Battery Capacity Fade Research Articles

A graphite functional layer covering the surface of LiMn2O4 electrode to improve its electrochemical performance

Here, we first report the introduction of sputtering a graphite layer covering the surface of the as-fabricated LiMn2O4 cathode to form a protective layer as a solution to solve the rapid capacity fading of LiMn2O4-based lithium ion battery at elevated temperature. Compared with the rapid capacity fading of the bare LiMn2O4 cathode (LMO), the graphite layer modified cathode (G-LMO) possesses excellent cyclic performance at 55°C. It maintains 92% of initial discharge capacity even after 500cycles at 1C. TEM images show that the surface of the bare LiMn2O4 particles in LMO sample is damaged while G-LMO withstands Mn leaching induced by HF corrosion under the protection of graphite layer.

Research on Buoy Power Management Technology Based on the Battery Switch Theory

The cycle performance and the capacity fading model of 18650 Li-ion batteries and the possibility of dual-battery switching technology applied in marine buoys were studied. The recycling capacity fading data of 18650 li-ion batteries were gained and the data were fit by Matlab cttool toolbox. A fitting curve more in line with the scatters was gained. The number of cycles was calculated when the battery capacity remaining 80%. Then the normal working time and the working time using battery switching theory of a buoy were calculated under that specific number of cycles. The results show that the 18650 li-ion battery capacity fading model adheres more to the power function model than linear function model. Its correlation coefficient reaches 0.9811 and it shows a high fitting degree. The longevity of the battery pack using battery switching technology is 28.79% longer than the traditional single battery pack.

Analysis of Fuel Economy and Battery Life depending on the Types of HEV using Dynamic Programming

Increasing demands of eco-friendly vehicles, various types of hybrid electric vehicle (HEV) have been researched and released. Recently, some research has interest in not only the efficiency of the vehicle but also the durability of battery because the life of battery has influence on the cost of maintenance, stability and performance of the vehicle. In this study, backward simulation based on dynamic programming depending on the type of HEV which is consists of engine and battery or engine, battery and ultra-capacitor was conducted. The developed backward simulation algorithm can calculate the optimal fuel economy according to the driving cycle and other vehicle and components conditions. For the analysis of battery life, a battery capacity fade model was applied to the result of backward simulation. Battery life was estimated with an assumption that the vehicle drives repeatedly to follow the result of backward simulation derived to find the optimal fuel economy. From the simulation results, it is shown that HEV with ultra-capacitor has better fuel economy though it is almost similar with HEV without ultra-capacitor. However, the battery life of HEV with ultra-capacitor was estimated better because of the difference of battery power usage. Consequently, applying the ultra-capacitor to the typical parallel HEV has no large advantage in terms of fuel economy but has significant benefit in terms of battery life.

On-board state of health monitoring of lithium-ion batteries using incremental capacity analysis with support vector regression

Battery state of health (SOH) monitoring has become a crucial challenge in hybrid electric vehicles (HEVs) and all electric vehicles (EVs) research, as SOH significantly affects the overall vehicle performance and life cycle. In this paper, we focus on the identification of Li-ion battery capacity fading, as the loss of capacity and therefore the driving range is a primary concern for EV and plug-in HEV (PHEV). While most studies on battery capacity fading are based on laboratory measurement such as open circuit voltage (OCV) curve, few publications have focused on capacity loss monitoring during on-board operations. We propose a battery SOH monitoring scheme based on partially charging data. Through analysis of battery aging cycle data, a robust signature associated with battery aging is identified through incremental capacity analysis (ICA). Several algorithms to extract this signature are developed and evaluated for on-board SOH monitoring. The use of support vector regression (SVR) is shown to provide the most consistent identification results with moderate computational load. For battery cells tested, we show that the SVR model built upon the data from one single cell is able to predict the capacity fading of 7 other cells within 1% error bound.

On the stress characteristics of graphite anode in commercial pouch lithium-ion battery

The stress of graphite anode in commercial pouch lithium-ion battery is characterized ex-situ by using micro-Raman mapping technique at 2 μm lateral resolution. The results show that the stress in graphite anode is always compressive and its distribution is inhomogeneous both in the manufacturing process and in cycling process. The stress mainly generates and accumulates in the early stage of cycling process, which causes not only big anode thickness swelling but also graphite particles cracking or even degrading. The deterioration of electrical contact of graphite particles from current collector caused by anode volume expansion and formation of solid electrolyte interface (SEI) in fresh surface of cracked graphite particle is responsible for the faster capacity fading of pouch battery in this early stage.

Tris(trimethylsilyl) borate as an electrolyte additive to improve the cyclability of LiMn2O4 cathode for lithium-ion battery

In order to overcome severe capacity fading of LiMn2O4 cathode lithium-ion battery, tris(trimethylsilyl) borate (TMSB) is used as an electrolyte additive. With 0.5 wt% TMSB addition into the electrolyte (EC/DMC with 1 M LiPF6), the capacity retention is significantly improved at both room temperature and 55 °C. The effects of the TMSB on the LiMn2O4 electrode are investigated via a combination of cyclability, capacity retention of high temperature storage, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Based on these results, it is suggested that the improved cyclability of the cells containing the TMSB additive is mainly originated from the participation in the formation of solid electrolyte interface (SEI) on the surface of electrode, the dissolution of LiF out of the SEI and the enhancement of cyclability of Li anode.

Mn Substitution with Co in LiCo<sub>(1-X)</sub>Mn<sub>x</sub>O<sub>2</sub> Cathode Materials and their Charge-Discharge Characteristic

LiCoO2 has been used as a cathode material in commercial Li-ion batteries. This is due to advantageous properties of the LiCoO2 like ease of preparation and good electrochemical characteristics. However, the high cost and toxicity of Co has limited its use. Therefore, the substitution of Co in the LiCoO2 by non-toxic and inexpensive transition metallic element is needed. Mn is considered as one of the promising candidates to fulfill all the requirements. Partial substitution of Co by Mn has also been considered to enhance the stability of LiCoO2 lattice, minimize capacity fading and increase cycle life of the Li-ion battery. LiCo(1-x)MnxO2 (x= 0.1, 0.2, 0.3) were prepared by using a self-propagating combustion (SPC) method. X-ray diffraction (XRD) of the samples were carried out for phase analysis and showed that all the materials are pure. The samples were also analyzed using the Field Emission Scanning Electron Microscope (FESEM) to study its morphology and particle size. Finally cathodes were fabricated and assembled in an inert gas-filled fabrication box. Discharge profiles of the materials were carried out in the voltage range of 4.3 V – 3 V. The materials obtained were phase pure and improved the capacity fading of the materials compared to LiCoO2. All of the materials exhibited less than 10% capacity loss even though it does not improve the first cycle discharge capacity.

Cycling effects on surface morphology, nanomechanical and interfacial reliability of LiMn2O4 cathode in thin film lithium ion batteries

In this study, the effects of Li+ intercalation/deintercalation processes on surface morphology, nanomechanical and interfacial properties of sputtered LiMn2O4 cathode film are studied using various techniques, including ex situ field emission scanning electron microscope (FESEM), atomic force microscope (AFM), nanoindentation tests combining with focused ion beam (FIB) sectioning. The results reveal that the spinel LiMn2O4 cathode film shows good cycling performance and morphology stability, accompanying with a slight increase of surface roughness mainly due to the agglomeration of nano-grains caused by phase transformations. The cathode film mechanically fails due to the stress induced by the lattice parameter change upon Li+ intercalation/deintercalation and lattice mismatch related to inhomogeneous phase transformation as well as the Jahn–Teller distortion in the 4V region. The induced stress in the film causes the fragmentation of grains and the initiation/propagation of micro-cracks, leading to the mechanical degradation. The non-uniformity, micro-cracks and nanomechanical degradation have harmful effects on the electrical contact of LiMn2O4 cathode film, resulting in the capacity fading of the lithium ion battery.

Insights into Li-S Battery Cathode Capacity Fading Mechanisms: Irreversible Oxidation of Active Mass during Cycling

The solid components deposited in sulfur cathode during cycling for Li-S battery is studied in this work. ROLi, HCO2Li, LixSOy and Li2S (or Li2S2) are proved to be the main components by the methods of Fourier transform infrared (FTIR), Raman spectra and X-ray photoelectron spectroscopy (XPS). ROLi and HCO2Li are solvent degradation products existed in electrolyte. The reversibility of Li2S and Li2S2 are not serious as in previous reports. ROLi, HCO2Li and LixSOy co-deposited with Li2S or Li2S2 in discharge process lead to the cathodes performance deterioration. Lithium salts such as LiNO3 and LiTFSI can oxidize sulfur compounds to higher oxidation states, and LixSOy species increased with cycling indicates the active mass irreversible oxidation that may be another important reason for the capacity fading of Li-S battery.

The role of mechanically induced separator creep in lithium-ion battery capacity fade

Lithium-ion batteries are well-known to be plagued by a gradual loss of capacity and power which occur regardless of use and can be limiting factors in the development of emerging energy technologies. Here we show that separator deformation in response to mechanical stimuli that arise under normal operation and storage conditions, such as external stresses on the battery stack or electrode expansion associated with lithium insertion/deinsertion, leads to increased internal resistance and significant capacity fade. We find this mechanically induced capacity fade to be a result of viscoelastic creep in the electrochemically inactive separator which reduces ion transport via a pore closure mechanism. By applying compressive stress on the battery structure we are able to accelerate aging studies and identify this unexpected, but important and fundamental link between mechanical properties and electrochemical performance. Furthermore, by making simple modifications to the electrode structure or separator properties, these effects can be mitigated, providing a pathway for improved battery performance.

Lithium (fluorosulfonyl)(nonafluorobutanesulfonyl)imide (LiFNFSI) as conducting salt to improve the high-temperature resilience of lithium-ion cells

A novel lithium salt, lithium (fluorosulfonyl)(nonafluorobutanesulfonyl)imide (LiFNFSI), is investigated as a conducting salt to improve the high-temperature resilience of lithium-ion cells. It shows better thermal stability than LiPF 6. The electrolyte having 1.0 M LiFNFSI in a mixture of ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (3:7, v/v) shows high conductivity comparable to LiClO 4, good electrochemical stability, and does not corrode aluminum. At both room temperature (25 °C) and elevated temperature (60 °C), the graphite/LiCoO 2 cells with LiFNFSI exhibit better cycling performances than those with LiPF 6. Particularly, at 60 °C, the capacity fading rate of the LiFNFSI-based cell without any additive is 37% after 100 cycles, while the cell with LiPF 6 fails rapidly. These outstanding properties of LiFNFSI make it an attractive candidate to overcome the rapid capacity fading of lithium-ion batteries at elevated temperatures.

Tris(pentafluorophenyl)borane as an Electrolyte Additive to Improve the High Temperature Cycling Performance of LiFePO4 Cathode

The capacity fading of batteries using ethylene carbonate/dimethyl carbonate electrolyte with tris(pentafluorophenyl)borane (TPFPB) additive at is investigated by cyclic voltammetry, cyclability, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The cyclability results show that the cell with the TPFPB additive electrolytes exhibits high discharge capacity and good cycling performance at . The electrode cycled at without the TPFPB additive shows a significant increase in charge-transfer resistance by EIS analysis. The TPFPB additive in the electrolyte reduces the difference in the charge-transfer resistance before and after 100 cycles at elevated temperatures. SEM results show that after 100 cycles at in an electrolyte without TPFPB additive, the electrode forms a visible material on the electrode surface. The observed material is presumably related with capacity fading in the cell. The results indicate that TPFPB in the electrolyte prevents the formation of the observed material on the electrode, reduces charge-transfer resistance, and enhances cycling performance of the cells at .

Changes of LiCoO[sub 2] Cathode Material for Lithium-Ion Battery during Long Cycling

Changes of the cathode material LiCoO 2 of our homemade lithium-ion batteries with good uniformity, high capacity, and good cycling were investigated after 500, 1060, and 1600 cycles. The results show clearly that the cathode partially contributes to capacity fading of lithium-ion batteries due to two factors: (i) reactions between the electrolytes and LiCoO 2 , which produce a continuously growing surface layer on the cathode, leading to the increase of the charge transfer resistance, and (ii) the fading of LiCoO 2 structure. These results provide valuable clues to extend the cycling life for lithium-ion batteries.

A study on capacity fading of lithium-ion battery with manganese spinel positive electrode during cycling

The capacity fading mechanism of lithium-ion cell was studied by disassembling the charge–discharged cells and analyzing their electrodes using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. Cu ion dissolved from current collector of anode and Mn ion dissolved from LiMn 2O 4 spinel (cathode) were all existing in solid electrolyte interface (SEI) layer on carbon anode as Cu 2O and MnO or MnO 2, respectively. These depositions of Cu and Mn oxides did not uniformly deposited on the anode side, and most of them were detected on the carbon surface nearby to the separator side. The SEI layer is hard and about 0.3 μm in thickness. Furthermore, the cycling performance of the cells can be improved by adding 1,2,3-benzotrazole (a corrosion inhibitor of Cu) before assembling the cell, it then coordinates strongly with Cu ions into the electrolyte. From the results, it is obvious that the existing of Cu oxide as well as Mn oxide in the SEI layer, which blocks the normal intercalation of the lithium ions, is one of the factors for the capacity fading of the cells.

Electrochemical Investigations on Capacity Fading of Advanced Lithium-Ion Batteries after Storing at Elevated Temperature

Capacity fading of advanced lithium-ion batteries after elevated temperature storage was investigated by three-electrode measurements. Capacity fading of a battery increases by increasing the state-of-charge (SOC) during storage, especially at elevated temperatures. The reversible capacity of a battery at decreases from (79.3% capacity retention) after . At room temperature, a battery SOC influences the capacity fading only slightly; after of storage, the reversible capacity decreases from (98.2% capacity retention). Individual effects by the anode, cathode, and electrolyte on capacity fading are analyzed with three-electrode electrochemical ac impedance. The major contribution, from X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectroscopy results, comes from cathode degradation as a result of cobalt dissolution at the surface layer. A minor contribution comes from the continuous reactions between lithiated mesocarbon microbead (MCMB) electrode and electrolyte components, which in turn thicken the SEI film and consume available lithium ions. From X-ray diffraction and XPS results, high-temperature storage influences only the surface properties of MCMB and electrodes; bulk properties remain unchanged.

DTI APPROVES BRAEMAR FIELD DEVELOPMENT PLAN

Battery Asset Management problem determines the minimum cost replacement schedules for each individual asset in a group of battery assets that operate in parallel. Battery cycle life varies under different operating conditions including temperature, depth of discharge (DOD), charge rate, etc., and a battery deteriorates due to usage, which cannot be handled by current asset management models. This paper presents a new battery asset management methodology where battery cycle life prognosis is integrated with parallel asset management to reduce lifecycle cost of the Battery Energy Storage Systems (BESS). For the battery failure time prognosis, a nonlinear physics-based battery capacity fade model is developed and incorporated in parallel asset management model to update battery capacity over time. Experiment results have shown that the developed battery asset management methodology can be conveniently used to facilitate BESS asset management decision making thereby decreasing asset lifecycle costs.

Electrochemical analysis for cycle performance and capacity fading of a lithium-ion battery cycled at elevated temperature

Laboratory-size LiNi 0.8Co 0.15Al 0.05O 2/graphite lithium-ion pouch cells were cycled over 100% DOD at room temperature and 60 °C in order to investigate high-temperature degradation mechanisms of this important technology. Capacity fade for the cell was correlated with that for the individual components, using electrochemical analysis of the electrodes and other diagnostic techniques. The high-temperature cell lost 65% of its initial capacity after 140 cycles at 60 °C compared to only a 4% loss for the cell cycled at room temperature. Cell ohmic impedance increased significantly with a elevated temperature cycling, resulting in some of loss of capacity at the C/2 rate. However, as determined with slow rate testing of the individual electrodes, the anode retained most of its original capacity, while the cathode lost 65%, even when cycled with a fresh source of lithium. Diagnostic evaluation of cell components including X-ray diffraction (XRD), Raman, CSAFM and suggest capacity loss occurs primarily due to a rise in the impedance of the cathode, especially at the end-of-charge. The impedance rise may be caused in part by a loss of the conductive carbon at the surface of the cathode and/or by an organic film on the surface of the cathode that becomes non-ionically conductive at low lithium content.

System for 20-Min Recharging of Sealed Nickel-Cadmium Batteries

A 15–20 min recharging system for sealed cylindrical flashlight-type nickel-cadmium batteries is now available for electronic newsgathering and other applications. This ReFLEX-20 charger can recharge various sizes of battery packs—sub C, D and larger and offers the advantages of greatly reduced recharging time, negligible battery capacity fading, and up to 10 times longer battery cycle life. The principle of “ReFLEX charging” is to alternate high-energy charging periods with automatically varying lower-energy discharge pulses that in effect act as “burps.” The ReFLEX-20 system, which also includes specially manufactured and matched batteries, complements the larger ReFLEX charger which has been used for some years to recharge aircraft sintered and vented nickel-cadmium batteries. Five significant problems that are encountered with sealed nickel-cadmium batteries and conventional chargers are overcome with the ReFLEX-20 system.

Standardization of aircraft materials and parts: Anon. ( Journal Of the Society Of Chemical Industry, vol. xxxviii, No. 8, p. 144, April 30, 1919)

Lithium-sulfur batteries have been highly praised for energy storage on account of their high theoretical energy density. Beside the dissolution of lithium polysulfides, volume expansion during lithiation and insulation nature of sulfur, which lead to low sulfur utilization, the irreversible phase transformation of the final discharge product Li2S is considered as one predominant reason for capacity fading of lithium-sulfur batteries. The effective activation of Li2S is the key to improve the cycling stability. Herein, we develop a cost-effective method to synthesize N-doped nanoflakes with tunable nitrogen structures and controllable concentrations. Activation experiments confirm that N-doped carbon can reduce the activation energy to accelerate the Li2S conversion for the first time. The pyridinic N doped carbon exhibits not only the strongest capture ability of the lithium polysulfides but also the lowest dissociated energy of Li2S. Moreover, theoretical and experimental evidence prove that the activity site is electron-withdrawing pyridinic N. The cathodes based on pyridinic N doped carbon display higher capacity and better cycling stability.