Lithium-ion battery

This example file calculates the cell voltage of a lithium-ion battery at given temperature, pressure, current, and range of state of charge (SOC).

The thermodynamics are based on a graphite anode and a LiCoO2 cathode, modeled using the BinarySolutionTabulatedThermo class. Further required cell parameters are the electrolyte ionic resistance, the stoichiometry ranges of the active materials (electrode balancing), and the surface area of the active materials. These values are stored in the input file lithium_ion_battery.yaml.

The functionality of this example is presented in greater detail in the reference (which also describes the derivation of the BinarySolutionTabulatedThermo class).

Reference:

M. Mayur, S. C. DeCaluwe, B. L. Kee, W. G. Bessler, “Modeling and simulation of the thermodynamics of lithium-ion battery intercalation materials in the open-source software Cantera,” Electrochim. Acta 323, 134797 (2019), https://doi.org/10.1016/j.electacta.2019.134797

Tags: Matlab surface chemistry kinetics electrochemistry battery plotting

Initialization

clear all
close all

tic
help lithium_ion_battery

Operation parameters

SOC = 0:0.02:1; % [-] Input state of charge (0...1) (can be a vector)
I_app = -1; % [A] Externally-applied current, negative for discharge
T = 293; % [K] Temperature
P = OneAtm; % [Pa] Pressure

Cell properties

inputFile = 'lithium_ion_battery.yaml'; % Cantera input file name
R_elyt = 0.0384; % [Ohm] Electrolyte resistance
S_ca = 1.1167; % [m^2] Cathode total active material surface area
S_an = 0.7824; % [m^2] Anode total active material surface area

Electrode balancing: The “balancing” of the electrodes relates the chemical composition (lithium mole fraction in the active materials) to the macroscopic cell-level state of charge.

X_Li_an_0 = 0.01; % [-] anode Li mole fraction at SOC = 0 %
X_Li_an_1 = 0.75; % [-] anode Li mole fraction at SOC = 100 %
X_Li_ca_0 = 0.99; % [-] cathode Li mole fraction at SOC = 0 %
X_Li_ca_1 = 0.49; % [-] cathode Li mole fraction at SOC = 100 %

Calculations

% Calculate mole fractions from SOC
X_Li_an = (X_Li_an_1 - X_Li_an_0) * SOC + X_Li_an_0; % anode balancing
X_Li_ca = (X_Li_ca_0 - X_Li_ca_1) * (1 - SOC) + X_Li_ca_1; % cathode balancing

% Import all Cantera phases
anode = Solution(inputFile, 'anode');
cathode = Solution(inputFile, 'cathode');
elde = Solution(inputFile, 'electron');
elyt = Solution(inputFile, 'electrolyte');
anode_interface = Interface(inputFile, 'edge_anode_electrolyte', anode, elde, elyt);
cathode_interface = Interface(inputFile, 'edge_cathode_electrolyte', cathode, elde, elyt);

% Set the temperatures and pressures of all phases
anode.TP = {T, P};
cathode.TP = {T, P};
elde.TP = {T, P};
elyt.TP = {T, P};
anode_interface.TP = {T, P};
cathode_interface.TP = {T, P};

% Calculate cell voltage, separately for each entry of the input vectors
V_cell = zeros(length(SOC), 1);
phi_l_an = 0;
phi_s_ca = 0;

for i = 1:length(SOC)
    % Set anode electrode potential to 0
    phi_s_an = 0;

    % Calculate anode electrolyte potential
    phi_l_an = fzero(@(E) anode_curr(phi_s_an, E, X_Li_an(i), anode, elde, ...
                                    elyt, anode_interface, S_an) - I_app, phi_l_an);

    % Calculate cathode electrolyte potential
    phi_l_ca = phi_l_an + I_app * R_elyt;

    % Calculate cathode electrode potential
    phi_s_ca = fzero(@(E) cathode_curr(E, phi_l_ca, X_Li_ca(i), ...
                                      cathode, elde, elyt, cathode_interface, S_ca) ...
                                      - I_app, phi_s_ca);

    % Calculate cell voltage
    V_cell(i) = phi_s_ca - phi_s_an;
end

% Let's plot the cell voltage, as a function of the state of charge:
figure(1);
plot(SOC * 100, V_cell, 'linewidth', 2.5)
ylim([2.5, 4.3])
xlabel('State of charge / %')
ylabel('Cell voltage / V')
set(gca, 'fontsize', 14)

toc

Helper functions

% This function returns the Cantera calculated anode current (in A)
function anCurr = anode_curr(phi_s, phi_l, X_Li_an, anode, elde, elyt, ...
                            anode_interface, S_an)
    % Set the active material mole fraction
    anode.X = ['Li[anode]:' num2str(X_Li_an) ', V[anode]:' num2str(1 - X_Li_an)];

    % Set the electrode and electrolyte potential
    elde.electricPotential = phi_s;
    elyt.electricPotential = phi_l;

    % Get the net reaction rate at the anode-side interface
    % Reaction according to cti file: Li+[elyt] + V[anode] + electron <=> Li[anode]
    r = anode_interface.netRatesOfProgress; % [kmol/m2/s]

    % Calculate the current. Should be negative for cell discharge.
    anCurr = r * FaradayConstant * S_an; %
end

% This function returns the Cantera calculated cathode current (in A)
function caCurr = cathode_curr(phi_s, phi_l, X_Li_ca, cathode, elde, elyt, cathode_interface, S_ca)
    % Set the active material mole fractions
    cathode.X = ['Li[cathode]:' num2str(X_Li_ca) ', V[cathode]:' num2str(1 - X_Li_ca)];

    % Set the electrode and electrolyte potential
    elde.electricPotential = phi_s;
    elyt.electricPotential = phi_l;

    % Get the net reaction rate at the cathode-side interface
    % Reaction according to cti file: Li+[elyt] + V[cathode] + electron <=> Li[cathode]
    r = cathode_interface.netRatesOfProgress; % [kmol/m2/s]

    % Calculate the current. Should be negative for cell discharge.
    caCurr = r * FaradayConstant * S_ca * (-1); %
end