KR20230120766A - Charging method, charging appartus, and charging system of secondary battery - Google Patents

Abstract

Provides a secondary battery charging method, charging device, and charging system that can effectively reduce the charging time while securing battery life characteristics during rapid charging by suppressing gas generation inside the battery and substantially suppressing the precipitation of lithium metal do.
The secondary battery charging method is a step of determining each inflection point as a charge limit for each charging rate in the SOC-dV/dQ graph derived by measuring the SOC and voltage change rate dV/dQ of the secondary battery for each charging rate during charging (S1) ; Deriving a charging protocol for changing the pulse charging rate according to the charging rate for each SOC section set based on the SOC value at the charging limit for each charging rate (S2); and pulse-charging the secondary battery using the charging protocol (S3).

Description

Secondary battery charging method, charging device and charging system {CHARGING METHOD, CHARGING APPARTUS, AND CHARGING SYSTEM OF SECONDARY BATTERY}

The present invention relates to a method for charging a secondary battery, a charging device, and a charging system, and more particularly, to change the charging rate based on the charging limit and pulse-charge the secondary battery to shorten the rapid charging time while also securing the lifespan characteristics of the secondary battery It relates to a possible secondary battery charging method, charging device, and charging system.

Recently, not only research on increasing the charging capacity of lithium secondary batteries, but also research on fast charging technology for shortening the charging time is also being actively conducted.

A lithium secondary battery is composed of a positive electrode and a negative electrode. During rapid charging, gas is generated inside the battery or lithium metal is deposited on the surface of the negative electrode. In particular, the precipitated lithium metal continuously causes a side reaction in the battery due to its low electrochemical stability, thereby reducing the lifespan of the battery, and furthermore, causing a short circuit in the battery, resulting in loss of battery function or a risk of fire.

In addition, in order to improve the energy density of secondary batteries, electrode loading is gradually increasing, and it is difficult to secure fast charging characteristics for high-capacity secondary batteries due to reduced diffusion characteristics and increased resistance.

As a method of shortening the charging time without lithium metal precipitation, methods such as observing voltage changes or changing the charge rate (C-rate) value during charging are known, but conventional methods often depend on experimental results through trial and error. .

Korean Patent Publication No. 10-2011-0024707

One object of the present invention is a secondary battery charging method, charging device, and charging system capable of securing lifespan characteristics of a secondary battery by substantially suppressing gas generation and lithium metal precipitation inside the battery during rapid charging of a high-capacity secondary battery. is to provide

Another object of the present invention is to provide a secondary battery charging method, charging device, and charging system capable of efficiently shortening the rapid charging time for a high-capacity secondary battery.

In the secondary battery charging method according to an embodiment of the present invention, each inflection point is charged for each charging rate in the SOC-dV/dQ graph derived by measuring the SOC and voltage change rate dV/dQ of the secondary battery for each charging rate during charging of the secondary battery. Determining the limit (S1); Deriving a charging protocol for changing the pulse charging rate according to the charging rate for each SOC section set based on the SOC value at the charging limit for each charging rate (S2); and pulse-charging the secondary battery using the charging protocol (S3).

In the step (S1), the charging limit may be a lower value among the charging limit SOC of each of the negative electrode and the positive electrode measured at the same charging rate.

In the step (S1), the charging rate for deriving the charging limit for each charging rate may be 0.1 to 6C.

In the step (S2), the lower end value of the pulse charging rate may be greater than 0C.

In the step (S2), the charging rate for each section of the SOC may decrease for each section as the SOC increases.

In the step (S2), the charging rate for each SOC section may be 0.1 to 6C.

In the step (S2), the pulse period interval may be 0.1 to 5 seconds.

The secondary battery may include a cathode including a lithium-transition metal composite oxide; and a negative electrode including a carbon-based material and a silicon-based material.

A secondary battery charging device according to an embodiment of the present invention includes a measurement unit for measuring SOC and voltage change rate dV/dQ of the secondary battery for each charging rate when charging the secondary battery; In the SOC-dV/dQ graph derived from the data measured by the measurement unit, the charging limit for each charging rate is determined at each inflection point, and the charging rate for each SOC section is set based on the SOC value at the charging limit for each charging rate. a controller for deriving a charging protocol for changing a pulse charging rate according to the charging rate for each SOC section; and a charging unit configured to pulse-charge the secondary battery using the charging protocol.

A secondary battery charging system according to one embodiment of the present invention is a secondary battery charging system having a secondary battery, comprising: a measurement unit for measuring SOC and a voltage change rate dV/dQ of the secondary battery for each charge rate during charging of the secondary battery; In the SOC-dV/dQ graph derived from the data measured by the measurement unit, the charging limit for each charging rate is determined at each inflection point, and the charging rate for each SOC section is set based on the SOC value at the charging limit for each charging rate. a controller for deriving a charging protocol for changing a pulse charging rate according to the charging rate for each SOC section; and a charging unit configured to pulse-charge the secondary battery using the charging protocol.

According to one embodiment of the present invention, it is possible to provide a secondary battery charging method, charging device, and charging system capable of substantially suppressing gas generation and lithium metal deposition in the battery when rapidly charging a high-capacity secondary battery.

According to one embodiment of the present invention, it is possible to provide a secondary battery charging method, charging device, and charging system capable of efficiently shortening the rapid charging time for a high-capacity secondary battery and at the same time securing battery life characteristics.

1 is a diagram exemplarily illustrating a method of determining a charge limit of a secondary battery by deriving an inflection point from a SOC-dV/dQ graph.
2 is a diagram showing a SOC-dV/dQ graph derived by measuring dV/dQ of a potential change rate of a secondary battery negative electrode according to SOC while charging at different charging rates of 0.33 C to 2.5 C, in one embodiment.
3 is a diagram showing a SOC-dV/dQ graph derived by measuring dV/dQ of a potential change rate dV/dQ of a positive electrode of a secondary battery according to SOC while charging at different charging rates of 0.33 C to 2.5 C, in one embodiment.
4 is a diagram illustrating a case where a lower value of the pulse charging rate is 0C as a pulse charging protocol in which a charging rate is changed according to an SOC section of a secondary battery and pulse charging is applied, in one embodiment.
FIG. 5 is a diagram illustrating a case in which the lower value of the pulse charging rate exceeds 0C (0.33C) as a pulse charging protocol in which a charging rate is changed according to an SOC section of a secondary battery and pulse charging is applied, in one embodiment.
6 is a conceptual diagram illustrating a secondary battery charging device and a secondary battery charging system including the same according to an embodiment of the present invention.
7 is a graph showing discharge capacity according to the number of charge/discharge cycles in which secondary batteries were charged according to a cascade charge protocol of a comparative example and a pulse charge protocol (lower value of a pulse charge rate: 0 C) of an embodiment in order to compare life characteristics during rapid charging. It is a diagram showing the retention rate (%).
8 is a graph showing discharge according to the number of charge/discharge cycles in which secondary batteries were charged according to the cascade charge protocol of Comparative Example and the pulse charge protocol (lower value of pulse charge rate: 0.33 C) of one embodiment in order to compare lifespan characteristics during rapid charging. It is a diagram showing the capacity retention rate (%).
FIG. 9 is to compare the gas generation and lithium precipitation in the battery during rapid charging, the secondary battery was charged according to the cascade charging protocol of the comparative example and the pulse charging protocol of the embodiment, respectively, and the battery was dismantled after 300 charge/discharge cycles. It is a drawing showing the electrode cross section.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified in various forms, and the scope of the present invention is not limited to the embodiments described below.

In the case of a lithium secondary battery (hereinafter referred to as 'battery' or 'secondary battery'), charging and discharging reactions proceed based on an electrochemical reaction of lithium. In the case of the charging reaction, a de-intercalation reaction in which lithium inside the positive electrode active material is oxidized and released as lithium ions proceeds in the positive electrode, and an intercalation reaction in which lithium ions are inserted into the negative electrode active material in the negative electrode ) reaction takes place.

In general, it is known that the de-intercalation reaction at the anode proceeds at a faster rate than the intercalation reaction at the cathode.

Therefore, when the secondary battery is rapidly charged, the amount of lithium ions released from the inside of the cathode active material is greater than the amount of lithium ions inserted into the anode active material, and the lithium ions that are not inserted into the anode active material are reduced and deposited on the surface of the anode. A problem of precipitation with lithium metal may occur.

According to one embodiment of the present invention, the voltage change rate of the secondary battery is analyzed to determine the start time of lithium metal precipitation for each charge rate, and the charge limit for each charge rate is determined by measuring the SOC (State of Charge) value when lithium metal precipitation starts. By setting and changing the charging rate (C-rate) for each SOC section based on this, it is possible to prevent the precipitation of lithium metal during rapid charging, shorten the charging time through pulse charging, and secure the lifespan characteristics of the battery. can do.

Hereinafter, the present invention will be described in more detail through embodiments.

Secondary battery charging method

In the secondary battery charging method according to an embodiment of the present invention, each inflection point is charged for each charging rate in the SOC-dV/dQ graph derived by measuring the SOC and voltage change rate dV/dQ of the secondary battery for each charging rate during charging of the secondary battery. Determining the limit (S1); Deriving a charging protocol for changing the pulse charging rate according to the charging rate for each SOC section set based on the SOC value at the charging limit for each charging rate (S2); and pulse-charging the secondary battery using the charging protocol (S3).

Hereinafter, the step (S1) will be described with reference to FIGS. 1 to 3 .

1 is a diagram illustrating a method of determining the charging limit of a secondary battery by deriving an inflection point from a SOC-dV/dQ graph, and FIG. 2 is a voltage change rate dV/dV/ of a negative electrode of a secondary battery according to SOC It is a diagram showing the SOC-dV / dQ graph derived by measuring and charging dQ at different charging rates of 0.33C to 2.5C. It is a diagram showing the SOC-dV/dQ graph derived by measuring and charging at different charging rates of 0.33C to 2.5C.

The inventors of the present invention, in the process of rapidly charging the secondary battery, there is a point (inflection point) at which dV / dQ, which is the degree of change (slope) of the battery voltage (V) according to the charged amount (Q), rapidly changes according to the SOC It was confirmed (see FIG. 1), and it was determined that the SOC value at this inflection point was the time of precipitation of lithium metal according to the phase change of each of the anode and cathode or the time of occurrence of a side reaction due to the structure, that is, the charging limit at the corresponding charge rate. did

According to the above process, the secondary battery was charged at different charging rates, and the SOC value at the inflection point was measured, and this was determined as the charging limit for each charging rate.

In the step (S1), the charging limit may be a lower value among the charging limit SOC of each of the negative electrode and the positive electrode measured at the same charging rate.

When the charging limit of the secondary battery is set to the lower value of the charging limit of the negative electrode and the positive electrode, it is possible to charge the secondary battery without exceeding both the charging limits of the negative electrode and the positive electrode during charging, so that lithium metal is deposited at the negative electrode and the positive electrode. The occurrence of side reactions can be simultaneously suppressed.

The charging limit for each charging rate of the negative electrode may be each inflection point in a SOC-dV/dQ graph derived by measuring the SOC and potential change rate dV/dQ of the negative electrode for each charging rate.

The charging limit for each charging rate of the positive electrode may be each inflection point in a SOC-dV/dQ graph derived by measuring the SOC and potential change rate dV/dQ of the positive electrode for each charging rate.

In the step (S1), the charging rate for deriving the charging limit for each charging rate may be 0.1 to 6C.

Specifically, in the step (S1), the charging rate may be 0.2 to 3C, and may be 0.33 to 2.5C.

When the charging rate in the step (S1) is as described above, the charging time may be shortened by controlling the charging rate to an appropriate level or higher. In addition, by preventing the charging rate from being too high, reaching the charging limit at the same time as charging starts, increasing the resistance of the secondary battery and preventing the formation of an overvoltage state in the electrode can be prevented.

Hereinafter, the step (S2) will be described with reference to FIGS. 4 and 5.

4 is a pulse charging protocol in which the charging rate is changed according to the SOC section of a secondary battery and pulse charging is applied, in one embodiment, and is a diagram showing a case where the lower value of the pulse charging rate is 0C. FIG. As a pulse charging protocol in which the charging rate is changed according to the SOC section of the battery and pulse charging is applied, this diagram shows a case where the lower value of the pulse charging rate exceeds 0C (0.33C).

In the step (S2), the charging protocol for setting the charging rate for each SOC section based on the SOC value at the charging limit for each charging rate derived through the step (S1), and changing the pulse charging rate according to the set charging rate for each SOC section. can be derived.

Specifically, the SOC section is divided based on the SOC value at the charging limit point measured at a specific charging rate, the charging rate for each SOC section is set based on this, and the pulse charging rate is determined according to the SOC section based on the set charging rate for each SOC section. A step-by-step charging protocol can be derived. When the secondary battery is pulse-charged according to the above protocol, it can be stably rapidly charged without exceeding the charging limit.

In the step (S2), the charging protocol may apply a pulse charging method and change the pulse charging rate according to the charging rate for each SOC section.

Specifically, the lower and upper values of the pulse charging rate may be set for each SOC section so that the average value is the same as the charging rate for each SOC section.

For example, if the charging rate of the SOC range of 8 to 49% is set to 2C, the same pulse period interval is set and the lower value is set to 0C and the upper value is 4C, and the pulse charging rate is applied to the average charging rate in the SOC interval to 2C. can (see Figure 4).

In the case of the charging protocol applying the pulse charging method as described above, unlike the case where the charging rate within the SOC section is kept constant, a higher charging rate than the set charging rate (securing fast charging characteristics) and a lower charging rate (improving lifespan characteristics) are alternately applied. Accordingly, it is possible to secure a short charging time and further improve lifespan characteristics.

In the step (S2), the lower end value of the pulse charging rate may be greater than 0C.

In general, when pulse charging is applied, the lower value of the pulse charging rate is applied as 0C, but if the upper value is maintained and the lower value is increased to exceed 0C, the life characteristics of the secondary battery are secured and the charging time is further reduced. can make it

For example, when the charging rate of the SOC range of 8 to 49% is set to 2C, when the upper value of the pulse charging rate is maintained at 4C and the lower value is applied by increasing the lower value from 0C to 0.33C (see FIG. 5), the fast charging time can be shortened further.

Specifically, the lower value of the pulse charge rate may be greater than 0C, may be greater than 0.1C, may be greater than 0.3C, may be less than 1C, may be less than 0.7C, and may be less than 0.4C.

In general, applying a lower value of the lower pulse charging rate is to ensure that lithium ions that have moved to the negative electrode during the charging process are smoothly diffused within the electrode. If lithium metal precipitation does not occur on the negative electrode, the upper value of the pulse charging rate is maintained and It is possible to further shorten the charging time by increasing the .

Therefore, when the lower value of the pulse charging rate within the interval is applied to exceed 0C as described above, the rapid charging time can be further shortened without problems such as precipitation of lithium metal.

In the step (S2), the charging rate for each section of the SOC may decrease for each section as the SOC increases.

Specifically, charging may be started at a relatively high charging rate, and charging may be performed while gradually decreasing the charging rate for each section according to an increase in SOC.

When such a charging protocol is applied, the charging time can be substantially shortened by starting charging at a high charging rate, and charging can be completed more stably by gradually decreasing the charging rate.

In the step (S2), the charging rate for each SOC section may be 0.1 to 6C.

Specifically, in the step (S2), the charging rate for each SOC section may be 0.3 to 3C, and may be 0.5 to 2C.

In the step (S2), when the charging rate for each SOC section is as described above, the charging time can be shortened by controlling the charging rate to an appropriate level or higher. In addition, by preventing the charging rate from being too high, reaching the charging limit at the same time as charging starts, increasing the resistance of the secondary battery and preventing the formation of an overvoltage state in the electrode can be prevented.

In the step (S2), the pulse period interval may be 0.1 to 5 seconds.

Specifically, in the step (S2), the pulse period interval may be 0.5 to 3 seconds, and may be 0.7 to 1.5 seconds. More specifically, in the step (S2), the pulse period interval may be 1 second.

The pulse period interval may be divided into a pulse period (a period in which the upper value of the pulse charging rate is applied) and a rest period (a period in which the lower value of the pulse charging rate is applied).

As the rest period is longer, lithium ions that have moved to the negative electrode are sufficiently diffused in the electrode, which is advantageous in performance such as life characteristics, but the charging time increases. On the other hand, as the idle period is shorter, the charging time can be shortened, but performance such as life characteristics may be deteriorated.

Therefore, during pulse charging in which the idle period and the pulse period are alternately applied, the rapid charging characteristics and battery life characteristics can be secured at the same time only when the period interval is appropriately controlled.

In the step (S2), when the pulse period interval is as described above, rapid charging characteristics and battery life characteristics can be secured at the same time.

Hereinafter, the step (S3) will be described.

In the step (S3), the secondary battery may be pulse-charged with the charging protocol derived through the step (S2).

When the secondary battery is pulse-charged according to the charging protocol, a more efficient charging time can be shortened by changing the pulse charging rate in consideration of the charging limit of the secondary battery, and life characteristics of the secondary battery can also be secured.

Secondary battery charging device

A secondary battery charging device according to an embodiment of the present invention includes a measurement unit 100 for measuring SOC and voltage change rate dV/dQ of the secondary battery for each charging rate when charging the secondary battery; In the SOC-dV/dQ graph derived from the data measured by the measurement unit, the charging limit for each charging rate is determined at each inflection point, and the charging rate for each SOC section is set based on the SOC value at the charging limit for each charging rate. a controller 200 for deriving a charging protocol for changing a pulse charging rate according to the charging rate for each SOC section; and a charging unit (E) configured to pulse-charge the secondary battery using the charging protocol.

The secondary battery charging method and charging protocol described above can be realized through the secondary battery charging device.

Hereinafter, the measuring unit 100, the controller 200, and the charging unit E will be described with reference to FIG. 6 .

The measurement unit 100 may measure the SOC and the voltage change rate dV/dQ of the secondary battery for each charging rate when the secondary battery C is being charged. A detailed description of the SOC, voltage change rate, etc. is omitted because it overlaps with the above description.

The controller 200 determines the charging limit for each charging rate at each inflection point in the SOC-dV/dQ graph derived from the data measured by the measuring unit 100, and based on the SOC value at the charging limit for each charging rate. A charging protocol for setting a charging rate for each SOC section and changing a pulse charging rate according to the set charging rate for each SOC section may be derived. Detailed descriptions of the charging limit for each charging rate, the charging rate for each SOC section, the pulse charging rate, etc. are duplicated with the above description, so description thereof will be omitted.

The charging unit E may pulse-charge the secondary battery using the charging protocol. A detailed description of the charging protocol, pulse charging, etc. is omitted because it overlaps with the above description.

The charging unit E may have a form including a measuring unit 100 and a control unit 200 therein (see FIG. 6 ), or may be an independent type (not shown). That is, as long as the secondary battery charging method and charging protocol according to the present invention can be applied to the charging unit E, the measuring unit 100, and the control unit 200, the shape and arrangement thereof are not particularly limited.

Secondary battery charging system

A secondary battery charging system according to an embodiment of the present invention is a secondary battery charging system including a secondary battery (C), and measures the SOC and voltage change rate dV/dQ of the secondary battery for each charging rate during charging of the secondary battery. section 100; In the SOC-dV/dQ graph derived from the data measured by the measurement unit, the charging limit for each charging rate is determined at each inflection point, and the charging rate for each SOC section is set based on the SOC value at the charging limit for each charging rate. a controller 200 for deriving a charging protocol for changing a pulse charging rate according to the charging rate for each SOC section; and a charging unit (E) configured to pulse-charge the secondary battery using the charging protocol.

Detailed descriptions of the measurement unit 100, the control unit 200, the charging unit E, and the like are omitted because they overlap with the above descriptions.

secondary battery

The secondary battery may include a positive electrode including a lithium-transition metal composite oxide.

Specifically, the lithium-transition metal composite oxide is Li _x Ni _a Co _b Mn _c O _y (0<x≤1.1, 2≤y≤2.02, 0<a<1, 0<b<1, 0<c< It may be an NCM-based positive electrode active material represented by the formula of 1, 0<a+b+c≤1).

The negative electrode may include a carbon-based material and a silicon-based material.

The charging method, charging device, and charging system according to the present invention can be applied without particular limitation as long as it is a secondary battery containing lithium ions therein, but includes a positive electrode including an NCM-based positive electrode active material; and a negative electrode including a carbon-based material and a silicon-based material, and has excellent usability for a lithium secondary battery having a relatively high capacity.

Hereinafter, examples are provided to aid understanding of the present invention, but these examples are merely illustrative of the present invention and do not limit the scope of the appended claims, and the examples within the scope and spirit of the present invention It is clear to those skilled in the art that various changes and modifications are possible, which also fall within the scope of the appended claims.

Examples and Comparative Examples

1) Preparation of secondary battery

Secondary examples and comparative examples of a lithium secondary battery including NCM-based active material, which is a Li-transition metal composite oxide, in a positive electrode, and containing graphite, which is a carbon-based material, and SiO _z (0<z<2), which is a silicon-based material, in a negative electrode. It was applied as a cell sample .

2) Measurement of charging limit by charging rate and deduction of charging protocol

From 8% SOC to 80% SOC with 9 different charging rates (0.33C, 0.75C, 1.0C, 1.25C, 1.5C, 1.75C, 2.0C, 2.25C, 2.5C) between 0.33 and 2.5C The graphs derived by measuring dV/dQ of the potential change rates of the negative electrode and the positive electrode according to SOC after each charge are shown in FIGS. 2 and 3, respectively.

The SOC value at the inflection point at which the slope of dV / dQ according to SOC rapidly changes in the negative and positive electrodes was measured according to each charging rate, and the lower value was set as the charging limit at the corresponding charging rate and shown in Table 1 below.

When the charge rate is 0.33C, no point judged as the charge limit is found within the corresponding section, so after the charge limit SOC value (cathode: 77.5%, cathode: 77%) of 0.75C charge rate, the charge rate of 0.5C (0.33 It was charged up to 80% SOC by applying the charging limit of C and 0.75C and the numerical value according to interpolation).

C-rate (C) cathode anode Charging limit setting value SOC
(%) △SOC
(%) charging time
(s) SOC
(%) △SOC
(%) charging time
(s) SOC
(%) △SOC
(%) charging time
(s) 0.5 80 2.5 3.0 80 3 3.6 80 3 3.6 0.75 77.5 6.5 5.2 77 6.5 5.2 77 6.5 5.2 One 71 9.5 5.7 70.5 6 3.6 70.5 9 5.4 1.25 61.5 4.1 2.0 64.5 8.5 4.1 61.5 5.5 2.6 1.5 57.4 3.4 1.4 56 3.5 1.4 56 3.5 1.4 1.75 54 4.7 1.6 52.5 3.5 1.2 52.5 3.5 1.2 2 49.3 3.9 1.2 49 6 1.8 49 6 1.8 2.25 45.4 3.4 0.9 43 2 0.5 43 2 0.5 2.5 42 34 8.2 41 33 7.9 41 33 7.9 Total charging time (s) - - 29.1 - - 29.3 - - 29.7

A standard protocol for charging according to the charging rate for each SOC section shown in Table 2 below was derived in consideration of the charging limit setting value set according to Table 1 and the actual fast charging characteristic data (lithium metal precipitation, etc.).

C-rate (C) standard protocol SOC (%) △SOC (%) Charging time (s) 0.5 80 One 1.2 0.75 79 6.5 5.2 One 72.5 9 5.4 1.25 63.5 5.5 2.6 1.5 58 3.5 1.4 1.75 54.5 5.5 1.9 2 49 41 12.3 Total charging time (s) - - 30.0

A protocol for applying pulse charging in the form shown in FIG. 4 was applied as the charging protocol by setting the upper and lower values of the pulse charging rate based on the charging rate value for each SOC section according to the reference protocol.

At this time, 1 second was applied to both the pulse period and the rest period as the pulse period interval.

A charging protocol with a lower value of the pulse charging rate of 0C was set as the first charging protocol, and a charging protocol with a value higher than 0C of 0.33C was set as the second charging protocol.

The case where the lithium secondary battery sample was charged with the first charging protocol was set as Example 1, and the case where the sample was charged with the second charging protocol was set as Example 2.

Comparative Example 1 is a protocol charging based on 35 minutes in the form of a standard protocol that keeps the charging rate constant for each SOC section without applying pulse charging and decreases the charging rate stepwise according to the SOC. Charging based on 30 minutes The protocol was set to Comparative Example 2.

3) Evaluation of rapid charging and life characteristics

The secondary battery sample was rapidly charged and then discharged (0.3C, SOC 8, CC cut-off) by dividing the section in the SOC 8-80% range for 30 or 35 minutes at room temperature (25 ° C) according to the protocols of Examples and Comparative Examples. While repeating the cycle, the discharge capacity retention rate compared to the initial discharge capacity was measured in %.

Comparing Example 1 and Example 2, even if the same pulse charging method is applied, the charging time of Example 2 using the second charging protocol set so that the lower value of the pulse charging rate exceeds 0C is 30 minutes, whereas the first Example 1 to which the charging protocol was applied was shown as 35 minutes, confirming that the charging time of Example 2 was reduced by about 15% compared to Example 1.

Comparing Example 1 and Comparative Example 1 with reference to FIG. 7 , it can be seen that the discharge capacity of Example 1 is maintained higher after 300 or more charge/discharge cycles even when rapid charging is completed with the same charging time (35 minutes). can Through this, even if the charging rate for each SOC section is the same, it is determined that the secondary battery of Example 1 to which the first charging protocol of the pulse charging method is applied has better lifespan characteristics.

Comparing Example 2 with Comparative Examples 1 and 2 with reference to FIG. 8, in the case of Example 2 applying the second charging protocol set so that the lower value of the pulse charging rate exceeds 0 C, the charging time compared to Comparative Example 1 is about 15% While being shortened, it has excellent life characteristics of the same level, and the discharge capacity is maintained higher after 300 or more charge and discharge cycles compared to Comparative Example 2, so it can be seen that the life characteristics are more excellent.

Referring to FIG. 9, as a result of disassembling the secondary batteries of Example 2 and Comparative Example 2 after rapid charging, and observing the cross-section of the electrode, gas generation in Example 2 was alleviated compared to Comparative Example 2, as well as precipitation of lithium metal. suppression can be observed.

Considering the above results, when the secondary battery is rapidly charged according to the charging protocol applying the pulse charging method in consideration of the charging limit as in Examples 1 and 2, the rapid charging time can be shortened, and the lithium metal It is judged that excellent life characteristics and long-term durability can be secured by suppressing precipitation and mitigating gas generation in the electrode.

In particular, when the lower end value of the pulse charging rate is set to more than 0 C as in Example 2, it is determined that the charging time can be further shortened while maintaining the life characteristics at an excellent level.

Claims (10)

Determining each inflection point as a charging limit for each charging rate in the SOC-dV/dQ graph derived by measuring the SOC and voltage change rate dV/dQ of the secondary battery for each charging rate during charging (S1);
Deriving a charging protocol for changing the pulse charging rate according to the charging rate for each SOC section set based on the SOC value at the charging limit for each charging rate (S2); and
Pulse charging the secondary battery with the charging protocol (S3); including,
Secondary battery charging method.
According to claim 1,
In the step (S1), the charge limit is the lower value of the charge limit SOC of each of the negative electrode and the positive electrode measured at the same charge rate,
Secondary battery charging method.
According to claim 1,
In the step (S1), the charging rate for deriving the charging limit for each charging rate is 0.1 to 6C,
Secondary battery charging method.
According to claim 1,
In the step (S2), the lower value of the pulse charging rate is greater than 0C,
Secondary battery charging method.
According to claim 1,
In the step (S2), the charging rate for each section of the SOC decreases for each section as the SOC increases.
Secondary battery charging method.
According to claim 1,
In the step (S2), the charging rate for each SOC section is 0.1 to 6C,
Secondary battery charging method.
According to claim 1,
In the step (S2), the pulse period interval is 0.1 to 5 seconds,
Secondary battery charging method.
According to claim 1,
The secondary battery,
a positive electrode including a lithium-transition metal composite oxide; and
A lithium ion secondary battery including a negative electrode including a carbon-based material and a silicon-based material,
Secondary battery charging method.
a measurement unit for measuring SOC and voltage change rate dV/dQ of the secondary battery for each charging rate when charging the secondary battery;
In the SOC-dV/dQ graph derived from the data measured by the measurement unit, the charging limit for each charging rate is determined at each inflection point, and the charging rate for each SOC section is set based on the SOC value at the charging limit for each charging rate. a controller for deriving a charging protocol for changing a pulse charging rate according to the charging rate for each SOC section; and
A charging unit configured to pulse charge the secondary battery with the charging protocol;
Secondary battery charging device.
As a secondary battery charging system having a secondary battery,
a measurement unit for measuring SOC and voltage change rate dV/dQ of the secondary battery for each charging rate when the secondary battery is charged;
In the SOC-dV/dQ graph derived from the data measured by the measurement unit, the charging limit for each charging rate is determined at each inflection point, and the charging rate for each SOC section is set based on the SOC value at the charging limit for each charging rate. a controller for deriving a charging protocol for changing a pulse charging rate according to the charging rate for each SOC section; and
A charging unit configured to pulse charge the secondary battery with the charging protocol;
Secondary battery charging system.

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