Stable Solid Electrolyte Interface Film Research Articles

The effect of carboxyl group position of pyrazinedicarboxylic acid on electrochemical performances in lithium ion batteries anode

Conjugate carbonyl compounds are considered to be one of the most promising electrode materials for the next generation of lithium ion batteries. However, most of the published researches focus on the electrochemical performances of conjugated carbonyl compounds, the researches on the structure-activity relationship of such materials are still not enough. In this work, we investigate the structure-activity relationship of pyrazinedicarboxylic acid (Pzdc) anode materials, and the results show that the lithium storage capability of 2, 3-Pzdc is much better than 2, 5-Pzdc and 2, 6-Pzdc. At 32 mA g−1, 2, 3-Pzdc is able to deliver a discharge capacity around 1200 mA h g−1, while 2, 5-Pzdc and 2, 6-Pzdc anodes only exhibit a capacity of 530 and 550 mA h g−1, respectively. Even at 32 A g−1, 2, 3-Pzdc still retains ca. 500 mA h g−1, and shows 1225 mA h g−1 after 400 cycles at 160 mA g−1 charge and 640 mA g−1 discharge. The combination of electrochemical and spectroscopic studies show that the good electrochemical performance of the 2, 3-Pzdc anode is because of the high lithium conductivity, the low resistance, the stable solid electrolyte interface film form on the electrode, as well as the rich lithium storage functional groups.

Unraveling the stabilization mechanism of solid electrolyte interface on ZnSe by rGO in sodium ion battery

Abstract Transition metal selenides have been widely studied as anode materials of sodium ion batteries (SIBs), however, the investigation of solid-electrolyte-interface (SEI) on these materials, which is critical to the electrochemical performance of SIBs, remains at its infancy. Here in this paper, ZnSe@C nanoparticles were prepared from ZIF-8 and the SEI layers on these electrodes with and without reduced graphene oxide (rGO) layers were examined in details by X-ray photoelectron spectroscopies at varied charged/discharged states. It is observed that fast and complicated electrolyte decomposition reactions on ZnSe@C leads to quite thick SEI film and intercalation of solvated sodium ions through such thick SEI film results in slow ion diffusion kinetics and unstable electrode structure. However, the presence of rGO could efficiently suppress the decomposition of electrolyte, thus thin and stable SEI film was formed. ZnSe@C electrodes wrapped by rGO demonstrates enhanced interfacial charge transfer kinetics and high electrochemical performance, a capacity retention of 96.4%, after 1000 cycles at 5 A/g. This study might offer a simple avenue for the designing high performance anode materials through manipulation of SEI film.

Adjusting the interface structure of graphdiyne by H and F co-doping for enhanced capacity and stability in Li-ion battery

The 18–C triangular ring structure of graphdiyne (GDY) can form three-dimensional channel between layers and make GDY an excellent anode material for lithium ion batteries (LIBs). The stable solid electrolyte interface (SEI) film and strong C–F bond formed by fluoride can forcefully enhance the cycle stability in LIBs. Additionally, the stable synthesis of hydrogen-containing carbon material reduces cost and the effective lithium storage of H increases specific capacity. Herein, we propose a strategy of H and F positioning balanced co-doped GDY, combining the lithium storage contributions of H and F elements and achieving an extraordinarily high capacity of 2050 ​mA ​h g−1 at 50 ​mA ​g−1 and only 23% reduction after even 8000 cycles. The fibrous network porous structure can be formed and generate excellent electrolyte infiltration and interface stability with SEI film when H and F is evenly co-doped. This work provides approach to interface structure adjustment that effectively improved lithium storage stability. Besides, the combination approach of positioning substitution and co-doping contributes to high lithium storage capacity and provides reference for elements co-doping.

Boosting rate performance of LiNi0.8Co0.15Al0.05O2 cathode by simply mixing lithium iron phosphate

LiNi0.8Co0.15Al0.05O2 (NCA), a cathode material for lithium-ion batteries (LIBs), is a promising material due to its high specific capacity. However, there are drawbacks like high cost, safety issues, and limited cycle-performance that represent obstacles for commercial applications. This study describes a simple ballmilling method to modify the surface of NCA materials and fill the gaps between particles by LiFePO4 (LFP) cathode to improve its charge/discharge rate. The results show that NCA@5LFP, mixed with 5 wt % LFP, has the best cycling and rate performance, with a higher capacity-retention (89.4% after 200 cycles, at 2C). Post-electrochemical and in-situ analysis reveal more detailed reasons of the observed improvements. The formation of a more stable solid electrolyte interface film in the NCA@5LFP hybrid electrode helps ensure the orderliness of the NCA structure, by reducing the charge-transfer resistance, and increasing the channel for lithium ion de-intercalation. All these factors help improve the battery performance.

A general strategy to construct yolk-shelled metal oxides inside carbon nanocages for high-stable lithium-ion battery anodes

Metal oxides (MOs) are attractive anode materials of Li-ion batteries for the large theoretical capacity, low cost and high density, but suffer from the poor cycling stability owing to the low conductivity, large volume variation, active component loss and instable solid electrolyte interface (SEI) during cycling. Herein, we develop a simple and general strategy to construct the yolk-shelled metal oxides inside 3D hierarchical carbon nanocages (hCNC). The obtained yolk-shelled MO@hCNC provides sufficient interior void to buffers the large volume variation, forms the stable SEI film, and greatly reduces the loss of active components during lithiation/delithiation, meanwhile ensures the fast electron transfer and ions/electrolyte transportation. Both SnO2@hCNC and Fe3O4@hCNC exhibit superior cycling stability and reversible capacity to the most corresponding SnO2- and Fe3O4-based anode materials reported to date. The simple and general approach to the yolk-shelled MO@hCNC is significant for exploring the high-performance energy-storage materials for Li-ion batteries or even beyond.

Pyromellitic dianhydride: A new organic anode of high electrochemical performances for lithium ion batteries

Organic energy storage materials attract extensive attention as a potential alternative for the next generation of lithium ion batteries. However, most of the reported organic electrodes can not achieve a good balance among high capacity, high rate and long cycle-life. In this work, pyromellitic anhydride is adopted as a new anode material for lithium-ion batteries. It exhibits superior electrochemical performances compared to most of the reported organic electrodes. The pyromellitic anhydride anode is able to reversibly deliver a capacity of 1472.2 mAh g−1 at 30 mA g−1. Even at an extremely high current of 30 A g−1, the electrode still retains 562.7 mAh g−1. After a 500 electrochemical cycles at 150 mA g−1 charge and 600 mA g−1 discharge, almost no capacity loss can be observed. The good electrochemical performance of the pyromellitic anhydride anode is because of its excellent lithium conductivity capability, as well as the stable solid electrolyte interface film formed on the electrode.

LiAlCl4·3SO2: a promising inorganic electrolyte for stable Li metal anode at room and low temperature

LiAlCl4·3SO2 is a promising electrolyte used for Li metal batteries. At room and low temperature, a stable solid electrolyte interface film can be formed in LiAlCl4·3SO2 to achieve favorable protection for Li metal anodes. Here, Li|Cu cells with SO2-based inorganic electrolyte (LiAlCl4·3SO2) display higher average coulombic efficiency and more excellent cycling stability compared with a conventional organic electrolyte. Moreover, at 0.5 mA cm−2, the coulombic efficiency of Li|Cu cells with LiAlCl4·3SO2 electrolyte can reach 95% at − 20 °C, while the coulombic efficiency of the conventional organic electrolyte at − 20 °C is only about 79%. Furthermore, LiAlCl4·3SO2 electrolyte is non-combustible. Based on all the experimental results, LiAlCl4·3SO2 is a promising electrolyte candidate for safe Li metal batteries.

Thin Carbon Layer Coated Porous Fe3O4 Particles Supported by rGO Sheets for Improved Stable Sodium Storage

AbstractIron oxide (Fe3O4) is considered as a promising sodium ion anode material due to high capacity, low cost and nontoxic features. However, the main challenges associated with Fe3O4 anodes are structure instability and low initial Coulombic efficiency (∼50%) during charge/discharge process. In this work, thin carbon layer (∼2.5 nm) coated porous Fe3O4 particles (∼ 100 nm) anchored on reduced graphene oxide sheets (Fe3O4@C/rGO) are achieved. Fe3O4@C/rGO composite shows a stable cycling performance of 356 mAh g−1 after 300 cycles at 0.1 A g−1 with a slight decay of 0.098 mAh g−1 per cycle. Moreover, it exhibits a high initial Coubombic efficiency of 74%, superior to the values in most reported literatures for Fe3O4/carbon composites. The excellent electrochemical performance is attributed to the porous structure of Fe3O4 which can accommodate the mechanical stress induced by the volume expansion, and the outside carbon layers which can protect Fe3O4 from electrolyte to form a stable solid electrolyte interface film.

Unraveling the Impact of Ether and Carbonate Electrolytes on the Solid-Electrolyte Interface and the Electrochemical Performances of ZnSe@C Core-Shell Composites as Anodes of Lithium-Ion Batteries.

The recognition of the solid electrolyte interface (SEI) between the electrode materials and electrolyte is limiting the selection of electrode materials, electrolytes, and further the electrochemical performance of batteries. Herein, we report ZnSe@C core-shell nanocomposites derived from ZIF-8 as anode materials of lithium-ion batteries, the electrochemical performances, and SEI films formed on ZnSe@C in both ether and carbonate electrolytes. It is found that ZnSe@C delivers a reversible capacity of 617.1 mA h·g-1 after 800 cycles at 1 A·g-1 in the ether electrolyte, much higher than that in the carbonate electrolyte. Both ex situ X-ray diffraction and X-ray photoelectron spectroscopies reveal that stable SEI films are formed on ZnSe@C in the ether electrolyte while selenium is involved in the formation of SEI films and further dissolved into the carbonate electrolyte because of the concurrent decomposition of electrolytes and insertion of Li+ into ZnSe, which differentiates between the cycling performances of ZnSe@C composites in ether and carbonate electrolytes.

Necklace-like Si@C nanofibers as robust anode materials for high performance lithium ion batteries

Silicon is believed to be a promising anode material for lithium ion batteries because of its highest theoretical capacity and low discharge potential. However, severe pulverization and capacity fading caused by huge volume change during cycling limits its practical application. In this work, necklace-like N-doped carbon wrapped mesoporous Si nanofibers (NL-Si@C) network has been synthesized via electrospinning method followed by magnesiothermic reduction reaction process to suppress these issues. The mesoporous Si nanospheres are wrapped with N-doped carbon shells network to form yolk-shell structure. Interestingly, the distance of adjacent Si@C nanospheres can be controllably adjusted by different addition amounts of SiO2 nanospheres. When used as an anode material for lithium ion batteries, the NL-Si@C-0.5 exhibits best cycling stability and rate capability. The excellent electrochemical performances can be ascribed to the necklace-like network structure and N-doped carbon layers, which can ensure fast ions and electrons transportation, facilitate the electrolyte penetration and provide finite voids to allow large volume expansion of inner Si nanoparticles. Moreover, the protective carbon layers are also beneficial to the formation of stable solid electrolyte interface film.

In-situ reduction derived nitrogen doped carbon anchored cobalt nanoparticles as highly capacity and long life lithium ion battery anodes

A novel composite with embedded cobalt nanoparticles in nitrogen doped carbon (Co@NDC) is synthesized by the in-situ reduction of Co(OH)2 using ionic liquid [HMIm]N(CN)2 as carbon precursor. Due to the special structure, this composite can form more stable solid electrolyte interface (SEI) film than cobalt nanoparticles when used as anode. The Co@NDC electrode shows a high discharge capacity of 1322 mAh g−1 after 850 cycles at 0.5 C, and an extremely long cycle life (436 mAh g−1 after 2400 cycles at 5 C). This excellent electrochemical performance can be attributed to the catalytic lithium-carbon reaction of cobalt nanoparticles, high conductivity of the carbon material, and the thin and stable SEI film.

Liquid-like Poly(ionic liquid) as Electrolyte for Thermally Stable Lithium-Ion Battery.

A liquid-like poly(ionic liquid) (PIL) with a very low glass transition temperature of −51 °C and a thermal decomposition temperature of 202.7 °C was synthesized. A PIL-based electrolyte by mixing this poly(ionic liquid) with additives of 10 wt % propylene carbonate and 0.1 M LiClO4 is proved to be an excellent electrolyte for lithium-ion battery. The obtained PIL-based electrolyte exhibits a high ionic conductivity of 8.3 × 10–5 S cm–1 at 25 °C and 2.0 × 10–4 S cm–1 at 60 °C and a wide electrochemical potential window up to 5.61 V at 25 °C and 4.14 V at 60 °C. The Li/LiFePO4 batteries equipped with this PIL-based electrolyte achieve high capacity, outstanding cycling stability and rate capability at 25 °C, and even improved performance at high temperature like 60 °C. Such excellent performances of batteries are attributed to the formation of stable solid-electrolyte interface film at the lithium-electrolyte interface and the stability of electrolyte during cycling.

Microwave-Irradiation-Assisted Combustion toward Modified Graphite as Lithium Ion Battery Anode

A rapid method to high-yield synthesis of modified graphite by microwave irradiation of partially oxidized graphite (oxidized by H2SO4 and KMnO4) is reported. During the microwave irradiation, electrical arc induced flame combustion of Mn2O7 and vaporization and decomposition of H2SO4 to form O2 and SO2, which helped to decompose graphite within 30 s. The modified graphite boosts its ability to support the intercalation and diffusion of Li+ ions. As an anode material for lithium ion batteries, the modified graphite displays high reversible capacity of 373 mA·h/g, approaching the theoretical value of 372 mA·h/g. Long cycling performance of 410 charge-discharge cycles shows the capacity is retained at 370 mA·h/g, demonstrating superior stability. The improved cycling stability is attributed to the formation of a stable solid electrolyte interface film with the help of in situ formed S-based compounds on a graphite sheet. This work demonstrated a simple and effective method to alter carbon structures for improving energy storage ability.

Baby Diaper‐Inspired Construction of 3D Porous Composites for Long‐Term Lithium‐Ion Batteries

AbstractIn this paper, by using the superabsorbent polymers (SAPs) from baby diaper, the 3D porous composites decorated with NiO and Ni nanoparticles (NNSCs) have been prepared via a facile dissolving‐freeze drying and subsequent annealing reactions. The porous carbon matrix (PCM) derived from the SAPs also provides a continuous highly conductive network to facilitate the fast charge transfer and form a stable solid electrolyte interface film. Furthermore, NNSC can exhibit the high specific capacity and excellent cycle performance as anode materials for lithium‐ion batteries. And more importantly, employing the PCM derived from baby diaper offers a green approach for other energy storage materials.

Electrochemical analysis graphite/electrolyte interface in lithium-ion batteries: p-Toluenesulfonyl isocyanate as electrolyte additive

Lithium plating and dendrite formation can occur on the graphite surface at high current densities. What is more, graphite generates a 10% volume change during cycling, resulting in a solid electrolyte interface (SEI) crack and further electrolyte decomposition. Here, p-Toluenesulfonyl isocyanate (PTSI) as an electrolyte additive is evaluated to overcome the above problem of Li/graphite cells. The results show that the cycling capacity of Li/graphite cell with 0.5wt% PTSI is effectively enhanced at high current densities. Remarkably, we find that a stable SEI film derived from PTSI is generated on the graphite surface. The SEI film can obviously inhibit the reductive decomposition of electrolyte, electrode erosion and LiF formation upon cycling. This additive will provide new avenues for the rational engineering of advanced Li-ion batteries.

SnO2/Sn Nanoparticles Embedded in an Ordered, Porous Carbon Framework for High‐Performance Lithium‐Ion Battery Anodes

AbstractTin dioxide (SnO2) is recognized as one of the most promising anode materials for lithium‐ion batteries. However, the large volume changes of pure SnO2 anodes during Li+ insertion/extraction inevitably result in rapid capacity decay. Herein, the fabrication of microsized, porous SnO2/Sn/carbon (p‐SnO2/Sn/C) composites by a straightforward one‐step hydrothermal process with triblock copolymer Pluronic F‐127 as templating agent and subsequent carbonization is reported. In this composite structure, SnO2/Sn nanoparticles (≈5 nm) are uniformly embedded in an ordered porous carbon matrix to form an interpenetrating framework structure. The ordered porous carbon matrix not only offers three‐dimensional channels for extraction/insertion of Li+ during cycling, but also buffers severe volume changes of the SnO2/Sn nanoparticles. Furthermore, the composite structure also ensures formation of stable solid electrolyte interface films as compared with isolated SnO2/Sn nanoparticles, which efficiently improves the electrochemical stability of the active materials. Thus, the p‐SnO2/Sn/C anode delivers a high reversible capacity of 1016.2 mAh g−1 at 100 mA g−1 after 100 cycles and has remarkable long‐term cycle stability (a charge capacity of 710 mAh g−1 even after 600 cycles at 1000 mA g−1).

Lithium difluorophosphate as an additive to improve the low temperature performance of LiNi0.5Co0.2Mn0.3O2/graphite cells

Lithium difluorophosphate (LiPO2F2) was used as an electrolyte additive to promote the low temperature performance of LiNi0.5Co0.2Mn0.3O2/graphite cells. The impact of LiPO2F2 on the solid electrolyte interface (SEI) film-formation on electrodes was demonstrated by various electrochemical methods and microscopy techniques, such as transmission electron microscopy (TEM), scanning electron microscope (SEM) as well as X-ray photoelectron spectroscopy (XPS), in the pouch cells and half cells. The results showed that the cells containing 1% LiPO2F2 performed 71.9% (−20°C) and 57.93% (−30°C) of initial capacity, while the cells without LiPO2F2 discharged only 49.41% and 9.6% of initial capacity under the same condition. In addition, the enhancement of cyclic performance at 0°C was attributed to a conductive and stable SEI film formed on the graphite by the sacrifice of LiPO2F2, which led to a low impedance and richer content of LiF and Li2CO3 in SEI components, as depicted in XPS.

Oxygen vacancies in SnO2 surface coating to enhance the activation of layered Li-Rich Li1.2Mn0.54Ni0.13Co0.13O2 cathode material for Li-ion batteries

Abstract This work reports the facile surface coating of lithium-rich Li1.2Mn0.54Ni0.13Co0.13O2 cathode material by nano-SnO2 for lithium ion batteries. Thus-obtained nano-SnO2 coated Li1.2Mn0.54Ni0.13Co0.13O2 (denoted as NTO-LMO) material is characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. It is revealed that the SnO2 layer with a thickness of 4–8 nm is uniformly coated on the surface of Li1.2Mn0.54Ni0.13Co0.13O2. This NTO-LMO material exhibits outstanding rate capability and cyclic stability in comparison with pristine material, which should be ascribed to the nano-SnO2 coating layer that limits the side reactions and produces a thin and stable solid electrolyte interface film. More importantly, in contrast to the conventional surface coatings that usually reduce the reversible capacity of active materials, the discharge capacity of our NTO-LMO material increases by 38 mAh g−1 at the current density of 30 mA g−1, which is attributed to the enhanced activation of Li2MnO3 component. The oxygen vacancies in nano-SnO2 coating layer are revealed to facilitate the transfer of high valence state oxygen through the coating layer and be responsible for the promoted activation of Li2MnO3. These insightful findings are very helpful to developing effective strategies for the surface modification of Li-rich oxide materials.

Effects of SEI Formation Additives on Cycle Performance and Surface Morphology in Si-Flake-Powder Anodes

We had reported that an amorphous silicon flake powder (Si LeafPowder®, Si-LP), of which the lateral dimension and the thickness were ~4 μm and 100 nm, respectively, demonstrated superior cycle performances.[1, 2] Cyclability of the Si-LP electrodes was successfully improved by an addition of solid electrolyte interface (SEI)-forming additives such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC). However, the capacity-fading mechanism of the Si-LP electrodes has not been clarified. In order to understand the capacity fading of the Si-LP and effects of additives, variations of impedance components and the morphology changes were investigated. Test electrodes were composed of Si-LP (83.3 wt.%), Ketjen Black (5.6 wt.%) and carboxymethyl cellulose sodium salt (11.1 wt.%), and coated on a Cu foil. The loading of the Si-LP composite was approximately 0.4 mg cm-2. Electrolytes were 1 M LiPF6 dissolved in a mixture of ethylene carbonate and diethyl carbonate (EC+DEC, 1:1 by vol.) with and without additive of 10 wt.% VC or FEC. Charge and discharge tests were conducted at C/2 rate in the CC-CV mode between 1.5 and 0.02 V using a two-electrode coin-type cell. The electrochemical impedance spectroscopy (EIS) was performed using a three-electrode cell in which impedance spectra were obtained by applying an AC voltage of 10 mV over the frequency range of 0.03 Hz to 300 kHz. Surface and cross-sectional morphologies of the Si-LP electrodes after cycling were observed by a scanning electron microscope (SEM) without air exposure. Cyclability of the Si-LP electrodes in the electrolyte with and without FEC is shown in Fig. 1(a). Capacity retention for Si-LP electrode was substantially improved by the FEC-addition, although the discharge capacity at the 100th cycle decreased to 50% of the initial discharge capacity for the Si-LP electrode without FEC. To understand effects of the FEC-addition, EIS measurements were conducted and the SEI resistance (R SEI) was derived from the impedance spectra obtained at 0.1 V in the charging process. The SEI resistance for the Si-LP without FEC increased with increase in cycle number as shown in Fig. 1(b). By the FEC-addition, the SEI resistance was decreased and its increment with cycle number was substantially suppressed in comparison with the case of additive-free, indicating that reductive decomposition of the electrolyte on the Si-LP electrode was suppressed with a stable SEI film derived from FEC. Cross-sectional SEM images of the Si-LP electrodes after 10 and 30 cycles in the additive-free electrolyte are shown in Fig 1(c) and (d). Deposits of reductive products of the electrolyte were confirmed on Si-LPs. The amount of the deposition increased with cycle number, indicating a continuous decomposition of the electrolyte and a growth of SEI layer. The growth of the SEI layer lades an increment of the SEI resistance. Moreover, we found that the thickness of the Si-LP composite electrode was increased drastically by the growth of SEI layer and bending of Si-LPs, leading to a loss of the electric contact between the Si-LPs. Although Si-LPs bended after cycling, pulverization of Si-LPs was not observed. On the other hand, thinner SEI layer was observed on Si-LPs with the FEC-addition, and the expansion of the composite electrodes was suppressed. The stable SEI layer suppresses increment of the SEI resistance. Ensuring the electric-conducting path between active materials by the stable SEI layer is necessary to achieve a superior cycle performance of Si anodes. Acknowledgments: This work was supported by JST-ALCA-SPRING and JSPS-KAKENHI Grant Number 25820335 and 16H04649.

Effects of lithium fluoride coating on the performance of nano-silicon as anode material for lithium-ion batteries

To overcome the capacity fading issue of Si particle upon repeated cycle process, in this study, lithium fluoride (LiF) is introduced to coat commercial nano silicon to form an artificial solid electrolyte interface (SEI) film. After a facile spray drying process, Si nanoparticles are aggregated to form spheres and the LiF is homogenously coated on the surface of Si nanoparticles. Compared with the bare nano-Si, Si/LiF composite shows a huge increase in capacity retention, increasing from 0.8% to 31.2% after 30 cycles. Such improvement results from artificial formation of a stable LiF-based SEI film on the Si surface, reducing the parasitic reaction and thus minimizing the capacity loss during the first lithiation process.