电化学阻抗测量锂电池老化程度
Electrochemical Impedance Spectroscopy Testing on the Advanced Technology Development
Program Lithium-Ion Cells
Jon P. Christophern, David F. Glenn, Chester G.
Motloch, Randy B. Wright, Chinh D. Ho
Transportation Technologies and Infrastructure Department Idaho National Engineering and Environmental Laboratory描写十月
Idaho Falls, ID
Vincent S. Battaglia
DOE Technical Contact Argonne National Laboratory
Washington, DC
原来我是第三者
Abstract—The U.S. DOE Advanced Technology Development (ATD) Program is investigating Electrochemical Impedance Spectroscopy (EIS) as a new measure of cell degradation. As part of the program, the Idaho National Engineering and Environmental Laboratory (INEEL) is aging 18650-size cells using cycle-life tests developed under the Partnership for a New Generation of Vehicles, which has been superceded by FreedomCAR in January 2002. At beginning of life and every four weeks thereafter, cycle-life testing is interrupted for reference performance tests (RPT) to asss capacity and power fade rates. The
EIS impedance is measured at 60% state-of-charge over a range of frequencies at each RPT. The resulting Nyquist plots show that the two mi-circles, reprenting the anode and cathode impedance growth, are poorly resolved due to the influence of the high frequency capacitive tail and the low-frequency Warburg impedance. However, impedance growth is clearly visible at the trough frequency of the cond mi-circle. The magnitude at this frequency is comparable to the standard measure of cell degradation, which is bad on the percent-fade in power as a function of test time while delivering 300 Wh. The percent growth in EIS magnitude at the trough frequency highly correlates with the power fade. This suggests that the EIS test is a uful alternate measure of cell degradation.英语请假条格式
Keywords—Electrochemical Impedance Spectroscopy; trough frequency; Hybrid Pul Power Chararacterization test; power fade; Advanced Technology Development
Cooperative Automotive Rearch). Its emphasis will be the development of fuel cell-powered vehicles. “The long-term results of this cooperative effort will be cars and trucks that are more efficient, cheaper to operate, pollution-free, and com petitive in the showroom.”
俩小儿辩日It is believed that advanced high-power batteries will continue to be a critical component in this new program.]
II. CELL CHEMISTRY
Advanced Technology Development testing of the cond generation of cells (referred to as Gen 2 cells) is now underway. The 18650-size Gen 2 cells consist of a baline cell chemistry and one variant chemistry (referred to as Variant C). The Baline cells were manufactured to the following specifications, as developed by Argonne National Laboratory [2]: ?
Positive Electrode
? 84 wt% LiNi0.8Co0.15Al0.05O2 ? 4 wt% carbon black ? 4 wt% SFG-6
玫瑰花手工? 8 wt% PVDF binder ?
外汇倾销Negative Electrode ? 92 wt% MAG-10 ? 8 wt% PVDF binder ? ?
Electrolyte
? 1.2 M LiPF6 in EC/EMC (3:7 wt%) Separator制冷英文
? 25 μm thick PE Celgard
The Variant C cell chemistry differs from the baline chemistry by an increa to the aluminum dopant from 5% to 10% and a decrea to the cobalt from 15% to 10% in the cathode (i.e., LiNi0.8Co0.1Al0.1O2). This change resulted in a 20% drop in rated capacity (0.8 Ah) at beginning of life (BOL) compared to the Baline cell rated capacity of 1.0 Ah. III. CELL TESTING
The Idaho National Engineering and Environmental Laboratory (INEEL) is cycle-life testing the Gen 2 cells in two
I. INTRODUCTION
The U.S. Department of Energy (DOE) initiated the Advanced Technology Development (ATD) Program in 1998 to address the outstanding barriers that limit the commercialization of high-power lithium-ion batteries, specifically for hybrid electric vehicle applications. As part of the program, 18650-size cells are aged using calendar- and cycle-life tests developed under the Partnership for a New Generation of Vehicles (PNGV) Power Assist goals. Reference [1] provides additional information about the ATD Program. [Note: In January 2002 at the Detroit Auto Show, Energy Secretary Spencer Abraham announced that PNGV would be superceded by the formation of a new program between the U.S. Government and the U.S. Council for Automotive Rearch, dubbed FreedomCAR (Freedom
0-7803-7467-3/02/$17.00 ?2002 IEEE.1851
temperature groups (fifteen Baline cells at 25°C and fifteen Baline and Variant C cells each at 45°C), as described in the cell-specific test plan [3]. Cycle-life testing is performed using the PNGV 25-Wh Power Assist profile defined in the PNGV Battery Test Manual, Revision 3 [4]. It consists of a constant power discharge and regen pul with intersperd rest periods centered around 60% state-of-charge (SOC). The cumulative length of a single profile is 72 conds and constitutes one cycle. This cycle is repeated continuously during life testing.
At BOL and every four weeks (i.e., 33,600 cycle-life profiles) thereafter, cycle-life testing is interrupted for reference performance testing (RPT) which are ud to quantify capacity and power fade rates. The RPTs consist of a C1/1 static capacity test, a low-current hybrid pul power characterization (L-HPPC) test, a C1/25 static capacity test, and an Electrochemical Impedance Spectroscopy (EIS) test. All RPT’s are performed at 25°C. To minimize temperature fluctuations, the cells remain in environmental chambers during testing activities.
The C1/1 static capacity test consists of a complete discharge at a
C1 rate (i.e., 1.0 A for the Baline cells and 0.8 A for the Variant C cells) to the minimum voltage from a fully charged cell. The C1/25 capacity test consists of a full discharge and charge at one twenty-fifth of the
盐酸林可霉素
C1/1 rate (i.e., 40 mA for the Baline cells and 32 mA for the Variant C cells). The tests are ud to track the capacity fade rates as a function of time. The L-HPPC and EIS tests are ud to track power fade rates as a function of time. The tests are discusd in detail below.
The Gen 2 end-of-test (EOT) criteria are specified in [3]. The INEEL cycle-life cells are organized in three groups of fifteen, as described above. One cell from each group was nt to a diagnostic lab fo
r evaluation after the BOL RPT was completed. Following the 4-week RPT, another two cells were removed from test and nt to diagnostic labs. The EOT criteria for the remaining 12 cells are bad on equal power
