Enabling Ultralow-Temperature (-70 °C) Lithium-Ion Batteries: Advanced Electrolytes Utilizing Weak-Solvation and Low-Viscosity Nitrile Cosolvent.

Low-temperature performance of lithium-ion batteries (LIBs) has always posed a significant challenge, limiting their wide application in cold environments. In this work, the high-performance LIBs working under ultralow-temperature conditions, which is achieved by employing the weak-solvation and low-viscosity isobutyronitrile as a cosolvent to tame the affinity between solvents and lithium ions, is reported. The as-prepared electrolytes exhibit a sufficiently high conductivity (1.152 mS cm-1 ) at -70 °C. The electrolytes enable LiCoO2 cathode and graphite anode to achieve high Coulombic efficiency of >99.9% during long-term cycling at room temperature, and to respectively achieve 75.8% and 100.0% of their room-temperature capacities at -40 °C. Even the LiCoO2 //graphite pouch cells can retain 68.7% of the room-temperature capacity when discharged at -70 °C, and present stable cycling performance at -40 and 60 °C. This work provides a solution for the development of advanced electrolytes to enable LIBs working at wide-temperatures range.

Correlating the Solvating Power of Solvents with the Strength of Ion-Dipole Interaction in Electrolytes of Lithium-ion Batteries.

The solvation structure of Li+ plays a significant role in determining the physicochemical properties of electrolytes. However, to date, there is still no clear definition of the solvating power of different electrolyte solvents, and even the solvents that preferentially participate in the solvation structure remain controversial. In this study, we comprehensively discuss the solvating power and solvation process of Li+ ions using both experimental characterizations and theoretical calculations. Our findings reveal that the solvating power is dependent on the strength of the Li+ -solvent (ion-dipole) interaction. Additionally, we uncover that the anions tend to enter the solvation sheath in most electrolyte systems through Li+ -anion (ion-ion) interaction, which is weakened by the shielding effect of solvents. The competition between the Li+ -solvent and Li+ -anion interactions ultimately determines the final solvation structures. This insight into the fundamental understanding of the solvation structure of Li+ provides inspiration for the design of multifunctional mixed-solvent electrolytes for advanced batteries.

Revealing the structural chemistry in Na6-2xFex(SO4)3 (1.5 ≤ x ≤ 2.0) for low-cost and high-performance sodium-ion batteries.

Fe-based polyanionic sulfate materials are one of the most promising candidates for large-scale applications in sodium-ion batteries due to their low cost and excellent electrochemical performance. Although great achievements have been gained on a series of Na6-2xFex(SO4)3 (NFSO-x, 1.5 ≤ x ≤ 2.0) materials such as Na2Fe2(SO4)3, Na2Fe1.5(SO4)3, and Na2.4Fe1.8(SO4)3 for sodium storage, the phase and structure characteristics on these NFSO-x are still controversial, making it difficult to achieve phase-pure materials with optimal electrochemical properties. Herein, six NFSO-x samples with varied x are investigated via both experimental methods and density functional theory calculations to analyze the phase and structure properties. It reveals that a pure phase exists in the 1.6 ≤ x ≤ 1.7 region of the NFSO-x, and part of Na ions tend to occupy Fe sites to form more stable frameworks. The NFSO-1.7 exhibits the best electrochemical performance among the NFSO-x samples, delivering a high discharge capacity (104.5 mAh g-1 at 0.1 C, close to its theoretical capacity of 105 mAh g-1), excellent rate performance (81.5 mAh g-1 at 30 C), and remarkable cycle stability over 10,000 cycles with high-capacity retention of 72.4%. We believe that the results are useful to clarify the phase and structure characteristics of polyanionic materials to promote their application for large-scale energy storage.

4-1BB-Based CAR T Cells Effectively Reverse Exhaustion and Enhance the Anti-Tumor Immune Response through Autocrine PD-L1 scFv Antibody.

Exhaustion of chimeric antigen receptor (CAR) T cells is one of the limitations for CAR T efficacy in solid tumors and for tumor recurrence after initial CAR T treatment. Tumor treatment with a combination of programmed cell death receptor-1 (PD-1)/programmed cell death ligand-1 (PD-L1) blockage and CD28-based CAR T cells has been intensively studied. However, it remains largely unclear whether autocrine single-chain variable fragments (scFv) PD-L1 antibody can improve 4-1BB-based CAR T cell anti-tumor activity and revert CAR T cell exhaustion. Here, we studied T cells engineered with autocrine PD-L1 scFv and 4-1BB-containing CAR. The antitumor activity and exhaustion of CAR T cells were investigated in vitro and in a xenograft cancer model using NCG mice. CAR T cells with autocrine PD-L1 scFv antibody demonstrate enhanced anti-tumor activity in solid tumors and hematologic malignancies by blocking the PD-1/PD-L1 signaling. Importantly, we found that CAR T exhaustion was largely diminished by autocrine PD-L1 scFv antibody in vivo. As such, 4-1BB CAR T with autocrine PD-L1 scFv antibody combined the power of CAR T cells and the immune checkpoint inhibitor, thereby increasing the anti-tumor immune function and CAR T persistence, providing a cell therapy solution for a better clinical outcome.

Microstructure-Dependent Charge/Discharge Behaviors of Hollow Carbon Spheres and its Implication for Sodium Storage Mechanism on Hard Carbon Anodes.

Hard carbons are actively developed as a promising anode material for sodium ion batteries (SIBs). However, their sodium storage mechanism is poorly understood, leading to difficulties in design and development of high-performance hard carbon anode materials. In this work, hollow carbon spheres (HCSs) with different shell thickness as a model material to investigate the correlation between the microstructural change and resulting Na+ storage behavior during charge/discharge cycles are designed and synthesized. Ex situ X-ray diffraction and Raman evidences reveal that an interlayer spacing change of the graphitic nanodomains occurs in HCS electrode, leading to a shift of the reversible capacity from the high-potential sloping (HPS) region to the low-potential plateau (LPP) region. This unusual capacity shift suggests a microstructure-dependent Na+ storage reaction on the HCS electrode and can be well explained by "adsorption-intercalation" mechanism for these HCS materials. This work strengthens the understanding of the sodium storage behavior and provides a new perspective for the morphological and structural design of hard carbon anode materials for high-performance SIBs.

Effects of Comonomers on the Performance of Stable Phosphonate-Based Gel Terpolymer Electrolytes for Sodium-Ion Batteries with Ultralong Cycling Stability.

Gel polymer electrolyte (GPE) is one of the most promising alternatives to solve the bottlenecks of nonaqueous liquid electrolytes such as decomposition, safety hazards, and growth of dendrites. In this work, three novel methyl phosphonate-based crosslinking gel terpolymer electrolytes with different comonomers are designed and prepared by in situ radical polymerization. The gel polymer electrolytes have excellent thermal stability, wide electrochemical windows (≥4.9 V), and high ionic conductivities (±3 mS cm-1), and may be used as less-flammable electrolytes for sodium-ion batteries. 31P NMR spectra, Arrhenius plot, and density functional theory (DFT) calculations confirm that multifunctional phosphonate structural units promote the dissociation of NaClO4 and help to transport the sodium ions freely in the polymer framework. X-ray photoelectron spectroscopy (XPS) results show that the gel polymer electrolytes have the capability of inhibiting liquid electrolyte decomposition and the formation of the stable solid electrolyte interphase (SEI) film. The Na3V2(PO4)3/GPE/Na cells exhibit better ultralong cycling stability and enhanced temperature performance than those of liquid cells. Strikingly, GPE1 has the best comprehensive electrochemical performance, especially the rate performance and long-term cycling stability with a capacity retention ratio of 82.6% after 3500 cycles, which indicates that different comonomers have obvious effects on the performance. Therefore, the full cell of SnS2/GPE1/Na3V2(PO4)3 is evaluated and delivers good cycling stability of 500 cycles, holding a great prospect for the design and production of phosphorus-containing electrolytes for safer sodium-ion batteries.

Efficient and Facile Electrochemical Process for the Production of High-Quality Lithium Hexafluorophosphate Electrolyte.

The global consumption for lithium hexafluorophosphate (LiPF6) has increased dramatically with the rapid growth of Li-ion batteries (LIBs) for large-scale electric energy storage applications. Conventional LiPF6 production has a high cost and high energy consumption due to complicated separation and purification processes. Here, based on the electrode materials of LiMn2O4 and polyaniline (PANI), we propose a facile electrochemical extraction/release process for LiPF6 electrolyte production. This new technology consists of two independent steps: a PF6-- and Li+-extracting step using a PANI/LixMn2O4 cell in aqueous solution (an ion extraction step) and a LiPF6 electrolyte production step from the charged LiMn2O4/PANI+PF6- cell in an organic electrolyte (an ion release step). This new process can effectively avoid the contamination of HF residue in the final product, providing a great possibility to create a facile, energy-efficient, and low-cost LiPF6 electrolyte production.

Enabling electrochemical compatibility of non-flammable phosphate electrolytes for lithium-ion batteries by tuning their molar ratios of salt to solvent.

We develop a new type of electrolyte with a high molar ratio (MR) of salt to solvent but a low molar concentration by adjusting the molar mass of the solvent. The present 1 : 2 LiFSI-triamyl phosphate electrolyte exhibits a low molar concentration of only 1.35 M along with excellent electrochemical stability against the graphite anode.

Bimetal Synergistic Effect Induced High Reversibility of Conversion-Type Ni@NiCo2S4 as a Free-Standing Anode for Sodium Ion Batteries.

Conversion-type anode materials for sodium ion batteries have received extensive attention because of their relatively high theoretical capacity. However, multiple challenging obstacles stand in the way of their commercial application, especially their poor cycling stability resulting from the bad reversibility of the conversion reaction. Herein, Ni-Co bimetal sulfide was selected and investigated with the goal of improving the reversibility of the conversion reaction owing to the similarity of Ni and Co. As expected, when three-dimensional hierarchical Ni@NiCo2S4 (NiCo2S4 nanowires growing on the Ni foam) was applied as the free-standing anode for sodium ion batteries, it demonstrated high capacity and excellent cycling stability (90.65%, 100 cycles) compared with those of monometallic sulfides. Various characterization [in situ X-ray diffraction (XRD), ex situ XRD, ex situ X-ray photoelectron spectroscopy, FESEM mapping, and high-resolution transmission electron microscopy] tests confirmed that the Ni-Co alloy was formed during the discharge process and effectively prevented the crystalline grain growth of conversion reaction products, improving the reaction kinetics and reversibility.

Facile and reversible digestion and regeneration of zirconium-based metal-organic frameworks.

The digestion/regeneration of metal-organic frameworks (MOFs) has important applications for catalysis, drug delivery, environmental decontamination, and energy storage, among other applications. However, research in this direction is limited and very challenging. Here, we develop a facile method to digest and regenerate a series of zirconium-based metal-organic frameworks (Zr-MOFs) by bicarbonate or carbonate salts. As an example, UiO-66 demonstrates well the mechanism of reversible digestion/regeneration processes. By analyzing the digested zirconium species via X-ray diffraction, Fourier transform infrared spectroscopy and Raman scattering spectroscopy, a digestion mechanism based on the formation of dissoluble complexes [Zr2(OH)2(CO3)4]2- is proposed. Impressively, ultrafine Pd nanoparticles can be extracted from Pd@PCN-224 via this strategy. This work, thus, may provide new insight for the development of renewable MOFs and their practical applications.

A Membrane-Free and Energy-Efficient Three-Step Chlor-Alkali Electrolysis with Higher-Purity NaOH Production.

Conventional chlor-alkali processes are energy-consuming and environmentally unfriendly. To deal with this problem, we developed a three-step electrolysis (TSE) for a cleaner, energy-saving, and lower-cost chlor-alkali process. This new chlor-alkali process consists of three independent steps: a NaOH-production step in a Na0.44MnO2/oxygen-depolarizing cathode cell (step I), a Na+ and CI- extraction step in a Ag/Na0.44-xMnO2 cell (step II), and a CI2-production step in a graphite/AgCl cell (step III). This technology avoids the use of expensive ion-exchange membrane and toxic electrode materials, providing a great prospect to create a cleaner, energy-saving, and lower-cost chlor-alkali electrolysis process. This electrochemical ion coupling/decoupling technology can also be extended to other salt solutions (Na2SO4/NaNO3) to produce corresponding alkali (NaOH) and acid (H2SO4/HNO3), which has potential significance in the chlor-alkali industry.

Hollow carbon nanofibers as high-performance anode materials for sodium-ion batteries.

Hollow carbon nanofibers (HCNFs) are successfully fabricated by pyrolyzation of a polyaniline hollow nanofiber precursor. The as-prepared HCNFs as sodium storage anode materials exhibit a high reversible charge capacity of 326 mA h g-1 at 20 mA g-1, high rate capability (85 mA h g-1 at 1.6 A g-1) and superior cycling stability (a capacity retention of 70% even after 5000 cycles at 1.6 A g-1). Such a high performance of HCNFs can be ascribed to the special hollow structure characteristics; they possess a well fabricated electronic transport path and can shorten the ion diffusion distance. Therefore, the HCNFs can be regarded as promising anode materials for advanced sodium ion batteries (SIBs).

Highly Electrochemically-Reversible Mesoporous Na2 FePO4 F/C as Cathode Material for High-Performance Sodium-Ion Batteries.

As promising cathode materials, iron-based phosphate compounds have attracted wide attention for sodium-ion batteries due to their low cost and safety. Among them, sodium iron fluorophosphate (Na2 FePO4 F) is widely noted due to its layered structure and high operating voltage compared with NaFePO4 . Here, a mesoporous Na2 FePO4 F@C (M-NFPF@C) composite derived from mesoporous FePO4 is synthesized through a facile ball-milling combined calcination method. Benefiting from the mesoporous structure and highly conductive carbon, the M-NFPF@C material exhibits a high reversible capacity of 114 mAh g-1 at 0.1 C, excellent rate capability (42 mAh g-1 at 10 C), and good cycling performance (55% retention after 600 cycles at 5 C). The high plateau capacity obtained (>90% of total capacity) not only shows high electrochemical reversibility of the as-prepared M-NFPF@C but also provides high energy density, which mainly originates from its mesoporous structure derived from the mesoporous FePO4 precursor. The M-NFPF@C serves as a promising cathode material with high performance and low cost for sodium-ion batteries.

High-Safety Symmetric Sodium-Ion Batteries Based on Nonflammable Phosphate Electrolyte and Double Na3V2(PO4)3 Electrodes.

Sodium-ion batteries (SIBs) have been viewed as a promising candidate for grid-scale energy storage systems owing to their low cost and abundant Na resources. However, insufficient safety and poor cycling performance of current SIBs are hampering their implementation. Herein, we develop a symmetric SIB by employing Na3V2(PO4)3 as both cathode and anode along with the nonflammable triethyl phosphate dissolving 0.9 M NaClO4 as the electrolyte. The symmetric SIB demonstrates a superior rate capability (35.1 mA h g-1 at 32 C) and excellent cycling performance with a capacity retention of 88.9% after 500 cycles at 2 C. This work demonstrates a new avenue to construct safe and long-cycle-life SIBs with a simple electrode manufacturing process.

In Situ Formation of Co9S8 Nanoclusters in Sulfur-Doped Carbon Foam as a Sustainable and High-Rate Sodium-Ion Anode.

Transition-metal sulfides hold great promise as anode materials for sodium-ion batteries due to the high theoretical capacity and excellent redox reversibility based on multielectron conversion reactions. In this work, an elaborate composite, cobalt sulfide nanoclusters embedded in honeycomb-like sulfur-doped carbon foam (Co9S8@S-CF), is prepared via a facile sulfur-assisting calcination strategy, which tactfully induces the co-occurrence of in situ pore-forming, sulfidation, sulfur doping, and carbonization. Notably, sulfur-doped carbon foam (S-CF) possesses abundant voids, which are subject to construction of three-dimensional ionic/electronic pathways, leading to high sodium-ion accessibility and ultrafast sodium-ion/electron transportation toward Co9S8 nanoclusters. When worked as an anode in sodium-ion batteries, it delivers a remarkable capacity of 373 mA h g-1 over 1000 cycles at 0.25 C, achieving superior capacity retention of 80%. Furthermore, this anode could achieve unprecedented rate capability with a reversible capacity of 180 mA h g-1 at 50 C (20 A g-1), which significantly precedes those reported previously.

High-Performance Flexible Freestanding Anode with Hierarchical 3D Carbon-Networks/Fe7 S8 /Graphene for Applicable Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have gained tremendous interest for grid scale energy storage system and power energy batteries. However, the current researches of anode for SIBs still face the critical issues of low areal capacity, limited cycle life, and low initial coulombic efficiency for practical application perspective. To solve this issue, a kind of hierarchical 3D carbon-networks/Fe7 S8 /graphene (CFG) is designed and synthesized as freestanding anode, which is constructed with Fe7 S8 microparticles well-welded on 3D-crosslinked carbon-networks and embedded in highly conductive graphene film, via a facile and scalable synthetic method. The as-prepared freestanding electrode CFG represents high areal capacity (2.12 mAh cm-2 at 0.25 mA cm-2 ) and excellent cycle stability of 5000 cycles (0.0095% capacity decay per cycle). The assembled all-flexible sodium-ion battery delivers remarkable performance (high areal capacity of 1.42 mAh cm-2 at 0.3 mA cm-2 and superior energy density of 144 Wh kg-1 ), which are very close to the requirement of practical application. This work not only enlightens the material design and electrode engineering, but also provides a new kind of freestanding high energy density anode with great potential application prospective for SIBs.

Electrospun Flexible Cellulose Acetate-Based Separators for Sodium-Ion Batteries with Ultralong Cycle Stability and Excellent Wettability: The Role of Interface Chemical Groups.

Na-ion batteries are one of the best technologies for large-scale applications depending on almost infinite and widespread sodium resources. However, the state-of-the-art separators cannot meet the engineering needs of large-scale sodium-ion batteries to match the intensively investigated electrode materials. Here, a kind of flexible modified cellulose acetate separator (MCA) for sodium-ion batteries was synthesized via the electrospinning process and subsequently optimizing the interface chemical groups by changing acetyl to hydroxyl partly. Upon the rational design, the flexible MCA separator exhibits high chemical stability and excellent wettability (contact angles nearly 0°) in electrolytes (EC/PC, EC/DMC, diglyme, and triglyme). Moreover, the flexible MCA separator shows high onset temperature of degradation (over 250 °C) and excellent thermal stability (no shrinkage at 220 °C). Electrochemical measurements, importantly, show that the Na-ion batteries with flexible MCA separator exhibit ultralong cycle life (93.78%, 10 000 cycles) and high rate capacity (100.1 mAh g-1 at 10 C) in the Na/Na3V2(PO4)3 (NVP) half cell (2.5-4.0 V) and good cycle performance (98.59%, 100 cycles) in the Na/SnS2 half cell (0.01-3 V), respectively. Moreover, the full cell (SnS2/NVP) with flexible MCA separator displays the capacity of 98 mAh g-1 and almost no reduction after 40 cycles at 0.118 A g-1. Thus, this work provides a kind of flexible modified cellulose acetate separator for Na-ion batteries with great potential for practical large-scale applications.

Construction of 3D architectures with Ni(HCO3)2 nanocubes wrapped by reduced graphene oxide for LIBs: ultrahigh capacity, ultrafast rate capability and ultralong cycle stability.

Rechargeable lithium-ion batteries (LIBs) have been the dominating technology for electric vehicles (EV) and grid storage in the current era, but they are still extensively demanded to further improve energy density, power density, and cycle life. Herein, a novel 3D layered nanoarchitecture network of Ni(HCO3)2/rGO composites with highly uniform Ni(HCO3)2 nanocubes (average diameter of 100 ± 20 nm) wrapped in rGO films is facilely fabricated by a one-step hydrothermal self-assembly process based on the electrostatic interaction and coordination principle. Benefiting from the synergistic effects, the Ni(HCO3)2/rGO electrode delivers an ultrahigh capacity (2450 mA h g-1 at 0.1 A g-1), ultrafast rate capability and ultralong cycling stability (1535 mA h g-1 for the 1000th cycle at 5 A g-1, 803 mA h g-1 for the 2000th cycle at 10 A g-1). The detailed electrochemical reaction mechanism investigated by in situ XRD further indicates that the 3D architecture of Ni(HCO3)2/rGO not only provides a good conductivity network and has a confinement effect on the rGO films, but also benefits from the reversible transfer from LiHCO3 to Li x C2 (x = 0-2), further oxidation of nickel, and the formation of a stable/durable solid electrolyte interface (SEI) film (LiF and LiOH), which are responsible for the excellent storage performance of the Li-ions. This work could shed light on the design of high-capacity and low-cost anode materials for high energy storage in LIBs to meet the critical demands of EV and mobile information technology devices.

How to synthesize pure Li2-xFeSi1-xPxO4/C (x = 0.03-0.15) easily from low-cost Fe(3+) as cathode materials for Li-ion batteries.

Li2FeSiO4 is a low-cost, environmentally friendly electrode material with high theoretical capacity. However, obtaining pure-phase Li2FeSiO4 on a large scale is difficult. In this study, pure Li2-xFeSi1-xPxO4/C is prepared easily by using the low cost compound Fe(NO3)3·9H2O, with the help of citric acid and appropriate ratios of NH4H2PO4 (x = 0.03-0.15). The possible mechanism of the system with NH4H2PO4 to synthesize Li2-xFeSi1-xPxO4/C is that there is a catalysis process in the system, which helps to produce H2, providing a reducing environment in every particle of the reactants guaranteeing a complete change from Fe(3+) to Fe(2+). The produced H2 is verified by the gas chromatography of the collected gas produced in the calcination process. The ratios of NH4H2PO4 in this system could adjust the valence of element Fe in the products. Without NH4H2PO4, an Fe2O3 impurity is formed accompanying the Li2FeSiO4. With the addition of 1 at% NH4H2PO4, the Li4SiO4 impurity accords with the objective Li2-xFeSi1-xPxO4/C. Also, Fe with zero-valence could be found as an impurity with the addition of 20 at% NH4H2PO4 due to overreduction in the system. The synthesized pure Li2-xFeSi1-xPxO4/C (x = 0.03) displayed the highest discharge capacity of 179 mA h g(-1) in the first cycle, the best discharge capacity retention and the most reliable redox reversibility of the coulombic efficiency (approximately 100%), compared with the synthesized materials with Fe2O3 or Li4SiO4 impurities.

Pilot-scale experiment on anaerobic bioreactor landfills in China.

Developing countries have begun to investigate bioreactor landfills for municipal solid waste management. This paper describes the impacts of leachate recirculation and recirculation loadings on waste stabilization, landfill gas (LFG) generation and leachate characteristics. Four simulated anaerobic columns, R1-R4, were each filled with about 30 tons of waste and recirculated weekly with 1.6, 0.8 and 0.2m(3) leachate and 0.1m(3) tap water. The results indicated that the chemical oxygen demand (COD) half-time of leachate from R1 was about 180 days, which was 8-14 weeks shorter than that of R2-R4. A large amount of LFG was first produced in R1, and its generation rate was positively correlated to the COD or volatile fatty acid concentrations of influent leachates after the 30th week. By the 50th week of recirculation, the waste in R1 was more stabilized, with 931.2 kg COD or 175.6 kg total organic carbon released and with the highest landfill gas production. However, this contributed mainly to washout by leachate, which also resulted in the reduction of LFG generation potential and accumulation of ammonia and/or phosphorus in the early stage. Therefore, the regimes of leachate recirculation should be adjusted to the phases of waste stabilization to enhance efficiency of energy recovery. Integrated with the strategy of in situ leachate management, extra pre-treatment or post-treatment methods to remove the nutrients are recommended.