WO2018032557A1

WO2018032557A1 - Method and apparatus for metering remaining electric quantity of lithium-ion battery

Info

Publication number: WO2018032557A1
Application number: PCT/CN2016/098498
Authority: WO
Inventors: 鲍云; 鲍公舜
Original assignee: 上海绿耳新能源科技有限公司
Priority date: 2016-08-19
Filing date: 2016-09-09
Publication date: 2018-02-22
Also published as: CN106405424B; CN106405424A

Abstract

A method and apparatus for metering the remaining electric quantity of a lithium-ion battery. The method comprises the following steps: subjecting a lithium-ion battery to pulse discharging under a discharge current at a discharge time (301); obtaining a voltage difference between when the lithium-ion battery is not subjected to pulse discharging and when the lithium-ion battery is subjected to pulse discharging (302); and acquiring the remaining electric quantity of the lithium-ion battery according to the voltage difference (303).

Description

Method and device for measuring remaining amount of lithium ion battery

Technical field

The invention mainly relates to the technical field of measuring the remaining power of a lithium ion battery, and in particular to a method and a device for measuring the remaining power of a lithium ion battery.

Background technique

With the popularity of mobile communication products such as smart phones and notebook computers, the development of electric vehicles and the needs of solar cell applications, lithium-ion batteries as a high-energy secondary battery have a unique advantage before a better battery is available. Will be widely used for a long time. In many applications, it is necessary to know the remaining amount of lithium-ion battery in real time to estimate the available time of the battery.

At present, the known methods for measuring the remaining amount of lithium ion batteries mainly include a charge accumulation method and an open circuit voltage method. The charge accumulation method estimates the remaining battery capacity by measuring the net charge flowing into/out of the battery. The method integrates the total current flowing into/out of the battery to obtain the amount of electricity flowing in/out, and the initial battery power ± inflow/outflow = remaining battery. The initial battery charge can be preset or updated during the full charge and discharge cycle. This metering method relies on the initial battery charge and there is a cumulative error problem.

The open circuit voltage method obtains the remaining power by monitoring the open circuit voltage of the battery because there is a certain correspondence between the battery terminal voltage and the remaining power. However, the limitation of the method is that the correspondence needs to be established after the battery is left open for a long time. Only when the open circuit voltage of the battery is measured at a low load can the relatively accurate result be obtained, but the practical application needs to be in the charging and discharging process. Get the remaining power. Therefore, this method is not suitable for measuring the remaining battery power in real time.

In practice, there are attempts to improve or combine the two methods for residual power estimation, including various algorithms to improve the accuracy of the evaluation. These techniques include fuzzy logic, Kalman filtering, neural networks, recursion, self-learning, and more. However, the evaluation based on the charge accumulation method and the open circuit voltage method cannot fundamentally solve the inherent defects of the method, resulting in low accuracy and poor stability of the remaining amount of lithium ion battery.

Summary of the invention

The invention provides a method and a device for measuring the remaining electric quantity of a lithium ion battery, which can improve the accuracy and real-time performance of the measurement of the remaining electric quantity.

The invention provides a method for measuring the remaining electric quantity of a lithium ion battery, comprising the following steps: making lithium The ion battery performs pulse discharge at a discharge current and a discharge time; obtains a voltage difference between the pulse discharge of the lithium ion battery and the pulse discharge; and obtains the remaining power of the lithium ion battery according to the voltage difference described above.

According to an embodiment of the invention, the pulse discharge is performed a plurality of times and the voltage difference is determined a plurality of times, and an average value of the plurality of voltage differences is calculated.

According to an embodiment of the invention, the discharge time of the pulse discharge is the same for a plurality of times.

According to an embodiment of the invention, the discharge time of the pulse discharge is different a plurality of times.

According to an embodiment of the invention, the discharge current of the pulse discharge is the same for a plurality of times.

According to an embodiment of the invention, the discharge current of the pulse discharge is different a plurality of times.

According to an embodiment of the invention, the step of acquiring the remaining power of the lithium ion battery according to the voltage difference comprises: substituting the voltage difference into a correspondence between the predetermined voltage difference and the remaining power of the lithium ion battery to obtain a corresponding lithium. The remaining battery power of the ion battery.

The invention provides a metering device for remaining power of a lithium ion battery, comprising: a controllable conductive path connecting a positive electrode and a negative electrode of the lithium ion battery to discharge the lithium ion battery; and a voltage detector connecting the positive electrode of the lithium ion battery And a negative electrode to obtain a voltage difference between the pulse discharge and the non-pulse discharge of the lithium ion battery; a control unit connecting the conductive path and the voltage detector, the controller configured to perform the lithium ion battery under the discharge current and the discharge time Pulse discharge, and obtaining the voltage difference from the voltage detector; and a processing unit connected to the control unit to determine the remaining power of the lithium ion battery based on the voltage difference.

According to an embodiment of the invention, the controllable conductive path comprises a current source and a switch connected in series, the switch being connected to the control unit.

According to an embodiment of the invention, the control unit is configured to perform the pulse discharge a plurality of times, the processing unit being configured to determine the voltage difference a plurality of times and calculate an average of the plurality of voltage differences.

According to an embodiment of the invention, the control unit and the processing unit are integrated.

The invention also proposes a lithium ion battery device, comprising a lithium ion battery, and the above-mentioned metering device for remaining power of the lithium ion battery.

The above technical solution of the present invention performs rapid pulse discharge on both ends of a lithium ion battery, at which time the electrons of the positive electrode of the lithium ion battery are concentrated on the positive electrode side due to the separator; and the lithium ions deintercalated from the negative electrode temporarily accumulate on the negative electrode side due to the large mobility. . Thus, an instantaneous internal capacitance is formed inside the lithium ion battery, and the capacitance value is C=Q/V _c . Where Q is the charge accumulated on the surface of the capacitor; V _c is the voltage across the capacitor and is also equal to the voltage difference between the battery terminals before and after the pulse discharge. In the equivalent test environment, the capacitance value C remains unchanged, so the differential voltage V _c is proportional to the surface charge Q of the capacitor. Under the same pulse discharge condition, the density of the surface charge Q has a one-to-one correspondence with the lithium ion density of the negative electrode, so there is a one-to-one correspondence between the differential voltage V _c and the lithium ion density of the negative electrode. At this time, the negative lithium ion density in the microscopic world is indicating the remaining battery power in the macro world. Thus, the remaining power of the lithium ion battery can be directly obtained by pulse discharge-differential voltage detection.

Through the above technical solution, the invention can directly measure the remaining power of the lithium ion battery, has high real-time performance, and has a simple structure.

BRIEF abstract

Features and capabilities of the present invention are further described by the following examples and the accompanying drawings.

1 is an electrical schematic diagram of a metering device for remaining power of a lithium ion battery, in accordance with an embodiment of the present invention.

2 is a structural diagram of a lithium ion battery device including a metering device, in accordance with an embodiment of the present invention.

3 is a flow chart of a method for measuring the remaining amount of a lithium ion battery according to an embodiment of the invention.

Preferred embodiment of the invention

The above described objects, features and advantages of the present invention will become more apparent from the aspects of the appended claims.

In the following description, numerous specific details are set forth in the description of the invention, and the invention may be practiced otherwise.

The essence of the existing method for measuring the remaining amount of lithium ion battery is to estimate indirectly by measuring the state quantity such as voltage and current, so the measurement accuracy is limited.

Embodiments of the present invention describe a method of metering the remaining amount of lithium ion battery, which can be directly measured as a physical quantity of the lithium ion battery. Moreover, this method enables real-time measurements at various stages of the use of lithium-ion batteries.

1 is an electrical schematic diagram of a metering device for remaining power of a lithium ion battery, in accordance with an embodiment of the present invention. Referring to FIG. 1, the metering device of the present embodiment includes a current source 101, a switch 102, a voltage detector 103, a control unit 104, and a processing unit 105 for measuring the remaining power of the lithium ion battery 120. In the present embodiment, the lithium ion battery 120 may be composed of one or more battery cells. The current source 101 and the switch 102 are connected in series between the positive electrode and the negative electrode of the lithium ion battery 120 to form a controllable conductive path. In this conductive path, the current source 101 provides a discharge current, and the switch 102 can Closed under the control of the signal, the lithium ion battery 120 is discharged for a period of time. It will be appreciated that the controllable conductive path can take other forms. The voltage detector 103 is capable of detecting the voltage of the lithium ion battery 120, which is embodied as the voltage between the positive and negative terminals of the battery.

The control unit 104 connects on the one hand the conductive path consisting of the current source 101 and the switch 102 and on the other hand the voltage detector 103. The controller 104 is configured to cause the lithium ion battery 120 to perform pulse discharge at a discharge current and a discharge time, and obtain between the first voltage V ₀ at the time of unpulsed discharge of the lithium ion battery 120 and the second voltage V ₁ at the time of discharge. Voltage difference. The discharge current I depends on the current source 101, and the discharge time t depends on the time the switch 104 is open, both of which may be known to the controller 104 or may be unknown. Current source 101 can be a constant current source or a variable current source. When a variable current source is used, control unit 104 can be coupled to current source 101 to control the magnitude of the discharge current. Controller 104 can send a pulse control signal to switch 102 to control when switch 102 is open. The level (e.g., high level) in the pulse control signal that causes switch 102 to open has a small duty cycle. It can be understood that the discharge performed in order to detect the remaining amount of electric power should be changed as small as possible, so that a pulse discharge of a shorter time is performed. Of course, pulse discharge also takes into account the internal factors of the lithium-ion battery, which will be discussed later. The discharge time t can have a wide range of choices, from tens of nanoseconds to hundreds of milliseconds. In general, t can be controlled at the microsecond level.

The control unit 104 is connected to the voltage detector 103 to obtain a voltage difference between the voltage V ₀ at the time of the unpulsed discharge and the voltage V ₁ at the time of the discharge. The voltage detector 103 can obtain a differential voltage value by calculation, and can also obtain a differential voltage value by differential voltage detection. When the differential voltage detection obtains the differential voltage value, the voltage detector 103 may not necessarily obtain the unpulsed discharge voltage V ₀ and the discharge voltage V ₁ , respectively, but directly obtain the voltage difference.

The processing unit 105 is connected to the control unit 104 for determining the remaining power of the lithium ion battery 120 based on the voltage difference V _c . In an embodiment, control unit 104 and processing unit 105 may be integrated. For example, the control unit 104 and the processing unit 105 are integrated on the same chip.

2 is a structural diagram of a lithium ion battery device including a metering device, in accordance with an embodiment of the present invention. Referring to FIG. 2, the lithium ion battery device includes a lithium ion battery 120. A typical lithium ion battery 120 includes a positive electrode 121, a negative electrode 122, an electrolyte and a separator 123, a positive electrode 124, and a negative electrode 125. When the battery is charged, lithium ions are generated on the positive electrode 121, and the generated lithium ions move to the negative electrode 122 through the electrolyte. There are many micropores in the negative electrode 122, and lithium ions reaching the negative electrode are embedded in the micropores. The more lithium ions are embedded, the higher the charging capacity. Also, when the battery is discharged, the lithium ions embedded in the negative electrode 122 are taken out and moved back to the positive electrode 121. The more lithium ions are returned to the positive electrode 121, the higher the discharge capacity.

When the switch 102 of the metering device is closed to generate a pulse discharge, the electrons cannot penetrate the diaphragm 123 and accumulate on the side of the positive electrode 121; the lithium ions deintercalated on the side of the negative electrode 122 have not yet penetrated the separator 123 at the negative electrode due to the large mobility. The 122 side gathers. This creates an instantaneous internal capacitance C inside the lithium ion battery, assuming its voltage is V _c . No discharge pulse, the voltage detector 103 detects the battery terminal voltage V _B value V _0; pulse discharge, due to the supply voltage V _c on the capacitance C exists instantaneously, the voltage detector 103 detects the battery terminal voltage V _B of The value V ₁ =V ₀ -V _c . Thus, by obtaining the voltage difference V ₀ -V ₁ at the time of the unpulsed discharge and the pulse discharge, the voltage V _c on the capacitor C can be obtained. In the equivalent test environment, the capacitance value C remains unchanged, so the voltage difference V _c is proportional to the surface charge Q of the capacitor. Under the same pulse discharge condition, the density of the surface charge Q has a one-to-one correspondence with the lithium ion density of the negative electrode, so there is a one-to-one correspondence between the voltage difference V _c and the lithium ion density of the negative electrode. The microscopic negative lithium ion number density is indicative of the macroscopic battery residual capacity. Characterized thereby remaining charge the lithium ion battery 120 is the voltage difference accurately by V _c.

After the production of the lithium ion battery 120, may be previously obtained correspondence relationship between the remaining charge and the voltage difference V _c the lithium ion battery 120 through a test. This correspondence can be saved by a table or a fitting function. In the process of using the lithium ion battery 120, after the voltage difference is obtained by the above device and method, the voltage difference can be substituted into the corresponding relationship between the predetermined voltage difference and the remaining power of the lithium ion battery to obtain the corresponding lithium ion battery 120. remaining battery.

Furthermore, in view of the instability of the single pulse discharge and measurement, the control unit 104 is configured to perform multiple pulse discharges, and the processing unit 105 is configured to obtain a voltage difference multiple times and calculate an average of the plurality of voltage differences as a final result. . In each pulse discharge, the discharge time may be the same or different. Similarly, the discharge currents may be the same or different.

As described above, the discharge time t can be controlled from several tens of nanoseconds to several hundred milliseconds. Of course, this is not a limitation. The selection of the discharge time t, in addition to considering the influence on the battery power, is also considered to be short enough to allow the lithium ions to temporarily penetrate the separator 123 and temporarily in the negative electrode 122 due to the large mobility. Side gathering.

The remaining power metering method of this embodiment has significant advantages over the known methods. First, by measuring the differential voltage V _c , the remaining amount of lithium ion battery can be directly measured, which leads to a significant increase in accuracy. According to the test, this metering method can increase the accuracy from 3%-8% in current applications to less than 1%. This is very difficult for lithium-ion battery residual power metering, and it is of great significance, because accurate residual power metering is the basis of the battery management system. For example, lithium-ion battery cells have large inconsistency and need to accurately measure power. In the case of equilibrium. Secondly, the metering method of the present embodiment can be measured in real time at various stages of use of the lithium ion battery, including when discharging. Furthermore, the metering method of the embodiment has a very simple structure and reduces the device cost.

3 is a flow chart of a method for measuring the remaining amount of a lithium ion battery according to an embodiment of the invention. Referring to FIG. 3, in summary, the method for measuring the remaining capacity of the lithium ion battery of the embodiment includes the following steps:

In step 301, the lithium ion battery is subjected to pulse discharge at a discharge current and a discharge time;

In step 302, a voltage difference between the pulse discharge of the lithium ion battery and the non-pulse discharge is obtained;

At step 303, the remaining power of the lithium ion battery is obtained based on the voltage difference.

The method of measuring the remaining amount of the lithium ion battery of the present embodiment can be carried out in the metering apparatus described above, but it is also understood that those skilled in the art can implement it in other metering apparatuses according to the spirit of the metering method.

Claims

A method for measuring the remaining amount of a lithium ion battery includes the following steps:

The lithium ion battery is subjected to pulse discharge under discharge current and discharge time;

Obtaining a voltage difference between a pulse discharge of a lithium ion battery and a pulse discharge;

The remaining amount of the lithium ion battery is obtained based on the voltage difference.
The method of measuring the remaining amount of a lithium ion battery according to claim 1, wherein the pulse discharge is performed a plurality of times and a voltage difference is obtained a plurality of times, and an average value of the plurality of voltage differences is calculated.
The method of measuring the remaining amount of a lithium ion battery according to claim 2, wherein the discharge time of the pulse discharge is the same for a plurality of times.
The method of measuring the remaining amount of a lithium ion battery according to claim 2, wherein the discharge time of the pulse discharge is different a plurality of times.
A method of measuring a remaining amount of a lithium ion battery according to claim 2, wherein the discharge current of the pulse discharge is the same a plurality of times.
The method of measuring the remaining amount of a lithium ion battery according to claim 2, wherein the discharge current of the pulse discharge is different a plurality of times.
The method for measuring a remaining amount of a lithium ion battery according to claim 1, wherein the step of obtaining a remaining amount of the lithium ion battery according to the voltage difference comprises: substituting the voltage difference into a predetermined voltage difference and a lithium ion battery In the correspondence relationship of the remaining electric power, the remaining electric quantity of the corresponding lithium ion battery is obtained.
A metering device for remaining battery power of a lithium ion battery, comprising:

a controllable conductive path connecting the positive and negative electrodes of the lithium ion battery to pulse discharge the lithium ion battery;

a voltage detector connecting the positive electrode and the negative electrode of the lithium ion battery to obtain a voltage difference between a pulse discharge and a non-pulse discharge of the lithium ion battery;

a control unit that connects the conductive path and the voltage detector, the controller configured to pulse discharge the lithium ion battery at a discharge current and a discharge time, and obtain the voltage difference from the voltage detector;

The processing unit is connected to the control unit, and determines the remaining power of the lithium ion battery according to the voltage difference.
A metering device for residual power of a lithium ion battery according to claim 8, wherein the controllable conductive path comprises a current source and a switch connected in series, the switch being connected to the control unit.
The apparatus for measuring the remaining amount of a lithium ion battery according to claim 8, wherein the control unit is configured to perform the pulse discharge a plurality of times, the processing unit is configured to obtain the voltage difference multiple times, and calculate a plurality of voltage differences average value.
The metering device for remaining power of a lithium ion battery according to claim 8, wherein the control unit and the processing unit are integrated.
A lithium ion battery device comprising a lithium ion battery, and a metering device for remaining power of the lithium ion battery according to any one of claims 8-11.