KR101781825B1 - Appratus for setting limited voltage of secondary battery and method of the same - Google Patents

Abstract

The present invention relates to an apparatus and a method for setting a limited voltage of a secondary battery for a sufficient capacity of a secondary battery, A strain calculator for calculating strain values for an anode of the secondary battery according to an initial strain value and a variation of the charge voltage by the charge voltage regulator, and a strain calculator for calculating strain values calculated by the strain calculator, And a limited voltage detecting unit for detecting the limited voltage of the voltage detection unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery, and more particularly, to an apparatus and a method for setting a limited voltage of a secondary battery for a sufficient capacity of the secondary battery.

Recently, the development of electronics and information and communication industry has been rapidly growing through the portability, miniaturization, light weight, and high performance of electronic devices. A high performance lithium secondary battery is employed as a power source for such a portable electronic device, and the demand is rapidly increasing.

Rechargeable batteries that are used repeatedly for charging and discharging are essential for power supply for portable electronic devices, electric bicycles, and electric vehicles for information and communication. Particularly, the performance of these products depends on the battery, which is a core component, so the demand for a high performance battery is very large. The characteristics required for a battery include various aspects such as charge / discharge characteristics, life span, high rate characteristics, and stability at high temperatures, and lithium secondary batteries are most widely used.

Currently, LiCoO ₂ is used as a cathode active material in almost all commercialized lithium secondary batteries. LiCoO ₂ is a material with excellent charge / discharge characteristics, high electron conductivity, excellent rate characteristics and excellent thermal stability. However, recently, there is a need for a cathode active material for a lithium secondary battery having a high voltage and a large capacity. When LiCoO ₂ is continuously charged and discharged at a voltage higher than 4.3 V, the cathode active material is liable to react with an electrolyte due to lattice strain or destruction of crystal structure The lifetime characteristics and the safety are deteriorated. In addition, cobalt (Co), which is a starting material for cathode active materials, is in a trend of rising prices continuously because of a shortage of reserves. Further toxic and environmental pollution problems are required to develop alternative cathode active materials.

LiNiO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , and Li (Ni _a Co _b Mn _c ) O ₂ are examples of a cathode active material for a lithium secondary battery, which has been actively researched and developed at present. However, in the case of LiNiO ₂ is not only difficult to synthesize, because of a problem with thermal stability, it is difficult to commercialize, LiMn but a part commercialized in the case of low-price products ₂ O _4, structural modification due to Mn ³⁺ (Jahn-Teller distortion) Therefore, the life characteristics are not good. In addition, LiFePO ₄ is excellent in low cost and safety, and is currently being studied for HEV. However, it is difficult to apply LiFePO ₄ to other fields due to its low conductivity.

Therefore, the most popular material for LiCoO _{2 as} an alternative cathode active material is Li (Ni _a Mn _b Co _c ) O ₂ having a layered structure of R-3m.

However, when the positive electrode active material having a layered structure of R-3m is charged, the average crystal grain size and the lattice are deformed, and after a certain amount of charging, the lattice strain is changed. Such lattice strain can cause the intergranular fracture by eliminating the elasticity between particles after a certain amount of stress.

An object of the present invention is to provide a device and a method for setting a limited voltage of a battery using the layered positive electrode active material to detect and display a limited voltage in which degradation of the positive electrode structure does not occur.

The apparatus for setting a limited voltage of a secondary battery according to an embodiment of the present invention includes a charge voltage regulator for regulating a charge voltage of a secondary battery, an initial strain value, And a limiting voltage detector for detecting a limited voltage of the secondary battery using the strain values calculated by the strain calculator, wherein the anode of the secondary battery is Li (Ni _a Mn _b Co _c ) O ₂ structure. Here, a + b + c = 0.8-1.2, a = 0-1, b = 0-1, c = 0-1.

A method for setting a limited voltage of a secondary battery according to an embodiment of the present invention includes calculating an initial strain value of a secondary battery, calculating strain values of an anode of the secondary battery while changing a charging voltage of the secondary battery, And detecting a limited voltage of the secondary battery using an initial strain value and strain values corresponding to the change of the charging voltage. The anode of the secondary battery may include Li (Ni _a Mn _b Co _c ) O ₂ structure Of the cathode active material. Here, a + b + c = 0.8-1.2, a = 0-1, b = 0-1, c = 0-1.

The present invention can prevent degradation of the anode structure of a battery by finding and informing a limited voltage of the battery in which the layered structure cathode active material is used.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram briefly showing a configuration of a limited voltage setting device according to an embodiment of the present invention; FIG.
FIG. 2 is a flowchart illustrating a procedure for setting a limited voltage of a lithium secondary battery using the apparatus of FIG. 1;
FIG. 3 is a graph showing a relationship between a positive electrode of a secondary battery and a positive electrode of a Li (Ni _a Mn _b Co _c ) O ₂ (a + b + c = 0.8-1.2, a = 0-1, b = 0-1, Graphs showing changes in strain value as a function of charging voltage when made of an active material.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

FIG. 1 is a configuration diagram briefly showing the configuration of a limited voltage setting device for a secondary battery according to an embodiment of the present invention.

The limited voltage setting device of FIG. 1 includes a charge voltage regulator 10, a strain measurement unit 20, and a limited voltage detector 30.

The charging voltage regulator 10 regulates the charging voltage of the secondary battery 2. For example, the charging voltage regulator 10 supplies power to the secondary battery 2 to gradually increase the charging voltage of the secondary battery 2.

The strain calculating unit 20 calculates a strain value in a positive electrode of an initial discharge state (discharging state in which lithium is not discharged) or a positive electrode material of a raw material state (powder state) 10 calculates the strain value of the anode of the secondary battery 2 every time the charging voltage of the secondary battery 2 changes (increases), and transmits the calculated strain value to the limited voltage detecting unit 30. For example, the strain calculating unit 20 can obtain a strain using a single crystal X-ray diffraction (XRD) peak.

The limited voltage detector 30 controls the charging voltage controller 10 to increase the charging voltage of the secondary battery 2 in units of a constant level and uses the strain value provided by the strain calculator 20, Thereby detecting the limited voltage of the battery 2. [

FIG. 2 is a flowchart illustrating a procedure for setting a limited voltage of a lithium secondary battery using the apparatus of FIG.

In this embodiment, a case of using a cathode active material having a layered structure of Li (Ni _a Mn _b Co _c ) O ₂ is described.

First, the strain calculating unit 20 calculates an initial strain value of the battery 2 and transmits it to the limited voltage detecting unit 30 (step 210).

For example, the strain calculating unit 20 calculates the strain value of the anode of the secondary battery 2 in an initial discharge state in which lithium does not escape, and transmits the calculated value to the limited voltage detecting unit 30. [ To this end, the strain calculating unit 20 irradiates the anode of the secondary battery 2 coated with the active material with the X-ray according to the instruction of the limited voltage detecting unit 30, and then calculates the phase of the scattered X-ray (X- ), It is possible to calculate the strain value for the cathode active material.

A method for calculating the strain value using the X-ray diffraction method (XRD) may be any conventional technique, and therefore, a detailed description of a method for calculating the strain value using X-ray diffraction (XRD) It is omitted.

Although the case of calculating the strain value with respect to the anode of the secondary battery 2 in the initial discharge state of the battery 2 is described as the initial strain value in the above embodiment, Powder state) can be calculated by X-ray rotation method and used as an initial strain value.

When the cathode active material having a layered structure of R-3m such as Li (Ni _a Mn _b Co _c O ₂ ) is charged, lattice deformation occurs.

Therefore, the limited voltage detecting unit 30 controls the charging voltage adjusting unit 10 and the strain calculating unit 20 to gradually increase the charging voltage of the secondary battery 2 to a predetermined level, The strain value is calculated (step 220).

For example, the charging voltage regulator 10 makes the charging voltage of the secondary battery 20 approximately 0.1 V higher than the initial discharging voltage (approximately 3.6 V) in accordance with the instruction of the limited voltage detector 30. [ At this time, the strain calculating unit 20 calculates the strain value using the X-ray diffraction method (XRD) as in step 210 and transfers the strain value to the limited voltage detecting unit 30.

Then, the charge voltage regulator 10 raises the charge voltage of the secondary battery 2 by 0.1 V, and the strain calculator 20 calculates the strain value of the anode in the charge voltage state, .

This strain value calculation process is repeated until the charge voltage reaches a predetermined level.

In the present embodiment, the case where the charging voltage regulator 10 raises the charging voltage by 0.1 V has been described, but the magnitude of the voltage to be changed can be changed. Also, the magnitude of the charging voltage may be increased in units of the same level for each step without increasing the magnitude of the charging voltage.

FIG. 3 is a graph showing a relationship between a positive electrode of a secondary battery and a positive electrode of a Li (Ni _a Mn _b Co _c ) O ₂ (a + b + c = 0.8-1.2, a = 0-1, b = 0-1, Graphs showing changes in the strain value as a function of the charging voltage in the case of an active material.

(A) is a graph when the positive electrode active material has a Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ structure, (b) is a graph when the positive electrode active material has a Li (Ni _0.8 Mn _0.1 Co _0.1 ) O ₂ structure .

Referring to the graphs of FIG. 3, it is possible to know the voltage (the voltage at the point where the strain reaches the maximum) at the point where the strain value rises but does not rise any more but falls. The strain value at each charge voltage is 0.3 ~ 1.0%.

The limited voltage detecting unit 30 finds the voltage before the stress is relieved by using the strain values supplied from the strain calculating unit 20 and sets it as a limited voltage for the cathode active material of the corresponding secondary battery 230 .

For example, the limited voltage detector 30 sets the voltage corresponding to the peak value among the strain values supplied from the strain calculator 20 as a limited voltage of the corresponding secondary battery and displays the corresponding information as indicated by a dotted line in FIG. 3 .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It should be regarded as belonging to the claims.

2: secondary battery
10: charge voltage regulator
20: strain calculating section
30:

Claims (9)

A limited voltage setting device for a secondary battery comprising a cathode active material having _a Li (Ni _a Mn _b Co _c ) O ₂ structure,
A charge voltage regulator for regulating the charge voltage of the secondary battery;
A strain calculating unit for calculating strain values for an anode of the secondary battery according to an initial strain value and a change of the charging voltage by the charging voltage regulator; And
And a limited voltage detector for detecting a limited voltage of the secondary battery using the strain values calculated by the strain calculator,
Wherein the charge voltage regulator raises the charge voltage stepwise from an initial discharge state of the secondary battery to a predetermined level.
Here, a + b + c = 0.8-1.2
a = 0 to 1
b = 0 to 1
c = 0 to 1 delete 2. The apparatus of claim 1, wherein the strain calculator
Wherein strain values for the anode of the secondary battery are calculated every time the charging voltage is changed using X-ray diffraction (XRD). The apparatus of claim 3, wherein the limited voltage detector
Wherein the charge voltage corresponding to the highest value among the strain values is defined as the limited voltage. 2. The apparatus of claim 1, wherein the strain calculator
Wherein the strain value of the positive electrode in the initial discharge state of the secondary battery or the strain value of the positive electrode active material in the raw material state is calculated as the initial strain value. Calculating an initial strain value of a positive electrode active material in a raw material state or a strain value of an anode in an initial discharge state of the secondary battery;
Calculating strain values of an anode of the secondary battery in each step while raising a charging voltage stepwise from an initial discharge state of the secondary battery to a predetermined constant level; And
And detecting the limited voltage of the secondary battery using the initial strain value and the strain values corresponding to the change of the charging voltage,
Wherein the positive electrode of the secondary battery comprises a positive electrode active material having _a Li (Ni _a Mn _b Co _c ) O ₂ structure.
Here, a + b + c = 0.8-1.2
a = 0 to 1
b = 0 to 1
c = 0 to 1 delete delete The method of claim 6, wherein the step of detecting the limited voltage of the secondary battery
Wherein the charge voltage corresponding to the highest value among the strain values is defined as the limited voltage.

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