Lithium-rich manganese-based lithium ion battery, activation method thereof and electric device

Abstract

The invention provides a lithium-rich manganese-based lithium ion battery, an activation method thereof and an electric device, and the activation method comprises the following steps: in a first charging process, charging to a target voltage with a pre-charging current, and then entering an activation stage; the activation stage comprises at least two activation programs, the activation programs comprise constant-current charging to a target voltage with an activation current and then constant-voltage charging to a cut-off current, and the activation current is smaller than a pre-charging current; in the same activation program, the cut-off current is smaller than the activation current; in two adjacent activation programs, the activation current in the next activation program is smaller than the cut-off current in the previous activation program; the target voltage ranges from 4.35 V to 4.52 V. By optimizing the activation method of the lithium-rich manganese-based lithium ion battery, the specific discharge capacity of the lithium-rich manganese-based lithium ion battery is effectively regulated and controlled, and the problem of low cost performance caused by incomplete capacity exertion of the existing lithium-rich manganese-based positive electrode material is solved.

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 based 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 positive electrode material with surface aluminum doping and lithium titanium aluminum phosphate coating, comprising a lithium-rich manganese-based positive electrode material and a coating layer of lithium titanium aluminum phosphate wrapped outside the lithium-rich manganese-based positive electrode material, wherein the surface of the lithium-rich manganese-based positive electrode material is doped with Al. In the invention, the positive electrode material is prevented from directly contacting the electrolyte with the positive electrode material through the coating layer, and the fast ion conductor is conducive to Li + Transmission improves rate performance; by forming a coating layer and doping the surface with Al in a one-step method, the lattice oxygen is stabilized, thereby improving the cycle performance of the material. However, this method is a modification of the lithium-rich manganese-based material itself and is not universal.

[0007] CN117199300A discloses a multi-layer composite structure lithium-rich manganese-based positive electrode material and a preparation method thereof. The multi-layer composite structure lithium-rich manganese-based positive electrode material is sequentially provided with a lithium-rich manganese-based oxide positive electrode 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 positive electrode 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, the outer coating layer is one or more of the oxide, fluoride, and phosphate of L, which solves the technical problem in the prior art that the surface lattice oxygen of the lithium-rich manganese-based positive electrode material is prone to irreversible release under high pressure, but causes a decrease in material capacity during high rate and cycle processes.

[0008] In the prior art, lithium-rich manganese-based materials are usually modified by doping and coating to enable them to be used at a high voltage of 4.8V, but the problem of imperfect electrolyte matching at high voltage remains unsolved and is not universal. Therefore, it is of great significance to develop a universal activation method that enables lithium-rich manganese-based positive electrode materials to fully exert their capacity under low voltage and conventional electrolytes based on the characteristics of lithium-rich manganese-based positive electrode materials during use. Summary of the invention

[0009] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a lithium-rich manganese-based lithium-ion battery and its activation method and application. The present invention optimizes the activation method of the lithium-rich manganese-based lithium-ion battery and changes the activation conditions of the Li2MnO3 phase, so that the Li2MnO3 phase can release a higher specific capacity under low voltage and conventional electrolyte, thereby regulating the charge specific capacity, and then effectively regulating the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery, solving the problem of low cost performance of the existing lithium-rich manganese-based positive electrode materials due to incomplete capacity utilization.

[0010] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides an activation method for a lithium-rich manganese-based lithium-ion battery, the activation method comprising, during the first charging process, charging to a target voltage with a pre-charge current, and then entering an activation stage; the activation stage comprises at least two activation procedures, the activation procedure comprising charging to a target voltage with an activation current at a constant current, and then charging to a cut-off current at a constant voltage, wherein the activation current is less than the pre-charge current; in the same activation procedure, the cut-off current is less than the activation current; in two adjacent activation procedures, the activation current in the latter activation procedure is less than the cut-off current in the previous activation procedure; the target voltage is 4.35V-4.52V.

[0012] The present invention optimizes the activation method of the lithium-rich manganese-based lithium-ion battery, changes the activation conditions of the Li2MnO3 phase, and enables the Li2MnO3 phase to release a higher specific capacity at a low voltage, thereby regulating the charge specific capacity, and then effectively regulating the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery, solving the problem of low cost performance due to incomplete capacity utilization of the existing lithium-rich manganese-based positive electrode materials. At the same time, the present invention fully activates the Li2MnO3 phase at a low voltage, and can also eliminate the climbing phenomenon of the battery during the cycle process. The climbing phenomenon will cause lithium ions to accumulate continuously at the negative electrode, causing lithium precipitation, and seriously affecting the cycle life and safety performance of the lithium-rich manganese-based lithium-ion battery. In addition, the present invention can fully activate the Li2MnO3 phase at a low voltage, avoiding the use of high voltage, thereby avoiding the side reaction between the electrolyte and the electrode material at high voltage, and can also slow down the adverse phase change of the material structure, and improve the safety of the application of lithium-rich manganese-based materials. The activation method provided by the present invention realizes the application of lithium-rich manganese-based positive electrode materials in low voltage and conventional electrolyte systems, and has universal applicability.

[0013] The “conventional electrolyte” mentioned in the present invention refers to the electrolyte that has been mature and widely used in lithium-ion batteries in the prior art.

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

[0015] Preferably, the activation current ratio is 0.01C-0.10C; the cut-off current ratio 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 to the target voltage with the pre-charge current and before entering the activation phase, the process further includes a pause.

[0018] Preferably, each activation procedure independently includes a pause between them.

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

[0020] Preferably, the formation process also includes applying 1.5Kg / cm 2 -2.5Kg / cm 2 pressure.

[0021] In a second aspect, the present invention provides a lithium-rich manganese-based lithium ion battery, wherein the lithium-rich manganese-based lithium ion battery is activated by the activation method of the lithium-rich manganese-based lithium ion battery 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, comprising 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) The present invention optimizes the activation method of lithium-rich manganese-based lithium-ion batteries and changes the activation conditions of the Li2MnO3 phase, so that the Li2MnO3 phase can release a higher specific capacity at a low voltage, thereby regulating the charge specific capacity, and further effectively regulating the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery, thereby solving the problem of low cost performance of existing lithium-rich manganese-based positive electrode materials due to incomplete capacity utilization.

[0027] (2) The present invention fully activates the Li2MnO3 phase at low voltage and can also eliminate the climbing phenomenon of the battery during the cycle process. The climbing phenomenon will cause lithium ions to accumulate continuously at the negative electrode, causing lithium precipitation, which seriously affects the cycle life and safety performance of the lithium-rich manganese-based lithium-ion battery.

[0028] (3) The present invention fully activates the Li2MnO3 phase at low voltage, avoiding the use of high voltage, thereby avoiding the side reaction between the electrolyte and the electrode material under high voltage, and can also slow down the adverse phase change of the material structure, thereby improving the safety of the application of lithium-rich manganese-based materials.

[0029] (4) The activation method provided by the present invention realizes the application of lithium-rich manganese-based positive electrode materials in low-voltage, conventional electrolyte systems and has universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the first charge and discharge curve of the lithium-rich manganese-based lithium-ion battery after activation according to the activation method provided in Example 1 and Comparative Example 1.

[0031] Figure 2 It is a cycle curve of a lithium-rich manganese-based lithium-ion battery activated according to the activation method provided in Example 1 and Comparative Example 1.

[0032] Figure 3 This is the first charge and discharge curve of the lithium-rich manganese-based lithium-ion battery after activation according to the activation method provided in Example 2. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians 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 inclusions.

[0035] In a specific embodiment, the present invention provides an activation method for a lithium-rich manganese-based lithium-ion battery, the activation method comprising, during the first charging process, charging to a target voltage with a pre-charge current, and then entering an activation stage; the activation stage comprises at least two activation procedures, the activation procedure comprising charging to a target voltage with an activation current constant current, and then charging to a cut-off current with a constant voltage, wherein the activation current is less than the pre-charge current; in the same activation procedure, the cut-off current is less than the activation current; in two adjacent activation procedures, the activation current in the latter activation procedure is less than 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 charging 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 is less than the activation current, and in two adjacent activation procedures, the activation current in the latter activation procedure is less than the cut-off current in the previous activation procedure. Through at least two activations, the Li2MnO3 phase is fully activated at a low voltage of 4.35V-4.52V, and the Li2MnO3 phase can release a higher specific capacity without the need for a high voltage of up to 4.80V in a conventional activation method, thereby regulating the charging specific capacity, and then effectively regulating the discharge specific capacity of the lithium-rich manganese-based lithium ion battery, solving the problem of low cost performance of existing lithium-rich manganese-based positive electrode materials due to incomplete capacity utilization.

[0037] At the same time, the present invention fully activates the Li2MnO3 phase at low voltage, and can also eliminate the climbing phenomenon of the battery during the cycle process. The climbing phenomenon will cause lithium ions to accumulate continuously at the negative electrode, causing lithium precipitation, and seriously affecting 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 low voltage, avoids the use of high voltage, thereby avoiding the side reaction between the electrolyte and the electrode material at high voltage, and can also slow down the adverse phase change of the material structure, thereby improving the safety of the application of lithium-rich manganese-based materials.

[0038] In the present invention, the number of activation procedures in the activation phase is at least two times, for example, two times, three times, four times or five times, 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 also applicable.

[0040] In the activation method provided by the present invention, the size of the charging current is defined by the charging rate, wherein "C" refers to the theoretical specific capacity of the lithium-rich manganese-based positive electrode material, and those skilled in the art can determine the theoretical capacity calculated based on the specific composition of the lithium-rich manganese-based positive electrode material actually used.

[0041] In some embodiments, the pre-charge current ratio 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 also applicable.

[0042] In some embodiments, the activation current magnification 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 also applicable.

[0043] In the activation method provided by the present invention, the cut-off current ratio should not be too large, otherwise the Li2MnO3 phase cannot be fully activated and the sample cannot exert its expected discharge specific capacity. The cut-off current should not be too small, otherwise the lithium-rich manganese-based positive electrode material will be overcharged, resulting in performance deterioration.

[0044] In some embodiments, the cut-off current ratio 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 also applicable.

[0045] In some embodiments, the activation method is carried out in a constant temperature environment of 20°C-80°C, for example, 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 also applicable.

[0046] In some embodiments, after charging to the target voltage with the pre-charge current and before entering the activation phase, the process further includes pausing.

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

[0048] In the present invention, there is no particular limitation on the shelving time, and the purpose is to completely eliminate voltage polarization and to shelve 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, the activation method further comprises forming the lithium-rich manganese-based lithium-ion battery before the initial charging stage.

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

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

[0052] In another specific embodiment, the present invention provides a lithium-rich manganese-based lithium ion battery, which is activated by the activation method of the lithium-rich manganese-based lithium ion battery 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 is universal, and therefore the composition of the lithium-rich manganese-based positive electrode material is not particularly limited. For example, the general structural 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, M is selected from any one of Co, Al, Mo, Mg, Fe, Nb, W, Zr, Ti, or Cu, or a combination of at least two of them, typical but non-limiting combinations include a combination of Co and Al, a combination of Mo and Mg, a combination of Fe and Nb, a combination of W and Zr, or a 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 embodiment provides a lithium-rich manganese-based lithium-ion battery and an activation method thereof, comprising:

[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 an activation method thereof, which is the same as that of Embodiment 1 except that the target voltage of 4.52 V in step (2) is increased to 4.55 V.

[0073] Example 5

[0074] This embodiment provides a lithium-rich manganese-based lithium-ion battery and an activation method thereof, comprising:

[0075] (1) Preparation of lithium-rich manganese-based lithium-ion battery: same as Example 1.

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

[0077] Example 6

[0078] This embodiment provides a lithium-rich manganese-based lithium-ion battery and an activation method thereof, comprising:

[0079] (1) Preparation of lithium-rich manganese-based lithium-ion battery: same as Example 1.

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

[0081] Comparative Example 1

[0082] This comparative example provides a lithium-rich manganese-based lithium-ion battery and an activation method thereof, which is the same as Example 1 except that step (2) is to charge the battery to 4.52V at a constant current of 0.25C and then directly charge the battery at a constant voltage to a cutoff current of 0.001C to complete the activation of the lithium-rich manganese-based lithium-ion battery.

[0083] Performance Testing:

[0084] The electrical performance of the lithium-rich manganese-based lithium-ion battery activated by the activation methods provided in all the above embodiments and comparative examples was tested:

[0085] Under the test conditions of voltage of 2.3V-4.52V and 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 and discharge curves of the activated lithium-rich manganese-based lithium-ion battery in Example 1 and Comparative Example 1 are shown in Table 1. Figure 1 The first charge and discharge curve of Example 2 is shown in Figure 3 .

[0086] Under the test conditions of voltage of 2.3V-4.52V and rate of 0.5C, the charge and discharge cycles were repeated 100 times to test the cycle capacity retention rate.

[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 battery activated by the activation methods provided in Example 1 and Comparative Example 1 are shown in Table 1. 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 activation according to the activation method provided by the present invention effectively improves the discharge specific capacity of the lithium-rich manganese-based lithium-ion battery, and solves the problem of low cost performance of existing lithium-rich manganese-based positive electrode materials due to incomplete capacity utilization.

[0092] like Figure 1 From the charge and discharge curves shown, 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 conditions, 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] like Figure 2The cycle curve of the lithium-rich manganese-based lithium-ion battery activated by the activation method provided in Example 1 is very stable, while the lithium-rich manganese-based lithium-ion battery activated by the activation method provided in Comparative Example 1 shows a climbing phenomenon during the cycle, that is, the discharge specific capacity slowly rises and then falls, which is attributed to the small amount of activation of the Li2MnO3 phase during the cycle, but its discharge specific capacity is still far lower than the discharge specific capacity of Example 1, indicating that even after multiple subsequent charge and discharge, Comparative Example 1 still cannot effectively activate the Li2MnO3 phase. On the contrary, the climbing phenomenon of Comparative Example 1 during the cycle will lead to lithium precipitation at the negative electrode, uneven deposition on the surface of the negative electrode to form lithium dendrites, which will puncture the diaphragm and cause safety hazards, and will also cause the capacity of the lithium-rich manganese-based lithium ion to decay rapidly in the later stage of the cycle, shortening 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 the lithium-rich manganese-based material to be overcharged. As shown in the data results of Example 4, although the charging capacity is increased, the stability of the lithium-rich manganese-based positive electrode material decreases, and the capacity retention rate after 100 cycles decreases 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 performed according to the charging rate provided by the present invention, the Li2MnO3 phase cannot be effectively activated.

[0096] The applicant declares that the above is only a specific implementation mode 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 those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and 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 to a target voltage with a pre-charge current, and then entering an activation stage; The activation stage includes at least two activation procedures, wherein the activation procedure includes constant current charging to a target voltage with an activation current, and then constant voltage charging to a cutoff current, wherein the activation current is less than the pre-charge current; In the same activation procedure, the cut-off current is less than the activation current; In two adjacent activation procedures, the activation current in the latter activation procedure is less than the cut-off current in the former activation procedure; The target voltage is 4.35V-4.52V.

2. The activation method of the lithium-rich manganese-based lithium-ion battery according to claim 1, characterized in that: The pre-charge current ratio 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 activation current ratio is 0.01C-0.10C; The cut-off current ratio is 0.001C-0.050C.

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

6. The activation method of lithium-rich manganese-based lithium-ion battery according to claim 1, characterized in that: The activation method further comprises forming the lithium-rich manganese-based lithium ion battery before the initial charging stage.

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

8. A lithium-rich manganese-based lithium-ion battery, characterized in that: The lithium-rich manganese-based lithium-ion battery is activated by the activation method of the lithium-rich manganese-based lithium-ion battery according to any one of claims 1 to 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 comprises the lithium-rich manganese-based lithium ion battery as claimed in claim 8 or 9.

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