Low Interfacial Resistance Research Articles

Antibiotics photodegradation over recycling Z-scheme Bi2Ti2O7@Bi2S3/PU with super-efficiency: DFT calculation, toxicity of oxytetracycline intermediates and photoactivation mechanism

Inspired by the high sustainability, energy saving, cleanliness of photocatalysis (PC) with respect to antibiotics decomposition, we developed a stable, highly efficient Bi2Ti2O7@Bi2S3/polyurethane (BTO@Bi2S3/PU) photocatalytic system. It exhibited the best degradation performance with the removal of 82.08 % oxytetracycline (OTC) within 180 min under the optimal reaction parameters. Systematic characterization of BTO@Bi2S3/PU revealed its wider light-harvest capacity, higher electron–hole (e−–h+) separation efficiency, lower interface resistance, and better redox potential in heterojunction. Based on electrochemical characterization and density functional theory calculation, the construction of Z-scheme BTO@Bi2S3 photocatalyst substantially optimized the band structure. Moreover, the redox cycles of Bi3+/Bi5+ and Ti4+/Ti3+ further enhanced the charge transfer rate during the photoactivation process. For the OTC photodegradation pathways, ·OH, h+, ·O2−, and 1O2 dominated the pollutant decomposition and the toxicity of intermediates were decreased. Overall, the BTO@Bi2S3/PU photocatalytic system may provide a universal and stable technique for advanced photoheterojunction applications and wastewater purification.

Bias Voltage Dependency of Structural and Bipolar Plate-Related Properties of Cathodic Arc-Deposited Carbon-Based Coatings.

Carbon-based coatings composed of a chromium interlayer and a carbon top layer were deposited on stainless steel substrates via cathodic arc evaporation. During the carbon deposition, the bias voltage was varied between 900 and 1 V to investigate the influence on the structural, electrical, and electrochemical properties. Raman spectroscopy indicated a dependency of the intensity ratio and G peak position on the bias voltage, which can be attributed to an alteration of the structure. Transmission electron microscopy (TEM) cross-section investigations revealed a graphite-like structure for most carbon top layers but with an increasing amount of disordered fractions, eventually resulting in an amorphous structure at 1 V. To further examine the structure, electron energy loss spectroscopy (EELS) was used. In the high-loss region, distinct π* and σ* peaks could be observed, which agree well with the TEM results. Additionally, analysis of the low-loss region showed that the 1 V carbon top layer exhibits a shifted σ plasmon peak at 20 eV corresponding to an amorphous structure. The carbon-based coatings are highly conductive with low interfacial contact resistance values between 4 and 1.5 mΩ cm2 at 150 N cm-2. From a bias voltage of 200 V, the resistance increases. To evaluate the corrosion resistance, we conducted potentiodynamic polarization tests. At first, with decreasing bias voltage, the corrosion resistance increases and then decreases for both the 100 and 1 V samples. Considering the low thickness, the coating with a carbon top layer deposited at 600 V had the best corrosion resistance. In combination with the excellent contact resistance, the 600 V sample is a highly suitable coating for metallic bipolar plates.

A flexible PEO-based polymer electrolyte with cross-linked network for high-voltage all solid-state lithium-ion battery

Solid state lithium-ion batteries (SLIBs) have been considered as one of the most promising sustainable next-generation technologies for energy storage. However, the poor interfacial compatibility and low ion conductivity of solid electrolytes still remain a major challenge for SLIBs. Herein, a free-standing flexible solid polymer LA-PAM-PEO electrolyte is constructed through the electrospinning technology featuring with high Li+ conductivity (6.1 × 10−4 S cm−1), strong mechanical strength and high Li+ migration number (0.32), which breaks the restriction between ionic conductivity and mechanical strength in polymer solid electrolyte. The cross-linking between LA, PAM and PEO is verified to decrease the crystalline of PEO, thus increasing the Li+ conductivity. Moreover, benefiting from the 3D network composed of interconnected nanofibers and the covalent bonds between LA, PAM and PEO, the mechanical strength of LA-PAM-PEO SPE was also effectively improved. The LA-PAM-PEO SPE also delivers a high electrochemical window (4.95 V), and low interface resistance (243.8 Ω). As a result, the Li/Li symmetrical cell with the LA-PAM-PEO displayed outstanding stability after 1000 h with the uniform Li deposition on the interface of Li electrode, in sharp contrast to the PEO SPE. In addition, the Li/LA-PAM-PEO SPE/LFP displays a discharge capacity of 135 mA h g−1 after 1000 cycles at the rate of 1 C, with a capacity retention of 93.5%. The proposed LA-PAM-PEO SPE thus opens new possibilities for the fabrication and engineering of solid-state Li-ion batteries.

Synthesis of vertically aligned and interconnected BN fiber skeleton for significantly improving thermal conductivity of PVDF

Seeking efficient thermal management materials for electronic components is urgent and important. BN has high thermal conductivity and good insulating properties, making it an ideal polymer filler for improving thermal conductivity. Currently, because of the weak interaction between BN and its high melting point, it is extremely difficult to construct a BN three-dimensional skeleton by direct sintering to achieve efficient heat transfer channels. In this work, vertically aligned BN three-dimensional skeletons with fiber walls were synthesized in one step by combining the in-situ conversion of precursor fibers and directional freeze-drying technology. The precursor fibers were expelled by the directionally grown ice crystals, forming vertically aligned fiber walls. Importantly, molten B2O3 produced during air calcination made the fibers bond to each other, thus obtaining the vertically aligned and interconnected BN fiber skeleton. Benefiting from the short-path fast heat transfer and low interfacial thermal resistance of the fiber walls, the obtained vertically aligned BN skeleton exhibited obvious structural advantages, resulting in composites with a unidirectional thermal conductivity of 1.372 W/(m·K) with the filling content of 25.7 wt% and high enhancement efficiency per unit volume of 32.6 %. This approach is expected to open a new avenue for developing highly thermally conductive composites with great potential.

A Magnesium Carbonate Hydroxide Nanofiber/Poly(Vinylidene Fluoride) Composite Membrane for High-Rate and High-Safety Lithium-Ion Batteries.

Simultaneously high-rate and high-safety lithium-ion batteries (LIBs) have long been the research focus in both academia and industry. In this study, a multifunctional composite membrane fabricated by incorporating poly(vinylidene fluoride) (PVDF) with magnesium carbonate hydroxide (MCH) nanofibers was reported for the first time. Compared to commercial polypropylene (PP) membranes and neat PVDF membranes, the composite membrane exhibits various excellent properties, including higher porosity (85.9%) and electrolyte wettability (539.8%), better ionic conductivity (1.4 mS·cm-1), and lower interfacial resistance (93.3 Ω). It can remain dimensionally stable up to 180 °C, preventing LIBs from fast internal short-circuiting at the beginning of a thermal runaway situation. When a coin cell assembled with this composite membrane was tested at a high temperature (100 °C), it showed superior charge-discharge performance across 100 cycles. Furthermore, this composite membrane demonstrated greatly improved flame retardancy compared with PP and PVDF membranes. We anticipate that this multifunctional membrane will be a promising separator candidate for next-generation LIBs and other energy storage devices, in order to meet rate and safety requirements.

NaBr-Assisted Sintering of Na3Zr2Si2PO12 Ceramic Electrolyte Stabilizes a Rechargeable Solid-state Sodium Metal Battery.

Solid-state metal batteries with nonflammable solid-state electrolytes are regarded as the next generation of energy storage technology on account of their high safety and energy density. However, as for most solid electrolytes, low room temperature ionic conductivity and interfacial issues hinder their practical application. In this work, Na super ionic conductor (NASICON)-type Na3Zr2Si2PO12 (NZSP) electrolytes with improved ionic conductivity are synthesized by the NaBr-assisted sintering method. The effects of the NaBr sintering aid on the crystalline phase, microstructure, densification degree, and electrical performance as well as the electrochemical performances of the NZSP ceramic electrolyte are investigated in detail. Specifically, the NZSP-7%NaBr-1150 ceramic electrolyte has an ionic conductivity of 1.2 × 10-3 S cm-1 (at 25 °C) together with an activation energy of 0.28 eV. A low interfacial resistance of 35 Ω cm2 is achieved with the Na/NZSP-7%NaBr-1150 interface. Furthermore, the Na/NZSP-7%NaBr-1150/Na3V2(PO4)3 battery manifests excellent cycling stability with a capacity retention of 98% after 400 cycles at 1 C and 25 °C.

Green synthesized 3D coconut shell biochar/polyethylene glycol composite as thermal energy storage material

Developing stable, economic, safer and carbon-based nanoparticles from agro solid waste facilitates a new dimension of advancement for eco-friendly nanomaterials in competition to existing nanoparticles. Herewith, a three dimensional highly porous honeycomb structured carbon-based coconut shell (CS) nanoparticle is prepared through green synthesis technique using tube furnace to energies organic phase change material (PCM). CS nanoparticle synthesis using a green approach is incorporated with polyethylene glycol (PEG) using a two-step technique to develop PEG/CS nanocomposite PCM. Thermophysical features of the nanocomposites are characterized using transient hot bridge (ThB), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA), whereas optical property and chemical stability is evaluated using UV–Vis and FTIR spectrometers. Resulting nanocomposite demonstrates higher thermal conductivity by 114.5 % (improved from 0.24 W/m⋅K to 0.515 W/m⋅K). Energy storage enthalpy increased from 141.2 J/g to 150.1 J/g with 1.0 % weight fraction of CS nanoparticles. Optical absorbance of the nanocomposite is improved by 2.14 times compared to base PCM. The developed nanocomposite samples exhibit extreme thermal stability up to 215 °C. The 3D porous structure of CS nanoparticles shows better contact area with PEG, causing low interfacial thermal resistance for improved thermal network channels and pathways for extra heat transfer and phonon propagation.

Heterocyclic polymer supported cathode/Li interface layers to lower the operational temperature of PEO-based Li-batteries

High-performance poly (ethylene oxide) (PEO)-based solid-state polymer Li-batteries (SSLBs) at low temperature (≤ 25 ℃) is hindered by high interfacial resistance and low ionic conductivity. Herein, we simultaneously construct cathode and anode interface layers via in-situ heat-induced heterocyclic polymerization reaction, where the cathode-electrolyte interface layer (PPL) consists of bromine-doped poly (3,4-ethylene-dioxy-thiophene) (PEDOT), PEO and bis-trifluoromethanesulfonimide (LiTFSI), featuring with mixed ionic/electronic conduction, and the anode-electrolyte interface layer (PVCL) was formed by poly (vinyl carbonate) (PVC), PEO and LiTFSI, having a robust fast ionic conduction. Benefiting from the PEDOT conductivity, high mechanical strength of PVC and good interface affinity aroused by heat-induced reaction, the solid-state PEO-based LiFePO4||Li cell shows low interfacial resistance of 11.02 Ω that decreased by 92% compared to the cell without interface modification, and delivering a discharge capacity of 164.4 mAh g−1 at 0.1 C (25 ℃), as high as 115.9 mAh g−1 at 10 ℃. X-ray photoelectron spectroscopy revealed the enrichment of LiF, Li3N and LiBr on the lithium metal surface after cycling, further enhancing stable cycling Li-batteries. The dual interface-constructed strategy provides a reliable way to resolve the bottle-neck interfacial issues of SSLBs.

Self-Transformation of Atomically Precise Alloy Nanoclusters to Plasmonic Alloy Nanocrystals: Evaluating Photosensitization in Solar Water Oxidation.

Atomically precise alloy nanoclusters (NCs) inherit the advantages of homometal NC counterparts such as atomic stacking fashion, quantum confinement effect, and enriched catalytic active sites and simultaneously possess the advantageous physicochemical properties such as significantly enhanced photostability, ideal photosensitization efficiency, and favorable energy band structure. Nevertheless, elucidation of the roles of alloy NCs and alloy nanocrystals (NYs) in boosting solar water oxidation has so far not yet been reported owing to the deficiency of applicable alloy NC photosystems. Herein, utilizing the generic thermal-induced self-transformation of alloy NCs to alloy NYs, we comprehensively explore the photosensitization properties of glutathione (GSH)-capped alloy NCs (AgxAu1-x@GSH and CuxAu1-x@GSH) and the corresponding alloy NY (AgAu and CuAu) counterparts in solar water oxidation reaction. The results imply that photoelectrons of alloy NCs surpass the hot electrons over plasmonic alloy NYs in stimulating the PEC water oxidation reaction. The photoelectrons of alloy NCs demonstrate lower interfacial charge-transfer resistance, longer carrier lifetime, and a more enhanced photosensitization effect with respect to the plasmonic alloy NYs, contributing to the significantly boosted photoelectrochemical water oxidation activities. Moreover, we found that our result is universal.

Gelatin network reinforced poly (vinylene carbonate-acrylonitrile) based composite solid electrolyte for all-solid-state lithium metal batteries

Solid polymer electrolyte (SPE) has become one of the most promising candidate materials for building solid-state lithium batteries because of its excellent flexibility, expansibility and good interface compatibility with electrodes. However, SPE still has some problems such as low ionic conductivity at room temperature and narrow electrochemical window. Therefore, it is of great significance to develop polymer solid electrolyte with new structure to improve the comprehensive performance of the battery. In this work, Poly (vinylene carbonate-acrylonitrile) (PVN) was selected as the matrix of polymer electrolyte, and the network structure filled with biomass material gelatin was used as the skeleton. The composite solid polymer electrolyte (CSPE) composed of PVN, lithium bis (trifluoromethyl) sulfonimide (LiTFSI) and gelatin was prepared by simple solution casting method. The constructed PVN/LiTFSI/Gelatin (PLG) electrolyte has excellent ionic conductivity (3.47 × 10−4 S cm−1 at 60 °C) and wide electrochemical window (4.3 V). Li|10 %PLG CSPE|LiFePO4 battery has a capacity retention rate of 85 % after 1000 cycles of stable operation at 1C rate at 60 °C, and has excellent cycle performance and life. In addition, a low interface resistance enables highly reversible Li|Li symmetrical battery has a stably cycle of 1500 h at 0.1 mA cm−2 and has good interface compatibility. Therefore, PLG CSPE composite is a simple and effective strategy to obtain high-performance lithium batteries, which can realize the ultra-stable operation of solid lithium metal batteries.

Efficient Photocatalytic CO2 Reduction with High Selectivity for Ethanol by Synergistically Coupled MXene-Ceria and the Charge Carrier Dynamics.

The primary factors that govern the selectivity and efficacy of CO2 photoreduction are the degree of activation of CO2 on the active surface sites of photocatalysts and charge separation/transfer kinetics. In this context, the rational synthesis of heterostructured MXene-coupled CeO2-based photocatalysts with different loading concentrations of Ti3C2MXene via a one-step hydrothermal approach has been undertaken. These photocatalysts exhibit a shift in X-ray diffraction peaks to higher 2θ values and changes in stretching vibrations of 5 wt % Ti3C2MXene/CeO2(5-TC/Ce) that indicate interaction between Ti3C2MXene and CeO2. Moreover, XPS analysis confirms the presence of the Ce3+/Ce4+ states. A sharp band at 2335 cm-1 observed during the CO2 photoreduction process corresponds to bidentate b-CO32-, which facilitates the adsorption of CO2 at the surface of the catalyst as revealed by the TPD analysis. Furthermore, the Schryvers test and NMR analysis were undertaken to confirm the formaldehyde intermediate formation during CO2 photoreduction to C2H5OH. The decrease in emission intensity, reduced lifetimes (2.68 ns), and lower interfacial resistance, as revealed by PL, TR-PL, and EIS analysis, imply an efficient charge separation and charge transfer in the case of the Ti3C2MXene/CeO2 heterojunction. The decrease in the intensity of peaks in the EPR spectrum in the case of 5-TC/Ce further confirms efficient charge transfer kinetics across the interface. The optimized 5-TC/Ce shows CO2 reduction with a drastically enhanced yield of ethanol on the order of 6127 μmol g-1 at 5 h with 98% selectivity and 7.54% apparent quantum efficiency, which is 6-fold higher than that of ethanol produced by bare CeO2. Herein, CeO2 that acts as a redox couple (Ce3+/Ce4+) when coupled with MXene having a metallic nature that reduces the electron transfer resistance is in unison, enabling an enhanced mobilization of electrons. Thereby, the synergistic coupling of Ti3C2MXene with CeO2 leads to an efficient photoreduction of CO2 under visible light illumination.

Sandwich-like functional design of C/(Ti:C)/Ti modified Ti bipolar plates for proton exchange membrane fuel cells

An important challenge for proton exchange membrane (PEM) fuel cells is to achieve design innovation and lifetime enhancement of bipolar plates. The development of surface coatings for metal bipolar plates that combine electrical conductivity and corrosion resistance is essential to enhance durability and reduce costs. In this work, sandwich-like C/(Ti:C)/Ti modified Ti bipolar plates have been proposed based on computational simulations and experimental verification. The functional design is represented by predicted electrical conductivity and H2O adsorption behavior based on theoretical calculations. Experimentally, the C/(Ti:C)/Ti modified Ti bipolar plates achieves lower interfacial contact resistance (ICR) values of 1.51 mΩ cm2 with Ti mesh and 1.66 mΩ cm2 with carbon paper at 1.4 MPa. The corrosion current density significantly decreases to 0.21 μA cm−2 after potentiostatic polarization for 4 h at 0.6 V vs. Ag/AgCl. To meet the durability requirements of variable operating conditions, performance of Ti bipolar plates under high temperature, high acidity and high potential conditions has been discussed to assist in the functional design of surface films.

Gradient Nitrogen Doping in the Garnet Electrolyte for Highly Efficient Solid-State-Electrolyte/Li Interface by N2 Plasma.

Solid-state lithium batteries (SSBs) have been widely researched as next-generation energy storage technologies due to their high energy density and high safety. However, lithium dendrite growth through the solid electrolyte usually results from the catastrophic interface contact between the solid electrolyte and lithium metal. Herein, a gradient nitrogen-doping strategy by nitrogen plasma is introduced to modify the surface and subsurface of the garnet electrolyte, which not only etches the surface impurities (e.g., Li2CO3) but also generates an in situ formed Li3N-rich interphase between the solid electrolyte and lithium anode. As a result, the Li/LLZTON-3/Li cells show a low interfacial resistance (3.50 Ω cm2) with a critical current density of about 0.65 mA cm-2 at room temperature and 1.60 mA cm-2 at 60 °C, as well as a stable cycling life for over 1300 h at 0.4 mA cm-2 at room temperature. A hybrid solid-state full cell paired with a LiFePO4 cathode exhibits excellent cycling durability and rate performance at room temperature. These results demonstrate a rational strategy to enable lithium utilization in SSBs.

Enhancing pseudo-capacitive behavior in Mn-doped Co3O4 nanostructures for supercapacitor applications

The study focused on Mn-doped Co3O4 samples, which were synthesized successfully using the coprecipitation method and subsequently annealed at 600 °C. The X-ray diffraction (XRD) patterns displayed distinct peaks corresponding to the spinel-cubic structure of Co3O4. Notably, these patterns indicated a preference for (311) plane orientations, which shifted toward lower diffraction angles as the concentration of Mn increased. The analysis of crystallite sizes for the Mn-doped Co3O4 nanoparticles revealed values of 40 nm, 38 nm, and 38 nm for Co3O4:3%Mn, Co3O4:5%Mn, and Co3O4:7%Mn, respectively. Employing X-ray photoelectron spectroscopy (XPS), the study provided insights into the chemical constituents and valence states of the samples. It revealed the presence of both Co2+ and Co3+ ions, along with different oxygen states. The investigation into the electrochemical behavior of the Mn-doped Co3O4 nanostructures highlighted their pseudo-capacitive nature. The specific capacitance and cyclic stability of these structures were found to be contingent on the concentration of Mn doping. Electrochemical impedance spectroscopy (EIS) data unveiled low interfacial charge resistance and enhanced ion diffusion rates. Notably, the most striking results were observed with the 7 wt% Mn-doped Co3O4 nanomaterials. These materials exhibited an outstanding specific capacitance of 537 F/g at a current density of 1.5 A/g. Additionally, they demonstrated remarkable capacity retention of 94% over a span of 1500 cycles. In conclusion, the Mn-doped Co3O4 nanostructures showcased promising electrochemical performance, which could render them suitable for potential applications in supercapacitors.

An H2 O-Initiated Crosslinking Strategy for Ultrafine-Nanoclusters-Reinforced High-Toughness Polymer-In-Plasticizer Solid Electrolyte.

Incorporating plasticizers is an effective way to facilitate conduction of ions in solid polymer electrolytes (SPEs). However, this conductivity enhancement often comes at the cost of reduced mechanical properties, which can make the electrolyte membrane more difficult to process and increase safety hazards. Here, a novel crosslinking strategy, wherein metal-alkoxy-terminated polymers can be crosslinked by precisely controlling the content of H2 O as an initiator, is proposed. As a proof-of-concept, trimethylaluminum (TMA)-functionalized poly(ethylene oxide) (PEO) is used to demonstrate that ultrafine Al-O nanoclusters can serve as nodes to crosslink PEO chains with a wide range of molecular weights from 10000 to 8000000gmol-1 . The crosslinked polymer network can incorporate a high concentration of plasticizers, with a total weight percentage over 75%, while still maintaining excellent stretchability (4640%) and toughness (3.87×104 kJm-3 ). The resulting electrolyte demonstrates high ionic conductivity (1.41mScm-1 ), low interfacial resistance toward Li metal (48.1Ωcm2 ), and a wide electrochemical window (>4.8V vs Li+ /Li) at 30°C. Furthermore, the LiFePO4 /Li battery shows stable cycle performance with a capacity retention of 98.6% (146.3mAhg-1 ) over 1000 cycles at 1C (1C=170mAhg-1 ) at 30°C.

Co/N co‐doped flower‐like carbon‐based phase change materials toward solar energy harvesting

AbstractThe photothermal conversion capacity of pristine organic phase change materials (PCMs) is inherently insufficient in solar energy utilization. To upgrade their photothermal conversion capacity, we developed bimetallic zeolitic imidazolate framework (ZIF) derived Co/N co‐doped flower‐like carbon (Co/N‐FLC)‐based composite PCMs toward solar energy harvesting. 3D interconnected carbon framework with low interfacial thermal resistance, abundant carbon defects and high content of nitrogen doping, excellent localized surface plasmon resonance (LSPR) effect of Co nanoparticles, and light absorber Co3ZnC in Co/N‐FLC synergistically upgrade the photothermal capacity of (polyethylene glycol) PEG@Co/N‐FLC composite PCMs with an ultrahigh photothermal conversion efficiency of 94.8% under 0.16 W/cm2. Uniformly anchored Co and Co3ZnC nanoparticles in carbon framework guarantee excellent photon capture ability. Bridging carbon nanotubes (CNTs) in 2D carbon nanosheets further accelerate the rapid transport of phonons by constructing cross‐connected heat transfer paths. Additionally, PEG@Co/N‐FLC exhibits a thermal energy storage density of 100.69 J/g and excellent thermal stability and durable reliability. Therefore, PEG@Co/N‐FLC composite PCMs are promising candidates to accelerate the efficient utilization of solar energy.

Effect of ionizing radiation on thermal and mechanical properties of filled-epoxy adhesives

Stave assemblies at the Large Hadron Collider and other high-energy physics experiments require radiation-resistant adhesives composed of light elements with high thermal conductivity and low interfacial resistance. Porous carbon foams are currently bonded to carbon fiber faceplates with graphite-filled epoxy. Low-viscosity epoxies are used to increase the amount of filler in order to double the thermal conductivity without impacting the properties of the material under irradiation. Promising new adhesive formulations showed no degradation in thermal conductivity after exposure to a fluence of 1016 n/cm2 (>0.1 MeV neutrons) or 10 Gy gamma radiation, but showed variable degradation, compared to the currently used adhesive, after exposure to a fluence of 1015 p/cm2 (1 MGy, 67.5 MeV protons). Adhesives with more than double the irradiated thermal conductivity of the baseline material showed marked improvement in thermal transport in graphite/epoxy/foam/epoxy/graphite structures based on thermal diffusivity measurements. Silicon carbide particles can be added to graphite to stiffen the modulus of the filled epoxy. When spherical AlN was used as a filler, the degradation in thermal conductivity under proton irradiation varied based on the size of the ceramic filler. Options for improving the thermal performance of irradiated adhesives for high-energy physics experiments are discussed.

Low Temperature Research and Improvement on Lithium Ion Batteries

Lithium ion batteries have been the dominant power sources in portable electronics and electric vehicles due to their high energy density, long lifetime and environmental benignity. However, it is a big challenge for lithium ion batteries to be used at low temperature. Compared with the performance at room temperature, lithium ion batteries deliver much less capacity and energy at low temperature. The poor low temperature performance restricts the usage of lithium ion batteries for power electronics and electric vehicles in the winter. The results of previous research, suggest that the poor low temperature performance is attributed to the freezing of the liquid electrolyte which leads to low ionic conductivity and high interfacial resistance, especially on the anode side. Other researchers tried using a solvent with low melting point to partially replace ethylene carbonate or adding some additives to the electrolyte to enhance the ionic conductivity or modify the interface to reduce the resistance and then deliver more capacity and energy.In this research, we investigated the discharge capacity, energy, pulse power and electrochemical impedance spectroscopy at different depths of discharge of NCM622/Graphite lithium ion batteries at varied temperatures. We found that the discharge energy and pulse power are sensitive to the temperature decreasing. For the NCN622/Graphite cell (2.5 mAh cm-2) with commonly used LiPF6-EC/EMC electrolyte, at -20 oC the cell is able to deliver 65% capacity of that at 30 oC with C/3 discharge current rate, while the delivered energy is only 60%. The 30 seconds pulse power became much worse at -20 oC compared with the power at room temperature. In our research the poor low temperature performance is not from the low ionic conductivity and interfacial resistance. The dominant factor is the charge transfer impedance from the cathode side of the cell.To improve the low temperature performance, we explored the addition inexpensive nano-particles as the additive into the electrolyte. The cell composed of this electrolyte is able to release more than 70% capacity and energy at -20 oC of that measured at 30 oC. The charge transfer resistance in the fully charge state decreased almost 80% compared to a cell with baseline electrolyte. Meanwhile, the additive has no effect on the long-term cycling (1000 cycles) and stability at high temperature (55 oC) Fig.1. Normalized capacity and energy. Fig.2. The EIS of the full cell at 30 oC and -20 oC. Figure 1

Femtosecond-Laser Microstructuring Improves Solid-State Electrolyte/Cathode Ionic Transport

All-solid-state batteries (ASSBs) provide the opportunity for substantially enhanced gravimetric and volumetric energy and power density and improved safety. However, these gains will not be realized without first overcoming substantial challenges, notably, the high interfacial resistance between electrodes and the solid-state electrolyte (SSE) which requires high stack pressures, on the order of 10,000 psi, to achieve high performance metrics.[1,2]. Already there is a large and growing body of research demonstrating the advantages of laser structuring of Li-ion battery materials for enhanced kinetics and shorter diffusion pathways [3,4]. This work extends these advantages to ASSBs through lowering the catholyte-SSE interfacial impedance by increasing its surface area and providing less torturous paths for ion diffusion.The work presented here uses a near-IR (1030 nm) femtosecond laser (pulse duration approx. 250 fs) to ablate microstructures into the surface of a slurry-cast LiNi0.8Mn0.1Co0.1O2 (NMC811):Li6PS5Cl catholyte. Micrometer-sized channel structures were ablated at various depths and pitch spacings to assess the effect of patterning on cell performance. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) measurements were acquired on both pristine and patterned samples to ensure that the femtosecond laser pulses do not cause any residual compositional or phase changes, respectively. Critically, low interfacial resistance will require that an SSE layer be applied to the patterned catholyte such that the microstructure is preserved while maintaining intimate contact between the catholyte and SSE layer. SSE layers were both slurry cast and pellet-pressed onto both pristine and patterned electrodes. Cross-sectional SEM was used to investigate the degree of interfacial contact, and relate interface quality to parameters such as SSE application technique (e.g., pellet pressing vs. slurry casting) and slurry properties (i.e., viscosity). The improvement to interfacial ionic conductivity is assessed using electrochemical impedance spectroscopy (EIS). The effect of stack pressure is analyzed in order to assess the degree to which laser patterning can alleviate stack pressure requirements in ASSBs.

Improving lithium-ion battery performance with attapulgite nanoparticle-modified polypropylene separator

The separator is one of the important components of lithium-ion battery, but there are also some problems, such as low porosity, poor wettability and so on. Therefore, it is an important approach to improve the performance of lithium-ion battery by improving the performance of separator. In this paper, the attapulgite nanoparticle was modified onto the polypropylene separator for the first time by the surface covalent method, and the effect of attapulgite nanoparticles on the properties of separator and the performance of lithium-ion battery was studied in detail. Electron microscopy and infrared characterization results have showed that attapulgite nanoparticles were successfully immobilized on the surface of polypropylene separator by covalent reactions. Compared to the original polypropylene separator, the porosity of polypropylene separator modified with attapulgite nanoparticles was improved obviously (38 % VS 78 %). At the same time, the cost of attapulgite nanoparticle has a clear advantage over other studies. Compared to the lithium-ion battery equipped with original polypropylene separator, and the lithium-ion battery equipped with polypropylene separator modified with attapulgite nanoparticles based on the surface covalent reaction method has a better electrochemical kinetic reaction process and lower interfacial resistance. Meanwhile, the polypropylene separator modified with attapulgite nanoparticles could improve the performance of lithium-ion battery obviously (~ 110 %) in different c densities, and a capacity retention of 97.2 % and 87.3 % was gained for the battery modified with attapulgite nanoparticles at 0.5c and 1c respectively.