Conventional Carbonate Electrolytes Research Articles

Review on polymer electrolytes for lithium‐sulfurized polyacrylonitrile batteries

AbstractLithium‐sulfur (Li‐S) batteries are deemed as the next generation of energy storage devices due to high theoretical specific capacity (1675 mAh g−1) and energy density (2600 Wh kg−1). However, the commercial application has always been constrained by lithium polysulfide (LiPSs) shuttling effects and still has a long way to go. Sulfurized polyacrylonitrile (SPAN) is a promising alternative candidate to replace traditional sulfur cathode and is conducive to eliminating LiPSs by realizing “solid‐solid” direct conversion in conventional carbonate electrolytes. However, an over 25% irreversible capacity loss is exhibited inevitably in the first discharge process, the inherent structure of SPAN and the related reaction mechanism remain unclear. In this review, the structure characteristics and electrochemical behaviors of SPAN are summarized for better interpreting current knowledge and favoring the design of high performance materials. In the past few decades, many problems in traditional Li‐S batteries have been solved by improving electrolytes. Polymer electrolytes (PEs) have been widely used due to structural designability, multi‐functionality, exceptional chemical stability, and excellent processability. Surprisingly, the relevant researches on PEs compatible with SPAN remains limited currently. Therefore, the recent modification strategies of gel polymer electrolytes and solid polymer electrolytes in Li‐SPAN batteries are introduced in terms of Li+ transfer and interface engineering, the design principles are concluded, the specific challenges encountered by polymer‐based electrolytes are summarized and the instructive directions for future research on PEs are demonstrated, facilitating the commercialization of Li‐SPAN batteries.

Cyclic Ether-Based Electrolyte with a Weak Solvation Structure for Advanced Potassium Metal Batteries.

Potassium metal batteries (PMBs) are promising candidates for large-scale energy storage. Conventional carbonate electrolytes exhibit unsatisfactory thermodynamic stability against potassium (K) metal anode. Linear ether is widely adopted because of its compatibility with K metal, but the poor oxidation stability restricts the application with high-voltage cathodes. Herein, a weakly solvating cyclic ether is proposed as a solvent to stabilize the K-electrolyte interface and build a robust solid-electrolyte interphase (SEI). This weakly solvating electrolyte (WSE) possesses an anion-dominated solvation structure, which facilitates the anion decomposition for constructing an inorganic-rich SEI. The superior mechanical properties of the SEI, as examined by atomic force microscopy, prevent the SEI from fracture. Consequently, this WSE achieves highly reversible plating/stripping behavior of K metal for 1300h with a high average Coulombic efficiency of 99.20%. Stable full cells are also demonstrated with a high-voltage cathode at harsh conditions. This work complements the design of WSEs for advanced PMBs by cyclic ether solvents.

Interphase engineering by tunable redox of (p-d) π-bond additive toward extended lifespan of sodium-ion batteries

The durability of the cathode and anode interphases is critical for long-term stable cycling of sodium-ion batteries, however, difficult to achieve precise modulation in conventional carbonate-based electrolytes. Herein, from the perspective of functional additives, the sulfur-containing interphase engineering is introduced by the cyclic sulfate esters with tunable redox mechanism, which are oriented to alter specific decomposition and film-forming pathways on the surface of the cathode and anode, compensating for the deficiencies of the fluorinated interphases, such as improving the inhomogeneous and fragile characteristics, while enhancing the ion transport efficiency. As a result, the cells based on hard carbon (HC) and high voltage Na3V2(PO4)2O2F (NVPF) demonstrate excellent cycling stability (1000 and 8000 cycles with more than 80 % and 83 % capacity retention, respectively). Moreover, the assembled HC//NVPF full cell also achieves a cycle life of more than 2500 cycles with a capacity retention of 91%, which is far superior to that of conventional carbonate electrolytes. Furthermore, the high-voltage oxide cathode also demonstrates extended cycling stability (80 % capacity retention after 300 cycles). In short, the proposed sulfur-based additive strategy enables to effectively improve the problems encountered in carbonate-based electrolytes, providing certain reference and application value.

The high-fluorinated bi-molecular combination enables high-energy lithium batteries under challenging environment

The drawbacks of temperature sensitivity, high voltage intolerance, and flammability of lithium batteries are gradually brought to light in conventional carbonate electrolytes. To solve these problems, a localized high concentration electrolyte (LHCE) employing highly fluorinated ethyl trifluoroacetate (TFAE) and 2,2,3,3-tetrafluoro-1-(1,1,2,2-tetrafluoroethoxy) propane (TFEP) is designed. When applied in high-energy lithium batteries, the discharge specific capacity of Li||NMC811 battery can maintain 143.6 mAh/g after 500 cycles at 4.6 V and 1C, and the capacity retention of Li||LNMO battery retains as high as 89.99 % after 500 cycles at 5 V. In addition, this LHCE also possesses the ability to operate the battery under challenging conditions including low temperature, fast charge, safety risks, etc. The LHCE based on TFAE and TFEP has unique solvated structures to generate a moderate LiF-rich interfacial layer, ensuring the fast Li+ migration. This work will provide strong guidance for future electrolyte industrial design of high-energy lithium battery.

In Situ Ions Induced Formation of KxF-Rich SEI Layers toward Ultrastable Life of Potassium-Ion Batteries.

Engineering F-rich solid electrolyte interphase (SEI) layers is regarded as an effective strategy to enable the long-term cycling stability of potassium-ion batteries (KIBs). However, in the conventional KPF6 carbonate electrolytes, it is challenging to form F-containing SEI layers due to the inability of KPF6 to decompose into KxF. Herein, AlCl3 is employed as a novel additive to change the chemical environment of the KPF6 carbonate electrolyte. First, due to the large charge-to-radius ratio of Al3+, the Al-containing groups in the electrolyte can easily capture F from PF6 - and accelerate the formation of KxF in SEI layer. In addition, AlCl3 also reacts with trace H2O or solvents in the electrolytes to form Al2O3, which can further act as a HF scavenger. Upon incorporating AlCl3 into conventional KPF6 carbonate electrolyte, the hard carbon (HC) anode exhibits an ultra-long lifespan of 10000 cycles with a high coulombic efficiency of ≈100%. When coupled with perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), the full cell exhibits a high capacity retention of 81% after 360 cycles-significantly outperforming cells using conventional electrolytes. This research paves new avenues for advancing electrolyte engineering towards developing durable batteries tailored for large-scale energy storage applications.

Long-life potassium metal batteries enabled by anion-derived solid electrolyte interphase using concentrated ionic liquid electrolytes

Potassium metal batteries (PMBs) show great potential as next-generation energy storage systems yet face challenges such as the dendritic growth of the potassium anode, leading to issues with cycle life and safety. This study reports a potassium salt-concentrated ionic liquid electrolyte (PCIL) consisting of potassium bis(fluorosulfonyl)imide (KFSI) and 1-methyl-1-propyl pyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI) to achieve long-life and, safe PMBs. PCIL presents several advantages including outstanding oxidation stability (≈5.2 V), decent ionic conductivity (4.0 mS cm−1 at 25 °C), and negligible flammability. Moreover, PCIL promotes the development of anion-derived solid-electrolyte interphase (SEI) with high inorganic content. This not only hinders the growth of potassium dendrites but also facilitates facile interfacial charge transfer kinetics. Benefiting from these advantages, PMBs (K||KVPO4F) employing PCIL exhibit remarkable cycle performances at both ambient and elevated temperatures (capacity retention after 300 cycles: 74.8% at 25 °C and 82.9% at 45 °C), surpassing the performance of conventional carbonate (1 M KPF6 EC/PC) and dilute potassium ionic liquid electrolyte (PIL). This work demonstrates the tangible capability of PCIL in realizing practical PMBs.

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes in a Localized High‐Concentration Electrolyte

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes in a Localized High‐Concentration Electrolyte

Tuning Rate‐Limiting Factors for Graphite Anodes in Fast‐Charging Li‐Ion Batteries

AbstractLocalized high‐concentration electrolyte (LHCE) is considered to be a promising substitution for the conventional carbonate electrolytes in fast‐charging Li‐ion batteries. However, the rate‐determining steps (RDS) for fast‐charging electrodes (i.e., graphite anode) in LHCE remain unclear. Herein, a typical localized high‐concentration electrolyte consisting of lithium bis(fluorosulfonyl)imide in dimethoxyethane with 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether as a diluent is selected to investigate the RDS of lithiation process in graphite anode, including the diffusion of solvated Li+ in the electrolyte, the desolvation behavior of solvated Li+, the Li+ transfer in solid electrolyte interphase (SEI) on the graphite surface, and the Li+ diffusion in bulk graphite. The results indicated that the rate performance of graphite anode in LHCE lies in the balance between Li+ desolvation process and Li+ migration in SEI. Through the regulation of solvated Li+ structure and SEI component, excellent fast‐charging performance can be obtained in the LHCE. The present studies not only offer fresh insights in the mechanistic understanding of fast‐charging batteries, but also provide new clues to the performance improvement of graphite anodes.

Full gradient compensation of LiNO3 in the suspension electrolyte for lithium metal batteries

Uncontrolled side reactions between lithium metal and organic electrolytes seriously deteriorates the stability of corresponding battery due to the non-uniform Li+ deposition. Using lithium nitrate (LiNO3) as an additive can adjust the components in solid-electrolyte-interphase (SEI) for optimizing of lithium metal interface. However, the low solubility and rapid consumption of LiNO3 in ester-based electrolytes limit its further application. Herein, a kind of suspension electrolyte containing micron-sized LiNO3 particles is reported to realize a full gradient compensation against the consumption of NO3−. Benefiting from the uniformly dispersion of LiNO3 particles, a SEI layer containing even-distributed Li3N and LiNxOy with high content is constructed that promotes the rapid and uniform plating of Li+. Consequently, the Li/Cu batteries present a polarization of only 15–20 mV, and exhibit a consistent performance for 230 cycles with the CE of 98.1%, which is 4 times than that of conventional carbonate electrolytes. In addition, the cycling life of the assembled Li/NCM811 batteries can be extended to 260 cycles with a high capacity retention of 82.4 %.

Rechargeable Manganese Dioxide||Hard Carbon Lithium Batteries in an Ether Electrolyte

Earth-abundant, cost-effective electrode materials are essential for sustainable rechargeable batteries and global decarbonization. Manganese dioxide (MnO2) and hard carbon both exhibit high structural and chemical tunability, making them excellent electrode candidates for batteries. Herein, we elucidate the impact of electrolytes on the cycling performance of commercial electrolytic manganese dioxide in Li chemistry. We leverage synchrotron X-ray analysis to discern the chemical state and local structural characteristics of Mn during cycling, as well as to quantify the Mn deposition on the counter electrode. By using an ether-based electrolyte instead of conventional carbonate electrolytes, we circumvent the formation of a surface Mn(II)-layer and Mn dissolution from LixMnO2. Consequently, we achieved an impressive ∼100% capacity retention for MnO2 after 300 cycles at C/3. To create a lithium metal-lean full cell, we introduce hard carbon as the anode which is compatible with ether-based electrolytes. Commercial hard carbon delivers a specific capacity of ∼230 mAh g−1 at 0.1 A g−1 without plateau, indicating a surface-adsorption mechanism. The resulting manganese dioxide||hard carbon full cell exhibits stable cycling and high Coulombic efficiency. Our research provides a promising solution to develop cost-effective, scalable, and safe energy storage solutions using widely available manganese oxide and hard carbon materials.

Tailored Cation–Anion Coordination in Carbonate Electrolyte Enabling a Rigid‐Flexible Compact Solid‐Electrolyte Interphase for Potassium Batteries

AbstractPotassium batteries have received extensive attention as a promising grid‐level storage technology. However, the anodes in potassium batteries using conventional carbonate‐based electrolyte systems always suffer from severe capacity deterioration, due to the heterogeneous and highly swollen solid‐electrolyte interphase (SEI) layer. Herein, a rigid‐flexible compact SEI consisting of rigid inner KF layer and flexible crosslinked oligomeric K–B(OCH2CH2)n (modified KEO), is designed by tailoring cation–anion coordination in 1 m carbonate electrolyte based on the main salt—potassium perfluorinated pinacolatoborate, (KB(O2C2(CF3)4)2, abbreviated as KPFB). Specifically, the KPFB tunes K+−anions coordinated configuration in K+ solvation sheaths by unique spatial structure and strong electron‐withdrawing effect of its eight −CF3 groups. With the assistance of rigid‐flexible compact SEI layer, the potassium metal symmetric cells stably cycle for more than 1600 hours in the conventional carbonate electrolyte (1 m KPFB‐EC/DEC). Moreover, K||graphite and K||Prussian blue (PB) batteries adopting this conventional carbonate electrolyte can operate for more than 500 and 120 cycles with high average Coulombic efficiency of 99.7% and 99.4%, respectively. The work provides new insights in customizing salt anion structure to reinforce SEI layer for high‐performance potassium batteries.

Stabilizing LiNi0.8Co0.1Mn0.1O2 cathode by combined moisture and HF digestion/adsorption for high-performance lithium metal batteries

Nickel-rich layered oxide cathodes such as LiNi0.8Co0.1Mn0.1O2 are promising to significantly increase the energy density of lithium metal batteries beyond 350 Wh kg−1. However, serious issues regarding cycle stability still remain when matching with conventional non-aqueous carbonate electrolytes that contain fluorine such as lithium hexafluorophosphate (LiPF6). Hydrolysis of LiPF6 generates corrosive hydrofluoric acid (HF), which destroys the cathode structure and accelerates the cathodic dissolution/anodic deposition of transition metal (TM) ions. Here, we demonstrate that ball milling NCM811 with carbon-coated aluminum nitride (AlN-C) remarkably enhances the capacity retention. AlN-C acts both as a scavenger and as an adsorption center to digest and adsorb H2O and HF, respectively. Thereby, it prevents the dissolution of TM ions, which would result in capacity decay and damage to the lithium metal anode. It is demonstrated that the addition of AlN-C via wet ball milling with NCM811 enables retaining a specific capacity of 149.9 mA h g−1 after 250 cycles (capacity retention: 85.2 %) at 1 C even in a high moisture electrolyte containing ∼0.2 % (v/v) H2O. Therefore, this work shows up a pathway to a rational enhancement of the capacity retention and cycle life of nickel-rich cathodes.

Interfacial solvation-structure regulation for stable Li metal anode by a desolvation coating technique

Rechargeable lithium (Li) metal batteries face challenges in achieving stable cycling due to the instability of the solid electrolyte interphase (SEI). The Li-ion solvation structure and its desolvation process are crucial for the formation of a stable SEI on Li metal anodes and improving Li plating/stripping kinetics. This research introduces an interfacial desolvation coating technique to actively modulate the Li-ion solvation structure at the Li metal interface and regulate the participation of the electrolyte solvent in SEI formation. Through experimental investigations conducted using a carbonate electrolyte with limited compatibility to Li metal, the optimized desolvation coating layer, composed of 12-crown-4 ether-modified silica materials, selectively displaces strongly coordinating solvents while simultaneously enriching weakly coordinating fluorinated solvents at the Li metal/electrolyte interface. This selective desolvation and enrichment effect reduce solvent participation to SEI and thus facilitate the formation of a LiF-dominant SEI with greatly reduced organic species on the Li metal surface, as conclusively verified through various characterization techniques including XPS, quantitative NMR, operando NMR, cryo-TEM, EELS, and EDS. The interfacial desolvation coating technique enables excellent rate cycling stability (i.e., 1C) of the Li metal anode and prolonged cycling life of the Li||LiCoO2 pouch cell in the conventional carbonate electrolyte (E/C 2.6 g/Ah), with 80% capacity retention after 333 cycles.

Realizing Low-Temperature Graphite-based Rechargeable Potassium-Ion Full Battery.

Graphite (Gr) has been considered as the most promising anode material for potassium-ion batteries (PIBs) commercialization due to its high theoretical specific capacity and low cost. However, Gr-based PIBs remain unfeasible at low temperature (LT), suffering from either poor kinetics based on conventional carbonate electrolytes or K+ -solvent co-intercalation issue based on typical ether electrolytes. Herein, a high-performance Gr-based LT rechargeable PIB is realized for the first time by electrolyte chemistry. Applying unidentate-ether-based molecule as the solvent dramatically weakens the K+ -solvent interactions and lowers corresponding K+ de-solvation kinetic barrier. Meanwhile, introduction of steric hindrance suppresses co-intercalation of K+ -solvent into Gr, greatly elevating operating voltage and cyclability of the full battery. Consequently, the as-prepared Gr||prepotassiated 3,4,9,10-perylene-tetracarboxylicacid-dianhydride (KPTCDA) full PIB can reversibly charge/discharge between -30 and 45 °C with a considerable energy density up to 197 Wh kgcathode -1 at -20 °C, hopefully facilitating the development of LT PIBs.

Realizing Low‐Temperature Graphite‐based Rechargeable Potassium‐Ion Full Battery

AbstractGraphite (Gr) has been considered as the most promising anode material for potassium‐ion batteries (PIBs) commercialization due to its high theoretical specific capacity and low cost. However, Gr‐based PIBs remain unfeasible at low temperature (LT), suffering from either poor kinetics based on conventional carbonate electrolytes or K+‐solvent co‐intercalation issue based on typical ether electrolytes. Herein, a high‐performance Gr‐based LT rechargeable PIB is realized for the first time by electrolyte chemistry. Applying unidentate‐ether‐based molecule as the solvent dramatically weakens the K+‐solvent interactions and lowers corresponding K+ de‐solvation kinetic barrier. Meanwhile, introduction of steric hindrance suppresses co‐intercalation of K+‐solvent into Gr, greatly elevating operating voltage and cyclability of the full battery. Consequently, the as‐prepared Gr||prepotassiated 3,4,9,10‐perylene‐tetracarboxylicacid‐dianhydride (KPTCDA) full PIB can reversibly charge/discharge between −30 and 45 °C with a considerable energy density up to 197 Wh kgcathode−1 at −20 °C, hopefully facilitating the development of LT PIBs.

Integrating commercial graphite with network-like carbon fibers for high-rate and long-term cycling K+-storage.

K can reversibly intercalate into graphite by forming KC8 (279 mA h g-1, ≈0.2 V) in conventional carbonate electrolytes, but the large ionic radius of K+ (1.38 Å) easily results in structural degradation and rapid capacity decay. Here, commercial graphite particles are directly electrospun into network-like carbon fibers, thus forming a flexible Gr@CNF membrane. This hybrid electrode configuration can efficiently withstand the volume expansion during K+ insertion. K||Gr@CNF half-cells can stably operate for over 800 cycles (running time of 170 days at C/3) and achieve fast K+-intercalation kinetics at 5C. The fabricated Gr@CNF||AC K-ion hybrid capacitor delivers a high energy density of 119.3 W h kg-1 at 2717.82 W kg-1, corresponding to a fast-charge time of 3.2 min.

Influence of Lithium Diffusion into Copper Current Collectors on Lithium Electrodeposition in Anode-Free Lithium-Metal Batteries

With increasing demands for lithium-based batteries that have higher energy densities, access to better negative electrode materials becomes crucial. Lithium metal which has a very high theoretical specific capacity, a very low standard potential and a very low density can be considered one of the best negative electrode materials for next-generation lithium-based batteries. In order to fully exploit the merits of lithium metal, a cell configuration in which lithium is directly electrodeposited (and then stripped) on (from) the negative electrode current collector (i.e., copper foil) is essential. Such “anode-material-free” (or ”anode-free”) lithium-metal batteries can have significantly higher gravimetric and volumetric energy densities than conventional graphite-based lithium-ion batteries. However, poor control of the lithium electrodeposition directly on the copper current collector, especially in conventional carbonate electrolytes, limits the development of such batteries. It is therefore essential to improve the understandings of the lithium electrodeposition, especially its nucleation process, and the interactions between lithium and the copper substrate.According to the classical electrodeposition theory, a larger overpotential will lead to a decrease in both the critical free energy for the nucleation and the critical radius of the nuclei, which should facilitate the nucleation process since more clusters can reach the critical radius required to form stable nuclei with a lower energy barrier. The concept was utilized via the application of a potentiostatic nucleation pulse to attain two-dimensional instantaneous lithium nucleation on lithium-metal electrodes in a previous study by Rehnlund et al.[1] Using such a strategy should also provide some insights into the lithium nucleation on copper substrates. In addition, it is also important to consider interactions between lithium and the copper substrate. A study, in which Lv et al.[2] used operando neutron diffraction to track the spatial distribution of lithium during lithium electrodeposition and stripping on copper, revealed that some lithium was actually taken up by the copper substrates most likely via the grain boundaries during the electrodeposition. In other studies by Rehnlund et al., the results also showed that lithium can diffuse into copper and that the effect of this diffusion can be readily seen after electrodepositing a small amount of lithium (as would be the case during the lithium nucleation stage).[3,4] However, the relation between such a lithium diffusion behavior and the lithium nucleation on copper substrates is not clearly studied.With a series of electrodeposition experiments, we demonstrate that it is highly possible that the lithium diffusion into the copper substrate can influence the nucleation process. Due to the presence of such diffusion, small lithium clusters and nuclei may be lost during the nucleation process, which makes it difficult to obtain a larger number of lithium nuclei with a homogeneous distribution on the copper surface. This then leads to inhomogeneous lithium electrodeposits with poor morphologies. It is, however, demonstrated that the nucleation of lithium on copper can be significantly improved if an initial chemical prelithiation of the copper surface is performed. This prelithiation saturates the copper surface with lithium and hence decreases the influence of lithium diffusion via the grain boundaries. In this way, the lithium nucleation can be made to take place more homogenously on the copper surface, especially when a short potentiostatic nucleation pulse that can generate a large number of nuclei is used.[1] D. Rehnlund, C. Ihrfors, J. Maibach, L. Nyholm, Mater. Today 21 (2018) 1010–1018.[2] S. Lv, T. Verhallen, A. Vasileiadis, F. Ooms, Y. Xu, Z. Li, Z. Li, M. Wagemaker, Nat. Commun. 9 (2018) 1–12.[3] D. Rehnlund, F. Lindgren, S. Böhme, T. Nordh, Y. Zou, J. Pettersson, U. Bexell, M. Boman, K. Edström, L. Nyholm, Energy Environ. Sci. 10 (2017) 1350–1357.[4] D. Rehnlund, J. Pettersson, K. Edström, L. Nyholm, ChemistrySelect 3 (2018) 2311–2314.

Firefighting Gel Polymer Electrolyte for Non-Flammable Li-Ion Batteries Based on Extremely Low Amount of a Cross-Linkable Polymer

Safety issues of lithium-ion batteries(LIBs) have caught a priority of concerns as the electric vehicle(EV) market expands dramatically and requires higher energy densities. To be free from a variety of unpredictable situations and environments triggering such a safety issue, materials that provide a mechanism to control the factors causing fire and explosion are required to be involved in LIB cells.In this work, we present a gel polymer electrolyte(GPE) characterized by nonflammability and fire-extinguishing capability by radical scavenging(Rs). This GPE was realized within battery cells by in situ crosslinking a small amount of a cross-linkable fluoro-functionalized cyanoethyl polyvinyl alcohol(F7) in conventional carbonate electrolytes having LiPF6. The cyanoethyl functional groups(-CN) is responsible for gelation by cross-linking while the fluorine-containing moiety terminated radical chain reactions triggering thermal runaway by Rs. The strong interaction between the polymer and solvent molecules restricted solvent volatility. The tiny solid content at 2 wt. % in GPE guaranteed a liquid-level ionic conductivity at 9 mS/cm, disallowing battery performances to be sacrificed. Formation of the LiF-dominant solid-electrolyte-interphase(SEI) layer on anodes was encouraged by the fluoro-moiety of F7.In previous research of our group, PVA-CN was used as cross-linkable polymer for enhancement of mechanical property with additional metal-chelating functional group. Hydroxy group of PVA-CN is useful to modify the functional group by DCC coupling mechanism. Herein, as same as previous modification, the Heptafluorobutyric acid(HFB) was used for non-flammability and battery performance. F7 was expected to not only increase thermal stability but also scavenge the radicals. In addition, LiF-rich SEI layers would be made by fluorine groups.First, GPE increase its thermal stability by strong interaction between cross-linked polymer matrix and organic solvents. The binding energy of ethylene carbonate (EC) and hydrogen of cyanoethyl side chain was 0.4 eV which is stronger compared with general hydrogen bond(0.2 eV). Therefore, the flammable gas generation was suppressed by strong interaction between solvents and polymer matrix.In addition, the flash point demonstrated the strong interaction in GPE. The flash point of GPE which contained different polymer contents was decreased as the ratio of polymer content was increased. The composition of the atmosphere in the devices changed into more flammable because of the higher ratio of EMC gas in the atmosphere within enough time to equilibrate. In other words, EC forms a greater number of strong interactions with the polymer matrix while the polymer contents increased. The SET test of 2 wt.% PVA-CN-based GPE(G2)(3.36 s/g) and 5 wt.% PVA-CN-based GPE(G5)(0 s/g) proved that higher contents of PVA-CN in GPE ensure the non-flammability.Second, to overcome the poor electrochemical ability of G5, Rs functionalized F7 was used instead of PVA-CN. Unlike G2, only with 2 wt. % of F7 guaranteed the 0 s/g of SET. Non-flammability of 2 wt.% F7-based GPE(FG2) is due to the fluorine moiety scavenge the O• or H•. In the nail penetration test, only the FG2 was not exploded and maintained charged voltage while the nail penetrates the whole pouch cell vertically because of its elasticity.The Rs capability was demonstrated by cyclic voltammetry(CV) with 2,2’-azobisisobutyronitrile(AIBN) and alpha-tocopherol(α-TOH). After α-TOH react with AIBN radicals at the 70 ℃, the oxidation current decreased because of consumption of α-TOH. The Rs capability was calculated by ratio of current retention of α-TOH oxidation current with a same amount of among scavenger additives. The Rs capability of F7 was 214%.Lastly, our findings suggest sufficient non-flammability without battery performances degradation. The capacity retention of FG2 was higher than LE at the 300th Cycles. This is because the fluorine moiety contributed to make LiF-rich SEI layers. The rigid SEI layers and GPE suppressed volume expansion of graphite. Also, the capacity fade was not observed in FG2 with higher current density. The reason for great rate capability is higher lithium-ion conductivity which is a multiplication of ionic conductivity and lithium-ion transference number(tLi+). FG2has 4.82 of lithium-ion conductivity, while 3.63 in LE. Therefore, the mass transfer resistance was not large on the electrode surface due to the higher lithium-ion mobility in FG2.In this work, the non-flammability and battery performance were successfully demonstrated by thermal stability and Rs capability without any battery performances degradation. The thermal stability was enhanced by strong intermolecular forces between polymer chain and polar organic solvents. The radical chain reaction was terminated by fluorine moiety of GPEs matrix. The capacity retention of FG2 was outstanding compared with LE. Therefore, due to the FG2, the battery will be able to ensure non-flammability without degradation of performance. Figure 1

Anionic Additive-Integrated Electrolyte Therapy: Enhancing High-Voltage Stability and Performance in Lithium-Ion Batteries

Significant endeavours have been undertaken to advance the development of eco-friendly, abundant, cost-effective, and high-performance cathode materials for lithium-ion batteries. Among the various contenders for next-generation energy storage systems, spinel LiNi0.5Mn1.5O4 has emerged as a leading high-voltage cathode candidate, owing to its aforementioned benefits. Nonetheless, the widespread adoption of LNMO-based lithium-ion batteries is substantially impeded by the electrochemical instability of conventional carbonate electrolytes above 4.5 V. High-voltage cycling of such batteries results in rapid capacity degradation and metal-ion dissolution from the LNMO electrode into the electrolyte, particularly at elevated temperatures, further causing deposition of metal-ions on anode electrode. Therefore, stabilizing the electrode/electrolyte interface is crucial to achieve improved electrochemical performance of the Li-ion cell at high voltages. The utilization of sacrificial electrolyte additives is regarded as a straightforward and efficacious method to accomplish this objective. These additives form a protective layer on the cathode surface, mitigating electrolyte decomposition and transition metal-ion dissolution and deposition on anode’s surface. Various additives facilitating high-voltage cathode materials have been documented, encompassing fluorides and sulfonates. However, borate salt-containing additives are particularly promising within this context.In the present study, we endeavour to elucidate the surface modifications transpiring on the electrode’s surface when minute quantities of borate-based salt are employed as an additive in the conventional EC:EMC electrolyte for high-voltage operation. We explored the impact of the additive salt in a standard LiPF6-EC/EMC base electrolyte on the discharge capacity and rate performance of the LiNi0.5Mn1.5O4/Graphite based Li-ion cell. The electrochemical behaviour, morphological behaviour, and electrode-electrolyte interphase layer stability on the electrode were meticulously examined using high-resolution transmission electron microscopy (HR-TEM), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These characterisations conformed the presence of an electrode-electrolyte interface forming a thin-layer via the sacrificial decomposition of the utilised additive. The introduction of this salt exhibits favourable effects on enhancing the electrochemical performance of the LiNi0.5Mn1.5O4/Graphite in high-voltage lithium-ion batteries. Notably, the utilised additive excels in mitigating irreversible capacity loss and reducing cycling fade, as it preferentially decomposes and forms a conductive, protective film that impedes subsequent electrolyte decomposition, thereby substantially enhancing cell performance.

Reticular Elastic Solid Electrolyte Interface Enabled by an Industrial Dye for Ultrastable Potassium‐Ion Batteries

The solid electrolyte interface (SEI) is vital to the stability of alkali metal‐ion battery anodes. However, conventional SEIs that lack elasticity will be damaged during the anode's repeated volume expansion, such as in potassium‐ion battery anodes, ultimately resulting in cell failure. Herein, a low‐content additive (pigment green 7, 0.07 wt%) in a conventional carbonate electrolyte to create a reticular elastic SEI with excellent uniformity and good chemical stability is employed. As a result, long‐lasting K||K symmetric cell (over 1400 h), enhanced graphite anode (500 cycles with 97.9% capacity retention), and stabilized perylene‐3,4:9,10‐tetracarboxydiimide cathode (1200 cycles with 82.8% capacity retention) are achieved. Furthermore, the matched graphite||perylene‐3,4:9,10‐tetracarboxydiimide full cell operates stably for more than 200 cycles. This work provides a novel avenue into the rational design of elastic SEIs for advanced anodes.