WO2017008991A1 - Charging method for lithium ion batteries - Google Patents

Abstract

The description covers an adaptive method for charging a rechargeable battery comprising the step of: charging the battery with a constant charging current I_Lad I during a CC (constant current) phase and charging the battery with a constant voltage U_Lad 20 during a CV (constant voltage) phase, comprising the step of: adapting the charging current I_Lad I to a parameter of the battery.

Description

 Charging method for lithium-ion batteries

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to an adaptive method for charging a rechargeable battery.

BACKGROUND OF THE INVENTION

In the prior art, the CC-CV charging method (also known as Ula charging method, U = voltage, I = current, a = switching off) for charging rechargeable batteries is known. The charging process can be divided into two phases. In a first phase, the battery is charged with a constant charging current. This increases the voltage of the battery. Upon reaching a threshold voltage, the second phase begins, wherein the voltage is kept constant and the charging current is variable. The charging current decreases in the second phase. If a minimum charge current is reached, the charging process is terminated.

SUMMARY OF THE INVENTION

Lithium-ion batteries (Li-ion batteries) have a real product life of about 5 to 20 years. To achieve the best possible amortization of the lithium-ion batteries, it would be desirable to fully exploit the potential life of the batteries. The lifetime of Li-ion batteries depends on different parameters. It is therefore an object to provide a method for making the best possible use of the potential lifetime of lithium-ion batteries.

As a first embodiment of the invention, there is provided an adaptive method for charging a rechargeable battery, comprising the step of charging the battery with a constant charging current I _Lad during a CC (Constant Current) phase and charging the battery at a constant voltage U _Lad during a CV (Constant Voltage) phase, including the step of: adjusting the

Charging current I _Lad to a parameter of the battery.

The embodiment of the invention results in a shorter charging time while increasing the potential life of the battery in question. In particular, initially a maximum charging current during the CC phase can be selected, which is increasingly reduced in the course of aging of the battery. For example, with a very old battery, the charging current can be determined as one third of the maximum charging current. It can thereby be ensured that a maximum high charging current can be selected depending on the aging state of the battery, which leads to a respective maximum fast charge of the battery.

As a second embodiment of the invention, a device for charging a rechargeable battery is provided, wherein the device is adapted to perform a method according to one of claims 1 to 11.

Exemplary embodiments are set forth in the dependent claims

described.

In a further embodiment according to the invention, a method is provided, wherein the charge current I _Lad constant during a CC phase is strictly monotonically decreasing over time and / or continuously decreasing and / or has a cut on each charge cycle and / or is constant on a consecutive series of charge cycles.

During the charging process, the charging current is kept constant. However, according to the invention, the charge current used is reduced from charge cycle to charge cycle. This can prevent the plating effect. Alternatively, during the transition from one charging cycle to the next charging cycle, a significant reduction of the charging current and, during one or subsequent transitions, the same charging current can be used. In a subsequent charging cycle, a reduction of the charging current can again take place, so that overall a strictly monotonically decreasing curve of the charging current takes place along a growing number of charging cycles.

According to an exemplary embodiment of the invention, a method is provided, wherein the parameter is the aging of the battery.

By adjusting the charging current to the aging progress of the battery, the effect of lithium-platings can be avoided. A long battery life can be ensured hereby.

In another embodiment of the invention, a method is provided wherein the method is a CC-CV charging method.

By using a standard CC-CV charging process, the specifications of the battery manufacturers can be met.

According to another embodiment of the present invention, there is provided a method wherein the battery is a lithium-ion battery and / or wherein the anode of the battery comprises graphite or silicon. In particular, in lithium-ion batteries can by the inventive

Procedure to extend the life of the battery and a minimum charging time can be achieved. According to an exemplary embodiment of the invention, a method is provided, wherein the aging results from the operating time of the battery, the charge throughput and / or the number of charge cycles.

The charge throughput is a good indicator of the aging progress of the battery. In an alternative embodiment, the aging progress of a

 Combination of service life of the battery and / or the charge flow rate and / or the number of charge cycles can be determined.

In a further embodiment according to the invention, a method is provided, comprising the step: adjusting the charging current I _Lad by means of a battery model and / or a variable derived therefrom and / or wherein the charging current I _{Lad is} strictly monotonically decreasing over time and / or the charging current I _Lad has constant sections over time. By using a model, a fast and accurate determination of the charging current can be made. It is essential that the invention is not an (improved) adaptation of parameters during a single charge. Rather, the charging parameters should be calculated depending on the aging state of the battery before a respective charging process. That is, the one hundredth charge of the battery will use a different (lower) maximum rate of current for the CC charge than it does on the first charge.

According to an exemplary embodiment of the invention, a method is provided, wherein the size is an impedance, an impedance value of the battery and / or the capacity of the battery. According to a further embodiment of the present invention, a method is provided, wherein the constant charge current I _Lad during a CC (Constant Current) phase of charging cycle to charge cycle has a reduction, which reduction is correlated with the decrease in the capacity of the battery and / or wherein the reduction with the increase of an impedance value

(Internal resistance) of the battery.

By adjusting the charging current according to the correlation to the current capacity or to a specific current impedance value of the battery, a respective maximum charging current can be used without a dramatic increase in the impedance value and / or a dramatic decrease in the capacity of the battery. In a further embodiment of the invention, a method is provided wherein the battery is less cooled or heated from charge cycle to charge cycle.

By adjusting the temperature to the number of charging cycles or to the current capacity or to the current impedance value of the battery, a dramatic increase in the impedance value and / or a dramatic decrease in the capacity of the battery can be prevented.

According to an exemplary embodiment of the invention, there is provided a method wherein the constant charge current I _Lad during a CC (Constant Current) phase from charge cycle to charge cycle has a reduction, the cumulative reduction being from 5% to 50% of the first Charging current I _Lad , preferably from 10%> to 30%> of the first charging current I _Lad , particularly preferably 20%> of the first charging current I _Lad , is. As an idea of the invention can be considered an age-dependent

Charging method for rechargeable batteries to provide. Here, a CC-CV charging method can be used, wherein in the first phase, the constant current phase (CC phase), a constant charging current is used, which is adapted to the aging of the battery. The older the battery, the lower the constant charging current can be selected. Aging can be determined by the number of charge cycles, the impedance value of the battery, and / or the capacity of the battery. In this way, the life of the battery can be significantly extended, resulting in a cheaper use of the battery. By the embodiments according to the invention, the lithium-plating effect can be counteracted.

Of course, the individual features can also be combined with each other, which can also be partially beneficial effects that go beyond the sum of the individual effects.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantages of the invention will be apparent from the in the

Drawings illustrated embodiments clearly. Show it

1 is an illustration of a CC-CV charging method,

FIG. 2 shows a development of the capacitance with charging currents I _Lad i <I _Lad 2 <I _Lad 3 with cyclic loading and a CC-CV charging method, FIG.

3 shows a development of the impedance value for charging currents I _Lad i <I _Lad 2 <I _Lad 3 for cyclic loading and a CC-CV charging method, 4 shows a reduction of the charging current according to the invention during the CC phase of a CC-CV charging method as a function of the aging progress of the relevant battery, FIG. 5 shows different CC-CV charging methods, wherein different charging currents 14, 15, 16 are used depending on the progress of aging be and

Fig. 6 curves 21, 24 of charging currents. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Fig. 1 shows the current and voltage curves 1, 2, 19, 20 during a CC-CV charging process. In a first phase until the time ti is the charging takes place with a constant current I 1 · _Lad Here, the voltage 2 rises up to a voltage U _Lad (CC-phase: Constant Current). Upon reaching this voltage U _Lad , the voltage is kept constant and the current I _Lad 19 decreases. Upon reaching a minimum current I _s d, the charging process is discontinued (CV phase: Constant Voltage).

Fig. 2 shows a cyclic aging behavior 3, 4, 5 of Li-ion batteries (Li-ion cells), wherein always the CC-CV charging method with different

Charging currents l _Lad i <l _Lad 2 <l _Lad 3 was applied. A high charging current I _Lad 3 leads after a relatively few equivalent full cycles (charging cycles) to a significant decrease in the relative capacity 3 of the battery. By decreasing the charging current I _Lad 2, the reduction of the relative capacitance 4 can be delayed, and a very small charging current I _Lad 3 can prevent a dramatic decrease in the capacitance 5. Nevertheless, the fundamental tendency of the decrease of the relative capacity 5 can not be prevented by the increase in the number of charging cycles. Fig. 3 shows the development of the impedance value 6, 7, 8 of the battery via a

Increase in charging cycles. It turns out that at a high charging current I _Lad 3, the impedance value 6 increases sharply already after a few charging cycles. lower

Charging currents I _Lad i, _Lad 2 lead to the fact that the rapid increase of the impedance value 7, 8 takes place only with a significantly higher number of charging cycles. The fundamental tendency that the impedance value 8 of the battery increases with the number of charging cycles can not be prevented.

FIGS. 2 and 3 show a bending behavior of the capacitance 3, 4 and the impedance value 6, 7 of the battery. Too low a capacity or too high an impedance value means that the battery is no longer operational and needs to be replaced. FIGS. 2 and 3 have shown

that the amount of the charge current i _Lad an impact on the life of the

has the relevant battery. Equivalent full cycles correspond to an equivalent amount of charge throughput.

Fig. 4 shows a characteristic curve 9 as a relationship between the aging progress 10, 11, 12 of a battery and different charging currents I _Lad i, l _Lad 2, l _Lad 3- This can with increasing age of the battery, ie with increasing number of charging cycles, a Reduction of the applied charging current I _Lad , wherein the charging current I _{Lad is} the constant charging current during the CC phase of the CC-CV charging method. For example, after only a few charging cycles or a low

Aging progress 10 the battery with a high charging current l _Lad 3 be charged. After a progress of the aging of the battery, a reduced charging current I _Lad 2 can be used. If the battery is already very old, can be a very small

Charging current I _Lad i be used. As a result, a "kinking" in accordance with FIGS 2 and 3, ie the dramatic increase in the impedance value or the dramatic decrease in the capacity of the battery can be delayed or prevented

ensured. Fig. 5 shows different charging currents 13, 14, 15, 16, 17, 18 during a CC-CV charging process. In this case, a high charging current 13 in a new battery and low charging currents 17, 18 used in old batteries to achieve a long life of the battery in question.

FIG. 6 shows curves 21, 24 according to the invention of charging currents over time or over the aging progress of the battery or over the number of charging cycles or over the charge throughput or over equivalent full cycles. Curve 21 represents an optimal choice of charging currents, with discrete points being chosen according to time. The curve 24 shows an alternative curve with falling

Curve sections 22 and constant curve sections 23. During the constant sections 23, the same charging current is used for several charging cycles. This results in a reduction 22 of the selected charging current. The capacity of a battery decreases with the increase in charging cycles. If the charging current is chosen to be the same for each charging cycle, the charging process is terminated faster and faster. However, this results, as in the later

Charging cycles too large a charging current is chosen, a drastic increase in the impedance value and a dramatic decrease in capacity (plating). In addition, at the beginning of the life of the battery is not optimally fast charging performed, since at the start of life, a higher charging current could be selected.

According to the invention, therefore, the charging current is adapted to the aging progress, whereby very fast charging operations at the beginning of the life of the battery can be achieved. Furthermore, the plating is avoided.

It should be noted that the term "comprise" further elements or

Does not preclude procedural steps, just as the term "a" and "an" does not preclude several elements and steps. The reference numerals used are for convenience of reference only and are not to be considered as limiting, the scope of the invention being indicated by the claims.

LIST OF REFERENCE SIGNS

1 current during a CC phase

 2 Voltage curve during a CC phase

3 Capacity curve with high charging current l _Lad 3

4 Capacity curve with medium charging current l _Lad 2

5 Capacity curve with low charging current I _Lad i

6 History of the impedance value at high charging current I _Lad 3

7 Course of the impedance value at average charging current I _Lad 2

8 Course of the impedance value at low charging current I _Lad i

 9 Characteristic curve as relationship between aging progress of the battery and charging current

 10 small age of the battery

 11 mean age of the battery

12 years old age of the battery

13 high charging current I _Lad 3

14 Characteristic curve with high charging current l _Lad 3

15 Characteristic curve at medium charging current l _Lad 2

16 Characteristic curve with small charging current I _Lad i

17 average charging current l _Lad 2

18 small charging current I _Lad i

 19 current curve during a CV phase

 20 voltage during a CV phase

 21 first inventive curve of the charging current

22 falling curve section

 23 constant curve section

 24 second curve of the charging current according to the invention

ti limit time CC phase and CV phase

t ₂ End of the charging process

lend charging current at discontinuation of the CV phase

I _Lad i is smaller charging current

Claims

An adaptive method of charging a rechargeable battery comprising the step of: Charging the battery with a constant charging current I _Lad (1) during a CC (Constant Current) phase and Charging the battery with a constant voltage U _Lad (20) during a CV (Constant Voltage) phase, characterized by the step: Adjusting the charging current I _Lad (1) to a parameter of the battery. 2. The method according to claim 1, characterized in that during a CC phase constant charging current I _Lad (1) over time is strictly monotonically decreasing and / or continuously falling and / or has a reduction in each charging cycle and / or constant on a consecutive series of charging cycles. 3. The method according to any one of claims 1 or 2, characterized in that the parameter is the aging or the aging progress of the battery. 4. The method according to any one of the preceding claims, characterized in that the method is a CC-CV charging method. 5. The method according to any one of the preceding claims, characterized in that the battery is a lithium-ion battery and / or wherein the anode of the battery Graphite or silicon. 6. The method according to any one of claims 3 to 5, characterized in that the aging results from the operating time of the battery, the charge throughput and / or the number of charging cycles. 7. The method according to any one of the preceding claims, characterized by the step: Adjusting the charging current I _Lad (1) by means of a battery model and / or a variable derived therefrom and / or wherein the charging current I _Lad (1) is strictly monotonically decreasing over time and / or the charging current I _Lad (1) over time has constant sections. 8. The method according to claim 7, characterized in that the size of a Impedance, the impedance value of the battery and / or the capacity of the battery. 9. The method according to any one of the preceding claims, characterized in that the constant charging current I _Lad (1) during a CC (Constant Current) phase of charging cycle to charging cycle has a reduction, the reduction correlated with the decrease in the capacity of the battery and or wherein the reduction correlates with the increase in the impedance value of the battery. 10. The method according to any one of the preceding claims, characterized in that the battery is less cooled or heated from charge cycle to charge cycle. A method according to any one of the preceding claims, characterized in that the constant charging current I _Lad (1) has a reduction during a CC (Constant Current) phase from charging cycle to charging cycle, the cumulative reduction amounting to 5% to 50%. of the first charging current I _Lad (1), preferably from 10% to 30%> of the first charging current I _Lad (1), particularly preferably 20%> of the first charging current I _Lad (1). 12. Device for charging a rechargeable battery, characterized in that the device is suitable for carrying out a method according to one of the preceding claims.