Battery additive and preparation method thereof, diaphragm, positive plate and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a battery additive and a preparation method thereof, a diaphragm, a positive plate and a lithium ion battery. The battery additive comprises an ammine capsule containing a capsule core and a capsule wall, and the capsule core contains an ammine. According to the battery additive, under the condition that the battery temperature is high, the compound capsule is decomposed to generate ammonia, the capacity of absorbing heat and reducing the temperature is achieved, the flame-retardant effect is achieved, battery thermal runaway can be inhibited, and then the safety performance of the battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a battery additive, a preparation method of the battery additive, a separator containing the battery additive, a positive electrode sheet containing the battery additive and a lithium ion battery containing the battery additive. BACKGROUND

[0002] For the two safety problems of thermal runaway and overcharge failure of lithium ion batteries, the industry and academia mainly solve them from the module end and the cell end. Among them, a fireproof isolation layer can be set at the module end to suppress heat spread, and liquid cooling / liquid heating systems and phase change materials can be used to reduce the temperature rise of the cell; at the cell end, the safety of the battery is improved by optimizing the positive electrode material, separator, negative electrode material and electrolyte.

[0003] The modification of the separator and electrolyte at the cell end is the most effective. For the separator, ceramic coating improves the high temperature resistance and mechanical strength of the separator, and the thermal shutdown separator can improve the melting closed pore at high temperature and block the ion transmission; for the electrolyte, the addition of flame retardant additives such as phosphorus-based or fluorinated solvents can reduce the flammability of the electrolyte.

[0004] For the overcharge safety problem, the prior art adds overcharge additives such as biphenyl and cyclohexylbenzene, which preferentially oxidize and polymerize at high pressure to form a passivation film or release gas to trigger a protection mechanism.

[0005] However, the materials with large heat absorption in the prior art have high endothermic onset temperature, at which time the ternary battery will have serious thermal runaway; and the materials with low endothermic onset temperature have small heat absorption, so it is necessary to find a safe additive with a decomposition temperature close to the actual battery system temperature, large heat absorption and no adverse effect on battery performance. SUMMARY

[0006] The purpose of the present application is to overcome the above technical problems, provide a battery additive and a preparation method, a separator, a positive electrode sheet and a lithium ion battery. The battery additive decomposes to produce ammonia when the battery temperature rises, which not only absorbs heat to reduce the temperature, but also inhibits the thermal runaway of the battery, thereby improving the safety performance of the battery through the additive.

[0007] To achieve the above purpose, the first aspect of the present application provides a battery additive, which comprises: an ammonia complex capsule containing a capsule core and a capsule wall, and the capsule core contains an ammonia complex.

[0008] The second aspect of the present application provides a preparation method of a battery additive, which comprises:

[0009] S1, coating a resin material on the surface of the ammine, to obtain an ammine capsule;

[0010] S2, mixing the ammine capsule with a catalyst, to obtain a mixture;

[0011] wherein the ammine capsule or the mixture is used as a battery additive.

[0012] The third aspect of the present application provides a separator, wherein a modified layer is arranged on the surface of the separator close to the positive electrode side, and the modified layer contains the battery additive provided in the first aspect, or contains the battery additive prepared by the preparation method provided in the second aspect.

[0013] The fourth aspect of the present application provides a positive electrode sheet, wherein the active material layer of the positive electrode sheet contains the battery additive provided in the first aspect, or contains the battery additive prepared by the preparation method provided in the second aspect.

[0014] The fifth aspect of the present application provides a lithium ion battery, wherein the lithium ion battery contains the separator provided in the third aspect, and / or contains the positive electrode sheet provided in the fourth aspect.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] (1) The battery additive provided by the present application includes an ammine capsule, which does not introduce side reactions during normal operation of the battery; when the temperature of the battery is relatively high, the capsule wall melts or decomposes, and the ammine as the capsule core decomposes to produce ammonia, which not only absorbs heat and reduces the temperature of the battery, but also has a fire-retardant effect to inhibit thermal runaway of the battery; at the same time, the stability of the battery system can be controlled through the structural design of the ammine capsule, especially the control of the type and thickness of the capsule wall;

[0017] (2) The battery additive provided by the present application can also include a specific catalyst used in cooperation with the ammine capsule, which further promotes the oxidation of the ammonia gas released under the conditions of battery short circuit and overcharge to nitrogen, water and other harmless gases by the oxidizing positive electrode, promotes the breaking of the battery, avoids the accumulation of flammable gas leading to thermal runaway of the battery, and further reduces the temperature rise rate and termination temperature of the thermal runaway of the battery, which is beneficial to the delay of the thermal runaway of the single battery and the thermal spread of the battery;

[0018] (3) The battery additive provided by the present application is used in lithium ion batteries, especially through coating of the separator or mixing of the positive electrode, which effectively inhibits the intensity of battery thermal runaway and overcharge runaway, and further improves the safety performance of the battery. DETAILED DESCRIPTION

[0019] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, as well as intermediate values that are not explicitly recited; any "range of values" disclosed herein is intended to include all sub-ranges of values that fall within such broader range; all individual values distributed within such range or sub-ranges are included and disclosed; and, all combinations of individual values from

[0020] The first aspect of the present application provides a battery additive, comprising: an ammoniacal compound capsule containing a capsule core and a capsule wall, and the capsule core contains an ammoniacal compound.

[0021] The inventors of the present application have found that, compared with the prior art, using an ammoniacal compound capsule as a battery additive, on the one hand, since the decomposition temperature of the ammoniacal compound is close to the initial temperature of battery thermal runaway, the ammoniacal compound is used as the capsule core; before the battery thermal runaway, the ammoniacal compound is decomposed to produce ammonia gas, which not only has a flame-retardant function, but also has a heat-absorbing function, which correspondingly increases the initial temperature of battery thermal runaway; on the other hand, the ammoniacal compound is coated with a capsule wall, thereby ensuring the stability of the battery system during the battery operation and storage.

[0022] Meanwhile, in order to further improve the flame-retardant and heat-absorbing effects, a specific catalyst can also be added to the battery additive to catalyze the reaction between the ammonia gas released by the decomposition of the ammoniacal compound and the oxidized positive electrode, thereby reducing the release of toxic gas; at the same time, the water formed by the reaction conversion also has a flame-retardant effect.

[0023] In the present application, the ammoniacal compound capsule has a capsule structure, including a capsule wall and a capsule core, and the capsule core is selected from an ammoniacal compound having a heat-absorbing and flame-retardant function, i.e., the capsule core contains an ammoniacal compound that decomposes to produce ammonia gas, unless otherwise specified.

[0024] In the present application, by adjusting the decomposition temperature of the ammoniacal compound to be lower than the initial temperature of battery thermal runaway, the ammoniacal compound is decomposed to absorb heat before the battery thermal runaway, thereby reducing the temperature rise of the battery in the early stage of battery thermal runaway, and the ammonia gas produced can also have a flame-retardant effect, thereby avoiding the high temperature of the battery leading to thermal runaway and delaying the speed of battery thermal runaway.

[0025] In the present application, preferably, the decomposition temperature of the ammoniacal compound is ≤300℃, for example, 300℃, 270℃, 250℃, 240℃, 200℃, 180℃, 160℃, 150℃, 120℃, 100℃, 80℃, 50℃, 40℃, and any value in the range between any two of the numerical values, preferably 80-300℃, further preferably 80-180℃, and more preferably 80-150℃.

[0026] In the present application, the decomposition temperature parameters are measured by TGA-DSC method, for example, the decomposition temperature of [Co(NH3)6]Cl3 is 270℃; the decomposition temperature of [Co(NH3)6]Cl2 is 240℃; the decomposition temperature of [Mg(NH3)6]Cl2 is 120℃; the decomposition temperature of [Ca(NH3)8]Cl2 is 50℃; and the decomposition temperature of ammonium carbamate is 40℃.

[0027] In the present application, further preferably, the ammonia compound is selected from the group consisting of ammoniate and / or ammonium salt, preferably selected from the group consisting of ammonium carbamate, ammonium chlorate, ammonium carbonate, NH4Cl·3NH3, [Co(NH3)6]Cl3, [Co(NH3)6]Cl2, [Sr(NH3)8]Cl2, [Ca(NH3)8]Cl2 and [Mg(NH3)6]Cl2, and at least one of the mixtures, derivatives, coatings and deaminated substances of the above-mentioned substances.

[0028] In the present application, the above-mentioned deaminated substance refers to a substance partially deaminated due to too low decomposition temperature.

[0029] In the present application, preferably, the glass transition temperature of the capsule wall is ≤300℃, for example, 300℃, 250℃, 200℃, 180℃, 170℃, 160℃, 150℃, 140℃, 130℃, 120℃, 110℃, 105℃, 100℃, 95℃, 90℃, 85℃, 82℃, 80℃, and any value within the range of any two numerical values, preferably 80-300℃, more preferably 80-150℃.

[0030] In the present application, the glass transition temperature refers to the temperature at which the resin material changes from glassy state to high elastic state; the glass transition temperature parameter is measured by dilatometer method.

[0031] In the present application, the lower the glass transition temperature of the capsule wall, the better the performance of the battery additive. Further preferably, the glass transition temperature of the capsule wall is ≤ the decomposition temperature of the ammonia compound.

[0032] In some embodiments of the present application, preferably, the difference between the decomposition temperature of the ammonia compound and the glass transition temperature of the capsule wall is ≥5℃, for example, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, and any value within the range of any two numerical values, preferably ≥20℃, more preferably ≥30℃, most preferably ≥50℃. In this way, it is beneficial to improve the release of ammonia gas of the ammonia compound capsule at a higher temperature, further improve the flame retardation and heat absorption effect, and thus improve the safety of the battery.

[0033] In the present application, the difference between the decomposition temperature of the ammine and the glass transition temperature of the capsule wall means that the glass transition temperature of the capsule wall is lower than the decomposition temperature of the ammine, and the glass transition temperature of the capsule wall is at least 5°C lower than the decomposition temperature of the ammine, preferably at least 20°C lower, more preferably at least 30°C lower, and most preferably at least 50°C lower.

[0034] In the present application, the capsule wall material is stable to the ammine as the capsule core without side reactions.

[0035] In the present application, it is further preferred that the capsule wall is selected from at least one of resin materials decomposed or melted by heat, preferably selected from at least one of melamine formaldehyde resin, urea formaldehyde resin, polyethylene, polyurethane, chitosan, carboxymethyl cellulose, polyvinyl alcohol, polylactic acid, cyclodextrin, polystyrene, and polymethyl methacrylate.

[0036] In the present application, the urea formaldehyde resin includes, but is not limited to, polyurea formaldehyde and the like.

[0037] In the present application, preferably, the average thickness of the capsule wall is 1-100 nm, for example, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, and any value in the range between any two numerical values, preferably 10-50 nm.

[0038] In the present application, the average thickness of the capsule wall mainly affects the content of the effective substance and the gas release capacity, and the thinner the thickness, the higher the proportion of the ammine can be improved, but too thin can easily cause incomplete local coating and affect the stability of the battery.

[0039] In the present application, the average thickness parameter is first measured by an ion cutting sample instrument, i.e. cutting 3 particles under liquid nitrogen cooling, and then at the interface of each particle being cut, 5 different positions are selected to measure the wall thickness by a scanning electron microscope to calculate the average value.

[0040] In the present application, the average particle size of the ammine capsule is 50 nm-5 μm, for example, 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 1 μm, 2 μm, 5 μm, and any value in the range between any two numerical values, preferably 100-800 nm.

[0041] In the present application, the average particle size parameter is measured by a scanning electron microscope.

[0042] In the present application, the source of the ammonia complex capsule has a wide range of selection, as long as the above-mentioned limitations are met. Preferably, the ammonia complex is coated with a resin material to obtain the ammonia complex capsule, wherein the coating temperature is ≤ the decomposition temperature of the ammonia complex, preferably the coating temperature is ≤ (the decomposition temperature of the ammonia complex - 5) °C.

[0043] In the present application, when the battery temperature rises, the ammonia complex as the capsule core is thermally decomposed to produce ammonia, which penetrates the capsule wall and is released to play the heat absorption and flame retardant functions; at the same time, as the temperature continues to rise, the capsule wall also melts or decomposes accordingly, thereby releasing ammonia gas. After the capsule wall decomposes or melts, the ammonia complex gas is released to play a role, and the capsule wall material itself melts or decomposes to produce other small molecules.

[0044] In the present application, preferably, the battery additive can further include a catalyst, and the catalyst catalyzes the oxidation of ammonia gas into nitrogen and water by producing active oxygen; the catalytic mode is selected from electrocatalysis and / or thermal catalysis.

[0045] In a specific embodiment of the present application, the catalyst catalyzes the oxidation of ammonia gas into nitrogen and water by producing active oxygen through catalysis, wherein the catalytic mode is selected from electrocatalysis and / or thermal catalysis, and the above-mentioned positive electrode is an oxidized positive electrode.

[0046] In the present application, under the condition of high temperature and high potential existing in the battery core at the same time (including the scene of heating under overcharging and high SOC), the introduced catalyst significantly catalyzes the positive electrode to produce active oxygen, which reacts with the ammonia gas produced by the decomposition of the ammonia complex, the reducing gas produced by the negative electrode, and the electrolyte with strong reduction to produce harmless gases such as nitrogen and water, which are discharged from the pressure relief valve of the battery, take away heat, reduce the temperature rise of the battery, and inhibit thermal runaway.

[0047] In the present application, preferably, the catalyst is selected from at least one of transition metal oxides, preferably selected from cerium oxide, cerium-zirconium solid solution, lanthanum oxide, praseodymium oxide, neodymium oxide, tricobalt tetroxide, copper-cerium-zirconium solid solution, and copper oxide.

[0048] In the present application, further preferably, the mass ratio of the ammonia complex capsule to the catalyst is 1-150:1, for example, 1:1, 5:1, 9:1, 10:1, 15:1, 20:1, 30:1, 50:1, 60:1, 80:1, 100:1, 120:1, 150:1, and any value in the range between any two numerical values, preferably 5-100:1. In the present application, by adjusting the mass ratio of the above-mentioned two, the heat absorption and flame retardant effect of the battery additive are further adjusted.

[0049] In the present application, preferably, the average particle size of the catalyst is 100-1000 nm, for example, 100 nm, 200 nm, 300 nm, 500 nm, 600 nm, 700 nm, 1000 nm, and any value in the range consisting of any two of the numerical values, preferably 200-700 nm.

[0050] The second aspect of the present application provides a preparation method of a battery additive, the preparation method comprising:

[0051] S1, coating a resin material on the surface of the ammine to obtain an ammine capsule;

[0052] S2, mixing the ammine capsule with a catalyst to obtain a mixture;

[0053] The ammine capsule or the mixture is used as a battery additive.

[0054] In the present application, the above-mentioned ammine, coating material, ammine capsule, and catalyst are in accordance with the above-mentioned limitations, and the present application will not be repeated here.

[0055] In the present application, in step S1, the surface of the ammine, which is intended to be used as the core of the capsule, is coated to form a dense coating layer as the wall of the capsule, thereby obtaining an ammine capsule. Preferably, the temperature of the coating is ≤ the decomposition temperature of the ammine, and further preferably, the temperature of the coating is ≤ (the decomposition temperature of the ammine-5) ℃.

[0056] In one specific embodiment of the present application, the temperature of the coating is ≤ 100 ℃, for example, 100 ℃, 80 ℃, 70 ℃, 60 ℃, 50 ℃, 40 ℃, 25 ℃, and any value in the range consisting of any two of the numerical values, preferably ≤ 80 ℃.

[0057] In the present application, the coating method includes but is not limited to spray drying, photopolymerization curing, thermal polymerization, solvent evaporation, etc.

[0058] In the present application, in step S2, the mixing is intended to mix the ammine capsule and the catalyst uniformly. Preferably, the mixing conditions include: the temperature is 10-40 ℃, preferably 15-25 ℃; the time is 0.1-5 h, preferably 0.1-2 h.

[0059] In the present application, in step S2, the mass ratio of the ammonia complex capsule and the catalyst is 1-150:1, for example, 1:1, 5:1, 9:1, 10:1, 15:1, 20:1, 30:1, 50:1, 60:1, 80:1, 100:1, 120:1, 150:1, and any value in the range between any two numerical values, preferably 5-100:1. In the present application, when the mass ratio of the ammonia complex capsule and the catalyst is less than 1:1, the ammonia complex content is less, and the heat absorption effect cannot be fully played; when the mass ratio of the ammonia complex capsule and the catalyst is greater than 150:1, the proportion of the catalyst is too low, and the effect of catalyzing the conversion of ammonia gas into water cannot be fully played.

[0060] The battery additive provided by the present application is introduced by coating the separator or mixing the positive electrode, especially introduced by coating the separator. The ammonia complex capsule can decompose to produce ammonia gas at a high battery temperature, absorb heat, reduce the battery temperature, and the generated ammonia gas will have a fire retardant effect to inhibit the thermal runaway of the battery.

[0061] The third aspect of the present application provides a separator, wherein the surface of the separator near the positive electrode side is provided with a modified layer, and the modified layer contains the battery additive provided by the first aspect or the battery additive prepared by the preparation method provided by the second aspect.

[0062] In some embodiments of the present application, preferably, the modified layer is composed of the battery additive and a binder. That is, the modified layer is mainly composed of the ammonia complex capsule and the binder, or the modified layer is mainly composed of the ammonia complex capsule, the catalyst and the binder.

[0063] In the present application, further preferably, in the modified layer, the content of the battery additive is ≥50wt%, preferably 95-100wt%, for example, 95wt%, 96wt%, 97wt%, 98wt%, 99wt%, 100wt%, and any value in the range between any two numerical values; the content of the binder is ≤5wt%, preferably 0-5wt%, for example, 5wt%, 4wt%, 3wt%, 2wt%, 1wt%, 0wt%, and any value in the range between any two numerical values.

[0064] In the present application, the binder is selected from at least one of polymethacrylic acid, methyl ester butadiene styrene rubber, benzene propylene emulsion, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane, or a copolymer formed by methyl methacrylate and one or more monomers of methacrylic acid, ethyl acrylic acid, ethyl acrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate.

[0065] In the present application, preferably, the thickness of the modified layer is 0.5-6 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 5 μm, 6 μm, and any value in the range between any two of the values, preferably 1-3 μm.

[0066] In the present application, the thickness parameter is measured by SEM unless otherwise specified.

[0067] In the present application, the modified layer is obtained by coating the water-based slurry containing the battery additive on the positive side of the separator and drying, unless otherwise specified. In the present application, the water-based slurry contains the battery additive, the binder and the solvent. In the present application, the solid content of the water-based slurry is 5-30 wt%.

[0068] The fourth aspect of the present application provides a positive electrode sheet, wherein the active material layer of the positive electrode sheet contains the battery additive provided in the first aspect, or the battery additive prepared by the preparation method provided in the second aspect.

[0069] In the present application, the active material layer is obtained by coating and drying the positive electrode slurry containing the battery additive in sequence, unless otherwise specified. In the present application, the positive electrode slurry contains the positive electrode active material, the conductive agent, the binder, the battery additive and the solvent.

[0070] In the present application, the solid content of the positive electrode slurry is 40-60 wt%.

[0071] In an embodiment of the present application, the active material layer of the positive electrode sheet is composed of the positive electrode active material, the conductive agent, the binder and the ammonia compound capsule; or the active material layer of the positive electrode sheet is composed of the positive electrode active material, the conductive agent, the binder, the ammonia compound capsule and the catalyst.

[0072] In some embodiments of the present application, preferably, the content of the battery additive in the active material layer is 0.1-10 wt%, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 2.5 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%, and any value in the range between any two of the values, preferably 0.5-5 wt%.

[0073] The fifth aspect of the present application provides a lithium ion battery, wherein the lithium ion battery contains the separator provided in the third aspect, and / or the positive electrode sheet provided in the fourth aspect.

[0074] In some embodiments of the present application, preferably, the lithium ion battery contains the separator provided in the third aspect.

[0075] The lithium-ion battery provided by this invention, when subjected to thermal chamber or ARC testing, not only increases the onset temperature of thermal failure and reduces the degree of failure, but also lowers the maximum temperature of thermal runaway, which is beneficial for delaying thermal runaway of individual cells and the spread of battery heat. The threshold for the initial exothermic temperature rise rate in ARC testing is 0.02℃·min. -1 The HWS mode test temperature step is 10℃.

[0076] The present invention will be described in detail below through embodiments.

[0077] The decomposition temperature of [Mg(NH3)6]Cl2 is 120℃; the decomposition temperature of [Co(NH3)6]Cl2 is 240℃; and the decomposition temperature of [Ca(NH3)8]Cl2 is 50℃.

[0078] Hot box test conditions: The sample to be tested is first placed at 100℃ for 0.5h without thermal runaway. Then the temperature is increased to 105℃ and placed for 0.5h. If no runaway occurs, the temperature is increased to 110℃ and placed for 0.5h. The temperature is increased in steps of 5℃ and then held for 0.5h until thermal runaway occurs.

[0079] ARC test: The sample to be tested is heated from 25℃ at a fixed heating rate of 3℃ / min until thermal runaway occurs; where T2 is the thermal runaway temperature of the built-in thermocouple of the battery cell, defined as the temperature when the temperature rise rate of the built-in thermocouple is continuously ≥1℃ / s; T3 is the highest temperature recorded by the built-in thermocouple during the thermal runaway process of the battery cell.

[0080] Overcharge test method: After the battery cell is installed, test it with the clamp. Step ① Charge it to the upper limit voltage at 0.33C, cut off the current at 0.05C, and let it rest for 10 minutes. Step ② Charge it with a constant current of 1C until the battery cell fails or for 4 hours, and record the battery cell failure status.

[0081] In the following examples and comparative examples, when 0.72 wt% of battery additive was incorporated into the positive electrode, the thickness of the modified layer was 2 μm when the same amount of battery additive was coated onto the separator. Therefore, it is assumed that the required mass of battery additive is the same for a positive electrode incorporation of 0.72 wt% and a separator coating thickness of 2 μm.

[0082] Example 1

[0083] (1) Preparation of ammonia capsules

[0084] Microcapsules were prepared by coating polyurea-formaldehyde (glass transition temperature 128-138℃) onto the surface of [Mg(NH3)6]Cl2.

[0085] In a container equipped with stirring device, 1.2 g of urea and 40 mL of aqueous solution containing 2.4 g of formaldehyde were added, after dissolution, pH value was adjusted to 9.5 with triethanolamine, then slowly heated to 65°C for 1 h, to obtain a viscous transparent urea-formaldehyde prepolymer, then n-octanol was added as a surfactant; 14 g of [Mg(NH3)6]Cl2 with an average particle size of 487 nm was added to the prepolymer solution, and a defoaming agent with a mass fraction of 1% was added; the pH value of the emulsion was adjusted to 3.5 with dilute sulfuric acid, and the reaction was slowly heated to 60°C for 1.5 h; after washing, filtering and drying, the suspension containing microcapsules was obtained, the average particle size of the ammonia compound capsule was 504 nm, and the average thickness of the capsule wall was 20 nm.

[0086] (2) Preparation of battery additive

[0087] The above ammonia compound capsule was mixed with a catalyst (Zr 0.1 Ce 0.9 O2, with an average particle size of 495 nm) at a mass ratio of 9:1 to obtain a battery additive A1.

[0088] (3) Assembly of battery

[0089] The above battery additive A1 was dispersed using ultrasonic waves to prepare a water-based slurry with a solid content of 20 wt%; a 9 μm thick separator was used, the negative side of the separator was coated with 2 μm of aluminum oxide, the positive side of the separator was coated with 2 μm of the above battery additive A1 (equivalent to mixing 0.72 wt% in the positive electrode), the positive electrode used a Ni83 positive electrode material, and the positive electrode surface load was 20 mg / cm 2 , the negative electrode used a graphite negative electrode, and the negative electrode surface load was 9 mg / cm 2 , to obtain a soft package battery Q1.

[0090] Example 2

[0091] According to the method of Example 1, except that,

[0092] In step (3), a 9 μm thick separator was used, the negative side of the separator was coated with 2 μm of aluminum oxide, the positive electrode used a Ni83 positive electrode material, and mixed 0.72 wt% (the amount of addition equivalent to coating the positive side of the separator with a thickness of 2 μm) of the above battery additive A1, and the positive electrode surface load was 20 mg / cm 2 , the negative electrode used a graphite negative electrode, and the negative electrode surface load was 9 mg / cm 2 ; the rest was the same, to obtain a soft package battery Q2.

[0093] Example 3

[0094] (1) Preparation of ammonia compound capsule

[0095] [Co(NH3)6]Cl2and [Ca(NH3)8]Cl2are mixed in a mass ratio of 4:5, and then coated with polystyrene (glass transition temperature: 100-120°C):

[0096] [Co(NH3)6]Cl2and [Ca(NH3)8]Cl2are mixed and ball-milled to an average particle size of about 495 nm. Styrene and the above ammonia complex are weighed in a mass ratio of 1:8 in a beaker, and then dissolved by oscillation for 2 h. 4-ABP (4-acryloyloxybenzophenone) is added, dissolved in 4 times the mass of the solute and dispersant in anhydrous ethanol, and then heated and stirred and irradiated with ultraviolet light of wavelength 0.1 μm for 6 h. After the reaction is complete, the solution is dissolved in saturated brine, filtered, and precipitated, and then the product is dried in an oven to form ammonia complex capsules with an average particle size of 511 nm and an average capsule wall thickness of 18 nm.

[0097] (2) Preparation of battery additive

[0098] The above ammonia complex capsules are mixed with a catalyst (copper cerium zirconium solid solution, average particle size: 497 nm) in a mass ratio of 20:1 to obtain a battery additive A3.

[0099] (3) Assembly of battery

[0100] A 9-μm-thick separator is used, the separator negative electrode side is coated with 2 μm of aluminum oxide, the separator positive electrode side is coated with 3 μm of the above battery additive A3, the positive electrode uses a Ni83 positive electrode material, and the negative electrode uses a graphite negative electrode to obtain a soft pack battery Q3.

[0101] Example 4

[0102] The method of Example 1 is followed, except that

[0103] In step (2), no catalyst is added; that is, the ammonia complex capsules of step (1) are directly used as a battery additive A4.

[0104] In step (3), the remaining conditions are the same, and a soft pack battery Q4 is obtained.

[0105] Example 5

[0106] The method of Example 1 is followed, except that

[0107] In step (1), the mass of the urea-formaldehyde prepolymer is increased to 3 times the original amount, and the other steps remain the same, to obtain ammonia complex capsules with an average particle size of 547 nm and an average capsule wall thickness of 55 nm.

[0108] In step (2), the remaining conditions are the same, and a battery additive A5 is obtained.

[0109] In step (3), the remaining conditions were the same, to obtain soft pack battery Q5.

[0110] Example 6

[0111] According to the method of Example 1, except that,

[0112] In step (1), the capsule wall material was replaced with polyvinyl alcohol (glass transition temperature 85°C) to obtain an ammine capsule with an average particle size of 507 nm and an average thickness of the capsule wall of 19 nm;

[0113] In step (2), the remaining conditions were the same, to obtain battery additive A6;

[0114] In step (3), the remaining conditions were the same, to obtain soft pack battery Q6.

[0115] Comparative Example 1

[0116] According to the method of Example 1, except that,

[0117] There was no step (1)-(2);

[0118] In step (3), the separator was coated with 2 μm of aluminum oxide on both the positive electrode side and the negative electrode side;

[0119] The remaining conditions were the same, to obtain soft pack battery DQ1.

[0120] Comparative Example 2

[0121] According to the method of Example 1, except that,

[0122] There was no step (1)-(2), and Mg(OH)2was used as battery additive DA2;

[0123] In step (3), the separator was coated with 2 μm of Mg(OH)2as battery additive DA2;

[0124] The remaining conditions were the same, to obtain soft pack battery DQ2.

[0125] Table 1

[0126]

[0127] From the data in Table 1, compared with Comparative Examples 1-2, the lithium ion battery of Examples 1-6 using the battery additive provided by the application releases the pressure earlier when overcharged, and the decomposition and conversion of the ammonia compound capsule results in the spewed gas containing ammonia, water vapor and other gases, and part of the electrolyte in the battery is taken away during the spewing process, thus resulting in less residual electrolyte in the battery during the subsequent overcharging process, and the battery will not burn and explode. In the battery hot box and ARC tests, the initial temperature T2 of the combustion is increased, the degree of severity is reduced, and the T3 temperature of the battery thermal runaway is reduced, which is conducive to delaying the thermal runaway of the single battery and the thermal spread of the battery.

[0128] The preferred embodiments of the application are described in detail above, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the application and fall within the protection scope of the application.

Claims

1. A battery additive, characterized in that, The battery additive includes: an ammonia compound capsule containing a core and a capsule wall, wherein the core contains an ammonia compound.

2. The battery additive according to claim 1, wherein, The decomposition temperature of the ammonia compound is ≤300℃, preferably 80-300℃, and most preferably 80-150℃; And / or, the ammonium compound is selected from ammonium compounds and / or ammonium salts, preferably from at least one of ammonium carbamate, ammonium chlorate, ammonium carbonate, NH4Cl·3NH3, [Co(NH3)6]Cl3, [Co(NH3)6]Cl2, [Sr(NH3)8]Cl2, [Ca(NH3)8]Cl2 and [Mg(NH3)6]Cl2, as well as mixtures, derivatives, coatings and deammonigenates of the above substances.

3. The battery additive according to claim 1 or 2, wherein, The glass transition temperature of the capsule wall is ≤300℃, preferably 80-300℃, and more preferably 80-150℃; Preferably, the glass transition temperature of the capsule wall is less than or equal to the decomposition temperature of the ammonium compound; Preferably, the difference between the decomposition temperature of the ammonium compound and the glass transition temperature of the capsule wall is ≥5°C, more preferably ≥20°C, more preferably ≥30°C, and most preferably ≥50°C. And / or, the capsule wall is a resin material, preferably selected from at least one of melamine-formaldehyde resin, urea-formaldehyde resin, polyethylene, polyurethane, chitosan, carboxymethyl cellulose, polyvinyl alcohol, polylactic acid, cyclodextrin, polystyrene, and polymethyl methacrylate.

4. The battery additive according to any one of claims 1-3, wherein, The average particle size of the ammonium compound capsule is 50nm-5μm, preferably 100nm-800nm; And / or, the average thickness of the capsule wall is 1-100 nm, preferably 10-50 nm.

5. The battery additive according to any one of claims 1-4, wherein, The battery additive also includes a catalyst, which oxidizes ammonia into nitrogen and water by generating active oxygen; the catalytic method is selected from electrocatalysis and / or thermal catalysis. Preferably, the catalyst is selected from transition metal oxides, and more preferably from at least one of cerium oxide, cerium-zirconium solid solution, lanthanum oxide, praseodymium oxide, neodymium oxide, cobalt tetroxide, copper-cerium-zirconium solid solution, and copper oxide; Preferably, the average particle size of the catalyst is 100-1000 nm, more preferably 200-700 nm; Preferably, in the battery additive, the mass ratio of the ammonia capsule to the catalyst is 1-150:1, more preferably 5-100:

1.

6. A method for preparing a battery additive, characterized in that, The preparation method includes: S1. Coating the surface of the ammonium compound with resin material to obtain an ammonium compound capsule; S2. The ammonium compound capsule is mixed with the catalyst to obtain a mixture; The ammonium compound capsule, or mixture thereof, is used as a battery additive.

7. The preparation method according to claim 6, wherein, In step S1, the coating temperature is ≤ the decomposition temperature of the ammonium compound, preferably the coating temperature is ≤ (the decomposition temperature of the ammonium compound - 5)℃; And / or, in step S2, the mass ratio of the ammonium compound capsule to the catalyst is 1-150:1, preferably 5-100:

1.

8. A diaphragm, characterized in that, The surface of the separator near the positive electrode is provided with a modified layer, and the modified layer contains the battery additive as described in any one of claims 1-5, or the battery additive prepared by the preparation method described in claim 6 or 7. Preferably, the thickness of the modified layer is 0.5-6 μm, and more preferably 1-3 μm; Preferably, the modified layer contains ≥50wt% battery additives.

9. A positive electrode plate, characterized in that, The active material layer of the positive electrode contains the battery additive as described in any one of claims 1-5, or the battery additive prepared by the preparation method described in claim 6 or 7. Preferably, the content of the battery additive in the active material layer is 0.1-10 wt%, more preferably 0.5-5 wt%.

10. A lithium-ion battery, characterized in that, The lithium-ion battery contains the separator as described in claim 8, and / or the positive electrode as described in claim 9; Preferably, the lithium-ion battery contains the separator as described in claim 8.

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