Battery control device and battery system

1 . A battery control device configured to control charging of a lithium-ion battery in a vehicle battery system, the battery control device comprising:

a degraded battery state estimation unit that estimates a first degraded state of a battery on a basis of at least any one of a use history, a capacity retention rate, and an internal resistance increase rate of the battery and estimates a second degraded state of constituent elements inside the battery regarding each type of the battery;

a storage unit that stores information regarding an upper limit voltage of chargeable electric power with respect to each temperature of the battery based on a life model that defines degradation rates of constituent elements inside the battery, including positive electrode degradation rate, negative electrode degradation rate, and degradation rate caused by side reactions, where the life model is specific to the battery type and uses vehicle driving history and vehicle stop history stored in the storage unit; and

an upper limit voltage estimation unit that estimates the upper limit voltage of the chargeable electric power of the battery on a basis of the information and prevents lithium precipitation by dynamically adjusting charging parameters based on updated information to maintain safe battery operation while maximizing charging performance,

wherein the upper limit voltage estimation unit updates the information on a basis of the first degraded state and the second degraded state, and

wherein the upper limit voltage estimation unit generates control signals that are transmitted to charging circuitry to physically limit voltage applied to the battery during charging operations.

2 . The battery control device according to claim 1 ,

wherein the first degraded state is expressed by the capacity retention rate and the internal resistance increase rate; and

wherein the second degraded state is expressed by a positive electrode degradation rate and a negative electrode degradation rate of the battery, and a degradation rate caused by side reactions of the battery.

3 . The battery control device according to claim 2 ,

wherein if at least the capacity retention rate is smaller than a threshold value and the positive electrode degradation rate is larger than the threshold value, and the degradation rate caused by the side reactions is larger than the negative electrode degradation rate, the degraded battery state estimation unit calculates an index value based on a quotient obtained by dividing the degradation rate caused by the side reactions of an electrolyte of the battery by the negative electrode degradation rate and transmits the index value to the upper limit voltage estimation unit; and

wherein the upper limit voltage estimation unit updates the information on a basis of the index value.

4 . The battery control device according to claim 1 , wherein the information is a map in which with respect to each temperature of the battery, an area associated with the upper limit voltage lower than a first voltage threshold value is set as a first area capable of suppressing precipitation of metal ions in an electrolytic solution of the battery, an area associated with the upper limit voltage in excess of the first voltage threshold value is set as a second area incapable of suppressing the precipitation of the metal ions, and an area associated with the upper limit voltage equal to the first voltage threshold value is set as a threshold value area capable of suppressing the precipitation of the metal ions; and

wherein the upper limit voltage estimation unit updates the map to expand the first area and reduce the second area, or to reduce the first area and expand the second area.

5 . The battery control device according to claim 4 ,

wherein the upper limit voltage estimation unit:

calculates, as a second voltage threshold value, a product of the first voltage threshold value and an index value based on quotient obtained by dividing the degradation rate caused by the side reactions of the electrolyte of the battery by the negative electrode degradation rate; and

updates the map so that in the map, with respect of each temperature of the battery, an area associated with the upper limit voltage lower than the second voltage threshold value is set as the first area which is new and capable of suppressing the precipitation of the metal ions, an area associated with the upper limit voltage in excess of the second voltage threshold value is set as the second area which is new and incapable of suppressing the precipitation of the metal ions, and an area associated with the upper limit voltage equal to the second voltage threshold value is set as the threshold value area which is new and capable of suppressing the precipitation of the metal ions.

6 . The battery control device according to claim 1 ,

wherein the upper limit voltage estimation unit estimates and sets the upper limit voltage of the chargeable electric power with respect to each temperature of the battery on a basis of the updated information.

7 . The battery control device according to claim 1 , comprising an assembled battery where the battery is provided in plurality and the plurality of batteries are connected to each other,

wherein the battery control device sets the upper limit voltage of the chargeable electric power with respect to each temperature of the battery on a basis of the updated information and controls the batteries and the assembled battery.

8 . The battery control device according to claim 1 , wherein the degraded battery state estimation unit estimates the second degraded state based on a life model that defines degradation rates of constituent elements inside the battery, including positive electrode degradation rate, negative electrode degradation rate, and degradation rate caused by side reactions, where the life model is specific to the battery type and uses vehicle driving history and vehicle stop history stored in the storage unit, and

wherein the upper limit voltage estimation unit prevents lithium precipitation by dynamically adjusting charging parameters based on the updated information to maintain safe battery operation while maximizing charging performance.

9 . The battery control device according to claim 1 , further comprising:

an assembled battery where the battery is provided in plurality and the plurality of batteries are connected to each other,

wherein the upper limit voltage estimation unit estimates and sets the upper limit voltage of the chargeable electric power with respect to each temperature of the battery on a basis of the updated information, and

wherein the battery control device controls charging of a lithium-ion battery in a vehicle battery system by preventing metal ion precipitation in an electrolytic solution while maximizing usable charging capacity through temperature-specific voltage adjustments.

10 . The battery control device according to claim 1 , wherein, when at least the capacity retention rate is smaller than a threshold value and the positive electrode degradation rate is larger than the threshold value, and the degradation rate caused by the side reactions is larger than the negative electrode degradation rate, the degraded battery state estimation unit calculates an index value based on a quotient obtained by dividing the degradation rate caused by the side reactions of an electrolyte of the battery by the negative electrode degradation rate and transmits the index value to the upper limit voltage estimation unit,

wherein the upper limit voltage estimation unit updates the information on a basis of the index value, and

wherein the information is a map in which with respect to each temperature of the battery, an area associated with the upper limit voltage lower than a first voltage threshold value is set as a first area capable of suppressing precipitation of metal ions in an electrolytic solution of the battery, an area associated with the upper limit voltage in excess of the first voltage threshold value is set as a second area incapable of suppressing the precipitation of the metal ions, and an area associated with the upper limit voltage equal to the first voltage threshold value is set as a threshold value area capable of suppressing the precipitation of the metal ions.

11 . The battery control device according to claim 10 , wherein the upper limit voltage estimation unit calculates, as a second voltage threshold value, a product of the first voltage threshold value and the index value based on the quotient obtained by dividing the degradation rate caused by the side reactions of the electrolyte of the battery by the negative electrode degradation rate, and

wherein the upper limit voltage estimation unit updates the map so that in the map, with respect of each temperature of the battery, an area associated with the upper limit voltage lower than the second voltage threshold value is set as the first area which is new and capable of suppressing the precipitation of the metal ions, an area associated with the upper limit voltage in excess of the second voltage threshold value is set as the second area which is new and incapable of suppressing the precipitation of the metal ions, and an area associated with the upper limit voltage equal to the second voltage threshold value is set as the threshold value area which is new and capable of suppressing the precipitation of the metal ions, thereby expanding the first area and reducing the second area to exhibit charging performance safely and to a maximum in consideration of suppressing the precipitation of the metal ions in the electrolytic solution of the battery.

12 . The battery control device according to claim 1 , wherein the degraded battery state estimation unit estimates the second degraded state based on a life model that defines degradation rates of constituent elements inside the battery, including positive electrode degradation rate, negative electrode degradation rate, and degradation rate caused by side reactions, where the life model is specific to the battery type and uses vehicle driving history and vehicle stop history stored in the storage unit,

wherein the upper limit voltage estimation unit estimates and sets the upper limit voltage of the chargeable electric power with respect to each temperature of the battery on a basis of the updated information according to a degradation status inside the battery, and

wherein the upper limit voltage estimation unit variably controls the upper limit voltage of the chargeable electric power of the battery to prevent precipitation of metal ions in an electrolytic solution of the battery according to the degraded state inside the battery while making the upper limit voltage higher to secure chargeable amount of electric power even if degradation of the battery progresses.

13 . The battery control device according to claim 1 , wherein the upper limit voltage estimation unit calculates a ratio α based on formula α=k×(Csr/Cn) where Csr is the degradation rate caused by side reactions, Cn is the negative electrode degradation rate, and k is a specified constant, and updates the information by multiplying a voltage threshold value by this ratio α.

14 . The battery control device according to claim 1 , wherein the information stored in the storage unit is an upper limit voltage map that divides voltage ranges into first areas, threshold value areas, and second areas based on metal ion precipitation suppression capability, and the upper limit voltage estimation unit updates this map by changing threshold values to expand or reduce these areas based on the degraded states.

15 . The battery control device according to claim 1 , wherein the degraded battery state estimation unit performs diagnosis processing that compares SOHC with a threshold value SOHC_th and SOHR with a threshold value SOHC_th, and only proceeds to estimate the second degraded state when SOHC is lower than SOHC_th and SOHR is higher than SOHC_th, followed by comparing positive electrode degradation rate Cp with threshold Cp_th and confirming that degradation rate caused by side reactions Csr is higher than negative electrode degradation rate Cn before calculating a update ratio.

16 . The battery control device according to claim 1 , wherein the degraded battery state estimation unit uses a life model to calculate specific degradation rates including positive electrode degradation rate, negative electrode degradation rate, and side reaction degradation rate, and the upper limit voltage estimation unit updates a voltage threshold map by multiplying threshold values by a ratio calculated from these degradation rates to prevent metal ion precipitation during charging.