Recent Advances and Perspectives in Lithium-Sulfur Pouch Cells

Lithium–sulfur batteries (LSBs) are considered one of the most promising candidates for next-generation energy storage owing to their large energy capacity. Tremendous effort has been devoted to overcoming the inherent problems of LSBs to facilitate their commercialization, such as polysulfide shuttling and dendritic lithium growth. Pouch cells present additional challenges for LSBs as they require greater electrode active material utilization, a lower electrolyte–sulfur ratio, and more mechanically robust electrode architectures to ensure long-term cycling stability. In this review, the critical challenges facing practical Li–S pouch cells that dictate their energy density and long-term cyclability are summarized. Strategies and perspectives for every major pouch cell component—cathode/anode active materials and electrode construction, separator design, and electrolyte—are discussed with emphasis placed on approaches aimed at improving the reversible electrochemical conversion of sulfur and lithium anode protection for high-energy Li–S pouch cells.

Cobalt Coordinated Cyano Covalent-Organic Framework for High-Performance Potassium-Organic Batteries

Potassium ion batteries (PIBs) are expected to become the next large-scale energy storage candidates due to its low cost and abundant resources. And the covalent organic framework (COF), with designable periodic organic structure and ability to organize redox active groups predictably, has been considering as the promising organic electrode candidate for PIB. Herein, we report the facile synthesis of the cyano-COF with Co coordination via a facile microwave digestion reaction and its application in the high-energy potassium ion batteries for the first time. The obtained COF-Co material exhibits the enhanced π-π accumulation and abundant defects originated from the Co interaction with the two-dimensional layered sheet structure of COF, which are beneficial for its energy-storage application. Adopted as the inorganic-metal boosted organic electrode for PIBs, the COF-Co with Co coordination can promote the formation of the π-K⁺ interaction, which could lead to the activation of aromatic rings for potassium-ion storage. Besides, the porous two-dimensional layered structure of COF-Co with abundant defects can also promote the shortened diffusion distance of ion/electron with promoted K⁺ insertion/extraction ability. Enhanced cycling stability with large reversible capacity (371 mAh g^-1 after 400 cycles at 100 mA g^-1) and good rate properties (105 mAh g^-1 at 2000 mA g^-1) have been achieved for the COF-Co electrode.

Tailoring Co3d and O2p Band Centers to Inhibit Oxygen Escape for Stable 4.6 V LiCoO2 Cathodes

High-voltage LiCoO₂ delivers a high capacity but sharp fading is a critical issue, and the capacity decay mechanism is also poorly understood. Herein, we clarify that the escape of surface oxygen and Li-insulator Co₃ O₄ formation are the main causes for the capacity fading of 4.6 V LiCoO₂ . We propose the inhibition of the oxygen escape for achieving stable 4.6 V LiCoO₂ by tailoring the Co3d and O2p band center and enlarging their band gap with MgF₂ doping. This enhances the ionicity of the Co-O bond and the redox activity of Co and improves cation migration reversibility. The inhibition of oxygen escape suppresses the formation of Li-insulator Co₃ O₄ and maintains the surface structure integrity. Mg acts as a pillar, providing a stable and enlarged channel for fast Li⁺ intercalation/extraction. The modulated LiCoO₂ shows almost zero strain and achieves a record capacity retention at 4.6 V: 92 % after 100 cycles at 1C and 86.4 % after 1000 cycles at 5C.

Commercialization-Driven Electrodes Design for Lithium Batteries: Basic Guidance, Opportunities, and Perspectives

Current lithium-ion battery technology is approaching the theoretical energy density limitation, which is challenged by the increasing requirements of ever-growing energy storage market of electric vehicles, hybrid electric vehicles, and portable electronic devices. Although great progresses are made on tailoring the electrode materials from methodology to mechanism to meet the practical demands, sluggish mass transport, and charge transfer dynamics are the main bottlenecks when increasing the areal/volumetric loading multiple times to commercial level. Thus, this review presents the state-of-the-art developments on rational design of the commercialization-driven electrodes for lithium batteries. First, the basic guidance and challenges (such as electrode mechanical instability, sluggish charge diffusion, deteriorated performance, and safety concerns) on constructing the industry-required high mass loading electrodes toward commercialization are discussed. Second, the corresponding design strategies on cathode/anode electrode materials with high mass loading are proposed to overcome these challenges without compromising energy density and cycling durability, including electrode architecture, integrated configuration, interface engineering, mechanical compression, and Li metal protection. Finally, the future trends and perspectives on commercialization-driven electrodes are offered. These design principles and potential strategies are also promising to be applied in other energy storage and conversion systems, such as supercapacitors, and other metal-ion batteries.

Thermal-Responsive and Fire-Resistant Materials for High-Safety Lithium-Ion Batteries

As one of the most efficient electrochemical energy storage devices, the energy density of lithium-ion batteries (LIBs) has been extensively improved in the past several decades. However, with increased energy density, the safety risk of LIBs becomes higher too. The frequently occurred battery accidents worldwide remind us that safeness is a crucial requirement for LIBs, especially in environments with high safety concerns like airplanes and military platforms. It is generally recognized that the catastrophic thermal runaway (TR) event is the major cause of LIBs related accidents. Tremendous efforts have been devoted to coping with the TR concerns in LIBs, and thus enhance battery safety. This review first gives an introduction to the fundamentals of LIBs and the origins of safety issues. Then, the authors summarize the recent advances to improve the safety of LIBs with a unique focus on thermal-responsive and fire-resistant materials. Finally, a perspective is proposed to guide future research directions in this field. It is anticipated this review will stimulate inspiration and arouse extensive studies on further improvement in battery safety.

Heterostructured CoS2/CuCo2S4@N-doped carbon hollow sphere for potassium-ion batteries

Potassium ions batteries (PIBs) have been regarded as a promising choice for electrical energy storage technology due to the wide distribution of potassium resources. However, developing low-cost and robust earth-rich anode materials is still a major challenge for the practical and scalable usage of PIBs. Herein, for the first time, we developed nitrogen doped carbon coating CoS₂/CuCo₂S₄ heterostructure (CoS₂/CuCo₂S₄@NCs) hollow spheres and evaluated as anode for PIBs. The CoS₂ and CuCo₂S₄ heterostructure interface could generate a built-in electric field, which can fasten electrons transportation. The nanostructures could shorten the diffusion length of K⁺ and provide large surface area to contact with electrolytes. Furthermore, the inner hollow sphere morphology along with the carbon layer could accommodate the volume expansion during cycling. What's more, the N-doped carbon could increase the conductivity of the anodes. Benefitting from the above features, the CoS₂/CuCo₂S₄@NCs displays an outstanding rate capability (309 mAh g^-1 at 500 mA g^-1 after 250 cycles) and a long-term cycling life (112 mAh g^-1 at 1000 mA g^-1 after 1000 cycles) in ether-based electrolyte. Conversion reaction mechanism in CoS₂/CuCo₂S₄@NCs anode is also revealed through ex situ XRD characterizations. This work provides a practical direction for investigating metal sulfides as anode for PIBs.

FeNb2O6/reduced graphene oxide composites with intercalation pseudo-capacitance enabling ultrahigh energy density for lithium-ion capacitors

Lithium-ion capacitors (LICs), which combine the characteristics of lithium-ion batteries and supercapacitors, have been well studied recently. Extensive efforts are devoted to developing fast Li⁺ insertion/deintercalation anode materials to overcome the discrepancy in kinetics between battery-type anodes and capacitive cathodes. Herein, we design a FeNb₂O₆/reduced graphene oxide (FNO/rGO) hybrid material as a fast-charge anode that provides a solution to the aforementioned issue. The synergetic combination of FeNb₂O₆, whose unique structure promotes fast electron transport, and highly conductive graphene shortens the Li⁺ diffusion pathways and enhances structural stability, leading to excellent electrochemical performance of the FNO/rGO anode, including a high capacity (770 mA h g⁻¹ at 0.05 A g⁻¹) and long cycle stability (95.3% capacitance retention after 500 cycles). Furthermore, the FNO/rGO//ACs LIC achieves an ultrahigh energy density of 135.6 W h kg⁻¹ (at 2000 W kg⁻¹) with a wide working potential window from 0.01 to 4 V and remarkable cycling performance (88.5% capacity retention after 5000 cycles at 2 A g⁻¹).

FeNb₂O₆/reduced graphene oxide (FNO/rGO) hybrid material as a fast charge anode for LICs that provides a solution to overcome the discrepancy in kinetics between battery-type anodes and capacitive cathodes.

Poly(2-Hydroxyethyl methacrylate-co-N,N-dimethylacrylamide)-Coated Quartz Crystal Microbalance Sensor: Membrane Characterization and Proof of Concept

Application-oriented hydrogel properties can be obtained by modifying the synthesis conditions of the materials. The purpose of this study is to achieve customized properties for sensing applications of hydrogel membranes based on poly(2-hydroxyethyl methacrylate), HEMA and N,N-dimethylacrylamide, DMAa. Copolymer p(HEMA-co-DMAa) hydrogels were prepared by varying the DMAa monomer ratio from 0-100% in 20% increments. Hydrogel membranes were characterized by attenuated infrared spectroscopy. Swelling and sorption were evaluated using cation solutions. Copolymers were also synthesized on the gold surface of quartz crystal microbalances (QCM) as coating membranes. A proof of concept was conducted for approaching the design and development of QCM sensors based on P(DMAa-co-HEMA)-membranes. Results showed that the water and ion adsorption capacity of hydrogel membranes increased with higher DMAa content. Membranes are not selective to a specific location but did show different transport features with each cation. The QCM coated with the selected membrane presented linear relationships between resonance frequency and ions concentration in solution (10-120 ppm). As a consequence, hydrogel membranes obtained are promising for the development of future biosensing devices.

Rational Design of Effective Binders for LiFePO4 Cathodes

Polymer binders are critical auxiliary additives to Li-ion batteries that provide adhesion and cohesion for electrodes to maintain conductive networks upon charge/discharge processes. Therefore, polymer binders become interconnected electrode structures affecting electrochemical performances, especially in LiFePO4 cathodes with one-dimensional Li+ channels. In this paper, recent improvements in the polymer binders used in the LiFePO4 cathodes of Li-ion batteries are reviewed in terms of structural design, synthetic methods, and working mechanisms. The polymer binders were classified into three types depending on their effects on the performances of LiFePO4 cathodes. The first consisted of PVDF and related composites, and the second relied on waterborne and conductive binders. Profound insights into the ability of binder structures to enhance cathode performance were discovered. Overcoming the bottleneck shortage originating from olivine structure LiFePO4 using efficient polymer structures is discussed. We forecast design principles for the polymer binders used in the high-performance LiFePO4 cathodes of Li-ion batteries. Finally, perspectives on the application of future binder designs for electrodes with poor conductivity are presented to provide possible design directions for chemical structures.

Hierarchical MnV2O4 double-layer hollow sandwich nanosheets confined by N-doped carbon layer as anode for high performance lithium-ion batteries

Binary transition metal oxides, especially vanadate metal oxides, are highly desirable for lithium-ion batteries (LIBs) anode materials due to their low-budget and high theoretical lithium storage capacity. However, low conductivity and poor cycle stability caused by volume changes during charge and discharge limit their grid-scale applications. Herein, a novel spinel MnV₂O₄ double-layer hollow sandwich nanosheets enclosed in N-doped porous carbon layer (MnV₂O₄/NC) was efficiently synthesized in 5 min by microwave-assisted and in-situ pyrolysis the coated polydopamine. MnV₂O₄/NC shows the superior performance as anode for LIBs with a specific capacities of 760 mA h g^-1 at 1000 mA g^-1 and outstanding of cycling stability with a specific capacities of 525.5 mA h g^-1 after 1000 cycles even at 5000 mA g^-1, respectively, which due to its unique double-layer hollow sandwich microstructure, mixed lithium storage mechanism and in-situ coating of nitrogen-doped carbon layer.

Reversible Magnesium Metal Anode Enabled by Cooperative Solvation/Surface Engineering in Carbonate Electrolytes

Magnesium metal anode holds great potentials toward future high energy and safe rechargeable magnesium battery technology due to its divalent redox and dendrite-free nature. Electrolytes based on Lewis acid chemistry enable the reversible Mg plating/stripping, while they fail to match most cathode materials toward high-voltage magnesium batteries. Herein, reversible Mg plating/stripping is achieved in conventional carbonate electrolytes enabled by the cooperative solvation/surface engineering. Strongly electronegative Cl from the MgCl₂ additive of electrolyte impairs the Mg…O = C interaction to reduce the Mg²⁺ desolvation barrier for accelerated redox kinetics, while the Mg²⁺-conducting polymer coating on the Mg surface ensures the facile Mg²⁺ migration and the effective isolation of electrolytes. As a result, reversible plating and stripping of Mg is demonstrated with a low overpotential of 0.7 V up to 2000 cycles. Moreover, benefitting from the wide electrochemical window of carbonate electrolytes, high-voltage (> 2.0 V) rechargeable magnesium batteries are achieved through assembling the electrode couple of Mg metal anode and Prussian blue-based cathodes. The present work provides a cooperative engineering strategy to promote the application of magnesium anode in carbonate electrolytes toward high energy rechargeable batteries.

Electrolyte Design Enabling a High-Safety and High-Performance Si Anode with a Tailored Electrode-Electrolyte Interphase

Silicon (Si) anodes are advantageous for application in lithium-ion batteries in terms of their high theoretical capacity (4200 mAh g^-1 ), appropriate operating voltage (<0.4 V vs Li/Li⁺ ), and earth-abundancy. Nevertheless, a large volume change of Si particles emerges with cycling, triggering unceasing breakage/re-formation of the solid-electrolyte interphase (SEI) and thereby the fast capacity degradation in traditional carbonate-based electrolytes. Herein, it is demonstrated that superior cyclability of Si anode is achievable using a nonflammable ether-based electrolyte with fluoroethylene carbonate and lithium oxalyldifluoroborate dual additives. By forming a high-modulus SEI rich in fluoride (F) and boron (B) species, a high initial Coulombic efficiency of 90.2% is attained in Si/Li cells, accompanied with a low capacity-fading rate of only 0.0615% per cycle (discharge capacity of 2041.9 mAh g^-1 after 200 cycles). Full cells pairing the unmodified Si anode with commercial LiFePO₄ (≈13.92 mg cm^-2 ) and LiNi_0.5 Mn_0.3 Co_0.2 O₂ (≈17.9 mg cm^-2 ) cathodes further show extended service life to 150 and 60 cycles, respectively, demonstrating the superior cathode-compatibility realized with a thin and F, B-rich cathode electrolyte interface. This work offers an easily scalable approach in developing high-performance Si-based batteries through Si/electrolyte interphase regulation.

Conversion-Alloying Anode Materials for Sodium Ion Batteries

The past decade has witnessed a rapidly growing interest toward sodium ion battery (SIB) for large-scale energy storage in view of the abundance and easy accessibility of sodium resources. Key to addressing the remaining challenges and setbacks and to translate lab science into commercializable products is the development of high-performance anode materials. Anode materials featuring combined conversion and alloying mechanisms are one of the most attractive candidates, due to their high theoretical capacities and relatively low working voltages. The current understanding of sodium-storage mechanisms in conversion-alloying anode materials is presented here. The challenges faced by these materials in SIBs, and the corresponding improvement strategies, are comprehensively discussed in correlation with the resulting electrochemical behavior. Finally, with the guidance and perspectives, a roadmap toward the development of advanced conversion-alloying materials for commercializable SIBs is created.

Confronting the Challenges in Lithium Anodes for Lithium Metal Batteries

With the low redox potential of -3.04 V (vs SHE) and ultrahigh theoretical capacity of 3862 mAh g-1 , lithium metal has been considered as promising anode material. However, lithium metal battery has ever suffered a trough in the past few decades due to its safety issues. Over the years, the limited energy density of the lithium-ion battery cannot meet the growing demands of the advanced energy storage devices. Therefore, lithium metal anodes receive renewed attention, which have the potential to achieve high-energy batteries. In this review, the history of the lithium anode is reviewed first. Then the failure mechanism of the lithium anode is analyzed, including dendrite, dead lithium, corrosion, and volume expansion of the lithium anode. Further, the strategies to alleviate the lithium anode issues in recent years are discussed emphatically. Eventually, remaining challenges of these strategies and possible research directions of lithium-anode modification are presented to inspire innovation of lithium anode.

Surface Modification and Functional Structure Space Design to Improve the Cycle Stability of Silicon Based Materials as Anode of Lithium Ion Batteries

Silicon anode is considered as one of the candidates for graphite replacement due to its highest known theoretical capacity and abundant reserve on earth. However, poor cycling stability resulted from the “volume effect” in the continuous charge-discharge processes become the biggest barrier limiting silicon anodes development. To avoid the resultant damage to the silicon structure, some achievements have been made through constructing the structured space and pore design, and the cycling stability of the silicon anode has been improved. Here, progresses on designing nanostructured materials, constructing buffered spaces, and modifying surfaces/interfaces are mainly discussed and commented from spatial structure and pore generation for volumetric stress alleviation, ions transport, and electrons transfer improvement to screen out the most effective optimization strategies for development of silicon based anode materials with good property.

Lithium-Ion Battery Operation, Degradation, and Aging Mechanism in Electric Vehicles: An Overview

Understanding the aging mechanism for lithium-ion batteries (LiBs) is crucial for optimizing the battery operation in real-life applications. This article gives a systematic description of the LiBs aging in real-life electric vehicle (EV) applications. First, the characteristics of the common EVs and the lithium-ion chemistries used in these applications are described. The battery operation in EVs is then classified into three modes: charging, standby, and driving, which are subsequently described. Finally, the aging behavior of LiBs in the actual charging, standby, and driving modes are reviewed, and the influence of different working conditions are considered. The degradation mechanisms of cathode, electrolyte, and anode during those processes are also discussed. Thus, a systematic analysis of the aging mechanisms of LiBs in real-life EV applications is achieved, providing practical guidance, methods to prolong the battery life for users, battery designers, vehicle manufacturers, and material recovery companies.

Facile Synthesis of Polyphenothiazine as a High-Performance p-Type Cathode for Rechargeable Lithium Batteries

p-Type electroactive polymers are promising cathodes for dual-ion batteries but cost-effective candidates are still lacking. In this study, the p-type polymer polyphenothiazine (PPTZ) is synthesized by a facile one-step oxidation polymerization from the low-cost phenothiazine (PTZ) monomer. As a cathode for rechargeable lithium batteries, PPTZ shows superior electrochemical performance to previously reported PTZ-based polymers with complicated structures and syntheses. For example, PPTZ has a high reversible capacity of 157 mAh g^-1 within 2.5-4.3 V vs. Li⁺ /Li with an average discharge voltage of 3.5 V, and a high capacity retention of 77 % after 500 cycles. The highly reversible one-electron redox mechanism of PPTZ is also investigated in detail by electrochemical testing, ex situ FT-IR and X-ray photoelectron spectroscopy, and DFT calculations. PPTZ has the potential to serve as an attractive p-type cathode material for practical applications and the facile synthesis may be also extended to other polymer cathodes based on N-heteroaromatic units.

Regulation of SEI Formation by Anion Receptors to Achieve Ultra-Stable Lithium-Metal Batteries

Despite high specific capacity (3860 mAh g^-1 ), the utilization of Li-metal anodes in rechargeable batteries are still hampered due to their insufficient cyclability. Herein, we report an anion-receptor-mediated carbonate electrolyte with improved performance and can ameliorate the solid electrolyte interphase (SEI) composition comparing to the blank electrolyte. It demonstrates a high average Coulombic efficiency (97.94 %) over 500 cycles in the Li/Cu cell at a capacity of 1 mAh cm^-2 . Raman spectrum and molecular modelling further clarify the screening effects of the anion receptor on the Li⁺ -PF₆ ^- ion coupling that results in the enhanced ion dynamics. The X-ray photoelectron spectroscopy (XPS) distinguishes the disparities in the SEI components of the developed electrolyte and the blank one, which is rationalized by the molecular insights of the Li-metal/electrolyte interface. Thus, we prepare a 2.5 Ah prototype pouch cell, exhibiting a high energy density (357 Wh kg^-1 ) with 90.90 % capacity retention over 50 cycles.

Mechanical Failure Mechanism of Silicon-Based Composite Anodes under Overdischarging Conditions Based on Finite Element Analysis

Overdischarge is a severe safety issue that can induce severe mechanical failure of electrode materials in lithium-ion batteries. A considerable volume change of silicon-based composite anodes undoubtedly further aggravates the mechanical failure. However, the mechanical failure mechanism of silicon-based composite anodes under overdischarging conditions still lacks in-depth understanding despite many efforts paid under normal charging conditions. Herein, we have modeled and tracked the mechanical failure evolution of silicon/carbon nanofibers, a typical silicon-based anode, under overdischarging conditions based on the finite element simulation, with derived optimization strategies of optimal Young's modulus and stable microstructure. The severe contact damage between silicon nanoparticles and carbon nanofibers, which causes larger shedding and breakage risks, has been found to contribute to mechanical failure. To improve the electrode stability, an optimal Young's modulus interval ranging from ∼75 to ∼150 GPa is found. Furthermore, increasing the embedding depth of silicon nanoparticles in carbon nanofibers has proven to be an effective strategy for improving electrochemical stability due to the faster lithium salt diffusion and more uniform current density distribution, which was further verified by the experimental capacity retention ratio of carbon-coated silicon and silicon/carbon nanofibers (84 vs 75% after 100 cycles). Our results provide meaningful insights into the mechanical failure of silicon-based composite anodes during overdischarging, giving reasonable guidance for electrode safety designs and performance optimization.

Unique Carbonate-Based Single Ion Conducting Block Copolymers Enabling High-Voltage, All-Solid-State Lithium Metal Batteries

Safety and high-voltage operation are key metrics for advanced, solid-state energy storage devices to power low- or zero-emission HEV or EV vehicles. In this study, we propose the modification of single-ion conducting polyelectrolytes by designing novel block copolymers, which combine one block responsible for high ionic conductivity and the second block for improved mechanical properties and outstanding electrochemical stability. To synthesize such block copolymers, the ring opening polymerization (ROP) of trimethylene carbonate (TMC) monomer by the RAFT-agent having a terminal hydroxyl group is used. It allows for the preparation of a poly(carbonate) macro-RAFT precursor that is subsequently applied in RAFT copolymerization of lithium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethylsulfonyl)imide and poly(ethylene glycol) methyl ether methacrylate. The resulting single-ion conducting block copolymers show improved viscoelastic properties, good thermal stability (T onset up to 155 °C), sufficient ionic conductivity (up to 3.7 × 10-6 S cm-1 at 70 °C), and high lithium-ion transference number (0.91) to enable high power. Excellent plating/stripping ability with resistance to dendrite growth and outstanding electrochemical stability window (exceeding 4.8 V vs Li+/Li at 70 °C) are also achieved, along with enhanced compatibility with composite cathodes, both LiNiMnCoO2 - NMC and LiFePO4 - LFP, as well as the lithium metal anode. Lab-scale truly solid-state Li/LFP and Li/NMC lithium-metal cells assembled with the single-ion copolymer electrolyte demonstrate reversible and very stable cycling at 70 °C delivering high specific capacity (up to 145 and 118 mAh g-1, respectively, at a C/20 rate) and proper operation even at a higher current regime. Remarkably, the addition of a little amount of propylene carbonate (∼8 wt %) allows for stable, highly reversible cycling at a higher C-rate. These results represent an excellent achievement for a truly single-ion conducting solid-state polymer electrolyte, placing the obtained ionic block copolymers on top of polyelectrolytes with highest electrochemical stability and potentially enabling safe, practical Li-metal cells operating at high-voltage.

Incentivizing Innovation: The Causal Role of Government Subsidies on Lithium-Ion Battery Research and Development

Governments design and implement policies to achieve a variety of goals, but perhaps none are as pressing as shifting national economies away from non-renewable fuels and towards more sustainable, environmentally-friendly technologies. To incentivize such transitions, governments provide subsidies to private and public companies to innovate, i.e., to engage in research and development (R&D) to develop those technologies. However, the question of the companies is using government subsidies (GS) to perform R&D and its answer determines the effectiveness of government policies. Consequently, this paper seeks to answer this question through investigating Chinese lithium-ion battery (LiB) firms and the GS they receive through novel usage of information flow (IF). Hausman tests, fixed- and random-effects models confirmed a weak, though positive correlation between GS and R&D as determined by patent output (PO), but interestingly, observations of IF intimated that GS also affected other variables such as net profit (NP) and main business income (MBI). This suggests that firms are being awarded GS for higher PO, but a corresponding increase in R&D and its expected growth in company performance is not occurring. Thus, it is suggested that performance variables other than PO be used as firms may ab (use) this metric to apply for more GS, rather than performing R&D that leads to technological breakthroughs.

Mechanically Strong and Electrochemically Stable Single-Ion Conducting Polymer Electrolytes Constructed from Hydrogen Bonding

Herein, composite membranes based on a single-ion conducting polymer electrolyte (SIPE) and poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) were prepared by an electrospinning technology. The SIPE with hydrogen bonding was obtained via reversible addition-fragmentation chain transfer (RAFT) copolymerization of 2-(3-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl)ureido)ethyl methacrylate (UPyMA), poly(ethylene glycol) methyl ether methacrylate (PEGMA), and lithium 4-styrenesulfonyl (phenylsulfonyl) imide (SSPSILi). The obtained composite membrane exhibited a highly porous network structure, superior thermal stability (>300 °C), and high mechanical strength (17.3 MPa). The fabricated SIPE/PVDF-HFP composite membrane without lithium salts possessed a high ionic conductivity of 2.78 × 10^-5 S cm^-1 at 30 °C, excellent compatibility with the lithium metal electrode, and high lithium-ion transference number (0.89). The symmetric Li//Li cell exhibited a superior cycle performance without short circuit, indicating the generation of a stable interface between SIPE and the lithium metal electrode during the process of lithium plating/stripping, which could inhibit lithium dendrite growth in lithium metal batteries (LMBs). The Li//LiFePO₄ cell also exhibited superior cycle life and excellent rate capability at 60 or 25 °C. In consequence, the composite membrane exhibits a considerable future prospect for advanced LMBs.

Vacant Manganese-Based Perovskite Fluorides@Reduced Graphene Oxides for Na-Ion Storage with Pseudocapacitive Conversion/Insertion Dual Mechanisms

Na-ion capacitors (NICs) and Na-based dual-ion batteries (Na-DIBs) have been considered to be promising alternatives to traditional lithium-ion batteries (LIBs) because of the abundance and low cost of the Na-ion, but their energy density, power density and life cycle are limited. Herein, dual-vacancy (including K⁺ and F^- vacancies) perovskite fluoride K_0.86 MnF_2.69 @reduced graphene oxide (rGO; recorded as Mn-G) as anode for NICs and Na-DIBs has been developed. The special conversion/intercalation dual Na-ion energy storage mechanism and pseudocapacitive dynamics are analyzed in detail. The Mn-G//AC NICs and Mn-G//KS6 Na-DIBs delivered a maximum energy density of 92.7 and 187.6 W h kg^-1 , a maximum power density of 20.2 and 21.12 kW kg^-1 , and long cycle performance of 61.3 and 68.4 % after 1000 cycles at 5 A g^-1 , respectively. Moreover, Mn-G//AC NICs and Mn-G//KS6 Na-DIBs can work well over a wide range of temperatures (-20 to 40 °C). These results make it competitive in Na-ion storage applications with high energy/power density over a wide temperature range.

Dendrite-Suppressing Polymer Materials for Safe Rechargeable Metal Battery Applications: From the Electro-Chemo-Mechanical Viewpoint of Macromolecular Design

Metal batteries have been emerging as next-generation battery systems by virtue of ultrahigh theoretical specific capacities and low reduction potentials of metallic anodes. However, significant concerns regarding the uncontrolled metallic dendrite growth accompanied by safety hazards and short lifespan have impeded practical applications of metal batteries. Although a great deal of effort has been pursued to highlight the thermodynamic origin of dendrite growth and a variety of experimental methodologies for dendrite suppression, the roles of polymer materials in suppressing the dendrite growth have been underestimated. This review aims to give a state-of-the-art overview of contemporary dendrite-suppressing polymer materials from the electro-chemo-mechanical viewpoint of macromolecular design, including i) homogeneous distribution of metal ion flux, ii) mechanical blocking of metal dendrites, iii) tailoring polymer structures, and iv) modulating the physical configuration of polymer membranes. Judiciously tailoring electro-chemo-mechanical properties of polymer materials provides virtually unlimited opportunities to afford safe and high-performance metal battery systems by resolving problematic dendrite issues. Transforming these rational design strategies into building dendrite-suppressing polymer materials and exploiting them towards polymer electrolytes, separators, and coating materials hold the key to realizing safe, dendrite-free, and long-lasting metal battery systems.

A pre-oxidation strategy to improve architecture stability and electrochemical performance of Na2MnPO4F particles-embedded carbon nanofibers

The rational design of an excellent architecture for active materials combined with carbon matrix is of particular importanceto obtain flexible electrode material with high electrochemical properties. Well-designed nanofibers possess unique 3D network structure, which can significantly improve the electron/ion transportation and supplies sufficient active sites for Li⁺/Na⁺ insertion. Electrospinning-carbonization technology is a popular strategy to prepare nanofibers with active material embedded in carbon. It is found that the architecture of nanofibers tended to be wrecked and destroyed during the carbonization process without pre-oxidation treatment. In this study, we prepared Na₂MnPO₄F particles embedded in carbon nanofibers (Na₂MnPO₄F/C) using PVP as carbon source and investigated the strengthen mechanism of pre-oxidation on their architecture. The experiment and simulation results demonstrate that, without pre-oxidation, the main chain of PVP is severely ruptured during the carbonization procedure, consequently leads to fractured architecture of Na₂MnPO₄F/C nanofibers. In contrast, with pre-oxidation treatment, a long-chain and heat-resistance structured carbon matrix formed, and Na₂MnPO₄F/C nanofibers with stable architecture and improved electrochemical performance can be achieved. This study demonstrates a promising guide to construct carbon based nanofiber electrodes with stable architecture and high electrochemical performance.

Engineering the Active Sites of Graphene Catalyst: From CO2 Activation to Activate Li-CO2 Batteries

As one of the CO₂ capture and utilization technologies, Li-CO₂ batteries have attracted special interest in the application of carbon neutral. However, the design and fabrication of a low-cost high-efficiency cathode catalyst for reversible Li₂CO₃ formation and decomposition remains challenging. Here, guided by theoretical calculations, CO₂ was utilized to activate the catalytic activity of conventional nitrogen-doped graphene, in which pyridinic-N and pyrrolic-N have a high total content (72.65%) and have a high catalytic activity in both CO₂ reduction and evolution reactions, thus activating the reversible conversion of Li₂CO₃ formation and decomposition. As a result, the designed cathode has a low voltage gap of 2.13 V at 1200 mA g^-1 and long-life cycling stability with a small increase in the voltage gap of 0.12 V after 170 cycles at 500 mA g^-1. Our work suggests a way to design metal-free catalysts with high activity that can be used to activate the performance of Li-CO₂ batteries.

An AlCl3 coordinating interlayer spacing in microcrystalline graphite facilitates ultra-stable and high-performance sodium storage

Metal chloride-intercalated graphite intercalation compounds (MC-GICs) show a perfect sandwich structure with high electronic conductivity and chemical stability, but there are few applications for MC-GICs in anode materials of sodium ion batteries (SIBs). Herein, we selected a splendid host microcrystalline graphite (MG) to synthesize an AlCl3 intercalated MG intercalation compound (AlCl3-MGIC) anode material and demonstrated that it is suitable for SIBs via electrolyte optimization. The AlCl3-MGIC electrode is primarily compared in four electrolytes. Sodium storage is proposed for co-intercalation and conversion reactions by simultaneously selecting a compatible NaPF6/diethylene glycol dimethyl ether (DEGDME) electrolyte. As a result, the AlCl3-MGIC anode delivers a specific capacity of 202 mA h g-1 at a current density of 0.2 A g-1 after 100 cycles and still exhibits a satisfactory capacity of 198 mA h g-1 after 900 cycles. Density functional theory calculations further illustrate that DEGDME solvent molecules offer moderate adsorption energy to sodium ions that guarantees structure stabilization of GICs during repeated cycling. This work provides a theoretical basis for designing sodium ion storage with a graphite layered structure and unveiling the prospects of MC-GIC materials as high-performance anodes.

Direct recovery of degraded LiCoO2 cathode material from spent lithium-ion batteries: Efficient impurity removal toward practical applications

Regenerating cathode material from spent lithium-ion batteries (LIBs) permits an effective approach to resolve resource shortage and environmental pollution in the increasing battery industry. Directly renovating the spent cathode materials is a promising way, but it is still challenging to efficiently remove all of the complex impurities (such as binder, carbon black, graphite and current collectors) without destroying the material structure in the electrode. Herein, a facile strategy to directly remove these impurities and simultaneously repair the degraded LiCoO₂ by a target healing method is reported. Specifically, by using an optimized molten salt system of LiOH-KOH (molar ratio of 3:7) where LiNO₃ and O₂ both serve as oxidants, the impurities can be completely removed, while the structure, composition and morphology of degraded LiCoO₂ can be successfully repaired to commercial level based on a two-stage heating process (300 °C for 8 h and 500 °C for 16 h, respectively), resulting in a high recovery rate of approximately 100% for cathode material. More importantly, the regenerated LiCoO₂ exhibits a high reversible capacity, good cycling stability and excellent rate capability, which are comparable with commercial LiCoO₂. This work demonstrates an efficient approach to recycle and reuse advanced energy materials.

Natural Clay-Based Materials for Energy Storage and Conversion Applications

Among various energy storage and conversion materials, functionalized natural clays display significant potentials as electrodes, electrolytes, separators, and nanofillers in energy storage and conversion devices. Natural clays have porous structures, tunable specific surface areas, remarkable thermal and mechanical stabilities, abundant reserves, and cost-effectiveness. In addition, natural clays deliver the advantages of high ionic conductivity and hydrophilicity, which are beneficial properties for solid-state electrolytes. This review article provides an overview toward the recent advancements in natural clay-based energy materials. First, it comprehensively summarizes the structure, classification, and chemical modification methods of natural clays to make them suitable in energy storage and conversion devices. Then, the particular attention is focused on the application of clays in the fields of lithium-ion batteries, lithium-sulfur batteries, zinc-ion batteries, chloride-ion batteries, supercapacitors, solar cells, and fuel cells. Finally, the possible future research directions are provided for natural clays as energy materials. This review aims at facilitating the rapid developments of natural clay-based energy materials through a fruitful discussion from inorganic and materials chemistry aspects, and also promotes the broad sphere of clay-based materials for other utilization, such as effluent treatment, heavy metal removal, and environmental remediation.

The Electrolysis of Anti-Perovskite Li2 OHCl for Prelithiation of High-Energy-Density Batteries

Anti-perovskite type Li₂ OHCl was previously studied as a solid-state Li⁺ conductor. Here, we report that the Li₂ OHCl can be electrolyzed at 3.3 V or 4.0 V, with the creation of O₂ /HCl gases and the release of 2 equiv. Li⁺ via two different decomposition routes, depending on the acidity of electrolyte. In the electrolyte with trace acid, the Li₂ OHCl is oxidized at a constant voltage of 3.3 V. In neutral electrolyte, the oxidization of Li₂ OHCl starts at 4.0 V, but the produced HCl will increase the acidity of electrolyte and lead to a voltage drop to 3.3 V for the electrolysis of Li₂ OHCl. The electrolysis of Li₂ OHCl delivers a lithium releasing capacity as high as 810 mAh g^-1 , with an equivalent Li-deposition or Li-intercalation on anode, making it a promising candidate as a Li reservoir for prelithiation of anode. Using Li₂ OHCl as the lithium source, silicon-carbon (Si@C) composite anode can be effectively prelithiated. The full cells composed of LiNi_0.8 Mn_0.1 Co_0.1 O₂ (NMC811) cathode and prelithiated Si@C anode exhibited increased capacities with the increment of prelithiation dosages.

Dynamics of Emim+ in [Emim][TFSI]/LiTFSI Solutions as Bulk and under Confinement in a Quasi-liquid Solid Electrolyte

Quasi-liquid solid electrolytes are a promising alternative for next-generation Li batteries. These systems combine the safety of solid electrolytes with the desired properties of liquids and are typically formed by solutions of Li salts in ionic liquids incorporated into solid matrices. Here, we present a fundamental understanding of the transport properties in solutions of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][TFSI]), either in bulk form or incorporated in a boron nitride (BN) matrix. We performed a series of quasi-elastic neutron scattering experiments that, given the high incoherent neutron scattering cross section of hydrogen, allowed us to focus on the Emim⁺ dynamics. First, [Emim][TFSI]/LiTFSI solutions (0.5 and 2.5 mol·kg^-1) were investigated and we show how the increase in the concentration reduces the Emim⁺ mobility and increases the activation energy of their long-range motions. Then, the 0.5 mol·kg^-1 solution was incorporated into the BN matrix and we report that the diffusivities of the Emim⁺ cations that remain mobile under confinement are highly accelerated in comparison with the bulk sample and the activation energy of these motions is drastically reduced. We present the experimental evidence that this effect is related to the content of the Emim⁺ cations immobilized near the surfaces of the BN pores.

Al-Storage Behaviors of Expanded Graphite as High-Rate and Long-Life Cathode Materials for Rechargeable Aluminum Batteries

The rational design and synthesis of capable cathode materials with low cost that can exhibit good electrochemical performance are key to the development of rechargeable aluminum batteries (RABs). In this article, we have developed low-cost expanded graphite as typical cathode materials for high-performance RABs in pouch cells. Remarkably, the commercial expanded graphite can show high-rate performance, long-term cyclic life, and high energy density (64 Wh kg^-1 based on a whole pouch cell). In particular, it delivers a high capacity of 111 mAh g^-1 at a current density of 2 A g^-1 after 300 cycles and 61.1 mAh g^-1 at a high current density of 50 A g^-1 after 10 000 cycles. The high-rate performance is derived from the rapid kinetic enhancement caused by the chemisorption-involved-intercalation pseudocapacitance effect. Further, a series of facile electrochemical means are used to confirm the intercalation (1.5-2.4 V)-adsorption mechanism (0.5-1.5 V) of expanded graphite. This work can provide significant support for further understanding the Al-storage behaviors of graphite materials in RABs.

Enhanced energy storage of aqueous zinc-carbon hybrid supercapacitors via employing alkaline medium and B, N dual doped carbon cathode

Zinc-based energy storage systems (zinc-air, zinc-nickel and zinc-ion batteries and zinc-ion hybrid supercapacitors (ZHSs) are considered as promising power sources for wide applications from personal electronic devices to electric vehicles. However, these systems, especially the Zn-based hybrid supercapacitors, display unsatisfying power density and energy density, which should be enhanced for their large-scale applications. In this work, aqueous alkaline zinc-carbon hybrid supercapacitors (A-ZCHS) were designed, consisting of B, N dual doped carbon cathode, Zn anode and KOH electrolyte. The B, N dual doped carbon was prepared via thermal treatment of metal-organic frameworks and boric acid, which exhibits abundant hierarchical pore structure (micropore, mesopore and macropore) and suitable defect construction, promoting ion diffusion/charge transfer and providing more rapid surface pseudocapacitance reaction. More obviously, when the optimized B, N dual doped carbon was used as cathode in A-ZCHS and ZHS, more capacitive charge storage and rapider electrochemical kinetics can be observed in A-ZCHS than in ZHS. Therefore, the optimized A-ZCHS displays a high energy density of 115.7 Wh kg^-1 at the power density of 711.6 W kg^-1 with excellent stability, which is much better than most of ZHSs reported previously. The A-ZCHS should be a promising candidate for energy storage applications.

Benzoic Anhydride as a Bifunctional Electrolyte Additive for Hydrogen Fluoride Capture and Robust Film Construction over High-Voltage Li-Ion Batteries

High-voltage LiNi_0.8 Co_0.1 Mn_0.1 O₂ (NCM811)-based Li-ion batteries (LIBs) with enhanced performance can be achieved by properly tailoring the electrolyte systems. Benzoic anhydride (BA) was proposed here as a promising bifunctional electrolyte additive that can not only construct a robust cathode-electrolyte interface (CEI) film on the electrode surface but also capture HF/H₂ O in the electrolyte effectively. Compared to the cell without the BA additive, the capacity of Li/NCM811 half-cell with 1.0 wt % BA was increased from 128.5 to 149.6 mAh g^-1 after 200 cycles at 1 C between 3.0 and 4.3 V. Even at a higher cut-off voltage of 4.5 V, the BA-containing Li/NCM811 half-cell delivered a capacity retention of 69 % after 200 cycles, much higher than that of the half-cell without the additive (56 %). Both theoretical calculation and experimental results verified that the BA additive could be preferentially oxidized to form a stable interface film with high conductivity that protected the NCM811 cathode and suppressed the decomposition of the electrolyte.

Architectural Engineering Achieves High-Performance Alloying Anodes for Lithium and Sodium Ion Batteries

Tremendous efforts have been dedicated to the development of high-performance electrochemical energy storage devices. The development of lithium- and sodium-ion batteries (LIBs and SIBs) with high energy densities is urgently needed to meet the growing demands for portable electronic devices, electric vehicles, and large-scale smart grids. Anode materials with high theoretical capacities that are based on alloying storage mechanisms are at the forefront of research geared towards high-energy-density LIBs or SIBs. However, they often suffer from severe pulverization and rapid capacity decay due to their huge volume change upon cycling. So far, a wide variety of advanced materials and electrode structures are developed to improve the long-term cyclability of alloying-type materials. This review provides fundamentals of anti-pulverization and cutting-edge concepts that aim to achieve high-performance alloying anodes for LIBs/SIBs from the viewpoint of architectural engineering. The recent progress on the effective strategies of nanostructuring, incorporation of carbon, intermetallics design, and binder engineering is systematically summarized. After that, the relationship between architectural design and electrochemical performance as well as the related charge-storage mechanisms is discussed. Finally, challenges and perspectives of alloying-type anode materials for further development in LIB/SIB applications are proposed.