Electrode Swelling Research Articles

Weibull Technique for Evaluation of Swelling: Composite Graphite Resin Electrode for Electrochemical Treatment of Gold Mining Wastewaters

This paper evaluated the swelling of graphite resin electrodes developed for utilization in the electrochemical treatment of gold mining wastewater. Graphite-resin electrodes were developed from used dry cells and resin using non-heat treatment processes (segregation). The Microstructure of the electrode was determined using a scanning electron microscope (Carl Zeiss Smart Evo 10) to ascertain the composition of the electrode. The swelling property of the electrodes was measured using the standard method through a combination of gold mining wastewater and chloride salt solutions. Effects of operational factors (particle size, percentage binder and compressive “compacting” pressure) on the swelling of the electrodes were monitored and evaluated statistically (using analysis of variance). Weibull probability distribution (2 and 3 parameters) was applied to the swelling through Microsoft Excel Solver and Moment Likelihood Method to ascertain the usefulness of the electrode in environmental pollution control through computation of reliability. The study revealed that the swelling was in the range of 1.48 % to 2.24 %, particle size (F5,20 =196.48, p = 2.76 x 10-16), percentage binder (F4,12 =181.58, p = 1.27 x 10-10), and compressive pressure (F3,12 = 106.69, p = 6.43 x 10-9) were significant factors that influence swelling of graphite-resin electrode at 95 % confidence level. the values of α and β for 2-parameters Weibull distribution are 63.162 and 15.098, and 1.265 and 10.089 for MSE and MLM methods, respectively. The Table shows that the values of α, β and θ for 3-parameters Weibull distribution are 3.679, 8.097 and 0.168, and 4.350, 7.165 and 0.198 for MSE and MLM methods, respectively. It was concluded that particle size and compacting pressure are significant factors that had an effect on the swelling of graphite resin electrodes for treatment water and wastewater.

High voltage electrolytes for lithium-ion batteries with micro-sized silicon anodes

Micro-sized silicon anodes can significantly increase the energy density of lithium-ion batteries with low cost. However, the large silicon volume changes during cycling cause cracks for both organic-inorganic interphases and silicon particles. The liquid electrolytes further penetrate the cracked silicon particles and reform the interphases, resulting in huge electrode swelling and quick capacity decay. Here we resolve these challenges by designing a high-voltage electrolyte that forms silicon-phobic interphases with weak bonding to lithium-silicon alloys. The designed electrolyte enables micro-sized silicon anodes (5 µm, 4.1 mAh cm−2) to achieve a Coulombic efficiency of 99.8% and capacity of 2175 mAh g−1 for >250 cycles and enable 100 mAh LiNi0.8Co0.15Al0.05O2 pouch full cells to deliver a high capacity of 172 mAh g−1 for 120 cycles with Coulombic efficiency of >99.9%. The high-voltage electrolytes that are capable of forming silicon-phobic interphases pave new ways for the commercialization of lithium-ion batteries using micro-sized silicon anodes.

Lithiation-induced swelling of electrodes

Understanding the correlation between the deformation field and the diffusion of lithium in electrode materials can provide the knowledge of the effects of materials constants on the deformation behavior of lithiated electrode materials. In this work, we study the lithiation-induced swelling and deformation of three different electrodes of plate-like, cylindrical-shell and spherical-shell shapes under the framework of linear elasticity. Linear relationships between the lithium concentration and hydrostatic stress are derived for all the three different electrodes. For the diffusion of lithium with negligible contribution of stress-limited diffusion to the diffusion of lithium in electrode materials, the lithium-induced swelling is proportional to the partial molal volume of lithium and the state of charge for the three different electrodes of plate-like, cylindrical- and spherical shapes. The increase rate of the normalized surface displacement (the swelling) is the largest at the onset of lithiation and decreases gradually to a plateau with the increase of the lithiation time. Both the constraint and geometrical shape of an electrode play important roles in controlling the swelling and stress evolution in the electrode.

Silicon-Containing Anodes for High-Energy Density Lithium-Ion Batteries

Next- Generation Lithium(Li)-based rechargeable battery technologies utilising silicon (Si) and Si-containing (Si/Gr, SiOx/Gr, SiNx etc.) anodes coupled with high-capacity/high-voltage insertion-type cathodes (IC) have gained significant attention from both academic and industrial sectors.1 This originates from their practically achievable high energy density, offering a new possibility towards the large-scale espousal of electric vehicles and effective integration of renewable energy sources. In pursuit of designing such high-energy-density electrical energy storage devices, the anode compartment plays huge role and has accordingly reaped increasing interest. In this regards, Si and Si-containing materials are considered to be the most promising choices to replace state-of-the-art graphite in the construction of Lithium-ion batteries (LIBs). This is attributed to their unparalleled high theoretical capacity, suitable operating voltage, natural abundance, environmental benignity, nontoxicity, high safety, and so forth.However, Si and Si-containing materials are endowed with their own advantages and inherent shortcomings. Colossal volume change, much lower diffusivity (σe-+ and DLi+), unstable and fragile solid electrolyte interphase (SEI) formation, electrode swelling, and electrolyte drying are among the most impending intrinsic challenges that hider the large-scale commercialization of such innovative materials. Moreover, the detailed storage mechanism, electrochemistry, failure mechanism and impact of each component in case of blended/composite anode materials (e.g., Si/Gr and SiOX/Gr) etc. remain to be key loopholes to fully understand and thus enable the systems.In this paper, accounts on the various Si-containing active materials (Si, SiOx, Si/Gr blend/composite, SiOx/Gr blend/composite, SiNx etc) including their pros and cons, recent progresses, detailed storage chemistries and mechanisms, characteristics, possible tailored remedies to evade their challenges and thus improving performances - in hope of facilitating their large-scale deployment in the market, and future prospects and research directions will be presented. Impact of atomic level peculiar properties on the material and battery cells level key performance matrices are thoroughly examined. Moreover, the specific energy (Eg) and energy (Ev) density of various insertion-type cathode materials as a function of a) the weight fraction of Si at a fixed areal capacity, b) areal capacity at various Si contents, c) various kinds of electrolytes (liquid, polymer, glass and ceramic) at a fixed areal capacity, and d) electrolyte thickness are evaluated and analyzed.The approach presented in this paper will spur new concepts and perspectives into the best use of Silicon (Si) and Si-containing anode materials for the development Next-Generation high-energy density LIBs. 1Eshetu, G. G.; Zhang, H.; Judez, X.; Adenusi, H.; Armand, M.; Passerini, S.; Figgemeier, E, “Gebrekidan Gebresilassie Eshetu, Heng Zhang, Xabier Judez, Henry Adenusi, Michel Armand, Stefano Passerini, & Egbert Figgemeier, “Production of high-energy Li-ion batteries comprising silicon-containing anodes and insertion-type cathodes.” Nat. Commun. 2021, 12 (1), 1–14.

Chemical Structure Comparison via Scanning Electron Microscopy of Spent Commercial Nickel-Metal Hydride Batteries.

Back-scattered electron imaging and X-ray elemental mapping were combined in a tabletop scanning electron microscope (SEM) to investigate cross-sections of three AA-type (mignon) nickel-metal hydride (NiMH) batteries from different manufacturers. All batteries underwent 500-800 charge/discharge cycles and reached their end of lifetime after several years as they could no longer hold any significant electric charge (less than 20% of nominal charge capacity), but none showed any short-circuiting. The types of degradation observed in this field study included electrode swelling, metallic nickel formation and carbon incorporation into pores in the positive electrodes and, in the negative electrodes, metal alloy segregation of different elements such as nickel, lanthanum and, in one case, sodium, as well as grain break-up and pore formation. All these phenomena could readily be observed at rather small magnifications. This will be important for the improvement of NiMH batteries, for which new generations with nominally slightly increased charge capacities are being marketed all the time.

Layer stacked SiOx microparticle with disconnected interstices enables stable interphase and particle integrity for lithium-ion batteries

Severe mechanical fracture and unstable interphase, associated with the large volumetric expansion/contraction, significantly hinder the application of high-capacity SiOx materials in lithium-ion batteries. Herein, we report the design and facile synthesis of a layer stacked SiOx microparticle (LS-SiOx) material, which presents a stacking structure of SiOx layers with abundant disconnected interstices. This LS-SiOx microparticle can effectively accommodate the volume expansion, while ensuring negligible particle expansion. More importantly, the interstices within SiOx microparticle are disconnected from each other, which efficiently prevent the electrolyte from infiltration into the interior, achieving stable electrode/electrolyte interface. Accordingly, the LS-SiOx material without any coating delivers ultrahigh average Coulombic efficiency, outstanding cycling stability, and full-cell applicability. Only 6 cycles can attain >99.92% Coulombic efficiency and the capacity retention at 0.05 A g−1 for 100 cycles exceeds 99%. After 800 cycles at 1 A g−1, the thickness swelling of LS-SiOx electrode is as low as 0.87%. Moreover, the full cell with pure LS-SiOx anode exhibits capacity retention of 91.2% after 300 cycles at 0.2 C. This work provides a novel concept and effective approach to rationally design silicon-based and other electrode materials with huge volume variation for electrochemical energy storage applications.

First-Principles Investigation on Multi-Sodium Sulfide and Sodium Sulfide Clusters in Sodium-Sulfide Batteries

Room temperature sodium-sulfur batteries are expected to be widely used in large energy storage and power batteries due to their high energy density, abundant resources, and low price. However, shuttle effect of polysulfide, low reactivity of the end product, low activity of sodium sulfide, and electrode swelling are the main challenges. In order to improve the low sodium sulfide reaction performance and electrode swelling, the volume swelling of the final product sodium sulfide can be well controlled by using sodium sulfide directly as the cathode, and a special cathode structure was developed to overcome the “inert” problem of Na2S. Nevertheless, the structure, relative stability and electronic properties of (Na2S)n clusters are still uncertain so far, which is a necessary prerequisite for optimizing their properties and understanding their partitioning processes. In this paper, theoretical calculations of (Na2S)n clusters were performed to investigate the catalytic decomposition of sodium sulfide by mono-atomic catalysts, giving the energy distribution of sodium ions diffusing over FeN4 and FeN2. Together, these calculations confirm the high coordination design of mono-atomic Fe–N–C catalysts with high sulfur affinity and catalytic activity. Our work is an important step toward understanding (Na2S)n clusters and improving the performance of Na–S cells.

Asymmetric Swelling Behaviors of High-Energy-Density Lithium-Ion Batteries with a SiOx /Graphite Composite Anode.

The battery swelling originated from the electrode swelling is a big obstacle for the practical application of high-energy-density lithium-ion batteries (HED-LIBs). Herein, the HED-LIBs are constructed by SiOx /graphite composite anode and LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) cathode and their swelling behaviors are investigated at the cell, electrode, and particle scales. there are three expansion stages during the charging while one expansion followed by two contraction stages during the discharging process. The expansion ratio is in direct proportion to the ratio of SiOx content and about 10 times larger than that of the cathode. A 100nm thick double-layer solid electrolyte interface, comprises LiF, Li2 O, and Li2 CO3 , forms on the surface of the SiOx particles, and evolves into a 300nm thick triple-layer after cycling. The performance degradation of HED-LIBs is associated with the expansion of anodes, increase in resistance, and consumption of Li in the anodes during cycling. This study is expected to guide the future selection and design of HED-LIBs and battery packs.

Limiting anode utilization: A strategy to increase Si content and useable capacity in Si/C composite anode without compromising cycle life

Despite having a high theoretical capacity, silicon-based anodes fall short in providing practical and cycle-stable specific capacity close to the theoretical potential. The main challenge, namely particle pulverization and loss of mechanical integrity due to a large volume expansion, is commonly addressed by nano-structuring and blending with graphite in a Si/C composite anode. However, a maximum Si content of 15% in Si/C composite anodes has been realized, leaving scope for much improvement. Herein we discuss and theoretically benchmark a new strategy to increase Si content and achievable specific capacity by limiting anode utilization to minimize degradation. Through careful consideration to differential rates of lithiation of Si and C, particle fracture, and electrode swelling limit, our physical analysis suggests that this strategy could provide specific capacities of greater than 1100 Ah/Kg while eliminating degradation. These benchmarks are arrived at though a comprehensive analysis of lithiation of Si and C on an individual component level and the associated propensity for Si particle fracture as well as reduction in electrode porosity due to volume expansion and arriving at safe lithiation limits for a given set of electrode parameters under consideration. Since this safe range of operation is dependent on particle size, we show that we can optimize the Si% in Si/C to achieve maximum utilizable specific capacity for a given particle size.

On-site conversion reaction enables ion-conducting surface on red phosphorus/carbon anode for durable and fast sodium-ion batteries

The practical applications of high-capacity alloy-type anode materials in sodium-ion batteries (SIBs) are challenged by their vast volume effects and resulting unstable electrode–electrolyte interphases during discharge–charge cycling. Taking red phosphorus (P)/carbon anode material as an example, we report an on-site conversion reaction to intentionally eliminate the volume effect-dominated surface P and yield an ionically conducting layer of Na3PS4 solid-state electrolyte on the composite. Such a surface reconstruction can significantly suppress the electrode swelling and simultaneously enable the activation energy of interfacial Na+ transfer as low as 36.7 kJ mol−1, resulting in excellent electrode stability and ultrafast reaction kinetics. Consequently, excellent cycling performance (510 mA h g−1 at 5 A g−1 after 1000 cycles with a tiny capacity fading rate of 0.016% per cycle) and outstanding rate capability (484 mA h g−1 at 10 A g−1) are achieved in half cells. When coupled with Na3V2(PO4)3 cathode, the full cells exhibit 100% capacity retention over 200 cycles at 5C with an average Coulombic efficiency of 99.93% and a high energy density of 125.5 W h kg−1 at a power density of 8215.6 W kg−1 (charge or discharge within ∼49 s). Remarkably, the full cell can steadily operate at a high areal capacity of 1.9 mA h cm−2, the highest level among red P-based full SIBs ever reported.

High-density crack-resistant Si-C microparticles for lithium ion batteries

Hollow-structured silicon-carbon composite particles are regarded as advanced anode materials for lithium-ion battery (LIBs) due to their superior expansion-buffering capability. However, the hollow structures compromise particle density and its benefits are diminished by the potential pore collapses due to electrode calendaring and cell operation. Herein, we report stuffed high-density Si-C particles that can suffice to be crack-resistant and deliver highly reversible Li-storage performances. This was achieved by implanting Si particles into a dual-layered carbon matrix comprised of a porous interior and a compact exterior. The compact exterior prevents electrolyte permeation, while the porous interior accommodates the Si expansion. Such structure allows an intraparticle “on-site voiding” mechanism, leading to anti-cracking and low swelling of Si-C electrode. The resulting Si-C particles possess high tap density (0.86 g/cc), low specific surface area (3.3 m2/g), and the Si-C/graphite mixture anode delivers capacity retention of 96.2% after 200 cycles. Paired with high-mass-loading LiFePO4, the full cells display 70.6% capacity retention over 200 cycles under industry-viable electrode metrics (1.20 g/cm3 for SiCG-600 and 2.40 g/cm3 for LFP, 1.88 mAh/cm2). This gives rise to 18.3% energy density improvement as compared to graphite || LiFePO4 battery. Herein, this study shed light on designing dense particles for practical high-energy LIBs.

Investigation of Silicon-Based Anodes for Li-Ion Batteries Using X-Rays and Neutron 3D/4D Imaging Techniques

Silicon-based anode materials are one of the most promising approaches to further increase the energy density of lithium-ion batteries. However, current materials are limited by poor cycling stability and rapid capacity fading, mainly caused by the massive volume expansion of Si during lithiation and subsequent strain on the material composite. [1] Furthermore, this electrode swelling also results in continuous solid electrolyte interface (SEI) growth, which hinders the migration of Lithium and leads to permanent capacity loss. [2] [3]To optimize these materials, analytical techniques able to probe the local 3D morphology and Li content are necessary. By applying methods such as neutron computed tomography (NCT), X-Ray computed tomography (XCT) and synchrotron scattering micro-tomography (SMT) structural ageing and changes in the distribution of lithium in the various components can be characterized and quantified for different charging states and recharge cycle numbers.This study investigates an anode material based on a dual phase alloy system of amorphous Silicon (a-Si) with crystalline iron silicide (c-FeSi2) and graphite. [4] [5] Li-ion battery coin cells containing this silicon-graphite composite anode material were industrially produced and aged by performing 1, 300, and 700 charge-discharge cycles, corresponding to remaining capacities of 100, 70 and 50 %, respectively. NCT and XCT scans were acquired at the NeXT instrument of the ILL in Grenoble (France) [6], and SMT measurements performed at ID31 of the neighboring ESRF. These datasets were reconstructed and evaluated using specially developed data processing pipelines. By performing multi-modal registration, the NCT and XCT scans were aligned and segmented to combine the complementary datasets and create a 4D model of the Li-ion battery coin cells.Figure 1 shows a sample of the combined NCT (cyan) and XCT datasets (red). Cropped horizontal slices of Li-Ion battery coin cells are depicted side by side with the main components labelled. Comparing one of the highly cycled cells with 50% remaining capacity (top) with the reference cell without electrolyte (bottom), trapped Lithium can be observed in the anode layers, visible as cyan colored blotchy areas in the otherwise dark component. The pixel size is approximately 5 µm.The change of lithium distribution in the components between different cycle numbers and charge states in the attenuation-based tomography techniques of NCT / XCT is quantified by modelling expected attenuation parameters to the observed values. The diffraction-based tomography method of SMT was modeled using expected lattice parameters. From this information, trapped Lithium can be identified and changes in the distribution are analyzed to point out possible degradation and failure mechanisms.We acknowledge financial support from the European Union’s Horizon 2020 research and Innovation program No. 875514 (ECO2LIB) as well as No. 847439 (InnovaXN) under the Marie Skłodowska-Curie grant agreement.[1] S. Tardif et al, https://doi.org/10.1021/acsnano.7b05796 [2] T. Vorauer et al, https://doi.org/10.1038/s42004-020-00386-x [3] P. Kumar et al, https://doi.org/10.1002/smll.201906812 [4] C. Berhaut et al, https://doi.org/10.1021/acsnano.9b05055 [5] C. Berhaut et al, https://doi.org/10.1016/j.ensm.2020.04.008 [6] A. Tengattini et al, https://doi.org/10.1016/j.nima.2020.163939 Figure 1

Self-deformed Si/Graphene@C anode for stress relief in lithium ion batteries

Despite considerable efforts of carbon matrix for the superior structural integrity of Si anode of lithium-ion batteries, Si/C architectures with thick carbon layer suppress its ion kinetics. The design of Si/C architectures with thin carbon layers is promising for superior ion/charge kinetics but still arouses its deterioration in structural stability due to the agglomeration of Si nanoparticles (SiNPs). Herein, SiNPs are dispersed on large-sized graphene (Si/G@C) with robust linkings, which effectively suppresses the self-limiting effect due to the dispersed SiNPs on graphene. Finite element analysis reveals well-dispersed SiNPs in Si/G@C provide enough room for accumulating its volume variations. Even, the accumulated stress in relatively dense regions of SiNPs is relieved via self-deformed graphene. Thin carbon layers are grown on SiNPs of Si/G@C for low ion diffusion barriers, in agreement with density function theory simulation. Meanwhile, an electrical network and high electrical-field response on the interface of Si and carbon layers improve its charge transfer. Therefore, the prepared Si/G@C shows superior rate capability (1127.1 mAh/g at 4 A/g), capacity retention (∼74.56% after 303 cycles at 1A/g) and low electrode swelling (∼3.60% after 303 cycles). This design of Si/G@C sheds light on the preparation of advanced Si-based anode in lithium-ion battery.

Self-adaptive anode design with graphene-coated SiOx/graphite for high-energy Li-ion batteries

Si-based materials are promising high-capacity anodes, which can improve the energy density of Li-ion batteries (LIBs) that are required for the advancement of electric vehicles. Nevertheless, the severe volume change of Si-based materials during repeated cycles limits their widespread applications in LIBs. Here, we report a durable and high-energy blended anode composed of artificial graphite (AG) and graphene (Gr)-coated SiOx (SiOx@Gr) particles. The Gr coating reduces the electrode swelling during repeated cycles and increases the initial Coulombic efficiency of SiOx. This further increases the areal capacity owing to the reduction of carbon black (CB) content to 3 wt%. The SiOx@Gr/AG blended anode exhibits excellent properties compared to the bare SiOx/AG anode. These results can be attributed to the self-adaptive behavior by Gr sheets coated on SiOx particles, which mitigates the mechanical damage on the AG particles and maintains the electron conduction pathways. Hence, the reversibility of the charge–discharge reactions improves, as revealed by Raman spectral mapping and powder flowability measurements. Furthermore, the full-cell with the SiOx@Gr/AG anode exhibits good cycling stability and high volumetric capacities over 300 cycles compared to the full-cell with the bare SiOx/AG anode and AG-only anode, demonstrating the applicability of the high-capacity Si-based anodes for LIBs.

Scalable Synthesis of Pore-Rich Si/C@C Core-Shell-Structured Microspheres for Practical Long-Life Lithium-Ion Battery Anodes.

Silicon/carbon (Si/C) composites have rightfully earned the attention as anode candidates for high-energy-density lithium-ion batteries (LIBs) owing to their advantageous capacity and superior cycling stability, yet their practical application remains a significant challenge. In this study, we report the large-scale synthesis of an intriguing micro/nanostructured pore-rich Si/C microsphere consisting of Si nanoparticles tightly immobilized onto a micron-sized cross-linked C matrix that is coated by a thin C layer (denoted P-Si/C@C) using a low-cost spray-drying approach and a chemical vapor deposition process with inorganic salts as pore-forming agents. The as-obtained P-Si/C@C composite has high porosity that provides sufficient inner voids to alleviate the huge volume expansion of Si. The outer smooth and robust C shells strengthen the stability of the entire structure and the solid-electrolyte interphase. Si nanoparticles embedded in a microsized cross-linked C matrix show excellent electrical conductivity and superior structural stability. By virtue of structural advantages, the as-fabricated P-Si/C@C anode displays a high initial Coulombic efficiency of 89.8%, a high reversible capacity of 1269.6 mAh g-1 at 100 mA g-1, and excellent cycle performance with a capacity of 708.6 mAh g-1 and 87.1% capacity retention after 820 cycles at 1000 mA g-1, outperforming the reported results of Si/C composite anodes. Furthermore, a low electrode swelling of 18.1% at a high areal capacity of 3.8 mAh cm-2 can be obtained. When assembled into a practical 3.2 Ah cylindrical cell, extraordinary long cycling life with a capacity retention of 81.4% even after 1200 cycles at 1C (3.2 A) and excellent rate performance are achieved, indicating significant advantages for long-life power batteries in electric vehicles.

How do Depth of Discharge, C-rate and Calendar Age Affect Capacity Retention, Impedance Growth, the Electrodes, and the Electrolyte in Li-Ion Cells?

Lithium-ion cells testing under different state of charge ranges, C-rates and cycling temperature have different degrees of lithium inventory loss, impedance growth and active mass loss. Here, a large matrix of polycrystalline NMC622/natural graphite Li-ion pouch cells were tested with seven different state of charge ranges (0–25, 0–50, 0–75, 0–100, 75–100, 50–100 and 25%–100%), three different C-rates and at two temperatures. First, capacity fade was compared to a model developed by Deshpande and Bernardi. Second, after 2.5 years of cycling, detailed analysis by dV/dQ analysis, lithium-ion differential thermal analysis, volume expansion by Archimedes’ principle, electrode stack growth, ultrasonic transmissivity and X-ray computed tomography were undertaken. These measurements enabled us to develop a complete picture of cell aging for these cells. This then led to an empirical model for cell capacity loss vs SOC range and calendar age. Although these particular cells exhibited substantial positive electrode active mass loss, this did not play a role in capacity retention because the cells were anode-limited during full discharge under all the tests carried out here. However, the positive electrode mass loss was strongly coupled to positive electrode swelling and electrolyte “unwetting” that would eventually cause dramatic failure.

Advanced Diagnostics for Lithium-ion Batteries: Decoding the Information in Electrode Swelling

Advanced Diagnostics for Lithium-ion Batteries: Decoding the Information in Electrode Swelling

A Scalable Silicon Nanowires-Grown-On-Graphite Composite for High-Energy Lithium Batteries

Silicon (Si) is the most promising anode candidate for the next generation of lithium-ion batteries but difficult to cycle due to its poor electronic conductivity and large volume change during cycling. Nanostructured Si-based materials allow high loading and cycling stability but remain a challenge for process and engineering. We prepare a Si nanowires-grown-on-graphite one-pot composite (Gt-SiNW) via a simple and scalable route. The uniform distribution of SiNW and the graphite flakes alignment prevent electrode pulverization and accommodate volume expansion during cycling, resulting in very low electrode swelling. Our designed nanoarchitecture delivers outstanding electrochemical performance with a capacity retention of 87% after 250 cycles at 2C rate with an industrial electrode density of 1.6 g cm-3. Full cells with NMC-622 cathode display a capacity retention of 70% over 300 cycles. This work provides insights into the fruitful engineering of active composites at the nano- and microscales to design efficient Si-rich anodes.

Synthesis of micro-sized porous antimony via vapor dealloying for high-performance Na-ion battery anode

Antimony (Sb) is a promising sodium-ion anode material due to sustaining a high theoretical capacity of 660 mAh g−1. However, the huge volumetric change of 293% leads to serious pulverization and poor cycling stability. Herein, we design micro-sized porous Sb (PSb) via one-step chemical vapor dealloying. The as-prepared PSb owns three-dimensional nano-skeleton and interconnected pores, which enables PSb a high tap density (2.33 g cm−3), high electrochemical properties and robust ability to alleviate the volumetric expansion of sodiation. The PSb anode exhibits initial charge and discharge capacities of 834 and 517 mAh g−1 at a current density of 50 mA g−1, corresponding to an initial Coulombic efficiency (ICE) of 61.8%. And a high capacity retention of 80% is obtained after 120 cycles at a current density of 50 mA g−1. Moreover, the PSb sustains an outstanding rate performance with a capacity of 300 mAh g−1 even at a large current density of 3000 mA g−1. Compared with micro-Sb, the PSb exhibits a lower electrode swelling of 63.96% because the unique porous structure can effectively alleviate the volume variation and pulverization of Sb during cycling. The enhanced performance of PSb enables it as a promising anode material for advanced Sodium-Ion Batteries.

Optimization of Silicon-Graphite Anode and Polymeric Binders for Lithium-Ion Batteries

Graphite (G) is considered as the state-of-the-art anode material in commercial Li-ion batteries (LIBs), attributed due to its long cycle life, high Coulombic/energy efficiency and low cost. However, its low theoretical specific capacity (372 mAh g-1/ 840 mAh cm−3 for LiC6) is a limiting factor towards the large scale integration of emerging applications such as electromobility (electric vehicles, xEVs). Therefore, it is essential to search for other anode active materials with higher theoretical capacity.1 Silicon (Si) is one of the most appealing anode active materials with an extra-high capacity of 4200 mAh g-1 /9660 mAh cm−3 (Li4.4Si) and 3590 mAh g-1/8360 mAh cm−3 (Li3.75Si) at 415 oC and 25 oC respectively, suitable operating potential (0.2-0.4 V vs. Li/Li+), high abundancy (second abundant element in the earth crust) and thus low cost, superior safety and, environmental friendliness. However, in spite of all the resilient features, Si shows an extreme volume change ( ≥ 280%) upon (de-)lithiation, low electric conductivity, low initial Coulombic efficiency, electrode swelling and, electrolyte drying. These challenges limit the usage of Si in large-scale commercial LIBs. Many strategies have been suggested to overcome the above-mentioned difficulties, and two of the most promising strategies are: (1) use of Si-G composite anode active material, resulting in a synergistic beneficial effect of G and Si. The composite electrode shows longer cycle life and lower volume change with respect to Si anode and higher theoretical capacity compared to G anode. Moreover, G also enhances the electrical conductivity of the blended anode electrode. However, it is crucial to optimize the composition of the Si to G ratio so as to obtain desirable performances. (2) Use of new tailored binders for Si-based anodes. Binders are electrochemically inactive components of LIBs, nevertheless, they play a major role in the mechanical stability of the electrodes, irreversible capacity losses and stabilizing the cycling performance. Suitable binder for Si-based anodes should accommodate the volume change of Si particles. These binders usually contain carboxylate or imide functional groups, which interact strongly with the surface of the Si during charge/discharge of the battery.2 This implies also that the choice of binders for Si may not be necessarily the same as that of G.In this work, we have investigated and optimized the composition of Si-G composite anode using a mixture of state-of-the-art carboxymethyl cellulose (CMC) and poly (acrylic acid) (PAA) binders. Furthermore, the composition of the binders was optimized for the corresponding different ratio of the Si-G blends. Afterward, the benchmarked electrodes were further studied with different designer bio-polymeric binders such as chitosan, tragacanth gum, alginates, etc. The electrochemical properties (long-term cycling, rate capability, cyclic voltammetry,...) for the optimized Si to G ratio electrodes were investigated, followed by surface characterization and thermal reactivity.