阅读说明：本技术 一种电芯的制备方法 (Preparation method of battery cell ) 是由 林少雄 陆大班 赵宇飞 毕超奇 于 2020-02-28 设计创作，主要内容包括：本发明的一种电芯的制备方法,可解决现有的制备方法导致电池的能量密度不稳定及加工过程存在风险的技术问题。包括以下步骤：使用金属箔材作为负极或正极集流体,在集流体上均匀的涂布一层负极或正极材料；将粘结剂分散或溶解于相应的溶剂中,配置成具有设定固含量的粘结剂悬浊液或溶液；在制备的极片边缘露金属箔处均匀的涂覆一层粘结剂,烘箱中烘干；最后该负极或正极极片经处理后与对应的正极或负极、隔膜、电解液组装成锂离子电芯。本发明通过粘结剂的引入,覆盖了箔材表面,有效的防止了负极边缘析锂的风险,提高了电芯的安全性能；在安全性能提升的同时,可以降低负极的过量比,降低负极的使用量,并提升电芯能量密度,同时提高了生产效率。(The preparation method of the battery cell can solve the technical problems that the energy density of a battery is unstable and risks exist in the processing process due to the existing preparation method. The method comprises the following steps: using a metal foil as a negative electrode or positive electrode current collector, and uniformly coating a layer of negative electrode or positive electrode material on the current collector; dispersing or dissolving the binder in a corresponding solvent to prepare a binder suspension or solution with a set solid content; uniformly coating a layer of adhesive on the edge of the prepared pole piece where the metal foil is exposed, and drying in an oven; and finally, the negative electrode or the positive electrode plate is processed and then assembled with a corresponding positive electrode or negative electrode, a diaphragm and electrolyte to form the lithium ion battery cell. According to the invention, the surface of the foil is covered by introducing the binder, so that the risk of lithium precipitation at the edge of the negative electrode is effectively prevented, and the safety performance of the battery cell is improved; when the safety performance is improved, the excessive ratio of the negative electrode can be reduced, the using amount of the negative electrode is reduced, the energy density of the battery cell is improved, and meanwhile, the production efficiency is improved.)

1. A preparation method of a battery cell is characterized by comprising the following steps: the method comprises the following steps:

s100, using a metal foil as a negative electrode or positive electrode current collector, and uniformly coating a layer of negative electrode or positive electrode material on the current collector;

s200, dispersing or dissolving the binder in a corresponding solvent to prepare a binder suspension or solution with a set solid content;

s300, uniformly coating a layer of the adhesive in the S200 on the exposed metal foil part of the edge of the pole piece prepared in the S100, and drying in an oven;

and S400, finally, assembling the processed negative or positive pole piece, the corresponding positive or negative pole, the diaphragm and the electrolyte into the lithium ion battery cell.

2. The method for preparing the battery cell of claim 1, wherein: the thickness of the metal foil in the S100 is 5 um-20 um.

3. The method for preparing the battery cell of claim 1, wherein: the binder in the S200 comprises polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose (CMC), Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), Polyimide (PI), polyamide imide (PAI), sodium alginate (Alg), carboxymethyl chitosan (C-chitosan), Oxidized Starch (OS), Guar gum (Guar gum, GG) and a derivative obtained by modifying the binder.

4. The method for preparing the battery cell of claim 1, wherein: the binder solvent is water, N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF) and isopropanol.

5. The method for preparing the battery cell of claim 1, wherein: the solid content of the binder in the S200 is 1.5-50%.

6. The method for preparing the battery cell of claim 1, wherein: the thickness of the binder in the S200 is 5 um-50 um after drying.

7. The method for preparing the battery cell of claim 1, wherein: in the S400, the cathode excess ratio Negative/Positive, the N/P ratio or Cell Balance, CB is 1.00-1.50.

8. The method for preparing the battery cell of claim 1, wherein: in the S400, the length and width directions of the negative electrode coating area are 0-5 mm longer than the length (Overhang) of the positive electrode.

9. The method for preparing the battery cell of claim 1, wherein: the cathode material in S100 comprises a graphite cathode, a pure silicon cathode, a pure SiO cathode, a pure SiC cathode, a silicon-graphite mixed cathode, a SiO-graphite cathode, a SiC-graphite cathode, a silicon alloy cathode, a pure tin cathode or a tin alloy cathode.

10. The method for preparing the battery cell according to claim 1, wherein the positive electrode material in S100 is lithium iron phosphate (L FP), ternary (NCM), lithium cobaltate (L CO), lithium manganate (L MO), lithium nickelate (L NO), lithium vanadate (L VO).

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a battery cell.

Background

The lithium ion battery is a battery system with the highest energy density in the current commercial secondary batteries, and the commercial lithium ion battery has good cyclicity and use safety, is widely applied to the fields of communication, traffic, electronic equipment, industrial products and the like, and quickly obtains a larger market.

An important criterion in battery capacity design is that the negative electrode must have a larger reversible capacity than the positive electrode. Although the battery may have some advantages such as large capacity when the capacity of the negative electrode is smaller, lithium may be deposited on the surface of the negative electrode during charging to generate dendrite, which causes a safety problem. In addition, the capacity attenuation of the negative electrode is generally higher than that of the positive electrode in the use process of the battery, so that the capacity of the negative electrode is generally ensured to be higher than that of the positive electrode in the design process of the battery, namely the N/P ratio is more than 1 (the so-called N/P ratio is actually another name CB (cell balance)), the existing 3C products are generally designed to be 1.04-1.08 according to the design of a cell, and the power batteries are higher and are basically 1.12-1.20. However, the redundant negative electrode portion not only wastes material but also lowers the energy density from the viewpoint of the energy density.

When high energy density is pursued, each battery and material manufacturer continuously improves gram capacity, compaction density, load capacity and the like of the anode and cathode materials; the current collector and the diaphragm are continuously lightened and thinned. However, in the process of continuously thinning and continuously improving the loading capacity of the current collector, the processing performance of the current collector correspondingly has obvious risks, including the problems of wrinkling, belt breakage and the like of the current collector after coating and rolling.

In order to prevent the safety problem caused by short circuit of the positive and negative electrodes and the corresponding positive and negative current collectors, an Overhang design is required in the aspect of cell design (Overhang refers to a part of the negative electrode plate which is beyond the positive and negative electrode plates in the length and width directions, and a part of the diaphragm which is beyond the negative electrode plate in the length and width directions). However, excessive Overhang causes waste of materials as well as lowering of energy density of the battery as a high N/P ratio.

Disclosure of Invention

The preparation method of the battery cell provided by the invention can solve the technical problems that the energy density of the battery is unstable and the risk exists in the processing process due to the existing preparation method.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a battery cell comprises the following steps:

(1) using a metal foil as a negative electrode (or positive electrode) current collector, and uniformly coating a layer of negative electrode (or positive electrode) material on the current collector;

(2) dispersing or dissolving a proper amount of binder in a corresponding solvent to prepare a binder suspension or solution with a certain solid content;

(3) uniformly coating a layer of the adhesive in the step (2) on the exposed metal foil part of the edge of the pole piece prepared in the step (1), and drying in an oven;

(4) finally, the negative pole (or positive pole) pole piece is rolled, cut and the like, and then assembled with a corresponding positive pole (or negative pole), a diaphragm, electrolyte and the like to form a lithium ion battery cell;

furthermore, the negative metal foil includes metal copper foil, nickel foil, alloy foil and the like which can be suitable for the negative electrode.

Furthermore, the anode metal foil comprises metal aluminum foil and the like which can be applied to the anode.

Further, the metal foil thickness 5um ~20 um.

Further, the cathode material comprises a graphite cathode, a pure silicon cathode, a pure SiO cathode, a pure SiC cathode, a silicon-graphite mixed cathode, a SiO-graphite cathode, a SiC-graphite cathode, a silicon alloy cathode, a pure tin cathode or a tin alloy cathode.

Furthermore, the positive electrode of the electric core system corresponds to lithium iron phosphate (L FP), ternary (NCM), lithium cobaltate (L CO), lithium manganate (L MO), lithium nickelate (L NO), lithium vanadate (L VO) and the like.

Further, the binder includes polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose (CMC), Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), Polyimide (PI), Polyamideimide (PAI), sodium alginate (Alg), carboxymethyl chitosan (C-chitosan), Oxidized Starch (OS), Guar gum (Guar gum, GG), and the like, and derivatives obtained by modifying such binders, and the like.

Further, the binder solvent is selected according to different binders, and is water, Nitrogen Methyl Pyrrolidone (NMP), N-Dimethylformamide (DMF), isopropanol, etc.

Further, it is characterized in that: according to different binder selections, the solid content of the binder is 1.5% -50%.

Further, according to actual binder solid content difference, binder thickness is the thickness after the drying, and preferred is 5um ~50um, especially preferred 10~30 um.

Furthermore, in the design of the battery core, the cathode excess ratio (Negative/Positive, N/P ratio or CellBalance, CB) is 1.00-1.50, preferably 1.02-1.08.

Furthermore, according to the capacity of the assembly process, the battery core is designed, and the length and width directions of the negative electrode coating area of the battery core are 0 mm-5 mm, preferably 0 mm-1 mm longer than the length (Overhang) of the positive electrode.

According to the technical scheme, the preparation method of the battery cell has the following beneficial effects:

the invention can avoid the phenomenon that the edge of the foil is wrinkled when in use, and improve the first pass rate in the assembling process; the introduction of the binder covers the surface of the foil, so that the risk of lithium precipitation at the edge of the negative electrode is effectively prevented, and the safety performance of the battery cell is improved; when the safety performance is improved, the excessive ratio of the negative electrode can be reduced, the using amount of the negative electrode is reduced, the energy density of the battery cell is improved, the phenomena that the battery cell cannot cover the positive electrode in the assembling process, the edge short circuit and the like are reduced, and the production efficiency is improved.

Drawings

FIG. 1 is a flow chart of a method of the present invention;

FIG. 2 is a schematic structural view of the present invention;

in the figure: 11-positive (or negative) electrode current collector, 12-positive (or negative) electrode coating material, and 13-binder coating.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention.

As shown in fig. 1, the method for manufacturing a battery cell according to this embodiment includes the following steps:

s100, using a metal foil as a negative electrode or positive electrode current collector, and uniformly coating a layer of negative electrode or positive electrode material on the current collector;

s200, dispersing or dissolving the binder in a corresponding solvent to prepare a binder suspension or solution with a set solid content;

s300, uniformly coating a layer of the adhesive in the S200 on the exposed metal foil part of the edge of the pole piece prepared in the S100, and drying in an oven;

and S400, finally, assembling the processed negative or positive pole piece, the corresponding positive or negative pole, the diaphragm and the electrolyte into the lithium ion battery cell.

Wherein the content of the first and second substances,

the thickness of the metal foil in the S100 is 5 um-20 um.

The binder in the S200 comprises polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose (CMC), Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), Polyimide (PI), polyamide imide (PAI), sodium alginate (Alg), carboxymethyl chitosan (C-chitosan), Oxidized Starch (OS), guar gum (Guargum, GG) and a derivative obtained by modifying the binder.

The binder solvent is water, N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF) and isopropanol.

The solid content of the binder in the S200 is 1.5-50%.

The thickness of the binder in the S200 is preferably 5 um-50 um, particularly preferably 10-30 um after drying.

In the S400, the cathode excess ratio Negative/Positive, the N/P ratio or Cell Balance, CB, is 1.00-1.50, preferably 1.02-1.08.

In the S400, the length and width directions of the negative electrode coating area are 0 mm-5 mm longer than the length (Overhang) of the positive electrode, and the preferable length is 0 mm-1 mm.

The cathode material in S100 comprises a graphite cathode, a pure silicon cathode, a pure SiO cathode, a pure SiC cathode, a silicon-graphite mixed cathode, a SiO-graphite cathode, a SiC-graphite cathode, a silicon alloy cathode, a pure tin cathode or a tin alloy cathode.

The positive electrode material in S100 is lithium iron phosphate (L FP), ternary (NCM), lithium cobaltate (L CO), lithium manganate (L MO), lithium nickelate (L NO) and lithium vanadate (L VO).

The following are specific examples: