Redefine LLI

LLI given by (Inventory[fresh] - Inventory[aged])/Inventory[fresh]

pyprobe/methods/ocv_fitting/DMA.py

@@ -18,14 +18,14 @@ def __init__(self, input_data: List[Result]) -> None:
         self.cell_capacity = self.variable("Cell Capacity")
         self.pe_capacity = self.variable("Cathode Capacity")
         self.ne_capacity = self.variable("Anode Capacity")
-        self.offset = self.variable("Stoichiometry Offset")
+        self.li_inventory = self.variable("Li Inventory")
         self.define_outputs(["SOH", "LAM_pe", "LAM_ne", "LLI"])
         self.assign_outputs(
             self.calculate_dma_parameters(
                 self.cell_capacity,
                 self.pe_capacity,
                 self.ne_capacity,
-                self.offset,
+                self.li_inventory,
             )
         )
 
@@ -35,7 +35,7 @@ def calculate_dma_parameters(
         cell_capacity: NDArray[np.float64],
         pe_capacity: NDArray[np.float64],
         ne_capacity: NDArray[np.float64],
-        offset: NDArray[np.float64],
+        li_inventory: NDArray[np.float64],
     ) -> Tuple[
         NDArray[np.float64],
         NDArray[np.float64],
@@ -49,13 +49,13 @@ def calculate_dma_parameters(
             ne_stoich_limits (NDArray[np.float64]): The anode stoichiometry limits.
             pe_capacity (NDArray[np.float64]): The cathode capacity.
             ne_capacity (NDArray[np.float64]): The anode capacity.
-            offset (NDArray[np.float64]): The stoichiometry offset.
+            li_inventory (NDArray[np.float64]): The lithium inventory.
 
         Returns:
             Tuple[float, float, float, float]: The SOH, LAM_pe, LAM_ne, and LLI.
         """
         SOH = cell_capacity / cell_capacity[0]
         LAM_pe = 1 - pe_capacity / pe_capacity[0]
         LAM_ne = 1 - ne_capacity / ne_capacity[0]
-        LLI = (pe_capacity[0] - pe_capacity - (offset[0] - offset)) / cell_capacity[0]
+        LLI = 1 - li_inventory / li_inventory[0]
         return SOH, LAM_pe, LAM_ne, LLI

pyprobe/methods/ocv_fitting/Simple_OCV_fit.py

@@ -38,7 +38,7 @@ def __init__(self, rawdata: RawData, parameters: Dict[str, Any]):
                 "Cell Capacity",
                 "Cathode Capacity",
                 "Anode Capacity",
-                "Stoichiometry Offset",
+                "Li Inventory",
             ]
         )
         self.assign_outputs(
@@ -93,7 +93,7 @@ def fit_ocv(
                 - NDArray[np.float64]: The cell capacity.
                 - NDArray[np.float64]: The cathode capacity.
                 - NDArray[np.float64]: The anode capacity.
-                - NDArray[np.float64]: The stoichiometry offset.
+                - NDArray[np.float64]: The lithium inventory.
         """
         cell_capacity = np.ptp(capacity)
         SOC = capacity / cell_capacity
@@ -121,7 +121,7 @@ def objective_func(
         x_ne_lo_out = x_out[0][2]
         x_ne_hi_out = x_out[0][3]
 
-        pe_capacity, ne_capacity, stoich_offset = cls.calc_electrode_capacities(
+        pe_capacity, ne_capacity, li_inventory = cls.calc_electrode_capacities(
             x_pe_lo_out, x_pe_hi_out, x_ne_lo_out, x_ne_hi_out, cell_capacity
         )
         return (
@@ -132,7 +132,7 @@ def objective_func(
             np.array([cell_capacity]),
             np.array([pe_capacity]),
             np.array([ne_capacity]),
-            np.array([stoich_offset]),
+            np.array([li_inventory]),
         )
 
     @staticmethod
@@ -155,13 +155,12 @@ def calc_electrode_capacities(
             Tuple[float, float, float]:
                 - NDArray: The cathode capacity.
                 - NDArray: The anode capacity.
-                - NDArray: The stoichiometry offset.
+                - NDArray: The lithium inventory.
         """
-        pe_capacity = cell_capacity / (x_pe_hi - x_pe_lo)
+        pe_capacity = cell_capacity / (x_pe_lo - x_pe_hi)
         ne_capacity = cell_capacity / (x_ne_hi - x_ne_lo)
-        stoich_offset = ((1 - x_pe_hi) * pe_capacity) - (x_pe_lo * ne_capacity)
-
-        return pe_capacity, ne_capacity, stoich_offset
+        li_inventory = (pe_capacity * x_pe_lo) + (ne_capacity * x_ne_lo)
+        return pe_capacity, ne_capacity, li_inventory
 
     @staticmethod
     def calc_full_cell_OCV(

tests/methods/ocv_fitting/test_DMA.py

@@ -36,28 +36,28 @@ def eol_pe_limits_fixture():
 def bol_capacity_fixture(bol_ne_limits_fixture, bol_pe_limits_fixture):
     """Return the cell and electrode capacities."""
     cell_capacity = 5
-    pe_capacity, ne_capacity, stoich_offset = Simple_OCV_fit.calc_electrode_capacities(
+    pe_capacity, ne_capacity, li_inventory = Simple_OCV_fit.calc_electrode_capacities(
         bol_pe_limits_fixture[0],
         bol_pe_limits_fixture[1],
         bol_ne_limits_fixture[0],
         bol_ne_limits_fixture[1],
         cell_capacity,
     )
-    return [cell_capacity, pe_capacity, ne_capacity, stoich_offset]
+    return [cell_capacity, pe_capacity, ne_capacity, li_inventory]
 
 
 @pytest.fixture
 def eol_capacity_fixture(eol_ne_limits_fixture, eol_pe_limits_fixture):
     """Return the cell and electrode capacities."""
     cell_capacity = 4.5
-    pe_capacity, ne_capacity, stoich_offset = Simple_OCV_fit.calc_electrode_capacities(
+    pe_capacity, ne_capacity, li_inventory = Simple_OCV_fit.calc_electrode_capacities(
         eol_pe_limits_fixture[0],
         eol_pe_limits_fixture[1],
         eol_ne_limits_fixture[0],
         eol_ne_limits_fixture[1],
         cell_capacity,
     )
-    return [cell_capacity, pe_capacity, ne_capacity, stoich_offset]
+    return [cell_capacity, pe_capacity, ne_capacity, li_inventory]
 
 
 @pytest.fixture
@@ -69,7 +69,7 @@ def bol_result_fixture(bol_capacity_fixture):
                 "Cell Capacity": bol_capacity_fixture[0],
                 "Cathode Capacity": bol_capacity_fixture[1],
                 "Anode Capacity": bol_capacity_fixture[2],
-                "Stoichiometry Offset": bol_capacity_fixture[3],
+                "Li Inventory": bol_capacity_fixture[3],
             }
         ),
         info={},
@@ -85,7 +85,7 @@ def eol_result_fixture(eol_capacity_fixture):
                 "Cell Capacity": eol_capacity_fixture[0],
                 "Cathode Capacity": eol_capacity_fixture[1],
                 "Anode Capacity": eol_capacity_fixture[2],
-                "Stoichiometry Offset": eol_capacity_fixture[3],
+                "Li Inventory": eol_capacity_fixture[3],
             }
         ),
         info={},
@@ -118,10 +118,8 @@ def test_calculate_dma_parameters(
     expected_LAM_pe = 1 - eol_capacity_fixture[1] / bol_capacity_fixture[1]
     expected_LAM_ne = 1 - eol_capacity_fixture[2] / bol_capacity_fixture[2]
     expected_LLI = (
-        bol_capacity_fixture[1]
-        - eol_capacity_fixture[1]
-        - (bol_capacity_fixture[3] - eol_capacity_fixture[3])
-    ) / bol_capacity_fixture[0]
+        bol_capacity_fixture[3] - eol_capacity_fixture[3]
+    ) / bol_capacity_fixture[3]
 
     result = dma_fixture.result
     assert result.data["SOH"].to_numpy()[1] == expected_SOH

tests/methods/ocv_fitting/test_simple_ocv_fit.py

@@ -134,7 +134,7 @@ def test_init(
         "Cell Capacity",
         "Cathode Capacity",
         "Anode Capacity",
-        "Stoichiometry Offset",
+        "Li Inventory",
     ]
 
 
@@ -157,5 +157,5 @@ def test_result(OCP_result_fixture, ocp_ne_fixture, ocp_pe_fixture):
         "Cell Capacity",
         "Cathode Capacity",
         "Anode Capacity",
-        "Stoichiometry Offset",
+        "Li Inventory",
     ]