High-energy-density long-cycle-life lithium-ion battery and preparation method therefor

Abstract

The present invention relates to the field of lithium-ion batteries. Disclosed are a high-energy-density long-cycle-life lithium-ion battery and a preparation method therefor. The specific implementation solution involves: the high-energy-density long-cycle-life lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and an aluminum laminate film casing, wherein the positive electrode sheet consists of a positive-electrode current collector and a positive-electrode slurry applied to a surface of the positive-electrode current collector, and the positive-electrode slurry consists of a positive-electrode active substance, a positive-electrode conductive agent and a positive-electrode binder; the negative electrode sheet consists of a negative-electrode current collector and a negative-electrode slurry applied to a surface of the negative-electrode current collector, and the negative-electrode slurry consists of a negative-electrode active substance, a negative-electrode conductive agent and a negative-electrode binder; the separator is an adhesive ceramic-coated separator; and the electrolyte consists of a solute and a solvent. The present invention comprehensively improves the energy density and cycle performance of a battery cell, the energy density can reach 360 Wh / kg or above, and the electrical performance is good.

Description

High specific energy long cycle lithium ion battery and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a high specific energy long cycle lithium ion battery and a preparation method thereof. BACKGROUND

[0002] With the improvement of environmental awareness and the innovation of automobile technology, new energy vehicles as a new green transportation tool are gradually occupying the market of fuel vehicles. Short driving range and long charging time are the urgent problems to be solved for electric vehicles. Therefore, high energy density and fast charging technology are two key development directions of power batteries. In recent years, various countries have published research plans for high energy density batteries, aiming to promote the development of the electric vehicle industry more quickly and efficiently.

[0003] Patent CN106784843A uses carbon black, carbon nanotubes and graphene composite conductive agent to construct a three-dimensional conductive network, and uses high-nickel ternary or high-voltage lithium cobaltate positive electrode to prepare a lithium battery with an energy density greater than 300Wh / kg, good structural stability and high safety. Patent CN109659522A uses a high-nickel positive electrode combined with a silicon-based negative electrode material, adds carbon nanotubes with long-range conductive structure to maintain the conductive network in the later cycle, and adds a polyacrylic polymer binder to inhibit the rebound of the electrode sheet, achieving long cycle stability of high energy density batteries. Patent CN111384388B uses a pure silicon negative electrode, effectively ensures the high capacity of the negative electrode, greatly reduces the negative electrode surface density, thereby improving the energy density, and controls the depth of lithium extraction from the silicon negative electrode by controlling the voltage window of the cycle, thereby controlling the expansion and contraction degree of the electrode sheet, and preparing a lithium ion battery with high energy density, rate performance and safety performance. However, in the existing technical solutions, the development of high energy density battery is often focused on one aspect, and the energy density and cycle performance of the battery cannot be improved in all aspects. SUMMARY

[0004] Therefore, the present application provides a high specific energy long cycle lithium ion battery and a preparation method thereof to solve the problem that the existing technology cannot improve the energy density and cycle performance of the battery in all aspects.

[0005] In a first aspect, the present application provides a high specific energy long cycle lithium ion battery, comprising:

[0006] The positive electrode sheet, the negative electrode sheet, the diaphragm, the electrolyte and the aluminum plastic film shell, the positive electrode sheet is composed of a positive electrode current collector and a positive electrode slurry coated on the surface of the positive electrode current collector, the positive electrode slurry is composed of a positive electrode active material, a positive electrode conductive agent and a positive electrode binder, the negative electrode sheet is composed of a negative electrode current collector and a negative electrode slurry coated on the surface of the negative electrode current collector, the negative electrode slurry is composed of a negative electrode active material, a negative electrode conductive agent and a negative electrode binder, the diaphragm is a ceramic-coated diaphragm with glue, the electrolyte is composed of a solute and a solution, the solute includes lithium salt, and the solution is mixed by EC, PC, EMC, DMC and DEC;

[0007] The diaphragm is arranged between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet, the diaphragm and the negative electrode sheet are stacked to form an electric core, the electric core is packaged by the aluminum plastic film, and the electrolyte is injected into the electric core.

[0008] The positive electrode active material is a nine-system NCM, NCA or rich manganese-based positive electrode, and the gram capacity of the positive electrode active material is greater than or equal to 210 mAh / g.

[0009] The negative electrode active material is a pre-lithiated silicon-oxygen material or a composite material obtained by mixing a new type of vapor-deposited silicon-carbon material and artificial graphite, and the gram capacity of the composite material after mixing is greater than or equal to 700 mAh / g.

[0010] The negative electrode current collector is a PET copper foil, wherein the thickness of the PET substrate is 3-7 mu m, and the thickness of the copper plating layer is 1-2 mu m.

[0011] The base film of the ceramic-coated diaphragm with glue is 8-10 mu m, the ceramic coating is 2-5 mu m, and the glue coating is 1-3 mu m.

[0012] The electrolyte includes a plurality of additives, the plurality of additive systems include conventional additives for promoting the formation of a solid electrolyte interface film and additives for improving wettability and functional performance, and the addition amount of the plurality of additives is 0.5-3%.

[0013] In the second aspect of the application, a preparation method of a high-specific-energy long-cycle lithium ion battery is provided, comprising:

[0014] The positive electrode main material, the multi-walled carbon tube, the conductive carbon black, the PVDF and the NMP solvent are mixed to form a uniform positive electrode slurry by using a dry or wet homogenate process, the positive electrode slurry is coated on the positive electrode current collector, and the electrode sheet after coating is dried, rolled and cut to obtain the positive electrode sheet, wherein the weight ratio of the positive electrode main material, the multi-walled carbon tube, the conductive carbon black, the PVDF and the NMP solvent is 90-97.5:0.3-0.8:0.3-1.2:0.7-1.5;

[0015] The negative electrode main material, single-walled carbon tube, conductive carbon black, CMC, PAA and SBR are dispersed in solvent water by a dry mixing or wet mixing homogenizing process to obtain a negative electrode slurry, the negative electrode slurry is coated on a negative electrode current collector, and the coated electrode sheet is dried, rolled and cut to obtain a negative electrode sheet, wherein the weight ratio of the negative electrode main material, single-walled carbon tube, conductive carbon black, CMC, PAA and SBR is 85-91:0.1-0.4:4-6:0.8-1.2:4-8:2-4.

[0016] The positive electrode sheet, the separator and the negative electrode sheet are made into an electric core by a laminating machine, and the electric core is loaded into an aluminum-plastic film shell after tab welding;

[0017] The electric core loaded into the aluminum-plastic film shell is baked, and the electrolyte is injected after the moisture is qualified.

[0018] The electric core after the injection is subjected to high-temperature aging, formation and capacity, and a high specific energy long cycle lithium ion battery is obtained.

[0019] The viscosity of the positive electrode slurry is 8000-10000 mPas, and the fineness is less than or equal to 25 mu m.

[0020] The viscosity of the negative electrode slurry is 2000-5000 mPas, and the fineness is less than or equal to 35 mu m.

[0021] The baking condition of the electric core is 85 DEG C / 12h, and the moisture of the positive electrode sheet, the negative electrode sheet and the separator is tested after baking, and the moisture is qualified when the moisture of the positive electrode sheet is less than or equal to 200 ppm, the moisture of the negative electrode sheet is less than or equal to 400 ppm, and the moisture of the separator is less than or equal to 400 ppm.

[0022] Beneficial effect: the application adopts nine-system ternary or rich-manganese positive electrode material with high capacity, and high-silicon negative electrode, wherein conductive carbon black and single-arm carbon tube are added in the negative electrode slurry system to form a composite conductive network, and a PAA type adhesive with high mechanical modulus and high adhesion is additionally added, a light-weight PET copper foil is selected as the foil material, and the separator is coated with glue on the basis of the ceramic layer to bond the positive and negative electrode sheets together, the lithium ion transmission path is shortened, the positive and negative electrode contact interface is improved, and in addition to the conventional VC and FEC film-forming additives in the electrolyte, a fluorine-containing additive with higher wettability is additionally added, so that the energy density and cycle performance of the electric core are improved in all aspects, the energy density can reach more than 360 Wh / kg, and the electrical performance is good.

[0023] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the application, nor is it used to limit the scope of the application. Other features of the application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings are used to better understand the present application and do not constitute a limitation thereof. Among them:

[0025] Figure 1 is a high-temperature cycle performance diagram of a lithium ion battery prepared according to Example 1 and Comparative Examples 1, 2 and 3 provided by the present application. DETAILED DESCRIPTION

[0026] Exemplary embodiments of the present application are described below with reference to the accompanying drawings, which include various details of the embodiments of the present application to assist in understanding them. They should be considered in their context only as exemplary. Thus, those of ordinary skill in the art will recognize various changes and modifications to the embodiments described herein, without departing from the scope and spirit of the present application. Also, descriptions of well-known functions and structures are omitted in the following description for clarity and conciseness.

[0027] In a first aspect of the present application, a high specific energy long cycle lithium ion battery is provided, comprising:

[0028] A positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and an aluminum plastic film shell, the positive electrode sheet is composed of a positive electrode current collector and a positive electrode slurry coated on the surface of the positive electrode current collector, the positive electrode slurry is composed of a positive electrode active material, a positive electrode conductive agent and a positive electrode binder, the negative electrode sheet is composed of a negative electrode current collector and a negative electrode slurry coated on the surface of the negative electrode current collector, the negative electrode slurry is composed of a negative electrode active material, a negative electrode conductive agent and a negative electrode binder, the separator is a ceramic-coated separator with adhesive, the electrolyte is composed of a solute and a solution, the solute includes lithium salt, and the solution is a mixture of EC (Ethylene Carbonate), PC (Propylene Carbonate), EMC (Ethyl Methyl Carbonate), DMC (Dimethyl Carbonate) and DEC (Diethyl Carbonate).

[0029] The solute includes lithium salt, and the lithium salt is mainly lithium hexafluorophosphate.

[0030] The separator is arranged between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet, the separator and the negative electrode sheet are stacked to form an electric core, the electric core is packaged by an aluminum plastic film, and the electrolyte is injected into the electric core.

[0031] The positive electrode active material is a nine-system NCM (NCM material with high nickel content), NCA or a rich manganese-based positive electrode, and the gram capacity of the positive electrode active material is greater than or equal to 210 mAh / g.

[0032] NCM is an oxide composed of nickel, cobalt, and manganese in certain proportions. The "nine series" refers to materials with a high nickel content, close to 90%, and relatively low cobalt (Co) and manganese (Mn) content. Specifically, the chemical formula of nine series NCM material can be written as LiNi0.9xCo0.hMn0.h-xO2, where x and h are decimals representing the proportions of cobalt and manganese, while the proportion of nickel is close to 0.9. This high-nickel formulation aims to maximize the energy density of the battery.

[0033] NCA (Nickel Cobalt Aluminum) refers to a ternary material composed of nickel (Ni), cobalt (Co), and aluminum (Al). NCA materials are known for their high nickel content, and the addition of aluminum is primarily to improve the structural stability and thermal stability of the material.

[0034] Rich lithium manganese-based cathode materials are manganese-based solid solution materials containing excess lithium, with a general chemical formula of xLi2MnO3·(1-x)LiMO2, where M can be Co, Ni, Mn, and other transition metals. This type of material has a very high theoretical specific capacity.

[0035] The reason for setting the specific capacity of the positive electrode active material to at least 210 mAh / g is that this value reflects the energy storage capacity of the material in battery applications. A higher specific capacity means that the battery can store more energy under the same weight, thereby improving the overall energy density of the battery.

[0036] The negative electrode active material is a pre-lithiated silicon-oxygen material or a composite material obtained by mixing a new type of vapor-deposited silicon-carbon material with artificial graphite. The specific capacity of the composite material after mixing is greater than or equal to 700 mAh / g.

[0037] Preferably, the pre-lithiated silicon-oxygen material refers to a negative electrode material obtained by pre-lithiation treatment of silicon-oxygen (SiOx) material. Silicon-oxygen material has a high theoretical specific capacity, much higher than traditional graphite materials. However, silicon-oxygen material forms a solid electrolyte interface (SEI) film during the first charge and discharge, consuming part of the lithium ions, resulting in a lower first coulomb efficiency. Pre-lithiation treatment is to supplement this part of lithium in the material manufacturing stage to improve the first efficiency and overall energy density.

[0038] The new type of vapor-deposited silicon-carbon material is a silicon-carbon composite material prepared by chemical vapor deposition (CVD) technology. This material combines the high specific capacity of silicon and the high conductivity and stability of carbon, overcoming the problem of cycle performance decline caused by volume expansion of pure silicon material during charging and discharging.

[0039] Artificial graphite is a high-temperature treated graphite material with good cycle stability and high coulomb efficiency. Compared with natural graphite, artificial graphite has advantages in cycle performance and safety of lithium-ion batteries.

[0040] For the negative electrode material, the higher the specific capacity, the more charge can be stored per unit mass. The 700 mAh / g mentioned here is a very high value, far exceeding the theoretical specific capacity of traditional graphite materials, indicating that this composite material has extremely high energy density potential.

[0041] By mixing pre-lithiated silicon-oxygen materials or new vapor-deposited silicon-carbon materials with artificial graphite, a negative electrode material with high energy density, good cycle performance and high initial efficiency is expected. The target specific capacity of this composite material reaches 700 mAh / g or more, which represents the latest efforts in the field of negative electrode materials to pursue high performance and high energy density.

[0042] The negative electrode current collector is a PET (polyethylene terephthalate) copper foil, wherein the thickness of the PET substrate is 3-7 microns, and the thickness of the copper plating layer is 1-2 microns.

[0043] The base film of the ceramic-coated separator with adhesive is 8-10 microns, the ceramic coating is 2-5 microns, and the adhesive coating is 1-3 microns.

[0044] The electrolyte includes a multi-component additive system, which includes conventional additives that promote the formation of solid electrolyte interface films and additives that improve wettability and functional performance, and the addition amount of the multi-component additive is 0.5-3%.

[0045] Further, in addition to the conventional VC, FEC film-forming additives, the additives also include fluorine-containing or silane-containing additives that improve wettability, such as tris-(trimethylsilyl) phosphite (TMSP), vinyl tri(2,2,3-trifluoro) ethoxy silane (VTTES), etc.

[0046] In a second aspect of the present application, a preparation method of a high-specific-energy long-cycle lithium-ion battery is provided, comprising:

[0047] The positive electrode main material, multi-walled carbon tube, conductive carbon black, PVDF (polyvinylidene fluoride) and NMP (N-methyl pyrrolidone) solvent are mixed to form a uniform positive electrode slurry by dry or wet homogenization process, the positive electrode slurry is coated on the positive electrode current collector, and the coated electrode sheet is dried, rolled and cut to obtain a positive electrode sheet, wherein the weight ratio of the positive electrode main material, multi-walled carbon tube, conductive carbon black, PVDF is 90-97.5:0.3-0.8:0.3-1.2:0.7-1.5.

[0048] Further, the operation of mixing the positive electrode main material, the multi-walled carbon tube, the conductive carbon black, the PVDF and the NMP solvent to form a uniform positive electrode slurry by using a dry or wet homogenization process specifically includes,

[0049] In the dry homogenization process, the positive electrode main material, the multi-walled carbon tube, the conductive carbon black and the PVDF are directly mixed in a dry state, and the solvent NMP is not involved in the initial stage of the mixing process. The purpose of dry mixing is to first ensure uniform distribution between solid materials, and then add the solvent to dissolve the PVDF to form the slurry. The advantage of the dry process is that it can reduce the amount of solvent used.

[0050] The wet homogenization process adds solvent NMP in the initial stage of mixing, so that the positive electrode main material, the multi-walled carbon tube, the conductive carbon black and the PVDF form a uniform positive electrode slurry with the help of the solvent NMP. The presence of the solvent NMP reduces the friction between the materials, helping to form a more delicate and uniform mixture. The wet process is generally easier to control the dispersity of the materials and the viscosity of the slurry.

[0051] The negative electrode main material, the single-walled carbon tube, the conductive carbon black, the CMC, the PAA and the SBR are dispersed in the solvent water to obtain a negative electrode slurry by using a dry or wet homogenization process, the negative electrode slurry is coated on a negative electrode current collector, and the coated electrode sheet is dried, rolled and cut to obtain a negative electrode sheet, wherein the weight ratio of the negative electrode main material, the single-walled carbon tube, the conductive carbon black, the CMC (carboxymethyl cellulose), the PAA (polyacrylic acid) and the SBR (Styrene Butadiene Rubber) is 85-91:0.1-0.4:4-6:0.8-1.2:4-8:2-4.

[0052] Further, the operation of mixing the negative electrode main material, the single-walled carbon tube, the conductive carbon black, the CMC, the PAA and the SBR to obtain a negative electrode slurry by using a dry or wet homogenization process specifically includes,

[0053] In the dry homogenization process, the negative electrode main material (such as graphite), the single-walled carbon tube (SWCNT), the conductive carbon black, the CMC (carboxymethyl cellulose), the PAA (polyacrylic acid) and the SBR (styrene butadiene rubber) are mixed to ensure uniform distribution of each component in the final slurry. After dry mixing, an appropriate amount of solvent (usually water) is slowly added to the mixture while continuing to stir until the desired slurry consistency is formed. One advantage of the dry mixing process is that it can reduce the possibility of particle agglomeration, thereby helping to obtain a more uniform slurry.

[0054] The wet mixing process is to add water in the initial stage of mixing, and the negative main material (such as graphite), single-walled carbon nanotubes (SWCNT), conductive carbon black, CMC (carboxymethyl cellulose), PAA (polyacrylic acid) and SBR (styrene-butadiene rubber) are directly added into the solvent water, and then mixed by mechanical stirring or ultrasonic dispersion, until a uniform slurry is formed. The advantage of the wet mixing process is that it can better control the viscosity and fluidity of the slurry, which is very important for the subsequent coating process.

[0055] The positive plate, the separator, and the negative plate are made into a battery cell by a laminating machine, and the tab is welded and then loaded into an aluminum-plastic film shell;

[0056] The battery cell loaded into the aluminum-plastic film shell is baked, and after the moisture is qualified, the electrolyte is injected;

[0057] The battery cell after injection is subjected to high-temperature aging, formation and capacity, and a high-energy long-cycle lithium ion battery is obtained.

[0058] The positive plate and the negative plate are the core part of energy storage of the battery, which stores and releases energy through the insertion and extraction of lithium ions. The separator is located between the positive plate and the negative plate, and its main function is to prevent the direct contact of the positive and negative electrodes to cause short circuit, while allowing the free migration of lithium ions between the positive and negative electrodes through its micropores. The electrolyte is filled between the positive plate, the negative plate and the separator, which is the medium for the migration of lithium ions, and the presence of the electrolyte ensures the smooth transmission of lithium ions during charging and discharging, and participates in the formation of the SEI (solid electrolyte interface) film during the first charging and discharging of the battery, which is crucial for the performance and life of the battery.

[0059] The positive slurry has a viscosity of 8000-10000 mPas and a fineness of less than or equal to 25 μm.

[0060] The negative slurry has a viscosity of 2000-5000 mPas and a fineness of less than or equal to 35 μm.

[0061] The battery cell baking condition is 85℃ / 12h, and after baking, the moisture of the positive plate, the negative plate and the separator is tested, and when the moisture of the positive plate is less than or equal to 200ppm, the moisture of the negative plate is less than or equal to 400ppm, and the moisture of the separator is less than or equal to 400ppm, it is considered to be qualified for moisture. Embodiment

[0062] A preparation method of a high-energy long-cycle lithium ion battery, comprising the following steps:

[0063] (1) Preparation of positive electrode sheet: using wet homogenate method, 1.5% PVDF powder by mass fraction is dispersed in NMP to form glue liquid, then 0.5% multi-walled carbon tube slurry and 1% conductive carbon black by mass fraction are added in turn, after stirring uniformly, 97% nine-system NCM ternary positive electrode main material is added, after viscosity and fineness test is qualified, it is coated on 12 μm aluminum foil, dried, rolled, and cut to obtain positive electrode sheet;

[0064] (2) Preparation of negative electrode sheet: using wet homogenate method, 0.5% CMC powder by mass fraction is dispersed in deionized water to form glue liquid, 1.8% PAA glue liquid by mass fraction, 1.5% conductive carbon black and 0.05% single-arm carbon tube slurry by mass fraction are added in turn, after dispersion, 94.45% negative electrode main material is added, after viscosity and fineness are qualified, 1.7% SBR glue liquid by mass fraction is added, after dispersion, it is coated on PET copper foil, dried, rolled, and cut to obtain negative electrode sheet;

[0065] (3) Assembly: the positive electrode sheet, adhesive separator and negative electrode sheet are made into a battery cell through a laminating machine, and then the tab is welded and put into an aluminum plastic film shell;

[0066] (4) Baking and liquid injection: the assembled battery cell is vacuum baked at 85℃ / 12h, and then moisture test is carried out, after qualified, liquid injection is carried out, the electrolyte contains 0.5% additive tris-(trimethylsilyl) phosphite (TMSP), and the injection coefficient is 2~3g / Ah;

[0067] (5) Formation and capacity test: the battery cell after liquid injection is subjected to high temperature aging, formation and capacity test according to the process, and a finished high-energy-density lithium ion battery is obtained; Embodiment

[0068] A preparation method of a high-specific-energy long-cycle lithium ion battery, comprising the following steps:

[0069] (1) Preparation of positive electrode sheet: using dry homogenate method, 1.7% PVDF powder, 0.65% conductive carbon black and 97.2% nine-system ternary positive electrode powder by mass ratio are added into a stirring tank, dry powder is mixed for 5 min, then 0.45% multi-walled carbon tube slurry by mass ratio is added for kneading, NMP is added to adjust to appropriate viscosity and fineness, after qualified, it is coated on 12 μm aluminum foil, dried, rolled, and cut to obtain positive electrode sheet;

[0070] (2) Preparation of negative electrode sheet: using dry homogenate method, 0.45% by mass CMC, 1.5% conductive carbon black and 94.5% negative electrode main material were added into the stirring tank, dry powder was mixed for 5 minutes, then 1.8% PAA glue was added for kneading, 0.05% single-arm carbon tube slurry was added after kneading, water was added for viscosity adjustment, then 1.7% SBR glue was added, after uniform dispersion, it was coated on PET copper foil, dried, rolled, and cut to obtain negative electrode sheet;

[0071] (3) Assembly: the positive electrode sheet, the separator and the negative electrode sheet were stacked by a laminating machine to form a battery cell, and the battery cell was assembled into an aluminum-plastic film shell after tab welding;

[0072] (4) Baking and liquid injection: the assembled battery cell was vacuum baked at 85°C for 12 hours, and moisture test was performed after baking, and the battery cell was injected with liquid after passing the test, the battery cell was injected with liquid according to the designed capacity, and the injection coefficient was 2-3 g / Ah;

[0073] (5) Formation and capacity test: the battery cell after liquid injection was subjected to high-temperature aging and formation capacity test according to the process to obtain a finished high-energy-density lithium ion battery; Embodiment

[0074] A preparation method of a high-specific-energy long-cycle lithium ion battery, comprising the following steps:

[0075] (1) Preparation of positive electrode sheet: using wet homogenate method, 1.5% by mass PVDF powder was dispersed in solvent NMP to form glue, then 0.6% multi-walled carbon tube slurry and 0.55% conductive carbon black were added in sequence, after uniform stirring, 97.35% rich manganese-based positive electrode powder was added, and after viscosity and fineness test, it was coated on 12μm aluminum foil, dried, rolled, and cut to obtain positive electrode sheet;

[0076] (2) Preparation of negative electrode sheet: using wet homogenate method, 0.45% by mass CMC powder was dispersed in deionized water to form glue, then 1.9% PAA glue, 1.2% conductive carbon black and 0.06% single-arm carbon tube slurry were added in sequence, after uniform dispersion, 94.89% negative electrode main material was added, after viscosity and fineness test, 1.5% SBR glue was added, after uniform dispersion, it was coated on PET copper foil, dried, rolled, and cut to obtain negative electrode sheet;

[0077] (3) Assembly: the positive electrode sheet, the separator and the negative electrode sheet were stacked by a laminating machine to form a battery cell, and the battery cell was assembled into an aluminum-plastic film shell after tab welding;

[0078] (4) baking and liquid injection: the assembled battery cell is vacuum baked under the condition of 85℃ / 12h, moisture test is carried out after baking, and qualified liquid injection is carried out, the liquid injection coefficient is 2~3g / Ah according to the designed capacity of the battery cell;

[0079] (5) formation and capacity test: the battery cell after liquid injection is subjected to high temperature aging and formation capacity test according to the process, and a finished high energy density lithium ion battery is obtained;

[0080] Comparative Example 1

[0081] The same as Example 1, except that in the preparation of the negative electrode sheet in step (2), 0.05% of single-arm carbon tube is not added;

[0082] Comparative Example 2

[0083] The same as Example 1, except that in the assembly of step (3), the separator is a conventional separator without a glue layer;

[0084] Comparative Example 3

[0085] The same as Example 1, except that in step (4), the electrolyte does not add 0.5% of additive tris(trimethylsilyl) phosphite (TMSP);

[0086] Figure 1 is a high temperature cycle performance diagram of the lithium ion battery prepared in Example 1 and Comparative Examples 1, 2 and 3, and the cycle life is 741 weeks, 391 weeks, 553 weeks and 567 weeks respectively, it can be seen that the addition of single-arm carbon tube and the optimization of the composition of the separator and the electrolyte have obvious improvement effect on the improvement of the cycle life of the battery cell.

[0087] The present application uses high-capacity high-nickel ternary positive electrode matched with high-first-effect silicon-oxygen or new-type silicon-carbon negative electrode, which greatly improves the capacity of the battery cell; the single-arm carbon tube combined with conductive carbon black forms a good conductive network in the uniform slurry system of the silicon-containing negative electrode, and the PAA type adhesive is added to increase the adhesion, effectively inhibit the volume expansion of the silicon particles, and improve the cycle performance; the use of lightweight and high-safety PET copper foil improves the energy density and safety of the battery cell while significantly reducing the cost; the use of the adhesive separator bonds the positive electrode sheet and the negative electrode sheet together, avoids the formation of "dead zone" during the process of lithium extraction and embedding, shortens the lithium ion transmission path, and improves the contact interface; in the electrolyte design, the fluorine-containing or silane-containing additives are added to reduce the surface tension and improve the wettability, further improving the electrical performance of the battery cell.

[0088] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A high specific energy long cycle lithium-ion battery, characterized in that, It comprises: The positive electrode sheet, the negative electrode sheet, the diaphragm, the electrolyte and the aluminum plastic film shell, the positive electrode sheet is composed of the positive electrode current collector and the positive electrode slurry coated on the surface of the positive electrode current collector, the positive electrode slurry is composed of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder, the negative electrode sheet is composed of the negative electrode current collector and the negative electrode slurry coated on the surface of the negative electrode current collector, the negative electrode slurry is composed of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder, the diaphragm is the ceramic-coated diaphragm, the electrolyte is composed of the solute and the solution, the solute includes lithium salt, the solution is mixed by EC, PC, EMC, DMC and DEC; The diaphragm is arranged between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet, the diaphragm and the negative electrode sheet are stacked to form the battery cell, the battery cell is packaged by the aluminum plastic film and the electrolyte is injected into the battery cell.

2. The high specific energy long cycle lithium-ion battery of claim 1, wherein: The positive electrode active material is nine-system NCM, NCA or rich manganese-based positive electrode, and the gram capacity of the positive electrode active material is greater than or equal to 210 mAh / g.

3. A high specific energy, long cycle life lithium-ion battery as claimed in claim 2, wherein: The negative electrode active material is a composite material obtained by mixing pre-lithiated silicon-oxygen material or new vapor-deposited silicon-carbon material with artificial graphite, and the gram capacity of the composite material after mixing is greater than or equal to 700 mAh / g.

4. The high specific energy long cycle lithium-ion battery of claim 1 or 3, wherein: The negative electrode current collector is PET copper foil, wherein the thickness of the PET substrate is 3-7 μm, and the thickness of the copper plating layer is 1-2 μm.

5. A high-energy-density, long-cycle lithium-ion battery and its preparation method according to claim 1, characterized in that: The base film of the ceramic-coated diaphragm is 8-10 μm, the ceramic coating is 2-5 μm, and the adhesive coating is 1-3 μm.

6. A high specific energy, long cycle life lithium-ion battery as claimed in claim 5, wherein: The electrolyte includes a plurality of additives, the plurality of additive systems include conventional additives for promoting the formation of solid electrolyte interface film and additives for improving wettability and functional performance, and the addition amount of the plurality of additives is 0.5-3%.

7. A method of manufacturing a high specific energy long cycle lithium-ion battery as claimed in claims 1 to 6, characterized in that, It comprises: The positive electrode main material, the multi-walled carbon tube, the conductive carbon black, the PVDF and the NMP solvent are mixed to form a uniform positive electrode slurry by using a dry or wet homogenization process, the positive electrode slurry is coated on the positive electrode current collector, and the coated electrode sheet is dried, rolled and cut to obtain the positive electrode sheet, wherein the weight ratio of the positive electrode main material, the multi-walled carbon tube, the conductive carbon black, the PVDF is 90-97.5:0.3-0.8:0.3-1.2:0.7-1.5; The negative electrode main material, the single-walled carbon tube, the conductive carbon black, the CMC, the PAA and the SBR are dispersed in the solvent water to obtain the negative electrode slurry by using a dry or wet mixing homogenization process, the negative electrode slurry is coated on the negative electrode current collector, and the coated electrode sheet is dried, rolled and cut to obtain the negative electrode sheet, wherein the weight ratio of the negative electrode main material, the single-walled carbon tube, the conductive carbon black, the CMC, the PAA and the SBR is 85-91:0.1-0.4:4-6:0.8-1.2:4-8:2-4; The positive electrode sheet, the diaphragm and the negative electrode sheet are made into the battery cell by using the laminating machine, and the tab welding is performed before being loaded into the aluminum plastic film shell; The battery cell loaded into the aluminum plastic film shell is baked, and the electrolyte is injected after the moisture is qualified; The battery cell after injection is high-temperature aged, formed and capacity-tested to obtain the high-specific-energy long-cycle lithium ion battery.

8. A method for preparing a high-energy-density, long-cycle lithium-ion battery according to claim 7, characterized in that: The viscosity of the positive electrode slurry is 8000-10000 mPas, and the fineness is less than or equal to 25 μm.

9. The method of claim 7 or 8, wherein the method further comprises: The negative electrode slurry has a viscosity of 2000-5000 mPas and a fineness of less than or equal to 35 μm.

10. A method for preparing a high-energy-density, long-cycle lithium-ion battery according to claim 7 or 8, characterized in that: The cell baking condition is 85℃ / 12h, and moisture tests are respectively performed on the positive electrode sheet, the negative electrode sheet and the separator after baking. When the moisture of the positive electrode sheet is less than or equal to 200ppm, the moisture of the negative electrode sheet is less than or equal to 400ppm, and the moisture of the separator is less than or equal to 400ppm, it is considered that the moisture is qualified.

11. The method of claim 1, wherein the high specific energy long cycle lithium-ion battery is prepared by the steps of: Single-arm carbon tube, adhesive separator and TMSP are simultaneously added. ​

Images