Solid Electrolyte Interphase Layer Research Articles

Recyclable organic radical electrodes for metal-free batteries.

Organic batteries are one of the possible routes for transitioning to sustainable energy storage solutions. However, the recycling of organic batteries, which is a key step toward achieving circularity, is not easily achieved. This work shows the direct recycling of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl) (PTMA) and poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) (PTAm) based composite electrodes. After charge-discharge cycling, the electrodes are deconstructed using a solubilizing-solvent and then reconstructed using a casting-solvent. The electrochemical properties of the original and recycled electrodes are compared using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) cycling, from which it is discovered using time-of-flight secondary ion mass spectrometry (ToF-SIMS) that recycling can be challenged by the formation of a solid-electrolyte interphase (SEI). In turn, an additive is proposed to modify the SEI layer and improve the properties after recycling. Last, an anionic rocking chair battery consisting of PTAm electrodes as both positive and negative electrodes is demonstrated, in which the electrodes are recycled to form new battery. This work gives demonstrates the recycling of composite electrodes for organic batteries and provides insights into the challenges and possible solutions for recycling the next-generation electrochemical energy storage devices.

Ether vs. Carbonate solvents in Na–CuS Batteries: Impact on anode Morphology, SEI Formation, and desolvation dynamics

Traditionally, electrolyte solvents in batteries have been regarded primarily as carrier for ion transporters. Here, we reveal the critical roles of solvents in transforming microscale anode materials into porous nanostructures and in facilitating the formation of thinner, more efficient solid-electrolyte interphase (SEI) layers. Using machine-learning-assisted molecular dynamics simulations combined with density functional theory calculations on Na–CuS batteries, we unveil the significant yet previously unclear impact of solvent choice on solvation/desolvation dynamics, a complex area that has been difficult to resolve with traditional methods. We demonstrate that solvent choice significantly impacts the capacity, particularly the rate performance, primarily due to the desolvation dynamics, thus establishing a direct correlation between solvent selection and battery performance. Our findings highlight DEGDME as the optimal solvent for Na–CuS half-cells, due to its low Na desolvation energy and favorable Na–O bond energy. This leads to exceptional energy capacity (610 mAh/g at 2C) and ultrafast charging capability (520 mAh/g at 30C). This research marks a significant advancement in energy storage technology by demonstrating the crucial role of solvent selection in anode morphology, SEI formation, and desolvation energy optimization.

Mg-Composition Dependent Cycle Stability in Zn<sub>1-x</sub>Mg<sub>x</sub>O Li-ion Battery: Transition from Electronic Transport-Limited to Ionic Transport Limited Cycles

This study explores Mg-composition dependent cycle stability in a Zn<sub>1-x</sub>Mg<sub>x</sub>O Li-ion battery, where battery cycles transition from an electronic transport-limited to an ionic transport limited regime. We investigated the impact of Mg doping in Zn<sub>1-x</sub>Mg<sub>x</sub>O nanocrystals on Li-ion battery performance, focusing on Mg compositions between x=0.05 and x=0.15. Mg composition dependent structural and electrical properties were explored using field effect transistors (FETs) and various microscopic/spectroscopic methods. The electronic conductivity was found to be sensitive to changes in Mg composition. Consistently, the initial capacity decreased with an increase in Mg composition, aligning with the reduction in electronic conductivity due to Mg doping. However, with successive cycles, the capacity became independent of the electronic conductivity, an outcome attributed to the formation of a solid-electrolyte interphase (SEI) and the conversion reactions. Initially, Mg doping reduces electronic conductivity due to increased carrier trapping, leading to lower discharge capacity. However, as cycling progresses, the impact of Mg doping diminishes. The formation of the SEI layer becomes more influential, significantly affecting Li-ion transport. Over time, factors like SEI formation, conversion reaction dynamics, and structural changes within the electrode start to dominate the battery's capacity, rather than the initial electronic conductivity influenced by Mg doping. This understanding can guide the development of materials with lower resistance, facilitating faster charging and discharging rates. More importantly, this study indicates that the initial capacity is closely tied to the conductivity of the Zn<sub>1-x</sub>Mg<sub>x</sub>O material.

LiF-Rich Solid Electrolyte Interphase Formation by Establishing Sacrificial Layer on the Separator.

The formation of a stable solid electrolyte interphase (SEI) layer is crucial for enhancing the safety and lifespan of Li metal batteries. Fundamentally, a homogeneous Li+ behavior by controlling the chemical reaction at the anode/electrolyte interface is the key to establishing a stable SEI layer. However, due to the highly reactive nature of Li metal anodes (LMAs), controlling the movement of Li+ at the anode/electrolyte interface remains challenging. Here, an advanced approach is proposed for coating a sacrificial layer called fluorinated self-assembled monolayer (FSL) on a boehmite-coated polyethylene (BPE) separator to form a stable SEI layer. By leveraging the strong affinity between the fluorine functional group and Li+, the rapid formation of a LiF-rich SEI layer in the cell production and early cycling stage is facilitated. This initial stable SEI formation promotes the subsequent homogeneous Li+ flux, thereby improving the LMA stability and yielding an enhanced battery lifespan. Further, the mechanism behind the stable SEI layer generation by controlling the Li+ dynamics through the FSL-treated BPE separator is comprehensively verified. Overall, this research offers significant contributions to the energy storage field by addressing challenges associated with LMAs, thus highlighting the importance of interfacial control in achieving a stable SEI layer.

In situ high‐quality LiF/Li3N inorganic and phenyl‐based organic solid electrolyte interphases for advanced lithium–oxygen batteries

AbstractLithium metal shows a great advantage as the most promising anode for its unparalleled theoretical specific capacity and extremely low electrochemical potential. However, uncontrolled lithium dendrite growth and severe side reactions of the reactive intermediates and organic electrolytes still limit the broad application of lithium metal batteries. Herein, we propose 4‐nitrobenzenesulfonyl fluoride (NBSF) as an electrolyte additive for forming a stable organic–inorganic hybrid solid electrolyte interphase (SEI) layer on the lithium surface. The abundance of lithium fluoride and lithium nitride can guarantee the SEI layer's toughness and high ionic conductivity, achieving dendrite‐free lithium deposition. Meanwhile, the phenyl group of NBSF significantly contributes to both the chemical stability of the SEI layer and the good adaptation to volume changes of the lithium anode. The lithium–oxygen batteries with NBSF exhibit prolonged cycle lives and excellent cycling stability. This simple approach is hoped to improve the development of the organic–inorganic SEI layer to stabilize the lithium anodes for lithium–oxygen batteries.

1,3,6-Hexanetricarbonitrile as electrolyte additive to inhibit sodium dendrites in sodium-metal batteries

Sodium-metal batteries (SMBs) offer substantial competitiveness owing to their wide elemental distribution and high specific capacity. However, SMBs face safety issues such as unstable properties of the Solid Electrolyte Interphase (SEI) layer due to irregular sodium dendrites. In this paper, we constructed a stable and uniform SEI layer by introducing the 1,3,6-Hexanetricarbonitrile (HTCN) electrolyte additive, replacing the conventional, insoluble nitrate. HTCN facilitates the generation of substances like Na3N with high electrical conductivity on the Na anode surface. This accelerates Na+ shuttling and provides high-flux nucleation sites. Molecular dynamics simulations were employed to elucidate the solvated structure of electrolyte and radial distribution of Na+ after HTCN addition. Moreover, in-situ optical microscopy revealed a stable and robust SEI layer, effectively inhibiting the disorderly growth of sodium dendrites. The superior cycling performance of the Na3V2(PO4)3 (NVP)/Na full cell further demonstrates the addition of HTCN.

Introduction of a nitrate anion with solubility mediator in a carbonate-based electrolyte for a stable potassium metal anode

In this study, sodium nitrate (NaNO3) dissolves in a carbonate electrolyte for K-metal batteries (KMBs) using a dimethylacetamide (DMA) solvent with a higher Gutmann donor number than that of NO3−. The K-metal anode in 0.02 M NaNO3 electrolyte exhibits enhanced stability due to the modified solid-electrolyte interphase (SEI) layer resulting from the preferential reduction of NaNO3. Reduced NaNO3 forms ionically conductive and mechanically robust compounds in the SEI layer. This compound plays a critical role in altering the morphology of electrodeposited K-metal from dendritic to spherical, reducing the barrier energy of nucleation potential for K-ions. These unique features make K-metal highly resistant to dendrite formation and aggressive electrolyte chemistry. Therefore, the K-metal anode in the proposed electrolyte containing 0.02 M NaNO3 additive ensures excellent cycle life with stable Coulombic efficiency in both symmetrical K/K half cells and full-cells coupled with a Prussian green FeFe(CN)6 cathode.

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 %.

Lithium‐Mediated Nitrogen Reduction for Ammonia Synthesis: Reviewing the Gap between Continuous Electrolytic Cells and Stepwise Processes through Galvanic Li─N2 Cells

AbstractElectrochemical N2 reduction reaction (E‐NRR) has recently gained increasing interest within the scientific community, due to the ongoing energy crisis and pursuit of process sustainability. In this scenario, emerging lithium‐mediated (Li‐m) strategies are obtaining promising Faradaic efficiency (FE) and NH3 production rate values. In this work, the Li‐m scenarios are classified and explained toward a more sustainable process. Continuous processes, with a lithium salt and a proton donor in an electrolytic cell, are analyzed and compared with stepwise pathways. Different parameters are summarized in relation to the system stability, for which the importance of a tailored solid electrolyte interphase (SEI) layer emerged. Among stepwise processes, the thermochemical direct nitridation of lithium is discussed together with the recently developed Galvanic Li─N2 cell strategy.

Latent Solvent Induced Reliable Interfacial Chemistry Toward Highly Reversible Zn Anodes

AbstractAqueous zinc‐ion batteries have garnered renewed interest owing to their inherent safety and cost‐effectiveness. However, Zn anode suffers from notorious side reactions and dendrite growth, compromising the battery performance. Designing anion‐containing solvation structures to facilitate the in situ formation of a solid electrolyte interphase (SEI) layer proves effective in protecting Zn anode, yet balancing the inherent interactions between the cations‐solvents and cations–anions remains a significant challenge. Herein, latent solvent (hexafluoroisopropanol) with specific anion‐philic and cation‐phobic properties is introduced, which can remarkably increase Zn(TFSI)2 solubility in water and induce anion‐containing solvation structures. The introduction of latent solvent enables anions to preferentially decompose, giving rise to an anion‐derived SEI layer. More interestingly, the direct anion‐cation interaction endows Zn2+ species with stepwise dehydration, minimizing the adsorption of water on Zn anode. The anion‐derived SEI layer and optimized de‐solvation process work in synergy to enable homogeneous Zn deposition and ensure high reversibility. When coupled with a NaV3O8·1.5H2O (NVO) cathode, the resultant full cell delivers a high‐capacity retention of 87.8% after 2000 cycles at 1 A g−1. This work provides valuable insights into the advanced latent solvent electrolyte design and beyond.

Ionic conductive membrane suitable for sodium metal batteries

Recently, sodium-ion batteries have received great attention primarily due to the scarcity of lithium resources and fluctuations in lithium prices, but sodium-ion batteries have relatively low energy densities. One solution to the low energy density is to employ sodium metal anode, and the risks associated with using metallic sodium could be mitigated by constructing sodium-metal batteries (SMBs) with polymer electrolytes. In this paper, we would like to report a novel gel polymer membrane composed of a cellulose polymer, which not only has a wide electrochemical window, but also has excellent mechanical strength and thermal stability. Moreover, the prepared membrane exhibits high ionic conductivity, thus it can be used as separator and/or electrolyte for ionic batteries. The sodium-metal battery constructed with the prepared gel cellulose electrolyte has been further evaluated by cycling at 0.1C and 60 °C. The solid electrolyte interphase (SEI) layer formed on the surface of the sodium metal anode has been carefully examined using various characterization techniques. The results verify that the ionic-liquids based gel polymer electrolyte (IGPE) is thermally and electrochemically stable, and suitable for high-voltage SMBs.

Is silicon worth it? Modelling degradation in composite silicon–graphite lithium-ion battery electrodes

The addition of silicon into graphite lithium-ion battery anodes has the potential to increase cell energy density. However, understanding the complex degradation behaviour in these composite systems remains a research challenge. Here, we developed a coupled electrochemical–mechanical model of a composite silicon/graphite electrode, including stress-driven crack formation and solid electrolyte interphase layer growth for each material, validated with experimental degradation data from an LG M50T cell. The model reveals self-limiting loss of silicon due to decreasing stress in the silicon as the silicon activity shifts to a lower state-of-charge. Higher C-rates can lead to lower degradation due to lower phase utilisation as voltage cut-offs are reached earlier. Increasing silicon content can reduce the stress in the silicon by distributing reaction current density over more material. Using this model, we explored whether the extra capacity from silicon is generally ‘worth’ the faster degradation compared to graphite-only electrodes. The model shows if you use the silicon, you lose it, as the higher initial capacity is rapidly lost with regular high depth-of-discharge events. However, silicon does have value if it enables full graphite utilisation without range anxiety; if high depth-of-discharge events are minimised then graphite’s superior longevity can be utilised while exploiting silicon’s high specific capacity. The model is integrated into PyBaMM (an open-source physics-based modelling platform); providing the research community and industry with the capability to reproduce our results and further explore the dynamic lifetime behaviour of composite electrodes.

Functionalized interfacial cover design toward pure silicon anode for high power density lithium–ion capacitor

A lithium–ion capacitor, comprising a capacitor–type cathode and battery–type anode, exhibits high power and energy density; however, the integration of different charge storage mechanisms in one cell naturally leads to a kinetic mismatch between the two electrodes, reducing the power density and cycle stability. To solve this problem, high–capacity anode materials with thinner electrodes are required. Silicon, with its high specific capacity, is considered a promising anode material with high energy and power density; however, pure Si anodes undergo rapid capacity fading and exhibit increased internal resistance owing to volume changes during cycling. In this study, both sides of the electrode are covered with functional layers consisting of functionalized herringbone–type carbon nanofibers to protect the Si electrode from degradation. The polar functional groups on the nanofibers weakly interact with the native oxide layer of the Si surface and the carboxyl groups of the binder, ensuring stable contact between electrode materials over repeated cycles. Moreover, the conductive functional cover promotes uniform lithium ion fluxes, aiding the formation of a stable solid electrolyte interphase layer. This study investigates the effects of this strategy on pure Si electrodes by surface morphology analysis, assessment of chemical interactions, and electrochemical testing. This approach has the potential to overcome the degradation of Si electrodes and significantly improve the power and energy density of lithium–ion capacitors.

Catalytic role of in-situ formed C-N species for enhanced Li2CO3 decomposition

Sluggish kinetics of the CO2 reduction/evolution reactions lead to the accumulation of Li2CO3 residuals and thus possible catalyst deactivation, which hinders the long-term cycling stability of Li-CO2 batteries. Apart from catalyst design, constructing a fluorinated solid-electrolyte interphase is a conventional strategy to minimize parasitic reactions and prolong cycle life. However, the catalytic effects of solid-electrolyte interphase components have been overlooked and remain unclear. Herein, we systematically regulate the compositions of solid-electrolyte interphase via tuning electrolyte solvation structures, anion coordination, and binding free energy between Li ion and anion. The cells exhibit distinct improvement in cycling performance with increasing content of C-N species in solid-electrolyte interphase layers. The enhancement originates from a catalytic effect towards accelerating the Li2CO3 formation/decomposition kinetics. Theoretical analysis reveals that C-N species provide strong adsorption sites and promote charge transfer from interface to *CO22− during discharge, and from Li2CO3 to C-N species during charge, thereby building a bidirectional fast-reacting bridge for CO2 reduction/evolution reactions. This finding enables us to design a C-N rich solid-electrolyte interphase via dual-salt electrolytes, improving cycle life of Li-CO2 batteries to twice that using traditional electrolytes. Our work provides an insight into interfacial design by tuning of catalytic properties towards CO2 reduction/evolution reactions.

Rational Design of an In‐Situ Polymer‐Inorganic Hybrid Solid Electrolyte Interphase for Realising Stable Zn Metal Anode under Harsh Conditions

AbstractThe in‐depth understanding of the composition‐property‐performance relationship of solid electrolyte interphase (SEI) is the basis of developing a reliable SEI to stablize the Zn anode‐electrolyte interface, but it remains unclear in rechargeable aqueous zinc ion batteries. Herein, a well‐designed electrolyte based on 2 M Zn(CF3SO3)2‐0.2 M acrylamide‐0.2 M ZnSO4 is proposed. A robust polymer (polyacrylamide)‐inorganic (Zn4SO4(OH)6.xH2O) hybrid SEI is in situ constructed on Zn anodes through controllable polymerization of acrylamide and coprecipitation of SO42− with Zn2+ and OH−. For the first time, the underlying SEI composition‐property‐performance relationship is systematically investigated and correlated. The results showed that the polymer‐inorganic hybrid SEI, which integrates the high modulus of the inorganic component with the high toughness of the polymer ingredient, can realize high reversibility and long‐term interfacial stability, even under ultrahigh areal current density and capacity (30 mA cm−2~30 mAh cm−2). The resultant Zn||NH4V4O10 cell also exhibits excellent cycling stability. This work will provide a guidance for the rational design of SEI layers in rechargeable aqueous zinc ion batteries.

Ethanol as Solvent Additives with Competitive Effect for High-Stable Aqueous Zinc Batteries.

Aqueous zinc-ion batteries are emerging as promising sustainable energy-storage devices. However, their cyclic stability is still a great challenge due to the inevitable parasitic reaction and dendrite growth induced by water. Herein, a cosolvent strategy based on competitive effect is proposed to address the aforementioned challenges. Ethanol with a higher Gutmann donor number demonstrates lower polarity and better wettability on the Zn surface compared with water, which endows ethanol with the ability of minimizing water activity by weakening H bonds and preferentially adsorbing on the Zn electrode. The above competitive advantages synergistically contribute to inhibiting the decomposition of free water and dendrite growth. Besides, an organic-inorganic hybrid solid-electrolyte interphase layer is in situ built based on ethanol additives, where organic matrix suppresses water corrosion while inorganic fillers promote fast Zn2+ diffusion. Consequently, the electrolyte with ethanol additives boosts a high reversibility of Zn deposition, long-term durability, as well as superior Zn2+ diffusibility in both Zn half-cells (Zn||Cu and Zn||Zn batteries) and Zn full cells (Zn||PTCDA and Zn||VO2 batteries). This work sheds light on a universal strategy to design a high-reversible and dendrite-free Zn anode for stable aqueous batteries.

In Situ Polymerized Quasi-Solid Electrolytes Compounded with Ionic Liquid Empowering Long-Life Cycling of 4.45 V Lithium-Metal Battery.

High-voltage resistant quasi-solid-state polymer electrolytes (QSPEs) are promising for enhancing the energy density of lithium-metal batteries in practice. However, side reactions occurring at the interfaces between the anodes or cathodes and QSPEs considerably reduce the lifespan of high-voltage LMBs. In this study, a copolymer of vinyl ethylene carbonate (VEC) and poly(ethylene glycol) diacrylate (PEGDA) was used as the framework, with a cellulose membrane (CE) as the supporting layer. Based on density functional theory calculations, 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI), an ionic liquid, was screened because of its lowest unoccupied molecular orbital energy level as a modifying agent for the in situ P(VECx-EGy)/Pyrz/LiTFSI@CE QSPEs synthesis. Pyr14+, with a lithiophobic alkyl chain, forms a dense positive ion shielding layer on the protruding tips of deposited lithium, facilitating uniform and smooth lithium deposition. Pyr14TFSI assists in constructing a stable solid electrolyte interphase (SEI) layer on the Li surface enriched with LiF, Li3N, and RCOOLi. The modulation of lithium deposition behavior on the anode by Pyr14TFSI ensures stable Li plating/stripping for >1500 h. A Li-Cu cell exhibits stable cycling for >200 cycles at a current density of 0.05 mA cm-2, with an average Coulombic efficiency of 92.7%. In situ polymerization ensures that P(VECx-EGy)/Pyrz/LiTFSI@CE QSPEs exhibit excellent interface compatibility with the anode and the cathode. The CR2032 button cell Li|P(VEC1-EG0.06)/Pyr0.4/LiTFSI@CE|LiCoO2 demonstrates stable cycling with a negligible capacity decay of 0.083% per cycle for >390 cycles at 25 °C and 0.2 C when using a high-voltage LiCoO2 (4.45 V) cathode. Furthermore, a 7.1 mAh pouch cell achieves stable charge-discharge cycles, confirming the pronounced stability of the as-fabricated QSPE at the interfaces of the high-voltage LiCoO2 cathode and Li anode.

Organic Anodes with Nearly 100% Initial Coulombic Efficiency Enabled by Wet‐Chemically Constructed Artificial Solid‐Electrolyte Interphase Film toward High‐Energy‐Density Organic Full Batteries

AbstractLithium‐ion batteries (LIBs) built on inorganic anodes have achieved great commercial success. By contrast, the practical application of organic anode materials encounters key bottlenecks including electronic insulation, high solubility, and poor initial coulombic efficiency (ICE). Among them, improving ICEs (normally 30–60%) faces enormous challenges in both theory and technology, and there has been no substantial breakthrough yet. Herein, a wet chemical pretreatment technology to increase the ICE of maleic acid (MA)‐based anodes from 43.2% to nearly 100% is proposed for the first time, and this strategy demonstrates universal applicability. Typically, the wet chemical pretreatment involves reacting with lithium‐biphenyl to form LixMA intermediates (x = 4–6) and further forming a compact artificial solid‐electrolyte interphase (SEI) film through the spontaneous reaction between active LixMA and battery organic electrolytes. This wet chemically‐constructed artificial SEI layer can almost completely suppress lithium loss in the initial cycle of the MA electrode and significantly boost the actual output energy density, rate capability, and cycling durability of MA anode‐based full batteries. Significantly, the study further demonstrated that a series of organic anode materials with high ICEs can be achieved through similar wet chemical pretreatment. This work will open up the true application of high‐ICE organic anodes in LIBs.

Correlating Graphite Surface with Interphase for Fast‐Charging and Low‐Temperature Operation

AbstractThe properties of graphite surface can not only affect the interaction between graphite and electrolyte but also induce the formation of solid electrolyte interphase (SEI) film. Herein, the graphite surface is purposely treated to incorporate oxygen‐containing functional groups, which facilitates a desired Li2CO3‐rich SEI with high ionic conductivity and good mechanical stability. The modified graphite electrodes exhibit significant enhancement in electrochemical performance during rapid charging at the rate of 15 C, where an impressive capacity of 225 mAh g−1 is still maintained, corresponding to a capacity retention of 60.8%. Moreover, the modified electrodes showcase outstanding performance under wide temperature ranging from −50 to +65 °C, with an amazing capacity retention of 97.6% under −20 °C, the conceivable capacity of 105 mAh g−1 at −50 °C as well as excellent stability at both −20 °C and +65 °C. These findings offer valuable insights into the design of a thin and robust Li2CO3‐rich SEI layer via a facile chemical treatment of the graphite surface.

The effect of annealing and multilayer structure on promoting the electrochemical performance of Al/Si thin film anodes

C/(Al/Si)n/TiO2 multilayer thin films with the controllable number of (Al/Si) layers (n = 1, 2, 3, 4) were prepared by magnetron sputtering. The effect of the inserted Al layers and annealing process on the electrochemical performance of the anodes have been discussed. Among the samples before annealing, C/(Al/Si)4/TiO2 thin film anode exhibits a better capacity retention rate after 500 cycles. The annealing process was performed to facilitate the diffusion of Al and Si layers in the film, improving the conductivity of the anode. The result is a decrease in the resistance and an increase in the Li+ diffusion rate of the anode. The annealing process also forms the Al-Si phase. During the cycling process, the Al-Si phase reacts with the electrolyte to form a Li-Al-Si ternary phase, which can improve the stability of the solid electrolyte interphase (SEI) layer. C/(Al/Si)4/TiO2 thin film anode annealed at 300 °C for 30 min (C/(Al/Si)4/TiO2-30 min) forms a stable block structure during cycling, which can alleviate volume expansion, enhance Li+ diffusion rate and exhibit adaptability to high current densities of the thin film anode. It is shown that C/(Al/Si)4/TiO2-30 min thin film anode obtains an initial discharge capacity of 2419 mA h g−1 and a capacity retention of 80.5 % after 500 cycles. In addition, this thin film anode exhibits superior rate performance, maintaining a capacity of 1453 mA h g−1 after 500 cycles at 5 A/g and a capacity above 1463 mAhg−1 even at 30 A/g.