A lithium-rich manganese-based lithium-ion battery, its activation method, and an electric device

Abstract

The present invention provides a lithium-rich manganese-based lithium-ion battery, an activation method thereof, and an electric device. The activation method includes, during the first charging process, charging at a pre-charging current to a target voltage and then entering an activation stage; the activation stage includes at least two activation procedures, and each activation procedure includes charging at a constant current of an activation current to the target voltage and then charging at a constant voltage to a cut-off current, wherein the activation current < the pre-charging current; in the same activation procedure, the cut-off current < the activation current; in two adjacent activation procedures, the activation current in the subsequent activation procedure < the cut-off current in the previous activation procedure; the target voltage is 4.35V - 4.52V. By optimizing the activation method of the lithium-rich manganese-based lithium-ion battery, the present invention effectively regulates the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery, and solves the problem of low cost performance caused by incomplete capacity utilization of the existing lithium-rich manganese-based cathode material.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, in particular to a lithium-ion battery, and in particular to a lithium-manganese-rich lithium-ion battery and an activation method and an electric device thereof. Background Art

[0002] Lithium-ion batteries are widely used in portable electronic devices due to their high energy density, long cycle life and environmental friendliness, and have good application prospects in the field of large-scale power batteries. As the core of lithium-ion batteries, cathode materials have attracted extensive attention from researchers. The specific capacity of lithium-rich manganese-based layered oxide (xLi2MnO3·(1-x)LiMO2) is as high as 250mAh / g, which is considered to be an ideal choice for improving the energy density of lithium-ion batteries.

[0003] However, lithium-rich manganese-based materials have a high manganese content and contain more Li2MnO3 phases. Although this structure provides the material with a higher specific capacity, the lithium ion conductivity is low, resulting in severe voltage hysteresis in its electrochemical performance. The first charge requires a voltage of more than 4.5V to activate the Li2MnO3 phase and begin to release capacity.

[0004] In order to fully activate the Li2MnO3 phase, a high voltage of 4.8V is usually required in the prior art. However, during the charging process at high voltage, the material will continuously release oxygen, and at the same time, the material structure will undergo a phase change, resulting in an increase in the DCR (direct current resistance) of the lithium-rich manganese-based material and an increase in the voltage drop; and the electrolyte of the lithium-rich manganese-based material under high voltage is not perfect, the side reactions between the electrolyte and the material increase, the surface structure of the material is destroyed, and the safety is deteriorated, resulting in its inability to be applied on a large scale. When used at a low voltage of about 4.5V, it is difficult for the Li2MnO3 phase to fully exert its due performance, resulting in a low gram capacity of the material, resulting in a low cost-effectiveness of the low-voltage lithium-rich manganese-based material.

[0005] CN119481005A discloses a surface-modified lithium-rich manganese-based positive electrode material and a lithium-ion secondary battery. Under potential drive, the surface interface of the lithium-rich manganese-based positive electrode material particles converts active oxygen species, such as O2, O2 - , O - and oxygen polymer O n- The active oxygen is then absorbed and embedded into the lattice gaps, and then released when discharged to a low potential, returning to the lithium-rich manganese-based cathode material to form a reversible closed loop of active oxygen utilization. Although this technology effectively inhibits the oxidation and precipitation of lithium-free lattice oxygen in lithium-rich manganese-based cathode materials under high voltage, and improves the cycle stability and thermal stability of the material under high temperature and high voltage environments, it still needs to be used at a high voltage of 4.8V, and the side reactions between the lithium-rich manganese-based material and the electrolyte under high voltage cannot be avoided.

[0006] CN111987297A discloses a lithium-rich manganese-based cathode material with surface aluminum doping and lithium aluminum titanium phosphate coating, including a lithium-rich manganese-based cathode material and a coating layer of lithium aluminum titanium phosphate wrapped outside the lithium-rich manganese-based cathode material, and the surface of the lithium-rich manganese-based cathode material is doped with Al. In this invention, the electrolyte is prevented from directly contacting the cathode material through the coating layer, and at the same time, the fast ion conductor is beneficial to Li + transport to improve the rate performance; the coating layer and surface Al doping are formed by a one-step method to achieve the effect of stabilizing the lattice oxygen, so that the cycle performance of the material is improved. However, this method is a modification of the lithium-rich manganese-based material itself and is not universal.

[0007] CN117199300A discloses a lithium-rich manganese-based cathode material with a multi-layer composite structure and its preparation method. The lithium-rich manganese-based cathode material with a multi-layer composite structure is sequentially provided with a lithium-rich manganese-based oxide cathode material matrix, an inner coating layer, and an outer coating layer from the inside to the outside, and the molar ratio of the three is 1:(0.01-0.9):(0.01-0.1). The composition of the lithium-rich manganese-based oxide cathode material matrix is Li 1+x Mn a Ni b M c O2, the composition of the inner coating layer is Li 1-x Mn a M b O2, and the outer coating layer is one or more of oxides, fluorides, and phosphates of L, which solves the technical problem that the surface lattice oxygen of the lithium-rich manganese-based cathode material in the prior art is prone to irreversible removal under high voltage, but causes the reduction of the material capacity during high rate and cycling.

[0008] In the prior art, the lithium-rich manganese-based material is usually modified by doping and coating methods to enable it to be used at a high voltage of 4.8V. However, the problem of imperfect electrolyte matching under high voltage still cannot be solved, and it is not universal. Therefore, aiming at the characteristics of the lithium-rich manganese-based cathode material during use, it is of great significance to develop a universal activation method that enables the lithium-rich manganese-based cathode material to fully exert its capacity under low voltage and conventional electrolyte. Summary of the Invention

[0009] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a lithium-rich manganese-based lithium-ion battery, its activation method and application. The present invention optimizes the activation method of the lithium-rich manganese-based lithium-ion battery, changes the activation conditions of the Li2MnO3 phase, enables the Li2MnO3 phase to release a higher specific capacity under low voltage and conventional electrolyte, thereby regulating the charging specific capacity, and further effectively regulating the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery, and solving the problem of low cost performance caused by incomplete capacity utilization of the existing lithium-rich manganese-based cathode material.

[0010] To achieve the object of the present invention, the following technical solutions are adopted in the present invention:

[0011] In a first aspect, the present invention provides an activation method for a lithium-rich manganese-based lithium-ion battery. The activation method includes, during the first charging process, charging at a pre-charge current to a target voltage and then entering an activation stage; the activation stage includes at least two activation procedures, and each activation procedure includes charging at a constant current of an activation current to the target voltage and then charging at a constant voltage to a cut-off current, where the activation current < the pre-charge current; in the same activation procedure, the cut-off current < the activation current; in two adjacent activation procedures, the activation current in the subsequent activation procedure < the cut-off current in the previous activation procedure; and the target voltage is 4.35V - 4.52V.

[0012] By optimizing the activation method of the lithium-rich manganese-based lithium-ion battery, the present invention changes the activation conditions of the Li2MnO3 phase, enabling the Li2MnO3 phase to release a relatively high specific capacity at a low voltage, thereby regulating the charging specific capacity, and further effectively regulating the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery, and solving the problem of low cost performance caused by incomplete capacity utilization of the existing lithium-rich manganese-based cathode material. At the same time, by fully activating the Li2MnO3 phase at a low voltage, the present invention can also eliminate the ramp phenomenon during the battery cycle. The ramp phenomenon will cause lithium ions to continuously accumulate at the negative electrode, resulting in lithium deposition, which seriously affects the cycle life and safety performance of the lithium-rich manganese-based lithium-ion battery. In addition, since the Li2MnO3 phase can be fully activated at a low voltage in the present invention, the use of a high voltage is avoided, thereby avoiding side reactions between the electrolyte and the electrode material at a high voltage, and also being able to slow down the adverse phase transformation of the material structure, improving the safety of the application of the lithium-rich manganese-based material. The activation method provided by the present invention realizes the application of the lithium-rich manganese-based cathode material in a low voltage and a conventional electrolyte system, and has universality.

[0013] The "conventional electrolyte" referred to in the present invention means an electrolyte that has been maturely and widely used in lithium-ion batteries in the prior art.

[0014] Preferably, the rate of the pre-charge current is 0.1C - 0.5C.

[0015] Preferably, the rate of the activation current is 0.01C - 0.10C; the rate of the cut-off current is 0.001C - 0.050C.

[0016] Preferably, the activation method is carried out in a constant temperature environment of 20°C - 80°C.

[0017] Preferably, after charging at the pre-charge current to the target voltage and before entering the activation stage, a rest is also included.

[0018] Preferably, each activation process independently includes a hold.

[0019] Preferably, before the initial charging stage, the activation method further includes forming the lithium-rich manganese-based lithium-ion battery.

[0020] Preferably, during the forming process, a pressure of 1.5 Kg / cm 2 - 2.5 Kg / cm 2 is further applied to the lithium-rich manganese-based lithium-ion battery.

[0021] In a second aspect, the present invention provides a lithium-rich manganese-based lithium-ion battery, which is obtained by activating the lithium-rich manganese-based lithium-ion battery through the activation method as described in the first aspect.

[0022] Preferably, the positive electrode material of the lithium-rich manganese-based lithium-ion battery includes a lithium-rich manganese-based positive electrode material.

[0023] Preferably, the negative electrode material of the lithium-rich manganese-based lithium-ion battery includes a graphite negative electrode and / or a silicon-based negative electrode.

[0024] In a third aspect, the present invention provides an electric device, which includes the lithium-rich manganese-based lithium-ion battery as described in the second aspect.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) By optimizing the activation method of the lithium-rich manganese-based lithium-ion battery, the present invention changes the activation conditions of the Li2MnO3 phase, enabling the Li2MnO3 phase to release a higher specific capacity at a low voltage, thereby regulating the charging specific capacity, and further effectively regulating the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery, solving the problem of low cost performance caused by incomplete capacity utilization of the existing lithium-rich manganese-based positive electrode materials.

[0027] (2) By fully activating the Li2MnO3 phase at a low voltage, the present invention can also eliminate the slope phenomenon during the battery cycle. The slope phenomenon will cause lithium ions to continuously accumulate at the negative electrode, resulting in lithium deposition, which seriously affects the cycle life and safety performance of the lithium-rich manganese-based lithium-ion battery.

[0028] (3) By fully activating the Li2MnO3 phase at a low voltage, the present invention avoids the use of high voltage, thus avoiding the side reactions between the electrolyte and the electrode material at high voltage, and can also slow down the adverse phase transformation of the material structure, improving the safety of the application of the lithium-rich manganese-based material.

[0029] (4) The activation method provided by the present invention realizes the application of the lithium-rich manganese-based positive electrode material in a low voltage and conventional electrolyte system, and has universality. Description of the Drawings

[0030] Figure 1 are the first charge-discharge curves of the lithium-rich manganese-based lithium-ion battery after being activated by the activation methods provided in Example 1 and Comparative Example 1.

[0031] Figure 2 is the cycle curve of the lithium-rich manganese-based lithium-ion battery after being activated by the activation methods provided in Example 1 and Comparative Example 1.

[0032] Figure 3 are the first charge-discharge curves of the lithium-rich manganese-based lithium-ion battery after being activated by the activation method provided in Example 2. Detailed Embodiments

[0033] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the term "including" and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0035] In a specific embodiment, the present invention provides an activation method for a lithium-rich manganese-based lithium-ion battery. The activation method includes, during the first charging process, charging at a pre-charge current to a target voltage and then entering an activation stage; the activation stage includes at least two activation procedures, and each activation procedure includes charging at a constant current of an activation current to a target voltage and then charging at a constant voltage to a cut-off current, where the activation current < the pre-charge current; in the same activation procedure, the cut-off current < the activation current; in two adjacent activation procedures, the activation current in the subsequent activation procedure < the cut-off current in the previous activation procedure; the target voltage is 4.35V - 4.52V.

[0036] The activation method of the lithium-rich manganese-based lithium-ion battery provided by the present invention optimizes the constant voltage charging stage of the first charge of the lithium-rich manganese-based lithium-ion battery, sets at least two activation procedures, and in the same activation procedure, the cut-off current < activation current. In two adjacent activation procedures, the activation current in the latter activation procedure < the cut-off current in the previous activation procedure. Through at least two activations, at a low voltage of 4.35V - 4.52V, the Li2MnO3 phase is fully activated, and without the high voltage up to 4.80V in the conventional activation method, the Li2MnO3 phase can release a relatively high specific capacity, thereby regulating the charge specific capacity, and further effectively regulating the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery, solving the problem of low cost performance caused by incomplete capacity utilization of the existing lithium-rich manganese-based cathode material.

[0037] Meanwhile, the present invention fully activates the Li2MnO3 phase at a low voltage, and can also eliminate the slope phenomenon during the battery cycling process. The slope phenomenon will cause lithium ions to continuously accumulate at the negative electrode, resulting in lithium deposition, which seriously affects the cycle life and safety performance of the lithium-rich manganese-based lithium-ion battery. In addition, the present invention fully activates the Li2MnO3 phase at a low voltage, avoiding the use of high voltage, thus avoiding the side reaction between the electrolyte and the electrode material under high voltage, and can also slow down the adverse phase transformation of the material structure, improving the safety of the application of the lithium-rich manganese-based material.

[0038] In the present invention, the number of activation procedures in the activation stage is at least two, for example, it can be two, three, four or five, including but not limited to the listed values.

[0039] In the present invention, the target voltage is 4.35V - 4.52V, for example, it can be 4.35V, 4.38V, 4.40V, 4.42V, 4.44V, 4.46V, 4.48V, 4.50V, 4.51V or 4.52V, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0040] In the activation method provided by the present invention, the magnitude of the charging current is defined by the charging rate, where "C" refers to the theoretical specific capacity of the lithium-rich manganese-based cathode material, and those skilled in the art can determine it according to the theoretical capacity calculated from the specific composition of the actually used lithium-rich manganese-based cathode material.

[0041] In some embodiments, the rate of the pre-charge current is 0.1C - 0.5C, for example, it can be 0.1C, 0.2C, 0.3C, 0.4C or 0.5C, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0042] In some embodiments, the multiple of the activation current is 0.01C - 0.10C. For example, it can be 0.01C, 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, 0.09C or 0.10C, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0043] In the activation method provided by the present invention, the multiple of the cut-off current should not be too large, otherwise the Li2MnO3 phase cannot be fully activated and the sample cannot exhibit its due discharge specific capacity. Nor should the cut-off current be too small, otherwise overcharging will occur in the lithium-rich manganese-based cathode material, leading to performance deterioration.

[0044] In some embodiments, the multiple of the cut-off current is 0.001C - 0.050C. For example, it can be 0.001C, 0.003C, 0.005C, 0.007C, 0.009C, 0.010C, 0.020C, 0.030C, 0.040C or 0.050C, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0045] In some embodiments, the activation method is carried out in a constant temperature environment of 20°C - 80°C. For example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0046] In some embodiments, after charging to the target voltage with the pre-charge current and before entering the activation stage, it further includes a rest.

[0047] In some embodiments, each activation procedure independently includes a rest.

[0048] In the present invention, the rest time is not particularly limited. For the purpose of completely eliminating voltage polarization and resting until the voltage is stable and no longer changes, those skilled in the art can set it according to actual needs.

[0049] In some embodiments, before the initial charging stage of the activation method, it further includes forming the lithium-rich manganese-based lithium-ion battery.

[0050] In the present invention, the forming process of the lithium-rich manganese-based lithium-ion battery is a prior art and is not particularly limited.

[0051] In some embodiments, during the forming process, it further includes applying 1.5 Kg / cm 2 - 2.5 Kg / cm 2The pressure, for example, can be 1.5 Kg / cm 2 、1.6 Kg / cm 2 、1.7 Kg / cm 2 、1.8 Kg / cm 2 、1.9 Kg / cm 2 、2.0 Kg / cm 2 、2.1 Kg / cm 2 、2.2 Kg / cm 2 、2.3 Kg / cm 2 、2.4 Kg / cm 2 or 2.5 Kg / cm 2 , including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0052] In another specific embodiment, the present invention provides a lithium-rich manganese-based lithium-ion battery, which is obtained by activating the lithium-rich manganese-based lithium-ion battery through the activation method of the lithium-rich manganese-based lithium-ion battery as described in the above specific embodiment.

[0053] In some embodiments, the positive electrode material of the lithium-rich manganese-based lithium-ion battery includes a lithium-rich manganese-based positive electrode material.

[0054] In some embodiments, the negative electrode material of the lithium-rich manganese-based lithium-ion battery includes a graphite negative electrode and / or a silicon-based negative electrode.

[0055] The activation method of the lithium-rich manganese-based lithium-ion battery provided by the present invention has universality, so the composition of the lithium-rich manganese-based positive electrode material is not particularly limited. For example, the structural general formula of the lithium-rich manganese-based positive electrode material can be Li x Mn a Ni b Co c M d O 1+x , 1 < x ≤ 2, 0 < a + b + c + d < 1, and M is selected from any one or at least two combinations of Co, Al, Mo, Mg, Fe, Nb, W, Zr, Ti, or Cu. Typical but non-limiting combinations include the combination of Co and Al, the combination of Mo and Mg, the combination of Fe and Nb, the combination of W and Zr, or the combination of Ti and Cu.

[0056] In yet another specific embodiment, the present invention provides an electric device, which includes the lithium-rich manganese-based lithium-ion battery as described in the above another specific embodiment.

[0057] Example 1

[0058] This example provides a lithium-rich manganese-based lithium-ion battery and its activation method, including:

[0059] (1) Preparation of lithium-rich manganese-based lithium-ion batteries: Li 1.3 Ni 0.35 Mn 0.65 O 2.3 The positive electrode sheet was prepared by weighing and fully mixing with carbon black and PVDF in a mass ratio of 9:0.5:0.5. The positive electrode sheet was used as the positive electrode, a metal lithium sheet was used as the negative electrode, a polypropylene microporous membrane was used as the separator, and 1 mol / L LiPF6+EC / DMC / EMC was used as the electrolyte. The CR2430 stainless steel button battery was assembled in a glove box filled with argon and with a moisture content of less than 0.1 ppm to prepare a lithium-rich manganese-based lithium-ion battery.

[0060] (2) Activate the lithium-rich manganese-based lithium-ion battery prepared in step (1): place the lithium-rich manganese-based lithium-ion battery in a constant temperature environment of 25°C and let it stand for 8 hours to make the temperature of the lithium-rich manganese-based lithium-ion battery uniform. First, charge it to 4.52V at a constant current of 0.25C, then perform the first activation procedure: charge it to 4.52V at a constant current of 0.05C, and then charge it at a constant voltage until the cut-off current is 0.03C; then perform the second activation procedure: charge it to 4.52V at a constant current of 0.02C, and then charge it at a constant voltage until the cut-off current is 0.001C, thus completing the activation of the lithium-rich manganese-based lithium-ion battery.

[0061] The theoretical discharge specific capacity of the lithium-rich manganese-based positive electrode material used in this embodiment is 240 mAh / g, that is, the charging current in each stage is calculated according to C=240.

[0062] Example 2

[0063] This embodiment provides a lithium-rich manganese-based lithium-ion battery and an activation method thereof, comprising:

[0064] (1) Preparation of lithium-rich manganese-based lithium-ion battery: In addition to the lithium-rich manganese-based positive electrode material in Example 1, 1.3 Ni 0.35 Mn 0.65 O 2.3 Replace Li 1.5 Ni 0.25 Mn 0.75 O 2.5 Except for this, the rest are the same as in Example 1.

[0065] (2) Activate the lithium-rich manganese-based lithium-ion battery prepared in step (1): place the lithium-rich manganese-based lithium-ion battery in a constant temperature environment of 45°C and let it stand for 6 hours to make the temperature of the lithium-rich manganese-based lithium-ion battery uniform. First, charge it to 4.5V at a constant current of 0.1C, then perform the first activation procedure: charge it to 4.5V at a constant current of 0.04C, and then charge it at a constant voltage until the cut-off current is 0.02C; then perform the second activation procedure: charge it to 4.5V at a constant current of 0.01C, and then charge it at a constant voltage until the cut-off current is 0.002C, thus completing the activation of the lithium-rich manganese-based lithium-ion battery.

[0066] The theoretical discharge specific capacity of the lithium-rich manganese-based positive electrode material used in this embodiment is 270 mAh / g, that is, the charging current in each stage is calculated according to C=270.

[0067] Example 3

[0068] This embodiment provides a lithium-rich manganese-based lithium-ion battery and an activation method thereof, comprising:

[0069] (1) Preparation of lithium-rich manganese-based lithium-ion batteries: Li 1.1 Ni 0.45 Mn 0.55 O 2.1 The carbon black and PVDF were weighed and fully mixed in a mass ratio of 9:0.5:0.5 to prepare the positive electrode sheet; the graphite was weighed and fully mixed with the carbon black, CMC and SBR in a mass ratio of 92:0.8:5:2.2 to prepare the negative electrode sheet, the polypropylene microporous membrane was used as the separator, and 1 mol / L LiPF6+EC / DMC / EMC was used as the electrolyte. In a glove box filled with argon and with a moisture content of less than 0.1 ppm, a soft-pack lithium-manganese-rich based lithium-ion battery was assembled.

[0070] (2) Activating the lithium-rich manganese-based lithium-ion battery prepared in step (1): placing the lithium-rich manganese-based lithium-ion battery in a constant temperature environment of 80°C and leaving it to stand for 12 hours. After the standing period, applying 2 kg / cm 2 The pressure is used for formation. After formation, it is left to stand for 8 hours before activation. First, it is charged to 4.35V at a constant current of 0.5C. Next, the first activation procedure is performed: charging to 4.35V at a constant current of 0.1C, and then charging at a constant voltage until the cut-off current is 0.05C; then the second activation procedure is performed: charging to 4.35V at a constant current of 0.03C, and then charging at a constant voltage until the cut-off current is 0.015C; finally, the third activation procedure is performed: charging to 4.35V at a constant current of 0.01C, and then charging at a constant voltage until the cut-off current is 0.001C, completing the activation of the lithium-rich manganese-based lithium-ion battery.

[0071] Example 4

[0072] This embodiment provides a lithium-rich manganese-based lithium-ion battery and its activation method. Except that the target voltage in step (2) is increased from 4.52V to 4.55V, the rest are the same as in Embodiment 1.

[0073] Embodiment 5

[0074] This embodiment provides a lithium-rich manganese-based lithium-ion battery and its activation method, including:

[0075] (1) Prepare a lithium-rich manganese-based lithium-ion battery: the same as in Embodiment 1.

[0076] (2) Activate the lithium-rich manganese-based lithium-ion battery prepared in step (1): Except that in the first activation program, it is charged at a constant current of 0.2C to 4.52V and then charged at a constant voltage until the cut-off current is 0.15C; in the second activation program, it is charged at a constant current of 0.12C to 4.52V and then charged at a constant voltage until the cut-off current is 0.08C to complete the activation of the lithium-rich manganese-based lithium-ion battery, the rest are the same as in Embodiment 1.

[0077] Embodiment 6

[0078] This embodiment provides a lithium-rich manganese-based lithium-ion battery and its activation method, including:

[0079] (1) Prepare a lithium-rich manganese-based lithium-ion battery: the same as in Embodiment 1.

[0080] (2) Activate the lithium-rich manganese-based lithium-ion battery prepared in step (1): Except that in the first activation program, it is charged at a constant current of 0.2C to 4.52V and then charged at a constant voltage until the cut-off current is 0.15C; in the second activation program, it is charged at a constant current of 0.1C to 4.52V and then charged at a constant voltage until the cut-off current is 0.001C to complete the activation of the lithium-rich manganese-based lithium-ion battery, the rest are the same as in Embodiment 1.

[0081] Comparative Example 1

[0082] This comparative example provides a lithium-rich manganese-based lithium-ion battery and its activation method. Except that in step (2), it is charged at a constant current of 0.25C to 4.52V and then directly charged at a constant voltage until the cut-off current is 0.001C to complete the activation of the lithium-rich manganese-based lithium-ion battery, the rest are the same as in Embodiment 1.

[0083] Performance test:

[0084] Perform electrical performance tests on the lithium-rich manganese-based lithium-ion batteries activated by the activation methods provided in all the above embodiments and comparative examples:

[0085] Under the test conditions of a voltage of 2.3V - 4.52V and a rate of 0.1C, the initial charge specific capacity, initial discharge specific capacity, and first efficiency of the activated lithium-rich manganese-based lithium-ion battery were tested. The test results are shown in Table 1. The first charge-discharge curves of the activated lithium-rich manganese-based lithium-ion batteries in Example 1 and Comparative Example 1 are shown in Figure 1 , and the first charge-discharge curve of Example 2 is shown in Figure 3 .

[0086] Under the test conditions of a voltage of 2.3V - 4.52V and a rate of 0.5C, the charge-discharge cycle was carried out 100 times, and the cycle capacity retention rate was tested.

[0087] Among them, 50 th Cycle capacity retention rate = 50 th Discharge capacity / 1 st Discharge capacity, 100 th Cycle capacity retention rate = 100 th Discharge capacity / 1 st Discharge capacity.

[0088] The test results are shown in Table 1. The cycle curves of the lithium-rich manganese-based lithium-ion batteries activated by the activation methods provided in Example 1 and Comparative Example 1 are shown in Figure 2 .

[0089] Table 1

[0090]

[0091] According to the data results of Examples 1 to 3 and Comparative Example 1, it can be confirmed that by activating according to the activation method provided by the present invention, the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery is effectively improved, and the problem of low cost performance caused by incomplete capacity utilization of the existing lithium-rich manganese-based cathode material is solved.

[0092] As Figure 1 shown in the charge-discharge curve, it can be clearly seen that after Example 1 is activated according to the activation method provided by the present invention, under the same upper limit voltage condition, compared with Comparative Example 1, the charge specific capacity is increased by 21 mAh / g, the discharge specific capacity is increased by 28 mAh / g, and the first efficiency is increased by 3.7%.

[0093] As Figure 2For the cyclic curve mentioned above, the cyclic curve of the lithium-rich manganese-based lithium-ion battery activated by the activation method provided in Example 1 is very stable. However, for the lithium-rich manganese-based lithium-ion battery activated by the activation method provided in Comparative Example 1, a climbing phenomenon occurred during the cycling process, that is, the tendency of the discharge specific capacity to slowly increase and then decrease, which is attributed to the small activation of the Li2MnO3 phase during the cycling process. However, its discharge specific capacity is still far lower than that of Example 1, indicating that even after multiple subsequent charge and discharge cycles, Comparative Example 1 still cannot effectively activate the Li2MnO3 phase. Instead, the climbing phenomenon that occurred in Comparative Example 1 during the cycling process will cause lithium plating on the negative electrode, uneven deposition on the negative electrode surface to form lithium dendrites, which will thus pierce the separator and cause potential safety hazards, and will also cause the rapid decay of the capacity of the lithium-rich manganese-based lithium-ion battery in the later stage of cycling and the shortening of the battery life.

[0094] According to the data results of Example 1 and Example 4, it can be confirmed that the activation method provided by the present invention can fully activate the Li2MnO3 phase at a voltage of 4.52V. Continuing to increase the voltage to 4.55V will cause overcharge phenomenon in the lithium-rich manganese-based material. As shown in the data results of Example 4, although the charging capacity increases, the stability of the lithium-rich manganese-based cathode material decreases, and the capacity retention rate after 100 cycles drops to 94.8%.

[0095] According to the data results of Example 1, Example 5 and Example 6, it can be confirmed that if the activation is not carried out according to the charging rate provided by the present invention, the Li2MnO3 phase cannot be effectively activated.

[0096] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for activating a lithium-rich manganese-based lithium-ion battery, characterized in that, The activation method includes, during the first charging process, charging with a pre-charge current to a target voltage and then entering an activation stage; The activation stage includes at least two activation procedures. Each activation procedure includes charging at a constant current with an activation current to a target voltage and then charging at a constant voltage to a cut-off current, where the activation current is less than the pre-charge current; During the same activation procedure, the cut-off current is less than the activation current; During two adjacent activation procedures, the activation current in the subsequent activation procedure is less than the cut-off current in the previous activation procedure; The target voltage is 4.35V - 4.52V; The multiple of the cut-off current is 0.001C - 0.050C.

2. The activation method of the lithium-rich manganese-based lithium-ion battery according to claim 1, characterized in that, The multiple of the pre-charge current is 0.1C - 0.5C.

3. The activation method of the lithium-rich manganese-based lithium-ion battery according to claim 1, characterized in that, The multiple of the activation current is 0.01C - 0.10C.

4. The activation method of the lithium-rich manganese-based lithium-ion battery according to claim 1, characterized in that, The activation method is carried out in a constant temperature environment of 20°C - 80°C.

5. The activation method of the lithium-rich manganese-based lithium-ion battery according to claim 1, characterized in that, After charging with the pre-charge current to the target voltage and before entering the activation stage, it further includes a rest; And / or, each activation procedure independently includes a rest between them.

6. The activation method of the lithium-rich manganese-based lithium-ion battery according to claim 1, wherein, Before the initial charging stage, the activation method further includes forming the lithium-rich manganese-based lithium-ion battery.

7. The activation method of the lithium-rich manganese-based lithium-ion battery according to claim 6, characterized in that, During the formation process, it also includes applying a pressure of 1.5 Kg / cm 2 - 2.5 Kg / cm 2 to the lithium-rich manganese-based lithium-ion battery.

8. A lithium-rich manganese-based lithium-ion battery, characterized in that, The lithium-rich manganese-based lithium-ion battery is obtained by activating through the activation method of the lithium-rich manganese-based lithium-ion battery according to any one of claims 1 - 7.

9. The lithium-rich manganese-based lithium ion battery according to claim 8, characterized in that, The positive electrode material of the lithium-rich manganese-based lithium-ion battery includes a lithium-rich manganese-based positive electrode material; And / or, the negative electrode material of the lithium-rich manganese-based lithium-ion battery includes a graphite negative electrode and / or a silicon-based negative electrode.

10. An electric device, characterized in that, The electric device includes the lithium-rich manganese-based lithium-ion battery according to claim 8 or 9.

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