Movement Of Lithium Ions Research Articles

Solid-state lithium-sulfur battery chemistries achieving excellent room-temperature cycle performance by high-quality Li7La3Zr2O12-based electrolyte

The ceramic materials based on Li6.375La3Zr1.375Nb0.625O12 (LLZNO) with the LiX (XF, Cl, Br) additive have been prepared through the traditional solid−state sintering reaction. The phase evolution of solid-state electrolytes was studied using the X − ray diffraction (XRD) and Raman spectroscopy which confirmed that all prepared samples formed the cubic garnet-type structure. Also, the lattice distortion based on X− doping at partial O2− sites have been detected in the LLZNO by the XRD data. It was worth noting that, according to the observation of scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), the electrolytes were joint occurrence of anion (F−, Cl−, Br−) doping at LLZNO grains and lithiated interface at grain boundaries, thereby leading to the high densification and the excellent wetting. Therefore, the ionic conductivity and transport kinetics of ceramics were obviously improved after LiX (X = F−, Cl−, Br−) incorporation. Meanwhile, LiX addition into LLZNO sample can be conductive to the interfacial contact and lithium-ion movement between the electrode and the electrolytes. Additionally, a transition layer was introduced to further provide a stable contact with Li electrode. The Li| LLZNO/LiCl-Ag interface resistance decreases to 98.2 Ω cm2. The symmetric Li| LLZNO/LiCl-Ag |Li battery can cycle stably for 600 h at 0.2 mA cm−2 and room temperature without a short circuit. Moreover, the Li| LLZNO/LiCl |sulfur-carbon battery exhibited a capacity of 750mAh g−1 after 120th cycle at 0.2 C and room temperature, while maintaining the high coulombic efficiency (over 99.5%) and excellent cycling stability. These results indicate that the LLZNO/LiX ceramics are promising for the production of electrolyte and fabrication of lithium-sulfur batteries.

Stable cycling of high-density three-dimensional sintered LiCoO2 plate cathodes

High-density sintered plate-type cathodes composed of only an active material can achieve a high energy density of lithium-ion batteries (LIBs) beyond the current state of the art. However, slow lithium ion movement in the solid-state cathode plate and deterioration of the grain boundary of sintered cathodes over many charge/discharge cycles are obstacles to commercialization. Herein, we present a new three-dimensional high-density sintered LiCoO2 plate cathode with periodically aligned channels, which enable fast charging/discharging of high-energy-density LIBs. In addition, we investigate the grain-boundary cracking mechanism and introduce a conductive coating agent to LiCoO2 cathodes that prevents crack propagation, enhances electron transfer between sintered LiCoO2 grains, and prevents the formation of an undesirable cathode electrolyte interphase. In full-cell experiments, the cell with a sintered LiCoO2 cathode with industrial-level current density (3.5 mA cm−2) has a volumetric capacity (723 mAh cm−3) 21% higher than that of a conventional cathode (597 mAh cm−3). The cathode coated with the conductive agent shows a 30% higher cycle life after testing for 500 cycles compared to the bare cathode. High-density sintered cathodes are fabricated with an industrially acceptable cycle lifetime of 84% capacity retention over 500 cycles at 1 C.

Research progress of lithium-ion battery separator

As one of the inner layer components of lithium-ion batteries, the separator plays the role of blocking the positive and negative electrodes and providing channels for the movement of lithium ions. This chapter mainly expounds the use and performance characteristics of lithium-ion battery separators, the research progress of the three most widely used lithium battery separators, and systematically analyzes the characteristics of various thin-film materials, as well as the current four major processes for preparing separators: dry and wet. Method, centrifugal spinning method, electrospinning method, etc., and the future development direction of lithium-ion battery separator is prospected.

Metal Nitrate Embedded Polymeric Interlayer for Improving Cycling Stability of Li Metal Anode

Among secondary batteries using lithium, the use of lithium metal anodes for high capacity has become a hot topic. However, in lithium metal anodes, there is a major problem of dendritic growth and research are actively underway to address the issue. And it is reported that it is possible to improve the stability of Li metal anode by facilitating the movement of lithium ions through various additives to suppress dendritic growth and to make robust and stable SEI layer. To address the issue of dendritic growth of Li, using cesium nitrate is selected to improve the stability of the anode based on a mechanism by which a nitrogen-rich compounds lithiophilic to transport Li ion uniformly are formed in the SEI layer. And also the cesium element induces an cation electrostatic shielding effect while lithium metal is deposited and grown in the anode. In addition, since metal nitrates have very low solubility in carbonate-based electrolytes, polymer nanofiber-interlayer is synthesized by electrospinning to support metal nitrate and supply nitrate continuously and stably, while interlayer does not interfere with the movement of lithium ions through the nanofiber layer. In summary, a metal nitrate embedded polymer nanofiber layer is synthesized through an electrospinning method, then stabilization of a lithium surface and stability of a lithium metal anode are obtained by using an intermediate layer, and a relationship between an additive and SEI formation is identified at a limited solubility in carbonate electrolytes. The study result demonstrates that the lifetime of symmetric Li-Li cells and full cell with LCO cathodes improved greatly. And the deposition morphology of Li become dendrite-free and more uniform.

New UV-initiated lithiated-interpenetrating network gel-polymer electrolytes for lithium-metal batteries

A new lithiated-interpenetrating network gel-polymer electrolytes (LIPN-GPEs) is designed and fabricated by ultraviolet-irradiation radical polymerization. The LIPN-GPEs includes both cross-linked poly (lithiated 2-acrylamido-2-methylpropane sulfonic acid-co-polyethylene glycol acrylate) matrix C–P(AMPSLi-MPEGA) and polyacrylonitrile (C-PAN), which forms the interpenetrating framework. The interpenetrating network ensures the mechanical strength and flexibility that eliminates volume changes of lithium anode during lithium deposition/stripping process. Meanwhile, the LIPN-GPEs with better self-supporting nature and high ionic conductivity (2.5 × 10−3 S/cm) can promote the movement of lithium ion resulting in more uniform distribution, which realizes uniform lithium deposition with stable SEI composition. Therefore, the LIPN-GPEs indicates excellent interfacial stability towards lithium anode. Symmetrical lithium metal cell yields low overpotential of 50 mV over 4000 h at 0.5 mA cm−2. The LIPN-GPEs with optimized ratio exhibits wider electrochemical window (5.06 V vs. Li/Li+) at ambient temperature, which also possesses unexceptional thermal stability with decomposition temperature up to 400 °C. Especially, when assembled with high-voltage cathode LiCoO2 (LCO) and LiNi0.5Co0.2Mn0.3O2 (NCM523) as coin cells, the LIPN-GPEs reveals cycling performance, reflecting good high-voltage resistance characteristic. This work testifies that LIPN-GPEs through a convenient ultraviolet-irradiation radical polymerization provides a candidate for lithium metal battery, which furnishes application prospects in wearable devices.

Last developments in polymers for wearable energy storage devices

Last developments in polymers for wearable energy storage devices

Stable cellulose-separator with CaO on nanoporous polypropylene by water-treated channels

In this study, a stable battery separator was prepared to solve the thermal stability problem of lithium-ion batteries. A cellulose acetate (CA) and CaO composite solution was prepared, and a separator with improved stability was completed by coating it on polypropylene (PP). The added calcium oxide interacts with the carbonyl groups of CA to cause a crosslinking effect and at the same time to form the pores. By applying physical pressure based on water-molecules using a water treatment device, the pores of the two polymers (CA and PP) were partially connected, and interaction between the PP and the CA films was induced. The average water flux data and porosity for the separator were 208 L/m 2 h and 68.8%. The decomposition temperature increased by about 60 °C compared to pure CA. When this is used as a separator for a lithium-ion battery, its high porosity and thin thickness can enhance the charging efficiency and enable the fast lithium-ion movement. • Interconnection of cellulose separator with nanoporous polypropylene. • Enhanced stability by calcium oxide on polypropylene for separator. • Water-treated channels for interconnection through two polymers.

Tuning of composition and morphology of LiFePO4 cathode for applications in all solid-state lithium metal batteries

All solid-state rechargeable lithium metal batteries (SS-LMBs) are gaining more and more importance because of their higher safety and higher energy densities in comparison to their liquid-based counterparts. In spite of this potential, their low discharge capacities and poor rate performances limit them to be used as state-of-the-art SS-LMBs. This arise due to the low intrinsic ionic and electronic transport pathways within the solid components in the cathode during the fast charge/discharge processes. Therefore, it is necessary to have a cathode with good electron conducting channels to increase the active material utilization without blocking the movement of lithium ions. Since SS-LMBs require a different morphology and composition of the cathode, we selected LiFePO4 (LFP) as a prototype and, we have systematically studied the influence of the cathode composition by varying the contents of active material LFP, conductive additives (super C65 conductive carbon black and conductive graphite), ion conducting components (PEO and LiTFSI) in order to elucidate the best ion as well as electron conduction morphology in the cathode. In addition, a comparative study on different cathode slurry preparation methods was made, wherein ball milling was found to reduce the particle size and increase the homogeneity of LFP which further aids fast Li ion transport throughout the electrode. The SEM analysis of the resulting calendered electrode shows the formation of non-porous and crack-free structures with the presence of conductive graphite throughout the electrode. As a result, the optimum LFP cathode composition with solid polymer nanocomposite electrolyte (SPNE) delivered higher initial discharge capacities of 114 mAh g-1 at 0.2C rate at 30 °C and 141 mAh g-1 at 1C rate at 70 °C. When the current rate was increased to 2C, the electrode still delivered high discharge capacity of 82 mAh g-1 even after 500 cycle, which indicates that the optimum cathode formulation is one of the important parameters in building high rate and long cycle performing SS-LMBs.

LLCZN/PEO/LiPF6 Composite Solid-State Electrolyte for Safe Energy Storage Application

All-solid-state batteries (ASSBs) are gaining traction in the arena of energy storage due to their promising results in producing high energy density and long cycle life coupled with their capability of being safe. The key challenges facing ASSBs are low conductivity and slow charge transfer kinetics at the interface between the electrode and the solid electrolyte. Garnet solid-state electrolyte has shown promising results in improving the ion conductivity but still suffers from poor capacity retention and rate performance due to the interfacial resistance between the electrodes. To improve the interfacial resistance, we prepared a composite consisting of Li7La2.75Ca0.25Zr1.75Nb0.25O12 (LLCZN) garnet material as the ceramic, polyethylene oxide (PEO) as the polymer, and lithium hexafluorophosphate (LiPF6) as the salt. These compounds are mixed in a stoichiometric ratio and developed into a very thin disc-shaped solid electrolyte. The LLCZN provides a lithium-ion transport path to enhance the lithium-ion conduction during charging and discharging cycles, while the LiPF6 contributes more lithium ions via the transport path. The PEO matrix in the composite material aids in bonding the compounds together and creating a large contact area, thereby reducing the issue of large interfacial resistance. FESEM images show the porous nature of the electrolyte which promotes the movement of lithium ions through the electrolyte. The fabricated LLCZN/PEO/LiPF6 solid-state electrolyte shows outstanding electrochemical stability that remains at 130 mAh g−1 up to 150 charging and discharging cycles at 0.05 mA cm−2 current. All the specific capacities were calculated based on the mass of the cathode material (LiCoO2). In addition, the coin cell retains 85% discharge capacity up to 150 cycles with a Coulombic efficiency of approximately 98% and energy efficiency of 90% during the entire cycling process.

Development of impedance measurement of lithium ion batteries electrode using terahertz chemical microscope

AbstractIn recent years, with the spread of electric vehicles, improvement in the performance of lithium ion batteries has been required. Evaluation of the active material is important because the performance of the lithium ion battery is affected by the movement of lithium ions at the electrode active material‐electrolyte interface. In this study, we fabricated a lithium ion battery with the sensing plate, which is a potential sensor, attached to the positive electrode, and evaluated lithium ion battery with a terahertz chemical microscope (TCM). As a result, we succeeded in measuring the potential distribution of the positive electrode during charging and discharging, and the local impedance.

Enhanced Cycling Life of a Three Dimensional LiCoO2 Sintered Electrode for Li-Ion Batteries

The exploding growth of the portable electronic devices requires a high energy density battery. To meet this demand, the energy density of the conventional LIB is insufficient. The active material density in the conventional LIB electrode is limited to an amount of 3.8g / cc because the conducting agent and the binder are included in a considerable amount ( > 3%). Various studies are being conducted to improve energy density. Among them, research for removing conductive materials and binders from the cathode and to maximize electrode density through sintering is one of the most important candidates. This is because the density can be improved to 4.5 g / cc through sintering process. That way, energy density can be increased by 20%. In addition, unlike the existing jellyroll type, using the sintered LiCoO2 electrode, various shapes and thicknesses of batteries can be produced. However, there is a problem that the movement of lithium ion in the cathode should be made within the solid state active material. Since ions are much slower in solid state than in the liquid state, the sintered cathode has a fatal disadvantage that it is vulnerable to high rate characteristics. In addition, cracking in the grain boundary in the layered cathode deteriorates the cycle life performance.In this research, we propose a method to improve a cycle life of Li ion batteries with three dimensional LiCoO2 sintered electrode. We suggest the mechanism for the internal crack propagation of the sintered cathode, and suggest to mitigate the crack propagation by a conductive bonding agent. The conductive bonding agent formed a conductive path inside the cathode so that electrons could move even in a crack. The cathode showed a 130% improved cycle performance with a high current density of 3.0 mA/cm2. The study was the first to prove the performance of cycle life of the 3D sintered cathode in fullcell configuration, and it is meaningful in that it mitigates the deterioration caused by internal crack propagation, which is a problem that must be solved in order to apply the sintered cathode to the industrial level. In the commercialization of smaller, higher capacity and longer cycle life batteries using sintered cathodes, we hope the concepts proposed in this study will help.

Increasing the Lithium Ion Mobility in Poly(Phosphazene)-Based Solid Polymer Electrolytes through Tailored Cation Doping

Solid polymer electrolytes (SPEs) are promising candidates for usage in rechargeable lithium metal batteries (LMBs) as they possess high mechanical, thermal, and chemical stability. However, the poor ionic conductivity of SPEs in comparison to liquid electrolytes hampers the commercialization of SPE-based LMBs. In the case of poly[bis(methoxy-ethoxy-ethoxy-)phosphazene] (MEEP), one explanation for the low ionic conductivity is the trapping of lithium cations in backbone coordination sites, hindering lithium ion movement through the electrolyte membrane. Herein, modelling the ion coordination in MEEP using DFT calculations reveals that, compared to lithium, heavier alkali cations are more likely to be complexed at the backbone coordination sites. With other alkali cations masking these coordination sites, enhanced lithium ion mobility through the SPE is expected. Experimental data proves these expectations: doping MEEP-based LiBOB-containing SPE membranes with small amounts of in-house synthesized potassium bis(oxalato)borate (KBOB) increases the lithium ion transference number from 0.08 to 0.18. Also, the partial lithium ion conductivity of the salt-in-MEEP electrolyte is boosted to outstanding 0.08 mS cm−1, far exceeding state-of-the-art literature values for this material. A cross-check using SPEs based on the structurally similar poly(ethylene oxide) (PEO) validates the proposed cation displacement model. The obtained insights may aid the development of highly effective poly(phosphazene)-based SPEs.

Theoretical investigation on lithium battery material with improved light-harvesting performance

Dye-sensitized photo-batteries employ dye molecules to photo-charge lithium-based batteries via utilizing the inexhaustible solar energy. In this manuscript, we reveal the atomistic structures and optoelectronic properties of the representative dye-sensitized photo-battery electrode material based on N719/LiFePO4 via first-principles calculations. Both tridentate and bidentate anchoring modes are available in the hybrid systems stabilized by the O···Li, H···O and S···Li interactions. The lithium ions are displaced from the LiFePO4 surface upon the dye adsorption, which is proposed to benefit the light-driven lithium ion movement in the photo-charging process. The band gap of the LiFePO4-based surface system reduces by 90% upon the dye adsorption, leading to a semi-metallic character that is associated with the decent electric conductivity. The Mulliken and Hirshfeld charges indicate the electron accumulation in the substrate, suggesting the electron flow from the dye to the substrate to stabilize to overall structure. This study facilitates the fundamental understanding on the dye-sensitized lithium battery materials and expects the integration of more dye-sensitized solar cell-active dyes and lithium battery materials for the light-weight photo-rechargeable battery application.

Effect of Residual Trace Amounts of Fe and Al in Li[Ni1/3Mn1/3Co1/3]O2 Cathode Active Material for the Sustainable Recycling of Lithium-Ion Batteries.

As the explosive growth of the electric vehicle market leads to an increase in spent lithium-ion batteries (LIBs), the disposal of LIBs has also made headlines. In this study, we synthesized the cathode active materials Li[Ni1/3Mn1/3Co1/3]O2 (NMC) and Li[Ni1/3Mn1/3Co1/3Fe0.0005Al0.0005]O2 (NMCFA) via hydroxide co-precipitation and calcination processes, which simulate the resynthesis of NMC in leachate containing trace amounts of iron and aluminum from spent LIBs. The effects of iron and aluminum on the physicochemical and electrochemical properties were investigated and compared with NMC. Trace amounts of iron and aluminum do not affect the morphology, the formation of O3-type layered structures, or the redox peak. On the other hand, the rate capability of NMCFA shows high discharge capacities at 7 C (110 mAh g−1) and 10 C (74 mAh g−1), comparable to the values for NMC at 5 C (111 mAh g−1) and 7 C (79 mAh g−1), respectively, due to the widened interslab thickness of NMCFA which facilitates the movement of lithium ions in a 2D channel. Therefore, iron and aluminum, which are usually considered as impurities in the recycling of LIBs, could be used as doping elements for enhancing the electrochemical performance of resynthesized cathode active materials.

Ether-containing polycarbonate-based solid polymer electrolytes for Dendrite-Free Lithium metal batteries

Lithium metal is considered an ideal anode material for next-generation high-energy-density batteries, owing to its high theoretical specific capacity and low reduction potential. However, the uncontrolled growth of Li dendrites during cycling has limited its industrial application. In this work, a poly (allyl diglycol carbonate)-based solid polymer electrolyte (PADC-SPE) combining the advantages of polyether and polycarbonate-based solid electrolytes was prepared by in-situ polymerization. According to space charge theory, the uniform free movement of lithium ions in the electrolyte can prevent electric field generation at the anode surface, facilitating the safe and ordered deposition of lithium ions. Therefore, PADC-SPE exhibited excellent ionic conductivity (1.96 × 10−5 S cm−1), a wide electrochemical window (5.5 V), and a high Li-ion transference number (t+ = 0.67) at room temperature. Surprisingly, a smooth surface was observed for the Li anode of Li/Li cells after constant-current charge–discharge cycling for 800 h. A LiFePO4/PADC–SPE/Li battery showed excellent high-temperature (60 °C) cycling performance, with a discharge specific capacity reaching 145.1 mAh g−1 at 0.3C and retaining 99.2% of its first-cycle value after 110 cycles. Based on this excellent performance, PADC-SPE represents a promising system for developing safe and high-performance Li metal batteries.

Electrochemical and Pseudocapacitive Analysis of Rod-Like MoO2@MoSe2@NC Heterostructures for High-Performance Lithium Ion Batteries

A micro-scale rod-like heterostructure derived from molybdenum-based metal organic framework (Mo-MOF) has been successfully prepared via subsequent annealing treatment, which assembled from N-doped carbon encapsulated MoSe2 nanosheets grown on the surface of MoO2 microrod (named as MoO2@MoSe2@NC). For this novel heterostructure, the MoO2 nanoparticles assembled into rod core not only serve as supporting substrate for facilitating the fast kinetics of Li+ cations inside the electrode but also protect the MoSe2 structure from restacking in the charge/discharge process. Moreover, the outer-layered MoSe2 nanosheets enable the fast lithium ion movement owing to its large interlayer spacing. Moreover, this unique rod-like core–shell structure composite could further effectively alleviate the structural strains caused by large volume expansion during charge/discharge process, thus leading to stable electrochemical performance when evaluated as anode material for lithium ion batteries. Electrochemical testing exhibits that the MoO2@MoSe2@NC heterostructure presents highly reversible capacity of 468 mAh g−1 at 0.5 A g−1 and superior rate capability (318 mAh g−1 even at 5.0 A g−1), which is attributed to the synergistic effect of N-doped carbon encapsulated MoSe2 nanosheets and MoO2 nanoparticles.

Theoretical investigation on interactions between lithium ions and two-dimensional halide perovskite for solar-rechargeable batteries

Two-dimensional (2D) halide perovskite materials have recently been proposed for solar energy conversion and energy storage systems, namely, photo-rechargeable batteries. However, the theoretical understanding of the 2D halide perovskite materials for the photo-rechargeable batteries lags behind the experimental advancement. In this manuscript, we investigate the adsorption and transport properties of lithium ions on an experimentally verified 2D halide perovskite material, (C6H9C2H4NH3)2PbI4, via first-principles calculations. Our study reveals the efficient adsorption and transport properties of the lithium ion at the 2D lead halide perovskite surface, and demonstrates the prospects of the metal halide perovskite system as an effective anode material for lithium-ion batteries as well as the photo-charging medium for photo-rechargeable batteries. In addition, the interlayer diffusion of the lithium ions is calculated, which demonstrates the efficient transport of the lithium ions between the 2D halide perovskite layers that contribute to the most of capacity. Most importantly, the displacement of the lithium ion is demonstrated to be available upon the hole polaron formation, which is suggested to signify the photo-charging behaviour initiating the unidirectional lithium ion movement on the electrode surface. The present study for the first time rationalizes the photo-charging behaviour of the photo-rechargeable battery, and facilitates the fundamental understanding on the halide perovskites for the energy storage applications including the lithium-ion batteries and the photo-rechargeable batteries.

Health monitoring of mechanically fatigued flexible lithium ion battery by electrochemical impedance spectroscopy

For reliable applications of flexible lithium ion batteries, the states of mechanically fatigued batteries were evaluated by applying electrochemical impedance spectroscopy (EIS). The EIS resistance of the batteries increased with mechanical fatigue, and this tendency was more distinct for the battery in the charged state. The EIS resistance of the fatigued battery was unstable and fluctuated during subsequent storage time after fatigue. Capacity degradation of the fatigued battery was about three times faster than that of the as-received one. By scanning electron microscopic observation of the dissembled electrode materials, root causes of the observed faster degradations were attributed to lithium metal precipitation on the carbon negative electrode as well as collapse of lamellar structures of the polymer separator (i.e., blockage of micro pores for lithium ion movement.)

Dynamic imaging of lithium in solid-state batteries by operando electron energy-loss spectroscopy with sparse coding

Lithium-ion transport in cathodes, anodes, solid electrolytes, and through their interfaces plays a crucial role in the electrochemical performance of solid-state lithium-ion batteries. Direct visualization of the lithium-ion dynamics at the nanoscale provides valuable insight for understanding the fundamental ion behaviour in batteries. Here, we report the dynamic changes of lithium-ion movement in a solid-state battery under charge and discharge reactions by time-resolved operando electron energy-loss spectroscopy with scanning transmission electron microscopy. Applying image denoising and super-resolution via sparse coding drastically improves the temporal and spatial resolution of lithium imaging. Dynamic observation reveals that the lithium ions in the lithium cobaltite cathode are complicatedly extracted with diffusion through the lithium cobaltite domain boundaries during charging. Even in the open-circuit state, they move inside the cathode. Operando electron energy-loss spectroscopy with sparse coding is a promising combination to visualize the ion dynamics and clarify the fundamentals of solid-state electrochemistry.

A solid polymer electrolyte containing a novel lithium borate salt for all-solid-state lithium-ion batteries

We prepared a solid polymer electrolyte (SPE) composed of a lithium borate salt and a polymer matrix, which can be employed for all-solid-state lithium-ion batteries. The lithium borate salt was made from lithium cations and bis (maleic acid) borate anions, and exhibits an excellent thermal stability as well as high ionic conductivity. The polymer matrix is an amorphous polymeric material having no crystalline regions, which is beneficial for the movement of lithium ions in the SPE. The polymer matrix also has good mechanical performance and thermal stability. Moreover, the SPE also has a relatively high ionic conductivity.