Si Thin Film Anodes Research Articles

Alternating Si/C Thin-Films as Model Anode Material for Lithium-Ion Batteries

Graphite is currently the state-of-art material for the anode-side of lithium-ion batteries (LIB) with a theoretical capacity of 372 mAh g-1. However, its technological potential is already largely exhausted, shifting research focus to other materials, such as silicon (Si) with its high theoretical capacity (3579 mAh g-1) [1]. However, Si cannot be used on its own because of its low electrical conductivity. Moreover, it suffers from a strong increase in volume and amorphization during lithiation, which is the primary origin of several degradation mechanisms, e.g. as pulverization, delamination and an unstable solid electrolyte interface. There are various approaches to counteract these issues, amongst them the structuring of Si into nanowires or hollow structures [2]. Silicon is most often used with graphite in a composite material, due to decades of experience in graphite synthesis an application [3].In this work we investigate anodes consisting of alternating Si and C thin-films with a layer thickness of a few hundred nanometers each. In general, Si thin-film anodes show a higher performance than its bulk counterparts [4]. The layers are produced by deposition from the gas phase. This process enables good adhesion between the particles and the substrate, which can counteract delamination and provide a longer cycle life. Additionally, it can also be performed in a binder-free fashion, thereby reducing the need for inactive electrode components.The alternation of carbon and silicon layers improves the electrical conductivity and also separates the silicon layers from each other aiding to reduce the mechanical stress caused by volume expansion. The characterization of the layers is done by cross sectional SEM, EDX and AFM. Furthermore, the crystallinity of the deposited layers is determined via XRD. The manufacturing process influences the morphology of the layers, which in turn affects the electrochemical properties. For this reason, galvanostatic cycling and electrochemical impedance spectroscopy are subsequently carried out in a coin cell type Swagelok half-cell setup with 2- and 3-electrode arrangements. Constant current cycling is used to investigate the long-term stability of the cells in order to analyze the change in the respective Si layers as a function of their distance from the surface. In addition, the electrodes are analyzed post-mortem via SEM and XRD to investigate which degradation mechanisms play a role in the observed behavior.[1] Kasavajjula, U. et al., Nano- and bulk-silicon-based insertion anodes for lithium-ion secondary cells, J. of Power Sources 163 (2), 1003 – 1039, 2007.[2] Wu, H., Cui Y., Designing nanostructured Si anodes for high energy lithium ion batteries, Nano Today 7 (5), 414 – 429, 2012.[3] You, S. et al., Design Strategies of Si/C Composite Anode for Lithium-Ion Batteries, Chem. Eur. J. 27 (48), 12237 – 12256, 2021 [4] Graetz, J. et al., Highly reversible Lithium storage in nanostructures Silicon, Electrochem. Solid-State Lett. 6 (9), A194, 2003.

Revealing the Role, Mechanism, and Impact of AlF 3 Coatings on the Interphase of Silicon Thin Film Anodes (Adv. Energy Mater. 41/2022)

Solid Electrolyte Interphases In article number 2201859, Aurora Gomez-Martin, Tobias Placke, and co-workers discuss the role, mechanism, and impact of AlF3 coating on Si thin film anodes. The observations were done in different (de-)lithiation states. AlF3 transforms to Li-Al-F compounds with higher ionic conductivity, thus, increasing cycling stability. This study provides significant insights into the solid electrolyte interphase behavior with regard to the functional coating layer.

Propelling performance of silicon thin film lithium ion battery by appropriate dopants

Although pristine silicon (Si) has been employed as a high-capacity anode material, high performance of Si-based lithium-ion battery (LIB) still remains challenging constrained mainly by low intrinsic electrical conductivity of the semiconductor. This drawback can be addressed by doping Si with group III and V elements; nevertheless, a systematic study on the doping species is rarely reported. Herein, the effects of dopants (boron and arsenic) in Si thin film anodes, prepared by electron beam evaporation from different target materials (including pristine, p-type, and n-type Si), on the performance of LIB are investigated. In a coin cell configuration, the doped Si films are inferior to the pristine counterparts in terms of irreversible capacity loss at the first circle, possibly due to incorporation of more lithium ions with a higher conductivity in the former. Intriguingly, boron and arsenic ions are demonstrated as regulating dopants that can deteriorate (for the former) or enhance (for the latter) the capacity retention and rate capabilities of the pristine Si-based LIBs. Electrochemical impedance spectroscopy and microstructure characterizations reveal that the high electrical conductivity and chemical reactivity of boron ions with electrolytes aggravate the formation and propagation of cracks into the depth during cycling and thicken the thickness of solid electrode interphase, consequently increasing charge transfer impedance. This study clarifies the working mechanisms of different doping species in the Si thin film anodes in response to electrochemical cycling and shed light on the improved performance of thin film based LIBs with appropriate dopants.

Electrochemical properties of the Si thin-film anode deposited on Ti-Nb-Zr shape memory alloy in Li-ion batteries

Lithium-ion batteries (LIBs) are widely used, and extensive research has been conducted on new electrode materials. Silicon has been widely studied as an anode material. However, Si has a problem which is the large volume expansion. This study improved the electrochemical properties of Si thin films by employing a Ti-Nb-Zr SMA as a replacement candidate. The electrodes were prepared using two-step DC magnetron sputtering, followed by heat treatment to improve the adhesion between the Si thin film and the Ti-Nb-Zr film of the electrodes. X-ray diffraction confirmed that the SMA changed from the β (BCC) phase structure to the α (HCP) crystalline phase because of the volume changes arising from the Li-Si reactions during the lithiation/delithiation process. Additionally, the heat treatment significantly improved the adhesion between the active materials and substrate, improving the internal charge transfer bond and the martensite properties of the alloy allows it to work in the full sense. This study highlights a high-capacity, long cycle life, and free-standing electrode improvement by combining the shape-memory behavior recrystallization mechanism of heat-treated superelastic passive Ti-Nb-Zr for Si anode materials.

P‐Doped SiOx/Si/SiOx Sandwich Anode for Li‐Ion Batteries to Achieve High Initial Coulombic Efficiency and Low Capacity Decay (Small Methods 3/2022)

Inside Front Cover In article number 2101052, Kim, Yoon, Cho, and co-workers provided new sandwich-structured trilayer Si thin-film anodes demonstrating enhanced electrical conductivity and Li-ion diffusion coefficient from the synergy between structural properties and P-doping. Consequently, a Si anode with the highest initial Coulombic efficiency of 90.4% is achieved, thereby exhibiting superior electrochemical properties as anode material for advanced Li-ion batteries.

Quantifying lithium loss in amorphous silicon thin-film anodes via titration-gas chromatography

Silicon with a high theoretical capacity (3,579 mAh/g) is a promising anode candidate for lithium-ion batteries. However, commercialization is still impeded by low Coulombic efficiency, caused by solid electrolyte interphase (SEI) formation and trapped lithium (Li)-silicon (Si) alloy during repeated volume change. Quantifying capacity losses from each factor is crucial to formulate rational design strategies for further improvement. In this work, titration-gas chromatography and cryogenic transmission electron microscopy are applied to characterize the evolution of trapped Li-Si alloy and SEI growth in a silicon thin-film anode. It is found that continuous growth of the SEI is the dominant factor for lithium inventory loss during cycling, with only a marginal increase in trapped Li-Si alloy. This study offers a quantitative approach to differentiate Li in the SEI from trapped Li in Li-Si alloy through a silicon thin-film anode, providing unique insights into identifying critical bottlenecks for developing Si anodes. Li loss in silicon anode is a combination of SEI formation and trapped Li-Si alloy TGC quantifies the amount of trapped Li-Si alloy Cryo-TEM reveals the trapped Li-Si alloy intermix with SEI Growth of SEI is the dominant factor for capacity decay in Si thin-film anodes Silicon-based anodes for use in lithium-ion batteries are promising, but their fast degradation is not fully understood. Bao et al. apply gas titration chromatography for trapped Li-Si alloy quantification, revealing that interphase-consumed lithium is the primary reason for inferior cycle stability.

Influence of fluoroethylene carbonate on the solid electrolyte interphase of silicon anode for Li-ion batteries: A scanning force spectroscopy study**Project supported by the State Grid Technology Project, China (Grant No. DG71-17-010).

Silicon is an important high capacity anode material for the next generation Li-ion batteries. The electrochemical performances of the Si anode are influenced strongly by the properties of the solid electrolyte interphase (SEI). It is well known that the addition of flouroethylene carbonate (FEC) in the carbonate electrolyte is helpful to improve the cyclic performance of the Si anode. The possible origin is suggested to relate to the modification of the SEI. However, detailed information is still absent. In this work, the structural and mechanical properties of the SEI on Si thin film anode in the ethylene-carbonate-based (EC-based) and FEC-based electrolytes at different discharging and charging states have been investigated using a scanning atomic force microscopy force spectroscopy (AFMFS) method. Single-layered, double-layered, and multi-layered SEI structures with various Young’s moduli have been visualized three dimensionally at nanoscale based on the hundreds of force curves in certain scanned area. The coverage of the SEI can be obtained quantitatively from the two-dimensional (2D) project plots. The related analysis indicates that more soft SEI layers are covered on the Si anode, and this could explain the benefits of the FEC additive.

Understanding the effect of p-, n-type dopants and vinyl carbonate electrolyte additive on electrochemical performance of Si thin film anodes for lithium-ion battery

Amorphous silicon (Si) is one of the most prospective high performance anode material for lithium-ion batteries and thin films of this material are promising for microbattery applications. Undoped, p- and n-type doped Si thin films were deposited by madgnetron sputtering on a three-dimensional current collector designed to accommodate the volume expansion of anode upon charge-discharge cycling, improve the active material adhesion, and to enhance the rate capability of the anode. The designed Si thin film anodes with and without doping were first investigated in lithium cell using various electrochemical techniques confirming the positive effect of doping on their performance. Raman spectroscopy was performed before and after cycling the electrodes to further elucidate such effects. The trends in change of an electrolyte during first lithiation/delithiation were observed by in situ Raman technique. Along with this, the morphology features of a solid electrolyte interphase (SEI) layer formed on the surface of the electrode and its modifications upon addition of 5% vinyl carbonate (VC) to the electrolyte were studied. The n-type doping and unique SEI layer formed with poly(VC) polymeric species suppressed the electrode crack formation preventing the capacity loss due to the material disintegration upon cycling, which resulted in an outstanding cycling performance of Si thin film with the capacity of 1305 mAh g−1 retained over 400 cycles.

(Invited) Mitigation of Electrode Swelling of Pure Si Nano-Flake Anode for Advanced Lithium-Ion Batteries

The poor cyclability of pure Si electrodes is attributed to crack formation and pulverization of Si active material due to a large volume expansion and contraction during charging and discharging, respectively. It is thus important to suppress the physical stress induced by the large volume changes to improve the cyclability of Si electrodes. We designed a Si powder with a flake shape (Si LeafPowder®, Si-LP, OIKE & Co., LTD.) with 100 nm in thickness and 3-5 mm in lateral dimension, and have reported that Si-LP electrodes have a high initial discharge capacity (ca. 2,500 mAh g-1) and good cycleability (Fig. 1) [1]. Another serious problem of Si anode is a swelling of the electrode owing to irreversible microstructural changes of Si nano-flakes upon cycling (Fig. 2) [2]. The Si-LP sheets in a composite electrode were substantially deformed during alloying/de-alloying cycling and formed the multi-folded layered structure on repeated cycling. Furthermore, many voids, which could accommodate volume changes of Si, were formed on repeated cycling. The multi-folded layered structure with many voids enabled the stable battery operation of the Si-LP electrodes. Though good cycleability is obtained, the observed electrode swelling during cycling (Fig. 3) is not affordable for practical use. In this talk, we present some mitigation methods developed for suppression of electrode swelling of Si-LP anode and Si thin film anode, including the effects of additives (VC, FEC in Fig.4) [2], the effects of particle size, the effects of oxide content [3], the effects of pre-film formation [4], the effects of artificial SEI film [5], etc. This research was supported by Japan Science and Technology Agency (JST) ALCA-SPRING and Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number 16H04649.

A multiphysics model that can capture crack patterns in Si thin films based on their microstructure

Fracture in silicon anodes has fascinated the electrochemistry community for two decades, as it can result in a 80% capacity loss over the first few electrochemical cycles and is the limiting factor in commercializing such high capacity anodes. Although numerous experimental data exist illustrating severe fracture patterns and their dependence on the scale of the microstructure, no theoretical model has been able to re-produce and capture such behaviour. In this article, a multi-physics phase-field damage model is presented that can accurately capture the long standing problem of dry bed-lake crack patterns observed for Si thin film anodes. A promising aspect of the model is that, in addition to accounting for Li-ion diffusion, it can explicitly capture the microstructure, and therefore when applied to a Si film with a thickness below 100 nm no fracture was observed, which is consistent with experiments. As fracture in continuous thin films is random, micron-hole patterned Si films were also fabricated and cycled, resulting in ordered crack patterns. The proposed model was able to capture these elaborate, yet ordered, crack patterns, further validating its efficiency in predicting damage during lithiation of Si. This paves the way to using multiscale modeling for predicting the dimensions that limit and control fracture during lithiation, prolonging hence the electrode lifetime.

High performance sandwich structured Si thin film anodes with LiPON coating

The sandwich structured silicon thin film anodes with lithium phosphorus oxynitride (LiPON) coating are synthesized via the radio frequency magnetron sputtering method, whereas the thicknesses of both layers are in the nanometer range, i.e. between 50 and 200 nm. In this sandwich structure, the separator simultaneously functions as a flexible substrate, while the LiPON layer is regarded as a protective layer. This sandwich structure combines the advantages of flexible substrate, which can help silicon release the compressive stress, and the LiPON coating, which can provide a stable artificial solid-electrolyte interphase (SEI) film on the electrode. As a result, the silicon anodes are protected well, and the cells exhibit high reversible capacity, excellent cycling stability and good rate capability. All the results demonstrate that this sandwich structure can be a promising option for high performance Si thin film lithium ion batteries.

The role of thermal annealing on the microstructures of (Ti, Fe)-alloyed Si thin-film anodes for high-performance Li-ion batteries.

Here, we studied the effect of thermal annealing on the microstructure and cyclic stability of a (Ti, Fe)-alloyed Si thin-film fabricated by a simple sputtering deposition method for Li-ion battery (LIB) anodes. The anode samples annealed at different temperatures (300–600 °C) were subjected to microstructure analysis and LIB performance test. The (Ti, Fe)-alloyed Si thin-film anode delivered a high capacity of 1563 mA h g−1 for 100 cycles at 0.1 A g−1 with nearly 100% capacity retention. Post-mortem analysis using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) disclosed the microstructural changes of the cycled anodes, revealing that (Ti, Fe) silicides served as a structural buffer against the large volume change of active Si during cycling for enhanced LIB performance.

Graphene Coated Ni Foam As a Current Collector for N-Type Doped Si Thin Film Anode for Li-Ion Batteries

Thin film silicon (Si) has gained a significant attention as an anode material for Li-ion batteries (LIBs), since its nanostructure retains structural integrity through minimizing the volume variation. However, 2D Si thin film experiences delamination from the current collector, and loss of electrical contact leads to further capacity fading. To overcome this issue, recent scientific investigations have shown that the 3D structure of electrodes (porous, rough-surface, etc.) is capable of suppressing volume changes upon lithiation/delithiation and providing large contact area between active material and current collector. Here, we propose a novel electrode material for LIBs that comprises of Si on graphene coated Ni foam (G-Ni). Porous Ni foam serves as 3D structured highly electroconductive network, and graphene layer was employed with the purpose of improving adhesion and electrochemical stability of Si thin film electrode. Magnetron sputtering was used to deposit n-type doped amorphous Si thin film on G-Ni. Chemical vapor deposition (CVD) was applied to obtain a few layer graphene (FLG) on catalytic Ni foam. The as-grown anode material was tested in a half-cell configuration with metallic lithium as a counter and reference electrode. The results were compared with n-type doped amorphous Si thin film on pristine Ni foam. Galvanostatic cycling performance was evaluated in the voltage range from 0.1 to 1.5 V at a current density of ~ 32 µA cm-2. Si-G-Ni anode exhibited the initial areal capacity of around 141 µA cm-2 and the stable reversible areal capacity of around 80 µA cm-2 over 100 cycles. Si-Ni anode shows an initial capacity of 91 µA/cm-2 with a rapid capacity fading to approximately 30 µA cm-2 at 100th cycle. The results of characterization and electrochemical tests will be presented at the conference. Figure 1

Low-density silicon thin films for lithium-ion battery anodes

Density of sputter deposited silicon (Si) thin films was changed by a simple working gas pressure control process, and its effects on the cycling performance of Si films in Li-ion batteries as anodes was investigated. Higher gas pressure results in reduced film densities due to a shadowing effect originating from lower mean free path of sputter atoms, which leads to a wider angular distribution of the incoming flux and formation of a porous film microstructure. Si thin film anodes of different densities ranging from 2.27g/cm3 (film porosity ~3%) down to 1.64g/cm3 (~30% porosity) were fabricated by magnetron sputtering at argon pressures varying from 0.2Pa to 2.6Pa, respectively. High density Si thin film anodes of 2.27g/cm3 suffered from an unstable cycling behavior during charging/discharging depicted by a continuous reduction in specific down to ~830mAh/g at the 100th cycle. Electrochemical properties of lower density films with 1.99g/cm3 (~15% porosity) and 1.77g/cm3 (~24% porosity) got worse resulting in only ~100mAh/g capacity at 100th cycle. On the other hand, as the density of anode was further reduced down to about 1.64g/cm3 (~30% porosity), cycling stability and capacity retention significantly improved resulting in specific capacity values ~650mAh/g at 100th cycle with coulombic efficiencies of >98%. Enhancement in our low density Si film anodes are believed to mainly originate from the availability of voids for volumetric expansion during lithiation and resulting compliant behavior that provides superior mechanical and electrochemical stability.

Silicon thin film anodes coated on micron carbon-fiber current collectors for lithium ion batteries

Si thin films have been sputter deposited on vapor grown carbon-fibers and used as the anode materials for lithium ion batteries. A common issue for the Si anodes is the volume expansion during charge–discharge, leading to severe capacity fading. In this study, micron carbon-fibers (MCFs) are used as the current collectors to ease the volume-change induced stress, and significantly improve the cycling stability. The MCFs were fabricated using thermal chemical vapor deposition on stainless steel substrates. The Si films can be coated on MCFs as characterized by field emission scanning electron microscopy. The electrochemical properties of Si thin film anodes with various Si/MCFs ratios were investigated. The larger quantity of MCFs, the higher specific capacities can be obtained after 200cycles for a given amount of Si. The cycling stability is enhanced under low Si/MCFs ratios. After 200 charge–discharge cycles, the Si anode deposited on suitable amount of MCFs shows a well rounded surface with very few cracks. The results indicate that the combination of Si anodes and MCFs current collectors can effectively reduce the volume-change induced stress, and enhance the cycling stability.

Ultrasmall Li2S nanoparticles anchored in graphene nanosheets for high-energy lithium-ion batteries.

Li2S has a high theoretical capacity of 1166 mAh g−1, but it suffers from limited rate and cycling performance. Herein we reported in-situ synthesis of thermally exfoliated graphene−Li2S (in-situ TG−Li2S) nanocomposite and its application as a superior cathode material alternative to sulfur. Li2S nanoparticles with the size of ~8.5 nm homogeneously anchored in graphene nanosheets were prepared via chemical reduction of pre-sublimed sulfur by lithium triethylborohydride (LiEt3BH). The in-situ TG−Li2S nanocomposite exhibited an initial capacity of 1119 mAh g−1 Li2S (1609 mAh g−1 S) with a negligible charged potential barrier in the first cycle. The discharge capacity retained 791 mAh g−1 Li2S (1137 mAh g−1 S) after 100 cycles at 0.1C and exceeded 560 mAh g−1 Li2S (805 mAh g−1 S) at a high rate of 2C. Moreover, coupling the composite with Si thin film anode, a Li2S/Si full cell was produced, delivering a high specific capacity of ~900 mAh g−1 Li2S (1294 mAh g−1 S). The outstanding electrode performance of in-situ TG−Li2S composite was attributed to the well dispersed small Li2S nanoparticles and highly conductive graphene nanosheets, which provided merits of facile ionic and electronic transport, efficient utilization of the active material, and flexible accommodation of volume change.

Cycling performance of density modulated multilayer silicon thin film anodes in Li-ion batteries

The high volumetric expansion/contraction of silicon (Si) anodes in Li-ion batteries by about ∼400% during lithiation/delithiation causes considerably high stress followed by cracking, pulverization, and the loss of electrical contact; and finally results in capacity fading and failing. In this work, we present a new density modulated multilayer Si thin film anode approach, which can provide a robust high capacity electrode for Li-ion batteries. Alternating high and low density layers have been achieved by simply changing the working gas pressure between low and high values, respectively during magnetron sputter deposition of Si thin film anodes. Our results reveal that density modulated Si films can provide a high coulombic efficiency up to 99% and reversible specific capacity as high as ∼1700 mAh g−1 after 50 cycles. Low-density layers are believed to be performing as compliant layers during volume change making the films more durable compared to conventional Si film anodes. The results of this work can lead to Si thin film anode materials with superior capacity and mechanical stability compared to conventional Si anodes.

Mechanism Study of Crack Formation at Si Thin Film Anodes with Different Crystalline during Lithiation/Delithation

Thin film electrodes have the advantage for fundamental study owing to the ability to not use binder and conductive additive in testing them as anodes. Particularly, Si thin film electrodes have attracted the most attention due to their superior cyclic performance and high initial coulombic efficiency. It is well known that the problem is crack formation which leads to poor cycle ability during charge/discharge at Si thin films.In order to study the behavior of crack formation at Si anodes with different crystalline, amorphous Si (a-Si) thin films have been treated by laser annealing technique. When the heat exceeds the melting point of the a-Si, the Si melt and it generally form polycrystalline structures (p-Si) during re-solidification.Crystalline of a-Si is dramatically transformed to p-Si of cylindrical column type whose diameter ranges from tens of nanometers to hundred nanometers in p-Si thin film by the laser annealing as shown in Fig. 1.We prepared two adjacent Si patterns, whose size is 30 μm × 30 μm, with different crystalline. At initial stage, we found that the behavior of crack formation was very different in term of shape, size, and density of cracks.In this work, the cracking feature of Si films with different crystalline after first and 30th cycles has been investigated.Fig.1. Optical and cross-sectional TEM images of a-Si, and p-Si thin film.

In Operando Neutron Reflectometry Measurements Demonstrate Structural Stability in Thin Film Silicon Anodes for Lithium Ion Batteries

Despite its incredibly high theoretical capacity (~4200 mA-h/g), implementation of Si electrodes as high-capacity Li-battery anodes is hindered by poor mechanical durability. Si lithiation is accompanied by very high mechanical strain values, with nearly 370% volume expansion at maximum capacity, which typically leads to fracture and pulverization of the material and eventual battery failure. While numerous strategies have been employed to improve the durability of Si anodes, including nano-structured anode architectures, composite anode materials, and protective coatings, efforts have yet to identify a Si anode design that is mechanically robust and maintains a stable anode capacity. At least part of the difficulty is due to a lack of fundamental insight into the correlation between structure, mechanical properties, and function for Si anodes, owing to a paucity of in situ techniques to definitively observe them. In this presentation, we report the structural and composition changes in an amorphous thin-film silicon anode with a protective Al sub-oxide (AlOx) capping layer, using in operando neutron reflectivity (NR) and electronic impedance spectroscopy (EIS) measurements. NR measurements were carried out in situ on an operating Li half-cell at various charge states over six shallow charge-discharge cycles. These measurements quantify the correlation between mesoscopic strain and the degree of lithiation in a 10-nm thick amorphous silicon thin-film anode, which expands and contracts with repeated cycling (Figure 1). Results demonstrate the mechanical durability of both the Si thin-film anode and the protective AlOx layer, which maintain their low surface roughness and film integrity over the course of the measurements. While the macroscopic strain of the Si shows significant non-linearity with Li content after several shallow charge-discharge cycles, in agreement with previous reports1, careful inclusion of a-Si microstructural effects (via direct measurement of the a-Si porosity) reveal that the volumetric strain for the solid portion of a-Si thin films varies linearly with lithium content (Figure 2). Results demonstrate that the porosity is eliminated during the expansion that accompanies lithiation, and is then recovered during subsequent de-lithiation. Furthermore, it is shown here that the delithiated a-Si porosity does not vary significantly over the course of the measurements – ranging from 10.0 [5.4 – 28.0]% in the as-deposited state to 13.1 [10.02 – 15.73]% after 6 shallow charge and discharge cycles – demonstrating the structural reproducibility of the thin-film anode.

Improving the performance of silicon anode in lithium-ion batteries by Cu2O coating layer

The influence of a 200 nm Cu2O coating layer on the electrochemical performance of an 800 nm Si thin-film anode was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge measurements. The electrochemical performance of the Si thin-film anode was improved by the coating layer. The coated Si anode exhibited higher values of conductivity in comparison with the pristine Si anode. Scanning electron microscopy images of the anodes after cycling test showed that the coated Si anode after cycling test had less cracks than the pristine Si anode. The galvanostatic charge/discharge measurements reveal that the cyclability and rate capability of the coated Si thin-film anode were better than the pristine Si thin-film anode.