Charging method and application of lithium ion battery

Abstract

The invention provides a charging method and application of a lithium ion battery, and the charging method comprises the following steps: charging the lithium ion battery to a preset upper limit voltage at a preset rate at an initial temperature of 30-45 DEG C; and the lithium ion battery is charged at a constant voltage to a preset cut-off current. According to the charging method and the application of the lithium ion battery, the charging time can be shortened, and the discharging capacity of the lithium ion battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a charging method and application of a lithium-ion battery. Background Art

[0002] With the rapid development of smart grids, electric vehicles, and portable electronic products, secondary batteries, mainly lithium-ion batteries, have become one of the most widely used electrochemical energy storage devices. Lithium-ion electric vehicle systems need to meet the requirements of safety, mileage, and fast charging. Currently, battery suppliers are developing cells with higher fast charging capabilities to meet consumer needs. a Fe 1-a PO4, 0.4≤a≤0.8, LMFP) has the advantages of excellent safety, low temperature characteristics, high energy density and high cycle number, becoming a popular battery system to solve safety and mileage. However, the fast charging speed of the phosphate system is severely limited due to the one-dimensional ion channel, and the conductivity of lithium manganese iron phosphate is two orders of magnitude lower than that of lithium iron phosphate (LiFePO4, LFP). Therefore, the fast charging capability of the LMFP system is severely limited. Summary of the invention

[0003] The present invention provides a charging method and application of a lithium ion battery. Through the charging method and application of a lithium ion battery provided by the present invention, the charging time can be shortened and the discharge capacity of the lithium ion battery can be increased.

[0004] In order to solve the above technical problems, the present invention provides a charging method for a lithium ion battery, which at least comprises:

[0005] At a starting temperature, the lithium-ion battery is charged at a preset rate to a preset upper limit voltage, wherein the starting temperature is 30° C. to 45° C.; and

[0006] The lithium-ion battery is charged at a constant voltage to a preset cut-off current.

[0007] In one embodiment of the present invention, the starting temperature is 30°C to 40°C.

[0008] In one embodiment of the present invention, the starting temperature is 33°C to 35°C.

[0009] In one embodiment of the present invention, the preset magnification is, for example, 0.3C to 0.4C, and / or

[0010] The preset cut-off current is 0.01C to 0.1C.

[0011] In one embodiment of the present invention, the preset magnification is, for example, 0.33C, and / or,

[0012] The preset cut-off current is 0.05.

[0013] In one embodiment of the present invention, the lithium-ion battery is charged at a preset constant current rate to a preset upper voltage limit.

[0014] In one embodiment of the present invention, the lithium-ion battery is charged to a preset upper limit voltage by using a variable current at a preset rate.

[0015] In one embodiment of the present invention, the charging method further includes: after charging at a constant voltage to the preset cut-off current, lowering the temperature of the lithium-ion battery to 25° C., and then discharging at a constant current of 0.33C, and recording the discharge capacity of the lithium-ion battery.

[0016] In one embodiment of the present invention, the discharge capacity and the starting temperature satisfy the linear regression equation: y=0.0022x+0.3485, R 2 =0.9898, where x is the Calvin temperature of the starting temperature, y is the multiple of the discharge capacity of the lithium-ion battery at the preset starting temperature and the discharge capacity of the lithium-ion battery at 25°C, R 2 is the linear correlation constant.

[0017] In one embodiment of the present invention, the time proportion of the constant voltage charging in the charging process and the starting temperature satisfy the linear regression equation: m = -0.694x + 225.11, R2 = 0.9914, where x is the Calvin temperature of the starting temperature, m is the percentage value of the constant voltage charging time in the entire charging process, and R 2 is the linear correlation constant.

[0018] The present invention also provides a lithium ion battery which is charged by the above-mentioned charging method.

[0019] In one embodiment of the present invention, the lithium-ion battery comprises a positive electrode plate, the positive electrode plate comprises a positive electrode active material, and the positive electrode active material comprises LiMn a Fe 1-a PO4、LiMn a Fe 1-a PO4 and LiNi x Co y Mn 1-x-y Mixture of O2 or LiMn a Fe 1-a PO4 and LiNi b Co c Al 1-b-c A mixture of O2 wherein 0.4≤a≤0.8, 0.5≤x≤0.95, 0.05≤y≤0.2, 0.5≤b≤0.95, 0.05≤c≤0.2.

[0020] The present invention also provides an electronic device, comprising the lithium-ion battery mentioned above and a heating unit.

[0021] In summary, the present invention proposes a charging method and application of a lithium-ion battery, which increases the starting temperature of charging of the lithium-ion battery, can improve the kinetic characteristics of the active materials in the lithium-ion battery, reduce the polarization of the materials, increase the charging speed, and prevent safety problems caused by excessively high charging temperatures. The preset rate is controlled to reduce battery polarization and lithium precipitation to ensure the cycle performance of the lithium-ion battery. By first charging at a preset rate and then charging at a constant voltage, the kinetic characteristics of the active materials are improved, the polarization of the materials is reduced, and a higher discharge capacity is achieved. At the same time, the charging time can be shortened and the phenomenon of high virtual voltage can be reduced. That is, the discharge method provided by the present invention can simultaneously achieve the purpose of increasing the discharge capacity of the lithium-ion battery and shortening the charging time, thereby improving the applicability of the lithium-ion battery.

[0022] Of course, any method of implementing the present invention does not necessarily need to achieve all of the advantages mentioned above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0024] Figure 1 FIG. 4 is a flow chart of a charging method for a lithium-ion battery in one embodiment of the present invention.

[0025] Figure 2 is a linear regression equation between the multiple of the discharge capacity of the lithium ion battery and the starting temperature in one embodiment of the present invention.

[0026] Figure 3 A linear regression equation between CV time and starting temperature in one embodiment of the present invention.

[0027] Figure 4 It is the linear regression equation of the discharge capacity and the starting temperature of the lithium ion batteries of Examples 1-4 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] It should be understood that the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, providing these embodiments will make disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. If not otherwise specified, the "%" and "parts" shown in the following examples refer to "mass %" and "mass parts" respectively.

[0030] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] See also Figure 1 As shown, the present invention provides a charging method for a lithium-ion battery, and the charging method at least includes steps S11-S12.

[0032] Step S11, at a starting temperature, the lithium-ion battery is charged at a preset rate to a preset upper limit voltage, and the starting temperature is 30°C to 45°C.

[0033] Step S12: The lithium-ion battery is charged at a constant voltage to a preset cut-off current.

[0034] See also Figure 1 As shown, in one embodiment of the present invention, in step S11, at the starting temperature, the lithium-ion battery is charged to a preset upper limit voltage at a preset rate. At the preset rate, the lithium-ion battery is charged to a preset upper limit voltage, for example, at a constant current, to shorten the charging time. In another embodiment of the present invention, at a preset rate, the lithium-ion battery is charged to a preset upper limit voltage, for example, at a variable current. Wherein, the starting temperature is, for example, 30°C to 45°C, for example, 30°C to 40°C, and for example, 33°C to 35°C. By increasing the starting temperature of the lithium-ion battery charging and charging to the preset upper limit voltage at the starting temperature, the kinetic characteristics of the active material in the lithium-ion battery can be improved, the polarization of the material can be reduced, the charging speed can be increased, and the starting temperature can be controlled at the same time to prevent safety problems caused by excessively high charging temperatures. In this embodiment, the preset rate is, for example, 0.3C to 0.4C, and for example, 0.33C. By controlling the preset rate, the battery polarization and lithium precipitation phenomenon are reduced to ensure the cycle performance of the lithium-ion battery.

[0035] See also Figure 1As shown, in one embodiment of the present invention, in step S12, after the lithium-ion battery is charged to the upper limit voltage, the lithium-ion battery is then charged to a preset cutoff current at a constant voltage, wherein the preset cutoff current is, for example, 0.01C to 0.1C, and for example, 0.05C. In this embodiment, after constant voltage charging to the preset cutoff current, the temperature of the lithium-ion battery is lowered to room temperature, such as 25°C, and then constant current discharge is performed at 0.33C to record the discharge capacity of the lithium-ion battery. By charging the lithium-ion battery by the above charging method, the discharge capacity (or gram discharge capacity of the active material) of the lithium-ion battery can be increased by more than 1.5%, and the constant voltage charging (Constant Voltage, CV) time is significantly reduced. That is, by first charging to a preset upper limit voltage at a preset rate at a high temperature, and then charging at a constant voltage, the kinetic characteristics of the active material can be improved, the polarization of the material can be reduced, and a higher discharge capacity can be achieved. At the same time, the charging time can be shortened and the phenomenon of high virtual voltage can be reduced.

[0036] The present invention also provides a lithium-ion battery, including a positive electrode plate, a separator, a negative electrode plate and an electrolyte, wherein the separator is located between the positive electrode plate and the negative electrode plate, and the electrolyte is filled between the positive electrode plate, the separator and the negative electrode plate. The positive electrode plate includes a positive electrode active material, and the positive electrode active material includes LMFP, and for example, LMFP or a mixture of LMFP and other positive electrode active materials. The negative electrode plate includes a negative electrode active material, and the negative electrode active material is selected from any one or a combination of at least two of artificial graphite, natural graphite, soft carbon, hard carbon, pure silicon, silicon oxide compounds or silicon carbon compounds. The separator is, for example, a polyethylene film (Polyethylene, PE), a polypropylene film (Polypropylene, PP), a glass fiber film, a polyethylene film or a composite film, and the electrolyte can be any suitable commercial electrolyte.

[0037] See also Figure 2 As shown, in one embodiment of the present invention, the positive electrode active material includes, for example, LiMn a Fe 1-a PO4、LiMn a Fe 1-a PO4 and LiNi x Co y Mn 1-x-y Mixture of O2 or LiMn a Fe 1-a PO4 and LiNi b Co c Al 1-b-cA mixture of O2, wherein 0.4≤a≤0.8, 0.5≤x≤0.95, 0.05≤y≤0.2, 0.5≤b≤0.95, 0.05≤c≤0.2, and the discharge capacity of the positive electrode active material at 25°C (298.15K) is, for example, a mAh / g. After the positive electrode active material is prepared into a positive electrode plate, it is assembled with a negative electrode plate, a separator, and an electrolyte into a single lithium-ion battery, a battery module or a battery pack (Pack), etc., and then charged using the above charging method. Control the starting temperature, and charge the lithium-ion battery at different starting temperatures at the same preset rate, such as constant current, to a preset upper limit voltage, and then charge to the same preset cutoff current at a constant voltage. Lower the temperature of the lithium-ion battery to, for example, 25°C, and then discharge it at a constant current of, for example, 0.33C, and record the discharge capacity of the lithium-ion battery. Then the relationship between the discharge capacity and the starting temperature of the lithium-ion battery satisfies the linear regression equation, and the general formula of the linear regression equation is, for example: y=0.0022x+0.3485, R 2 =0.9898, where x is the Calvin temperature of the starting temperature, and y is the multiple of the discharge capacity of the lithium-ion battery at the preset starting temperature and the battery discharge capacity at 25°C, that is, the linear regression equation between the discharge capacity of the lithium-ion battery and the starting temperature: n=(0.0022x+0.3485)a, n is the discharge capacity of the lithium-ion battery at the preset starting temperature, R 2 is the linear correlation constant. Among them, the linear correlation constant is 0.9898, and the correlation constant is close to 1, indicating that the discharge capacity of lithium-ion batteries has a strong correlation with the starting temperature. That is, by increasing the starting temperature of lithium-ion battery charging, the kinetic characteristics of active materials can be improved, the polarization of materials can be reduced, and a higher discharge capacity can be achieved.

[0038] See also Figure 3 As shown, in one embodiment of the present invention, the positive electrode active material is, for example, LiMn a Fe 1-a PO4 and LiNi x Co y Mn 1-x-yO2 mixture, wherein 0.4≤a≤0.8, 0.5≤x≤0.95, 0.05≤y≤0.2, after the positive electrode active material is prepared into a positive electrode plate, it is assembled with a negative electrode plate, a separator and an electrolyte into a single lithium-ion battery, a battery module or a battery pack, and then charged using the above-mentioned charging method. Control the starting temperature, and charge the lithium-ion battery at different starting temperatures at the same preset rate, such as constant current charging to a preset upper limit voltage, and then charge at a constant voltage to the same preset cutoff current. When charging at different starting temperatures, record the proportion of constant voltage charging time in the entire charging process, and the CV time proportion and the starting temperature satisfy the linear regression equation, and the general formula of the linear regression equation is, for example: m=-0.694x+225.11, R 2 =0.9914, where x is the Calvin temperature of the starting temperature, m is the percentage of CV time in the entire charging process, R 2 is the linear correlation constant. The linear correlation constant is 0.9914, and the correlation constant is close to 1, indicating that the CV time has a strong correlation with the starting temperature. By increasing the starting temperature, the CV time gradually decreases, that is, by increasing the starting temperature of the lithium-ion battery charge, the charging time can be shortened and the phenomenon of high virtual voltage can be reduced.

[0039] Hereinafter, the present invention will be explained in more detail by citing examples, which should not be construed as limiting. Appropriate modifications may be made within the scope consistent with the gist of the present invention, all of which fall within the technical scope of the present invention.

[0040] Example 1

[0041] The positive electrode active material is LiMn 0.6 Fe 0.4 PO4 and LiNi 0.8 Co 0.1 Mn 0.1 O2 is mixed, and the theoretical discharge capacity of the positive electrode active material at 25°C is controlled to be 151 mAh / g. After the positive electrode active material is prepared into a positive electrode sheet, it is assembled into a lithium-ion battery with a graphite negative electrode sheet, a polypropylene film separator and an electrolyte.

[0042] The starting temperature of the lithium-ion battery charging is controlled to be 30°C, and the battery is charged to the preset upper limit voltage of 4.2V at a preset rate of 0.33C, and then charged to the preset cut-off current of 0.05C at a constant voltage. The temperature of the lithium-ion battery is lowered to 25°C, and then discharged at a constant current of 0.33C, and the discharge capacity and CV time ratio of the lithium-ion battery are recorded.

[0043] Example 2

[0044] The starting temperature was controlled to be 35° C., and the remaining steps were the same as in Example 1.

[0045] Example 3

[0046] The starting temperature was controlled to be 40° C., and the remaining steps were the same as in Example 1.

[0047] Example 4

[0048] The starting temperature was controlled to be 45°C, and the remaining steps were the same as in Example 1.

[0049] Comparative Example 1

[0050] The starting temperature was controlled to be 25°C, and the remaining steps were the same as in Example 1.

[0051] Table 1. Discharge capacity and CV time ratio of lithium ion batteries in Examples 1-4 and Comparative Example 1

[0052]

[0053] Please refer to Table 1 and Figure 4 As described above, by increasing the starting temperature of the lithium-ion battery charging, the discharge capacity of the lithium-ion battery gradually increases, and the discharge capacity and the preset temperature satisfy the linear regression equation n=0.3294x+52.582, R 2 =0.9898, where x is the Calvin temperature of the starting temperature, and n is the discharge capacity of the lithium-ion battery at the preset starting temperature. That is, the discharge capacity of the lithium-ion battery is positively correlated with the starting temperature of charging, and the discharge capacity of the lithium-ion battery can be increased by increasing the starting temperature of charging the lithium-ion battery. And the discharge capacity calculated based on the linear regression equation between the multiple of the battery's discharge capacity and the starting temperature is compared with the linear regression equation of the preset temperature, and the deviation of the coefficient of x from the constant is within ±1%, respectively, and the deviation is small. The CV time proportion satisfies the linear regression equation m=-0.694x+225.11, R 2 =0.9914, the CV time of lithium-ion batteries is negatively correlated with the charging start temperature, and the charging time can be shortened by increasing the charging start temperature of lithium-ion batteries. During the charging process of lithium-ion batteries, increasing the charging start temperature of lithium-ion batteries can simultaneously achieve the purpose of increasing the discharge capacity of lithium-ion batteries and shortening the charging time, thereby improving the applicability of lithium-ion batteries.

[0054] The present invention also provides an electronic device, the electronic device includes at least one of the above-mentioned lithium-ion batteries, and the lithium-ion battery is used to provide electrical energy. Among them, the electronic device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool. In one embodiment of the present invention, the vehicle is, for example, a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle. Spacecraft include airplanes, rockets, space shuttles and spacecrafts, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric airplane toys. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers. And the electronic device also includes a heating unit to control the starting temperature of the lithium-ion battery during charging, and control the temperature during charging to maintain at the starting temperature, wherein the heating unit is added in a manner including but not limited to a series of heating methods such as liquid cooling, water cooling, and air cooling.

[0055] In summary, the present invention proposes a charging method and application of a lithium-ion battery. By increasing the starting temperature of charging the lithium-ion battery, the kinetic characteristics of the active material in the lithium-ion battery can be improved, the polarization of the material can be reduced, the charging speed can be increased, and the safety problems caused by excessively high charging temperature can be prevented. By controlling the preset charging rate, the battery polarization and lithium precipitation phenomena can be reduced to ensure the cycle performance of the lithium-ion battery. By charging at a preset rate at high temperature and then charging at a constant voltage, the kinetic characteristics of the active material can be improved, the polarization of the material can be reduced, and a higher discharge capacity can be achieved. At the same time, the charging time can be shortened and the phenomenon of high virtual voltage can be reduced. That is, the purpose of increasing the discharge capacity of the lithium-ion battery and shortening the charging time can be achieved at the same time, and the applicability of the lithium-ion battery can be improved.

[0056] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept, such as the technical solution formed by replacing the above features with the technical features with similar functions disclosed in this application (but not limited to). In addition to the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described in detail here.

Claims

1. A method for charging a lithium-ion battery, characterized in that: At least: At the starting temperature, the lithium-ion battery is charged at a preset rate to a preset upper limit voltage, and the starting temperature is 30°C to 45°C; as well as The lithium-ion battery is charged at a constant voltage to a preset cut-off current.

2. The method for charging a lithium-ion battery according to claim 1, characterized in that: The starting temperature is 30°C to 40°C.

3. The method for charging a lithium-ion battery according to claim 1, characterized in that: The starting temperature is 33°C to 35°C.

4. The method for charging a lithium-ion battery according to claim 1, characterized in that: The preset magnification is, for example, 0.3C to 0.4C, and / or The preset cut-off current is 0.01C to 0.1C.

5. The method for charging a lithium-ion battery according to claim 4, characterized in that: The preset magnification is, for example, 0.33C, and / or, The preset cut-off current is 0.

05.

6. The method for charging a lithium-ion battery according to claim 1, characterized in that: The lithium-ion battery is charged at a preset rate constant current to a preset upper limit voltage.

7. The method for charging a lithium-ion battery according to claim 1, characterized in that: The lithium-ion battery is charged to a preset upper limit voltage at a preset rate variable current.

8. The method for charging a lithium-ion battery according to claim 1, characterized in that: The charging method further includes: after charging at a constant voltage to the preset cut-off current, lowering the temperature of the lithium-ion battery to 25° C., and then discharging at a constant current of 0.33C, and recording the discharge capacity of the lithium-ion battery.

9. The method for charging a lithium-ion battery according to claim 8, characterized in that: The discharge capacity and the starting temperature satisfy the linear regression equation: y=0.0022x+0.3485, R 2 =0.9898, where x is the Calvin temperature of the starting temperature, y is the multiple of the discharge capacity of the lithium-ion battery at the preset starting temperature and the discharge capacity of the lithium-ion battery at 25°C, R 2 is the linear correlation constant.

10. The method for charging a lithium-ion battery according to claim 1, characterized in that: The time proportion of the constant voltage charging in the charging process and the starting temperature satisfy the linear regression equation: m = -0.694x + 225.11, R2 = 0.9914, where x is the Calvin temperature of the starting temperature, m is the percentage value of the constant voltage charging time in the entire charging process, and R 2 is the linear correlation constant.

11. A lithium ion battery, characterized in that: The charging method according to any one of claims 1 to 10 is used for charging.

12. The lithium ion battery according to claim 11, characterized in that: The lithium-ion battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material comprises LiMn a Fe 1-a PO4、LiMn a Fe 1-a PO4 and LiNi x Co y Mn 1-x-y Mixture of O2 or LiMn a Fe 1-a PO4 and LiNi b Co c Al 1-b-c A mixture of O2 wherein 0.4≤a≤0.8, 0.5≤x≤0.95, 0.05≤y≤0.2, 0.5≤b≤0.95, 0.05≤c≤0.

2.

13. An electronic device, characterized in that: The invention comprises the lithium-ion battery according to any one of claims 11 to 12, and a heating unit.

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