Lithium salt for lithium ion battery and preparation method of lithium salt

Abstract

The invention provides a lithium salt for a lithium ion battery and a preparation method of the lithium salt. The lithium salt for the lithium ion battery comprises lithium oxide and an impure-phase dopant, the impure-phase dopant comprises LiOH and / or Li2CO3, and the mass fraction of the impure-phase dopant is less than or equal to 1.5% on the basis of the mass of the lithium salt for the lithium ion battery. The lithium salt for the lithium ion battery provided by the invention comprises lithium oxide with the purity of more than or equal to 98.5% and a trace amount of impure-phase dopant, and has the advantages of low sintering temperature, easiness in discharging after sintering, small volume production difficulty, high purity and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, and particularly relates to a lithium salt for lithium-ion batteries and a preparation method thereof. Background Art

[0002] Due to characteristics such as high energy density and long cycle service life, lithium-ion batteries are widely used in various electronic products. However, with the rapid development of large mobile power sources such as electric vehicles, electric machinery, and drones, higher requirements for high energy and high power have been put forward.

[0003] Lithium salt is one of the main raw materials for preparing electrode materials in lithium batteries. Commonly used lithium salt raw materials include lithium oxide, lithium hydroxide, or lithium carbonate, etc. Among them, the lithium-rich lithium supplement additive uses lithium oxide alone as the lithium salt. Therefore, how to prepare lithium oxide from lithium hydroxide, lithium carbonate, lithium oxalate, etc. has become a major problem. Currently, most preparation methods are sintering methods using lithium hydroxide in a nitrogen or vacuum (vacuum degree below 1 kPa) environment. For example, CN103603028B provides a method for preparing lithium oxide or single crystal lithium hydroxide, which is carried out according to the following steps: (1) Put monohydrate lithium hydroxide in a crucible, and then heat it to 90 - 120 °C under a vacuum degree of 50 - 150 Pa and keep it warm for 2 - 3 h; (2) Heat the monohydrate lithium hydroxide from which free water has been removed to 200 - 250 °C under a vacuum degree of 50 - 150 Pa and keep it warm for 2 - 3 h, and then heat it up to 700 - 1000 °C at a rate of 5 - 15 °C / min and keep it warm for 4 - 10 h; (3) Under a vacuum degree of 50 - 150 Pa, cool the material in the crucible with the furnace to 70 - 100 °C, and then place the crucible in a glove box and cool it to room temperature to obtain lithium oxide or single crystal lithium hydroxide.

[0004] However, although lithium hydroxide can generate lithium oxide in a nitrogen or vacuum (vacuum degree below 1 kPa) environment, it has the following several disadvantages: 1) The lithium oxide sample sintered from lithium hydroxide in a nitrogen or vacuum (vacuum degree below 1 kPa) environment adheres to the crucible, and it is not easy to separate the crucible from the sample; 2) The lithium oxide sample sintered from lithium hydroxide in a nitrogen or vacuum (vacuum degree below 1 kPa) environment has the characteristics of high hardness and is not easy to break, so the mass production is difficult; 3) The phenomenon that the lithium oxide sample sintered from lithium hydroxide in a nitrogen or vacuum (vacuum degree below 1 kPa) environment corrodes the crucible is very serious, resulting in low purity of the lithium oxide; 4) When sintering a lithium oxide sample from lithium hydroxide in a vacuum (vacuum degree below 1 kPa) environment, a large amount of water vapor will be generated when lithium hydroxide dehydrates during the formation of lithium oxide. At this time, the vacuum pump will suck in water vapor, greatly shortening its service life.

[0005] Therefore, how to improve the purity and breakability of lithium oxide and reduce its hardness is the current research difficulty. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a lithium salt for lithium-ion batteries and a preparation method thereof. The lithium salt for lithium-ion batteries provided by the present invention includes lithium oxide with a purity of ≥98.5%, and trace amounts of heterophase dopants. This lithium salt for lithium-ion batteries has the advantages of low sintering temperature, easy discharging after sintering, low mass production difficulty, and high purity.

[0007] To achieve the purpose of this invention, the following technical solutions are adopted:

[0008] In the first aspect, the invention provides a lithium salt for lithium-ion batteries, and the lithium salt for lithium-ion batteries includes lithium oxide and heterophase dopants;

[0009] The heterophase dopants include LiOH and / or Li 2 CO 3 , and based on the mass of the lithium salt for lithium-ion batteries, the mass fraction of the heterophase dopants is ≤1.5%.

[0010] The lithium salt for lithium-ion batteries provided by the present invention includes lithium oxide with a purity of ≥98.5%, and trace amounts of heterophase dopants. This lithium salt for lithium-ion batteries has the advantages of low sintering temperature, easy discharging after sintering, low mass production difficulty, and high purity.

[0011] In the present invention, trace amounts of heterophase dopants are beneficial to more uniform diffusion between the lithium salt and the precursor reactants during the material synthesis reaction, and the reaction is more complete; if the content is too much, it increases the decomposition and reaction difficulty of the lithium salt, reduces the reaction activity, the purity of the obtained synthetic material is low, and the residual alkali is high.

[0012] Preferably, based on the mass of the lithium salt for lithium-ion batteries, the mass fraction of the lithium oxide is ≥98.5%, such as 98.5%, 99%, or 99.5%, etc.

[0013] In the second aspect, the present invention provides a preparation method of the lithium salt for lithium-ion batteries as described in the first aspect, and the preparation method includes the following steps:

[0014] (1) In an oxygen-containing atmosphere, at least one lithium source is sintered to obtain a sintered product;

[0015] (2) In an oxygen-containing atmosphere, the sintered product is post-treated to obtain the lithium salt for lithium-ion batteries.

[0016] The present invention proposes a method for preparing lithium oxide in an oxygen-containing atmosphere. This method not only has a simple process and low cost, but also is easy to separate the crucible and the sample, and has little corrosion to the crucible.

[0017] It should be noted that, in the oxygen-containing environment of the present invention, the preparation can be achieved by normal exhaust under normal pressure. The water vapor and the oxygen gas flow are effectively evaporated and discharged together, and will not adhere to form a crystalline capping on the upper layer of the material. It is possible to directly discharge the material without sticking to the crucible, and a higher purity of lithium oxide can be achieved under the same temperature and time conditions.

[0018] As a preferred technical solution of the present invention, in the oxygen-containing atmosphere in step (1), the mass concentration of oxygen ≥ 99.5%, for example, it can be 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 100%, etc., preferably ≥ 99.9%.

[0019] In the present invention, if the mass concentration of oxygen is too low, the sintered sample will adhere to the crucible and is not easy to separate.

[0020] Preferably, in the oxygen-containing atmosphere in step (1), the flow rate of oxygen is 1 - 5 L / min, for example, it can be 1 L / min, 2 L / min, 3 L / min, 4 L / min or 5 L / min, etc.

[0021] In the present invention, if the flow rate of oxygen in the oxygen-containing atmosphere is too small, the gas flow is not smooth, the water vapor cannot be effectively discharged, and the sample adheres to the crucible seriously; if the flow rate of oxygen in the oxygen-containing atmosphere is too large, the material reaction is not sufficient, and the gas with a large flow rate will blow the powder to cause splashing, polluting the equipment and being not conducive to industrialization.

[0022] As a preferred technical solution of the present invention, the lithium source in step (1) includes any one or a combination of at least two of lithium hydroxide, lithium carbonate or lithium oxalate, preferably LiOH and Li 2 CO 3 .

[0023] Preferably, the mass ratio of the LiOH and Li 2 CO 3 is (80 - 98):(2 - 20), where the selection range of LiOH "80 - 98" can be, for example, 80, 85, 90, 95 or 98, etc., and the selection range of Li 2 CO 3 "2 - 20" can be, for example, 2, 5, 10, 15 or 20, etc.

[0024] In the present invention, if the mass ratio of LiOH and Li 2 CO 3 is too large, there is more water vapor, and the exhaust difficulty is large, which is likely to cause adhesion. If the mass ratio of LiOH and Li 2 CO 3 is too small, the decomposition of Li 2 CO 3 is difficult to proceed, and the product purity is low.

[0025] Preferably, the particle size D50 of the lithium source is 1-10 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc., and preferably 1-3 μm.

[0026] As a preferred technical solution of the present invention, the sintering method in step (1) is single-stage sintering, and the heating rate of the single-stage sintering is 1-20 °C / min, for example, it can be 1 °C / min, 3 °C / min, 5 °C / min, 7 °C / min, 9 °C / min, 11 °C / min, 13 °C / min, 15 °C / min, 17 °C / min or 19 °C / min, etc.

[0027] Preferably, the temperature of the single-stage sintering is 700-1100 °C, for example, it can be 700 °C, 800 °C, 900 °C, 1000 °C or 1100 °C, etc.

[0028] Preferably, the time of the single-stage sintering is 180-720 min, for example, it can be 180 min, 360 min, 420 min, 480 min, 540 min, 600 min, 660 min or 720 min, etc.

[0029] As a preferred technical solution of the present invention, the sintering method in step (1) is multi-stage sintering, and the multi-stage sintering includes first-stage sintering, second-stage sintering and third-stage sintering carried out in sequence.

[0030] In the present invention, the lithium source is subjected to first-stage sintering, second-stage sintering and third-stage sintering in sequence. The decomposition and reaction processes of the raw materials at different stages are more sufficient, which is more conducive to smoothly discharging water vapor and sintering and purifying at a high temperature stage. Among them, the first-stage sintering is a rapid heating stage, which can improve the production efficiency to reach the material reaction temperature; the second-stage sintering is a decomposition reaction stage, and slow heating and decomposition are conducive to the full reaction of the material; the third-stage sintering is a high-temperature purification stage, which is the key to obtaining high-purity lithium oxide and can ensure the high quality of the material.

[0031] Preferably, the heating rate of the first-stage sintering is 1-20 °C / min, for example, it can be 1 °C / min, 3 °C / min, 5 °C / min, 7 °C / min, 9 °C / min, 11 °C / min, 13 °C / min, 15 °C / min, 17 °C / min or 19 °C / min, etc., and preferably 2-10 °C / min.

[0032] Preferably, the temperature of the first-stage sintering is 400-500 °C, for example, it can be 400 °C, 420 °C, 440 °C, 460 °C, 480 °C or 500 °C, etc.

[0033] Preferably, the heat preservation time of the primary sintering is 30 - 120 min, for example, it can be 30 min, 60 min, 90 min or 120 min, etc.

[0034] As a preferred technical solution of the present invention, the heating rate of the secondary sintering is 0.2 - 2 °C / min, for example, it can be 0.2 °C, 0.5 °C, 0.7 °C, 1 °C, 1.2 °C, 1.4 °C, 1.6 °C, 1.8 °C or 2 °C, etc., and preferably 0.5 - 1 °C / min.

[0035] In the present invention, a lower heating rate is adopted for the secondary sintering to reach the sintering temperature, which can completely decompose the raw materials and fully remove the water vapor. If the heating rate of the secondary sintering is too high, the material will decompose. This process is a stage of a large amount of water vapor generation. If the heating is too fast, when the water vapor has not been completely discharged, high-temperature purification will occur, and the surface water vapor will condense again, resulting in serious powder adhesion.

[0036] Preferably, the temperature of the secondary sintering is 550 - 600 °C, for example, it can be 550 °C, 560 °C, 570 °C, 580 °C, 590 °C or 600 °C, etc.

[0037] Preferably, the heat preservation time of the secondary sintering is 30 - 120 min, for example, it can be 30 min, 60 min, 90 min or 120 min, etc.

[0038] As a preferred technical solution of the present invention, the heating rate of the tertiary sintering is 1 - 20 °C / min, for example, it can be 1 °C / min, 3 °C / min, 5 °C / min, 7 °C / min, 9 °C / min, 11 °C / min, 13 °C / min, 15 °C / min, 17 °C / min or 19 °C / min, etc., and preferably 2 - 10 °C / min.

[0039] Preferably, the temperature of the tertiary sintering is 700 - 1100 °C, for example, it can be 700 °C, 800 °C, 900 °C, 1000 °C or 1100 °C, etc.

[0040] Preferably, the heat preservation time of the tertiary sintering is 180 - 720 min, for example, it can be 180 min, 360 min, 420 min, 480 min, 540 min, 600 min, 660 min or 720 min, etc., and preferably 300 - 600 min.

[0041] As a preferred technical solution of the present invention, in the oxygen-containing atmosphere described in step (2), the mass concentration of oxygen ≥ 99.5%, for example, it can be 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 100%, etc.

[0042] Preferably, the post-treatment steps in step (2) include cooling and crushing.

[0043] It should be noted that this cooling process is natural cooling.

[0044] Preferably, after cooling, the temperature of the sintered product is 30 - 100 °C, for example, it can be 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C or 100 °C, etc.

[0045] Preferably, the crushing method includes any one of ball milling, roll crushing, mechanical pulverization or jet milling, and mechanical crushing is preferred.

[0046] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0047] (1) In an oxygen atmosphere with an oxygen mass concentration ≥ 99.5%, at least one lithium source is heated from room temperature to 400 - 500 °C at a heating rate of 1 - 20 °C / min and held for 30 - 120 min for primary sintering; then it is continuously heated to 550 - 600 °C at a heating rate of 0.2 - 2 °C / min and held for 30 - 120 min for secondary sintering; then it is continuously heated to 700 - 1100 °C at a heating rate of 1 - 20 °C / min and held for 180 - 720 min for tertiary sintering to obtain a sintered product;

[0048] (2) In an oxygen atmosphere with an oxygen mass concentration ≥ 99.5%, the sintered product is cooled to 30 - 100 °C and crushed to a particle size D50 of 1 - 10 μm to obtain the lithium salt for lithium-ion batteries.

[0049] The numerical ranges described in the present invention not only include the above-listed point values, but also any point values between the above numerical ranges not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) The lithium salt for lithium-ion batteries provided by the present invention includes lithium oxide with a purity ≥ 98.5% and trace amounts of heterophase dopants. This lithium salt for lithium-ion batteries has the advantages of low sintering temperature, easy discharging after sintering, low mass production difficulty and high purity.

[0052] (2) The present invention proposes a method for preparing lithium oxide in an oxygen-containing atmosphere. This method not only has a simple process and low cost, but also is easy to separate the crucible from the sample and has little corrosion to the crucible. Description of the Drawings

[0053] Figure 1 XRD pattern of the lithium salt for lithium-ion batteries prepared in Example 1 of the present invention. Detailed implementation manners

[0054] The technical solution of the present invention will be further described below through specific implementation manners. 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.

[0055] In the following embodiments, room temperature refers to 25 °C.

[0056] Example 1

[0057] This embodiment provides a lithium salt for lithium-ion batteries. The lithium salt for lithium-ion batteries includes lithium oxide with a mass fraction of 99.5%, and the hetero-phase dopant is LiOH.

[0058] This embodiment provides a preparation method of a lithium salt for lithium-ion batteries. The preparation method includes the following steps:

[0059] (1) Load 1 kg of lithium hydroxide (particle size D50 is 3 μm) into a corundum crucible and place it in a tubular furnace. Continuously introduce oxygen into the tubular furnace at an oxygen flow rate of 3 L / min. When the mass concentration of oxygen in the tubular furnace is 99.6%, heat it from room temperature to 500 °C at a heating rate of 10 °C / min and keep it warm for 120 min for the first-stage sintering; then continue to heat it to 550 °C at a heating rate of 1 °C / min and keep it warm for 120 min for the second-stage sintering; then continue to heat it to 800 °C at a heating rate of 10 °C / min and keep it warm for 180 min for the third-stage sintering to obtain a sintered product;

[0060] (2) Continue to introduce oxygen at 3 L / min. After the sintered product is naturally cooled to 100 °C, take it out and crush it with a mechanical crusher to obtain a lithium salt for lithium-ion batteries with a particle size D50 of 20.35 μm.

[0061] Figure 1 The XRD pattern of the lithium salt for lithium-ion batteries prepared in this embodiment is shown. It can be seen from the figure that all the phases are peaks corresponding to Li 2 O, and there is almost no remaining of other hetero-phases.

[0062] Example 2

[0063] The difference between this example and Example 1 is that in step (1), the temperature is raised to 400 °C at a heating rate of 20 °C / min at room temperature and held for 90 min for primary sintering; then the temperature is raised to 600 °C at a heating rate of 0.5 °C / min and held for 90 min for secondary sintering; then the temperature is raised to 700 °C at a heating rate of 1 °C / min and held for 300 min for tertiary sintering.

[0064] The remaining preparation methods and parameters are the same as those in Example 1.

[0065] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.5%, and the heterophase dopant is LiOH.

[0066] Example 3

[0067] The difference between this example and Example 1 is that in step (1), the temperature is raised to 450 °C at a heating rate of 5 °C / min at room temperature and held for 60 min for primary sintering; then the temperature is raised to 600 °C at a heating rate of 2 °C / min and held for 30 min for secondary sintering; then the temperature is raised to 800 °C at a heating rate of 10 °C / min and held for 240 min for tertiary sintering.

[0068] The remaining preparation methods and parameters are the same as those in Example 1.

[0069] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.4%, and the heterophase dopant is LiOH.

[0070] Example 4

[0071] The difference between this example and Example 1 is that in step (1), 1 kg of lithium carbonate (particle size D50 is 5 μm) is loaded into a corundum crucible and placed in a box furnace. The temperature is raised to 400 °C at a heating rate of 1 °C / min at room temperature and held for 30 min for primary sintering; then the temperature is raised to 600 °C at a heating rate of 2 °C / min and held for 30 min for secondary sintering; then the temperature is raised to 1100 °C at a heating rate of 20 °C / min and held for 180 min for tertiary sintering.

[0072] The remaining preparation methods and parameters are the same as those in Example 1.

[0073] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.4%, and the heterophase dopants are LiOH and Li 2 CO 3 .

[0074] Example 5

[0075] The difference between this embodiment and Embodiment 1 is that in step (1), 1 kg of lithium oxalate (with a particle size D50 of 1 μm) is loaded into a corundum crucible and placed in a box furnace. It is heated from room temperature to 480 °C at a heating rate of 3 °C / min and held for 75 min for primary sintering; then it is heated to 550 °C at a heating rate of 0.8 °C / min and held for 60 min for secondary sintering; then it is heated to 1100 °C at a heating rate of 6 °C / min and held for 180 min for tertiary sintering.

[0076] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0077] The lithium salt for lithium-ion batteries prepared in this embodiment is high-purity lithium oxide, with a mass fraction of 99.4%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0078] Embodiment 6

[0079] The difference between this embodiment and Embodiment 1 is that in step (1), 900 g of lithium hydroxide and 100 g of lithium carbonate (the mass ratio of lithium hydroxide to lithium carbonate is 90:10) are stirred and dispersed for 3 min at a speed of 600 rpm using a mixing blender to obtain a mixture. The mixture is heated from room temperature to 500 °C at a heating rate of 10 °C / min and held for 80 min for primary sintering; then it is heated to 600 °C at a heating rate of 0.2 °C / min and held for 45 min for secondary sintering; then it is heated to 900 °C at a heating rate of 10 °C / min and held for 180 min for tertiary sintering.

[0080] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0081] The lithium salt for lithium-ion batteries prepared in this embodiment is high-purity lithium oxide, with a mass fraction of 99.8%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0082] Embodiment 7

[0083] The difference between this embodiment and Embodiment 1 is that in step (1), 900 g of lithium hydroxide and 100 g of lithium oxalate (the mass ratio of lithium hydroxide to lithium oxalate is 90:10) are stirred and dispersed for 3 min at a rotation speed of 600 rpm by using a mixing blender to obtain a mixed material. The mixed material is heated to 420 °C at a heating rate of 15 °C / min at room temperature and kept warm for 100 min for primary sintering; then it is heated to 580 °C at a heating rate of 1.5 °C / min and kept warm for 100 min for secondary sintering; then it is heated to 1000 °C at a heating rate of 10 °C / min and kept warm for 180 min for tertiary sintering.

[0084] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0085] The lithium salt for lithium-ion batteries prepared in this embodiment is high-purity lithium oxide, and its mass fraction is 99.5%, and the heterophase dopants are LiOH and Li 2 CO 3 .

[0086] Embodiment 8

[0087] The difference between this embodiment and Embodiment 1 is that in step (1), 900 g of lithium carbonate and 100 g of lithium oxalate (the mass ratio of lithium hydroxide to lithium oxalate is 90:10) are stirred and dispersed for 3 min at a rotation speed of 600 rpm by using a mixing blender to obtain a mixed material. The mixed material is heated to 430 °C at a heating rate of 12 °C / min at room temperature and kept warm for 90 min for primary sintering; then it is heated to 530 °C at a heating rate of 2 °C / min and kept warm for 90 min for secondary sintering; then it is heated to 1000 °C at a heating rate of 10 °C / min and kept warm for 180 min for tertiary sintering.

[0088] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0089] The lithium salt for lithium-ion batteries prepared in this embodiment is high-purity lithium oxide, and its mass fraction is 99.4%, and the heterophase dopants are LiOH and Li 2 CO 3 .

[0090] Embodiment 9

[0091] The difference between this example and Example 1 is that in step (1), 800 g of lithium hydroxide, 100 g of lithium carbonate, and 100 g of lithium oxalate (the mass ratio of lithium hydroxide, lithium carbonate, and lithium oxalate is 80:10:10) are stirred and dispersed for 3 min to obtain a mixed material. The mixed material is heated to 500 °C at a heating rate of 10 °C / min at room temperature and held for 120 min for primary sintering; then heated to 550 °C at a heating rate of 1.5 °C / min and held for 90 min for secondary sintering; then heated to 1000 °C at a heating rate of 10 °C / min and held for 180 min for tertiary sintering.

[0092] The remaining preparation methods and parameters are the same as those in Example 1.

[0093] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.4%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0094] Example 10

[0095] The difference between this example and Example 1 is that in step (1), 850 g of lithium hydroxide, 75 g of lithium carbonate, and 75 g of lithium oxalate (the mass ratio of lithium hydroxide, lithium carbonate, and lithium oxalate is 85:7.5:7.5) are stirred and dispersed for 3 min to obtain a mixed material. The mixed material is placed in a box furnace and heated to 450 °C at a heating rate of 5 °C / min at room temperature and held for 60 min for primary sintering; then heated to 550 °C at a heating rate of 0.4 °C / min and held for 100 min for secondary sintering; then heated to 980 °C at a heating rate of 10 °C / min and held for 180 min for tertiary sintering.

[0096] The remaining preparation methods and parameters are the same as those in Example 1.

[0097] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.5%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0098] Example 11

[0099] This example provides a preparation method for a lithium salt for lithium-ion batteries, and the preparation method includes the following steps:

[0100] (1) Load 1 kg of lithium hydroxide (particle size D50 is 3 μm) into a corundum crucible and place it in a tube furnace. Continuously introduce oxygen into the tube furnace at an oxygen flow rate of 3 L / min. When the mass concentration of oxygen in the tube furnace is 99.6%, heat it from room temperature to 900 °C at a heating rate of 10 °C / min and hold for 360 min for sintering to obtain a sintered product;

[0101] (2) Continue to maintain an oxygen flow of 3 L / min. Naturally cool the sintered product to 100 °C and then take it out, and crush it using a mechanical crusher to obtain a lithium salt for lithium-ion batteries with a particle size D50 of 20.35 μm, that is, high-purity lithium oxide, with a mass fraction of 98.9% and the hetero-phase admixture being LiOH.

[0102] Example 12

[0103] The difference between this example and Example 11 is that in step (1), it is heated from room temperature to 700 °C at a heating rate of 1 °C / min and held for 300 min for sintering.

[0104] The remaining preparation methods and parameters are the same as those in Example 11.

[0105] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 98.9% and the hetero-phase admixture being LiOH.

[0106] Example 13

[0107] The difference between this example and Example 11 is that in step (1), it is heated from room temperature to 800 °C at a heating rate of 10 °C / min and held for 240 min for sintering.

[0108] The remaining preparation methods and parameters are the same as those in Example 11.

[0109] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.0% and the hetero-phase admixture being LiOH.

[0110] Example 14

[0111] The difference between this example and Example 11 is that in step (1), load 1 kg of lithium carbonate (particle size D50 is 5 μm) into a corundum crucible and place it in a box furnace. Heat it from room temperature to 1100 °C at a heating rate of 20 °C / min and hold for 180 min for sintering.

[0112] The remaining preparation methods and parameters are the same as those in Example 11.

[0113] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.0%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0114] Example 15

[0115] The difference between this example and Example 11 is that in step (1), 1 kg of lithium oxalate (particle size D50 is 1 μm) was loaded into a corundum crucible and placed in a box furnace. It was heated to 1100 °C at a heating rate of 6 °C / min at room temperature and sintered for 180 min while maintaining the temperature.

[0116] The remaining preparation methods and parameters are the same as those in Example 11.

[0117] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.1%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0118] Example 16

[0119] The difference between this example and Example 11 is that in step (1), 900 g of lithium hydroxide and 100 g of lithium carbonate (mass ratio of lithium hydroxide to lithium carbonate is 90:10) were stirred and dispersed for 3 min at a speed of 600 rpm using a mixing blender to obtain a mixture. The mixture was placed in a box furnace and heated to 900 °C at a heating rate of 10 °C / min at room temperature and sintered for 180 min while maintaining the temperature.

[0120] The remaining preparation methods and parameters are the same as those in Example 11.

[0121] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.0%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0122] Example 17

[0123] The difference between this example and Example 11 is that in step (1), 900 g of lithium hydroxide and 100 g of lithium oxalate (mass ratio of lithium hydroxide to lithium oxalate is 90:10) were stirred and dispersed for 3 min at a speed of 600 rpm using a mixing blender to obtain a mixture. The mixture was heated to 1000 °C at a heating rate of 10 °C / min at room temperature and sintered for 180 min while maintaining the temperature.

[0124] The remaining preparation methods and parameters are the same as those in Example 11.

[0125] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.2%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0126] Example 18

[0127] The difference between this example and Example 17 is that lithium hydroxide is replaced by lithium carbonate.

[0128] The remaining preparation methods and parameters are the same as those in Example 17.

[0129] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 98.9%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0130] Example 19

[0131] The difference between this example and Example 11 is that in step (1), 800 g of lithium hydroxide, 100 g of lithium carbonate, and 100 g of lithium oxalate (the mass ratio of lithium hydroxide, lithium carbonate, and lithium oxalate is 80:10:10) are stirred and dispersed for 3 min to obtain a mixture. The mixture is heated to 1000 °C at a heating rate of 10 °C / min at room temperature and sintered for 180 min.

[0132] The remaining preparation methods and parameters are the same as those in Example 11.

[0133] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 98.8%, and the heterophase dopants are LiOH and Li 2 CO 3 。

[0134] Example 20

[0135] The difference between this example and Example 11 is that in step (1), 850 g of lithium hydroxide, 75 g of lithium carbonate, and 75 g of lithium oxalate (the mass ratio of lithium hydroxide, lithium carbonate, and lithium oxalate is 85:7.5:7.5) are stirred and dispersed for 3 min to obtain a mixture. The mixture is heated to 980 °C at a heating rate of 10 °C / min at room temperature and sintered for 180 min.

[0136] The remaining preparation methods and parameters are the same as those in Example 11.

[0137] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 99.0%, and the heterophase dopants are LiOH and Li 2 CO3 。

[0138] Example 21

[0139] The difference between this example and Example 1 is that the mass concentration of oxygen in the tubular furnace in steps (1) and (2) is 99%.

[0140] The remaining preparation methods and parameters are the same as those in Example 1.

[0141] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 98.0%, and the heterophase dopant is LiOH.

[0142] Example 22

[0143] The difference between this example and Example 1 is that the oxygen flow rate in steps (1) and (2) is 0.5 L / min.

[0144] The remaining preparation methods and parameters are the same as those in Example 1.

[0145] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 97.2%, and the heterophase dopant is LiOH.

[0146] Example 23

[0147] The difference between this example and Example 1 is that the oxygen flow rate in steps (1) and (2) is 6 L / min.

[0148] The remaining preparation methods and parameters are the same as those in Example 1.

[0149] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 98.1%, and the heterophase dopant is LiOH.

[0150] Example 24

[0151] The difference between this example and Example 1 is that the heating rate of the secondary sintering in step (1) is 0.1 °C / min.

[0152] The remaining preparation methods and parameters are the same as those in Example 1.

[0153] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 97.6%, and the heterophase dopant is LiOH.

[0154] Example 25

[0155] The difference between this example and Example 1 is that the heating rate of the secondary sintering in step (1) is 3 °C / min.

[0156] The remaining preparation methods and parameters are the same as those in Example 1.

[0157] The lithium salt for lithium-ion batteries prepared in this example is high-purity lithium oxide, with a mass fraction of 97.7%, and the impurity dopant is LiOH.

[0158] Comparative Example 1

[0159] The difference between this comparative example and Example 1 is that the oxygen introduced in step (1) is replaced by nitrogen.

[0160] The remaining preparation methods and parameters are the same as those in Example 1.

[0161] Comparative Example 2

[0162] The difference between this comparative example and Example 1 is that in the tubular furnace of step (1), first evacuate to 150 Pa, then introduce oxygen, and then perform primary sintering, secondary sintering, and tertiary sintering.

[0163] The remaining preparation methods and parameters are the same as those in Example 1.

[0164] Comparative Example 3

[0165] This comparative example provides a preparation method for a lithium salt for lithium-ion batteries, and the preparation method includes the following steps:

[0166] Mix lithium hydroxide and hydrogen peroxide, then filter to collect the resulting reaction precipitate, vacuum bake at 80 °C to remove surface residual moisture, and then perform vacuum sintering of the dehydrated material at 600 °C for 10 h to obtain the reaction product Li 2 O.

[0167] Performance Test

[0168] The lithium salts for lithium-ion batteries prepared in the above Examples 1-25 and Comparative Examples 1-3 were subjected to purity tests to obtain the mass fraction of lithium oxide in the lithium salts for lithium-ion batteries.

[0169] The test results are shown in Table 1.

[0170] Table 1

[0171]

[0172]

[0173] Analysis:

[0174] As can be seen from the above table, the lithium oxide obtained by the method proposed in the present invention has the advantages of low sintering temperature, easy discharging after sintering, small mass production difficulty, and high purity.

[0175] From the comparison of the data results of Examples 1-10 and 11-20, it can be seen that the multi-stage sintering method is conducive to obtaining a high-purity lithium oxide phase.

[0176] From the data results of Example 1 and Example 21, it can be seen that if the mass concentration of oxygen in the tube furnace is too low, the crucible material will partially stick together, resulting in a decrease in purity.

[0177] From the data results of Example 1 and Example 22-23, it can be seen that if the oxygen flow rate is too low, the gas circulation is not smooth, and the sample bonding crucible is seriously too large, resulting in a decrease in purity; if the oxygen flow rate is too high, the material reaction is not sufficient, resulting in a decrease in purity.

[0178] From the data results of Example 1 and Examples 24-25, it can be seen that if the heating rate of the secondary sintering is too low, the material will slowly decompose at low temperature for a long time, the reaction rate will decrease, and the purity will decrease; if the heating rate of the secondary sintering is too high, the amount of water vapor generated will be large, and the exhaust will not be timely, which will cause the material to stick to the crucible and the purity will decrease.

[0179] From the data results of Example 1 and Comparative Example 1, it can be seen that if the preparation of lithium salt for lithium-ion batteries is carried out in a nitrogen atmosphere, the material will corrode the bonding crucible severely, resulting in a decrease in purity.

[0180] From the data results of Example 1 and Comparative Example 2, it can be seen that if the tube furnace is first evacuated and then oxygen is introduced, and then the first-stage sintering, the second-stage sintering and the third-stage sintering are performed, the material will partially adhere to the crucible, resulting in a decrease in purity.

[0181] From the data results of Example 1 and Comparative Example 3, it can be seen that if lithium hydroxide and hydrogen peroxide are mixed to prepare lithium oxide, the entire reaction process is complicated and the degree of material reaction is limited, resulting in the inability to obtain high-purity lithium oxide.

[0182] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A lithium salt for lithium ion batteries, characterized in that: The lithium salt for lithium ion battery comprises lithium oxide and heterophase dopant; The heterogeneous dopant includes LiOH and / or Li2CO3. Based on the mass of the lithium salt for lithium ion batteries, the mass fraction of the heterogeneous dopant is ≤1.5%.

2. A method for preparing a lithium salt for a lithium ion battery as claimed in claim 1, characterized in that: The preparation method comprises the following steps: (1) Sintering a lithium source in an oxygen-containing atmosphere to obtain a sintered product; (2) Post-treating the sintered product in an oxygen-containing atmosphere to obtain the lithium salt for lithium ion battery.

3. The preparation method according to claim 2, characterized in that: In the oxygen-containing atmosphere of step (1), the mass concentration of oxygen is ≥99.5%, preferably ≥99.9%; Preferably, in the oxygen-containing atmosphere of step (1), the flow rate of oxygen is 1-5 L / min.

4. The preparation method according to claim 2 or 3, characterized in that: The lithium source in step (1) comprises any one of lithium hydroxide, lithium carbonate or lithium oxalate or a combination of at least two thereof, preferably LiOH and Li2CO3; Preferably, the mass ratio of LiOH to Li2CO3 is (80-98):(2-20); Preferably, the particle size D50 of the lithium source is 1-10 μm, preferably 1-3 μm.

5. The preparation method according to any one of claims 2 to 4, characterized in that: The sintering method of step (1) is one-time sintering, and the heating rate of the one-time sintering is 1-20°C / min; Preferably, the primary sintering temperature is 700-1100°C; Preferably, the primary sintering time is 180-720 min.

6. The preparation method according to any one of claims 2 to 4, characterized in that: The sintering method of step (1) is multi-stage sintering, and the multi-stage sintering includes primary sintering, secondary sintering and tertiary sintering performed in sequence; Preferably, the heating rate of the primary sintering is 1-20°C / min, preferably 2-10°C / min; Preferably, the primary sintering temperature is 400-500°C; Preferably, the holding time of the primary sintering is 30-120 min.

7. The preparation method according to claim 6, characterized in that: The heating rate of the secondary sintering is 0.2-2°C / min, preferably 0.5-1°C / min; Preferably, the temperature of the secondary sintering is 550-600°C; Preferably, the holding time of the secondary sintering is 30-120 min.

8. The preparation method according to claim 6 or 7, characterized in that: The heating rate of the three-stage sintering is 1-20°C / min, preferably 2-10°C / min; Preferably, the temperature of the three-stage sintering is 700-1100°C; Preferably, the holding time of the three-stage sintering is 180-720 min, preferably 300-600 min.

9. The preparation method according to any one of claims 2 to 8, characterized in that: In the oxygen-containing atmosphere of step (2), the mass concentration of oxygen is ≥ 99.5%; Preferably, the post-treatment step in step (2) includes cooling and crushing; Preferably, after the cooling, the temperature of the sintered product is 30-100°C; Preferably, the crushing method includes any one of ball milling, roller crushing, mechanical crushing or air flow crushing, preferably mechanical crushing.

10. The preparation method according to any one of claims 2 to 9, characterized in that: The preparation method comprises the following steps: (1) In an oxygen atmosphere with an oxygen mass concentration of ≥99.5%, heating at least one lithium source from room temperature to 400-500°C at a heating rate of 1-20°C / min, and keeping the temperature for 30-120min to perform primary sintering; then continuing to heat to 550-600°C at a heating rate of 0.2-2°C / min, and keeping the temperature for 30-120min to perform secondary sintering; then continuing to heat to 700-1100°C at a heating rate of 1-20°C / min, and keeping the temperature for 180-720min to perform tertiary sintering to obtain a sintered product; (2) In an oxygen atmosphere with an oxygen mass concentration of ≥99.5%, the sintered product is cooled to 30-100° C. and crushed to a particle size D50 of 1-10 μm to obtain the lithium salt for lithium ion battery.

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