Anode For Lithium Secondary Batteries Research Articles

Co-synthesis and Electrochemical Investigation of the Nitrogen-Doped Carbon Layer with Metallic Nano Beads on the SiOx Anode for Lithium Secondary Batteries.

The high theoretical capacity (∼2000 mAh g-1) of silicon suboxide (SiOx, with 1 < x < 2) can solve the energy density issue of the graphite anode in Li-ion batteries. In addition, it has an advantage in terms of volume expansion or side reactions compared to pure Si or Li metals, which are considered as next-generation anode materials. However, the loading content of SiOx is limited in commercial anodes because of its low cycle stability and initial coulombic efficiency. In this study, a nitrogen-doped carbon layer with Cu beads (N-C/Cu) derived from copper phthalocyanine (CuPc) is applied to a SiOx electrode to improve its electrochemical performance. The SiOx electrode is simultaneously coated with a Cu- and N-doped carbon layer using CuPc. N-C/Cu synergistically enhances the electric conductivity of the electrode, thus improving its electrochemical performance. The SiOx/N-C/Cu composite has better cyclability and higher capacity (1095.5 mAh g-1) than the uncoated electrode, even after 200 cycles in the 0.5 C condition. In full-cell cycling with NCM811 cathodes, the SiOx (60 wt % of SiOx, with a n/p ratio of 1.1) and graphite-mixed (7.8 wt % of SiOx, with a n/p ratio of 1.1) anodes also show improved electrochemical performances in the same conditions.

Core-Shell-Type Carbon-Coated Lithium Titanium Oxide Composites Derived from Ti-Based Metal Organic Framework As Anode Materials for Lithium Secondary Batteries

Lithium titanium oxide, Li4Ti5O12 (LTO), is one of the most promising anode materials for Li secondary batteries. Although it has a lower specific capacity of approximately 175 mAh/g than does graphite (372 mAh/g), this material shows the unique property of the negligible lattice change in the Li-ion insertion/desertion process, providing excellent high-rate cycling stability. The biggest obstacles of limiting the application of LTO material electrode are poor electrical conductivity and low lithium-ion diffusion coefficient. To overcome these problems, in this work carbon-coated LTO (LTO/C) composites with core-shell-type structure are synthesized and it is derived from Ti-based metal organic framework (Ti-MOF). For the synthesis of the LTO/C composites, Ti-MOF was chemically lithiated by n-BuLi and heated at different temperature (500-800 oC) in an inert atmosphere. According to powder X-ray diffraction analysis, the as-lithiated sample shows an amorphous structure, and the LTO structure is generated after heat-treatment of above 600 oC. Transmission electron microscopy clearly shows core-shell-type LTO particles surrounded by carbon layers with a thickness of 3-5 nm. The electrochemical measurements clearly demonstrate the promising functionality of the present LTO/C composite as anode for lithium secondary batteries. The LTO/C composite obtained by heating at 700 oC show the largest discharge capacity (cal. 152 mAh/g) with good cyclability. The present experimental findings underscore the validity of the use of MOF as a useful platform for new synthetic strategies of carbon coated LTO materials and also for the improvement of their functionality.

Silicon-loaded Lithium-Carbon Composite Microspheres as Lithium Secondary Battery Anodes

Silicon-loaded Lithium-Carbon Composite Microspheres as Lithium Secondary Battery Anodes

Improving High Rate Electrochemical Performance of Patterned Lithium Metal Anode for Lithium Secondary Batteries By Using Dual Salt Electrolyte System

Recently, demand for lithium (Li) secondary batteries has been increasing as the market for mid- to large-size batteries such as electric vehicles (EV) and energy storage systems (ESSs) is expanding. Especially in order to popularize EVs, it is essential to improve the energy density in order to secure mileage. However, using commercialized graphite as an anode material is difficult to increase energy density due to their limited capacity. Li metal is an ideal anode material due to its extremely high theoretical specific capacity (3860 mAh g-1), low density (0.59 g cm-3) and the lowest negative electrochemical potential (‒3.040 V vs. the standard hydrogen electrode). For instance, Li/air and Li/S batteries enable to increase dramatically energy density. However, Li metal has been proposed as a problem of deterioration of cell performance due to dendrite caused by charging / discharging process and battery short circuit. More importantly, Li dendrite-growth lead to safety issue, i.e., thermal runaway, causing a catastrophic satety failure accompanied by fire and smoke. To overcome this problem, many efforts have been devoted to suppress lithium dendrite-growth. Recently, we demonstrated the possibility of using mechanically surface-patterned Li-metal for Li secondary batteries. In our previous work (J. N. Park et. Al), patterned Li-metal anode showed good cycle life at low current density cycling. Still, high current density cycling showed limited cycle life because of bulky Li dendrite formation in the micro-patterned Li-metal holes. These consume more amount of electrolytes during charging/discharging processes. In this work, we applied dual salt system electrolyte on the micro-patterned Li metal to suppress mechanically bulky Li deposition in the micro-patterned Li-metal holes during charging/discharging processes. And then, their electrochemical properties are investigated in detail.

Granular Dendrite Free Effect of CsPF6 as an Electrolyte Additive for Micro Patterned Lithium Metal Anode

To increase lithium secondary batteries energy density, lithium metal with high theoretical specific capacities, low densities, and lowest negative values of electrochemical potential should be used for anode material. However, despite their advantages, the unpredictable lithium deposition of lithium metal anode generating low Coulombic efficiency and safety problem has limited their commercialization until now. So, in order to solve this problem, our group developed regular sized micro patterned lithium metal anode for lithium secondary batteries. This micro patterned lithium metal anode demonstrated great electrochemical performance. But, above specific current density (about 2.4 mA cm-2) cycling, the cell with patterned lithium metal anode gradually lost their original capacity and showed low Coulombic efficiency due to forming granular lithium depositions in the micro patterned lithium metal holes. Luckily, additionally, micro pattern lithium metal anode is simply able to apply others lithium dendrite suppressed methods such as protection layer, electrolyte additive and so on. To remove these potential risk of electrochemical performance, CsPF6 electrolyte additive was introduced in our patterned lithium metal anode. This additive was known for suppressing lithium dendrite growth due to their Self-Healing Electrostatic Shield (SHES) Mechanism. Herein, LMO/Pattern lithium metal coin cells with CsPF6 additive in electrolytes show well protected patterned lithium metal anode surface, enhanced rate capability and extended cycling stability. This is mainly because CsPF6 can relatively help forming dense lithium deposition in pattern lithium metal hole so that bulk electrolyte consumption was suppressed.

Synthesis and Characterization of Silicon/Reduced Graphene Oxide Composites as Anodes for Lithium Secondary Batteries.

Silicon (Si) is one of the most attractive anode materials for lithium secondary batteries because of its large theoretical capacity, high safety, low cost and environmental benignity. However, Si-based anode material needs to overcome the structural change of the solid-electrolyte interphase due to the large volume change during cycling. To resolve these problems of composites by exploiting the superior conductivity, large specific surface area and flexibility of graphene, we have synthesized reduced graphene oxide (rGO)/Si composite electrode via a simple dip-coating method. Nickel foam is used as a current collector and template for the electrode fabrication. At 0.03 wt%, Si concentration, the rGO/Si composite anode presented the excellent cycle performance with large reversible capacity (778 mAh g-1 after 100 cycles). The characteristics of the rGO/Si composites were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman and X-ray photoelectron spectroscopy (XPS). The improved anode performance of the rGO/Si composite anode is ascribed to the rGO serving as a buffer layer, thereby preventing the volume expansion of Si nanoparticles, and provide facile electron pathways.

Biogenous iron oxide (L-BIOX) as a high capacity anode material for lithium ion batteries

Biogenous iron oxide (L-BIOX) produced by Leptothrix ochracea aquatic bacteria, which is an amorphous Fe3+-based oxide that contains Si4+ and P5+ with tube-formed structures, has been studied for practical use as a conversion anode for lithium secondary batteries. L-BIOX has a capacity approximately two times larger than that of graphite. Conductive additives such as carbon nanotubes (CNTs) and Ketjen black (KB), of which the size and surface area are comparable to the primary nanoparticles of L-BIOX, are required to achieve good electrical contacts. Quasi-open circuit voltage (OCV) and X-ray photoelectron spectroscopy (XPS) measurements with respect to the discharge reveal that the conversion reaction occurs and solid electrolyte interphase (SEI) films are formed within the potential plateau area (1.8–1.5 V vs. Li). The water contained in L-BIOX is completely removed by heat-treatment at 400 °C. The elimination of water decreases the first irreversible capacity and improves the cycle performance. Li pre-doping by contact with Li metal realizes 100% coulombic efficiency at the first cycle. A lithium ion cell fabricated with a Li-pre-doped L-BIOX anode and a LiCoO2 cathode exhibits good cycle performance with high capacity retention.

A-few-second synthesis of silicon nanoparticles by gas-evaporation and their self-supporting electrodes based on carbon nanotube matrix for lithium secondary battery anodes

Rapid gas-evaporation method is proposed and developed, which yields Si nanoparticles (SiNPs) in a few seconds at high yields of 20%–60% from inexpensive and safe bulk Si. Such rapid process is realized by heating the Si source to a temperature ≥2000 °C, much higher than the melting point of Si (1414 °C). The size of SiNPs is controlled at tens to hundreds nanometers simply by the Ar gas pressure during the evaporation process. Self-supporting films are fabricated simply by co-dispersion and filtration of the SiNPs and carbon nanotubes (CNTs) without using binders nor metal foils. The half-cell tests showed the improved performances of the SiNP-CNT composite films as anode when coated with graphitic carbon layer. Their performances are evaluated with various SiNP sizes and Si/CNT ratios systematically. The SiNP-CNT film with a Si/CNT mass ratio of 4 realizes the balanced film-based capacities of 618 mAh/gfilm, 230 mAh/cm3, and 0.644 mAh/cm2 with a moderate Si-based performance of 863 mAh/gSi at the 100th cycle.

Development of Areal Capacity of Si-O-C Composites as Anode for Lithium Secondary Batteries Using 3D-Structured Carbon Paper as a Current Collector

To enlarge the areal capacity of Si-O-C composites as an anode for high energy Li secondary batteries, 3D-structured carbon paper is used as a current collector for electrodeposition of Si-O-C composites. For higher surface affinity between organic solvents with carbon paper, surface treatment of carbon paper is carried out using a sulfuric acid-hydrogen peroxide mixture (SPM) solution. The higher deposited Si amounts and areal capacity are obtained by SPM treatment of carbon paper due to its enhanced surface affinity between carbon paper and electrolytes during Si-O-C electrodeposition. In addition, two kinds of organic solvents, propylene carbonate (PC) and ethylene carbonate/diethyl carbonate (EC/DEC), are employed to investigate their suitability for the electrodeposition of Si-O-C composites. As a result, it is confirmed that the Si-O-C composites synthesized by EC/DEC solvents show more stable cycle abilities than in the case of using PC solvents at a high charge current density of 1.0 mA cm−2. This is due to the exfoliation of carbon paper by PC, resulting in fast capacity fading during charge/discharge cycle. Nevertheless, it is confirmed that the use of carbon paper as a substrate for Si-O-C electrodeposition is an effective way to increase deposited Si amounts and discharge areal capacity.

Si-O-C Composites Prepared By Electrodeposition on CNTs/Cu or Carbon Paper Substrate and Electrochemical Performance for Lithium Ion Battery

Silicon have been attracted as promising anode material because of its higher theoretical capacity than commercial graphite (silicon: 4200 mA h g-1, graphite: 372 mA h g-1). We have been reported the novel Si-O-C composite as anode for lithium secondary batteries with high discharge capacity around of 1045 mA h (g of Si)-1 at 2000th cycle and 842 mA h (g of Si)-1 with outstanding cycle ability over 7200 cycles. Nevertheless, it is not easy to increase the thickness of Si-O-C composite for higher areal capacity due to its weak adhesion strength between Si-O-C with current corrector. To solve this problem, we reported the nickel micro-nanocones hierarchical structured (MHS) substrate and carbon nanotubes (CNTs) covered Cu substrate, and Si-O-C was deposited on those of current collectors, resulting in improved areal capacity and deposited Si amounts, 600 mA h cm-1 with Si-O-C deposited on MHS substrate and enhanced deposited Si amounts up to 16.7 % by CNTs/Cu substrate. In this research, the Si-O-C deposited on to CNTs/Cu substrate was used as anode for full-cell test with LiCoO2 (LCO) cathode. The loading amounts of LCO and Si-O-C were controlled to find optimum loading amounts for good-balanced LCO//Si-O-C full cell. Besides, to enhance the areal capacity, carbon paper (CP) which has three-dimensional structure was used as current collector. The Si-O-C/CP was prepared by electrodeposition with two kinds of electrolytes, in PC and EC/DEC bath. Material and electrochemical properties of Si-O-C/CP was measured by FE-SEM, raman spectrum, inductively coupled plasma, and charge/discharge test by half-cell. Acknowledgements This work was partly supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING)” from Japan Science and Technology Agency (JST), Japan.

Synthesis and electrochemical performance of mesoporous SiO2–carbon nanofibers composite as anode materials for lithium secondary batteries

In this study, carbon nanofibers (CNFs) and mesoporous SiO2–carbon nanofibers composite were synthesized and applied as the anode materials in lithium secondary batteries. CNFs and mesoporous SiO2–CNFs composite were grown via chemical vapor deposition method with iron-copper catalysts. Mesoporous SiO2 materials were prepared by sol–gel method using tetraethylorthosilicate as the silica source and cetyltrimethylammoniumchloride as the template. Ethylene was used as the carbon source and passes into a quartz reactor of a tube furnace heated to 600°C, and the temperature was maintained at 600°C for 10min to synthesize CNFs and mesoporous SiO2–CNFs composite. The electrochemical characteristics of the as-prepared CNFs and mesoporous SiO2–CNFs composite as the anode of lithium secondary batteries were investigated using a three-electrode cell. In particular, the mesoporous SiO2–CNFs composites synthesized without binder after depositing mesoporous SiO2 on Ni foam showed the highest charging and discharging capacity and retention rate. The initial capacity (2420mAh/g) of mesoporous SiO2–CNFs composites decreased to 2092mAh/g after 30 cycles at a retention rate of 86.4%.

Preparation and Lithium Storage Performance of NiO/ C@CNT Anode Material

Abstract Core-shell polypyrrole-based carbon@carbon nanotube (C@CNT) was incorporated into nanosheet-assembled NiO microsphere to produce a porous hybrid (NiO/C@CNT) as an anode in lithium secondary batteries. Results show that the resultant NiO/C@CNT exhibits the enhanced capacity and cyclic stability compared with pure NiO and NiO/CNT. The hybrid delivers a reversible capacity of 573 mAh·g−1 at a current density of 50 mA·g−1 over 20 cycles with a capacity retention of 68.6%. The performance improvement results from the conductive buffering of core-shell C@CNT. It is likely that many benefits of C@CNT such as porous structure, large surface area, high electrochemical activity, high electron conductivity and good wettability, facilitate to avoid significant volume change and thus decrease the capacity fading of the electrode during lithiation and delithiation, as well as enhance the mass transfer efficiency.

An ex-situ nitridation route to synthesize Li3N-modified Li anodes for lithium secondary batteries

To overcome the dendrite formation of metallic lithium anodes, polycrystalline Li3N films are coated on Li foil by an ex-situ nitridation method. The electrochemical performances of the Li3N-modified Li electrodes are investigated by galvanostatic charge/discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to determine the optimized nitridation condition. The morphologies and structures for the pure Li and the Li3N-modified Li electrodes, both before and after cycling, are characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The Li3N films on Li surface can efficiently prevent the contact between Li and the electrolyte, and reduce the side reaction, thus suppressing the formation of dendritic lithium effectively.

Effect of electrolyte on cycle performances of the electrodeposited Sn–O–C composite anode of lithium secondary batteries

The electrodeposited Sn–O–C composite anode cycling with LiClO4 delivered stable cycle performances showing discharge capacity of 473 mA h g of Sn−1 with 95% of coulombic efficiency at 100th cycle. However, the anode showed poor cycle performances with LiPF6 delivering discharge capacity of 69 mA h g of Sn−1 at 100th cycle with 70% of coulombic efficiency. Electrochemical investigation performed by cyclic voltammetry and differential capacity plots revealed that the Sn–O–C composite cycling with LiPF6 suffered from retarded phase transition reaction between Li and Sn during charge/discharge process. X-ray photoelectron spectroscopy declared the existence of fluorinated-Sn and LiF. Moreover, energy dispersive X-ray spectroscopy found increase in their amount with repeated cycles. The morphologies of the Sn–O–C composite cycled with LiPF6 showed aggregated particles containing the chemical state of fluorinated-Sn and LiF on its surface. Furthermore, the significant pulverization and aggregation of the active material were observed from the Sn–O–C composite cycled by LiPF6 rather than that of LiClO4, which was probably promoted by the generated HF strongly corroding metallic component.

Electrodeposition of Si-O-C Composite Anode Onto Three Dimensional Structures for Lithium Secondary Batteries

Silicon is one of the most promising materials for lithium secondary battery anodes. However, silicon anodes have a critical drawback to their practical application, which is capacity degradation due to pulverization of the active material by the large volume change of silicon during charge–discharge cycles. To solve the problem, some attempts have been proposed such as a formation of thinner film1, nano-, micro-structure such as nano-wired structure2, core-shell structure, porous structure3, alloying with the third metallic elements4, and so on. Among them, we have proposed Si-O-C composite anode prepared by electrodeposition process. 5-8 The Si-O-C composite anode is composed of silicon oxide (SiOx, 0<x<2) and organic compounds that are derived from decomposed products by the electrochemical co-reduction of Si and the solvent was performed directly on the current collector. 8,9 The Si-O-C anode showed excellent cycle durability, that is the Si-O-C anode delivered ca. 800 mAh/g-Si even over 7000 cycles. However, the Si-O-C composite anode has room to be improved on specific capacity normalized by electrode area, ca. 50 μAh/cm2. To improve the capacity, we applied nanocone-structured substrate as a current collector. Consequently, we succeeded in increasing the thickness of the Si-O-C composite anode, resulting in the capacity of ca. 600 μAh/cm2 (800 mAh/g-Si).7In the present paper, to improve the specific capacity normalized by electrode area, the Si-O-C composite anode was electrodeposited onto three-dimensional structured material, i.e. carbon paper.A carbon paper was treated by sulfuric acid and hydrogen peroxide mixture (SPM) to improve the surface of the carbon paper. The Si-O-C composite was electrodeposited on the carbon paper by using an electrolytic solution which contains 0.5 M SiCl4and 0.5 M tetrabuthylammonium perchlorate / propylene carbonate.Figure 1 shows whole covering of the Si-O-C composite on the carbon paper which is treated by SPM compared, although the covering of the Si-O-C composite on the carbon paper with no treatment is defective (Figure 2). Thus, the SPM treatment improved the coverage of the Si-O-C composite on the carbon paper. Figure 3 shows the discharge capacity of the Si-O-C composite on the carbon paper treated by SPM. The discharge capacity of the Si-O-C composite anodes on the carbon paper delivered more than 1.5 mAh /cm2 which is more than double compared with the our previous work7. Although the half of the capacity was derived from the capacity of the carbon paper, the feasibility of the electrodeposition of Si-O-C composite onto three-dimensional structured materials is demonstrated to be effective to increase the specific capacity normalized by electrode area. Reference 1. T. L. Kulova, A. M. Skundin, Y. V. Pleskov, E. I. Terukov, and O. I. Kon’kov, J. Electroanal. Chem., 600, 217–225 (2007).2. C. K. Chan et al., Nat. Nanotechnol., 3, 31–35 (2008).3. J. Cho, J. Mater. Chem., 20, 4009–4014 (2010).4. K.-M. Lee, Y.-S. Lee, Y.-W. Kim, Y.-K. Sun, and S.-M. Lee, J. Alloys Compd., 472, 461–465 (2009).5. T. Momma, S. Aoki, H. Nara, T. Yokoshima, and T. Osaka, Electrochem. Commun., 13, 969–972 (2011).6. H. Nara, T. Yokoshima, T. Momma, and T. Osaka, Energy Environ. Sci., 5, 6500–6505 (2012).7. T. Hang, H. Nara, T. Yokoshima, T. Momma, and T. Osaka, J. Power Sources, 222, 503–509 (2013).8. T. Osaka, H. Nara, T. Momma, and T. Yokoshima, J. Mater. Chem. A, 2, 883–896 (2014).9. H. Nara, T. Yokoshima, M. Otaki, T. Momma, and T. Osaka, Electrochimica Acta, 110, 403–410 (2013). Acknowledgement This work was supported partially by Advanced Low Carbon Technology Research and Development Program (JST-ALCA) Special Priority Research Area "Next-generation Rechargeable Battery".

Electrochemical properties of nano-sized binary metal oxides as anode electrode materials for lithium battery synthesized from layered double hydroxides

Abstract Electrochemical performance of Ni-V, Ni-Fe and Mg-Fe oxide nano-sized particles obtained from layered double hydroxide (LDH) precursors were investigated as anode of lithium secondary batteries. These binary metal oxides showed very high reversible charge–discharge capacity for conversion reaction with lithium ion and good capacity retention. From the results of ex situ XRD and XANES measurements, it cleared the conversion reaction of the binary metal cation is occurring at the lower voltage range under 1.0 V. Especially for the Ni-V system, the lower hysteresis of voltage and the high capacity of 821 mAh/g in the lower voltage region were obtained owing to four step reduction of vanadium ion under 1.0 V.

Influence of the diffusion-layer thickness during electrodeposition on the synthesis of nano core/shell Sn–O–C composite as an anode of lithium secondary batteries

Electrodeposition of nano core/shell Sn–O–C composite anodes for lithium secondary batteries and improvement of cycle performances by a simple agitation technique.

New Si–O–C composite film anode materials for LIB by electrodeposition

Silicon is one of the most promising materials for lithium secondary battery anodes. However, silicon anodes have a critical drawback to their practical application, which is capacity degradation due to pulverization of the active material by the large volume change of silicon during charge–discharge cycles. This paper reviews recent studies on silicon-based anodes that have attempted to overcome this poor cycle durability through structural control such as through thin films, porous structures, core–shell structures, and by alloying with other metals, and by application of proper binders. Among them, binder-free Si–O–C composite films prepared by electrodeposition exhibit outstanding cycle durability. The origin of this excellent durability is discussed in depth from the standpoint of chemical and morphological changes. Consequently, the combination of active materials such as Si and Li2Si2O5 and inactive materials such as Li2O, Li2CO3, and organic compounds is suggested to result in outstanding properties as a lithium secondary battery anode.

Electrochemically Synthesized Sn-O-C Composite With Nano Core/Shell Structure for Anode of Lithium Secondary Batteries

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Carbon paper substrate for silicon–carbon composite anodes in lithium-ion batteries

We have developed a new Si-based anode for lithium secondary batteries consisting of a carbon paper substrate and Si/C composite deposited on it (Si/C/CP electrode). The Si/C composite was formed by pyrolysis of a slurry consisting of Si power and THF solution of PVC as the carbon precursor.The electrode contains no additional conductive carbon and binder, which supports the tight contact among the Si particle, pyrolytic carbon and carbon paper. The Si/C/CP electrode with the three-dimensional carbon fiber framework of the carbon paper was also advantageous to absorb severe volume changes of silicon particles.The electrode performance revealed that the Si/C/CP electrode prepared from the mixture of Si and PVC with the ratio of 10:90 by weight had a quite high initial capacity of 1720 mAh g−1 and initial Coulombic efficiency of 90%, and also exhibited excellent capacity retention with a reversible capacity of 1200 mAh g−1 even after 100 cycles.