Rechargeable lithium ion battery with high energy density

Abstract

The invention discloses a high-energy-density rechargeable lithium ion battery, and belongs to the technical field of lithium ion battery preparation. The high-energy-density rechargeable lithium ion battery is composed of a positive electrode material, a negative electrode material, an electrolyte and a porous polyethylene film, the positive electrode material is prepared from lithium cobalt oxide, carbon black, polyvinylidene fluoride, N-methyl pyrrolidone and aluminum foil, and the negative electrode material is prepared from lithium cobalt oxide, carbon black, polyvinylidene fluoride, N-methyl pyrrolidone and aluminum foil. The negative electrode material is prepared from graphite, a negative electrode material additive, carbon black, carboxymethyl cellulose, deionized water and copper foil, and the electrolyte is prepared from dimethyl carbonate, lithium hexafluorophosphate and an electrolyte additive. The lithium ion battery prepared by the method has high energy density, excellent cycle performance and safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery preparation, and particularly relates to a rechargeable lithium-ion battery with high energy density. Background Art

[0002] With the rapid development of the global economy and the continuous growth of the population, the energy demand shows an explosive growth trend. Traditional fossil fuels, such as coal, oil, and natural gas, not only have limited resources, but also produce a large amount of carbon dioxide and other greenhouse gases during the combustion process, leading to serious problems such as global warming and environmental pollution. As an efficient and environmentally friendly energy storage technology, lithium-ion batteries have emerged and rapidly developed into the main force in the energy storage field.

[0003] Lithium-ion batteries have significant advantages such as high energy density, long cycle life, low self-discharge rate, and no memory effect, and have been widely used in many fields such as portable electronic devices, electric vehicles, smart grids, and aerospace. Especially in the field of electric vehicles, the high energy density of lithium-ion batteries means longer driving range and lighter battery weight, which is of great significance for improving the competitiveness of electric vehicles and promoting the development of the new energy vehicle industry. In addition, with the large-scale development and utilization of renewable energy, lithium-ion batteries are also increasingly widely used in energy storage power stations, becoming the key means to solve the intermittency and instability problems of renewable energy.

[0004] Patent CN110137467A discloses a lithium-ion battery with high energy density, including a battery cell and a battery film encapsulating the battery cell. The battery cell includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The separator is located between the positive electrode sheet and the negative electrode sheet, and the electrolyte is disposed between the positive electrode sheet and the separator and between the negative electrode sheet and the separator. The positive electrode sheet includes a positive electrode composite material and a positive electrode current collector, and the negative electrode sheet includes a negative electrode composite material and a negative electrode current collector. This invention can reduce weight, improve the first charge and discharge efficiency, and increase the energy density. However, there is still room for improvement in the energy density, cycle performance, and safety of the lithium-ion battery prepared by this method. Summary of the Invention

[0005] The purpose of the present invention is to provide a lithium-ion battery with high energy density for solving the technical problems of poor energy density, cycle performance, and safety of lithium-ion batteries in the prior art.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The present invention provides a rechargeable lithium-ion battery with a high energy density, which is composed of a positive electrode material, a negative electrode material, an electrolyte, and a porous polyethylene film. Among them, the positive electrode material is prepared from lithium cobaltate, carbon black, polyvinylidene fluoride, N-methylpyrrolidone, and aluminum foil; the negative electrode material is prepared from graphite, a negative electrode material additive, carbon black, carboxymethyl cellulose, deionized water, and copper foil; and the electrolyte is prepared from dimethyl carbonate, lithium hexafluorophosphate, and an electrolyte additive.

[0008] Preferably, the preparation method of the negative electrode material additive includes the following steps:

[0009] Q1: 3,5-dibromoaniline, 1-bromohexane, tetrabutylammonium bromide, and potassium iodide are sequentially added to a container, nitrogen is introduced, then sodium hydroxide and acetonitrile are added, and the mixture is stirred for reaction, extracted, washed, dried, and purified to obtain Compound 1; Compound 1, bis(pinacolato)diboron, potassium acetate, and DPPF dichloropalladium are sequentially added to a container, nitrogen is introduced, then N,N-dimethylformamide is added, and the mixture is stirred for reaction. After the reaction is completed, it is extracted, washed, dried, and purified to obtain Compound 2;

[0010] Q2: 2-bromophenazine, Compound 2, potassium carbonate, and tetrakis(triphenylphosphine)palladium are sequentially added to a container. After nitrogen is introduced, tetrahydrofuran, deionized water, and toluene are added, and the mixture is stirred for reaction in an oil bath, dried, and purified to obtain Compound 3; Compound 3 is added to a container filled with ethanol, nitrogen is introduced, and then distilled water dissolving sodium dithionite is added to the container, and the mixture is heated for reaction. After the reaction is completed, it is cooled, washed, filtered by suction, and dried to obtain Compound 4;

[0011] Q3: Compound 4, 2-bromoanthraquinone, 2-bis(cyclohexylphosphino)-2',4',6'-triisopropylbiphenyl, sodium tert-butoxide, and tris(dibenzylideneacetone)palladium are added to a container. After nitrogen is introduced, 1,4-dioxane is added, the container is sealed, and the mixture is heated and stirred magnetically for reaction. After the reaction is completed, it is cooled, filtered by suction, washed, and dried to obtain the negative electrode material additive.

[0012] In the above process, the synthesis reaction formula of the negative electrode material additive is as follows:

[0013]

[0014] The results of mass spectrometry analysis for Compound 1 are as follows: m / z: 419.06 (100.0%), 417.07 (51.4%), 421.06 (48.6%), 420.07 (19.8%), 418.07 (10.2%), 422.07 (9.7%), 421.07 (1.9%), 419.07 (1.0%); the results of mass spectrometry analysis for Compound 2 are as follows: m / z: 513.42 (100.0%), 512.42 (42.7%), 514.42 (28.9%), 511.42 (5.3%), 515.42 (5.2%), 514.43 (2.3%), 512.43 (1.8%); the results of mass spectrometry analysis for Compound 3 are as follows: m / z: 617.35 (100.0%), 618.36 (45.9%), 619.36 (10.3%), 618.35 (1.8%), 620.36 (1.7%); the results of mass spectrometry analysis for Compound 4 are as follows: m / z: 625.41 (100.0%), 626.42 (46.0%), 627.42 (10.3%), 626.41 (1.8%), 628.42 (1.6%); the results of mass spectrometry analysis for the additive of the negative electrode material are as follows: m / z: 1450.56 (100.0%), 1449.56 (92.7%), 1451.57 (54.2%), 1452.57 (21.1%), 1453.57 (5.8%), 1451.56 (1.8%), 1454.58 (1.3%), 1450.57 (1.1%).

[0015] Preferably, in the Q1, the dosage ratio of 3,5-dibromoaniline, 1-bromohexane, tetrabutylammonium bromide, potassium iodide, sodium hydroxide and acetonitrile is (6.218 - 6.668) g : (1.024 - 1.232) g : (0.782 - 0.866) g : (0.342 - 0.506) g : (8.564 - 8.844) g : (18 - 24) mL, the stirring reaction temperature is 60 - 80 °C, and the reaction time is 6 - 8 h; the dosage ratio of Compound 1, bis(pinacolato)diboron, potassium acetate, DPPF dichloropalladium and N,N-dimethylformamide is (1.046 - 1.15) g : (1.11 - 1.55) g : (1.212 - 1.366) g : (0.15 - 0.23) g : (20 - 30) mL, the stirring reaction temperature is 90 - 110 °C, and the reaction time is 6 - 8 h.

[0016] Preferably, in Q2, the dosage ratio of 2-bromophenazine, Compound 2, potassium carbonate, tetrakis(triphenylphosphine)palladium, tetrahydrofuran, deionized water and toluene is (0.04 - 0.06) g : (0.03 - 0.07) g : (0.06 - 0.102) g : (0.008 - 0.014) g : (8 - 11) mL : (4 - 8) mL : (8 - 10) mL. The oil bath stirring temperature is 90 - 105 °C, and the reaction time is 20 - 24 h; the dosage ratio of Compound 3, ethanol, sodium dithionite and distilled water is (3.1 - 4.1) g : (45 - 55) mL : (31.2 - 37.6) g : (100 - 120) mL. The heating reaction temperature is 80 - 90 °C, and the reaction time is 1 - 2 h.

[0017] Preferably, in Q3, the dosage ratio of Compound 4, 2-bromoanthraquinone, 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl, sodium tert-butoxide, tris(dibenzylideneacetone)palladium and 1,4-dioxane is (0.166 - 0.208) g : (0.552 - 0.654) g : (0.111 - 0.117) g : (0.188 - 0.234) g : (0.05 - 0.07) g : (18 - 22) mL. The heating magnetic stirring reaction temperature is 100 - 120 °C, and the reaction time is 60 - 80 h.

[0018] Preferably, the preparation method of the electrolyte additive includes the following steps:

[0019] S1: Add phosphonyl chloride trimer, N-hydroxyethylaniline, triethylamine and chlorobenzene into a container equipped with a thermometer, a mechanical stirrer and a reflux condenser, and carry out an oil bath heating and stirring reaction;

[0020] S2: After the reaction is completed, cool down, introduce ammonia gas, filter, wash, dry, carry out polycondensation, cool, dissolve, filter, wash, and dry to obtain the electrolyte additive.

[0021] In the above process, using phosphonyl chloride trimer and N-hydroxyethylaniline as raw materials, triethylamine as a catalyst and an acid-binding agent, through the reaction of phosphonyl chloride trimer and N-hydroxyethylaniline, followed by ammoniation and then polycondensation to obtain the electrolyte additive.

[0022] Preferably, in S1, the dosage ratio of phosphonyl chloride trimer, N-hydroxyethyl aniline, triethylamine and chlorobenzene is (15 - 19.8) g : (6.02 - 6.24) g : (6.48 - 6.64) g : (58 - 64) g, the oil bath heating temperature is 90 - 95 °C, and the reaction time is 8 - 12 h; in S2, the temperature is lowered to -5 °C to 5 °C, ammonia gas is introduced for 20 - 24 h, the polycondensation temperature is 160 - 190 °C, the time is 10 - 30 min, it is added to deionized water for dissolution, washed with deionized water, and the drying temperature is 90 - 110 °C, and the time is 12 - 18 h.

[0023] Preferably, the preparation method of the lithium-ion battery includes the following steps:

[0024] Step 1: Mix lithium cobaltate, carbon black and polyvinylidene fluoride, then add N-methylpyrrolidone and stir to obtain a positive electrode paste. The positive electrode paste is evenly coated on aluminum foil, dried, pressed into tablets, and cut to obtain a positive electrode material.

[0025] Step 2: Mix graphite and a negative electrode material additive, then mix with carbon black and carboxymethyl cellulose, add deionized water and stir to obtain a negative electrode paste. The negative electrode paste is evenly coated on copper foil, dried, pressed into tablets, and cut to obtain a negative electrode material.

[0026] Step 3: Mix dimethyl carbonate and lithium hexafluorophosphate, then add an electrolyte additive, stir evenly, and filter to obtain an electrolyte.

[0027] Step 4: Stack the positive electrode material, porous polyethylene film and negative electrode material to obtain an electric core, then install the electric core into a metal shell, and then inject the electrolyte into the battery and seal it to obtain a rechargeable lithium-ion battery with high energy density.

[0028] Preferably, in Step 1, the mass ratio of lithium cobaltate, carbon black and polyvinylidene fluoride is (88 - 92) : (4 - 6) : (3 - 7); in Step 2, the mass ratio of graphite, negative electrode material additive, carbon black and carboxymethyl cellulose is (86 - 89) : (2.58 - 2.67) : (2 - 8) : (3 - 7); in Step 3, the mass ratio of dimethyl carbonate, lithium hexafluorophosphate and electrolyte additive is (30 - 53) : (8 - 13) : (0.24 - 0.39).

[0029] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are:

[0030] 1. First, using 3,5-dibromoaniline, 1-bromohexane, bis(pinacolato)diboron, 2-bromophenazine, and 2-bromoanthraquinone as raw materials, an additive for the negative electrode material is prepared. Subsequently, using phosphoryl chloride trimer and N-hydroxyethylaniline as raw materials, an additive for the electrolyte is prepared. Adding them to the preparation process of lithium-ion batteries can effectively improve the energy density, cycle performance, and safety of lithium-ion batteries.

[0031] 2. Applying the obtained additive for the negative electrode material to the preparation process of lithium-ion batteries can effectively improve the energy density and cycle performance of the batteries. The nitrogen atoms contained in the additive for the negative electrode material have lone pairs of electrons, which can form coordination bonds with lithium ions, providing additional lithium-ion storage sites. The presence of the anthraquinone structure provides stable lithium-ion storage sites, further increasing the capacity of the negative electrode material. The presence of the additive for the negative electrode material can provide more lithium-ion storage sites, significantly enhancing the theoretical capacity of the negative electrode material. At the same time, the conjugate π-electron system of the additive for the negative electrode material can move freely within and between molecules, forming a continuous electron conduction path. It can also reduce the internal resistance of the electrode and improve the electron transfer efficiency, thereby increasing the energy density. The rigid molecular structure of the additive for the negative electrode material can effectively relieve volume changes during the lithium-ion insertion / extraction process, reduce the pulverization and shedding of the electrode material, and enhance the mechanical stability of the electrode. The presence of this substance also helps to form a stable solid electrolyte interface film on the electrode surface, effectively isolating the electrode and the electrolyte, improving the cycle stability of the battery, and extending the cycle life of the battery.

[0032] 3. Applying the obtained additive for the electrolyte to the preparation process of lithium-ion batteries can effectively improve the safety of the batteries. The conjugate structure of the nitrogen-phosphorus alternating six-membered ring can effectively disperse the heat generated inside the battery, prevent local overheating, and enhance its thermal stability. The synergistic effect of nitrogen and phosphorus elements can effectively inhibit combustion and prevent thermal runaway of the battery. The molecular structure of the additive for the electrolyte does not hinder the transport of lithium ions. The contained conjugate structure can also interact with lithium ions through polar bonds, promoting the rapid diffusion of lithium ions. At the same time, the additive for the electrolyte has high electrochemical stability within the working voltage range of the battery and will not undergo oxidation or reduction reactions, ensuring the efficiency and safety of the battery during charge and discharge. Detailed implementation manners

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Example 1: This example discloses a preparation method of a negative electrode material additive, including the following steps:

[0035] Q1: Add 6.439 g of 3,5-dibromoaniline, 1.128 g of 1-bromohexane, 0.828 g of tetrabutylammonium bromide, and 0.424 g of potassium iodide into a container in sequence, introduce nitrogen, then add 8.651 g of sodium hydroxide and 21 mL of acetonitrile, stir and react at 70 °C for 8 h, extract, wash, dry, and purify to obtain Compound 1; Add 1.098 g of Compound 1, 1.33 g of bis(pinacolato)diboron, 1.289 g of potassium acetate, and 0.19 g of DPPF dichloropalladium into a container in sequence, introduce nitrogen, then add 25 mL of N,N-dimethylformamide, stir and react at 100 °C for 8 h. After the reaction ends, extract, wash, dry, and purify to obtain Compound 2;

[0036] Q2: Add 0.05 g of 2-bromophenazine, 0.05 g of Compound 2, 0.081 g of potassium carbonate, and 0.011 g of tetrakis(triphenylphosphine)palladium into a container in sequence. After introducing nitrogen, add 9.5 mL of tetrahydrofuran, 6 mL of deionized water, and 9 mL of toluene, stir and react in an oil bath at 95 °C for 24 h, dry, and purify to obtain Compound 3; Add 3.6 g of Compound 3 into a container containing 50 mL of ethanol, introduce nitrogen, then add 110 mL of distilled water dissolving 34.3 g of sodium dithionite into the container, heat and react at 90 °C for 2 h. After the reaction ends, cool, wash, filter by suction, and dry to obtain Compound 4;

[0037] Q3: Add 0.187 g of Compound 4, 0.603 g of 2-bromoanthraquinone, 0.114 g of 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl, 0.216 g of sodium tert-butoxide, and 0.06 g of tris(dibenzylideneacetone)palladium into a container. After introducing nitrogen, add 20 mL of 1,4-dioxane, seal, heat and stir magnetically at 110 °C for 72 h. After the reaction ends, cool, filter by suction, wash, and dry to obtain the negative electrode material additive.

[0038] This example discloses a preparation method of an electrolyte additive, including the following steps:

[0039] S1: Add 17.4 g of phosphonyl chloride trimer, 6.13 g of N-hydroxyethylaniline, 6.56 g of triethylamine, and 62 g of chlorobenzene into a container equipped with a thermometer, a mechanical stirrer, and a reflux condenser, heat and stir in an oil bath at 90 °C for 12 h;

[0040] S2: After the reaction is completed, cool down to 5 °C, introduce ammonia gas for 24 h, filter, wash, dry, perform polycondensation at 190 °C for 30 min, cool down, add it to deionized water for dissolution, filter, wash with deionized water, and dry at 100 °C for 18 h to obtain an electrolyte additive.

[0041] This example discloses a preparation method of a lithium-ion battery, including the following steps:

[0042] Step 1: Mix 90 g of lithium cobaltate, 5 g of carbon black, and 5 g of polyvinylidene fluoride, then add 150 mL of N-methylpyrrolidone and stir to obtain a positive electrode paste. Coating the positive electrode paste evenly on aluminum foil, drying, pressing, and cutting to obtain a positive electrode material;

[0043] Step 2: Mix 87.5 g of graphite and 2.64 g of a negative electrode material additive, then mix with 5 g of carbon black and 5 g of carboxymethyl cellulose, add 80 mL of deionized water and stir to obtain a negative electrode paste. Coating the negative electrode paste evenly on copper foil, drying, pressing, and cutting to obtain a negative electrode material;

[0044] Step 3: Mix 41.5 g of dimethyl carbonate and 10.5 g of lithium hexafluorophosphate, then add 0.28 g of an electrolyte additive, stir evenly, and filter to obtain an electrolyte;

[0045] Step 4: Stack the positive electrode material, porous polyethylene film, and negative electrode material to obtain an electric core, then place the electric core into a metal shell, and then inject the electrolyte into the battery and seal it to obtain a rechargeable lithium-ion battery with a high energy density.

[0046] Example 2: This example discloses a preparation method of a negative electrode material additive, including the following steps:

[0047] Q1: Add 6.218 g of 3,5-dibromoaniline, 1.024 g of 1-bromohexane, 0.782 g of tetrabutylammonium bromide, and 0.342 g of potassium iodide into a container in sequence, introduce nitrogen gas, then add 8.564 g of sodium hydroxide and 18 mL of acetonitrile, stir and react at 70 °C for 8 h, extract, wash, dry, and purify to obtain Compound 1; Add 1.046 g of Compound 1, 1.11 g of bis(pinacolato)diboron, 1.212 g of potassium acetate, and 0.15 g of DPPF dichloropalladium into a container in sequence, introduce nitrogen gas, then add 20 mL of N,N-dimethylformamide, stir and react at 100 °C for 8 h. After the reaction is completed, extract, wash, dry, and purify to obtain Compound 2;

[0048] Q2: 0.04 g of 2-bromophenazine, 0.03 g of compound 2, 0.06 g of potassium carbonate, and 0.008 g of tetrakis(triphenylphosphine)palladium were successively added to a container. After purging with nitrogen, 8 mL of tetrahydrofuran, 4 mL of deionized water, and 8 mL of toluene were added. The mixture was stirred and reacted in an oil bath at 95 °C for 24 h, then dried and purified to obtain compound 3. 3.1 g of compound 3 was added to a container containing 45 mL of ethanol. After purging with nitrogen, 100 mL of distilled water dissolving 31.2 g of sodium dithionite was added to the container. The mixture was heated and reacted at 90 °C for 2 h. After the reaction, it was cooled, washed, filtered by suction, and dried to obtain compound 4;

[0049] Q3: 0.166 g of compound 4, 0.552 g of 2-bromoanthraquinone, 0.111 g of 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl, 0.188 g of sodium tert-butoxide, and 0.05 g of tris(dibenzylideneacetone)palladium were added to a container. After purging with nitrogen, 18 mL of 1,4-dioxane was added, and the container was sealed. The mixture was heated and magnetically stirred at 110 °C for 72 h. After the reaction, it was cooled, filtered by suction, washed, and dried to obtain the anode material additive.

[0050] This example discloses a preparation method of an electrolyte additive, including the following steps:

[0051] S1: 15 g of phosphonyl chloride trimer, 6.02 g of N-hydroxyethylaniline, 6.48 g of triethylamine, and 58 g of chlorobenzene were added to a container equipped with a thermometer, a mechanical stirrer, and a reflux condenser. The mixture was heated and stirred in an oil bath at 90 °C for 12 h;

[0052] S2: After the reaction, the temperature was lowered to 5 °C, ammonia gas was introduced for 24 h, then filtered, washed, and dried. It was polycondensed at 190 °C for 30 min, cooled, added to deionized water for dissolution, filtered, washed with deionized water, and dried at 100 °C for 18 h to obtain the electrolyte additive.

[0053] This example discloses a preparation method of a lithium-ion battery, including the following steps:

[0054] Step 1: 88 g of lithium cobaltate, 4 g of carbon black, and 3 g of polyvinylidene fluoride were mixed, then 150 mL of N-methylpyrrolidone was added for stirring to obtain the positive electrode paste. The positive electrode paste was uniformly coated on aluminum foil, dried, pressed into tablets, and cut to obtain the positive electrode material;

[0055] Step 2: 86 g of graphite and 2.58 g of the anode material additive were mixed, then mixed with 2 g of carbon black and 3 g of carboxymethyl cellulose, and 80 mL of deionized water was added for stirring to obtain the negative electrode paste. The negative electrode paste was uniformly coated on copper foil, dried, pressed into tablets, and cut to obtain the negative electrode material;

[0056] Step 3: Mix 30 g of dimethyl carbonate and 8 g of lithium hexafluorophosphate, then add 0.24 g of electrolyte additive. After stirring evenly, filter to obtain the electrolyte;

[0057] Step 4: Stack the positive electrode material, porous polyethylene film, and negative electrode material to obtain an electrode core. Then, place the electrode core into a metal shell. Subsequently, inject the electrolyte into the battery and seal it to obtain a rechargeable lithium-ion battery with high energy density.

[0058] Example 3: This example discloses a preparation method of a negative electrode material additive, which includes the following steps:

[0059] Q1: Add 6.668 g of 3,5-dibromoaniline, 1.232 g of 1-bromohexane, 0.866 g of tetrabutylammonium bromide, and 0.506 g of potassium iodide into a container in sequence. Introduce nitrogen, then add 8.844 g of sodium hydroxide and 24 mL of acetonitrile. Stir and react at 70 °C for 8 h, extract, wash, dry, and purify to obtain Compound 1; Add 1.15 g of Compound 1, 1.55 g of bis(pinacolato)diboron, 1.366 g of potassium acetate, and 0.23 g of DPPF dichloropalladium into a container in sequence. Introduce nitrogen, then add 30 mL of N,N-dimethylformamide. Stir and react at 100 °C for 8 h. After the reaction, extract, wash, dry, and purify to obtain Compound 2;

[0060] Q2: Add 0.06 g of 2-bromophenazine, 0.07 g of Compound 2, 0.102 g of potassium carbonate, and 0.014 g of tetrakis(triphenylphosphine)palladium into a container in sequence. After introducing nitrogen, add 11 mL of tetrahydrofuran, 8 mL of deionized water, and 10 mL of toluene. Stir and react in an oil bath at 95 °C for 24 h, dry, and purify to obtain Compound 3; Add 4.1 g of Compound 3 into a container containing 55 mL of ethanol. Introduce nitrogen, then add 120 mL of distilled water dissolving 37.6 g of sodium dithionite into the container. Heat and react at 90 °C for 2 h. After the reaction, cool, wash, filter by suction, and dry to obtain Compound 4;

[0061] Q3: Add 0.208 g of Compound 4, 0.654 g of 2-bromoanthraquinone, 0.117 g of 2-bis(cyclohexylphosphino)-2',4',6'-triisopropylbiphenyl, 0.234 g of sodium tert-butoxide, and 0.07 g of tris(dibenzylideneacetone)palladium into a container. After introducing nitrogen, add 22 mL of 1,4-dioxane, seal, and heat and stir magnetically at 110 °C for 72 h. After the reaction, cool, filter by suction, wash, and dry to obtain the negative electrode material additive.

[0062] This example discloses a preparation method of an electrolyte additive, which includes the following steps:

[0063] S1: Add 19.8 g of phosphonyl chloride trimer, 6.24 g of N-hydroxyethyl aniline, 6.64 g of triethylamine, and 64 g of chlorobenzene into a container equipped with a thermometer, a mechanical stirrer, and a reflux condenser. Heat and stir the reaction in an oil bath at 90 °C for 12 h;

[0064] S2: After the reaction ends, cool down to 5 °C, introduce ammonia gas for 24 h, filter, wash, dry, carry out polycondensation at 190 °C for 30 min, cool down, add it to deionized water for dissolution, filter, wash with deionized water, and dry at 100 °C for 18 h to obtain the electrolyte additive.

[0065] This example discloses a preparation method of a lithium-ion battery, including the following steps:

[0066] Step 1: Mix 92 g of lithium cobaltate, 6 g of carbon black, and 7 g of polyvinylidene fluoride, then add 150 mL of N-methylpyrrolidone and stir to obtain the positive electrode slurry. Coat the positive electrode slurry evenly on the aluminum foil, dry, press into tablets, and cut to obtain the positive electrode material;

[0067] Step 2: Mix 89 g of graphite and 2.67 g of negative electrode material additive, then mix it with 8 g of carbon black and 7 g of carboxymethyl cellulose, add 80 mL of deionized water and stir to obtain the negative electrode slurry. Coat the negative electrode slurry evenly on the copper foil, dry, press into tablets, and cut to obtain the negative electrode material;

[0068] Step 3: Mix 53 g of dimethyl carbonate and 13 g of lithium hexafluorophosphate, then add 0.39 g of electrolyte additive, stir evenly, and filter to obtain the electrolyte;

[0069] Step 4: Stack the positive electrode material, porous polyethylene film, and negative electrode material to obtain the battery cell, then install the battery cell into a metal shell, and then inject the electrolyte into the battery and seal it to obtain a rechargeable lithium-ion battery with high energy density.

[0070] Example 4: This example discloses a preparation method of a negative electrode material additive, including the following steps:

[0071] Q1: 6.371 g of 3,5-dibromoaniline, 1.117 g of 1-bromohexane, 0.793 g of tetrabutylammonium bromide, and 0.387 g of potassium iodide were successively added to a container. Nitrogen was introduced, and then 8.593 g of sodium hydroxide and 19 mL of acetonitrile were added. The mixture was stirred at 70 °C for 8 h, followed by extraction, washing, drying, and purification to obtain Compound 1. 1.067 g of Compound 1, 1.22 g of bis(pinacolato)diboron, 1.247 g of potassium acetate, and 0.17 g of DPPF dichloropalladium were successively added to a container. Nitrogen was introduced, and then 22 mL of N,N-dimethylformamide was added. The mixture was stirred at 100 °C for 8 h. After the reaction, extraction, washing, drying, and purification were carried out to obtain Compound 2;

[0072] Q2: 0.045 g of 2-bromophenazine, 0.04 g of Compound 2, 0.07 g of potassium carbonate, and 0.009 g of tetrakis(triphenylphosphine)palladium were successively added to a container. After introducing nitrogen, 9 mL of tetrahydrofuran, 5 mL of deionized water, and 8.5 mL of toluene were added. The mixture was stirred at 95 °C in an oil bath for 24 h, followed by drying and purification to obtain Compound 3. 3.2 g of Compound 3 was added to a container containing 48 mL of ethanol. Nitrogen was introduced, and then 105 mL of distilled water dissolving 33.8 g of sodium dithionite was added to the container. The mixture was heated at 90 °C for 2 h. After the reaction, it was cooled, washed, filtered by suction, and dried to obtain Compound 4;

[0073] Q3: 0.171 g of Compound 4, 0.581 g of 2-bromoanthraquinone, 0.112 g of 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl, 0.191 g of sodium tert-butoxide, and 0.055 g of tris(dibenzylideneacetone)palladium were added to a container. After introducing nitrogen, 19 mL of 1,4-dioxane was added, and the container was sealed. The mixture was heated with magnetic stirring at 110 °C for 72 h. After the reaction, it was cooled, filtered by suction, washed, and dried to obtain the anode material additive.

[0074] This example discloses a preparation method of an electrolyte additive, including the following steps:

[0075] S1: 16.7 g of phosphonyl chloride trimer, 6.07 g of N-hydroxyethylaniline, 6.51 g of triethylamine, and 59 g of chlorobenzene were added to a container equipped with a thermometer, a mechanical stirrer, and a reflux condenser. The mixture was heated and stirred at 90 °C in an oil bath for 12 h;

[0076] S2: After the reaction, the temperature was lowered to 5 °C, and ammonia gas was introduced for 24 h. The mixture was filtered, washed, and dried, then polycondensed at 190 °C for 30 min, cooled, dissolved in deionized water, filtered, washed with deionized water, and dried at 100 °C for 18 h to obtain the electrolyte additive.

[0077] This example discloses a preparation method of a lithium-ion battery, including the following steps:

[0078] Step 1: Mix 89 g of lithium cobaltate, 4.5 g of carbon black, and 4 g of polyvinylidene fluoride, then add 150 mL of N-methylpyrrolidone and stir to obtain a positive electrode paste. Coat the positive electrode paste evenly on aluminum foil, dry, press into sheets, and cut to obtain a positive electrode material.

[0079] Step 2: Mix 87 g of graphite and 2.59 g of negative electrode material additive, then mix with 3 g of carbon black and 4 g of carboxymethyl cellulose, add 80 mL of deionized water and stir to obtain a negative electrode paste. Coat the negative electrode paste evenly on copper foil, dry, press into sheets, and cut to obtain a negative electrode material.

[0080] Step 3: Mix 35 g of dimethyl carbonate and 9 g of lithium hexafluorophosphate, then add 0.26 g of electrolyte additive, stir evenly, filter to obtain an electrolyte.

[0081] Step 4: Stack the positive electrode material, porous polyethylene film, and negative electrode material to obtain an electrode core, then place the electrode core into a metal shell, and then inject the electrolyte into the battery and seal to obtain a rechargeable lithium-ion battery with high energy density.

[0082] Example 5: This example discloses a preparation method of a negative electrode material additive, including the following steps:

[0083] Q1: Add 6.528 g of 3,5-dibromoaniline, 1.118 g of 1-bromohexane, 0.841 g of tetrabutylammonium bromide, and 0.483 g of potassium iodide into a container in sequence, introduce nitrogen, then add 8.715 g of sodium hydroxide and 23 mL of acetonitrile, stir and react at 70 °C for 8 h, extract, wash, dry, and purify to obtain Compound 1; add 1.108 g of Compound 1, 1.44 g of bis(pinacolato)diboron, 1.328 g of potassium acetate, and 0.21 g of DPPF dichloropalladium into a container in sequence, introduce nitrogen, then add 28 mL of N,N-dimethylformamide, stir and react at 100 °C for 8 h. After the reaction, extract, wash, dry, and purify to obtain Compound 2;

[0084] Q2: Add 0.055 g of 2-bromophenazine, 0.06 g of Compound 2, 0.091 g of potassium carbonate, and 0.013 g of tetrakis(triphenylphosphine)palladium into a container in sequence, introduce nitrogen, then add 10 mL of tetrahydrofuran, 7 mL of deionized water, and 9.5 mL of toluene, stir and react in an oil bath at 95 °C for 24 h, dry, and purify to obtain Compound 3; add 3.8 g of Compound 3 into a container containing 52 mL of ethanol, introduce nitrogen, then add 115 mL of distilled water dissolving 36.5 g of sodium dithionite into the container, heat and react at 90 °C for 2 h. After the reaction, cool, wash, filter by suction, and dry to obtain Compound 4;

[0085] Q3: Add 0.193 g of Compound 4, 0.623 g of 2-bromoanthraquinone, 0.116 g of 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl, 0.223 g of sodium tert-butoxide, and 0.065 g of tris(dibenzylideneacetone)palladium into a container. After introducing nitrogen, add 21 mL of 1,4-dioxane, seal it, and heat with magnetic stirring at 110 °C for 72 h. After the reaction is completed, cool it, filter it by suction, wash it, and dry it to obtain the additive for the negative electrode material.

[0086] This example discloses a preparation method of an electrolyte additive, including the following steps:

[0087] S1: Add 18.3 g of phosphonyl chloride trimer, 6.18 g of N-hydroxyethylaniline, 6.61 g of triethylamine, and 61 g of chlorobenzene into a container equipped with a thermometer, a mechanical stirrer, and a reflux condenser. Heat and stir the reaction in an oil bath at 90 °C for 12 h;

[0088] S2: After the reaction is completed, cool the temperature to 5 °C, introduce ammonia gas for 24 h, filter it, wash it, dry it, carry out polycondensation at 190 °C for 30 min, cool it, add it to deionized water for dissolution, filter it, wash it with deionized water, and dry it at 100 °C for 18 h to obtain the electrolyte additive.

[0089] This example discloses a preparation method of a lithium-ion battery, including the following steps:

[0090] Step 1: Mix 91 g of lithium cobaltate, 5.5 g of carbon black, and 6 g of polyvinylidene fluoride, then add 150 mL of N-methylpyrrolidone and stir to obtain the positive electrode slurry. Coat the positive electrode slurry evenly on the aluminum foil, dry it, press it into tablets, and cut it to obtain the positive electrode material;

[0091] Step 2: Mix 88 g of graphite and 2.66 g of the additive for the negative electrode material, then mix it with 7 g of carbon black and 6 g of carboxymethyl cellulose, add 80 mL of deionized water and stir to obtain the negative electrode slurry. Coat the negative electrode slurry evenly on the copper foil, dry it, press it into tablets, and cut it to obtain the negative electrode material;

[0092] Step 3: Mix 48 g of dimethyl carbonate and 11 g of lithium hexafluorophosphate, then add 0.34 g of the electrolyte additive, stir evenly, and filter to obtain the electrolyte;

[0093] Step 4: Stack the positive electrode material, the porous polyethylene film, and the negative electrode material to obtain the battery cell, then put the battery cell into the metal shell, and then inject the electrolyte into the battery and seal it to obtain a rechargeable lithium-ion battery with high energy density.

[0094] Comparative Example 1: Compared with Example 1, in the process of preparing a rechargeable lithium-ion battery with high energy density, no negative electrode material additive was added in Comparative Example 1, and other conditions remained unchanged.

[0095] Comparative Example 2: Compared with Example 1, in the process of preparing a rechargeable lithium-ion battery with high energy density, no electrolyte additive was added in Comparative Example 2, and other conditions remained unchanged.

[0096] Experimental Example: The energy density and cycle performance of the rechargeable lithium-ion batteries prepared in Examples 1-5 and Comparative Examples 1-2 were tested. The energy density test method was as follows: The prepared sample was charged at a constant current of 0.3C and a constant voltage of 4.25V in a 25°C constant temperature oven until the voltage reached 4.25V, with a cut-off current of 0.05C. After standing for 10 minutes, it was discharged at a constant current of 0.3C to 2.5V, and then stood for 10 minutes. The operation was repeated, and the battery energy density was recorded. The test method for the cycle performance was as follows: The prepared sample was charged at a constant current of 1C and a constant voltage of 4.25V until the voltage reached 4.25V, with a cut-off current of 0.05C. After standing for 10 minutes, it was discharged at a constant current of 1C to 2.5V, and then stood for 10 minutes. The discharge cycle was repeated 120 times. The prepared sample was charged at a current of 0.3C to a voltage of 4.25V, with a cut-off current of 0.05C. A steel needle with a diameter of 3 mm was used to completely penetrate into the center of the battery at a speed of 50 mm / s and maintain the penetrated state. The experimental phenomenon was observed until the surface temperature of the battery decreased by 50°C, and the test was terminated. The prepared sample was placed in a drying oven and heated to 160°C and maintained for 30 minutes. The test results are shown in Table 1:

[0097] Table 1

[0098] Project <![CDATA[Energy density Wh·kg -1 > Capacity retention rate / % Needle-punching test Furnace temperature experiment Example 1 337 97.4 No fire No fire Example 2 335 97.1 No fire No fire Example 3 328 96.8 No fire No fire Example 4 324 96.5 No fire No fire Example 5 327 96.4 No fire No fire Comparative example 1 295 92.7 No fire No fire Comparative example 2 325 96.5 Fire Fire

[0099] It can be seen from the test results in Table 1 that the rechargeable lithium-ion batteries prepared in Examples 1-5 of the present invention have high energy density, excellent cycle stability and safety. By comparing Comparative Example 1 with Examples 1-5, it can be known that the addition of the negative electrode material additive can effectively improve the energy density and cycle stability of the rechargeable lithium-ion battery; by comparing Comparative Example 2 with Examples 1-5, it can be known that the addition of the electrolyte additive can effectively improve the safety of the rechargeable lithium-ion battery.

[0100] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

[0101] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A high energy density rechargeable lithium ion battery, characterized in that: The invention is composed of a positive electrode material, a negative electrode material, an electrolyte and a porous polyethylene film, wherein the positive electrode material is prepared from lithium cobalt oxide, carbon black, polyvinylidene fluoride, N-methylpyrrolidone and aluminum foil, the negative electrode material is prepared from graphite, a negative electrode material additive, carbon black, carboxymethyl cellulose, deionized water and copper foil, and the electrolyte is prepared from dimethyl carbonate, lithium hexafluorophosphate and an electrolyte additive.

2. The high energy density rechargeable lithium ion battery according to claim 1, characterized in that: The method for preparing the negative electrode material additive comprises the following steps: Q1: 3,5-dibromoaniline, 1-bromohexane, tetrabutylammonium bromide and potassium iodide were added to a container in sequence, nitrogen was introduced, and then sodium hydroxide and acetonitrile were added, stirred for reaction, extracted, washed, dried and purified to obtain compound 1; compound 1, bis(pinacolato)diboron, potassium acetate and DPPF palladium dichloride were added to a container in sequence, nitrogen was introduced, and then N,N-dimethylformamide was added, stirred for reaction, extracted, washed, dried and purified to obtain compound 2; Q2: 2-bromophenazine, compound 2, potassium carbonate and tetrakis(triphenylphosphine)palladium are added to a container in sequence, nitrogen is introduced, tetrahydrofuran, deionized water and toluene are added, the reaction is stirred in an oil bath, dried, and purified to obtain compound 3; compound 3 is added to a container containing ethanol, nitrogen is introduced, and then distilled water dissolved in sodium dithionite is added to the container, heated for reaction, and after the reaction is completed, cooled, washed, filtered, and dried to obtain compound 4; Q3: Add compound 4, 2-bromoanthraquinone, 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl, sodium tert-butoxide and tri(dibenzylideneacetone)palladium into a container, introduce nitrogen and then add 1,4-dioxane, seal the container, heat and magnetically stir to react, and after the reaction is completed, cool, filter, wash and dry to obtain the negative electrode material additive.

3. The high energy density rechargeable lithium ion battery according to claim 2, characterized in that: In the Q1, the dosage ratio of 3,5-dibromoaniline, 1-bromohexane, tetrabutylammonium bromide, potassium iodide, sodium hydroxide and acetonitrile is (6.218-6.668) g: (1.024-1.232) g: (0.782-0.866) g: (0.342-0.506) g: (8.564-8.844) g: (18-24) mL, and the stirring reaction temperature is 60-80° C. The reaction time is 6-8h; the dosage ratio of compound 1, bis(pinacolato)diboron, potassium acetate, DPPF palladium dichloride and N,N-dimethylformamide is (1.046-1.15)g: (1.11-1.55)g: (1.212-1.366)g: (0.15-0.23)g: (20-30)mL, the stirring reaction temperature is 90-110°C, and the reaction time is 6-8h.

4. The high energy density rechargeable lithium ion battery according to claim 2, characterized in that: In Q2, the dosage ratio of 2-bromophenazine, compound 2, potassium carbonate, tetrakis(triphenylphosphine)palladium, tetrahydrofuran, deionized water and toluene is (0.04-0.06) g: (0.03-0.07) g: (0.06-0.102) g: (0.008-0.014) g: (8-11) mL: (4-8) mL: (8-10) mL, the oil bath stirring temperature is 90-105°C, and the reaction time is 20-24 h; the dosage ratio of compound 3, ethanol, sodium dithionite and distilled water is (3.1-4.1) g: (45-55) mL: (31.2-37.6) g: (100-120) mL, the heating reaction temperature is 80-90°C, and the reaction time is 1-2 h.

5. The high energy density rechargeable lithium ion battery according to claim 2, characterized in that: In Q3, the dosage ratio of compound 4, 2-bromoanthraquinone, 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl, sodium tert-butoxide, tri(dibenzylideneacetone)palladium and 1,4-dioxane is (0.166-0.208) g: (0.552-0.654) g: (0.111-0.117) g: (0.188-0.234) g: (0.05-0.07) g: (18-22) mL, the heating magnetic stirring reaction temperature is 100-120°C, and the reaction time is 60-80 h.

6. The high energy density rechargeable lithium ion battery according to claim 1, characterized in that: The preparation method of the electrolyte additive comprises the following steps: S1: Add phosphonyl chloride trimer, N-hydroxyethylaniline, triethylamine and chlorobenzene into a container equipped with a thermometer, a mechanical stirrer and a reflux condenser, and heat and stir in an oil bath to react; S2: After the reaction is completed, the temperature is lowered, ammonia is introduced, filtering, washing, drying, polycondensation, cooling, dissolving, filtering, washing, and drying to obtain an electrolyte additive.

7. The high energy density rechargeable lithium ion battery according to claim 6, characterized in that: In the S1, the amount ratio of phosphonyl chloride trimer, N-hydroxyethylaniline, triethylamine and chlorobenzene is (15-19.8) g: (6.02-6.24) g: (6.48-6.64) g: (58-64) g, the oil bath heating temperature is 90-95°C, and the reaction time is 8-12h; in the S2, the temperature is lowered to -5°C to 5°C, ammonia is introduced for 20-24h, the condensation temperature is 160-190°C, the time is 10-30min, the reaction is added to deionized water for dissolution, washed with deionized water, and the drying temperature is 90-110°C for 12-18h.

8. The high energy density rechargeable lithium ion battery according to claims 1-7, characterized in that: The method for preparing the lithium ion battery comprises the following steps: Step 1: Mix lithium cobalt oxide, carbon black and polyvinylidene fluoride, then add N-methylpyrrolidone and stir to obtain positive electrode slurry, evenly coat the positive electrode slurry on aluminum foil, dry, press and cut to obtain positive electrode material; Step 2: Mix graphite and negative electrode material additives, then mix with carbon black and carboxymethyl cellulose, add deionized water and stir to obtain negative electrode slurry, evenly coat the negative electrode slurry on copper foil, dry, press and cut to obtain negative electrode material; Step 3: Mix dimethyl carbonate and lithium hexafluorophosphate, then add an electrolyte additive, stir evenly, and filter to obtain an electrolyte; Step 4: Stack the positive electrode material, porous polyethylene film and negative electrode material to obtain a battery cell, then load the battery cell into a metal shell, and then inject the electrolyte into the battery, seal it, and obtain a high energy density rechargeable lithium-ion battery.

9. The high energy density rechargeable lithium ion battery according to claim 8, characterized in that: In the step 1, the mass ratio of lithium cobalt oxide, carbon black and polyvinylidene fluoride is (88-92): (4-6): (3-7); In the step 2, the mass ratio of graphite, negative electrode material additive, carbon black and carboxymethyl cellulose is (86-89): (2.58-2.67): (2-8): (3-7); in the step 3, the mass ratio of dimethyl carbonate, lithium hexafluorophosphate and electrolyte additive is (30-53): (8-13): (0.24-0.39).

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