C-rate Performance Research Articles

On the Volume Expansion of Lithium Ion Battery Electrodes (I) after Wetting, and (II) Selection of the Right Amount of Electrolyte

The electrolyte is necessary for transport of lithium ions between the negative and positive electrode within the battery cell. The lower the amount of electrolyte, the higher the energy density and specific energy. Hence, it is important to understand which cell parameters are relevant to determine the right amount of electrolyte. Here, three different cell designs in 1 to 5 Ah pouch cells where investigated for cell impedance after filling, cell capacity after formation, C-rate performance, and capacity retention for up to 3,000 full cycles. Wetting the cell with electrolyte, the cell pore volume changed between 25%–35% due to changes of 6%–16% in the thickness of the anode and cathode. Although electrolyte volumes >0.85 times the wet cell pore volume showed minimal resistance before formation, only electrolyte volumes of 1.08 times the wet cell pore volume were sufficient for a successful formation process. For long-term cycling, a minimum electrolyte volume of 1.19 times the wet cell pore volume was required to improve long-term cycling performance. Future experiments will investigate the correlation of capacity fade with electrolyte consumption for different electrolytes.

Co-axially electrospun Li-rich layered Oxide@Spinel core-shell heterostructure nanofibers for enhanced stability and electrochemical performance

Lithium-rich layered oxides (LLO) possessing high specific capacity has the limitation of voltage fade, poor high C-rate performance and low conductivity. Spinel coating on LLO surface is known to mitigate the voltage fade, however, enabling high C-rate performance remains challenging. In this study, LLO nanofiber core with composition 0.6Li2MnO3·0.4LiMn0.25Ni0.38Co0.37O2 is prepared by electrospinning process and the same is coated with spinel LiMn1.5Ni0.5O4 shell to obtain LLO/spinel (LLO/S) core-shell heterostructure. The spinel shell coating is accomplished (i) by a novel co-axial (CA) electrospinning process and (ii) by wet chemical (WC) approach. The CA electrospinning process provides a uniform core-shell structure compared to the WC process. The electron microscopy studies reveal the fibrous microstructure in LLO/S heterostructures with energy dispersive spectroscopy compositional mapping showing the spinel composition on the surface. Higher concentration (>10 wt.%) of spinel coating are shown to break the fibers into particulates. X-ray diffraction and high-resolution transmission electron microscopy analysis confirm the spinel structure formation along with layered structure. While the capacity is slightly compromised compared to the pristine LLO nanofiber, the LLO/S heterostructure with 10 wt.% spinel coating exhibits a high reversible capacity of 268 mAhg-1 with minimal capacity loss during the 1st cycle (with coulombic efficiency 83.5%) and an excellent high C-rate capability (88 mAhg-1 at 10C-rate and 55 mAhg-1 at 20C-rate). The electrochemical studies also demonstrate the importance of optimal spinel content in the coating and the method of spinel coating on the layered material surface. The encapsulation of LLO with spinel layer which has 3D-diffusion pathways for Li-ion transport facilitates high ionic and electronic conductivity and hence leads to enhanced electrochemical performance of LLO/S heterostructured cathodes.

Investigation of Dry-Made NMC 811 Electrodes with Varying Binder and the Conductive Agent Contents

Lithium-ion battery electrode materials consist of active materials (AM), conductive agents, and binders. Although conductive agents and polymeric binders occupy a small portion of the electrode, they play an indispensable role. Conductive agents are needed to improve the electronic conductivity of the electrode, while binders ensure mechanical integrity by providing particle/particle cohesion and electrode-film/substrate adhesion. Optimizing the interactions of active materials, conductive agents, and binders is crucial for achieving the desired electrode performance and durability. Although multiple studies have explored the impact of electrode composition for slurry-based electrodes, it is still unclear how composition affects the electrodes made by dry processes. In this study, we performed a detailed investigation of the effects of the different electrode compositions by changing the ratio of polyvinylidene difluoride (PVDF) binder and carbon black (CB) for dry-made LiNi0.8Mn0.1Co0.1O2 (NMC 811) electrodes. The electrostatic spray deposition method was used as a dry electrode fabrication process due to its many advantages, such as reduced energy consumption and inexpensive processing requirements. We investigated electrodes of four different compositions, 96:3:1, 96:2:2, 90:7.5:2.5, and 90:5:5 (AM:PVDF: CB), corresponding to PVDF/CB mass ratios of 1:1 and 3:1.We found that electrodes with a high PVDF/CB ratio of 3:1 have larger impedance than electrodes with a low PVDF/CB ratio of 1:1 due to the insulating aggregates of PVDF alone, causing deteriorated electrochemical performance. At the PVDF/CB ratio of 1:1, an even distribution of PVDF/CB on the AM particle surfaces and in the pores between the AM particles was observed. For both PVDF/CB ratios of 1:1 and 3:1, increasing the total amount of PVDF and CB (e.g., decreasing the AM amount) in the composite electrode enhanced both the C-rate and cycling performance. However, electrodes with the PVDF/CB ratio of 1:1 at high AM content (96%) still showed a comparable C-rate performance to that with lower AM content (90%). Thus, dry-made electrodes with high AM content can achieve a good high C-rate performance, especially for high-energy-density applications.This study provides a better understanding of the effects of CB/PVDF, which is key to finding an optimal structure and composition of the dry-made electrodes.

Investigating the Effect of Electrode Compositions on Dry-made NMC811 Positive Electrodes

Dry electrode manufacturing processes are appealing as they can potentially mitigate the economic and environmental consequences of traditional slurry techniques. Understanding the interactions among active material (AM), conductive agent, and binder in dry-made electrodes is crucial for achieving the desired electrode performance and durability. In this study, we conducted a comprehensive investigation of the effects of the different electrode formulations by altering the ratio of polyvinylidene fluoride (PVDF) binder and carbon black (CB) for LiNi0.8Mn0.1Co0.1O2 (NMC811) electrodes made using a dry coating process. Specifically, we examined four distinct electrode formulations: 96:3:1, 96:2:2, 90:7.5:2.5, and 90:5:5 (AM: PVDF: CB), equivalent to PVDF/CB mass ratios of 1:1 and 3:1. We found that a high PVDF content at PVDF/CB ratio of 3:1 provides high mechanical strength. However, the electrode ionic conductivity decreases due to the insulating aggregates of PVDF. The PVDF/CB ratio of 1:1 approaches the optimum ratio for balanced electronic and ionic conductivities and electrode mechanical strength, hence leading to enhanced electrochemical performance. For electrodes with the PVDF/CB ratio of 1:1, we observed surprisingly that electrode with higher AM content (e.g., 96%) showed a comparable C-rate and full-cell cycling performance to that with lower AM content (90%).

Inducing and Understanding Pseudocapacitive Behavior in an Electrophoretically Deposited Lithium Iron Phosphate Li-Metal Battery as an Electrochemical Test Platform.

Our study has effectively employed electrophoretic deposition (EPD) using AC voltage to develop a lithium iron phosphate (LFP) Li-ion battery featuring pseudocapacitive properties and improved high C-rate performance. This method has significantly improved the battery's specific capacity, achieving an impressive 100 mAhg-1 at a 5 C discharge rate, which showcases its superior high-rate capability. Additionally, the battery displayed excellent reversibility during its performance cycles. These results confirm the EPD method's efficacy in improving LFP electrode performance, yielding notable improvements in cycling stability and high-rate capability. The enhanced capacity and high-rate performance of the electrophoretic-deposited LFP electrodes are largely due to the fast kinetics facilitated by pseudocapacitive behavior-induced charge storage and a high Li-ion diffusion constant measured in our EPD-deposited LFP electrodes. This underscores the practicality of our approach and the development of a fundamental test platform to investigate the pseudocapacitive charge storage mechanism in electrodes with typical battery-like behavior.

A particle packing electrode model for microstructure optimization of lithium-ion batteries

The microstructure of porous electrodes has a significant impact on the performance of lithium-ion batteries (LIBs). The critical challenge in theoretical research of porous electrodes is to construct an electrode model that properly describes its microstructure while ensuring solving efficiency. In this work, a particle packing electrode (PPE) model is used to analyze the charging dynamics of LIBs, which is constructed based on the randomness distribution of the active materials. After accurately predicting the experimental data, the PPE model illustrates two key factors governing the C-rate performance: The C-rate performance depends on the Li+ transfer in active material at low C-rate and depends on Li+ transfer in the electrolyte at high C-rate. By optimizing the uniformity of the particle size and the orderliness of the pore structure, LIBs achieve improved performance. This model offers novel possibilities for designing and optimizing electrode microstructures of LIBs.

Quasi-diffusion controlled high rate sodium-ion storage performance of flame pyrolysis derived spherical hard carbon

Hard carbon (HC) is identified as a potential anode for sodium ion batteries (SIBs) due to its outstanding electrochemical performance. However, selection of synthesis routes and its precursors remain crucial to develop the HC of desired microstructures for enhanced sodium-ion storage. Herein, we employed novel flame pyrolysis route to prepare spherical HC nanoparticles (<100 nm) from a liquid precursor derived from a low-cost bio-source. The as prepared carbon has been subjected to different calcination temperatures to optimize the porosity and surface area in order to achieve maximum sodium ion storage. The HC calcined at 1200 °C has shown the optimum electrochemical performance with a high reversible capacity of ∼287 mAh/g at 0.1C (1C = 300 mA/g). It shows 72 % of capacity retention after 490 cycles when cycled at 1C, with initial reversible specific capacity of ∼235 mAh/g. Excellent rate performance has been seen even at 20 C (6 A/g) with high specific capacity of 118 mAh/g at 70 % capacity retention after 2000 cycles, which is one of the highest values reported so far. Structural and morphological characterization of HC prepared at different temperatures are carried out using X-ray powder diffraction (XRD), small angle X-ray scattering (SAXS), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Particle size and morphology altogether have played significant role in achieving high specific capacity and C-rate performance by providing shorter diffusion path and larger sodium ion storage sites.

Synergistic Effect of 3D Electrode Architecture and In Situ Carbon Coating on the Electrochemical Performance of SnO2 Anodes for Sodium-Ion Batteries

SnO2, owing to its high theoretical capacity of 1378 mAh g−1 and low sodium insertion potential, is one of the attractive anode materials for Sodium-ion batteries (SIBs). However, extensive volume expansion (∼300 %), significant capacity loss, particle agglomeration, and low conductivity (1.82 × 10−8 S cm−1) of SnO2 limit its commercial applications. In this work, SnO2 nano-particles have been synthesized via a one-step hydrothermal method. Subsequently, 3D electrode architecture is developed using pitch-coated SnO2 nanomaterial onto carbon fiber (CF) current collector to mitigate the inherent challenges of SnO2 anode. Compared to the conventional SnO2 electrode, the optimized CF-SnO2- carbon composite electrodes show an excellent second-cycle stable capacity of 843 mAh g−1 at 30 mA g−1 with 95 % capacity retention after 100 cycles. This CF-SnO2-carbon composite electrode further delivers a stable capacity of 419 mAh g−1 at 300 mA g−1, having 80 % capacity retention after 200 cycles, and shows excellent C-rate performance. Conductive CF backbone and carbon coating accommodate the volume expansion of the active material, acting as a buffer matrix and reducing the electrode pulverization. This work entails a carbon fiber-based electrode engineering approach to fabricate a binder-less metal current collector-free freestanding electrode as a potential anode for SIBs.

Mechanically Interlocked Interphase with Energy Dissipation and Fast Li-Ion Transport for High-Capacity Lithium Metal Batteries.

Constructing an artificial solid electrolyte interphase (ASEI) on Li metal anodes (LMAs) is a potential strategy for addressing the dendrite issues. However, the mechanical fatigue of the ASEI caused by stress accumulation under the repeated deformation from the Li plating/stripping is not taken seriously. Herein, this work introduces a mechanically interlocked [an]daisy chain network (DC MIN) into the ASEI to stabilize the Li metal/ASEI interface by combining the functions of energy dissipation and fast Li-ion transport. The DC MIN featured by large-range molecular motions is cross-linked via efficient thiol-ene click chemistry; thus, the DC MIN has flexibility and excellent mechanical properties. As an ASEI, the crown ether units in DC MIN not only interact with the dialkylammonium of a flexible chain, forming the energy dissipation behavior but also coordinate with Li ion to support the fast Li-ion transport in DC MIN. Therefore, a stable 2800h-symmetrical cycling (1mA cm-2 ) and an excellent 5 C-rate (full cell with LiFePO4 ) performance are achieved by DC MIN-based ASEI. Furthermore, the 1-Ah pouch cell (LiNi0.88 Co0.09 Mn0.03 O2 cathode) with DC MIN-coated LMA exhibits improved capacity retention (88%) relative to the Control. The molecular design of DC MIN provides new insights into the optimization of an ASEI for high-energy LMAs.

Accelerating sulfur conversion kinetics via CoS2–MgS heterostructure for lithium sulfur batteries

The CoS2–MgS heterostructure combines the high catalytic activity of CoS2 (Co2+ oxidized to Co3+) and the fast Li+ migration kinetics of MgS, which significantly improve the C-rate performance and cycling stability of lithium–sulfur batteries.

Ester-Enhanced Inorganic-Rich Solid Electrolyte Interphase Enabled Dendrite-Free Fast-Charging Lithium Metal Batteries

Building lithium fluoride (LiF)-rich solid electrolyte interphases (SEIs) by the decomposition of fluorinated salts has been widely adopted to be effective to suppress lithium dendrite growth, thus prolonging the lifespan of fast-charging lithium metal batteries (LMBs). Nevertheless, the slow dissociation of LiF salts reduces both their utilization and the formation of inorganic SEI. Herein, cellulose acetate (CA) was incorporated into the electrolyte to create an inorganic-rich SEI through ester groups, where the lithiophilic oxygen atoms in the ester group (C═O) enhanced lithium-ion diffusion and anion dissociation rates. Therefore, rapid ion diffusion and dendrite-free anodes were achieved in the ester-based electrolyte with CA (named as CA-E). As a result, the lithium symmetric batteries with the CA-E electrolyte exhibited stable cycling performance for 5,000 h at a current density/capacity of 3 mA cm −2 /1 mAh cm −2 , while a short-circuiting was observed after ~450 h for the bare electrolyte. Benefiting from the rational design, lithium iron phosphate batteries with the CA-E electrolyte showed an excellent C-rate performance with a capacity of 100.7 mAh g −1 at the rate of 10 C. Moreover, a specific capacity of 110.3 mAh g −1 was maintained after 300 cycles at the rate of 6 C with a Coulombic efficiency of 99.87%. This work proposes a new approach to dendrite inhibitors for fast-charging LMBs.

Architecting the Microenvironment Skeleton of Active Materials in High-Capacity Electrodes by Self-Assembled Nano-Building Blocks.

In analogy to the cell microenvironment in biology, understanding and controlling the active-material microenvironment (ME@AM) microstructures in battery electrodes is essential to the successes of energy storage devices. However, this is extremely difficult for especially high-capacity active materials(AMs) like sulfur, due to the poor controlling on the electrode microstructures. To conquer this challenge, here, a semi-dry strategy based on self-assembled nano-building blocks is reported to construct nest-like robust ME@AM skeleton in a solvent-and-stress-less way. To do that, poly(vinylidene difluoride) nanoparticle binder is coated onto carbon-nanofibers (NB@CNF) via the nanostorm technology developed in the lab, to form self-assembled nano-building blocks in the dry slurry. After compressed into an electrode prototype, the self-assembled dry-slurry is then bonded by in-situ nanobinder solvation. With this strategy, mechanically strong thick sulfur electrodes are successfully fabricated without cracking and exhibit high capacity and good C-rate performance even at a high AM loading (25.0mgcm-2 by 90wt% in the whole electrode). This study may not only bring a promising solution to dry manufacturing of batteries, but also uncover the ME@AM structuring mechanism with nano-binder for guiding the design and control on electrode microstructures.

Development of Wet-Li2ZrO3-Coating Process for LiNi0.8Co0.1Mn0.1O2 Cathode for All-Solid-State Batteries

All-solid-state batteries are considered as the next-generation energy storage technology due to their potential for higher energy and power densities, as well as improved reliability and safety compared to conventional lithium-ion batteries with liquid electrolytes[1,2]. However, technical challenges remain in achieving the necessary interface stability between the cathode active material and solid electrolyte, e.g., Li6PS5Cl[3,4]. Herein, we present a facile wet coating process for achieving a uniform and conformal Li2ZrO3 coating on LiNi0.8Co0.1Mn0.1O2 cathode particles to improve the performance of thio-sulfide-based all-solid-state batteries. The coating process was based on the addition of zirconium and lithium precursors to absolute ethanol-cathode dispersion, resulting in the adsorption of ZrO2+ and Li+ species onto LiNi0.8Co0.1Mn0.1O2 particles. After evaporating the solvent, the precipitate was calcinated, whereby the effects of different precursor weight percentages, types of precursors, conditions of solvent evaporation, and calcination temperatures on the distribution, uniformity, and crystallinity of the coating layers were subject of investigation. A wide spectrum of techniques has been used to evaluate phases, structure, and microstructure of the coated cathode particles. The optimal coating thickness has been determined by testing the coated cathodes in pellet-type all-solid-state batteries, composed by a composite cathode (ratio between LiNi0.8Co0.1Mn0.1O2, Li6PS5Cl, and conductive carbon: 11:16:1), Li-In alloy as anode, and Li6PS5Cl as separator and evaluating the electrochemical performance in respect of the initial discharge capacity, capacity retention after 200 cycles, C-rate performance, and cycling stability. ASSBs containing LiNi0.8Co0.1Mn0.1O2 cathode with an optimized Li2ZrO3-coating thickness of 10 nm showed not only increased specific capacity during the initial discharge (from 125 mAh/g to 149 mAh/g) but also exhibited improved capacity retention from 83% to 98% after 200 cycles. Reference [1] Janek J, Zeier WG. A solid future for battery development. Nature Energy. 2016, 8;1(9):1-4.[2] Tatsumisago M, Nagao M, Hayashi A. Recent development of sulfide solid electrolytes and interfacial modification for all-solid-state rechargeable lithium batteries. Journal of Asian Ceramic Societies. 2013, 1;1(1):17-25.[3] Culver SP, Koerver R, Zeier WG, Janek J. On the functionality of coatings for cathode active materials in thiophosphate‐based all‐solid‐state batteries. Advanced Energy Materials. 2019, 9(24):1900626.[4] Minnmann P, Strauss F, Bielefeld A, Ruess R, Adelhelm P, Burkhardt S, Dreyer SL, Trevisanello E, Ehrenberg H, Brezesinski T, Richter FH. Designing Cathodes and Cathode Active Materials for Solid‐State Batteries. Advanced Energy Materials. 2022, 12(35):2201425. Acknowledgements DR acknowledge financial support by Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development and the Christian Doppler Research Association (Christian Doppler Laboratory for Solid-State Batteries).

Carbon: A Ubiquitous Electrode Material for Lithium-Based Rechargeable Batteries

In recent times, research has been directed to develop high-capacity anodes along with high-energy-density (high capacity and high voltage) and safe Lithium-ion battery (LIB) cathodes to power electric vehicles (EV’s). State-of-the-art lithium-ion cells use layered transition metal oxides (LiCoO2, LiNi1/3Mn1/3Co1/3 or LiNi0.8Co0.15Al0.15O2), or Phosphates (LiFePO4), Mn-based spinels (LiMn2O4) as cathodes and graphitic carbon as anode [1-2]. The nominal capacities of most of these cathodes range between 140-180 mAh g-1 when cycled up to 4.2 V. This is only half the specific capacity of graphite anode (372 mAh g-1). Thus, there has been intense research activity in the last decade to develop high-capacity anodes or high energy (high capacity and high voltage) and safe cathodes for lithium-ion batteries (LIBs) [1-2].Eliminating binders and carbon diluents and replacing carbon fiber-based 3D electrode architectures can improve the capacity utilization and C-rate performance, thereby improving energy density, cycle life, and safety of LIBs. The presentation will be focused on the development of organic binder and conducting diluent-free carbon fiber-based 3D electrodes architectures for LIBs, where the conventional copper (Cu) and aluminum foil (Al) foil current collectors are replaced with highly conductive carbon fibers (CFs). In this approach, the petroleum pitch (P-pitch) is used as a binder that adequately coats between the CFs and active nanoparticles (NPs) at high temperatures to form a uniform continuous layer of carbon coating along the exterior surfaces of NPs and 3D CFs. As a result, the electrodes assembly delivers superior electrochemical performances than conventional electrode fabrications. 3D electrode architecture of LiFePO4, FeF3, Li2MnSiO4 cathodes, and Si-C anodes will be presented [3-5].Dual carbon batteries (DCBs) based on LIB electrolytes have been evolving in recent times [5]. In DCBs, both electrodes consist of carbonaceous materials, and the ions from the electrolyte intercalate and deintercalate into the electrode matrix. During the charge, the cations and anions get inserted into the anode and cathode, respectively, and during discharge, the process is reversed. A DCB based on the 3D electrode architecture of carbon (zero transition metal ion) will be discussed. A DCB based on fully graphitic carbon fiber can have a nominal voltage of 4.65 V and can deliver energy densities of 92.7, and 110.9 Wh kg−1 at a power density of 114 W kg−1 for the cells cycled at 3.0–5.0 and 3.0–5.2 V, respectively. It is believed that the study presented here may contribute to the future development of carbon fiber-based dual-carbon and lithium-ion batteries.

Surface Modification on TiNb2O7 Anode Via Atmospheric Pressure Plasma Jet for High-Rate Lithium-Ion Battery

Lithium-ion battery is one of the most vital energy storage devices due to high energy density property. In anode, TiNb2O7 (TNO) demonstrates high capacity as compared to Li4Ti5O12 materials. It is attractive for its high safety because of adequate Fermi level, implying that the solid electrolyte interface would not form during the charging and discharging process. This work provides a promising method of modifying the electrode, which includes PVdF, conductive carbon, and TNO, using the technology of atmospheric pressure plasma jet (APPj) treatment. This method is potential to accomplish roll-to-roll modification in the industry without any complex synthesis processes. In addition, APPj method is a time-effective process to treat the electrode. It has found that the treatment via APPj enhances the electrochemical performance by N-doped decoration on conductive carbon, as well as defects manufacturing of the TNO anode materials, and electrolyte wettability improvement on binder. The surface free energy of the APP-20 sample increases, improving the wettability of the electrolyte and contributing to an enhanced electrochemical performance. The C-rate performance of APP-20 improves significantly at 10C as compared to the sample without treatment. Also, the cycle test of APP-10 provides high retention after 300 cycles at 1C. In summary, this work promotes a feasible and facile treatment for roll-to-roll processing, and the mechanism could be established. APPj In short, the modification technique of APPj is an affordable method to apply in the lithium-ion battery of the industry manufacturing.

Self-healing composite anode induced by liquid-metal interlayer for flexible Zn ion storage application

Aqueous zinc (Zn)-ion hybrid supercapacitor (ZHS) has emerged as an attractive energy storage technology for wearables on their advantages of high safety and low cost. However, Zn anodes seriously undermine the durability of ZHSs due to the influences caused by Zn dendrite growth and side reactions at the electrode-electrolyte interface. Herein, we attempt to resolve this issue by introducing Ga-based liquid metal (LM)-incorporated carbon cloth as a flexible anode current collector for Zn storage. The high fluidity and deformability of LM ensure a superior self-healing anode during repeated Zn plating/stripping processes. Additionally, the unique liquid-liquid interface between LM on electrode and electrolyte facilitates lattice dynamical property of the electrode. Consequently, ZHS devices with such self-healing electrode demonstrate enhanced cycling stability and C-rate performance. Our work suggests a novel strategy to use LM-based composite anode current collector for fabricating high-performance ZHSs, which potentially promotes the development of flexible electronics for future wearable applications.

Grain-growth Inhibitor with Three-section-sintering for Highly Dispersed Single-crystal NCM90 Cubes.

Single crystallization of LiNix Coy Mn1-x-y O2 (NCM) is currently an effective strategy to improve the cycling life of NCM cathode, owing to the reduced surface area and enhanced mechanical strength, but the application of single crystal NCM(SC-NCM) is being hindered by severe particle agglomeration and poor C-rate performance. Here, a strategy of three-section-sintering(TSS) with the presence of grain-growth inhibitor was proposed, in which, the TSS includes three sections of phase-formation, grain-growth and phase-preservation. While, the addition of MoO3 inhibits the grain growth and restrains the particle agglomeration. With the help of TSS and 1 mol % of MoO3 , highly dispersed surface Mo-doped SC-NCM(MSC-NCM) cubes are obtained with the average diameter of 1.3 μm. Benefiting from the surface Mo-doping and the reduced surface energy, the Li+ -migration preferred (1 0 4) crystalline facet is exposed as the dominant plane in MSC-NCM cubes, because of which, C-rate performance is significantly improved compared with the regular SC-NCM. Furthermore, this preparation strategy is compatible well with the current industrial production line, providing an easy way for the large-scale production of SC-NCM.

3D Electrode architecture of high surface area carbon-sulfur composite as high energy density cathode for lithium-sulfur battery

High-performance lithium-sulfur (Li-S) battery is a potential candidate for next-generation energy storage systems to mitigate the ever-rising energy demand. The low cost of sulfur, eco-friendliness, and high energy density compared to the emerging LIBs (450 Wh kg−1 for Li-S batteries vs. 150–250 Wh kg−1 for LIBs) inspires the research on Li–S technology. In this work, carbon fiber-based free-standing electrodes are fabricated using a high surface area carbon-sulfur (HSAC-S) composite synthesized by the melt-diffusion method. The porous carbon host facilitates high sulfur loading in the void spaces and benefits the electrolyte infiltration and Li-ion diffusivity. Electrochemistry reveals that HSAC-S@CF exhibits an enhanced discharge capacity of 1000 mAh g−1 (750 mAh g−1 for HSAC-S@Al) in the 2nd cycle and maintains 620 mAh g−1 capacity till the 100th cycle. In comparison, HSAC-S@Al delivers 350 mAh g−1 capacity at the 80th cycle at a current density of 100 mA g−1. Besides, at 200 mA g−1, the free-standing electrode HSAC-S@CF delivers an initial capacity of 600 mAh g−1 (498 mAh g−1 HSAC-S@Al) and retains 497 mAh g−1 till the 100th cycle with 83 % capacity retention (60 % HSAC-S@Al). HSAC-S@CF displays good C-rate performance at a higher current density of 1 A g−1 (408 mAh g−1) and 1.5 A g−1 (346 mAh g−1). The conductive CF backbone provides mechanical stability, accommodates volume changes, and reduces particle agglomeration. The internal void spaces of the CF matrix act as a reservoir for polysulfides and minimize the shuttling effect. This work represents an effective cathode modification approach to understand the impact of high surface area carbon additives on free-standing 3D electrode architecture and its interaction with sulfur for improving the capacity and cycling stability in Li-S batteries.

Lithium phosphate incorporated carbon nanotube interlayer as an efficient polysulfide immobilizer for high performance lithium sulfur batteries

Lithium-sulfur (Li-S) batteries are the potential alternative for the lithium-ion batteries, owing to their remarkable energy density and specific capacity. Nevertheless, the lower utilization of active materials and the “shuttle effect” have impeded their widespread commercialization. To address these hurdles, a pioneering method has been proposed, involving a lithium phosphate-incorporated multi-walled carbon nanotube (Li3PO4@MWCNT) interlayer. The Li3PO4@MWCNT interlayer primarily serves as a physical barrier against polysulfide shuttling. Its highly conductive cross-link structure enables it to adsorb chemically derived lithium polysulfides (LiPS) and catalyze their conversion by incorporating Li3PO4 into the MWCNT matrix. This synergistic effect of immobilizing and converting LiPS results in a significant reduction in the “shuttle effect,” leading to enhanced sulfur utilization. The experimental results evidence the enhanced performance of the Li-S cells, with a capacity of 381 mAh g−1 at 0.1C and high C-rate performance of 393 mAh g−1 at 1C.

Manipulating Lewis acid–base interactions in metal-organic frameworks for optimizing zinc-ion diffusion, deposition, and reaction behaviors

The dendrite growth and side reactions of Zn anodes severely impair the performance of aqueous rechargeable Zn metal batteries. Although various artificial protective layers (APLs) have been developed to address these issues, the engineering of multifunctional APLs at the molecular level remains a challenge. Herein, a strategy of manipulating the Lewis acid–base interactions at the molecular level within metal-organic frameworks (MOFs) was conducted to optimize the Zn2+ diffusion, deposition, and reaction behaviors for stabilizing Zn anodes. A series of APLs based on isostructural UiO-66 type MOFs with different functional groups (–NH2, –OH, –SO3H, and –COOH) were developed to systematically study the influence of different host-guest interactions for zinc deposition. The results show that the more Lewis base chemical groups result in the improved ability of MOFs in trapping Zn2+, transporting Zn2+, accelerating the desolvation of Zn2+, regulating pH values, and decreasing the side reactions, rendering suppressed dendrite growth. Thus, UiO-66-2COOH shows the best performance in regulating Zn2+ deposition, delivering an excellent Zn plating/stripping cycling of up to 2700 h at 1 mAh/cm2 and 1600 h at 5 mAh/cm2, as well as full cells with remarkably improved C-rate and cycling performance.