Ragone-construction各种锂材料比较

Fuel Cells
EV goal
2
Li-ion
100
6 4 2
Ni-MH Lead-acid
10 h
HEV goal Capacitors
10
6 4 2
Range
1h
0.1 h
36 s
3.6 s
1 0 10 Acceleration
10
1
Specific Power (W/kg)
10
2
10
3
10
4
Voltage (V) vs.Li
1.0
• Diffusion coefficient taken as a constant with state of charge
0.8
Electrode thickness=75 mm Loading=4.8 mg/cm2
0.6
• Diffusion coefficient in solid phase and kinetics taken from literature; SEI resistance fit from experimental data (0.023 W-m2) • Material has lower power than ones used in present-day HEV batteries
Can we compare various Li-ion batteries to each other on a fair basis?
Relative Performance of Various Li-ion Chemistries
Li/LiNi1/3Co1/3Mn1/3O2(4.3 V)
• Model uses a varying diffusion coefficient (taken from literature)
Supplier: Seimi Chemical Co.
4.5 4.0
• Solved using a pseudo 2D-approach
Voltage (V) vs. Li
• Model fit to data to extract kinetic parameters (io=0.146 A/m2 at y=0.5) • Model predictions compared to data on charge and discharge, for two cell designs, and when charged to 4.3 and 4.5 V • Predictions poor at end of discharge
Lithium-metal
• Based on a macro-homogeneous approach – Microscopic details (e.g., pore structure) are averaged • Models are mechanistic in nature. Include: – Mass and charge transport in the porous electrodes – Thermodynamics and kinetics of the reaction – Solid-phase processes Diffusion and phase change (LiFePO4) or intercalation (other cathodes and graphite anode) • Electrolyte properties taken from literature and is the same for all cells • See /jsngrp/ for basic model (dualfoil)
Source: Product data sheets
• Goals developed by DOE and USABC • Plot provides a means of comparing various systems to each other • However, cell design has a significant impact on performance, hence complicating comparison • Lead-acid batteries in cars (SLI batteries) thinner than those used for traction
Graphite Anode
SEI
Discharge
Li1.0C6 Li1.0C6 Li Li+ e-
Discharge
Li1-xC6 Li
Discharge
Li0C6
Li+ e-
• SEI layer treated as an ohmic drop • Duhamel’s superposition integral used to account for the solid phase diffusion*
4
Specific Energy (Wh/kg)
10 h
2
charged to 4.5 V
EV pack goal Li/V6O13
100
8 6 4
3h
Gr/LiMn2O4
Gr/LiFePO4
1h
Gr/LiNi1/3Co1/3Mn1/3O2 (charged to 4.3 V)
2
30 min
Range
LiyMO2
discharge
LiyMO2 Li
discharge
Liy+xMO2
+
discharge
Li1.0MO2 Li Li+ e-
Li M=Ni1/3Co1/3Mn1/3 e y- Initial State-of-charge. Smaller y → Greater capacity; higher charging voltage
LiMn2O4 Spinel Cathode
Li0.45Mn2O4
discharge
Li0.45Mn2O4 Li
discharge
Li0.45+yMn2O4 Li
discharge
Li1.0Mn2O4
Li+
e-
Li+ e-
• Material is a lithium-excess spinel
• Modeled as an intercalation system • Diffusion coefficient assumed constant with SOC
A Model-based Comparison of Various Li-ion Chemistries
Relative Performance of Various Electrochemical Energy-Storage Devices
1000
6 4
IC Engine
100 h
Specific Energy (Wh/kg)
Source: US Patent application No. 2004/0191617A1
• Model incorporates glass layer by accounting for an additional ohmic drop • Layer thought to help prevent dendrite growth • Information from US Patent application No. 2004/0191617A1 by the Polyplus Battery Co. • Thickness of layer=50 mm • Conductivity=8× 10-4 S/cm • Model fit to impedance data to extract exchange current density • No attempt was made to fit the complete impedance curve
4.4
Thickness=35 mm Loading=3.3 mg/cm2
Voltage (V) vs. Li
4.4 4.2
Thickness=70 mm Loading=10.26 mg/cm2
Voltage (V) vs. Li
4.2 4.0
0.84
0.05 mA/cm2
0.28 0.56 1.41 2.82
Supplier: Toda
• Model fit to data to extract the diffusion coefficient (2.5× 10-15 m2/s) and exchange current density (0.157 A/m2 at 50% SOC) • Parameters used to predict other cell designs
Procedure for Generating Ragone Plot
Develop model for each chemistry • 2 anodes and 4 cathodes modeled to-date Perform thermodynamic and rate experiments • Half-cell experiments with Li-reference and counter • Performed for 1 anode and 3 cathodes • Typically performed with varying electrode design Compare model to data to extract unknown parameters • Extract with one cell; predict other cells Combine half-cell models to develop a full-cell model • Ensure common basis for various cells • Same first-cycle loss and excess anode capacity • Same mass of current collectors e.t.c Use models to understand limitations