new thin solid electrolyte tape with high ionic conductivity, used in solid-state LIBs with silicon nanowires as anode material. Moreover, we standardized a procedure to optimize the use of organic liquid electrolytes as an additive, without omitting the volume or using any excess that could lead to safety issues. This optimization process can contribute to the development of solid-state batteries that are not only high-performance but also safe and reliable for various applications, including electric vehicles and portable electronics. References Wu, F., J. Maier, and Y. Yu, Guidelines and trends for next-generation rechargeable lithium and lithium-ion batteries. Chem Soc Rev, 2020. 49(5): p. 1569-1614.Wang, C., et al., Garnet-Type Solid-State Electrolytes: Materials, Interfaces, and Batteries. Chem Rev, 2020. 120(10): p. 4257-4300.Chan, C.K., et al., High-performance lithium battery anodes using silicon nanowires. Nat Nanotechnol, 2008. 3(1): p. 31-5.Kennedy, T., M. Brandon, and K.M. Ryan, Advances in the Application of Silicon and Germanium Nanowires for High-Performance Lithium-Ion Batteries. Adv Mater, 2016. 28(27): p. 5696-704.Xu, L., et al., Garnet Solid Electrolyte for Advanced All ‐Solid ‐State Li Batteries. Advanced Energy Materials, 2020. 11(2).

In-Situ Convertible Amorphous Silicon Nitride (SiNx) Anode: Resolving the Long-Term Cyclic Instability of Silicon

Silicon (Si) has shown its promises as anode material for next-generation high-energy lithium-ion batteries (LIBs) due to its high theoretical capacity1. However, its practical application has been impeded by the severe cyclic instability caused by a large volume change during (de) lithiation. Recently, a new family of silicon-based anode materials called “in-situ convertible-type anode materials” has emerged to resolve the cyclic instability of silicon.2,3 This family includes sub-stoichiometric oxides, nitrides, and carbides of silicon (SiAx, where A = N, C, O). The working principle of these materials follow two mechanisms: (1) irreversible conversion and (2) reversible alloying/dealloying. During initial lithiation, the conversion reaction occurs, forming Si-Li nanodomains inside a stable Li-conductive matrix denoted as LiySixA (A=N, C, O). In the subsequent cycles, the Si-Li nanodomains reversibly alloying/dealloying with Li, while the Li-conductive matrix ensures stable cycling and good rate capability. Such composition mitigates the challenges associated with Si’s large volume change ensuring long-term cyclic stability.In this study, we demonstrate our approach on the development of silicon-rich, sub-stochiometric, amorphous silicon nitride (SiNx) nanoparticles, as an in-situ convertible-type anode material and its long-term cyclic performance for LIBs. In this approach, the SiNx nanoparticles are produced via the decomposition of silane gas in the presence of ammonia using an industrially scalable, free space reactor (FSR), which is developed and customized in our research institute (IFE) (Fig. 1a). Proper proportions of silane and ammonia gases are introduced into the reactor, leading to the nucleation and growth of SiNx nanoparticles. The synthesized SiNx nanoparticles exhibited Si-rich domain and amorphous structure with particle size between 100 nm - 200 nm (Fig. 1b), as confirmed by SEM, TEM and XRD characterizations. The presence of nitrogen in silicon dominated composition is revealed by energy dispersive electron spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR). The scalability and reproducibility of the FSR synthesis method makes it a promising approach for the industrial production of SiNx for advance anode materials for LIBs.The electrochemical performance of the synthesized SiNx anode is evaluated by galvanostatic cycling and electrochemical impedance spectroscopy. The electrochemical performance of the SiNx performed on the electrodes with the active mass loading of 0.987 mg/cm2 and cycled at C/5 rate has preserved its capacity about 852 mAh/g after around 600 cycles. As seen from Fig. 1c, the improved cyclic stability of the SiNx compared with pure silicon indicates that the Li-conductive matrix plays crucial role in stabilizing the anode. The authors emphasize the need for further investigation and collaboration, particularly in advance characterization, to better understand the composition and mechanisms of the Li-conductive matrix in the SiNx anode. Such detailed understanding can significantly benefit the conversion-type anode materials for their widespread use in future LIB technologies.References Zuo, X., Zhu, J., Müller-Buschbaum, P. & Cheng, Y.-J. Silicon based lithium-ion battery anodes: A chronicle perspective review. Nano Energy 31, 113–143 (2017).Ulvestad, A. et al. Stoichiometry-Controlled Reversible Lithiation Capacity in Nanostructured Silicon Nitrides Enabled by in Situ Conversion Reaction. ACS Nano 15, 16777–16787 (2021).Kilian, S. O. et al. Active Buffer Matrix in Nanoparticle-Based Silicon-Rich Silicon Nitride Anodes Enables High Stability and Fast Charging of Lithium-Ion Batteries. Advanced Materials Interfaces 9, 2201389 (2022). Figure 1