Low-voltage and high-capacity lithium-rich manganese-based positive electrode active materials and their preparation and application

Abstract

The present invention belongs to the field of lithium-ion battery materials, and specifically relates to a low-voltage, high-capacity lithium-rich manganese-based positive electrode active material, its preparation, and application in lithium-ion batteries. The preparation method of the present invention comprises the following steps: subjecting a raw precursor to thermal transformation treatment to obtain a transformed precursor, and then calcining the transformed precursor with a lithium source in an oxygen-deficient atmosphere to obtain the raw precursor; the raw precursor is a low-cobalt or cobalt-free precursor, wherein the Co content is less than or equal to 10% of the total molar weight of nickel and manganese; the thermal transformation temperature is 450-650°C; and the oxygen content in the oxygen-deficient atmosphere is 1-15% by volume. The material of the present invention can still exhibit high capacity at low pressure, and not only that, but also has excellent long cycle life and voltage stability.

Description

Technical field:

[0001] The present invention relates to the field of lithium-ion new energy materials, and in particular to the field of lithium-rich manganese-based positive electrode materials. Background technology:

[0002] The development of electric vehicles and energy storage has expanded the application market for lithium-ion batteries, while also placing higher energy density and lower costs on them. Lithium-ion battery cathode materials are a key factor limiting the improvement of lithium-ion battery energy density and account for approximately 30-40% of the cost of lithium-ion batteries. Compared with currently commercialized cathode materials, the lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiTMO2 (TM = Ni, Co, and Mn, etc.) has a higher specific capacity (>250mAh / g) and lower cost (rich in Mn, low in Ni, or no Co), making it a promising candidate for the next generation of lithium-ion battery cathode materials.

[0003] The high capacity of lithium-rich manganese-based cathode materials comes from the redox of lattice oxygen at high voltage (~4.5V), and the oxidation of lattice oxygen will cause some irreversible oxygen loss. The release of oxygen will promote the reduction and migration of transition metals, induce structural deterioration, and ultimately cause poor material cycle performance and severe voltage decay. In addition, since lithium-rich manganese-based cathode materials continue to work at high voltage, it will cause severe decomposition of the electrolyte. The oxidation products of lattice oxygen will also react with the electrolyte, aggravating the interface side reactions and deteriorating the surface structure, which will cause cycle instability and make it difficult to select high-voltage-compatible electrolytes. Therefore, the commercial application of lithium-rich manganese-based cathode materials is limited. The study found that by cycling the lithium-rich manganese-based cathode materials in the low voltage range, the voltage decay problem of the materials can be effectively alleviated and the cycling stability of the materials can be improved. However, when the charging voltage is lowered, the capacity provided by the material from the anion redox reaction will be reduced, resulting in limited utilization of the high capacity of the lithium-rich manganese-based positive electrode material. Therefore, it is urgent to design a lithium-rich manganese-based positive electrode material that can circulate in a low voltage range and have high capacity characteristics, no voltage decay and excellent cycle stability. The successful development of this material will be of great significance to promoting the industrial application of lithium-rich manganese-based positive electrode materials.

[0004] In view of the problem that lithium-rich manganese-based materials have low capacity in the low voltage range and it is difficult to achieve a stable long cycle, the improvement scheme of the existing technology is still relatively scarce, mainly in the cobalt and other element doping and coating ideas. The incorporation of cobalt can be beneficial to the capacity to a certain extent. While promoting the anion redox reaction, it will also bring new problems such as cost and cycle loss. In addition, the existing technology also provides a few cobalt-free and low-cobalt solutions. For example, the Chinese patent document with publication number CN114853091A discloses a high-capacity lithium-rich manganese-based positive electrode material for low-voltage applications, and specifically provides a Zr doping scheme, which material can discharge a gram capacity of 185mAh / g under 2.5-4.45V, 0.1C charge and discharge conditions. For another example, the Chinese patent document with publication number CN117423820A discloses a coated modified lithium-rich manganese-based positive electrode material, and specifically discloses a solution for a carbon-coated lithium-rich manganese-based material.

[0005] In summary, the existing improvement solutions cannot truly solve the problems of low capacity, low discharge voltage, and unsatisfactory long-range cycle stability of lithium-rich manganese-based materials under low cobalt and low voltage. Summary of the invention:

[0006] In response to the problems of low-cobalt lithium-rich manganese-based materials such as low capacity at low voltage, unsatisfactory medium voltage and long-range cycle stability, the first purpose of the present invention is to provide a method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material (also referred to as lithium-rich manganese-based positive electrode active material in the present invention), aiming to obtain a low-cobalt / cobalt-free active material that still has excellent capacity at low voltage, medium voltage stability and long-range cycle stability.

[0007] The second object of the present invention is to provide a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material prepared by the preparation method and its application in lithium-ion batteries.

[0008] The third object of the present invention is to provide a lithium-ion battery comprising the low-voltage and high-capacity lithium-rich manganese-based positive electrode active material, and its positive electrode and positive electrode material.

[0009] Lithium-rich manganese-based cathode materials have low capacity at low voltages. To address this issue, most approaches involve doping and coating with foreign elements (such as Co). However, this approach still fails to effectively address issues such as low capacity at low voltages, mid-voltage drop, and unsatisfactory long-range cycling. Furthermore, it increases processing costs. To address this issue, the present invention provides the following improvements:

[0010] A method for preparing a low-pressure lithium-rich manganese-based positive electrode active material comprises subjecting an original precursor to thermal transformation treatment to obtain a transformed precursor, which is then calcined with a lithium source in an oxygen-deficient atmosphere to obtain the transformed precursor;

[0011] The original precursor is a low-cobalt or cobalt-free precursor, wherein the Co content is less than or equal to 10% of the total molar amount of nickel and manganese;

[0012] The temperature of thermal transition is 450~650℃;

[0013] The oxygen content in the oxygen-deficient atmosphere is 1-15v%.

[0014] The present invention innovatively subjects the original precursor to a thermal transformation treatment, and then adds lithium and calcines it in an oxygen-deficient atmosphere. This unexpectedly achieves synergy and improves the physical and chemical structure of the material, allowing it to unexpectedly exhibit excellent capacity at low voltage under low cobalt or cobalt-free conditions. Not only that, it also helps to improve its medium-voltage and long-range cycle stability.

[0015] In the present invention, the original precursor contains Mn x Ni 1-x-y Co y CO3 and / or Mn x Ni 1-x - y Co y At least one of (OH)2; said x is 0.5 to 0.6; said y is 0 to 0.08;

[0016] In the present invention, the original precursor can be prepared by a conventional co-precipitation method.

[0017] In the present invention, the original precursor is innovatively thermally transformed in advance and then calcined under oxygen-deficient conditions. This unexpectedly solves the problems of difficult capacity utilization, low medium pressure, and unsatisfactory long cycle caused by low cobalt and low pressure applications.

[0018] In the present invention, the atmosphere during the thermal transition stage is an oxygen-containing atmosphere or is carried out under negative pressure;

[0019] The oxygen-containing atmosphere is at least one of air, oxygen, and an oxygen-diluent gas mixture;

[0020] Preferably, the gas pressure during the thermal transition stage is below -0.1 atm;

[0021] Preferably, the temperature of thermal transition is 530-620°C, more preferably 550-600°C.

[0022] Preferably, the thermal transition time is more than 1 hour, preferably 4 to 8 hours.

[0023] Preferably, a pre-transformation treatment is performed before thermal transformation, wherein the pre-transformation temperature is 350-450°C and the pre-transformation time is 1-3 hours. Research has shown that this process can further control the physical and chemical characteristics of the material during the transformation process. Furthermore, combined with the subsequent sintering process, it can further improve the low-voltage, high-capacity, long-cycle, and voltage stability of the prepared material.

[0024] In the present invention, the transformed precursor and the lithium source can be mixed based on conventional solid-phase or liquid-phase mixing ideas, and then subsequent oxygen-deficient calcination is performed.

[0025] In the present invention, there is no particular requirement for the composition of the lithium source, and for example, the lithium source may include at least one of lithium nitrate, lithium carbonate, and lithium hydroxide;

[0026] In the present invention, the amount of lithium added is 0.95 to 1.05 times the theoretical molar amount. The amount of lithium added refers to the molar ratio of Li to the transition metal element in the transition precursor.

[0027] In the present invention, the starting raw materials for calcination further include a calcination aid, which is at least one of lithium nitrate and lithium tungstate.

[0028] Preferably, the calcination aid is 1 to 10% of the molar amount of the transformation precursor, and further 3 to 6%.

[0029] In the present invention, the oxygen-deficient atmosphere includes an oxygen-containing atmosphere and a diluent gas; the diluent gas includes nitrogen and / or argon inert gas;

[0030] Preferably, the calcination temperature is 800-950°C, further 840-910°C;

[0031] Preferably, the calcination holding time is 10 to 20 hours, further 10 to 15 hours;

[0032] Preferably, a pre-calcination treatment is further included before calcination, wherein the calcination temperature is 450-550° C. Preferably, the pre-calcination time is 2-6 hours.

[0033] More preferably, the oxygen content of the oxygen-depleted atmosphere in the pre-calcination stage is 10-15v%, and the oxygen content of the oxygen-depleted atmosphere in the calcination stage is 5-8v%. Studies have shown that this preferred process can further improve the physicochemical characteristics of the material, enabling it to exhibit better low-oxygen, high-capacity, and long-cycle performance.

[0034] The present invention also provides a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material prepared by the preparation method.

[0035] The preparation method of the present invention can give the prepared material special physical and chemical characteristics, and the material prepared by the preparation method can unexpectedly enable it to still exhibit excellent capacity, voltage and cycle stability under low-cobalt or cobalt-free and low-oxygen conditions.

[0036] The present invention also includes methods for preparing lithium-ion batteries, their positive electrodes, and positive electrode materials using the low-voltage, high-capacity, lithium-manganese-rich positive electrode active material using conventional means. For example, the low-voltage, high-capacity, lithium-manganese-rich positive electrode active material can be mixed with conventional binders and conductive agents to produce the positive electrode material. Furthermore, the positive electrode material can be composited onto a current collector to form a positive electrode. Furthermore, the positive electrode, negative electrode, and separator components can be assembled to produce a battery.

[0037] The present invention also provides a lithium-ion battery positive electrode, including a current collector and a positive electrode material composited on its surface, wherein the positive electrode material contains an active material, and the active material contains the low-voltage and high-capacity lithium-manganese-rich positive electrode active material obtained by the preparation method.

[0038] The present invention also provides a lithium-ion battery comprising a positive electrode comprising the low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to the present invention.

[0039] The battery and the positive electrode thereof of the present invention, except for containing the low-voltage and high-capacity lithium-rich manganese-based positive electrode active material, other components and structures can be conventional.

[0040] The present invention also provides a method for charging and discharging the lithium-ion battery, which is particularly suitable for the lithium-ion battery, wherein the lithium-ion battery is pre-activated at a first voltage and then cycled at a second voltage;

[0041] The first voltage is 2 to 4.7V or 2 to 4.8V;

[0042] The pre-activation ratio is 0.05-0.2C, and can further be 0.1-0.15C;

[0043] In the present invention, the number of charge and discharge cycles in the pre-activation stage is 1 to 5;

[0044] In the present invention, the second voltage is 2.5-4.4V, 2.5-4.45V or 2.5-4.5V.

[0045] Beneficial effects

[0046] The present invention innovatively subjects the original precursor to a thermal transformation treatment, then adds lithium and calcines it in an oxygen-deficient atmosphere. This can solve the problem of unsatisfactory capacity of lithium-rich manganese-based materials under low cobalt or cobalt-free conditions and low voltages, and helps to ensure high capacity, voltage stability and long-range cycling performance at low voltages.

[0047] Case studies have shown that the material described in this invention has an initial discharge capacity of 292.44 mAh / g at a 0.1C rate and a voltage range of 2-4.8V, and an initial cycle discharge capacity of 203 mAh / g at a 1C rate and a voltage range of 2-4.45V. Furthermore, the voltage remains stable and the capacity remains high after 200 cycles, demonstrating excellent electrochemical performance. Description of the drawings:

[0048] Figure 1 is the SEM image of Example 1;

[0049] Figure 2 is the XRD pattern of Example 1;

[0050] Figure 3 This is a charge and discharge curve diagram of Example 1;

[0051] Figure 4 This is the voltage decay diagram of Example 1;

[0052] Figure 5 This is the capacity decay diagram of Example 1;

[0053] Figure 6 This is the charge and discharge curve diagram of Example 2B group; Specific implementation method:

[0054] The following specific examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. In the examples of the present invention, unless otherwise specified, the means used are conventional means in the art, and the reagents used can be obtained through conventional commercial channels.

[0055] It should be noted that the technical solution of the present invention is applicable to the preparation of low-cobalt and cobalt-free lithium-rich manganese-based materials. The raw precursor can be prepared by conventional coprecipitation methods. For example, when preparing a carbonate precursor, sodium carbonate or the like can be used as a precipitant, and when preparing a hydroxide precursor, sodium hydroxide or the like can be used as a precipitant.

[0056] Example 1

[0057] Step 1: Weigh 2 g of the nickel manganese carbonate precursor 1 (original precursor, Mn:Ni molar ratio of 0.54:0.26) and pre-heat-transform it in air at 600°C and atmospheric pressure for 6 h to obtain a transformed precursor (oxidized precursor);

[0058] Step 2: The transformation precursor and the lithium source (lithium carbonate) are mixed to obtain a mixture, wherein the amount of lithium is the theoretical molar amount; the mixture is placed in a corundum ark and sintered in a muffle furnace. The mixture is heated from room temperature to 500°C at a heating rate of 3°C / min in an oxygen-Ar mixed gas (oxygen content is 15v%) (first stage calcination), and kept warm for 5h. The mixture is then heated to 850°C at the same heating rate (second stage calcination), kept warm for 12h, and then naturally cooled to room temperature to obtain a low-pressure, high-capacity lithium-rich manganese-based active material (active material, which can be recorded as the chemical formula Li 1.2 Mn 0.54 Ni 0.26 O2).

[0059] test:

[0060] The prepared low-voltage, high-capacity lithium-rich manganese-based active material is assembled into a button battery: the active material, carbon black conductive agent (SP) and binder polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 80:10:10, and then N-methylpyrrolidone (NMP) of 120% by weight of the mixture is added as a solvent. After mixing evenly, the positive electrode sheet is obtained by slurry preparation, coating, drying and rolling. Combined with lithium metal, a 2025 button half-cell is made. The first three cycles of charging use 0.1C constant current or constant voltage charging with a cut-off voltage of 4.7V, and discharging uses 0.1C constant current discharge with a cut-off voltage of 2V. Subsequently, 200 cycles are cycled at 1C in a voltage window of 2.5-4.45V.

[0061] Electrochemical tests show that the material has a voltage range of 2 to 4.7 V. Figure 3 The discharge capacity at a rate of 0.1C is 255.39 mAh / g. The cycle test is carried out in the voltage range of 2.5 to 4.45 V. The discharge capacity at a rate of 1C is 180.48 mAh / g, the capacity retention rate is 85.62%, and the voltage retention rate is 98.23%.

[0062] Example 2

[0063] Compared with Example 1, the only difference is that the type of original precursor is changed. The experimental groups are:

[0064] Group A: Replace the carbonate precursor in step 1 with a hydroxide precursor with the corresponding transition metal ratio;

[0065] Group B: The cobalt-free carbonate precursor in step 1 was replaced with a low-cobalt carbonate precursor, where Mn:Ni:Co=0.53:0.2:0.07

[0066] Group C: The ratio of Mn:Ni in the carbonate precursor in step 1 was adjusted to 3:1, and the total amount of Mn+Ni remained unchanged;

[0067] Tested according to the method of Example 1, the results were:

[0068] Group A: The discharge capacity at 0.1C was 252.18 mAh / g, the discharge capacity at 1C was 180.32 mAh / g, the capacity retention rate was 87.12%, and the voltage retention rate was 95.65%.

[0069] Group B: The discharge capacity at 0.1C was 262.44 mAh / g, the discharge capacity at 1C was 192.63 mAh / g, the capacity retention rate was 80.12%, and the voltage retention rate was 92.82%.

[0070] Group C: The discharge capacity at 0.1C was 258.43 mAh / g, the discharge capacity at 1C was 183.26 mAh / g, the capacity retention rate was 86.48%, and the voltage retention rate was 96.35%.

[0071] By comparing Examples 1 and 2, it can be seen that in the absence of cobalt or low cobalt conditions, the material of the present invention can still exhibit excellent low-voltage capacity and performance, for example, excellent low-voltage stability and voltage retention.

[0072] Example 3

[0073] Compared with Example 1, the only difference is that the transformation process of step 1 is changed. The experimental groups are:

[0074] Group A: In step 1, air was replaced with oxygen, and other operations and parameters were the same as in Example 1.

[0075] Group B: In step 1, a two-stage heat treatment was used, that is, the original precursor was first kept at 400°C for 2 h and then kept at 600°C for 4 h;

[0076] Group C: In step 1, the thermal transition process was processed at -0.01 MPa.

[0077] Tested according to the method of Example 1, the results were:

[0078] Group A: The discharge capacity at 0.1C is 265.87 mAh / g, the discharge capacity at 1C is 194.37 mAh / g, the capacity retention rate is 86.43%, and the voltage retention rate is 97.65%.

[0079] Group B: The discharge capacity at 0.1C was 266.23 mAh / g, the discharge capacity at 1C was 194.76 mAh / g, the capacity retention rate was 86.29%, and the voltage retention rate was 98.75%.

[0080] Group C: The discharge capacity at 0.1C was 263.53 mAh / g, the discharge capacity at 1C was 191.56 mAh / g, the capacity retention rate was 86.12%, and the voltage retention rate was 97.75%.

[0081] Example 4:

[0082] Compared with Example 1, the only difference is that the calcination process is changed. The experimental groups are:

[0083] Group A: In step 2, a calcination aid is further added, specifically LiNiO3, and the calcination aid accounts for 5% of the total amount of lithium salt.

[0084] Group B: The atmosphere in step 2 was adjusted to an oxygen-depleted atmosphere (oxygen / Ar mixed gas, wherein the oxygen content was 5v%);

[0085] Group C: In step 2, the atmosphere of the first calcination stage was a 15v% oxygen / Ar mixture, and the atmosphere of the second holding stage was a 5v% oxygen / Ar mixture; other operations and parameters were the same as in Example 1;

[0086] Tested according to the method of Example 1, the results were:

[0087] Group A: The discharge capacity at 0.1C was 265.23 mAh / g, the discharge capacity at 1C was 205.18 mAh / g, the capacity retention rate was 85.7%, and the voltage retention rate was 98.46%.

[0088] Group B: The discharge capacity at 0.1C was 260.73 mAh / g, the discharge capacity at 1C was 191.82 mAh / g, the capacity retention rate was 83.56%, and the voltage retention rate was 95.37%.

[0089] Group C: The discharge capacity at 0.1C was 279.53 mAh / g, the discharge capacity at 1C was 206.36 mAh / g, the capacity retention rate was 88.43%, and the voltage retention rate was 98.64%.

[0090] It can be seen from Examples 1 and 4B that calcination in an oxygen-deficient atmosphere helps to improve the performance of the material. On this basis, further use of additive-assisted calcination (Group A) and the preferred basin oxygen control technology (Group C) are expected to further improve the capacity and high-voltage performance of the material in the cobalt-free state.

[0091] Example 5:

[0092] Compared with Example 1, the only difference is that the charge and discharge regime in the test steps is changed. The experimental groups are:

[0093] Group A: The cut-off voltage for the first three cycles of charging was adjusted to 4.8V, and other test conditions remained unchanged.

[0094] Group B: After pre-activation, the cells were cycled for 200 cycles at 1C in a voltage window of 2.5-4.55V.

[0095] The result is:

[0096] Group A: The discharge capacity at 0.1C is 281.36 mAh / g, the discharge capacity at 1C is 206.72 mAh / g, the capacity retention rate is 78.62%, and the voltage retention rate is 92.72%.

[0097] Group B: The discharge capacity at 1C was 253.72 mAh / g, the capacity retention rate was 79.21%, and the voltage retention rate was 91.39%.

[0098] Example 6:

[0099] The only differences compared to Example 1 are that, in step 1, the temperature is controlled at 550°C and the thermal transition time is 8 hours; in step 2, an oxygen-Ar mixture is used with an oxygen content of 10% by volume; the first calcination temperature is 460°C and the time is 6 hours; and the second calcination temperature is 900°C and the time is 10 hours. All other operations, parameters, and tests are the same as in Example 1.

[0100] The test results are: the discharge capacity at a rate of 0.1C is 256.13mAh / g. When cycled within a voltage range of 2.5 to 4.45V, the discharge capacity at a rate of 1C is 182.12mAh / g, the capacity retention rate is 86.18%, and the voltage retention rate is 97.34%.

[0101] Comparative Example 1

[0102] Compared with Example 1, the only difference is that the transformation treatment in step 1 is not performed, and other operations, conditions and tests are the same as in Example 1.

[0103] The results are: the discharge capacity at 0.1C is 248.33 mAh / g, the discharge capacity at 1C is 175.56 mAh / g, the capacity retention rate is 76.12%, and the voltage retention rate is 90.75%.

[0104] Comparative Example 2

[0105] Compared with Example 1, the only difference is that the thermal transition temperature in step 1 is set to 400° C., and other operations, conditions and tests are the same as Example 1.

[0106] The results are: the discharge capacity at 0.1C is 249.73 mAh / g, the discharge capacity at 1C is 176.28 mAh / g, the capacity retention rate is 77.27%, and the voltage retention rate is 91.53%.

[0107] Comparative Example 3

[0108] Compared with Example 1, the only difference is that the atmosphere of the calcination process in step 2 is air, and other operations, conditions and tests are the same as those in Example 1.

[0109] The results are: the discharge capacity at 0.1C is 246.37 mAh / g, the discharge capacity at 1C is 173.63 mAh / g, the capacity retention rate is 75.12%, and the voltage retention rate is 85.75%.

[0110] Comparative Example 4

[0111] Compared with Example 1, the only difference is that the atmosphere of the calcination process in step 2 is Ar, and the other operations, conditions and tests are the same as those in Example 1.

[0112] The result is: no effective lithium-manganese-rich material was synthesized.

Claims

1. A method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material, characterized in that: The original precursor is subjected to thermal transformation treatment to obtain a transformed precursor, which is then calcined with a lithium source in an oxygen-deficient atmosphere to obtain; The original precursor is a low-cobalt or cobalt-free precursor, wherein the Co content is less than or equal to 10% of the total molar amount of nickel and manganese; The temperature of thermal transition is 450~650℃; The oxygen content in the oxygen-deficient atmosphere is 1-15v%.

2. The method for preparing a low-voltage, high-capacity lithium-rich manganese-based positive electrode active material according to claim 1, wherein: The original precursor contains Mn x Ni 1-x-y Co y CO3 and / or Mn x Ni 1-x-y Co y At least one of (OH)2; The x is 0.5-0.6; the y is 0-0.

08.

3. The method for preparing a low-voltage, high-capacity lithium-rich manganese-based positive electrode active material according to claim 2, wherein: The original precursor is prepared by a co-precipitation method.

4. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 1, wherein: The atmosphere during the thermal transformation stage is an oxygen-containing atmosphere or under negative pressure; The oxygen-containing atmosphere is at least one of air, oxygen, and an oxygen-diluent gas mixture.

5. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 4, wherein: The negative pressure is below -0.1 atm.

6. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 4, wherein: The thermal transition time is more than 1h.

7. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 6, wherein: The thermal transition time is 4~8h.

8. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 1, wherein: Before thermal transformation, pre-transformation treatment is carried out in advance, wherein the pre-transformation temperature is 350~450℃; the preheating transformation time is 1~3h.

9. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 1, wherein: The lithium source includes at least one of lithium nitrate, lithium carbonate, lithium hydroxide and lithium tungstate.

10. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 9, characterized in that: The amount of lithium added is 0.95 to 1.05 times the theoretical molar amount.

11. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 1, wherein: The starting raw materials for calcination also contain a calcination aid, and the calcination aid includes at least one of lithium nitrate and lithium tungstate.

12. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 11, wherein: The calcination aid is 1-10% of the molar amount of the transformation precursor.

13. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 1, wherein: The oxygen-deficient atmosphere includes an oxygen-containing atmosphere and a diluent gas; the diluent gas contains nitrogen and / or an inert gas.

14. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 1, wherein: The calcination temperature is 800~950℃.

15. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 1, wherein: The calcination holding time is 10~20h.

16. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 1, wherein: Before calcination, a pre-calcination treatment is also included, wherein the pre-calcination temperature is 450-550°C.

17. The method for preparing a low-voltage and high-capacity lithium-rich manganese-based positive electrode active material according to claim 16, wherein: The pre-calcination time is 2~6h.

18. A low-voltage, high-capacity lithium-rich manganese-based positive electrode active material prepared by the preparation method according to any one of claims 1 to 17.

19. A lithium-ion battery positive electrode, comprising a current collector and a positive electrode material composited on the surface thereof, wherein the positive electrode material comprises an active material, characterized in that: The active material comprises a low-voltage lithium-rich manganese-based positive electrode active material prepared by the preparation method according to any one of claims 1 to 17.

20. A lithium ion battery, characterized in that: The positive electrode according to claim 19 is included.

21. A method for charging and discharging a lithium-ion battery according to claim 20, characterized in that: pre-activating it at a first voltage and then charging and discharging it at a second voltage; The first voltage is 2~4.7V or 2~4.8V; The pre-activation ratio is 0.05-0.2C.

22. The method for charging and discharging a lithium-ion battery according to claim 21, wherein: The number of charge and discharge cycles in the pre-activation stage is 1 to 5.

23. The method for charging and discharging a lithium-ion battery according to claim 21, wherein: The second voltage is 2.5-4.4V, 2.5-4.45V, or 2.5-4.5V.

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