Thin-film Rechargeable Lithium Batteries Research Articles

A new neutron depth profiling spectrometer at the JCNS for a focused neutron beam

A new neutron depth profiling (NDP) spectrometer has been designed and built for the use at a high intensity focused cold neutron beam of the reflectometer MARIA at the Heinz Maier-Leibnitz Zentrum (MLZ, Germany). The extremely high neutron flux at the sample position of MARIA joined with the multiple charged particle detectors allows less than 10 s sampling rate and paves the way to study the kinetics of Li ions in thin-film microbatteries. The performance of the spectrometer with standard calibration samples and amorphous thin films is presented; possibilities to operando study the Li distribution inside thin-film rechargeable lithium batteries are discussed.

Improvement of Power Characteristics of Thin Film Battery By Li3PO4-Li4SiO4 Electrolyte

Introduction Recently, all-solid-state thin-film rechargeable lithium batteries (TFBs) have expected to be used in various applications such as wireless sensor, smart device and other small devices for an auxiliary power supply. The TFBs are fabricated by forming each layers (i.e. cathode, electrolyte, anode and current collectors) mainly using physical vapor deposition process1,2). As a solid electrolyte, lithium phosphorus oxynitride (LiPON) thin film has been used commonly due to same advantages as no grain-boundary, isotropic property, less electronic conductivity and electrochemical stability. Ionic conductivity of LiPON thin film has been reported ~3.3 x 10-6 S/cm at 25 deg.C3), but it is lower compared with other solid electrolyte4). It is necessary to reduce the internal resistance of TFBs for applying to the device as described above. We tried to improve internal resistance used by Li3PO4-Li4SiO4 (LPO-LSO) electrolyte. Experimental LPO-LSO film was prepared by RF sputtering with 4 inch LPO-LSO target (Toshima manufacturing Co.). The LPO-LSO films were prepared by 0.1 Pa, 0.25 Pa and 0.6 Pa. LiPON film was prepared by RF magnetron reactive sputtering method with lithium phosphate (LPO; Li3PO4) target and N2 gas by 0.25 Pa. The substrate was glass wafer. The cathode film (LiCoO2) was prepared by RF and DC spattering method. The anode film (Metal Li) was prepared by vacuum evaporation method. Acrylic monomer was coated on the anode surface, covered with barrier lid, and cured by ultraviolet light for formation as an encapsulation. The LPO-LSO films quality were measured by FT-IR and SEM. The fabricated TFB cells were investigated by electrical and electrochemical properties at room temperature. Result and discussion Fig.1 shows the nyquist plot of Half-cell (Li/LPO-LSO/Pt, Li/LiPON/Pt) prepared by each pressure. The bulk resistance of LPO-LSO film prepared by 0.1 Pa and 0.25 Pa are lower than the bulk resistance of LiPON film. And the pressure condition of lowest bulk resistance was 0.25 Pa. Fig.2 shows the nyquist plot of TFB that electrolyte were LPO-LSO and LPO-LSO/LiPON . Two semi-circle were observed TFB that electrolyte is only LPO-LSO. We thought 1st semi-circle was the bulk resistance of LPO-LSO and 2nd semi-circle was the interfacial resistance between LPO-LSO and LiCoO2 because 2nd semi-circle was not observed in half-cell of LPO-LSO. We could improve the interfacial resistance by insertion of LiPON film (100nm) between LPO-LSO and LiCoO2. These results show LPO-LSO/LiPON electrolyte improved internal resistance of TFB. References J. B. Bates, N. J. Dudney, G. R. Gruzalski, R. A. Zuhr, A. Choudhury, C. F. Luck and J. D.Robertson, J. Power Sources, 43, 103 (1993).T. Jimbo, P. Kim and K. Suu, Energy Procedia, 14, 1574 (2012).Xiaohua Yu, J. B. Bates, G. E. Jellison, Jr., and F. X. Hart, J. Electrochem. Soc., 144, 524 (1997).N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y.Kato, S. Hama, K. Kawamoto and A. Mitsui, Nature Materials, 10, 682 (2011). Figure 1

Electrochemical Properties of Amorphous Nb2O5 Thin Film and Its Application to Rechargeable Thin Film Lithium Ion Batteries

IntroductionThe past few years have seen an increasing interest in the development of wireless sensor networks. But the limited available energy source is one of the major bottlenecks, which are limiting the wireless sensor technology from mass deployment. Micro energy harvesting is the most promising solution towards autonomous sensor nodes by providing low cost, permanent, and maintenance-free energy source to wireless sensor nodes. Because many harvesting devices could only capture low levels of ambient energy, very small batteries are required for energy storage and intermittent use. Compared to liquid electrochemical batteries with limitation of life span, thin film batteries with flexible charging models and excellent cycle life are very promising for paring with a variety of energy harvesting devices. Thin-film rechargeable lithium or Li-ion batteries have been investigated extensively. So far, positive-negative electrode combinations of LiCoO2-Li, LiMn2O4-Li, TiS2-Li, LiCoO2-SnO and LiMn2O4-V2O5 have been reported. Active Li requires an extra-protective layer to exclude entry of open air. Further, the voltage of the batteries containing Li electrode during charge-discharge processes is restricted to prevent degradation by over-charge or over-discharge. In the electrochemical conversion of oxides system, the initial Li2O formation is irreversible and a significant initial capacity loss is observed. On the other hand, V2O5 is toxic and moisture-sensitive. For practical applications, Nb2O5 displayed relatively good charge-discharge performance and stability although the poor crystallinity of films fabricated through low-temperature processes. In this study, we report on electrochemical properties of amorphous Nb2O5thin film and its application to rechargeable thin film batteries. Experimental. Nb2O5 thin films are deposited using an RF magnetron sputtering equipment (ISP-400, ULVAC) and the thicknesses of these thin films were controlled by the sputtering time. During the deposition, the substrate temperature, the sputtering pressure and the RF power were kept at room temperature, 1 Pa and 100 W, and the sputtered gas (O2/Ar) composition of 1:9 was maintained to minimize the loss of Oxygen. The electrochemical properties of Nb2O5 thin film electrodes were investigated in a liquid electrolyte (1 M LiPF6 in EC + DMC (EC/DMC = 1/1 v/v) )using head-type cells. A Li foil and 20 μm PBS separator were used as the counter electrode and separator. These half-cells were assembled in an Ar-filled glove box. The charge and discharge measurements were carried out using a source-meter (Keithley 2400) with the applied various charge-discharge currents and the cutoff voltages of between 1.0 and 3.0 V. In addition, thin-film batteries were fabricated on 30 μm SUS304 substrates. Charge–discharge properties of these thin-film batteries were measured at room temperature with charge-discharge currents of 50 μA and cutoff voltages of between 3.2 V and 0.5V by using a charge–discharge measuring instrument (ACD-01, Asuka). The surface area of thin film batteries was 4.2 x 4.2 cm2. Results and discussion. Figure 1 shows charge-discharge curves of Nb2O5 thin films in the voltage window 1.0-3.0 V (vs. Li/Li+) at a rate of 5 μAh/cm2 up to 10 cycles. The open circuit voltage of the cell lies at 2.46 V. The discharge capacities in the 1st, 3rd, 5th, and 10th cycles are 59.4, 56.8, 56.1, and 56.8 μAh/cm2μm, respectively; the corresponding charge capacities are 79.2, 56.1, 55.4, and 56.2 μAh/cm2μm for 1st, 3rd, 5th, and 10th cycles, respectively. After first few cycles, the coulombic efficiency reaches to 100%. Such irreversible capacity loss during first few cycles was also observed with other nanoparticle. Figure 2a shows charge-discharge cycling curves of a flexible thin-film battery based on Li2Mn2O4 thin films of 720 nm and Nb2O5 thin films of 800 nm at a charge-discharge current of 50 μA. The charge-discharge curve consists of smooth S-shape profiles at any cycle without any plateau having average voltage of about 1.7 V and the voltage may vary in broad voltage range of 3.2-0.5V with cycling. As shown in Fig. 2b, an initial irreversible capacity was observed, which is due to irreversible Li ions trapped in the negative electrode. The coulombic efficiency at the first cycle was only 26.3%, which is due to a large internal resistance of the battery when no Li ion was inserted into Nb2O5 thin films. After 20 cycles, the cycle performance of the thin-film battery showed steady cycling behaviors and the coulombic efficiency was all over 95% except for the first few cycles. The maximium discharge capacity (30.9 μAh/cm2μm) of the thin-film battery based on the negative electrode volume is about half of the negative capacity of the liquid battery (56.8 μAh/cm2μm), which may originate from Li ions partly being inserted into the negative electrode. Figure 1

Improvement of Internal Resistance of All-Solid-State Thin-Film Rechargeable Lithium Batteries

1. IntroductionRecently, all-solid-state thin-film rechargeable lithium batteries (TFBs) have expected to be used in various applications such as wireless sensor, smart device and other small devices for an auxiliary power supply. The TFBs are fabricated by forming each layers (i.e. cathode, electrolyte, anode and current collectors) mainly using physical vapor deposition process1,2). As a solid electrolyte, lithium phosphorus oxynitride (LiPON) thin film has been used commonly due to same advantages as no grain-boundary, isotropic property, less electronic conductivity and electrochemical stability. Ionic conductivity of LiPON thin film has been reported ~3.3 x 10-6 S/cm at 25 deg.C3), but it is lower compared with other solid electrolyte4). It is necessary to reduce the internal resistance of TFBs for applying to the device as described above. We improved this issue by reducing the thickness of LiPON film and reported in the previous meeting5). Internal resistance was successfully reduced. However, we had another issue that interfacial resistance between a cathode and an electrolyte was increased by planarization of a cathode surface. In this study, we investigated the mechanism of increasing of interfacial resistance and improved it with new surface modification material (LiCo0.9Al0.1O2). 2. ExperimentalLithium cobalt oxide (LCO) film as a cathode was prepared by RF and DC hybrid magnetron sputtering method on platinum film as a current collector. Ar was used as sputtering gas, and process pressure was kept at 1.6 Pa. New surface modification material, LiCo0.9Al0.1O2 (LCAO) film was prepared by RF magnetron sputtering method on LCO film. Sputtering gas and process pressure were same as LCO deposition. After deposition, LCO and LCAO were annealed at 600deg.C under atmospheric pressure by lamp heating system. Solid electrolyte (LiPON) film was prepared by RF magnetron reactive sputtering method with lithium phosphate (LPO; Li3PO4) target and N2 gas. Lithium film as an anode was prepared by vacuum evaporation method. Acrylic monomer was coated on the anode surface, covered with barrier lid, and cured by ultraviolet light for formation as an encapsulation. The fabricated TFB cells were investigated by electrical and electrochemical properties at room temperature. 3. Results and discussionFigure 1 shows the scanning electron microscopy (SEM) images of LCO films with and without LCAO film after annealing process. As result , it was confirmed that top of LCO columnar grain became sharp by coating with LCAO film. We think this result shows decomposition reaction was suppressed with LCAO film. Figure 2 shows the nyquist plot of TFB and each resistance with and without LCAO film. It was also confirmed that the resistance of 1st semicircle was not changed by LCAO film thickness and the resistance of 2nd semicircle is was decreased by it. These results show LCAO film improved interfacial resistance between a cathode and an electrolyte. Reference1) J. B. Bates, N. J. Dudney, G. R. Gruzalski, R. A. Zuhr, A. Choudhury, C. F. Luck and J. D.Robertson, J. Power Sources, 43, 103 (1993).2) T. Jimbo, P. Kim and K. Suu, Energy Procedia, 14, 1574 (2012).3) Xiaohua Yu, J. B. Bates, G. E. Jellison, Jr., and F. X. Hart, J. Electrochem. Soc., 144, 524 (1997).4) N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y.Kato, S. Hama, K. Kawamoto and A. Mitsui, Nature Materials, 10, 682 (2011).5) A. Suzuki, S. Sasaki, I. Kimura and T. Jimbo, #449, 227th ECS Meeting (2015). Figure 1

Improvement of Power Characteristics of All-Solid-State Thin-Film Rechargeable Lithium Batteries

1. Introduction Recently, all-solid-state thin-film rechargeable lithium batteries (TFBs) has expected in various applications such as wireless sensor, smart device and other small devices for an auxiliary power supply. The TFBs are fabricated by forming each layers (i.e. cathode, electrolyte, anode and current collector) using physical vapor deposition process1,2). As a solid electrolyte, lithium phosphorus oxynitride (LiPON) thin film has been used commonly due to no grain-boundary, isotropic property, less electronic conductivity and electrochemical stability. Ionic conductivity of LiPON thin film has been reported ~3.3 x 10-6 S/cm at 25 deg.C3), but it is lower compared with other solid electrolyte4). It is necessary to reduce the internal resistance of TFBs for applying to the device as described above. In order to improve this, it has to be thinner LiPON film or change the electrolyte material having higher ionic conductivity. However, there is a limited to the thickness of electrolyte film without short- circuit because the surface of cathode film is rougher with thicker cathode film5). In this study, we investigated the planarization of cathode film for thinner electrolyte film. 2. Experimental Lithium cobalt oxide (LCO) film was prepared by RF and DC hybrid power magnetron sputtering method on platinum film as current collector. Ar was used as sputtering gas, and process pressure was kept at 1.6 Pa. Furthermore, LCO was deposited with applying each bias power to the substrate for investigating the planarization. After deposition, LCO was annealed at 600 deg.C under atmospheric pressure by lamp heating system. Solid electrolyte (LiPON) film was prepared by RF magnetron reactive sputtering method with only N2gas. Lithium film as an anode was prepared by vacuum evaporation method. Acrylic monomer as a sealant was coating on the anode surface, covered with barrier lid, and cured by ultraviolet light for encapsulation. The fabricated TFB cells were investigated by electrical and electrochemical properties at room temperature. 3. Results and discussion Figure 1 shows the scanning electron microscopy (SEM) image of 3-μm-thick LCO film under different bias power condition. As the result of this, it was confirmed that surface of LCO becomes smoother with higher bias power and surface morphology changes from pyramid-like to dome-like by re-sputtering. TFB cell was fabricated with 2-μm-thick LiPON and 2-μm-thick lithium and discharge capacity was also checked. The charge method is CCCVmode (current density: 0.21 mA/cm2, cut-off: >4.2 V and <0.021 mA/cm2) and the discharge method is CC mode (current density: 0.21 mA/cm2, cut-off: <3.0 V). Figure 2 shows the discharge curve of TFB cells. It was confirmed that discharge capacity of TFB cell is higher with increasing bias power. It is thought that film density of LCO becomes high due to ion peening effect. The improvement of thinner LiPON film and the other are on evaluating. Reference 1) J. B. Bates, N. J. Dudney, G. R. Gruzalski, R. A. Zuhr, A. Choudhury, C. F. Luck and J. D. Robertson, J. Power Sources, 43, 103 (1993).2) T. Jimbo, P. Kim and K. Suu, Energy Procedia, 14, 1574 (2012).3) Xiaohua Yu, J. B. Bates, G. E. Jellison, Jr., and F. X. Hart, J. Electrochem. Soc., 144, 524 (1997).4) N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y. Kato, S. Hama, K. Kawamoto and A. Mitsui, Nature Materials, 10, 682 (2011).5) T. Jimbo, S. Sasaki, A. Suzuki, I. Kimura and K. Suu, #1235, 224th ECS Meeting (2013) Figure 1

Cu-Sn Thin Films as Anodes for Thin Film Rechargeable Lithium Batteries

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Layered Li(Ni[sub 1/4]Mn[sub 1/2]Co[sub 13])O[sub 2] as Cathode Material for All-Solid-State Thin-Film Rechargeable Lithium-Ion Batteries

Li(Ni 1/4 Mn 1/2 Co 1/3 )O 2 thin-film electrodes have been successfully fabricated by magnetron sputtering. The electrochemical behaviors of thin-film electrodes have been investigated in liquid and solid electrolytes. The reversible capacity of Li(Ni 1/4 Mn 1/2 Co 1/3 )O 2 is found to be above 30 μAh/cm 2 μm in all-solid-state thin-film batteries cycled between 5.0 and 3.0 V. The diffusion constants of Li ion are calculated to be 1.62 × 10 ―13 and 1.78 × 10 ―13 cm 2 /s for deinsertion and insertion at ambient temperature, respectively. Our results demonstrated that the Li(Ni 1/4 Mn 1/2 Co 1/3 )O 2 film electrode could be selected as one of the promising candidates for all-solid-state thin-film rechargeable lithium batteries.

Physical and electrochemical characterization of amorphous lithium lanthanum titanate solid electrolyte thin-film fabricated by e-beam evaporation

Amorphous lithium lanthanum titanate (LLTO) solid electrolyte thin-films have been fabricated by e-beam evaporation. The effect of different e-beam power on the physical properties and electrical performance of LLTO thin-film is investigated. Higher e-beam power is a key factor to obtain good quality LLTO thin-film which has higher ionic conductivity. X-ray diffraction patterns, X-ray photoelectron spectra, scanning electron microscopy and impedance spectroscopy are used to characterize their physical and electrical properties. An all-solid-state of Li/LiPON/LLTO/LiCoO2 cell using LLTO thin-film as solid electrolyte exhibits the first discharge capacity of about 50 μA h/cm2-μm and the capacity fading is about 0.5% per cycles after 100 discharge–charge cycles at discharge current of 7 μA/cm2, demonstrating the promise of e-beam evaporation deposition for the fabrication of LLTO thin-film for all-solid-state thin-film rechargeable lithium batteries.

Characterization of Composite 0.5Ag:V[sub 2]O[sub 5] Thin-Film Electrodes for Lithium-Ion Rocking Chair and All-Solid-State Batteries

A type of rocking chair Li-ion battery was reported using 0.5Ag:V 2 O 5 composite films with and without lithiation as anode and cathode materials, respectively. The discharge capacity can reach 22 μAh/μm cm 2 with low capacity fading up to 100 cycles at a current of 10 μA/cm 2 . An all-solid-state lithium battery of Li/LiPON/0.5Ag:V 2 O 5 exhibited a typical reversible capacity of 42-72 μAh/μm cm 2 and the reduction of capacity is about 1.1% every cycle. These results suggest that a composite 0.5Ag:V 2 O 5 thin-film electrode is a promising cathode material for all-solid-state thin-film rechargeable lithium batteries.

A nanocrystalline Co 3O 4 thin film electrode for Li-ion batteries

Thin films of nanocrystalline Co 3O 4 have been prepared by reactive pulsed laser deposition (PLD) method in oxygen ambient. The film electrode of Co 3O 4 has a reversible capacity of 1000 mAh/g and its capacity fading is less than 0.2% per cycle at a discharge of 3 C. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photo-electron spectroscopy (XPS) measurements demonstrated that the deposited films composed of cubic spinel Co 3O 4 with the mean size of ∼50 nm. The nano-sized structure of the Co 3O 4 plays an important role in the superior reversible capacity and good cycling performance. Our results also demonstrate the promise of pulsed laser deposition for the fabrication of nanocrystalline Co 3O 4 film for all-solid-state thin film rechargeable lithium batteries.

Nanostructured Ni 3Sn 2 thin film as anodes for thin film rechargeable lithium batteries

Thin film Ni 3Sn 2 anodes were deposited on a Cu substrate by e-beam evaporator at room temperature. The deposited films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). They were tested as anodes for thin film rechargeable lithium batteries. These film electrodes exhibited an excellent cycle performance over 500 cycles. Ni 3Sn 2 films remained without undergoing any crystallographic phase change during cycling.

Materials for all-solid-state thin-film rechargeable lithium batteries by sol-gel processing

A novel all-solid-state thin-film lithium battery has been fabricated by spin coating V2O5 and LiClO4-SiO2 thin films on a stainless steel substrate. The LiClO4-SiO2 electrolyte has been synthesized using a new sol-gel route and it has been characterized by electrochemical impedance spectroscopy. The Li+ ion conductivity of the spin-coated thin film thus measured is in the order of 10–6 S/cm, at 25 °C, which is sufficient for electrolytes in such thin-film batteries. The battery shows a typical discharge capacity of about 150 µAh/mg and satisfactory cathodic efficiency and cycle-life performance.

Reduction of Irreversibility in the First Charge of Tin Oxide Thin Film Negative Electrodes

Sputter deposited 3000 Å tin oxide thin films into which metallic lithium (6000 Å) was reacted were studied to develop a new negative electrode for thin film rechargeable lithium batteries. The crystal structure and chemical composition of the lithium reacted tin oxide films were characterized by X-ray diffraction (XRD) analysis and Auger electron spectroscopy, respectively. The charge/discharge performances of these films exhibited capacities >400 mAh/g for >75 cycles. There was no irreversible plateau near 0.8 V vs. due to reduction of to Sn and during the first charge half-cycle. XRD and scanning transmission electron microscopy results suggest that the lithium-reacted tin oxide thin film consists of metallic tin, lithium oxide, and reduced tin oxide, and the reacted thin films show reduced microcracks created by density fluctuations. © 2001 The Electrochemical Society. All rights reserved.

Effects of deposition condition on the ionic conductivity and structure of amorphous lithium phosphorus oxynitrate thin film

Thin film rechargeable lithium batteries, in forms of Li{vert_bar}Li{sup +} solid electrolyte{vert_bar}Li intercalation cathode, have been studied for their applications in electronic devices such as built-in power sources for RAM, CMOS chips and smart cards. Recently, it was reported that a new amorphous lithium electrolyte, lithium phosphorus oxynitride (LIPON), showed an ionic conductivity as high as 2.0 x 10{sup {minus}6} {Omega}{sup {minus}1} cm{sup {minus}1} at room temperature, and also excellent long term stability when in contact with lithium. In spite of the advantages of LIPON as a solid electrolyte for microbatteries, the influence of deposition parameters on the structure and ionic conductivity on the LIPON is not yet known. the objective of the present study is to examine the effect of deposition conditions on the ionic conductivity and structural change of the LIPON solid electrolyte films, and hence to elucidate the mechanism by which the incorporation of nitrogen into phosphate glass improves the Li{sup +} ionic conductivity of LIPON.

Solid state thin-film lithium battery systems

Thin-film rechargeable lithium batteries, less than 15 μm thick, are being developed as micro-power sources. Batteries with long cycle lives have been constructed with a variety of electrode materials and cell configurations onto thin ceramic, metal, and Si substrates. Improvements in the properties of several well-known cathode thin-film materials have been reported, while several novel thin-film anode materials have been introduced in recent papers. All recent thin-film batteries with moderate discharge powers and cycle lives rely on the amorphous lithium phosphorus oxynitride electrolyte, known as Lipon, deposited by rf magnetron sputtering.

Charge/discharge characteristics of $LiCoO_2$ thin film prepared by electron-beam evaporation with deposition rate and annealing temperatures

Lithium cobalt oxide cathode for thin-film rechargeable lithium batteries were fablicated by electron-beam evaporation. Annealed lithium cobalt oxide, which was deposited on to stainless steel substrate, showed well-developed (003) planes of the hexagonal structure and potential plateau at . Lithium cobalt oxide thin films had the stoichiometric Li/co ratio at high deposition rates and exhibited high discharge capacity at . As the annealing temperature increased, discharge capacity increased with maximum value at , but showed low capacity as a result of reaction with substrate above . Unuiformity of the lithium and cobalt in the depth profile gave initial capacity loss with charge/discharge performance.

High Performance Vanadium Oxide Thin Film Electrodes for Rechargeable Lithium Batteries

ABSTRACTPlasma Enhanced Chemical Vapor Deposition (PECVD) was used to prepare vanadium oxide thin films as cathodes for rechargeable lithium batteries. The reactants consisted of a high vapor pressure liquid source of vanadium (VOCl3) and hydrogen and oxygen gas. Deposition parameters such as the flow rates of H2, O2 and VOCl3, the substrate temperature and the Rf power were optimized, and high deposition rate of 11 Å/s was obtained. Vanadium oxide films with high discharge capacities of up to 408 mAh/g were prepared. The films also showed a superior cycling stability between 4 and 1.5 V at a C/0.2 rate for more than 4400 cycles. The films were amorphous up to a deposition temperature of 300°C, however, deposition on to substrates with textured surfaces facilitated the formation of crystalline films. We demonstrate that both the vanadium oxide material and the PECVD deposition method are very attractive for constructing thin-film rechargeable lithium batteries with high capacity and long-term cyclic stability.

Polymer electrolyte lithium batteries rechargeability and positive electrode degradation: An AC impedance study

AC impedance measurements of polymer electrolyte-based, symmetrical composite cathode cells were used to probe the effects of the composite cathode composition and fabrication process upon its performance when used in polymer electrolyte-based thin film rechargeable lithium batteries. The relationship between cycling performance and AC impedance measurements were used to elucidate some of the reported failure mechanisms of rechargeable lithium polymer electrolyte batteries. The rapid initial capacity decay observed within the first few cycles of the polymer electrolyte/V6O13 based composite cathode is shown to be related to the properties of the composite cathode active material, while the slower capacity decay observed during subsequent cycles, under continuous cycling regimes, appears to be related to a loss of ionic and electronic contact in the composite cathode.