Lithium supplement, preparation method thereof and battery

Abstract

The application discloses a lithium supplement agent, a preparation method thereof and a battery, and belongs to the technical field of battery materials. The lithium supplement agent comprises a porous sponge-like substrate and lithium salts filled in the surface and pores of the porous sponge-like substrate; wherein the porous sponge-like substrate contains a thickening agent, conductive carbon black and a modified catalyst. The modified catalyst is obtained by sintering at least three of cobalt nitrate, nickel nitrate, calcium nitrate and titanium dioxide with graphene or carbon nanotubes; and the lithium salts comprise at least two of lithium hydroxide, lithium carbonate and lithium oxalate. The lithium supplement agent has stable structure, and the initial charge decomposition voltage can be as low as 4.0 V. The preparation method is simple and suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, in particular to a lithium supplementing agent, a preparation method thereof and a battery. BACKGROUND

[0002] The lithium supplementing agent is a functional additive. The maximum potential of the positive and negative electrode materials can be stimulated by accurate lithium supplementing. The performance of the battery can be effectively improved by a small amount of the lithium supplementing agent, and the lithium supplementing agent is suitable for lithium battery materials of various systems. According to different lithium supplementing methods, the lithium supplementing agent is mainly divided into positive electrode lithium supplementing agents and negative electrode lithium supplementing agents. The positive electrode lithium supplementing is usually achieved by electrochemical method. The active lithium is released by adding a material to the positive electrode during the charging process. The negative electrode lithium supplementing includes self-discharge lithium supplementing, physical lithium supplementing, chemical lithium supplementing and electrochemical lithium supplementing.

[0003] The positive electrode lithium supplementing is relatively simple. The lithium supplementing agent can be added during the homogenization of the positive electrode slurry, and no additional process improvement is required and the cost is low. Among the positive electrode lithium supplementing agents, there are two main categories. One is lithium-rich inorganic matter, such as lithium nickelate and lithium ferrite. The lithium supplementing agent produces oxygen during lithium supplementing. The free nanoscale metal oxide remaining in the positive electrode side after lithium supplementing will decompose the electrolyte, resulting in a problem of a sharp drop in the later cycle of the battery. The other is lithium organic salt, such as lithium oxalate. The decomposition voltage of the lithium organic salt is high, and a catalyst needs to be added. The free nanoscale catalyst particles released after lithium supplementing will also decompose the electrolyte, resulting in a problem of a sharp drop in the later cycle of the battery.

[0004] In view of this, the present application is provided. SUMMARY

[0005] The present application aims to provide a lithium supplementing agent, a preparation method thereof and a battery, so as to solve or improve the above technical problems.

[0006] The present application can be achieved in the following manner:

[0007] In a first aspect, the present application provides a lithium supplementing agent. The lithium supplementing agent comprises a porous sponge-like substrate and lithium salt filled in the surface and pores of the porous sponge-like substrate. The porous sponge-like substrate contains a thickening agent, conductive carbon black and a modified catalyst. The modified catalyst is obtained by sintering at least three of cobalt nitrate, nickel nitrate, calcium nitrate and titanium dioxide with graphene or carbon nanotube. The lithium salt includes at least two of lithium hydroxide, lithium carbonate and lithium oxalate.

[0008] In an optional embodiment, the lithium supplementing agent has at least one of the following characteristics:

[0009] Characteristic 1: The mass ratio of the conductive carbon black to the lithium salt is (0.15-1):1.

[0010] Feature 2: the mass ratio of the modified catalyst to the lithium salt is (0.03-0.15):1;

[0011] Feature 3: the mass ratio of the thickening agent to the lithium salt is (0.001-0.025):1;

[0012] Feature 4: the thickening agent is a water-soluble thickening agent; preferably, the thickening agent comprises at least one of styrene butadiene rubber, polyacrylic acid, and sodium carboxymethyl cellulose;

[0013] Feature 5: the conductive carbon black comprises at least one of Super P, Cabot carbon black BP2000, Ketjen black EJ-300J, and Ketjen black ECP-600JD;

[0014] Feature 6: the single particle size of the modified catalyst is 5 nm-60 nm;

[0015] Feature 7: the lithium salt is in the form of a lump; preferably, the particle size of the lithium salt in the form of a lump is 0.8 μm-10 μm.

[0016] In a second aspect, the present application provides a preparation method of the lithium supplement as in the foregoing embodiments, comprising the following steps: adding the conductive carbon black and the modified catalyst into a water solution of the thickening agent, then adding the oxalic acid dihydrate and the anhydrous lithium hydroxide and mixing to obtain a mixed slurry; and baking and crushing the mixed slurry.

[0017] In an optional embodiment, the mass ratio of the oxalic acid dihydrate to the anhydrous lithium hydroxide is (2-2.5):1;

[0018] In an optional embodiment, the baking temperature is 80°C-180°C.

[0019] In an optional embodiment, the modified catalyst is obtained by mixing a catalytic raw material with a carrier and then sintering;

[0020] wherein the catalytic raw material comprises at least three of cobalt nitrate, nickel nitrate, calcium nitrate, and titanium dioxide, and the carrier comprises graphene or carbon nanotubes.

[0021] In an optional embodiment, the mass ratio of the catalytic raw material to the carrier is (6-10):1;

[0022] and / or, the catalytic raw material contains at least cobalt nitrate or nickel nitrate;

[0023] and / or, the titanium dioxide is in nanoscale; preferably, the particle size of the titanium dioxide is less than 30 nm;

[0024] and / or, the graphene is multi-layer graphene; preferably, the number of layers of the multi-layer graphene is 6-10 layers;

[0025] And / or, the carbon nanotube is a single-walled carbon nanotube; preferably, the single-walled carbon nanotube has a diameter of 1-3 nm and a tube length of 6-20 μm.

[0026] In an optional embodiment, the sintering temperature is 400-1000°C; the sintering atmosphere is a nitrogen atmosphere; and the sintering time is 1-8 h.

[0027] In a third aspect, the present application provides a battery comprising the lithium supplementing agent of the preceding embodiments.

[0028] The present application has the following advantages:

[0029] The lithium supplementing agent provided by the present application has the lithium salt closely bonded to the interior and surface of the porous sponge-like substrate, so that the lithium supplementing agent has a stable structure, and after the lithium supplementing is completed, the lithium salt is decomposed, but the modified catalyst in the porous sponge-like substrate is not released, which not only helps to improve the energy density of the battery, but also helps to improve the cycle life of the battery. In addition, the lithium supplementing agent has a relatively low decomposition voltage, can quickly exert the lithium supplementing effect, has a good lithium supplementing effect, and can effectively improve the problem of cycle diving in the later stage of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0031] Figure 1 SEM image of the lithium supplementing agent prepared in Example 1 of the present application;

[0032] Figure 2 SEM image of the positive electrode tab after the first charge to 4.6 V, which is further prepared from the lithium supplementing agent prepared in Example 1 of the test example. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0034] The lithium supplementing agent provided by the present application and its preparation method and battery will be specifically described below.

[0035] The present application provides a lithium supplement agent, which comprises a porous sponge-like substrate and lithium salts filled in the surface and pores of the porous sponge-like substrate.

[0036] The porous sponge-like substrate contains a thickening agent, conductive carbon black and a modified catalyst from sintering of at least three of cobalt nitrate, nickel nitrate, calcium nitrate and titanium dioxide with graphene or carbon nanotubes. The lithium salts include at least two of lithium hydroxide, lithium carbonate and lithium oxalate.

[0037] In the above lithium supplement agent, the thickening agent can provide viscosity to complex the conductive carbon black, the modified catalyst and the lithium salts into a whole, and can also make the lithium supplement agent brittle and form loose solid with cracks after drying, facilitating later pulverization and fine grinding. The conductive carbon black mainly plays a role in improving electrical conductivity. The modified catalyst can lower the decomposition voltage of the lithium supplement agent, so that it can quickly take effect. Moreover, the graphene or carbon nanotube contained in the modified catalyst can load catalytic substances, and together with the solidification effect of the thickening agent, can effectively prevent the release and shedding of the modified catalyst, and can also play a role in improving the electrical conductivity of the lithium supplement agent together with the conductive carbon black.

[0038] In the above lithium supplement agent, the lithium salts are closely combined with the inside and surface of the porous sponge-like substrate, and have a stable structure. After the lithium supplement is completed, the lithium salts decompose, but the modified catalyst in the porous sponge-like substrate does not release, which is beneficial to improving the energy density of the battery and the cycle life of the battery. The decomposition voltage of the lithium supplement agent can be as low as 4.0 V, and the lithium supplement agent can quickly take effect.

[0039] In some optional embodiments, the mass ratio of the conductive carbon black to the lithium salts can be (0.15-1):1, such as 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1 or 1:1, etc., and can also be other values within the range of (0.15-1):1.

[0040] If the amount of the conductive carbon black is too small, it is not conducive to the decomposition of the lithium supplement agent, and will increase the delithiation potential; if the amount of the conductive carbon black is too large, it will reduce the effect of the lithium supplement agent, and the improvement of the cycle performance of the battery is limited.

[0041] The mass ratio of the modified catalyst to the lithium salt can be (0.03-0.15):1, such as 0.03:1, 0.04:1, 0.05:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.10:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, or 0.15:1, and can also be other values within the range of (0.03-0.15):1.

[0042] If the amount of the modified catalyst is too small, it is difficult to reduce the decomposition voltage of the lithium supplement agent, and the lithium salt is also prone to incomplete decomposition; if the amount of the modified catalyst is too large, the electrolyte is prone to decomposition, and the subsequent cycle of the battery is prone to collapse.

[0043] The mass ratio of the thickening agent to the lithium salt can be (0.001-0.025):1, such as 0.001:1, 0.005:1, 0.010:1, 0.015:1, 0.020:1, or 0.025:1, and can also be other values within the range of (0.001-0.025):1.

[0044] If the amount of the thickening agent is too small, the conductive carbon black, the modified catalyst, and the lithium salt cannot be integrated and solidified, and the components will be precipitated in turn and agglomerated during oven drying; if the amount of the thickening agent is too large, the viscosity of the system is prone to be too large, and the components cannot be mixed smoothly.

[0045] In some optional embodiments, the thickening agent is a water-soluble thickening agent, which can include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), and sodium carboxymethyl cellulose (CMC-Na).

[0046] The conductive carbon black can include at least one of Super P, Cabot carbon black BP2000, Ketjen black EJ-300J, and Ketjen black ECP-600JD.

[0047] In some optional embodiments, the single particle size of the modified catalyst can be 5-60 nm, such as 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, or 60 nm, and can also be other values within the range of 5-60 nm.

[0048] If the single particle size of the modified catalyst is too small, it is prone to agglomeration and difficult to disperse, which is not conducive to uniform mixing; if the single particle size of the modified catalyst is too large, it is not conducive to contact with the lithium salt, and its surface area is too small.

[0049] In some preferred embodiments, to ensure full coverage and tight binding of the lithium salt, the substances in the modified catalyst exist in both a composite form and an independent free form. In some embodiments, the modified catalyst is in the form of metallic cobalt, metallic nickel, etc., composited with graphene or carbon nanotubes, or in the form of cobalt tetroxide, cobalt monoxide, metallic cobalt, nickel monoxide, metallic nickel, titanium dioxide, cobalt titanate, calcium titanate, and nickel titanate, etc., existing independently and free.

[0050] In some optional embodiments, the lithium salt is in the form of fragments. Preferably, the particle size of the fragmented lithium salt can be 0.8 μm to 10 μm, such as 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, or other values ​​within the range of 0.8 μm to 10 μm.

[0051] The above-mentioned fragmented lithium salt is more conducive to decomposition. Because this process has a step of heating to remove the solvent, the small-particle lithium salt will grow, so it is difficult to obtain nano-scale lithium salt stably; if the particle size of the fragmented lithium salt is too large, it is not conducive to decomposition, and the pores after decomposition are too large, which is not conducive to the stability of the electrode structure.

[0052] As mentioned above, the lithium replenisher provided by the present invention has a low decomposition voltage, can quickly exert its lithium replenishment effect, has good lithium replenishment effect, can significantly improve the cycle performance of the battery, and can also maintain a stable structure and good conductive path after the battery reaction is complete, so as to stably exert electrical performance. This lithium replenisher is suitable not only for lithium-ion batteries but also for lithium solid-state battery systems.

[0053] Accordingly, the present invention also provides a method for preparing the lithium supplement, comprising the following steps: adding conductive carbon black and a modified catalyst to an aqueous solution of a thickener, then adding dihydrated oxalic acid and anhydrous lithium hydroxide and mixing to obtain a mixed slurry; and baking the mixed slurry. After baking, the mixed slurry may be further pulverized.

[0054] The mixed slurry is baked and dehydrated to obtain a porous sponge-like substrate and a lithium salt filled on the surface and in the pores of the porous sponge-like substrate. The conductive carbon black, the modified catalyst and the thickener together form a cross-linked porous sponge-like substrate.

[0055] The mass ratio of oxalic acid dihydrate to anhydrous lithium hydroxide can be (2-2.5):1, such as 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, or 2.5:1, or other values ​​within the range of (2-2.5):1. By controlling the excess of anhydrous lithium hydroxide, a portion of the anhydrous lithium hydroxide reacts with oxalic acid dihydrate to form lithium oxalate, and the remaining anhydrous lithium hydroxide forms lithium carbonate during the baking process, thereby ensuring that the lithium salt has at least two components.

[0056] In some preferable embodiments, the lithium supplementing agent, the modified catalyst and the thickening agent can be added in an amount such that the mass ratio of the conductive carbon black to the lithium salt in the lithium supplementing agent is (0.15-1):1, the mass ratio of the modified catalyst to the lithium salt is (0.03-0.15):1, and the mass ratio of the thickening agent to the lithium salt is (0.001-0.025):1.

[0057] In some alternative embodiments, the oxalic acid dihydrate and the lithium hydroxide monohydrate can be added and mixed together for 1-8 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, or other values within the range of 1-8 hours. The mixing can be achieved by using any of a ball mill, a sand mill, a high-speed dispersion disc, etc.

[0058] In some alternative embodiments, the solid content of the mixed slurry is not less than 20 wt%.

[0059] In some alternative embodiments, the baking temperature can be 80-180°C, such as 80°C, 100°C, 120°C, 140°C, 160°C or 180°C, or other values within the range of 80-180°C.

[0060] In some alternative embodiments, the modified catalyst is obtained by sintering a mixture of a catalytic raw material and a carrier. The catalytic raw material includes at least three of cobalt nitrate, nickel nitrate, calcium nitrate and titanium dioxide, and the carrier includes graphene or a carbon nanotube.

[0061] In some alternative embodiments, the mass ratio of the catalytic raw material to the carrier can be (6-10):1, such as 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 or 10:1, or other values within the range of (6-10):1.

[0062] In some preferable embodiments, the catalytic raw material contains at least cobalt nitrate or nickel nitrate.

[0063] In some alternative embodiments, the titanium dioxide is in nanoscale. Preferably, the particle size of the titanium dioxide is less than 30 nm.

[0064] In some preferable embodiments, the graphene is multilayer graphene; in some more preferable embodiments, the multilayer graphene has 6-10 layers.

[0065] In some preferable embodiments, the carbon nanotube is a single-walled carbon nanotube; in some more preferable embodiments, the single-walled carbon nanotube has a diameter of 1-3 nm and a length of 6-20 μm.

[0066] In some alternative embodiments, the sintering temperature can be 400-1000℃, such as 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 1000℃, or other values within the range of 400-1000℃. Cobalt nitrate, nickel nitrate, calcium nitrate and titanium dioxide are sintered with graphene or carbon nanotubes to obtain a plurality of mixtures containing tricobalt tetroxide, cobalt monoxide, metallic cobalt, nickel monoxide, metallic nickel, titanium dioxide, cobalt titanate, calcium titanate and nickel titanate.

[0067] The sintering atmosphere is a nitrogen atmosphere. The sintering time can be 1-8h, such as 1h, 2h, 3h, 4h, 5h, 6h, 7h or 8h, or other values within the range of 1-8h.

[0068] As described above, the preparation method of the lithium supplement provided by the present application does not rely on the freeze-drying or spray-drying of low-concentration solutions, and the materials in the mixed slurry (the solid content can be not less than 20wt%) are directly mixed by mechanical mixing, followed by air drying, rolling and crushing to obtain the lithium supplement. The method is simple and efficient, and can ensure stable and reliable production of even 10,000-ton lithium supplement.

[0069] In addition, the present application also provides a battery containing the lithium supplement. The battery can have a longer cycle life.

[0070] The features and performance of the present application are further described in detail below in combination with examples.

[0071] Example 1

[0072] The present example provides a lithium supplement, and the preparation method thereof comprises:

[0073] S1: Preparation of a modified catalyst.

[0074] In 200mL of pure water, 60g of cobalt nitrate hexahydrate, 10g of nickel nitrate hexahydrate, 0.3g of titanium dioxide and 10g of graphene were stirred and mixed for 0.5h, and then sintered in a tube furnace under a nitrogen atmosphere at 450℃ for 1h to obtain a modified catalyst.

[0075] The graphene is multi-layer graphene with a layer number of 6-10 layers. The particle size of the titanium dioxide is 30nm. The single particle size of the modified catalyst is 5-60nm, and the average particle size is 18nm.

[0076] S2: Preparation of a mixed slurry, baking and crushing.

[0077] Take 1 g of sodium carboxymethyl cellulose (CMC2200) into 200 mL of deionized water, stir for 10 min until completely dissolved, then add 30 g of Cabot carbon black BP2000, 10 g of modified catalyst and 200 mL of deionized water, stir for 0.5 h, then add 240 g of oxalic acid dihydrate and 100 g of anhydrous lithium hydroxide and 200 g of deionized water, stir for 8 h to obtain a mixed slurry; the mixed slurry is baked in a blast oven at 80°C overnight, and finally the dried lumps are crushed and pulverized to obtain a lithium supplement.

[0078] The SEM image of the lithium supplement prepared in this example is shown in Figure 1 Figure 1 It can be seen that: the lithium supplement includes a porous sponge-like substrate, and lithium salt filled in the surface and pores of the porous sponge-like substrate. Among them, the lithium salt is in the form of a lump, and the average particle size is 1 μm-2 μm.

[0079] The mass ratio of conductive carbon black to lithium salt in the lithium supplement is 0.15:1; the mass ratio of modified catalyst to lithium salt is 0.05:1; the mass ratio of thickening agent to lithium salt is 0.005:1. The modified catalyst contained in the above-mentioned porous sponge-like substrate includes cobalt trioxide, cobalt monoxide, metallic cobalt, nickel monoxide, metallic nickel, titanium dioxide and graphene (cobalt trioxide, cobalt monoxide, metallic cobalt, nickel monoxide, metallic nickel, titanium dioxide can exist in free form), and the lithium salt contained in the above-mentioned porous sponge-like substrate includes lithium hydroxide, lithium carbonate and lithium oxalate.

[0080] Example 2

[0081] The difference between this example and Example 1 is that in S2, the baking temperature of the blast oven is 120°C.

[0082] Example 3

[0083] The difference between this example and Example 1 is that in S2, the baking temperature of the blast oven is 160°C.

[0084] Example 4

[0085] The difference between this example and Example 1 is that in S2, the mixed slurry is obtained after stirring for 4 h.

[0086] Example 5

[0087] The difference between this example and Example 1 is that in S2, the mixed slurry is obtained after stirring for 2 h.

[0088] Example 6

[0089] The difference between this example and Example 1 is that in S2, 250 g of oxalic acid dihydrate is added. ​

[0090] Example 7

[0091] The difference between this example and Example 1 is that 220 g of oxalic acid dihydrate is added in S2.

[0092] Example 8

[0093] The difference between this example and Example 1 is that 6 g of a modified catalyst is added in S2. The mass ratio of the modified catalyst to lithium salt is 0.03:1.

[0094] Example 9

[0095] The difference between this example and Example 1 is that 24 g of a modified catalyst is added in S2. The mass ratio of the modified catalyst to lithium salt is 0.12:1.

[0096] Example 10

[0097] The difference between this example and Example 1 is that 0.6 g of sodium carboxymethyl cellulose is added in S2. The mass ratio of the thickening agent to lithium salt is 0.003:1.

[0098] Example 11

[0099] The difference between this example and Example 1 is that 1 g of sodium carboxymethyl cellulose and 1 g of polyacrylic acid are added in S2. The mass ratio of the thickening agent to lithium salt is 0.01:1.

[0100] Example 12

[0101] The difference between this example and Example 1 is that 40 g of cobalt nitrate hexahydrate, 30 g of nickel nitrate hexahydrate, 0.3 g of titanium dioxide, and 10 g of graphene are added in S1. The modified catalyst has a single particle size of 5 nm to 60 nm and an average particle size of 14 nm.

[0102] Example 13

[0103] The difference between this example and Example 1 is that 10 g of cobalt nitrate hexahydrate, 60 g of nickel nitrate hexahydrate, 0.3 g of titanium dioxide, and 10 g of carbon nanotubes are added in S1. The modified catalyst has a single particle size of 5 nm to 60 nm and an average particle size of 10 nm.

[0104] Example 14

[0105] The difference between this example and Example 1 is that the sintering time is 2 h in S1. The modified catalyst has a single particle size of 5 nm to 60 nm and an average particle size of 31 nm.

[0106] Example 15

[0107] The difference between this example and Example 1 is that in S1, the sintering temperature is 650°C. The modified catalyst contained in the porous sponge-like substrate includes tricobalt tetroxide, cobalt monoxide, metallic cobalt, nickel monoxide, metallic nickel, titanium dioxide, cobalt titanate, nickel titanate, and graphene. The lithium salt contained in the porous sponge-like substrate includes lithium hydroxide, lithium carbonate, and lithium oxalate. The single particle size of the modified catalyst is 5 nm to 60 nm, and the average particle size is 58 nm.

[0108] Comparative Example 1

[0109] This comparative example provides a lithium supplement agent, and the preparation method thereof includes:

[0110] S1: Preparation of catalyst.

[0111] 10 g of commercially available tricobalt tetroxide (particle size 30 nm) was weighed and dried in a 105°C oven for 1 h to obtain the catalyst.

[0112] S2: Preparation of mixed slurry and spray drying.

[0113] 40 g of commercially available anhydrous lithium oxalate was dissolved in 600 mL of deionized water, then 8 g of catalyst and 1 g of Ketjen black were added, and after uniform dispersion, spray drying was carried out at 230°C at a flow rate of 4 mL / min to obtain a lithium oxalate lithium supplement agent.

[0114] Comparative Example 2

[0115] This comparative example provides a lithium supplement agent, and the preparation method thereof includes:

[0116] S1: Preparation of catalyst.

[0117] 10 g of commercially available nickel oxide (particle size 30 nm) was weighed and dried in a 105°C oven for 1 h to obtain the catalyst.

[0118] S2: Preparation of mixed slurry and spray drying.

[0119] 40 g of commercially available anhydrous lithium oxalate was dissolved in 600 mL of deionized water, then 8 g of catalyst and 1 g of Ketjen black were added, and after uniform dispersion, spray drying was carried out at 230°C at a flow rate of 4 mL / min to obtain a lithium oxalate lithium supplement agent.

[0120] Comparative Example 3

[0121] This comparative example provides a lithium supplement agent, and the preparation method thereof includes:

[0122] S1: Preparation of catalyst.

[0123] Take 5 g of commercial cobalt tetraoxide (particle size 30 nm) and 5 g of commercial nickel oxide (particle size 30 nm), dry in an oven at 105°C for 1 h to obtain the catalyst.

[0124] S2: Prepare mixed slurry, spray dry.

[0125] Take 40 g of commercial anhydrous lithium oxalate, dissolve in 600 mL of deionized water, then add 8 g of catalyst and 1 g of Ketjen black, disperse uniformly, and then spray dry at 230°C at a flow rate of 4 mL / min to obtain lithium oxalate lithium supplement agent.

[0126] Comparative Example 4

[0127] The difference between this comparative example and Example 1 is that in S2, 0.6 g of modified catalyst is added. The mass ratio of modified catalyst to lithium salt is 0.003:1.

[0128] Comparative Example 5

[0129] The difference between this comparative example and Example 1 is that in S1, no carrier (graphene or carbon tube) is used.

[0130] Comparative Example 6

[0131] The difference between this comparative example and Example 1 is that in S2, no thickening agent is used.

[0132] Test Example

[0133] The lithium supplement agent prepared in Examples 1-16 and Comparative Examples 1-6 above is applied to the positive electrode of a button cell, with an addition amount of 90 wt% lithium supplement agent, 5 wt% PVDF, and 5 wt% Super P; the negative electrode is a lithium sheet. After assembling the button cell, the temperature is kept at 45°C, and the first charge is 0.2C constant current charging to 4.6V. The decomposition voltage, specific capacity, and other properties of the button cell are tested using an electrochemical test channel. The water content of the lithium supplement agent is obtained by Karl Fischer titration using a moisture detector.

[0134] Table 1 Test Results

[0135]

[0136]

[0137] As can be seen from Table 1, the lithium supplementing agent provided by the embodiments 1-16 can have a lower decomposition voltage than the lithium supplementing agent provided by the comparative examples 1-6. The lithium supplementing agent provided by the embodiments 1-4, 6-7, 13 and 16 can have a lower decomposition voltage and a higher gram capacity performance than the lithium supplementing agent provided by the comparative examples 1-6, and can effectively improve the problem of high water content of the lithium supplementing agent. After the first charge to 4.6V, the positive electrode sheet is taken to make an electron microscope photo, and it can be seen that the structure of the electrode sheet can remain stable and keep the conductive path after the complete supplementing reaction, as shown in Figure 2

[0138] As can be seen from the embodiments 1 and the comparative examples 1-3, the catalytic raw material is first compounded with the carrier to prepare a modified catalyst, and then the modified catalyst is mixed with the thickening agent, the conductive carbon black, the oxalic acid dihydrate and the anhydrous lithium hydroxide and is baked, which can be more conducive to reducing the decomposition voltage of the lithium supplementing agent, improving the low-voltage decomposition efficiency and improving the gram capacity performance of the lithium supplementing agent than directly mixing the catalytic raw material with the anhydrous lithium oxalate and the conductive carbon black and drying, and the production process is water-saving, high-yield, small equipment investment and environment-friendly.

[0139] In summary, the lithium supplementing agent provided by the present application has a low decomposition voltage, can quickly play a lithium supplementing role, has a good lithium supplementing effect, can significantly improve the cycle performance of the battery, and after the complete reaction of the battery, it can still maintain a stable structure and a good conductive path to stably play the electrical performance.

[0140] In summary, the lithium supplementing agent provided by the present application has a low decomposition voltage, can quickly play a lithium supplementing role, has a good lithium supplementing effect, can significantly improve the cycle performance of the battery, and after the complete reaction of the battery, it can still maintain a stable structure and a good conductive path to stably play the electrical performance.

[0141] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A lithium supplement, characterized in that: The lithium supplement comprises a porous sponge-like substrate and a lithium salt filled in the surface and pores of the porous sponge-like substrate; wherein the porous sponge-like substrate contains a thickener, conductive carbon black, and a modified catalyst; the modified catalyst is obtained by sintering at least three of cobalt nitrate, nickel nitrate, calcium nitrate, and titanium dioxide with graphene or carbon nanotubes; and the lithium salt comprises at least two of lithium hydroxide, lithium carbonate, and lithium oxalate. The mass ratio of the modified catalyst to the lithium salt is (0.03-0.15):1; The preparation of the lithium supplement comprises the following steps: adding conductive carbon black and a modified catalyst to an aqueous solution of a thickener, then adding dihydrated oxalic acid and anhydrous lithium hydroxide and mixing to obtain a mixed slurry; and baking and crushing the mixed slurry.

2. The lithium supplement according to claim 1, characterized in that The lithium supplement has at least one of the following characteristics: Feature 1: The mass ratio of the conductive carbon black to the lithium salt is (0.15-1):1; Feature 2: The mass ratio of the thickener to the lithium salt is (0.001-0.025):1; Feature 3: The thickener is a water-soluble thickener; Feature 4: The conductive carbon black includes at least one of Super P, Cabot Black BP2000, Ketjen Black EJ-300J, and Ketjen Black ECP-600JD; Feature 5: The single particle size of the modified catalyst is 5nm~60nm; Feature 6: The lithium salt is in the form of fragments.

3. The lithium supplement according to claim 2, characterized in that The thickener includes at least one of styrene-butadiene rubber, polyacrylic acid and sodium carboxymethyl cellulose.

4. The lithium supplement according to claim 2, characterized in that The particle size of the fragmented lithium salt is 0.8 μm to 10 μm.

5. A method for preparing the lithium supplement according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: adding conductive carbon black and a modified catalyst into a thickener aqueous solution, then adding dihydrated oxalic acid and anhydrous lithium hydroxide and mixing them to obtain a mixed slurry; and baking and crushing the mixed slurry.

6. The preparation method according to claim 5, characterized in that The mass ratio of the oxalic acid dihydrate to the anhydrous lithium hydroxide is (2-2.5):

1.

7. The preparation method according to claim 5, characterized in that The baking temperature is 80℃~180℃.

8. The preparation method according to claim 5, characterized in that The modified catalyst is obtained by mixing a catalytic raw material and a carrier and then sintering; The catalytic raw materials include at least three of cobalt nitrate, nickel nitrate, calcium nitrate and titanium dioxide, and the carrier includes graphene or carbon nanotubes.

9. The preparation method according to claim 8, characterized in that The mass ratio of the catalytic raw material to the carrier is (6-10):

1.

10. The preparation method according to claim 8, characterized in that The catalytic raw material contains at least cobalt nitrate or nickel nitrate; And / or, the titanium dioxide is nanoscale; And / or, the graphene is multilayer graphene; And / or, the carbon nanotubes are single-walled carbon nanotubes.

11. The preparation method according to claim 10, characterized in that: The particle size of the titanium dioxide is less than 30 nm.

12. The preparation method according to claim 10, characterized in that The number of layers of the multilayer graphene is 6 to 10 layers.

13. The preparation method according to claim 10, characterized in that The diameter of the single-walled carbon nanotube is 1 nm to 3 nm, and the tube length is 6 μm to 20 μm.

14. The preparation method according to claim 8, characterized in that The sintering temperature is 400°C~1000°C; the sintering atmosphere is nitrogen atmosphere; and the sintering time is 1h~8h.

15. A battery, characterized in that: The battery contains the lithium supplement according to any one of claims 1 to 4.

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