Minimizing Undesired Side Reactions Induced by Nanoscale Conductive Carbon Enables Stable Cycling of Semi-Solid Li-Ion Full Batteries.

Semi-solid lithium-ion batteries (SSLIBs) based on "slurry-like" electrodes hold great promise to enable low-cost and sustainable energy storage. However, the development of the SSLIBs has long been hindered by the lack of high-performance anodes. Here the origin of low initial Coulombic efficiency (iCE, typically <60%) is elucidated in the graphite-based semi-solid anodes (in the non-flowing mode) and develop rational strategies to minimize the irreversible capacity loss. It is discovered that Ketjen black (KB), a nanoscale conductive additive widely used in SSLIB research, induces severe electrolyte decomposition during battery charge due to its large surface area and abundant surface defects. High iCEs up to 92% are achieved for the semi-solid graphite anodes by replacing KB with other low surface-area, low-defect conductive additives. A semi-solid full battery (LiFePO4 vs graphite, in the non-flowing mode) is further demonstrated with stable cycle performance over 100 cycles at a large areal capacity of 6 mAh cm-2 and a pouch-type semi-solid full cell that remains functional even when it is mechanically abused. This work demystifies the SSLIBs and provides useful physical insights to further improve their performance and durability.

High-entropy selenides derived from Prussian blue analogues as electrode materials for sodium-ion batteries.

Transition metal selenides (TMS) have received much attention as anode materials for sodium-ion batteries (SIBs) because of their high theoretical capacity and excellent redox reversibility. However, their further development is constrained by the dissolution of transition metal ions and substantial volume changes experienced during cycling. Herein, the high-entropy Prussian blue analogues were selenized by the vapor infiltration method, resulting in the formation of a core-shell structured high-entropy selenides (HESe-6). The core-shell structure with voids and abundant selenium vacancies on the surface effectively mitigates bulk expansion and enhances electronic conductivity. Furthermore, the high-entropy property endows an ultra-stable crystal structure and inhibits the dissolution of metal ions. The ex-situ EIS and in-situ XRD results show that HESe-6 is able to be reversibly transformed into highly conductive ultrafine metal particles upon Na+ embedding, providing more Na+ reactive active sites. In addition, despite the incorporation of up to seven different elements, it exhibits minimal phase transitions during discharge/charge cycles, effectively mitigating stress accumulation. HESe-6 could retain an ultralong-term stability of 765.83 mAh g-1 after 1000 loops even at 1 A g-1. Furthermore, when coupled with the Na3V2(PO4)2O2F cathode, it maintains a satisfactory charge energy density of 303 Wh kg-1 after 300 cycles, which shows promising application prospect in the future.

Ultra-Fast-Charging, Long-Duration, and Wide-Temperature-Range Sodium Storage Enabled by Multiwalled Carbon Nanotube-Hybridized Biphasic Polyanion-Type Phosphate Cathode Materials.

Sodium-ion batteries (SIBs) represent a promising energy storage technology with great safety. Because of their high operating potential, superior structural stability, and prominent thermal stability, polyanion-type phosphates have garnered significant interest in superior prospective cathode materials for SIBs. Nevertheless, the disadvantages of poor intrinsic electronic conductivity, sluggish kinetics, and volume variation during sodiation/desodiation remain great challenges for satisfactory rate performance and cycle stability, which severely hinder their further practical applications. In this work, by adjusting the amounts of pretreated multiwalled carbon nanotubes (CNT) added intentionally at the beginning of the preparation, biphasic polyanion-type phosphate materials (marked as NFC) are synthesized through a one-pot solid state reaction methodology, which are composed of CNT-interwoven Na3V2(PO4)2F3 (NVPF) and a small amount of Na3V2(PO4)3 (NVP). Benefiting from the improved electronic conductivity and unique composition and structure, the optimized sample (labeled as NFC-2) illustrates exceptional cycle stability and remarkable rate performance. The discharge capacities of the NFC-2 electrode are 114.8 and 78.6 mAh g-1 tested at 20 and 5000 mA g-1, respectively. Notably, such an electrode still gives out 75.7% capacity retention upon 10 000 cycles at 5000 mA g-1. In situ X-ray diffraction analysis demonstrates that the NFC-2 cathode has outstanding structural reversibility during charge/discharge cycles. More importantly, such a biphasic material has achieved impressive electrochemical performance within a wide operating temperature range of -20-50 °C. When temperature is decreased to -20 °C, the NFC-2 electrode still delivers an initial discharge capacity of 102.4 mAh g-1 and exhibits a remarkable capacity retention of 97.8% even after 500 cycles at 50 mA g-1. In addition, the sodium-ion full cell assembled by integrating NFC-2 cathode and hard carbon anode shows a satisfying energy density of 431.3 Wh kg-1 at 20 mA g-1 with a better long-term cycle performance. The synergistic effect among high energy NVPF, conductive CNT, and stable NVP may lead to the great improvement in the electrochemical sodium storage performance of the NFC-2 sample. Such biphasic polyanion-type phosphate materials will inject new ideas into the material design for SIBs with excellent electrochemical performance and further promote practical applications of this advanced energy storage technology.

Se-induced defective carbon nanotubes promoting superior kinetics and electrochemical performance in Na3V2(PO4)3 for half and full Na ion cells.

Na3V2(PO4)3 (NVP), with unique Na super ionic conductivity (NASICON) framework, has become an prospective cathode material. However, the low electronic conductivity and poor structural stability limit its further development. Currently, the optimized carbon nanotubes (CNTs) by selenium doping are utilized to modify NVP system for the first time. Notably, the introduction of selenium in CNTs promotes to generate more defects, resulting in abundant active sites for the de-intercalation of Na+ to achieve more pseudocapacitance. Moreover, the newly formative C-Se bonds possess much stronger bond energy than the original CC (586.6 KJ mol-1 vs 377.4 KJ mol-1) bonds. The structure arrangement of the original CNTs is significantly improved by the doped selenium element, indicating that an enhanced carbon skeleton could be obtained to sustain the structural stability of NVP system. Furthermore, the excess selenium can be doped into the bulk of NVP crystal to replace of partial oxygen. Due to the larger ionic of Se2- (1.98 Å vs 1.4 Å of O2-), the VSe6 group has larger framework, which provides a broadened pathway for Na+ migration to improve the kinetic characteristics. Accordingly, the modified NVP@CNTs:Se = 1:1 sample exhibits superior rate capability and cyclic performance. It reveals high capacities of 78.6 and 76.5 mAh/g at 20 and 60C, maintaining 65.4 and 53.8 mAh/g after 5000 and 7000 cycles with high capacity retention of 84.49 % and 70.32 %, respectively. The assembled NVP@CNTs:Se = 1:1//CHC full cell delivers a high value of 153.6 mAh/g, suggesting the optimized sample also behaves excellent application potentials.

An Ultra-Flexible Sodium-Ion Full Cell with High Energy/Power Density and Unprecedented Structural Stability.

Futuristic wearable electronics desperately need power sources with similar flexibility and durability. In this regard, the authors, therefore, propose a scalable PAN-PMMA blend-derived electrospinning protocol to fabricate free-standing electrodes comprised of cobalt hexacyanoferrate nanocube cathode and tin metal organic framework-derived nanosphere anode, respectively, for flexible sodium-ion batteries. The resulting unique inter-networked nanofiber mesh offers several advantages such as robust structural stability towards repeated bending and twisting stresses along with appreciable electronic/ionic conductivity retention without any additional post-synthesis processing. The fabricated flexible sodium ion full cells deliver a high working voltage of 3.0 V, an energy density of 273 Wh·kg-1 , and a power density of 2.36 kW·kg-1 . The full cells retain up to 86.73% of the initial capacity after 1000 cycles at a 1.0 C rate. After intensive flexibility tests, the full cells also retain 78.26% and 90.78% of the initial capacity after 1000 bending and twisting cycles (5 mm radius bending and 40o axial twisting), respectively. This work proves that the proposed approach can also be employed to construct similar robust, free-standing nanofiber mesh-based electrodes for mass-producible, ultra-flexible, and durable sodium ion full cells with commercial viability.

A Dithiin-Linked Covalent Organic Polymer for Ultrahigh Capacity Half-Cell and Symmetric Full-Cell Sodium-Ion Batteries.

Sodium ion-batteries (SIBs) are considered as a class of promising alternatives to lithium-ion batteries (LIBs) to overcome their drawbacks of limited sources and safety problems. However, the lack of high-performance electrode materials hinders the wide-range commercialization of SIBs. Comparing to inorganic counterparts, organic electrode materials, which are benefitted from flexibly designable structures, low cost, environmental friendliness, and high theoretical gravimetric capacities, should be a prior choice. Here, a covalent organic polymer (COP) based material (denoted as CityU-9) is designed and synthesized by integrating multiple redox motifs (benzoquinone and thioether), improved conductivity (sulfur induction), and intrinsic insolubility (rigid skeleton). The half-cell SIBs exhibit ultrahigh specific capacity of 1009 mAh g-1 and nearly no capacity drop after 650 cycles. The first all-COP symmetric full-cell shows high specific capacity of 90 mAh g-1 and excellent rate capability. This work can extend the selection of redox-active moieties and provide a rational design strategy of high-performance novel organic electrode materials.

Carbonized Polymer Dots for Controlling Construction of MoS2 Flower-Like Nanospheres to Achieve High-Performance Li/Na Storage Devices.

Despite being one of the most promising materials in anode materials, molybdenum sulfide (MoS2 ) encounters certain obstacles, such as inadequate cycle stability, low conductivity, and unsatisfactory charge-discharge (CD) rate performance. In this study, a novel approach is employed to address the drawbacks of MoS2 . Carbon polymer dots (CPDs) are incorporated to prepare three-dimensional (3D) nanoflower-like spheres of MoS2 @CPDs through the self-assembly of MoS2 2D nanosheets, followed by annealing at 700 °C. The CPDs play a main role in the creation of the nanoflower-like spheres and also mitigate the MoS2 nanosheet limitations. The nanoflower-like spheres minimize volume changes during cycling and improve the rate performance, leading to exceptional rate performance and cycling stability in both Lithium-ion and Sodium-ion batteries (LIBs and SIBs). The optimized MoS2 @CPDs-2 electrode achieves a superb capacity of 583.4 mA h g-1 at high current density (5 A g-1 ) after 1000 cycles in LIBs, and the capacity remaining of 302.8 mA h g-1 after 500 cycles at 5 A g-1 in SIBs. Additionally, the full cell of LIBs/SIBs exhibits high capacity and good cycling stability, demonstrating its potential for practical application in fast-charging and high-energy storage.

High-Efficiency Separator Capacity-Compensation Strategy Applied to Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are expected to replace partial reliance on lithium-ion batteries (LIBs) in the field of large-scale energy storage as well as low-speed electric vehicles due to the abundance, wide distribution, and easy availability of sodium metal. Unfortunately, a certain amount of sodium ions are irreversibly trapped in the solid electrolyte interface (SEI) layer during the initial charging process, causing the initial capacity loss (ICL) of the SIBs. A separator capacity-compensation strategy is proposed, where the capacity compensator on the separator oxidizes below the high cut-off voltage of the cathode to provide additional sodium ions. This strategy shows attractive advantages, including adaptability to current production processes, no impairment of cell long-cycle life, controlled pre-sodiation degree, and strategy universality. The separator capacity-compensation strategy is applied in the NaNi1/3 Fe1/3 Mn1/3 O2 (NMFO)||HC full cell and achieve a compensated capacity ratio of 18.2%. In the Na3 V2 (PO4 )3 (NVP)||HC full cell, the initial reversible specific capacity is increased from 61.0 mAh g-1 to 83.1 mAh g-1 . The separator capacity-compensation strategy is proven to be universal and provides a new perspective to enhance the energy density of SIBs.

Rational Design of a High-Loading Polysulfide Cathode and a Thin-Lithium Anode for Developing Lean-Electrolyte Lithium-Sulfur Full Cells.

Lithium-sulfur cells are attractive energy-storage systems because of their high energy density and the electrochemical utilization rates of the high-capacity lithium-metal anode and the low-cost sulfur cathode. The commercialization of high-performance lithium-sulfur cells with high discharge capacity and cyclic stability requires the optimization of practical cell-design parameters. Herein, a carbon structural material composed of a carbon nanotube skeleton entrapping conductive graphene is synthesized as an electrode substrate. The carbon structural material is optimized to develop a high-loading polysulfide cathode with a high sulfur loading capacity (6-12 mg cm-2 ), rate performance (C/10-C/2), and cyclic stability for 200 cycles. A thin lithium anode based on the carbon structural material is developed and exhibits long lithium stripping/plating stability for ≈2500 h with a lithium-ion transference number of 0.68. A lean-electrolyte lithium-sulfur full cell with a low electrolyte-to-sulfur ratio of 6 µL mg-1 is constructed with the designed high-loading polysulfide cathode and the thin lithium anode. The integration of all the critical cell-design parameters endows the lithium-sulfur full cell with a low negative-to-positive capacity ratio of 2.4, while exhibiting stable cyclability with an initial discharge capacity of 550 mAh g-1 and 60% capacity retention after 200 cycles.

Cycling Stability of Lithium-Ion Batteries Based on Fe-Ti-Doped LiNi0.5 Mn1.5 O4 Cathodes, Graphite Anodes, and the Cathode-Additive Li3 PO4.

This study addresses the improved cycling stability of Li-ion batteries based on Fe-Ti-doped LiNi0.5 Mn1.5 O4 (LNMO) high-voltage cathode active material and graphite anodes. By using 1 wt% Li3 PO4 as cathode additive, over 90% capacity retention for 1000 charge-discharge cycles and remaining capacities of 109 mAh g-1 are reached in a cell with an areal capacity of 2.3 mAh cm- 2 (potential range: 3.5-4.9 V). Cells without the additive, in contrast, suffer from accelerated capacity loss and increase polarization, resulting in capacity retention of only 78% over 1000 cycles. An electrolyte consisting of ethylene carbonate, dimethyl carbonate, and LiPF6 is used without additional additives. The significantly improved cycling stability of the full cells is mainly due to two factors, namely, the low MnIII content of the Fe-Ti-doped LNMO active material and the use of the cathode-additive Li3 PO4 . Crystalline Li3 PO4 yields a drastic reduction of transition metal deposition on the graphite anode and prevents Li loss and the propagation of cell polarization. Li3 PO4 is added to the cathode slurry that makes it a very simple and scalable process, first reported herein. The positive effects of crystalline Li3 PO4 as electrode additive, however, should apply to other cell chemistries as well.

Hierarchical 3D Porous Hydrogen-Substituted Graphdiyne for High-Performance Electrochemical Lithium-Ion Storage.

Graphdiyne (GDY) has realized significant achievements in lithium-ion batteries (LIBs) because of its unique π-conjugated skeleton with sp- and sp2-hybridized carbon atoms. Enriching the accessible surface areas and diffusion pathways of Li ions can realize more storage sites and rapid transport dynamics. Herein, three-dimensional porous hydrogen-substituted GDY (HsGDY) is developed for high-performance Li-ion storage. HsGDY, fabricated via a versatile interface-assisted synthesis strategy, exhibits a large specific surface area (667.9 m2 g-1), a hierarchical porous structure, and an expanded interlayer space, which accelerate Li-ion accessibility and lithiation/delithiation. Owing to this high π-conjugated, conductive, and porous framework, HsGDY exhibits a large reversible capacity (930 mA h g-1 after 100 cycles at 1 A g-1), superior cycle (720 mA h g-1 after 300 cycles at 1 A g-1), and rate (490 mA h g-1 at 5 A g-1) performances. Density functional theory calculations of the low diffusion barrier in the lamination and vertical directions further reveal the fast Li-ion transport kinetics of HsGDY. Additionally, a LiCoO2-HsGDY full cell is constructed, which exhibits a good practical charge/discharge capacity of 128 mA h g-1 and stable cycling behavior. This study highlights the advanced design of next-generation LIBs to sustainably develop the new energy industry.

Photo-Rechargeable Li-Ion Batteries using TiS2 Cathode.

Photo-rechargeable (solar) battery can be considered as an energy harvesting cum storage system, where it can charge the conventional metal-ion battery using light instead of electricity, without having other parasitic reactions. Here a two-electrode lithium-ion solar battery with multifaceted TiS2 -TiO2 hybrid sheets as cathode. The choice of TiS2 -TiO2 electrode ensures the formation of a type II semiconductor heterostructure while the lateral heterostructure geometry ensures high mass/charge transfer and light interactions with the electrode. TiS2 has a higher lithium binding energy (1.6 eV) than TiO2 (1.03 eV), ensuring the possibilities of higher amount of Li-ion insertion to TiS2 and hence the maximum recovery with the photocharging, as further confirmed by the experiments. Apart from the demonstration of solar solid-state batteries, the charging of lithium-ion full cell with light indicates the formation of lithium intercalated graphite compounds, ensuring the charging of the battery without any other parasitic reactions at the electrolyte or electrode-electrolyte interfaces. Possible mechanisms proposed here for the charging and discharging processes of solar batteries, based on the experimental and theoretical results, indicate the potential of such systems in the forthcoming era of renewable energies.

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 (387.6 mAh g-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.

P-Doping a Porous Carbon Host Promotes the Lithium Storage Performance of Red Phosphorus.

Red phosphorus (RP) is a promising anode material for use in lithium-ion batteries (LIBs) due to its high theoretical specific capacity (2596 mA h g-1). However, the practical use of RP-based anodes has been challenged by the material's low intrinsic electrical conductivity and poor structural stability during lithiation. Here, we describe a phosphorus-doped porous carbon (P-PC) and disclose how the dopant improves the Li storage performance of RP that was incorporated into the P-PC (designated as RP@P-PC). P-doping porous carbon was achieved using an in situ method wherein the heteroatom was added as the porous carbon was being formed. The phosphorus dopant effectively improves the interfacial properties of the carbon matrix as subsequent RP infusion results in high loadings, small particle sizes, and uniform distribution. In half-cells, an RP@P-PC composite was found to exhibit outstanding performance in terms of the ability to store and utilize Li. The device delivered a high specific capacitance and rate capability (1848 and 1111 mA h g-1 at 0.1 and 10.0 A g-1, respectively) as well as excellent cycling stability (1022 mA h g-1 after 800 cycles at 2.0 A g-1). Exceptional performance metrics were also measured when the RP@P-PC was used as an anode material in full cells that contained lithium iron phosphate as the cathode material. The methodology described can be extended to the preparation of other P-doped carbon materials that are employed in contemporary energy storage applications.

Molten salt synthesis of NiCo-NiCo2O4@C nanotubes as anode materials for Li-ion batteries.

The construction of carbon-encapsulated transition metal nanotube structures is a preferred method that can effectively slow down volume expansion, improve cycling stability and enhance the electrical conductivity of the reactive sites of lithium-ion batteries. In this study, nanotubes of carbon-coated NiCo-NiCo2O4 nanoparticles (NC-NCO@C) were prepared by a one-step molten salt method at high temperature using Ni and Co as catalytic centers and sodium acetate as carbon source. We used NC-NCO@C-2 nanotubes as anode materials for lithium-ion batteries(LIBs), which exhibited excellent lithium storage performance and good stability, with a specific capacity of 616.26 mAh g-1 after 1000 cycles at a high current density of 1 A g-1. In addition, NC-NCO@C-2 were used as anodes in lithium-ion full cells and LiFePO4 (LFP) was used as the cathode. The NC-NCO@C-2//LFP full-cell exhibits high capacity and good cycling stability, with a capacity of 100.7 mAh g-1 after 100 cycles and a capacity retention rate of 92%. The construction of NC, NCO, and carbon ternary complexes was found to activate and promote the reversible conversion of certain inorganic components at the solid electrolyte interfaces (SEI), which effectively reduced the volume change during cycling, increased the electrical conductivity, and improved the cycling stability of the electrode. The proposed one-step molten salt synthesis of Carbon-coated metals complexes with excellent compatibility characteristics, is expected to solve the problem of volume change in transition metals, which is encountered in LIBs applications.

Insights into Electrolytic Pre-Lithiation: A Thorough Analysis Using Silicon Thin Film Anodes.

Pre-lithiation via electrolysis, herein defined as electrolytic pre-lithiation, using cost-efficient electrolytes based on lithium chloride (LiCl), is successfully demonstrated as a proof-of-concept for enabling lithium-ion battery full-cells with high silicon content negative electrodes. An electrolyte for pre-lithiation based on γ-butyrolactone and LiCl is optimized using boron-containing additives (lithium bis(oxalato)borate, lithium difluoro(oxalate)borate) and CO2 with respect to the formation of a protective solid electrolyte interphase (SEI) on silicon thin films as model electrodes. Reversible lithiation in Si||Li metal cells is demonstrated with Coulombic efficiencies (CEff ) of 95-96% for optimized electrolytes comparable to 1 m LiPF6 /EC:EMC 3:7. Formation of an effective SEI is shown by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). electrolytic pre-lithiation experiments show that notable amounts of the gaseous product Cl2 dissolve in the electrolyte leading to a self-discharge Cl2 /Cl- shuttle mechanism between the electrodes lowering pre-lithiation efficiency and causing current collector corrosion. However, no significant degradation of the Si active material and the SEI due to contact with elemental chlorine is found by SEM, impedance, and XPS. In NCM111||Si full-cells, the capacity retention in the 100th cycle can be significantly increased from 54% to 78% by electrolytic pre-lithiation, compared to reference cells without pre-lithiation of Si.

Iodine-Ion-Assisted Galvanic Replacement Synthesis of Bismuth Nanotubes for Ultrafast and Ultrastable Sodium Storage.

Bismuth (Bi) has emerged as a promising anode material for fast-charging and long-cycling sodium-ion batteries (SIBs). However, its dramatically volumetric variations during cycling will undesirably cause the pulverization of active materials, severely limiting the electrochemical performance of Bi-based electrodes. Constructing hollow nanostructures is recognized as an effective way to resolve the volume expansion issues of alloy-type anodes but remains a great challenge for metallic bismuth. Here, we report a facile iodine-ion-assisted galvanic replacement approach for the synthesis of Bi nanotubes (NTs) for high-rate, long-term and high-capacity sodium storage. The hollow tubular structure effectively alleviates the structural strain during sodiation/desodiation processes, resulting in excellent structural stability; the thin wall and large surface area enable ultrafast sodium ion transport. Benefiting from the structural merits, the Bi NT electrode exhibits extraordinary rate capability (84% capacity retention at 150 A g-1) and outstanding cycling stability (74% capacity retention for 65,000 cycles at 50 A g-1), which represent the best rate performance and longest cycle life among all reported anodes for SIBs. Moreover, when coupled with the Na3(VOPO4)2F cathode in full cells, this electrode also demonstrates excellent cycling performance, showing the great promise of Bi NTs for practical application. A combination of advanced research techniques reveals that the excellent performance originates from the structural robustness of the Bi NTs and the fast electrochemical kinetics during cycling.

Nonsacrificial Nitrile Additive for Armoring High-Voltage LiNi0.83 Co0.07 Mn0.1 O2 Cathode with Reliable Electrode-Electrolyte Interface toward Durable Battery.

High-capacity Ni-rich layered oxides are considered as promising cathodes for lithium-ion batteries. However, the practical applications of LiNi0.83 Co0.07 Mn0.1 O2  (NCM83) cathode are challenged by continuous transition metal (TM) dissolution, microcracks and mixed arrangement of nickel and lithium sites, which are usually induced by deleterious cathode-electrolyte reactions. Herein, it is reported that those side reactions are limited by a reliable cathode electrolyte interface (CEI) layer formed by implanting a nonsacrificial nitrile additive. In this modified electrolyte, 1,3,6-Hexanetricarbonitrile (HTCN) plays a nonsacrificial role in modifying the composition, thickness, and formation mechanism of the CEI layers toward improved cycling stability. It is revealed that HTCN and 1,2-Bis(2-cyanoethoxy)ethane (DENE) are inclined to coordinate with the TM. HTCN can stably anchor on the NCM83 surface as a reliable CEI framework, in contrast, the prior decomposition of DENE additives will damage the CEI layer. As a result, the NCM83/graphite full cells with the LiPF6-EC/DEC-HTCN (BE-HTCN) electrolyte deliver a high capacity retention of 81.42% at 1 C after 300 cycles at a cutoff voltage of 4.5 V, whereas BE and BE-DENE electrolytes only deliver 64.01% and 60.05%. This nonsacrificial nitrile additive manipulation provides valuable guidance for developing aggressive high-capacity Ni-rich cathodes.

Organic Small Molecules with Electrochemical-Active Phenolic Enolate Groups for Ready-to-Charge Organic Sodium-Ion Batteries.

Organic materials have attracted much attention in sodium ion batteries (SIBs) because of their advantages such as being environmentally benign and having high designability. Capacities and cycle life of organic materials are the most important parameters in most research which has been paid much effort to obtain an impressive electrochemical performance on the material level, and the sodium-detachable ability of these materials to directly match with the sodium-free anode is neglected. In this work, one organic sodium salt (C6 H2 Na2 O6 ) exhibits the unique ability (charging first in half cell) unlike other reported organic cathode materials (normally discharging first) for SIBs. The redox mechanism and structure change are investigated by in situ and ex situ tests to give a better understanding for C6 H2 Na2 O6 . Satisfying electrochemical performance (74% capacity retention after 600 cycles at 0.05 A g-1 and 63% capacity retention at 5 A g-1 when compared with capacity at 0.05 A g-1 ) is achieved by the C6 H2 Na2 O6 electrode. In addition, matched with hard carbon, full cells are assembled successfully like other transition metal containing cathode materials because C6 H2 Na2 O6 electrode can deliver its sodium ions to a sodium-free anode directly without any presodiation.

Ultrastable and High Energy Calcium Rechargeable Batteries Enabled by Calcium Intercalation in a NASICON Cathode.

Ca-ion batteries (CIBs) have been considered a promising candidate for the next-generation energy storage technology owing to the abundant calcium element and the low reduction potential of Ca2+ /Ca. However, the large size and divalent nature of Ca2+ induce significant volume change and sluggish ion mobility in intercalation cathodes, leading to poor reversibly and low energy/power densities for CIBs. Herein, a polyanionic Na superionic conduction (NASICON)-typed Na-vacant Na1 V2 (PO4 )2 F3 (N1 PVF3 ) with sufficient interstitial spaces is reported as ultra-stable and high-energy Ca ion cathodes. The N1 PVF3 delivers exceptionally high Ca storage capacities of 110 and 65 mAh g-1 at 10 and 500 mA g-1 , respectively, and a record-long cyclability of 2000 cycles. More interestingly, by tailoring the fluorine content in N1 PVFx (1 ≤ x ≤ 3), the high working potential of 3.5 V versus Ca2+ /Ca is achievable. In conjunction with Ca metal anode and a compatible electrolyte, Ca metal batteries with N1 VPF3 cathodes are constructed, which deliver an initial energy density of 342 W h kg-1 , representing one of the highest values thus far reported for CIBs. Origins of the uncommonly stable and high-power capabilities for N1 PVF3 are elucidated as the small volume changes and low cation diffusion barriers among the cathodes.