Movement Of Li Ion Research Articles

Enhanced structural stability of Si electrode employing TiNi/Si pillars with oriented Li diffusion pathway

As the anode materials of Li-ion batteries, pillar-shaped TiNi/Si particles fabricated by employing electrochemical etching of (100) Si wafers and TiNi alloy coating, were investigated for their structural and electrochemical properties. The most suitable porous wafer for producing Si pillars was obtained at a current density of 2.5 mA/cm2 during etching. The deposited TiNi alloy film consisted of a crystallized austenitic (B2) phase capable of inducing phase transformation through annealing at 500°C. Particularly, by coating with the inactive materials, only the (100) plane of single crystalline Si was exposed during the initial charging process to restrict Li ion movement exclusively along the <100>Si direction. The TiNi/Si electrode exhibited a lower capacity compared to the Si electrode but demonstrated improved cycling performance. It showed a charge capacity of 1110 mAh/g at 0.1 C with an initial efficiency of 77 % and maintained a capacity retention of 49 % (543 mAh/g) up to 100 cycles. After the initial cycle, Si electrodes exposed to various lithium insertion directions exhibited severe structural damage such as cracking and particle pulverization, whereas TiNi/Si electrodes demonstrated enhanced structural stability due to surface coating and restricted reaction pathway.

Understanding the impact of porosity on Li-ion diffusion enhancement in micro-sized silicon particles for advanced batteries

Lithium-ion batteries (LIBs) require advanced and practical anode materials, such as porous silicon (PSi), which can meet these expectations due to their rapid Li-ion diffusion rates and structural relaxation. Several studies have focused on the structural design of PSi or its composites to improve Li-ion diffusion; however, no systematic and quantitative evaluations of the impact of porosity on Li-ion diffusion and battery performance have been reported. Therefore, to understand the impact of porosity on Li-ion diffusion, we developed micro-sized porous silicon (m-PSi) particles with various porosities via metal-assisted chemical etching (MACE) method using different concentrations of AgNO3 (0.02–0.08 M). Among the as-prepared samples, m-PSi-0.06 (prepared using 0.06 M AgNO3) with ∼70 % porosity achieved a maximum Li-ion diffusion rate of 2.35 × 10−9 cm2 s−1. This led to a high-rate capability, enhanced Li-ion storage, and better cyclic retention of 61.4 % compared to the non-porous micro-sized Si (m-Si) (5.8 %) sample at a current density of 0.1 A g−1. Furthermore, the optimal porosity of m-PSi-0.06 resulted in an impressive rate capability of 760 mAh g−1 at a high current density of 4 A g−1 with a recovery rate of 80 %. The improved efficiency of m-PSi-0.06 is attributed to its optimized mesoporosity, which ensures sufficient space for Li-ion storage and shortens the effective transmission path to accelerate Li-ion diffusion. Moreover, the mesopores provide a greater number of active sites for the reversible adsorption of Li ions, thereby improving the capacitive behavior of the anode. In contrast, the highly nanoporous m-PSi-0.08, with a pore diameter of 1–3 nm, impeded Li-ion movement and restricted diffusion. These results reveal that a high nano porosity hinders Li-ion diffusion, whereas an optimal mesoporosity ensures swift diffusion in m-PSi anodes. These insights could guide the design of Si-based anode materials for advanced LIBs.

Enhancing Lithium Conductivity Using High-Valence Cations in Cubic Spinel Halide Solid Electrolytes.

Halide solid electrolytes for all-solid-state batteries have recently emerged as competitors to oxide and sulfide solid electrolytes due to their excellent electrochemical properties. This ab initio study unveils the dynamic nature of Li2Sc2/3Cl4, a rare superionic conductor among cubic spinel halide materials. Li ions in Li2Sc2/3Cl4 prefer to occupy some of the tetrahedral 8a, octahedral 16c, and octahedral 16d sites, leading to disordered Li distribution. Li ions in Li2Sc2/3Cl4 diffuse through the single-ion diffusion mechanism rather than the concerted diffusion mechanism, providing a high conductivity of 1.36 mS cm-1. Li ions at the 16d site diffuse as actively as those at the 8a/16c site, an unexpected result that runs counter to the conventional view. In Li2MgCl4, the same cubic spinel as Li2Sc2/3Cl4, Li ions at the 8a/16c site diffuse actively, but those at the 16d site are almost immobile, resulting in a very low conductivity of 5.3 × 10-4 mS cm-1. The extremely higher conductivity in Li2Sc2/3Cl4 than in Li2MgCl4 is because the concentration of Sc3+/Mg2+ cations blocking the movement of Li ions at the 16d site is lower in Li2Sc2/3Cl4 than in Li2MgCl4. Designing cubic spinel materials containing high-valence cations is proposed as a way to increase conductivity by reducing the concentration of multivalent cations that impede Li diffusion. This study sheds new light on how to control conductivity using site-dependent Li mobility in solid electrolytes.

Fabrication of Single-Ion Conductors Based on Liquid Crystal Polymer Network for Quasi-Solid-State Lithium Ion Batteries.

Single-ion conductive polymer electrolytes can improve the safety of lithium ion batteries (LIBs) by increasing the lithium transference number (tLi+) and avoiding the growth of lithium dendrites. Meanwhile, the self-assembled ordered structure of liquid crystal polymer networks (LCNs) can provide specific channels for the ordered transport of Li ions. Herein, single-ion conductive nematic and cholesteric LCN electrolyte membranes (denoted as NLCN-Li and CLCN-Li) were successfully prepared. NLCN-Li was then coated on commercial Celgard 2325 while CLCN-Li was coated on poly(vinylidene fluoride-hexafluoropropylene) film, coupled with plasticizer, to make NLCN-Li/Cel and CLCN-Li/Pv quasi-solid-state electrolyte membranes, respectively. Their electrochemical properties were evaluated, and it was found that they possessed benign thermal stability and electrolyte/electrode compatibility, high tLi+ up to 0.98 and high electrochemical stability window up to 5.2 V. A small amount (0.5M) of extra Li salt added to the plasticizer could improve the ion conductivity from 1.79 × 10-5 to 5.04 × 10-4 S cm-1, while the tLi+ remained 0.85. The assembled LFP|Li batteries also exhibited excellent cycling and rate performances. The orderliness of the LCN layer played an important role in the distribution and movement of Li ions, thereby affecting the Li deposition and growth of Li dendrites. As the first report of nematic and cholesteric LCN single-ion conductors, this work sheds light on the design and fabrication of ordered quasi-solid-state electrolytes for high-performance and safe LIBs.

Deciphering the degradation mechanism of thick graphite anodes in high-energy-density Li-ion batteries by electrochemical impedance spectroscopy

The utilization of thick electrodes represents a promising strategy for high energy density batteries, but practical application is hindered by the observed challenges of low cyclic stability and rate performance. To address these issues, we employed electrochemical impedance spectroscopy (EIS) as a non-destructive method to establish a diagnostic model capable of identifying the causes of the instability of thick electrodes. While EIS models for thick electrodes have previously been discussed, the connection between these models and the degradation mechanism has yet to be fully understood. Our investigation revealed that resistances of the current collector, solid electrolyte interphase, or electrolyte, increase with the increment of electrode thickness and further increases following the cycling test with a similar degree, indicating that the degradation of thick electrodes is not governed by those resistances. Rather, a new resistance component emerged in the thick electrode after the cycling test, indicating the emerged resistance plays as the predominant factor driving degradation. The new resistance component on the impedance spectra is linked to Li dendrite formation, due to impeded Li-ion transfer. The hindered Li-ion movement is probably due to the migration of low-weight molecules in the drying process and/or the extended distance Li-ions must transverse.

Enhanced Cathode Performance: The Heterostructure Construction of LiCoO2@Co3O4@Li6.4La3Zr1.4Ta0.6O12.

In this study, the heterostructure cathode material LiCoO2@Co3O4@Li6.4La3Zr1.4Ta0.6O12 was prepared by coating Li6.4La3Zr1.4Ta0.6O12 on the surface of LiCoO2 through a one-step solid-phase synthesis. The morphology, structure, electrical state, and elemental contents of both pristine and modified materials were assessed through a range of characterization techniques. Theoretical calculations revealed that the LCO@LLZTO material possessed a reduced diffusion barrier compared to LiCoO2, thereby facilitating the movement of Li ions. Electrochemical tests indicated that the capacity retention rate of the modified cathode composites stood at 70.43% following 300 cycles at a 2C rate. This high rate occurred because the Li6.4La3Zr1.4Ta0.6O12 film on the surface enhanced the migration of Li+, and the spinel phase of Co3O4 had better interfacial stability to alleviate the generation of microcracks by inhibiting the phase change from the layered phase to the rock-salt phase, which considerably improved the electrochemical properties.

Architecting for Mass Transport: It Is More Than Just Tortuosity

Mass transport is performance-defining across energy storage devices. An example of this limitation is evident in energy dense lithium-ion batteries (LIBs), which develop concentration gradients from insufficient transport of lithium-ions (Li-ions) when operated at high current rates. This results in lowered capacity and energy due to underutilized active material and increased overpotential. The movement of Li-ions, or lack thereof is the root cause of the trade-off that exists between energy and power density in LIBs. To alleviate societal demur towards the full adoption of electric vehicles, range anxiety and slow charging are predominant challenges that industry and academia are rushing to overcome. These goals may require reimagined processing methods to move beyond planar electrodes with disorganized and heterogeneous porosity to create architectures that are dense in active material and contain tailored porosity. To maximize the geometric component of diffusion and species flux, porous low-tortuosity channels are a rational design choice, as they act as mass-transport highways for much needed through-plane Li-ion transport.One such innovative process is hybrid inorganic phase inversion (HIPI), a manufacturing method that is scalable, material-agnostic and results in low-tortuosity free-standing and monolithic architectures with tunable material-to-pore ratios. The HIPI process can enable electrodes with adjustable thicknesses of 100s of µm and relevant micro-architectural feature sizes between 5-40 µm, tailored by tuning the gelation temperature and nucleation density of the inorganic suspension during the nonequilibrium HIPI process. Importantly, the use of a soft organogel casting support results in the unhindered accessibility of the low-tortuosity pores present in the HIPI architectures.HIPI-architected anode and cathode electrodes exhibit electrochemical and architectural stability over a 1000 cycles in a full-cell battery. Further, mass-transport constraints appear at high current densities, and we identify the lithiation step as rate-performance limiting, a result of insufficient Li-ion supply and concentration polarization. Thus, for energy and power dense LIBs the answer is not simply mass-transport highways as unoptimized low-tortuosity channels, rather in-plane Li-ion demands must be tethered to the through-plane transport. Our results demonstrate the need for and feasibility of tailored electrode architectures where dimensional ratios between low-tortuosity channels, the charge-storing matrix, and electrode thickness are tunable, to both understand multi-scale structure-performance relationships and meet coupled power and energy-storage requirements.

Super Ionic Li3–2xMx(OH)1-yNyCl (M=Ca, W, N=F) Halide Hydroxide as an Anti-Perovskite Electrolyte for Solid-State Batteries

Lithium halide hydroxide (Li2OHX) as a new class of low-cost, lightweight solid electrolyte (SSE) shows promising lithium-ion conductivity for advanced solid-state batteries. Here, using solid-state synthesis and extensive materials characterization, the impurity-free Li3–2xMx(OH)1-yNyCl (M=Ca, W, N=F) are reported, having mS cm−1 and mS cm−1 at 140 °C for Substituted smaller anionic dopants, such as facilitate the movement of Li ions within the anti-perovskite framework through rotational disordering in local coordination, resulting in the highest ion conductivity of 0.28 mS cm−1 at 25 °C. Using a strong combination of XRD, FTIR, pH, elemental EDS analysis, and calculated activation energies, it is demonstrated that the presence of H in these SSEs yields significantly higher Li+-ionic conductivity. Rotation of an OH-group in enlarged Cl-O-Cl triangular in the synthesized SSEs and their fully defected/ disordered structures enhance Li-ion conductivity.

Highly Conductive Polyoxanorbornene-Based Polymer Electrolyte for Lithium-Metal Batteries.

This present study illustrates the synthesis and preparation of polyoxanorbornene-based bottlebrush polymers with poly(ethylene oxide) (PEO) side chains by ring-opening metathesis polymerization for solid polymer electrolytes (SPE). In addition to the conductive PEO side chains, the polyoxanorbornene backbones may act as another ion conductor to further promote Li-ion movement within the SPE matrix. These results suggest that these bottlebrush polymer electrolytes provide impressively high ionic conductivity of 7.12 × 10-4 S cm-1 at room temperature and excellent electrochemical performance, including high-rate capabilities and cycling stability when paired with a Li metal anode and a LiFePO4 cathode. The new design paradigm, which has dual ionic conductive pathways, provides an unexplored avenue for inventing new SPEs and emphasizes the importance of molecular engineering to develop highly stable and conductive polymer electrolytes for lithium-metal batteries (LMB).

Efficient utilization of lithium polysulfides in CO2-derived CNT free-standing electrode of Li-S batteries

The implementation of a free-standing carbon electrode provides an excellent strategy for the development of lithium-sulfur (Li-S) batteries with a maximized sulfur portion as the electrode does not require auxiliary components including a conducting agent, binder, and current collector. Electrospinning using a polymer is an attractive approach to prepare a free-standing electrode based on high carbon yield, but effective distribution and utilization of sulfur are hindered by the low porosity of the synthesized carbon nanofiber. The present work tackles this problem of electrospinning-based free-standing electrodes by utilizing Ni precursors and CO2 conversion to make porous materials by the resulting entangled CNTs as well as pores in the carbon nanofiber. The newly formed pores greatly improved the utilization of active sulfur materials and the movement of Li ions. While leading to CNT growth and pore formation, the Ni precursor also played a role in shifting nitrogen atoms from the graphene center to the edge-site, which could greatly improve the chemical interaction between lithium polysulfides and Li-ion as also confirmed by DFT calculations. The CNTs in porous carbon fibers, which are synthesized from CO2 and have both morphological and chemical advantages, delivered an areal capacity of 3.34 mAh cm−2 up to the 200th cycle when driven at 0.2C with high content sulfur-based active materials of 6.52 mg cm−2. The CNT free-standing electrode can effectively provide a high capacity of 412 mAh gcathode−1 based on the total cathode weight.

Stabilized cellulose separator based on NaCl and glycerol with uniform structure

A membranes used as battery separators must be thermally stable because they have to withstand extreme environments such as high temperatures. However, the membrane also must have a uniformly porous structure for the movement of Li ion, which reduces the thermal stability of the membrane. Thus, to solve this problem, thermally stable membrane was developed. Here in, for the first time, we succeeded that nano-sized porous composite membrane with thermally stable was fabricated from high molecular weight cellulose acetate (CA) and additives, Glycerol and NaCl, using a hydraulic force. The mol ratio of CA and glycerol was fixed at 1 and 0.1, respectively. With various mol ratio of NaCl, The optimal ratio for the additives to be well dispersed in the composite was investigated through water flux. At 0.07 mol ratio NaCl, it was measured that average water flux was 9.431 L/m2h and the coefficient of determination (R2) was 0.9802, which meaning it has a reproducible and largest water flux than other NaCl mol ratios. Thus, the optimal ratio was glycerol:NaCl = 0.1:0.07 mol ratio. In the optimal ratio, average porosity of the composite was measured to 10.20 ± 0.08%. It was confirmed by SEM that the pore sizes of the surfaces were similar. The thermodynamic properties of the CA/glycerol/NaCl composites was measured using TGA and DTG. It was shown that the thermal stability of the CA/glycerol/NaCl composite had a thermal behavior similar to neat CA film even though pore was formed. This was demonstrated that thermal stability was improved by stabling coordination bonding between the carbonyl group of CA and remaining additives. In addition, the degree of coordination bonding with the carbonyl group of CA according to the amount of NaCl was investigated using XPS.

Surface Oxygen Vacancy Inducing Li‐Ion‐Conducting Percolation Network in Composite Solid Electrolytes for All‐Solid‐State Lithium‐Metal Batteries (Small 22/2023)

All-Solid-State Lithium-Metal Batteries In article number 2207223, Jeeyoung Yoo, Youn Sang Kim, and co-workers present an all-solid-state lithium-metal battery with composite solid electrolyte. Specifically, the oxygen vacancy-rich indium tin oxide (ITO) nanoparticles (green-colored) induce the Li-ion conducting percolation network (red-colored) at the ITO-poly(ethylene oxide) (PEO) interface. The oxygen vacancy enables fast movement of Li-ions in the interface network. This phenomenon suggests that the vacancy engineering of filler holds strong promise for developing advanced all-solid-state batteries.

Preparation of Li2S-AlI3-LiI Composite Solid Electrolyte and Its Application in All-Solid-State Li-S Battery

Novel (80Li2S − 20AlI3)·yLiI composite solid electrolytes (y = 5, 10, 15) were prepared by mechannochemical synthesis. XRD results showed that the pattern of 80Li2S − 20AlI3 was similar to that of AlI3, which means that Li2S was dissolved in AlI3 matrix during preparation. This structure was still maintained after LiI addition. The current measured at constant applied DC voltage indicated that (80Li2S − 20AlI3)·yLiI composites are intrinsically pure Li-ion conductors. The ionic conductivity at 25 °C of y = 10 was about 2.3 × 10−4 Scm−1, which was about three times higher than that of y = 0. The conductivity of y = 10 increased 20 times to 2.2 × 10−3 Scm−1 at 70 °C. These values were highest among those observed from Li2S-based materials. It was revealed that Li-ion moves in 80Li2S − 20AlI3 by a hoping mechanism, while the lattice dipoles are the origin of Li-ion movement in (80Li2S − 20AlI3)·yLiI. The polarization measurements using Liǀ90 (80Li2S − 20AlI3)·10LiI ǀLi and LiǀLi6PS5Clǀ90 (80Li2S − 20AlI3)·10LiIǀLi6PS5ClǀLi cells proved that 90 (80Li2S − 20AlI3)·10LiI reacts with Li metal, but it is relatively stable at a low voltage. Sample y = 10 was also employed as a solid electrolyte in the positive electrode of a solid-state Li-S battery to study its stability in the voltage range of the positive electrode. CuS and Li4.4Si were the electrode-active materials. The cell was cycled in CC-CV mode at 1.0 mA cm−2 (CC) with a cut-off voltage of 1.0–2.3 V. The cell delivered a stable capacity of about 400 mAh g−1CuS after 40 cycles.

Sustainable metal-organic framework co-engineered glass fiber separators for safer and longer cycle life of Li-S batteries

Most of the issues with making Li–S batteries are caused by the growth of Li dendrites and the movement of polysulfide. To solve both of these problems at the same time, this study describes the placement of Cu or Fe atoms on an ultrathin metal organic framework (MOF) nanosheet-based glass fiber separator for making Li–S batteries that are safe and last a long time. Cu or Fe atoms coordinated with oxygen atoms on the surface of ultrathin MOF nanosheets can greatly facilitate the movement of Li ions while acting as "traps" to stop polysulfide from moving around by introducing the Lewis acid-base interaction. Because of this, the Li–S cells with the Cu/MOF or Fe/MOF coatings on the glass fiber separator show long-term cycling stabilities with low-capacity decay of 0.080% and 0.057% per cycle over 400 cycles, respectively. Furthermore, Li–S cells assembled with the Cu/MOF and Fe/MOF separators show capacity retention of 985 and 1237 mAh g−1, respectively, after 400 cycles, indicating the potential of the Cu/MOF and Fe/MOF separators for practical applications.

Influence of Vanadium Oxide on the Optical and Electrical Properties of Li (Oxide or Fluoride) Borate Glasses

Binary glass systems of the chemical composition 0.25Li2O–0.75B2O3 and 0.25LiF–0.75B2O3 with different additive ratios of V2O5 were prepared using the melt-quenching method. Characterization was carried out through different techniques such as Fourier-transform infrared (FTIR) and ultraviolet–visible absorption (UV–visible) spectroscopy. Optical and electrical properties have been investigated in order to recognize the role of V2O5 in glass. FTIR spectra of the studied glasses expose repetitive vibration curves with limited variations. BO4 and BO3 are the basic constituent units of the studied glasses in addition to the BO2F and BO3F units in the case of fluoro-borate glasses. Shifting to a higher wavelength in the optical absorption spectra and a decrease in the optical band gap values via increasing V2O5 content confirms the formation of non-bridging oxygen (NBO). The ac-electrical conductivity (σac) and the dielectric constants (ɛ′) of the glass samples were studied in the frequency range 102 Hz–8 MHz. The ionic conduction takes place by Li-ion movement in all samples. The electronic conduction of borate glass can be explained using hopping between V4+ and V5+. The results show excellent properties of the glass with a low concentration of vanadium oxide.Graphical

New insights into the effects of available space characteristics within graphite-based anodes on the accessibility of solvated Li-ions under fast charging conditions

Energy storage materials for energy storage system or electric vehicle should be able to supply high capacity quickly. Especially, Li-ion accessibility within graphite-based anodes is the key point to enhance mass transfer and the electrochemical performance. In terms of solvated Li-ion accessibility to the space, space in graphite-based anode is classified as two consecutive scales, channel and surface pores. A Li-ion transferrable channel is controlled by the calendering process, and surface pores are modified with a chemical vapor deposition surface coating to enhance the solvated Li-ion accessibility in each space. Cross-analysis of BET with small-angle X-ray scattering was conducted to determine whether each space is accessible and where the optimal point is. Finding correlations with the tortuosity value provided not only quantitative but also geometrical information on the space which was derived from the making process of each electrode, reflecting actual solvated Li-ion movement. This study not only suggests two distinguishable views in enhancing the accessibility of solvated Li-ions but also presents new insights to figure out how the changes in space characteristics affect the electrochemical performance. Furthermore, these findings could provide a potential strategy to estimate commercialized graphite such that the actual solvated Li-ion movement can be interpreted.

One-Dimensional Porous Li-Confinable Hosts for High-Rate and Stable Li-Metal Batteries.

Li-confinable core-shell hosts have been extensively studied because they mitigate Li dendrite growth and volume change by reducing the effective current density and storing Li inside the core space during consecutive cycling. However, despite these fascinating features, these hosts suffer from unwanted Li growth on their surface (i.e., top plating) due to the carbon shell hindering Li-ion movement especially at higher current densities and capacities, resulting in poor electrochemical performance. In this study, we propose a one-dimensional porous Li-confinable host with lithiophilic Au (Au@PHCF), which is synthesized by a scalable dual-nozzle electrospinning. Because of the well-interconnected conductive networks forming three-dimensional structure, porous shell design enabling facile Li-ion transport, and hollow core space with lithiophilic Au storing metallic Li, the Au@PHCF can suppress the Li top plating and improve the Li stripping/plating efficiency compared to their counterparts even at 5 mA cm-2, eventually achieving stable cycling performances of the LiFePO4 full cell and Au@PHCF-Li symmetric cell for over 1000 and 2000 cycles, respectively. Finite element analysis reveals that the structural merit and lithiophilicity of Au enable fast reversible Li operation at the designated core space of the Au@PHCF, implying that the structural design of the Li-confinable host is crucial for the stable operation of promising Li-metal batteries at a practical test level.

Preparation of β-Polyvinylidene Fluoride Film for Self-Charging Lithium-Ion Battery

—In recent years development of sustainable energy sources is getting extensive research interest due to the ever-growing demand for energy. As an alternative energy source to power small electronic devices, ambient energy harvesting from vibration or human body motion is considered to be a potential candidate. Despite the enormous progress in the field of battery research in terms of safety, lifecycle, and energy density in about three decades, it has not reached the level to conveniently power wearable electronic devices such as smart watches, bands, hearing aids, etc. For this reason, the development of self-charging power units with excellent flexibility, and integrated energy harvesting and storage is crucial. Self-powering is a key idea that makes possible the system to operate sustainably, which is now getting more acceptance in many fields in the area of sensor networks, internet of things (IoT) and implantable in-vivo medical devices.For solving this energy harvesting issue, the self-powering nanogenerators (NGs) were proposed and proved their high effectiveness. Usually, sustainable power is delivered through energy harvesting and storage devices by connecting them to the power management circuit, as for energy storage, Li-ion battery (LIB) is one of the most effective technologies. Through the movement of Li ions under the driving of an externally applied voltage source, the electrochemical reactions generate the anode and cathode, storing the electrical energy as the chemical energy. In this paper, we present a simultaneous process of converting the mechanical energy into chemical energy in a way that NG and LIB are combined as an all-in-one power system.The electrospinning method was used as an initial step for the development of such a system with β-PVDF separator. The obtained film showed promising voltage output at different stress frequencies. X-Ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) analysis showed a high percentage of β phase of PVDF polymer material. Moreover, it was found that the addition of 1 wt.% of BTO (Barium Titanate) results in higher quality fibers. When comparing pure PVDF solution with 20 wt.% content and the one with BTO added the latter was more viscous. Hence, the sample was electrospun uniformly without any beads. Lastly, to test the electrical output of such film, a particular testing device has been developed. With this device, the force of a finger tap can be applied at different frequencies, so that voltage generation across the surfaces of the film is validated. Further, this piezoelectric PVDF film can be used as a separator for LIB. Acknowledgements This work was supported by the project 240919FD3914 “Self-Charging Rechargeable Lithium-ion Battery” from Nazarbayev University, Kazakhstan.

Exploring the Ion Solvation Environments in Solid-State Polymer Electrolytes through Free-Energy Sampling

The success of poly(ethylene oxide) (PEO) in solid-state polymer electrolytes for lithium-ion batteries is well established. Recently, in order to understand this success and to explore possible alternatives, we studied polyacetal electrolytes to deepen the understanding of the effect of the local chemical structure on ion transport. Advanced molecular dynamics techniques using newly developed, tailored interaction potentials have helped elucidate the various coordination environments of ions in these systems. In particular, the competition between cation–anion pairing and coordination by the polymer has been explored using free-energy sampling (metadynamics). At equivalent reduced temperatures, with respect to the polymer-specific glass-transition temperature, two-dimensional free-energy plots reveal the existence of multiple coordination environments for the lithium (Li) ions in these systems and their relative stabilities. Furthermore, we observe that the Li-ion movement in PEO follows a serial, stepwise pathway when moving from one coordination state to another, whereas this happens in a more continuous and concerted fashion in a polyacetal such as poly(1,3-dioxalane) [P(EO-MO)]. The implication is that interconversion between coordination states of the Li ions may be easier in P(EO-MO). However, the overarching observation from our free-energy analysis is that Li-ion coordination is dominated by the polymer (in either case) and contact-ion pairs are rare. We rationalize the observed higher increase in glass-transition temperature (Tg) with salt loading in polyacetals as due to intermolecular Li-ion coordination involving multiple polymer chains, rather than just one chain for PEO-based electrolytes. This interchain coupling in the polyacetals, resulting in the higher Tg, works against any gains due to variations in Li-ion coordination that might enhance transport processes over PEO. Further research is required to overcome the interdependence between local coordination and macroscopic properties to compete with PEO electrolytes at the same absolute working temperature.

Hyperbranched Polyphenylene as an Electrode for Li‐Ion Batteries

Polymeric electrodes have attracted considerable attention for their potential as Li‐ion battery (LIB) electrodes due to their tunable structures and sustainable preparation from abundant precursors in an environmentally friendly manner. Herein, hyperbranched polyphenylene (HBP) is synthesized through Suzuki polycondensation and investigated as a potential bipolar electrode for LIBs. The advantages of the hyperbranched architecture in HBP include easy and fast transportation of ions as an electrode. Brunauer–Emmett–Teller (BET) measurement on HBP reveals a high specific surface area and porosity compared with typical linear polymers. The low conductivity in HBP is improved by preparing an HBP/multiwalled carbon nanotube (MWCNT) composite material. The LIB performance for the HBP/MWCNT composite anode electrode shows good cyclic stability and high specific capacity, which are caused by the branching architecture, surface area, and improved electronic conductivity from the MWCNT. This results in easy access and rapid movement of Li ions for improved charge–discharge performance. The ex situ technique using Fourier transform infrared spectroscopy shows a lithium storage mechanism in the HBP electrode. This work shows extensive scope for using the hyperbranched architectural concept to explore and develop high‐performing organic electrodes for future metal‐ion batteries.