Li Half-cells Research Articles

Constructing a universal artificial polymeric ionic liquid interfacial film for graphite anode and High-Voltage cathode

The electrode/electrolyte interface stability is crucial for the cycling stability and the safety of lithium-ion batteries. Construction of a superior interfacial film is of vital significance to promote battery performance. For this purpose, we develop a universal polymeric ionic liquid (PIL) as an artificial interfacial film to suppress the electrolyte decomposition on the electrode surface. The PIL interfacial film shows outstanding properties such as high mechanical modulus, superb shape compliance, excellent electrochemical stability. Moreover, abundant cations in the PIL matrix can combine PF6− and carbonate solvents by Coulombic interaction and promote Li+ migration. Hence, the modified graphite anode with PIL layer achieves an improved cyclability with 89% of capacity retention after 150 cycles at 1C with a high initial Coulombic efficiency (96%), which is higher than that of the bare graphite anode. Meanwhile, the modified LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode also maintains 90% of initial capacity (186 mAh/g) after 120 cycles at high temperature (55 °C) and high voltage (cut-off charging voltage of 4.5 V), much better than that of the bare NCM622||Li half-cell (only 2.7%).

Boosting Reversibility and Stability of Li Storage in SnO2 -Mo Multilayers: Introduction of Interfacial Oxygen Redistribution.

Among the promising high-capacity anode materials, SnO2 represents a classic and important candidate that involves both conversion and alloying reactions toward Li storage. However, the inferior reversibility of conversion reactions usually results in low initial Coulombic efficiency (ICE, ≈60%), small reversible capacity, and poor cycling stability. Here, it is demonstrated that by carefully designing the interface structure of SnO2 -Mo, a breakthrough comprehensive performance with ultrahigh average ICE of 92.6%, large capacity of 1067 mA h g-1 , and 100% capacity retention after 700 cycles can be realized in a multilayer Mo/SnO2 /Mo electrode. Furthermore, high capacity retentions are also achieved in pouch-type Mo/SnO2 /Mo||Li half cells and Mo/SnO2 /Mo||LiFePO4 full cells. The amorphous SnO2 /Mo interfaces, which are induced by redistribution of oxygen between SnO2 and Mo, can precisely adjust the reversible capacity and cycling stability of the multilayers, while the stable capacities are parabolic with the interfacial density. Theoretical calculations and in/ex situ investigation reveal that oxygen redistribution in SnO2 /Mo heterointerfaces boosts Li-ion transport kinetics by inducing a built-in electric field and improves the reaction reversibility of SnO2 . This work provides a new understanding of interface-performance relationship of metal-oxide hybrid electrodes and pivotal guidance for creating high-performance Li-ion batteries.

Physical properties and compatibility with graphite and lithium metal anodes of non-flammable deep eutectic solvent as a safe electrolyte for high temperature Li-ion batteries

In this study we present the original formulation of a deep eutectic mixture based on lithium imide salt as an electrolyte for Li-ion batteries. The non-flammable liquid mixture obtained by mixing asymmetric lithium (fluorosulfonyl) (trifluoromethanesulfonyl) imide (LiFTFSI) with ethylene carbonate (EC) demonstrates its applicability as a safer electrolyte for Li-ion batteries. By comparison with conventional electrolytes containing the same salt, in 3EC/7EMC and EC/PC/3DMC, the volumetric properties of (EC-LiTFSI, 3/1, w), abbreviated EC-LiTFSI31, reveal the strong nature of the FTFSI−—EC coordination and the non-solvation of Li+, explaining the "stacking" effect observed. Transport properties (viscosity, conductivity and ionicity) are discussed and compared to those of conventional electrolytes, demonstrating that eutectic EC-LiTFSI31 has the typical ionicity of organized media such as ionic liquids or DESs, even if its concentration in salt is similar to that of the conventional electrolyte of 1 mol L−1.The electrochemical evaluation of the compatibility of this original electrolyte with lithium metal and with graphite in Li//Li and Gr//Li half-cells shows that EC-LiTFSI31 does not cause any erratic or asymmetric polarization over time in lithium metal and that it demonstrates very good intercalation and stability during the charge/discharge of graphite. The thermal and electrochemical stability of EC-LiTFSI31 gives a good performance and an outstanding stability of Gr//Li cell cycling at C/20 or C/10 up to 80 °C, during 5 months (100 cycles) without any damage to the battery. This original formulation could prove to be a promising electrolyte for Li-ion battery safety, which remains the main concern of industrialists in the field.

Comparing the Solid Electrolyte Interphases on Graphite Electrodes in K and Li Half Cells

In both Li-ion and K-ion batteries, graphite can be used as the negative electrode material. When potassium ions are stored electrochemically in the graphite host, the electrode capacities fade faster than in the lithium ion counterpart. This could be due to the high reactivity of the potassium metal counter electrode (CE) in half cells or a less stable solid electrolyte interphase (SEI) in the potassium case. Previous surface studies on graphite electrodes cycled in K half cells have focused on the SEI characteristics of different electrolyte formulations or different states of charge. In this study, we exploit the fact that graphite can store both lithium and potassium ions. Cell and component parameters have been largely maintained the same, with the only differences between Li and K half cells being the cation of the electrolyte salt and the alkali metal at the CE. The SEI layers formed under these conditions in either setup are studied using X-ray photoelectron spectroscopy with the aim to draw a direct comparison between the surface layers in both charged and discharged states. The results show a considerable crosstalk under OCV conditions between K-metal and the working electrode. Furthermore, the relative SEI layer composition after cycling varies considerably between Li and K half cells. Different dominant SEI species are present depending on the alkali metal used. The strong capacity fade observed in graphite–K half cells is likely linked to much smaller concentrations of inorganic compounds, such as KF, and increased amounts of organic compounds in the SEI.

Practical Prelithiation of 4.5 V LiCoO2 ||Graphite Batteries by a Passivated Lithium-Carbon Composite.

Prelithiation can replenish active Li into the battery to compensate the Li consumption due to the formation of solid electrolyte interphase (SEI) on the electrode surface, therefore improving the energy density of Li-ion batteries (LIBs), especially for batteries using electrode materials with low initial Coulombic efficiency (ICE). However, practical prelithiation in LIBs is a challenge since most lithiated compounds with high specific capacity are unstable and industrially incompatible. Herein, an effective prelithiation strategy is demonstrated by using a lithium-carbon (Li-C) microsphere composite. These Li-C microspheres are passivated by a self-assembled monolayer of octadecylphosphonic acid, which suppresses the reaction between Li and commonly used slurry solvent 1-methyl-2-pyrrolidinone (NMP). After the addition of passivated Li-C into the NMP-based graphite slurry, the ICE of the graphite||Li half-cell boosts from 88.5% to 100.5%. In a 4.5V LiCoO2 (LCO)||graphite full-cell, the supplementary Li source avoids excessive delithiation of LCO, thus suppressing the destructive phase transformation at high delithiation potential. As a result, the prelithiated LCO||graphite full-cell presents an initial discharge capacity of 201mAhg-1 and the capacity retention after 100 cycles increases by 7.1%. This work provides a practical approach for developing high energy density and long cycle life LIBs.

Electrochemical and transport properties of Te-doped Li4Ti5O12 as anode material for lithium-ion half/full batteries

Te-doped Li4Ti5O12 (LTO) was prepared by a ball milling-assisted solid-state method in air. The as-prepared powders were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and electrochemical impedance spectroscopy. Li4Ti4.95Te0.05O12 powder sintered at 850 °C presented improved ionic and electronic conductivities of 2.20 × 10-7 S·cm-1 and 2.40 × 10-9 S·cm-1 at room temperature, respectively, an order of magnitude higher than those of intrinsic LTO. Electrochemical analysis showed that the discharge specific capacities of Li4Ti4.95Te0.05O12 in Li half cells at 1 C and 5 C were 162.49 mAh·g-1 and 143.5 mAh·g-1, respectively, with capacity retention rates of 98.8% and 98.2% after 100 cycles. The Li4Ti4.95Te0.05O12/LiNi0.5Mn0.3Co0.2O2 full cells also showed a good specific capacity of 101.8 mAh·g-1 at 1 C and delivered good temperature adaptability. This study provides an effective strategy for the preparation of high-performance LTO anodes for lithium-ion batteries.

Enhancing Surface Chemical Stability of LiMn2 O4 Cathode by Strontium Enrichment at Grain Boundaries.

LiMn2 O4 (LMO) cathodes suffer from limited cycle life, resulting from Mn dissolution and side reactions between electrode and electrolyte. In this study, Sr-modified LMO is prepared by using a simple strategy. The nature and position of large-radius Sr ions are investigated, alongside their influence on the structural stability of the bulk. SrMnO3 (SMO) is found to be enriched at grain boundaries of LMO, with Mn-O-Sr bonds forming at the SMO/LMO interface. Furthermore, stable SMO alleviates the migration of Mn ions in LMO associated with structural integrity and suppresses side reactions between the electrode and electrolyte. The modified LMO cathodes maintain their structural integrity and display improved rate performance and cycling stability under harsh conditions. Remarkably, the discharge capacity of a Sr-modified LMO||Li half-cell maintains 94.8 % at 25 °C and 79.6 % at 55 °C after 500 cycles. Consequently, enrichment of strontium at grain boundaries presents a promising strategy for developing cathodes for long-term use.

Half and full cell researches of ternary MoS2/graphene/CNT aerogel compostie for enhanced lithium storage performances

Without using any templates, a ternary MoS2/graphene/carbon nanotubes (MoS2/GN/CNT) aerogel compostie is prepared by convenient hydrothermal synthesis method. The free-standing MoS2/GN/CNT aerogel can be cut directly as binder free electrodes in lithium-ion batteries. The MoS2/GN/CNT electrodes can hold as high as 695 and 579 mAh g−1 discharge capacities after 200 cycles at 200 mA g−1 in MoS2/GN/CNT//Li half cells and MoS2/GN/CNT//LiCoO2 full-cells, respectively. The strengthened electrochemical properities are owed by the thin GN/CNT layers and their jagged and wrinkled surfaces, which can enhance the composite conductivity and shorten the Li+ diffusion distance, as well as buffer the volume change of electrodes druing the charge-discharge cycles.

Electrochemical activation of a diatom-derived SiO2/C composite anode and its implementation in a lithium ion battery

Nano-architectured silica is extracted from algae harvested in the ocean. Its electrochemical properties are investigated as an anode material for lithium ion batteries. The beneficial effect of a carbon coating formed by pyrolysis of glucose at 850 °C in Ar(g) onto the surface of the SiO2 particles is demonstrated. The SiO2 and SiO2/C composites are characterized by means of SEM, EDX, XRD, FT-IR and Raman spectroscopy, TGA, gas sorption analysis and laser diffraction, in order to verify the structure, morphology and composition of the materials.A procedure for the electrochemical activation of SiO2- and SiO2/C-based electrodes in Li half cells is devised to fully maximize their utility as a host material for Li-ions. The activated SiO2/C composite reversibly delivers delithiation capacities of ≈800 mAhg−1 at 50 mAg−1 and ≈450 mAhg−1 at 2000 mAg−1 in a LiPF6‑carbonate electrolyte. The properties of an electrochemically activated, algae-derived silica-based electrode (SiO2/C) is investigated in a full cell configuration using a commercially available LiNi0.4Mn0.4Co0.2O2 (NMC442) cathode material. Such a cell operates at an average discharge voltage of 3 V while delivering capacities up to ≈150 mAhg−1 (NMC), which translate into a specific energy density of ≈390 mWhg−1, based on the active materials.

Vapor phase infiltration of ZnO quantum dots for all-solid-state PEO-based lithium batteries

Composite solid polymer electrolytes (CSPEs) have long been considered as one of the most promising candidates for all-solid-state lithium batteries owing to the merits of easy fabrication and low cost. However, the inorganic fillers physically mixed into the polymer matrix have weak polymer-filler interactions and tend to agglomerate, which limits the further improvement of the ionic conductivity and Li+ transference number of CSPEs. In this work, we demonstrated ZnO quantum dots can be chemically incorporated into the poly(ethylene oxide) (PEO) matrix by vapor phase infiltration (VPI), a special variant of atomic layer deposition (ALD). The ZnO quantum dots have strong chemical interactions with PEO polymer chains, which suppresses the crystallization of PEO and enhances the Li+ conduction. Due to the strong interactions, ZnO quantum dots distribute uniformly in the PEO-based solid electrolyte matrix as well as the top surface, which leads to a significant decrease of interfacial resistance with Li metal. As a result, the NCM811|Li half-cell with the VPI-ZnO/PEO/LiTFSI CSPE exhibit high discharge capacity at 50 ℃ (164.7 mAh g−1 at 0.5 C (1 C = 200 mA g−1), 2.8–4.25 V). This result could potentially serve as a model for a more general approach of using VPI to introduce strong polymer-filler interaction in CSPEs for high-performance lithium metal batteries.

Poly(arylene ether nitrile) porous membranes with adjustable pore size for high temperature resistance and high-performance lithium-ion batteries

In this study, flame-retardant poly(arylene ether nitriles) (PEN) porous membranes are prepared by nonsolvent induced phase separation method. Porous PEN membranes with adjustable morphology are obtained by controlling the Hildebrand solubility parameters between non-solvent and PEN. The obtained PEN porous membranes exhibit much higher porosity and electrolyte uptake compare with commercial separators owing to abundant interconnected pore structure in membranes. High thermal stability and flame retardant properties of PEN membrane ensure the high temperature security of lithium batteries. Especially, PEN-IPA membrane with three-dimensional interconnected dendritic network structure shows the best electrolyte affinity and the highest ionic conductivity (1.47 mS/cm). The LFP||Li half cells assembled with the PEN-IPA separator shows outstanding cycle and C rate performance at 85 °C, the discharge capacity retention of the cell was 86% after 100 cycles at 1 C. Our research reveals the role of the cyano groups in the lithium-ion batteries separator and the relationship between morphology and performance of PEN porous membranes for lithium-ion batteries, which provides a facile and effective approach for preparing the promising separators with adjustable pore size, high temperature resistance and high performance for lithium-ion batteries.

Oxygen defected T-Nb2O5-x confined in necklace-like N-doped carbon fibers for Li+/Na+ capacitor

Optimizing the transmission dynamics and stability of orthorhombic (T-) Nb 2 O 5 is the development direction of hybrid supercapacitors. In this work, Necklace-like T-Nb 2 O 5-x @NC assembled by Yolk-Shell nanosphere is applied for self-supporting anode of the Li + /Na + capacitor. Each Yolk-Shell T-Nb 2 O 5-x @NC unit effectively alleviates the volume effect of Nb 2 O 5 during Li + /Na + embedding repeatedly, thus achieving good structural stability. In addition, oxygen vacancy optimizes the transmission barrier of Li + /Na + and its conductivity. T-Nb 2 O 5-x @NC units are stringed along the carbon fibers, which are further interconnected to form integrated 3D conductive network for excellent electron conductivity. As a result, T-Nb 2 O 5-x @NC-7, as the optimal sample, has high specific capacity (up to 208.3 mAh g −1 at 0.1 A g −1 in Li half-cell) and long cycle life (92.3% after 2000 cycles in Li capacitor). Also, it exhibits superior electrochemical performance in Na energy storage (84.2% after 2000 cycles). • Yolk-shell structure greatly relieved the volume expansion effect. • Oxygen vacancy reduces the ion transport barrier. • The independent unmatched electrons generated optimize its conductivity. • Carbon interconnected network improves electron conductivity.

Realizing Compact Lithium Deposition via Elaborative Nucleation and Growth Regulation for Stable Lithium-Metal Batteries.

Metallic lithium (Li) has been regarded as an ideal candidate for anode materials in next-generation high-energy-density batteries. However, a ubiquitous spongy Li deposition results in low reversibility, huge interfacial impedance, and even safety issues, hindering its practical application. Herein, we proposed a bifunctional electrolyte (BiFE) to avoid the spongy Li deposition, in which lithium nitrate (LiNO3) facilitates a uniform granular Li nucleation via forming a kinetically favorable solid electrolyte interphase and silicon dioxide (SiO2) adsorbs anions to stabilize the electric field distribution near the electrode surface. Such a BiFE provides an even Li+ ion flux for the subsequent growth of electrochemical Li deposition, which was verified by ζ potential, Raman spectra, and specific capacitance characterizations, thus realizing a compact and uniform Li deposition via elaborative nucleation and growth regulation. An improved Li Coulombic efficiency of 99.1% can be achieved within BiFE. When used in Cu∥Li half-cells and Li∥Li symmetric cells, the high Li utilization prolonged the cycling life span to above 300 cycles and 1200 h, respectively. The compact Li deposition also resisted the corrosion of polysulfides to enhance the cycling performance of Li∥S full cells.

On the beneficial effect of rutile TiO2 to improve electrochemical performance of Li4Ti5O12 at low-potential intercalation

Li4Ti5O12/TiO2 composite, pure Li4Ti5O12 and Li4Ti5O12/Li2TiO3 composite are synthesized through a high temperature solid-state approach by adjusting the molar ratio of Li/Ti precursors. Pure Li4Ti5O12 can be obtained when the molar ratio of Li/Ti precursor materials is 0.80, while low and over stoichiometric ratio of Li4Ti5O12 would lead to the formation of the second phase of rutile TiO2 and Li2TiO3, respectively. The electrochemical performance of the obtained materials as anode materials for Li-ion batteries is tested under potential range of 0.02–2.5 V in Li half-cell. The results show that all the samples exhibit two potential plateaus at ~1.5 V and ~0.75 V at various C-rate. Among the obtained samples, Li4Ti5O12/TiO2 composite exhibits the best cycling stability and rate capability. The second phase TiO2 facilitates the diffusion of Li+ and significantly enhances the rate capability.

Understanding the Electrochemical Performance of Hybrid Na(2-x)LixFeP2O7 (x= 0, 0.6) Cathode Materials

The need for green energy is increasing every year, and renewable energy and efficient storage require large-scale lithium-ion batteries (LIBs). The use of LIBs has resulted in declining lithium (Li) reserves, which effectively increases the cost of current LIBs. Na ion batteries (NIBs) have been proposed as an alternative to the LIBs as it displays similar properties to them. However, Na ions (Na+), possessing higher ionic radii, and lower energy density than Li ion (Li+), the NIBs have limited commercialization potential. One proposed solution is the development of hybrid cathodes, where the cathode has both Li+ and Na+ in the structure and can be active in both Li and Na cells. The current work describes the development of hybrid cathode material in which the substitution of Li+ for Na+ in the configuration of Na(2-x)LixFeP2O7 (x=0,0,6) is considered to form Na1.4Li0.6FeP2O7 cathodes. The solid-state technique was used for the synthesis of Na(2-x)LixFeP2O7 (x=0.6) cathode. Structural analysis indicates the formation of phase pure crystalline materials with non-uniform and sub-micron particles. It is also noticed that the original triclinic structure of Na2FeP2O7 is preserved with the substitution of Li+. It is also revealed that Na1.4Li0.6FeP2O7 shows improved thermal stability up to 550°C when compared to Na2FeP2O7. The electrochemical performance of Na2FeP2O7 and Na1.4Li0.6FeP2O7 is investigated using various electrochemical characterizations. Both Li and Na half cells show electrochemical activity for Na1.4Li0.6FeP2O7 with decent cyclability. However, Na1.4Li0.6FeP2O7, suffers from lower electrochemical efficiency when compared to Na2FeP2O7. This could mainly be due to the lattice distortion upon substituting larger Na+ ions with smaller Li+ ions. Nevertheless, Na1.4Li0.6FeP2O7 hybrid cathode material can be used as a reference to synthesize new cathode materials with improved efficiency.

On the Electrochemical Phase Evolution of Anti-PbO-Type CoSe in Alkali Ion Batteries

The reaction mechanism of anti-PbO type CoSe in Li, Na, and K ion half cells is studied. Ex situ X-ray diffraction data is analyzed with the Rietveld method, in conjunction with discharge profiles and extended cycling data. These indicate that intercalation followed by a conversion reaction occur in all systems. For the case of Na, the intercalation reaction was associated with a contraction in the stacking axis lattice parameter, whereas Li and K exhibited expansion. Magnetic susceptibility versus temperature measurements of Li- and Na-intercalated CoSe samples produce unusual results, and several explanations are proposed, including the formation of a superconductive phase. Extended cycling experiments are also performed, and high initial capacities of 937, 657, and 972 mAh/g are observed for Li, Na, and K, respectively. However, all systems exhibit significantly lower second discharge capacities of 796, 530, and 515 mAh/g. The capacities continue to decline during extended cycling, with the systems exhibiting tenth cycle capacity fades of 52, 85, and 95% and Li half cells exhibit capacities over 150 mAh/g at 15 mA/g after 50 cycles. The capacity fade is likely attributable to volume changes and irreversibility associated with conversion and intercalation reactions. This work correlates electrochemical features to the structural evolution, magnetic properties, and reaction mechanisms.

Dendrite-Suppressing Separator with High Thermal Stability Modified by Beaded-Chain-Like Polyimide Coating for a Li Metal Anode

Dendritic Li growth is the root hurdle against the implementation of a Li metal anode because it brings safety issues and unsatisfactory efficiency. In this work, a beaded-chain-like polyimide (PI) coating is designed on the commercial polyethylene (PE) separator to suppress the Li dendrite. Owing to the compactly stacking structure and high Li-ion absorption of the PI coating, the wettability of the prepared PI-PE separator is improved and a Li-ion-rich layer with uniform Li-ion transfer channels forms on the surface of the Li metal anode. Therefore, the planar Li deposition rather than dendrite growth has been achieved using this custom separator. The life spans of Cu||PI-PE||Li half-cells have been extended to 7 and 4 times longer than that of Cu||PE||Li half-cells at a current density of 1 mA/cm2 with deposition capacities of 0.5 and 1 mA h/cm2, respectively. Besides suppressing Li dendrites, the multifunctional PI-PE separator also delivers a higher thermal stability to 120 °C than commercial PE and Al2O3-PE separators. This facile approach provides a feasible strategy to realize smooth lithium deposition, and the fundamental mechanism underlying the combination of pore structure and surface chemistry may lead to new approaches to tackle the dendritic problem of Li deposition.

Circumventing chemo-mechanical failure of Sn foil battery anode by grain refinement and elaborate porosity design

Tin (Sn) metal foil is a promising anode for next-generation high-energy–density lithium-ion batteries (LIBs) due to its high capacity and easy processibility. However, the pristine Sn foil anode suffers nonuniform alloying/dealloying reaction with lithium (Li) and huge volume variation, leading to electrode pulverization and inferior electrochemical performance. Herein, we proposed that reduced grain size and elaborate porosity design of Sn foil can circumvent the nonuniform alloy reaction and buffer the volume change during the lithiation/delithiation cycling. Experimentally, we designed a three-dimensional interconnected porous Sn (3DIP-Sn) foil by a facile chemical alloying/dealloying approach, which showed improved electrochemical performance. The enhanced structure stability of the as-fabricated 3DIP-Sn foil was verified by chemo-mechanical simulations and experimental investigation. As expected, the 3DIP-Sn foil anode revealed a long cycle lifespan of 4400 h at 0.5 mA cm−2 and 1 mAh cm−2 in Sn||Li half cells. A 3DIP-Sn||LiFePO4 full cell with LiFePO4 loading of 7.1 mg cm−2 exhibited stable cycling for 500 cycles with 80% capacity retention at 70 mA g−1. Pairing with high-loading commercial LiNi0.6Co0.2Mn0.2O2 (NCM622, 18.4 mg cm−2) cathode, a 3DIP-Sn||NCM622 full cell delivered a high reversible capacity of 3.2 mAh cm−2. These results demonstrated the important role of regulating the uniform alloying/dealloying reaction and circumventing the localized strain/stress in improving the electrochemical performance of Sn foil anodes for advanced LIBs.

Electrospun MOF/PAN composite separator with superior electrochemical performances for high energy density lithium batteries

A composite separator is prepared with polyacrylonitrile (PAN) and metal-organic framework (MOF) particles by electrospinning, and its physical properties, battery performances and the mechanism of how it improves the performance of high energy density lithium battery are studied. The MOF/PAN separator shows an outstanding thermal stability, an ultra-high electrolyte uptake (794±30%), a high ionic conductivity (2.83 mS cm−1 at 25 °C) and a wide electrochemical window (5.2 V vs. Li+/Li). The Li||separator||Li half-cell can operate stably for 1000 h at 5 mA cm−2. A strong electrostatic interaction between MOF and PF6- in the electrolyte inhibits movement of the anions and enhances the Lithium-ion transference number (tLi+) up to 0.74, which is 64.4% higher than that of PAN separator. After 200 cycles at 0.2 C, the interfacial resistance between separator and electrode only increases from 22.00 to 30.58 Ω. The initial discharge capacity of the NCM811||10% MOF/PAN separator||Li battery system is 166.3 mAh g−1 with 81.3% capacity retention after 250 cycles at 5 C. This research offers an idea to design MOF-based composite separator that makes NCM811||Li battery outstanding in electrochemical stability and high rate performance.

Polymer-ceramic composite electrolytes for all-solid-state lithium batteries: Ionic conductivity and chemical interaction enhanced by oxygen vacancy in ceramic nanofibers

Perovskite Li3x La2/3−x TiO3 (LLTO) nanofibers have been heat-treated in the hydrogen-containing atmosphere and then incorporated with the poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) polymer to form a composite electrolyte. Hydrogen treatment has created oxygen vacancies in the LLTO nanofibers, which has reduced the activation energy of Li ion transport along intra-grains and inter-grains, leading to an improvement in the ion conductivity of LLTO nanofibers. Hydrogen treatment of the LLTO nanofibers has also enhanced the chemical interaction between the LLTO nanofibers and the polymer matrix in the composite electrolyte, and favored the Li ion transport at the nanofiber/polymer interface, improving the ion conductivity of the composite electrolyte to 3.4 × 10−4 S/cm at room temperature. As a result, the Li|composite-electrolyte|Li half-cell exhibits good stability during lithium plating/stripping cycling at room temperature, showing an overpotential of ~91 mV at a constant current density of 0.5 mA/cm2. The full-cell battery with the composite electrolyte, lithium metal anode and lithium iron phosphate cathode shows excellent rate capacity and cycling performance.