Stable Solid Electrolyte Interface Film Research Articles

Unraveling chemical origins of dendrite formation in zinc-ion batteries via in situ/operando X-ray spectroscopy and imaging

To prevent zinc (Zn) dendrite formation and improve electrochemical stability, it is essential to understand Zn dendrite growth, particularly in terms of morphology and relation with the solid electrolyte interface (SEI) film. In this study, we employ in-situ scanning transmission X-ray microscopy (STXM) and spectro-ptychography to monitor the morphology evolution of Zn dendrites and to identify their chemical composition and distribution on the Zn surface during the stripping/plating progress. Our findings reveal that in 50 mM ZnSO4, the initiation of moss/whisker dendrites is chemically controlled, while their continued growth over extended cycles is kinetically governed. The presence of a dense and stable SEI film is critical for inhibiting the formation and growth of Zn dendrites. By adding 50 mM lithium chloride (LiCl) as an electrolyte additive, we successfully construct a dense and stable SEI film composed of Li2S2O7 and Li2CO3, which significantly improves cycling performance. Moreover, the symmetric cell achieves a prolonged cycle life of up to 3900 h with the incorporation of 5% 12-crown-4 additives. This work offers a strategy for in-situ observation and analysis of Zn dendrite formation mechanisms and provides an effective approach for designing high-performance Zn-ion batteries.

Lithium-conducting phosphates as artificial solid-electrolyte interphase on silicon anode for supreme lithium storage

Silicon (Si) anode is an ideal material for next-generation lithium-ion batteries due to its high specific capacity. Unfortunately, the fragmentation and reconstruction of solid electrolyte interface (SEI) film caused by volume expansion during the (de)lithiation is still a problem to be overcome. Constructing a stable SEI film on Si surface through interface engineering is a very effective strategy to improve the electrochemical performance. In this work, we construct lithium-conducting phosphates (Li3PO4, denoted as LPO) as SEI film and SiOx buffer layer on Si surface. The obtained Si@SiOx@LPO anode retains 2015 mAh g−1 after 100 cycles at 0.2 A g−1 with a capacity retention of 73.6%, and 1636 mAh g−1 after 500 cycles at 1 A g−1 with a capacity retention of 81.7%, which is significantly higher than the Si anode under the same conditions, respectively. In addition, in/ex-situ tests demonstrate that Si@SiOx@LPO anode has faster lithium-ion diffusion and structural reversibility. The analysis shows that LPO has higher mechanical strength and provides better ionic conductivity. On the other hand, SiOx buffer layer can not only reduce the volume expansion of Si, but also reduce the energy barrier between Si and LPO interface and increase the electrical conductivity. Therefore, this work provides a novel strategy for boosting electrochemical performance by artificial SEI and surface modification.

Pre‐Doping of Dual‐Functional Sodium to Weaken Fe─S Bond and Stabilize Interfacial Chemistry for High‐Rate Reversible Sodium Storage

AbstractFerrous sulfides with the high theoretic capacity are the promising anode for sodium ion batteries. However, capacity fading and inferior rate capability still hinder their practical application. In this work, Na‐doped Fe7S8 microrods with cationic vacancies and weakened Fe─S bond are constructed through a facile and scalable sulfurized route. The experimental results combined with theoretical analysis thoroughly reveal the generation of Fe vacancies and weakened Fe─S bond strength induced by sodium doping, which modulates the energy band structure of Na‐doped Fe7S8, provides more active sites, and accelerates the sodiation/desodiation reaction kinetics, simultaneously. Moreover, the pre‐doping sodium delivers a strong guiding effect on the formation of thin and stable solid electrolyte interface films. As the result, the optimal sample exhibits the excellent sodium storage performance, including the high and stable reversible capacity (674 mAh g−1 after 200 cycles at 0.5 A g−1 and 503 mAh g−1 after 1500 cycles at 10 A g−1), superior rate capability, and increased initial coulombic efficiency. Furthermore, the full cell paired with commercial Na3V2(PO4)3 also displays the outstanding cyclic stability with 95.9% capacity retention at 0.5 A g−1 after 100 cycles.

Can We See SEI Directly byNaked Eyes?

Stable solid electrolyte interface (SEI) is the key to improve the electrochemical performance of lithium metal batteries (LMBs). However, there are still many puzzles about SEI film that have not been well explained, due to the complexity of electrochemical reactions involving in SEI formation and the absence of direct observation methods for SEI. Here, this work realizes the direct observation of SEI by skillfully designed fluorescent tracers acting as an SEI film-forming additive for electrolytes. These fluorescent tracers have three important moieties: an olefin group for polymerization on anode surface so as to participate in SEI film formation during charge/discharge cycles, a polar group for Li-ion conduction, and an AIEgen for fluorescent tracing. Therefore, the tracers participate in SEI film-forming and result in a shining SEI film. This shining SEI film with intrinsic fluorescence signal allows direct observation and quantification on the distribution, relative abundance, and macro morphology of SEI. These fluorescent tracers can also reveal the SEI formation growth destruction regularity during charge/discharge cycles. Several summarized typical macro morphologies and evolution stages of SEI will enrich knowledge and understanding of SEI and help to gain insight into the interaction between electrolyte and anode, electrochemical performance, and cycle life of batteries.

Amorphous TiO2 shells: an Essential Elastic Buffer Layer for High-Performance Self-Healing Eutectic GaSn Nano-Droplet Room-Temperature Liquid Metal Battery.

Gallium-based alloy liquid metal batteries currently face limitations such as volume expansion, unstable solid electrolyte interface (SEI) film and substantial capacity decay. In this study, amorphous titanium dioxide is used to coat eutectic GaSn nanodroplets (eGaSn NDs) to construct the core-shell structure of eGaSn@TiO2 nanodroplets (eGaSn@TiO2 NDs). The amorphous TiO2 shell (~6.5 nm) formed a stable SEI film, alleviated the volume expansion, and provided electron/ion transport channels to achieve excellent cycling performance and high specific capacity. The resulting eGaSn@TiO2 NDs exhibited high capacities of 580, 540, 515, 485, 456 and 426 mAh g-1 at 0.1, 0.2, 0.5, 1, 2 and 5 C, respectively. No significant decay was observed after more than 500 cycles with a capacity of 455 mAh g-1 at 1 C. In situ X-ray diffraction (in situ XRD) was used to explore the lithiation mechanism of the eGaSn negative electrode during discharge. This study elucidates the design of advanced liquid alloy-based negative electrode materials for high-performance liquid metal batteries (LMBs).

Effects of Butadiene Sulfone as an Electrolyte Additive on the Formation of Solid Electrolyte Interphase in Lithium-Ion Batteries Based on Li4Ti5O12 Anode Materials.

In this study, butadiene sulfone (BS) was selected as an efficient electrolyte additive to stabilize the solid electrolyte interface (SEI) film on the lithium titanium oxide (LTO) electrodes in Li-ion batteries (LIBs). It was found that the use of BS as an additive could accelerate the growth of stable SEI film on the LTO surface, leading to the improved electrochemical stability of LTO electrodes. It can be supported by the BS additive to effectively reduce the thickness of SEI film, and it significantly enhances the electron migration in the SEI film. Consequently, the LIB-based LTO anode in the electrolyte containing 0.5 wt.% BS showed a superior electrochemical performance to that in the absence of BS. This work provides a new prospect for an efficient electrolyte additive for next-generation LIBs-based LTO anodes, especially when discharged to low voltage.

Construction of a LiF-Rich and Stable SEI Film by Designing a Binary, Ion-, and Electron-Conducting Buffer Interface on the Si Surface.

Stabilizing a solid electrolyte interface (SEI) film on the Si surface is a prerequisite for realizing silicon (Si) anode applications. Interfacial engineering is one of the effective strategies to construct stable SEI films on Si surfaces and improve the electrochemical performance of the Si anodes. This work develops a silver (Ag)-decorated mucic acid (MA) buffer interface on the Si surface and the obtained Si@MA*Ag anode retains 1567 mAh g-1 after 500 cycles at 2.1 A g-1 and exhibits 1740 mAh g-1 at 126 A g-1, which are significantly higher than those of the bare Si anode of 247 and 145 mAh g-1 under the same conditions, respectively. Analysis indicates that the improved electrochemical performance is because of the depressed volume effect of the Si particles and the sustained integrity of the electrode laminate during cycling, the enhanced lithium diffusion on the Si surface, and the improved electronic conductivity of the Si anode, as well as the facilitated formation of inorganic components in the SEI film.

Effect of halogen-nitrate heterogeneous additives in carbonate-ether mixed electrolytes on inhibiting the growth of Li dendrites

Li metal is recognized as the most promising anode for Li metal batteries due to its high energy density. However, Li dendritic growth is one of the critical obstacles as the presence of this formation may lead to short circuits which will result in the fatal safety hazards like fire and explosion. Developing electrolytes which stabilize the solid electrolyte interface (SEI) film on Li/electrolyte interface to inhibit the Li dendritic formation is still challenging. Among the different electrolytes, few are reported based on LiNO3-carbonated electrolyte because of the low solubility of LiNO3 in carbonated solution. Here, the new advanced electrolyte based on halogen ions (XC1—, Br—, I—) dissolved in a mixture of vinyl carbonate, dimethyl carbonate and dimethyl ether (EC:DMC:DME) on inhibiting Li dendrites was investigated systematically. The highly smooth surface of Li metal could be obtained by adopting the LiBr-LiNO3 electrolytes. The formed stable and homogeneous SEI film fundamentally decreases the nucleation sites for dendritic Li and establishes ideal matrix for the even Li deposition. The Li metal thus shows improved cycling in LiBr-LiNO3 mixed electrolyte which may be the crucial for inhibit dendrite growth intrinsically.

Highly effective solid electrolyte interface on SnO2@C enabling stable potassium storage performance

The property of solid electrolyte interface (SEI), which is related to the nature of electrolyte, directly affects the electrochemical performance of electrode materials in potassium ion battery. In this work, the potassium storage performance of a composite SnO2@C was studied in two different electrolytes of 0.8 M KPF6/EC + DEC (KPF-ED) and 3 M KFSI/DME (KFSI-DME), and its correlation with the generation and properties of SEI film was explored and analyzed based on physicochemical characterizations and density functional theory (DFT) calculations. It was revealed that the superior potassium storage performance of SnO2@C when coupled with KFSI-DME electrolyte was originated from the thin inorganic-rich SEI film generated mainly from decomposition of KFSI salt, which could diminish internal resistance, promote charge transfer and improve electrolyte stability in PIB. While the thick organic SEI film formed in KPF-ED electrolyte was derived mainly from decomposition of the solvents, its continuous generation led to increasing electrolyte consumption and difficult charge transfer, resulting in poor potassium storage performance of SnO2/C as anode material. This work offers a valuable guidance to the construction of robust and stable SEI film by optimizing the electrolyte composition to boost potassium storage performance of electrode materials.

Fe/Fe3C modification to effectively achieve high-performance Si–C anode materials

For obtaining high-capacity and long cycling silicon–carbon based anodes used in lithium-ion batteries, there is an urgent need to rationally construct a stable solid electrolyte interface film and load a high proportion of silicon content.

3D Carbiyne Nanospheres Boosting Excellent Lithium and Sodium Storage Performance.

Reasonable design of electrode materials with specific morphology and structure can efficiently improve the metal ions storage and transmission properties of metal ion batteries. Here the preparation of spirobifluorene-based three-dimensional carbiyne nanosphere (SBFCY-NS) that is composed of spirobifluorene (SBF) and alkyne bonds is reported. Benefiting from the rigid spatial structure of SBF, numerous precursors are coupled through the connection of acetylene bonds, extending to form solid nanospheres. Abundant storage spaces and convenient multi-directional transmission paths for metal ions are available inside the three-dimensional (3D) carbiyne structure. Thus, SBFCY-NS is applied as efficient anode for lithium-ion battery and sodium-ion battery. The good stability of SBFCY-NS-based electrode and its improved Coulombic efficiency can be attributed to the special morphology of nanospheres, which can easily form thin and stable solid electrolyte interface film on the surface. Those results further promote the preparation of spherical carbon-based materials with abundant pores that can be applied in the field of electrodes.

NiSb@PEO Hollow Nanospheres with Stabilized Structure for Improved Sodium Storage

AbstractAntimony has a high theoretical capacity, is widely used as an anode material for sodium‐ion batteries (SIB). However, the reversible sodiation/desodiation causes the structure collapse of the materials and then a rapid capacity fade. To solve this issue, the rationally designed NiSb@PEO (PEO, polyethylene oxide) hierarchical hollow nanospheres are successfully synthesized via the combination of hydrothermal and galvanic replacement methods. The unique hierarchical hollow nanospheres can alleviate volume expansion and mechanical stress, maintaining structural integrity during cycling. The PEO coating offers a highly conducive network and is conducive to forming stable solid electrolyte interface film on the surface of NiSb nanospheres. In addition, the nanospheres can shorten the transport pathway for the charged species. Benefiting from these structural advantages, NiSb@PEO hollow nanospheres as anodes for SIB display excellent sodium storage properties. At the current density of 100 mA g−1, the initial charge specific capacity of the NiSb@PEO anode is 446 mAh g−1, and the capacity retains 82.5% after 100 cycles. NiSb@PEO can maintain a reversible capacity of 284 mAh g−1 even at a high current density of 1600 mA g−1.

Isatin anhydride as multifunctional film-forming additive to enhance cycle life of high-voltage Li-ion batteries at elevated temperature

High-voltage Ni-rich based lithium-ion batteries with long-term cycled life can be obtained by reasonable regulation of the nonaqueous electrolyte components. Herein, a novel multifunctional electrolyte additive, isatin anhydride (IAn) is dedicated to construct stable solid-electrolyte-interface (SEI) films on the both Ni-rich layered LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode and graphite anode in a high-voltage pouch cell. Electrochemical tests reveal that IAn can significantly enhance the long-term cycling performance of the graphite/NCM523 full-cell at high voltage and high temperature. The pouch cell containing 1.0 wt% IAn shows an excellent capacity retention of 92.3% after 200 cycles between 3.0 and 4.5 V at 1.0C under 45 °C condition. In contrast, the cell without IAn appears a lower cycle performance after 192 cycles while the capacity retention decrease to 18.3%. Such obvious improvement of electrochemical performance contributes from the formation of thin and stable SEI films at two electrodes’ surfaces, leading to restraining the electrolyte decomposition and protecting material structures on the both cathode and anode.

One‐dimensional bunched Ni‐V2O3@C@CNT for superior performance lithium‐ion batteries and hybrid capacitors

AbstractIn this paper, by using the bamboo‐like carbon nanotubes (BCNTs) from sulfonated polymer nanotubes (SPNTs), the 3D porous sugar‐coated haws stick‐like composites decorated with V2O3 and Ni nanoparticles (NV@C@CNT) have been prepared via a facile solution method and subsequent annealing reactions. The porous carbon matrix derived from the SPNTs provides a continuous highly conductive network to facilitate the fast charge transfer and form a stable solid electrolyte interface film. This engineering protocol toward electrode architectures/configurations endows integrated NV@C@CNT anodes with large specific capacity (895.6 mAh g–1 at 0.2 A g–1 after 100 cycles), good operation stability, excellent rate capabilities, and prolonged cyclic life span. To prove their potential real applications, we have established the NV@C@CNT//FCNT lithium ion capacitors (LICs), which is capable of showing high energy densities, power densities, and long cycle stability. This work provides a scalable, simple, and efficient evolutionary method for the production of NV@C@CNT electrode materials, providing useful inspiration and guidance for the anodic applications of metal oxides in next‐generation power sources.

Highly infiltrative micro-sized Cu2Se as advanced material with excellent rate performance and ultralong cycle-life for sodium ion half/full batteries

Appropriate material is the key to improve the energy and power density of sodium ion batteries. Herein, monoclinic Cu2Se is acquired by a facile one-pot solid method using Cu foil and Se power as the raw materials without use of expensive reagents and sophisticated instruments. Cu2Se exhibits preeminent cycling and rate properties. Concretely, Cu2Se represents reversible capacity of 264 and 241 mAh g−1 at 0.1 and 10 A g−1, as well as high capacity retention of ≈100% over 1000 cycles at 1 A g−1. When Cu2Se is applied as anode to assemble full battery with Na3V2(PO4)2F3@rGO, this battery exhibits a largest energy density of 97 Wh kg−1 (with a power density of 117 W kg−1) and a biggest power density of 1180 W kg−1 (with energy density of 59 Wh kg−1) based on the gross mass of cathode and anode active materials. A combination of ex-situ X-ray diffraction, transition electron microscopy tests and first-principle calculations demonstrate a reversible transformation between Cu2Se and Cu exists in the discharge-charge process. Stable solid-electrolyte interface film, highly infiltrative electrode and capacitive Na + storage behaviours are in favor of the excellent property. The preeminent electrochemical performance indicates that Cu2Se is a highly desirable anode material for high-performance sodium ion batteries.

Effects of charging protocols on the cycling performance for high-energy lithium-ion batteries using a graphite-SiOx composite anode and Li-rich layered oxide cathode

High-energy lithium-ion batteries (LIBs) using Si-based anode and Li-rich layered oxide (LLO) cathode suffer severe capacity degradation during cycling, which is directly affected by the charging protocols. In this paper, the effect of constant current (CC) and constant current-constant voltage (CC-CV) charging on the cycling performance of graphite-SiOx/LLO pouch-type batteries is studied. Unexpectedly, after 300 cycles, the batteries under the CC-CV protocol show capacity retention of 71.22%, batteries under the CC protocol, however, show capacity retention of only 64.02%. For the batteries using the CC protocol, the electrochemical test results reveal an unstable change in the electrode/electrolyte interface resistance and bigger lithium ion diffusion resistance. The postmortem analyses further indicate a solid electrolyte interface (SEI) film with lower chemical stability and a greater loss of active lithium and Si in the anode. Compared with the CC protocol, the batteries under the CC-CV protocol possess a more stable SEI film and a smaller loss of active lithium and Si. This work has certain reference significance for optimizing the charging protocol.

Artificial SEI for Superhigh-Performance K-Graphite Anode.

Although graphite with its merits of low cost, abundance, and environmental friendliness is a potential anode material for potassium ion batteries (PIBs), it suffers from a limited cycle life due to a severe decomposition of the solid electrolyte interface (SEI) in organic electrolytes. Herein, a simple and viable method is demonstrated for the first time through which an ultra‐thin, uniform, dense, and stable artificial inorganic SEI film can be prepared on commercial graphite anodes and used with traditional carbonate electrolytes to achieve PIBs with long‐cycle stability and high initial Coulombic efficiency (ICE). Specifically, such commercial graphite anodes exhibit a long‐term cycling stability for more than 1000 cycles at 100 mA g−1 (a reversible capacity of around 260 mAh g−1) and a high average CE (around 99.9%) in traditional carbonate electrolytes with no discernable decay in capacity. More importantly, the commercial graphite anodes with the artificial inorganic SEI film in traditional carbonate electrolytes can deliver a high ICE of 93% (the highest ICE ever reported for PIBs anodes until now), which improves the performance of the PIB full cell. Considering the high ICE and long cycle stability performance, this study can promote the rapid deployment of PIBs on a commercial scale.

Research progress of fluorine-containing electrolyte additives for lithium ion batteries

The construction of Solid Electrolyte Interface (SEI) film in Li-ion batteries with functional electrolyte additives is able to passivate the active material surface and inhibit the decomposition of the electrolyte continuously. In addition, safety issue is also an important factor restricting the large scale application of present lithium-ion batteries. Therefore, the additives for film-forming and safety enhancement are a class of cost-effective components that promote the application and development of batteries. Fluorine is a kind of “bipolar” element, which has strong electronegativity and weak polarity. Fluorine-containing electrolyte additives have excellent kinetic reactivity, which can preferentially generate stable SEI films and uniform Cathode-Electrolyte Interface (CEI) films to effectively improve the electrochemical performance of the batteries. Meanwhile, fluorine-containing electrolyte additives can also be used as flame-retardants to improve safety performance. In this review, we summarize the research status of fluorine-containing additives in recent years and elaborate its reaction mechanisms of improving battery performance. Finally, a personal perspective on the future of the development of fluorine-containing additives is presented.

Oriented-Redox Induced Uniform MnO2 Coating on Ni3S2 Nanorod Arrays as a Stable Anode for Enhanced Performances of Lithium Ion Battery.

Cost-effective transition metal chalcogenides have aroused wide consideration as alternative anode materials in lithium ion batteries (LIBs) on account of their elevated lithium activity and considerable theoretical capacity. However, the significant challenge caused by the large volume change and shuttle effect of polysulfides during Li ion insertion/extraction severely restricts their practical application. In this work, the uniform MnO2 coating layer with a tunable thickness on Ni3S2 nanorod arrays has been achieved through a mild oriented-redox reaction by taking advantage of the mixing valence of Ni in Ni3S2 [(Ni2+)2(Ni0)(S2-)2]. The core/shell structured nanorod arrays directly used as anode materials of LIBs demonstrate remarkably improved lithium storage performance including high rate capacity and long cycle life, which deliver a discharge capacity of 662 mA h g-1 for 150 cycles at 0.5 C, corresponding to an elevated capacity retention of 90.7%. The improved electrochemical performances can be assigned to the generation of stable solid electrolyte interface films and suppression of the shuttle behavior with the protection of the MnO2 coating layer on Ni3S2 nanorod arrays.

Rational Design of Sb@C@TiO2 Triple-Shell Nanoboxes for High-Performance Sodium-Ion Batteries.

Antimony is an attractive anode material for sodium-ion batteries (SIBs) owing to its high theoretical capacity and appropriate sodiation potential. However, its practical application is severely impeded by its poor cycling stability caused by dramatic volumetric variations during sodium uptake and release processes. Here, to circumvent this obstacle, Sb@C@TiO2 triple-shell nanoboxes (TSNBs) are synthesized through a template-engaged galvanic replacement approach. The TSNB structure consists of an inner Sb hollow nanobox protected by a conductive carbon middle shell and a TiO2 -nanosheet-constructed outer shell. This structure offers dual protection to the inner Sb and enough room to accommodate volume expansion, thus promoting the structural integrity of the electrode and the formation of a stable solid-electrolyte interface film. Benefiting from the rational structural design and synergistic effects of Sb, carbon, and TiO2 , the Sb@C@TiO2 electrode exhibits superior rate performance (212 mAh g-1 at 10 A g-1 ) and outstanding long-term cycling stability (193 mAh g-1 at 1 A g-1 after 4000 cycles). Moreover, a full cell assembled with a configuration of Sb@C@TiO2 //Na3 (VOPO4 )2 F displays a high output voltage of 2.8V and a high energy density of 179Wh kg-1 , revealing the great promise of Sb@C@TiO2 TSNBs as the electrode in SIBs.