Full Cell Performance Research Articles

Degradation Mechanisms of Positive Electrode Materials for Sodium-Ion Batteries

Sodium-ion batteries (SIB) require less critical materials and lead to a significant cost reduction compared to state-of-the-art lithium-ion batteries [1]. Although a large-scale commercialization of SIBs is within reach [2], the understanding of the degradation mechanisms of these batteries is still incomplete. The larger ionic radius of sodium in comparison to that of lithium can induce larger stress changes in the host material causing poor long-term stability. Minimizing degradation of positive electrode materials is of high importance for the advancement of SIB technology. Here, we report on degradation of the important structure types: layered oxides, polyanionic compounds, and Prussian blue analogues. Our results show that the polyanionic Na3V2(PO4)3 is a highly reliable cathode material, which can be used as a benchmark or reference material.During battery operation, mechanical stresses are caused by volume changes of the active materials, when sodium ions are inserted or extracted into/from them. We use operando methods such as the substrate curvature technique to measure stresses in the electrode and draw conclusions about electrochemical and physical processes in the materials during cycling [3]. To investigate phenomena like volume changes, crack formation and overall morphology, ex situ scanning electron microscopy (SEM) is used intermittently. Here, we compare the same site on the electrode in different states of charge and for different cycle numbers. Additionally, X-ray diffraction (XRD) measurements are conducted to study phase transitions.Na2/3Fe1/3Mn2/3O2 is a layered P2-type oxide that offers a high specific capacity and is composed of abundant elements. Due to its intrinsic sodium deficiency, diverse presodiation methods become important [4]. We investigate Na2C4O4 as sacrificial salt and its effects on electrode morphology during decomposition. Our goal is to understand the resulting reaction pathways and optimize the full cell performance of layered oxides.Sodium hexacyanoferrate NaxFe[Fe(CN)6] is a Prussian blue analogue and one of the most prominent candidates for commercial SIBs [2]. It also offers high specific capacities and a long cycle life, but its high moisture sensitivity and interstitial water demand appropriate electrode drying procedures to avoid side reactions during cell operation. Crack formation and growth were studied with SEM after and during cycling. Phase transitions are observed by operando XRD and operando substrate curvature measurements.Sodium vanadium phosphate Na3V2(PO4)3 (NVP) with its highly stable three-dimensional network of a NASICON-type structure and its large diffusion channels for sodium ions is another promising electrode material that deserves attention. NVP can be sodiated and desodiated at two different voltage plateaus and therefore can serve either as cathode or anode material. SEM observations at different states of charge show how preexisting cracks open/close during desodiation/sodiation due to volume shrinkage/expansion. We compare symmetric NVP−NVP cells to full cells with NVP cathodes and anodes of Na metal, hard carbon, Sb/C, and SnSb/C. Our data suggests that problems of Na and Na-ion cells frequently result from the anode. NVP itself is extremely reliable and balanced symmetric NVP−NVP cells exhibit very high cycling stability. More than one thousand cycles can be easily achieved. Due to its distinct plateaus and high stability, we suggest NVP as a reference material for cathode and anode materials. For example, NVP can serve as a reliable anode material for testing the stability of different cathode materials. NVP as a cathode may be used to test anode materials or as a benchmark for other cathode materials [5].Acknowledgements:This work contributes to the research performed at CELEST (Center for Electrochemical Energy Storage Ulm-Karlsruhe) and was funded by the German Research Foundation (DFG) under Project ID 390874152 (POLiS Cluster of Excellence, EXC 2154).Literature:[1] C. Vaalma et al., Nature Reviews Materials 2018, 3, 4, 1-11.[2] M. A. Sawhney et al., ChemPhysChem 2022, 23, 5, 1-19.[3] Z. Choi et al., Journal of Power Sources 2013, 240, 245-251.[4] J. M. De Ilarduya et al. Electrochimica Acta 2019, 321, 134693.[5] T. Akçay et al., ACS Applied Energy Materials 2021, 4, 11, 12688-12695.

Oxygen Defect Engineering toward Zero-Strain V2O2.8@Porous Reticular Carbon for Ultrastable Potassium Storage.

Potassium-ion batteries (KIBs) are promising candidates for large-scale energy storage devices due to their high energy density and low cost. However, the large potassium-ion radius leads to its sluggish diffusion kinetics during intercalation into the lattice of the electrode material, resulting in electrode pulverization and poor cycle stability. Herein, vanadium trioxide anodes with different oxygen vacancy concentrations (V2O2.9, V2O2.8, and V2O2.7 determined by the neutron diffraction) are developed for KIBs. The V2O2.8 anode is optimal and exhibits excellent potassium storage performance due to the realization of expanded interlayer spacing and efficient ion/electron transport. In situ X-ray diffraction indicates that V2O2.8 is a zero-strain anode with a volumetric strain of 0.28% during the charge/discharge process. Density functional theory calculations show that the impacts of oxygen defects are embodied in reducing the band gap, increasing electron transfer ability, and lowering the diffusion energy barriers for potassium ions. As a result, the electrode of nanosized V2O2.8 embedded in porous reticular carbon (V2O2.8@PRC) delivers high reversible capacity (362 mAh g-1 at 0.05 A g-1), ultralong cycling stability (98.8% capacity retention after 3000 cycles at 2 A g-1), and superior pouch-type full-cell performance (221 mAh g-1 at 0.05 A g-1). This work presents an oxygen defect engineering strategy for ultrastable KIBs.

Curtailing the thermal runaway and ameliorating interfacial charge kinetics using electrolyte-cum-separator in Li-battery

Recently, absolute requirements for high-performing energy storage devices with high thermal stability and superior safety features keep motivating to replace conventional liquid electrolyte systems with lithium-based secondary batteries. Instead, incorporating the solid-state electrolytes can be an elegant strategy; however, the solid electrolyte's poor interfacial kinetics and brutal ceramic nature are the significant hitches for commercial battery manufacturing. Considering these critical issues, an electrolyte cum separator (ECSP) membrane composed of robust polymer and high ion-conducting ceramic has been rationally designed to improve interfacial ion kinetics during electrochemical cycling. The electrolyte-cum-separator (ECSP) attains high thermal endurance (150 °C), superior mechanical strength, and excellent wettability to commercially available systems. Further, the ECSP ensures low interfacial resistance against the Li metal even at a high current density, that let to prevent the dendritic growth and short-circuiting of the battery. The ECSP membrane-enabled batteries demonstrate excellent discharge capacity with high potential cathode and metal anodes that outperform those batteries assembled from commercial electrolyte and separator systems. Moreover, the thermal stability of the ECSP membrane using the accelerating rate calorimeter (ARC) has also been investigated. The excess flammable solvent and lower thermal endurance of the commercial electrolyte separator system are responsible for the batteries' thermal runaway. Additionally, the full-cell performance composed of a commercial cathode (Li(NixCoxMnx)O2, x =1/3), anode (MCMB), and the ECSP membrane manifests good cycle life and stable capacity retention. Therefore, the fabrication of electrolyte-cum-separator is a prominent strategy to achieve flexible, dendrite-free, and high-performing solid-state Li metal as well as Li-ion battery technologies for high-end applications.

High-throughput and high-performance lithium-ion batteries via dry processing

A scalable powder-to-electrode dry processing strategy mainly based on powder dry mixing and rolling/calendering is rationally designed. The dry processed electrodes show lower tortuosity compared to that of conventional slurry-based electrodes. The dry-processed high-loading graphite anodes (6.6 mAh cm−2) and LiNi0.6Mn0.2Co0.2O2 cathodes (6.0 mAh cm−2) exhibit promising electrochemical performance in half-cells and full-cells. The full-cells with both electrodes from dry processing demonstrates superb rate performance to their counterpart with conventional slurry-based electrodes and delivers of capacity retentions of 74.1 % and 63.6 % over 400 and 800 cycles, respectively. Notably, the initial Coulombic efficiency of the dry processed graphite anodes is low ascribed to polytetrafluoroethylene binder. The results suggest that dry processing is promising for future lithium-ion battery manufacturing and also pinpoint the needs of modification for the polytetrafluoroethylene binder in the graphite anodes.

High-Entropy Na-Deficient Layered Oxides for Sodium-Ion Batteries.

Sodium layered oxides always suffer from sluggish kinetics and deleterious phase transformations at deep-desodiation state (i.e., >4.0 V) in O3 structure, incurring inferior rate capability and grievous capacity degradation. To tackle these handicaps, here, a configurational entropy tuning protocol through manipulating the stoichiometric ratios of inactive cations is proposed to elaborately design Na-deficient, O3-type NaxTmO2 cathodes. It is found that the electrons surrounding the oxygen of the TmO6 octahedron are rearranged by the introduction of MnO6 and TiO6 octahedra in Na-deficient O3-type Na0.83Li0.1Ni0.25Co0.2Mn0.15Ti0.15Sn0.15O2-δ (MTS15) with expanded O-Na-O slab spacing, giving enhanced Na+ diffusion kinetics and structural stability, as disclosed by theoretical calculations and electrochemical measurements. Concomitantly, the entropy effect contributes to the improved reversibility of Co redox and phase-transition behaviors between O3 and P3, as clearly revealed by ex situ synchrotron X-ray absorption spectra and in situ X-ray diffraction. Notably, the prepared entropy-tuned MTS15 cathode exhibits impressive rate capability (76.7% capacity retention at 10 C), cycling stability (87.2% capacity retention after 200 cycles) with a reversible capacity of 109.4 mAh g-1, good full-cell performance (84.3% capacity retention after 100 cycles), and exceptional air stability. This work provides an idea for how to design high-entropy sodium layered oxides for high-power density storage systems.

LiF-Rich Interfacial Protective Layer Enables Air-Stable Lithium Metal Anodes for Dendrite-Free Lithium Metal Batteries.

Lithium (Li) metal is considered as a promising anode candidate for high-energy-density batteries. However, the high reactivity of Li metal leads to poor air stability, limiting its practical application. Additionally, the interfacial instability, such as dendrite growth and an unstable solid electrolyte interphase layer, further complicates its utilization. Herein, a dense lithium fluoride (LiF)-rich interfacial protective layer is constructed on the Li surface through a simple reaction between Li and fluoroethylene carbonate (denoted as LiF@Li). The LiF-rich interfacial protective layer consists of both organic (ROCO2Li and C-F-containing species, which only exist on the outer layer) and inorganic (LiF and Li2CO3, distribute throughout the layer) components with a thickness of ∼120 nm. Specifically, chemically stable LiF and Li2CO3 play an important role in blocking air and hence improve the air durability of LiF@Li anodes. Notably, LiF with high Li+ diffusivity facilitates uniform Li+ deposition, while organic components with high flexibility relieve volume change upon cycling, thereby enhancing the dendrite inhibition capacity of LiF@Li. Consequently, LiF@Li exhibits remarkable stability and excellent electrochemical performance in both symmetric cells and LiFePO4 full cells. Moreover, LiF@Li maintains its initial color and morphology even after air exposure for 30 min, and the air-exposed LiF@Li anode still retains its superior electrochemical performance, further establishing its outstanding air-defendable capability. This work proposes a facile approach in constructing air-stable and dendrite-free Li metal anodes toward reliable Li metal batteries.

Stabilizing the surface of Li2NiO2 cathode additive by coating amorphous niobium oxy-carbide for lithium-ion batteries

The formation of solid electrolyte interphase at the first cycle has raised technical issues of capacity loss in anode materials for lithium-ion batteries. As one solution, using Li-excess Li2NiO2 as a cathode additive aims to compensate for the initial Li+ consumption by anode materials using some of the high irreversible capacity. However, Li2NiO2 is insufficient for satisfying atmospheric stability, which induces spontaneous side reactions (e.g. Li2CO3 and LiOH), resulting in an increase of interfacial resistance for Li+ migration. In addition, the small but significant evolution of oxygen (O2) gas during the charge process over 3.8 V vs. Li/Li+ brings an extra caution for safety concerns. There is no doubt that structural stabilization of Li2NiO2 is a prerequisite for practical use in lithium-ion batteries. In this study, we propose a surface coating of amorphous niobium oxycarbide (NbOxCy) onto Li2NiO2 particles to improve their atmospheric stability, together with suppression of O2 gas evolution. Owing to its distinctive physicochemical properties, NbOxCy is beneficial for enhancing vulnerability to moisture as well as scavenging any residual O2 gas. In practice, the adoption of NbOxCy-coated Li2NiO2 improved electrochemical performance in full cells and was verified as a strategic solution to two fundamental challenges.

Boron-Doping Induced Electron Delocalization in Fluorophosphate Cathode: Enhanced Na-Ion Diffusivity and Sodium-Ion Full Cell Performance.

Na3 V2 (PO4 )2 O2 F (NVPOF) is widely accepted as advanced cathode material for sodium-ion batteries with high application prospects ascribing to its considerable specific capacity and high working voltage. However, challenges in the full realization of its theoretical potential lie in the novel structural design to accelerate its Na+ diffusivity. Herein, considering the important role of polyanion groups in constituting Na+ diffusion tunnels, boron (B) is doped at the P-site to obtain Na3 V2 (P2- x Bx O8 )O2 F (NVP2- x Bx OF). As evidenced by density functional theory modeling, B-doping induces a dramatic decrease in the bandgap. Delocalization of electrons on the O anions in BO4 tetrahedra is observed in NVP2- x Bx OF, which dramatically lowers the electrostatic resistance experienced by Na+ . As a result, the Na+ diffusivity in the NVP2- x Bx OF cathode has accelerated up to 11 times higher, which secures a high rate property (67.2mAhg-1 at 60 C) and long cycle stability (95.9% capacity retention at 108.6mAhg-1 at 10C after 1000 cycles). The assembled NVP1.90 B0.10 OF//Se-C full cell demonstrates exceptional power/energy density (213.3Wkg-1 @ 426.4Whkg-1 and 17970W kg-1 @ 119.8Whkg-1 ) and outstanding capability to withstand long cycles (90.1% capacity retention after 1000 cycles at 105.3mAhg-1 at 10 C).

FeN Coordination Induced Ultralong Lifetime of Sodium-Ion Battery with the Cycle Number Exceeding 65 000.

Sodium-ion batteries (SIBs) have received increasing attention because of their appealing cell voltages and cost-effective features. However, the atom aggregation and electrode volume variation inevitably deteriorate the sodium storage kinetics. Here a new strategy is proposed to boost the lifetime of SIB by synthesizing sea urchin-like FeSe2 /nitrogen-doped carbon (FeSe2 /NC) composites. The robust FeN coordination hinders the Fe atom aggregation and accommodates the volume expansion, while the unique biomorphic morphology and high conductivity of FeSe2 /NC enhance the intercalation/deintercalation kinetics and shorten the ion/electron diffusion length. As expected, FeSe2 /NC electrodes deliver excellent half (387.6mAhg-1 at 20.0 A g-1 after 56 000 cycles) and full (203.5 mAh g-1 at 1.0 A g-1 after 1200 cycles) cell performances. Impressively, an ultralong lifetime of SIB composed of FeSe2 /Fe3 Se4 /NC anode is uncovered with the cycle number exceeding 65 000. The sodium storage mechanism is clarified with the aid of density function theory calculations and in situ characterizations. This work hereby provides a new paradigm for enhancing the lifetime of SIB by constructing a unique coordination environment between active material and framework.

Synergetic optimization of p-type Ba2+ substitution and carbon nanotubes enwrapping in Na3V2(PO4)3: A superior cathode with high electrochemical and safety performance for half and full cells

Na3V2(PO4)3 (NVP) has been deemed as a promising cathode because of high capacity and good stability. Nevertheless, poor intrinsic conductivity seriously limits its further application. Herein, partial Ba2+ substitution on V3+ site is introduced to modify NVP in terms of increasing cell volume due to larger ionic radius of Ba2+ and generating beneficial hole carriers derived from p-type doping. The expanded crystal channels efficiently facilitate the Na + migration and the hole carriers are beneficial for transfer charge to improve electronic conductivity. Ba2+ doping further enhances the structural stability due to the pillar effect, which has been proved by DSC measurement. The increase of exothermic peak temperature and decrease of heat release rate demonstrates the excellent thermal stability of NVBa0.07P@CNTs. Moreover, disordered carbon layer and enwrapped CNTs construct an effective network to provide abundant routes for electronic transportation. Notably, the optimized NVBa0.07P@CNTs delivers superior electrochemical performance in both half and full cells. It releases a capacity of 117.23 mA h g−1 at 0.1C and submits a capacity of 101.99 mA h g−1 with retention of 80% at 15 C over 2000 cycles. Even at 50 C, it still delivers a high value of 78.33 mA h g−1.

Three-dimensionally multiple protected silicon anode toward ultrahigh areal capacity and stability

Silicon (Si) is considered as one of the most promising candidates for next-generation lithium-ion battery (LIB) anode due to its high theoretical capacity. However, the drastic volume change of Si anodes during lithiation/delithiation processes leads to rapid capacity fade. Herein, a three-dimensional Si anode with multiple protection strategy is proposed, including citric acid-modification of Si particles (CA@Si), GaInSn ternary liquid metal (LM) addition, and porous copper foam (CF) based electrode. The CA modified supports strong adhesive attraction of Si particles with binder and LM penetration maintains good electrical contact of the composite. The CF substrate constructs a stable hierarchical conductive framework, which could accommodate the volume expansion to retain integrity of the electrode during cycling. As a result, the obtained Si composite anode (CF-LM-CA@Si) demonstrates a discharge capacity of 3.14 mAh cm−2 after 100 cycles at 0.4 A g−1, corresponding to 76.1% capacity retention rate based on the initial discharge capacity and delivers comparable performance in full cells. The present study provides an applicable prototype of high-energy density electrodes for LIBs.

Hybrid Dynamic Covalent Network as a Protective Layer and Solid-State Electrolyte for Stable Lithium-Metal Batteries.

Lithium (Li) metal is a highly promising anode material for next-generation high-energy-density batteries, while Li dendrite growth and the unstable solid electrolyte interphase layer inhibit its commercialization. Herein, a chemically grafted hybrid dynamic network (CHDN) is rationally designed and synthesized by the 4,4'-thiobisbenzenamine cross-linked poly(poly(ethylene glycol) methyl ether methacrylate-r-glycidyl methacrylate) and (3-glycidyloxypropyl) trimethoxysilane-functionalized SiO2 nanoparticles, which is utilized as a protective layer and hybrid solid-state electrolyte (HSE) for stable Li-metal batteries. The presence of a dynamic exchangeable disulfide affords self-heability and recyclability, and the chemical attachment between SiO2 nanoparticles and the polymer matrix enables the homogeneous distribution of inorganic fillers and mechanical robustness. With integrated flexibility, fast segmental dynamics, and autonomous adaptability, the as-prepared CHDN-based protective layer enables superior electrochemical performance in half cells and full cells (capacity retention of 83.7% over 400 cycles for the CHDN@Li/LiFePO4 cell at 1 C). Furthermore, benefiting from intimate electrode/electrolyte interfacial contact, CHDN-based solid-state cells deliver excellent electrochemical performance (capacity retention of 89.5% over 500 cycles for the Li/HSE/LiFePO4 cell at 0.5 C). In addition, the Li/HSE/LiFePO4 pouch cell exhibits superior safety, even exposing various physical damage conditions. This work thereby provides a fresh insight into a rational design principle for dynamic network-based protective layers and solid-state electrolytes for battery applications.

Highly Stable Potassium Metal Anodes with Controllable Thickness and Area Capacity.

K metal battery is a kind of high-energy-density storage device with economic advantages. However, due to the dendrite growth and difficult processing characteristics, it is difficult to prepare stable K metal anode with thin thickness and fixed area capacity, which severely limits its development. In this work, a multi-functional 3D skeleton (rGCA) is synthesized by simple vacuum filtration and thermal reduction, and K metal anodes with controllable thickness and area capacity (K content) can be fabricated by changing the raw material mass and graphene layer spacing of rGCA. Moreover, the graphene sheet layer of rGCA can relax stress and relieve volume expansion; carbon nanotubes can serve as the fast transport channel of electrons, reducing internal impedance and local current density; Ag nanoparticles can induce the uniform nucleation and deposition of K+ . The K metal composite anodes (rGCA-K) based on the conductive skeleton can effectively suppress dendrites and exhibit excellent electrochemical performance in symmetric and full cells. The controllable fabrication process of stable K metal anode is expected to help K metal batteries move toward the stage of commercial production.

Multifunctional fullerene protective layer for dendrite-free Zn metal anode

Although the aqueous zinc batteries are deemed as the most competitive alternatives in the next-generation batteries, there are still annoying issues, including obdurate dendrites formation and side reactions, limiting practical applications. Hence, a uniform artificial C60 layer via an ex-situ approach is successfully assembled to construct robust Zn anode (denoted as Zn@C60). The functional C60 layer allows the formation of the ohmic contact interface between the C60 layer and Zn anode, inducing a low nucleation barrier and restraining 2D diffusion of Zn ions. More importantly, density functional theory calculations and simulation of the electric field contribution demonstrate that the C60 layer can facilitate the deposition of Zn on the Zn(002) plane and homogenize the electric field distribution. Consequently, the Zn@C60 electrode is obtained with a cycling stability over 3800 h at 0.25 mA cm−2 in symmetric cells, excellent coulombic efficiency for 1400 h in half cells, and together with better cycling stability and enhanced rate performance in full cells. Significantly, the C60 layer protection strategy provides a new view for an excellent dendrite-free Zn metal anode.

Ultra‐High Capacity and Cyclability of β‐phase Ca0.14V2O5as a Promising Cathode in Calcium‐Ion Batteries

AbstractCrystalline water‐free β‐phase Ca0.14V2O5is reported for the first time as a viable cathode material for calcium‐ion batteries (CIBs). In contrast to layered α‐V2O5and δ‐CaxV2O5·nH2O, which have limited capacity, the β‐phase delivers a reversible capacity of ≈247 mAh g−1, which corresponds to the insertion/extraction of Ca2+between Ca0.14V2O5and Ca1.0V2O5. The process of Ca2+insertion process and the accompanying structural relaxation are theoretically and experimentally verified. The initial insertion of Ca2+into Ca0.14V2O5causes a slight shift of oxygen atoms surrounding hepta‐coordination sites, creating penta‐coordinated sites that are then partially filled up to Ca0.33V2O5. Further insertion occurs through the stepwise occupation of up to 50% of neighboring hexa‐ and tetra‐coordination sites to form Ca0.67V2O5and Ca1.0V2O5, respectively. The rearrangement of oxygen atoms in Ca0.14V2O5also minimizes dimensional changes, leading to high cyclic stability during repeated charge/discharge cycles. The remarkable electrochemical performance of full cells containing a Ca0.14V2O5cathode and a K metal anode in Ca2+/K+hybrid electrolytes, is also demonstrated, thanks to the inertness of K+insertion into Ca0.14V2O5and the absence of calcium plating/stripping. The cyclic stability and high capacity of Ca0.14V2O5is not compromised in hybrid electrolytes, making it a viable CIB cathode.

Multi-interfacial dendritic engineering facilitating congruous intrinsic activity of oxide-carbide/MOF nanostructured multimodal electrocatalyst for hydrogen and oxygen electrocatalysis

Multiple interfaces and phases between the electrode and electrolyte play a key role in prompting the overall electrocatalysis, due to the high chances of the formation and cleavage of chemical bonds. Here, we employed the most common tactic of coupling functional components into a hybrid heterostructure with improved synergistic effects between organic and inorganics. The functional metal nodes-organic bridge ligands integrated on polyvalent tungsten oxide–carbide interfaces with highly-porous nano-dendritic architectonic is developed. The FeCu–BTC/WO3–WC showed excellent electrochemical half-cell (HER/OER/ORR), and Full-cell (aqueous ZAB and water electrolysis) performances with Ε1/2, ORR = 0.81 V, η10, OER = 249 mV, η10, HER = 99 mV, Ε10, water splitting = 1.531 V, and PDZAB = 135.2 mW cm−2 with profound durability. Hence, the multi-interfacial dendritic FeCu–BTC/WO3–WC ternary nanocomposite offers the prospect of a good harbinger for aggressive reform of energy technologies towards the zero-emission energy goal.

Electronic interconnected CoV2O6 to induce boosted reaction kinetics for highly stable sodium-ion half/full batteries

It is one of the most common methods to improve the performance of sodium-ion batteries (SIBs) by improving the anodes. Vanadium metal oxides, including cobalt vanadate, are potential substitute as new anode material for SIBs due to their high theoretical capacity, variable crystal structure, synergistic effect and interfacial effect between multiple metals. However, although the specific capacity of such anode material is high, the irreversible capacity is often caused by the phase transition process in the charging and discharging process, which leads to a large amount of capacity attenuation. In addition, poor conductivity also limits the rate performance. In this work, bimetallic CoV2O6 (CVO) nanoparticles were modified by using two-dimensional (2D) reduced graphene oxide (rGO) with facile hydrothermal and heat treatment method. Via this construction, the CVO-rGO owns the advantage of porous electronic interconnected network structure, favoring the Na ions/electrons transportation, and suppressing the phase transition during Na+ (de)insertion. Benefiting from the built structure of CVO-rGO, it exhibits excellent performance in SIBs half and full cells. Specifically, CVO-rGO delivers stable 980 mAh g−1 at 0.1 A g−1 after 500 cycles and 98% capacity retention after 1000 cycles at 1 A g−1. Moreover, as anode in SIBs pouch cell, 84.7 mAh g−1 at 2 A g−1 after 1000 cycles (specific capacity retention: 90.3%) can be achieved. Such superior sodium storage of CVO-rGO is confirmed by reaction kinetics analysis and ex-situ XPS/Raman characterization. This work provides a reference for cobalt vanadium oxide to be used as anode material for high performance SIBs.

Room-Temperature Rapid Self-Healing Polymer Binders for Si Anodes in Highly Cycling-Stable and Capacity-Maintained Lithium-Ion Batteries

Silicon (Si) with high specific capacity has received increasing attention for rechargeable battery anode materials. However, particle pulverization as a result of the large volume expansion of Si anodes further aggravated electrochemical performance degradation during the process of charging and discharging. In this work, we report the room-temperature rapid self-healing polymer binders (Al/Alg-TUEG) synthesized via dynamic coordination bonds (Al–O) and hydrogen bonds from poly(ether-thioureas) (TUEG). The prepared polymer binders exhibit a peeling force of 4.2 N, a swelling ratio of 9.5%, and a recovery of 90% in 2 h at room temperature. As a result, the Si@Al/Alg-TUEG anodes stably cycle for 300 cycles at 0.5 C with a capacity retention rate of 77.4%. A high initial Coulombic efficiency (CE) of 87.2% and good rate performance are also achieved. In terms of full cell performance, both LiFePO4//Si@Al/Alg-TUEG and NCM811//Si@Al/Alg-TUEG display stable cycling for 100 cycles at 0.5 C. The capacity retention of both full cells reaches 93.8 and 92.5%. Good recoverability at high rates is also found. The superior electrochemical performance of the Si anode indicates that Al/Alg-TUEG polymer with rapid self-healing capability at room-temperature is one of the promising binder candidates for next-generation high-energy-density lithium-ion batteries.

Bi-Morphological Form of SiO2 on a Separator for Modulating Li-Ion Solvation and Self-Scavenging of Li Dendrites in Li Metal Batteries.

The lithium (Li) metal anode is highly desirable for high-energy density batteries. During prolonged Li plating-stripping, however, dendritic Li formation and growth are probabilistically high, allowing physical contact between the two electrodes, which results in a cell short-circuit. Engineering the separator is a promising and facile way to suppress dendritic growth. When a conventional coating approach is applied, it usually sacrifices the bare separator structure and severely increases the thickness, ultimately decreasing the volumetric density. Herein, we introduce dielectric silicon oxide with the feature of bi-morphological form, i.e., backbone-covered and backbone-anchored, onto the conventional polyethylene separator without any volumetric change. These functionally vary the Li+ transference number and the ionic conductivity so as to modulate Li-ion solvation and self-scavenging of Li dendrites. The proposed separator paves the way to maximizing the full cell performance of Li/NCM622 toward practical application.

Chitosan as Enabling Polymeric Binder Material for Silicon‐Graphite‐Based Anodes in Lithium‐Ion Batteries

Massive volume change during (de‐)lithiation and subsequent challenges, such as pulverization of active materials, delamination of electrode from the current collector, and fragile solid electrolyte interphase, are among the main impediments hindering the large‐scale commercialization of silicon‐containing anode materials in lithium‐ion batteries. In this regard, designer polymeric binders with unique chemistries are considered as enabling solutions. Polymeric materials endowed with functional groups such as –OH, –COOH/COO−, and –NH2/NH3+, capable of building strong H bonds, are hailed as effective binders for Si‐containing anode materials. Herein, chitosan biopolymers are investigated as a green and environmentally friendly binder in a silicon/graphite (Si/Gr) anode and compared to lithium poly(acrylic acid)/sodium carboxymethyl cellulose binders. The effect of degree of acetylation (DA) and degree of polymerization of chitosan on the electrochemical performance of Si/Gr anode‐based cells is investigated. Anodes with chitosan binder with DA of 50% show the most promising electrochemical performance in Si/Gr||lithium metal and lithium nickel manganese cobalt oxide (NMC622)||Si/Gr cells. Crosslinking of chitosan binder with citric acid monohydrate in combination with free‐standing electrodes results in improved electrochemical performance in full cells. The surface chemistry of electrochemically cycled Si/Gr anodes with/without chitosan binder is investigated by X‐ray photoelectron spectroscopy.