LITHIUM BATTERY SYSTEM AND CHARGE-DISCHARGE METHOD OF THE SAME

A lithium battery system is provided. The lithium battery system comprises a battery pack, a battery management module, and a cooling control module. The battery pack comprises a first battery module and a second battery module having different battery characteristics. The battery management module is electrically connected to the battery pack, and configured to control an operating condition of the battery pack according to the battery characteristics of the first battery module and the second battery module. The cooling control module is electrically connected to the battery management module and the battery pack, and configured to cool the battery pack according to an instruction of the battery management module. The application combines a variety of lithium batteries with different performances to obtain a lithium battery system with excellent comprehensive performance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. § 119 from China Patent Application No. 202210074480.0, filed on Jan. 21, 2022, in the China Intellectual Property Office, the contents of which are hereby incorporated by reference.

FIELD

The present disclosure relates to lithium battery technology field, especially relates to a lithium battery system and a charge-discharge method of the lithium battery system.

BACKGROUND

Currently, common lithium batteries comprise lithium cobalt oxide batteries, lithium manganate batteries, lithium titanate batteries, lithium iron phosphate batteries and ternary lithium batteries, etc. The common lithium batteries are named based on active materials of their positive electrodes, and the lithium batteries have different performance characteristics. A single type of lithium battery cannot be simultaneously meet the excellent in cycle life, safety, low temperature performance, high temperature performance, energy density, stability, cost, and charging speed, etc. For example, the lithium cobalt oxide battery has high cost, the lithium manganate battery has poor high temperature performance, the ternary lithium battery has high cost and complex process, the lithium titanate battery has low energy density and high cost, and so on. Therefore, applications of the single type of lithium battery is very limited. Even a ternary lithium battery with a high operating temperature range is characterized by huge performance differences at different temperatures, and therefore, resulting in voltage rebound and affecting cycle life.

Therefore, there is need to explore a solution for a lithium battery with excellent comprehensive property, which is suitable for complex and wide use environments.

DETAILED DESCRIPTION

The term “comprise,” when utilized, means “include, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the like. The term of “first”, “second” and the like, are only used for description purposes, and should not be understood as indicating or implying their relative importance or implying the number of indicated technical features. Thus, the features defined as “first”, “second” and the like expressly or implicitly include at least one of the feature.

Referring toFIG.1, one embodiment is described in relation to a lithium battery system100. The lithium battery system100comprises a battery pack10, a battery management module20, and a cooling control module30. The battery pack10comprises a first battery module11and a second battery module12. The first battery module11and the second battery module12have different battery characteristics. The battery management module20is electrically connected to the battery pack10, and the battery management module20can control an operating condition of the battery pack10according to the battery characteristics of the first battery module11and the second battery module12. The cooling control module30is electrically connected to the battery management module20. The cooling control module30is used to cool the battery pack10according to an instruction of the battery management module20.

The battery pack10can comprise a lithium battery. For example, the lithium battery can be lithium cobaltate oxide (LCO), lithium manganese oxide (LMO), lithium titanium oxide (LTO), ferrous lithium phosphate (LiFePO4, LFP), ternary lithium battery (NMC/NCA) or other common lithium batteries. Properties of lithium batteries with different polar materials are different. For example, LCO has excellent reversibility, high energy density, but poor safety and high cost; LMO has excellent safety, low cost, but poor performance recovery at high temperature; and the ternary lithium battery has high energy density, excellent cycle performance, excellent thermal stability, but high cost and complex manufacturing process. In one embodiment, the battery pack10selects two kinds of lithium batteries with different properties, to combine each property of the two kinds of lithium batteries, thereby improving a comprehensive property of the lithium battery system100.

An electrolyte of the lithium battery system100is not limited. The lithium battery system100can comprise liquid, gel, semi-solid, quasi-solid or all-solid types. A number of battery modules of the battery pack10are not limited. In one embodiment, the number of the battery module is more than two.

The battery management module20is electrically connected to the battery pack10. The first battery module11and the second battery module12can be separately controlled by the battery management module20according to a temperature of the battery pack10, to improve an overall performance of the battery pack10.

The cooling control module30can comprise an air-cooled cooling device or a liquid-cooled cooling device. A cooling medium of the cooling control module30can be water, oil or other heat transfer medium. A specific structure, a cooling method and the cooling medium of the cooling control module30are not limited, as long as the battery pack10can be cooled. The cooling control module30is electrically connected to the battery management module20and cools the battery pack10under a control of the battery management module20.

In one embodiment, the battery pack10further comprises a sensor40, the sensor40is electrically connected to the battery management module20, and the sensor40is used to detect environmental parameters of the battery pack10. The battery management module20controls charge and discharge the battery pack10, or start and stop of the cooling control module30according to the environmental parameters. The sensor40can comprise a temperature sensor40or a pressure sensor40, to detect a temperature or an air pressure of the battery pack10or an environment around the battery pack10. An ambient temperature of the battery pack10can be used to indirectly obtain the temperature of the battery pack10, but the battery pack10is usually sealed, there may be a safety hazard when the pressure is abnormal.

In one embodiment, the environmental parameters can comprise ambient temperature and/or ambient air pressure. A type of the environmental parameters depends on a type of the sensor40.

In one embodiment, the battery characteristics can comprise one or more of energy density, operating temperature range, service life, and discharge capacity.

In one embodiment, the first battery module11or the second battery module12can comprise one of the lithium cobalt oxide battery, the lithium manganate battery, the lithium titanate battery, the lithium iron phosphate battery, and the ternary lithium battery.

In one embodiment, the battery pack10can further comprise a temperature conduction device. The temperature conduction device connects the first battery module11and the second battery module12, and transfers a heat of the first battery module11and a heat of the second battery module12to each other, to balance the temperature of the first battery module11and the temperature of the second battery module12. Therefore, the temperature of the first battery module11and the temperature of the second battery module12have a tendency to change toward an average temperature of the first battery module11and the second battery module12.

Referring toFIG.2, one embodiment is described in relation to a charge-discharge method, and the charge-discharge method is used to the lithium battery system100. The lithium battery system100comprises the battery pack10, the battery management module20, and the cooling control module30. The battery pack10comprises the first battery module11and the second battery module12. A minimum operating temperature of the first battery module11is lower than a minimum operating temperature of the second battery module12; generally, battery types with a wide operating temperature range have relatively low energy density. In one embodiment, the first battery module11can be LTO or LFP, the second battery module12can be LCO, LMO or ternary lithium battery.

The charge-discharge method comprises steps as follows.

Step (S10): detecting the ambient temperature, and obtaining the temperature of the battery pack10according to the ambient temperature.

In step (S10), a current temperature of the battery pack10of the lithium battery system100can be directly or indirectly obtained by setting the sensor40.

Step (S20): when the temperature of the battery pack10is lower than the minimum operating temperature of the second battery module12and greater than the minimum operating temperature of the first battery module11, controlling the first battery module11to charge and discharge.

The first battery module11with a lower operating temperature is first started to charge and discharge, and the battery pack10can be partially charged and discharged. In this process, the first battery module11generates heat, and the heat can increase the temperature of the entire battery pack10through heat conduction; therefore, the temperature of the second battery module12can be increased to an operable temperature, and subsequently, the second battery module12with high energy density can be used for charging and discharging.

Step (S30): when the temperature of the battery pack10is greater than the minimum operating temperature of the second battery module12, controlling the second battery pack10to charge and discharge.

Through step (S20) and step (S30), an operating temperature range of the entire battery pack10can be expanded; and a utilization rate of the second battery module12with high energy density can also be improved, thereby improving a comprehensive charge and discharge performance of the battery pack10in a wider dimension.

Step (S40): when the temperature of the battery pack10is greater than a maximum operating temperature of the first battery module11, cooling the battery pack10by starting the cooling control module30.

In step (S40), after charging and discharging for a period of time, the temperature may gradually exceed the maximum operating temperature of the battery pack10. At this point, the temperature of the battery pack10can be detected and the battery module that has been exposed to unfavorable high temperatures can be turned off. At the same time, the cooling control module30is started to cool down the battery pack10, and then the corresponding battery module is started until the temperature drops to a suitable operating temperature range.

In this way, the second battery module12with a high minimum operating temperature range but high energy density can work within its suitable operating temperature range as much as possible. At the same time, it is also avoided to allow the first battery module11with low minimum operating temperature, high cycle life, high discharge rate but low energy density to work at low temperature for a long time. Therefore, the battery pack10is kept in a suitable operating temperature range for more time, and the overall performance is improved.

In one embodiment, after the step (S40) of when the temperature of the battery pack10is greater than the maximum operating temperature of the first battery module11, cooling the battery pack10by starting the cooling control module30, further comprising a step of: when the temperature of the battery pack10exceeds the maximum operating temperature of the second battery module12or the first battery module11, stopping charging and discharging the second battery module12or the first battery module11, and controlling the first battery module11or the second battery module12to drive the cooling control module30.

What needs to be explained is that when the temperature of the battery pack10exceeds the lower maximum operating temperature of the first battery module and the second battery module, the charging and discharging of the battery module with the lower maximum operating temperature is stopped, and the cooling control module30is driven by discharging another battery module with a higher maximum operating temperature to reduce the temperature.

When the temperature of the battery pack10is lower than the maximum operating temperature of the second battery module12or the first battery module11, stopping the first battery module11or the second battery module12, and controlling the second battery module12or the first battery module11to drive the cooling control module30.

What needs to be explained is that when the temperature drops below the operating temperature of the battery module with the lower maximum operating temperature, starting charging and discharging of the battery module with the lower maximum operating temperature, and stopping charging and discharging of another battery module with the higher maximum operating temperature. Thereby improving a service performance and the cycle life of the battery module with a large operating range.

In one embodiment, the step of when the temperature of the battery pack10exceeds the maximum operating temperature of the second battery module12or the first battery module11, stopping charging and discharging the second battery module12or the first battery module11, and controlling the first battery module11or the second battery module12to drive the cooling control module30, further comprising a step of: when the temperature of the battery pack10is lower than the maximum operating temperature of the second battery module12or the first battery module11, controlling the second battery module12and/or the first battery module11to drive the cooling control module30.

What needs to be explained is that when the temperature of the battery pack10is lower than the temperature of the battery module with a lower maximum operating temperature, only the battery module with the lower maximum operating temperature can be activated, or both battery modules can be activated at the same time.

In one embodiment, in step (S40), when the temperature of the battery pack10is greater than the maximum operating temperature of the first battery module11, starting the cooling control module30to cool the battery pack10comprises a step of driving the cooling control module30by an external power supply.

The lithium battery system100can be connected to the external power source, when the first battery module11and the second battery module12are both at a high temperature unsuitable for operation; the cooling control module30is activated by the external power source to reduce the temperature.

The lithium battery system100can include more than two battery modules, and the above charge-discharge method is also applicable to a control logic of any two battery modules among the more than two battery modules. The lithium battery system100is not limited to two battery modules.

The lithium battery system100of the present application can be used in scenes with a large temperature fluctuation range, such as a vehicle power system, a mobile terminal power supply system, and an industrial equipment energy system.

It is to be understood that the above-described embodiments are intended to illustrate rather than limit the present disclosure. Variations may be made to the embodiments without departing from the spirit of the present disclosure as claimed. Elements associated with any of the above embodiments are envisioned to be associated with any other embodiments. The above-described embodiments illustrate the scope of the present disclosure but do not restrict the scope of the present disclosure.