阅读说明：本技术 一种三元体系启停锂离子电池及其制备方法 (Ternary system start-stop lithium ion battery and preparation method thereof ) 是由 王林 刘长来 夏诗忠 孙光忠 方坤 张宝华 刘勇 于 2021-09-01 设计创作，主要内容包括：一种三元体系启停锂离子电池及其制备方法,包括正极极片、负极极片、隔膜、电解液,正极极片的正极材料中包括三元镍钴锰酸锂材料；叠片卷芯采用正、负极极片错位叠片方式,其中正极极片与负极极片上间距为正极极片超出负极极片2mm～3mm,正极极片与负极极片下间距为负极极片超出正极极片3mm～4mm,正极极片与负极极片左/右间距为负极极片超出正极极片2mm～3mm；正极材料双面涂布面密度为100～130g/m～(2)；负极材料双面涂布面密度为63～82g/m～(2)；正极极片极耳侧涂覆由无机粉末α-三氧化二铝和粘结剂聚偏氟乙烯组成的绝缘涂层；电解液中添加剂由双氟草酸磷酸锂、1,3-丙烷磺酸内酯组成。本发明用于48V启停锂离子电池,兼顾高低温性能,提高了电芯循环性能和大电流充放性能,增强电芯安全性能。(A ternary system start-stop lithium ion battery and a preparation method thereof comprise a positive pole piece, a negative pole piece, a diaphragm and electrolyte, wherein the positive pole material of the positive pole piece comprises a ternary nickel cobalt lithium manganate material; the laminated roll core adopts a positive pole piece and a negative pole piece staggered lamination mode, wherein the distance between the positive pole piece and the negative pole piece is that the positive pole piece exceeds the negative pole piece by 2-3 mm, the distance between the positive pole piece and the negative pole piece is that the negative pole piece exceeds the positive pole piece by 3-4 mm, and the left/right distance between the positive pole piece and the negative pole piece is that the negative pole piece exceeds the positive pole piece by 2-3 mm; the density of the double-sided coating surface of the positive electrode material is 100-130 g/m 2 (ii) a The density of the two-sided coating surface of the negative electrode material is 63-82 g/m 2 (ii) a Coating an insulating coating consisting of inorganic powder alpha-aluminum oxide and adhesive polyvinylidene fluoride on the side of the positive pole piece ear; the additive in the electrolyte consists of lithium difluorooxalate phosphate and 1, 3-propane sultone. The invention is used for 48V start-stop lithium ion batteries, has high and low temperature performance, improves the battery core circulation performance and the large current charge-discharge performance, and enhances the battery core safety performance.)

1. The utility model provides a ternary system opens stops lithium ion battery, includes positive pole piece, negative pole piece, diaphragm, electrolyte and aluminum hull, positive pole piece includes the anodal mass flow body and the anodal material of coating on the anodal mass flow body, negative pole piece includes the negative current collection body and the negative material of coating on the negative current collection body, positive pole piece, diaphragm and negative pole piece adopt zigzag lamination to ally oneself with into roll core, its characterized in that:

the positive electrode material comprises a ternary nickel cobalt lithium manganate material;

the winding core adopts a mode of staggered lamination of a positive pole piece and a negative pole piece, wherein the distance D1 between the positive pole piece and the negative pole piece is 2-3 mm when the positive pole piece exceeds the negative pole piece, the distance D2 between the positive pole piece and the negative pole piece is 3-4 mm when the negative pole piece exceeds the positive pole piece, and the left/right distance D3 between the positive pole piece and the negative pole piece is 2-3 mm when the negative pole piece exceeds the positive pole piece;

the density of the double-sided coating surface of the positive electrode material is 100-130 g/m²(ii) a The density of the two-sided coating surface of the negative electrode material is 63-82 g/m²；

The tab side of the positive pole piece is coated with an insulating coating; the insulating coating is composed of inorganic powder and a binder, and the mass ratio of the inorganic powder to the binder is 7: 1-9: 1; the inorganic powder is alpha-aluminum oxide, and the binder is polyvinylidene fluoride; the width Wi of the insulating coating coated on the positive pole piece is 5-7 mm;

the electrolyte consists of a solvent, lithium salt and an additive; the additive consists of lithium difluorooxalate phosphate and 1, 3-propane sultone, and the mass ratio of the lithium difluorooxalate phosphate to the 1, 3-propane sultone is as follows: 1.5-1.5: 1.

2. the ternary system start-stop lithium ion battery according to claim 1, characterized in that: the weight percentage of each component of the anode material is as follows: 92-96 wt% of positive electrode active substance, 2.5-4.8 wt% of positive electrode conductive agent and 1.5-3.2 wt% of positive electrode binder; the negative electrode material comprises the following components in percentage by weight: 92-95 wt% of negative electrode active material, 2.5-4.5 wt% of negative electrode conductive agent, and 2.5-3.5 wt% of negative electrode binder and negative electrode dispersant.

3. The ternary system start-stop lithium ion battery according to claim 2, characterized in that: the positive active material is one or more of NCM111, NCM523, NCM622 and NCM 811.

4. The ternary system start-stop lithium ion battery according to claim 2, characterized in that: the positive electrode conductive agent is one or two of carbon nano tube or graphene and conductive carbon black according to the following mass ratio of 1: 2-2: 1 are mixed to obtain the product.

5. The ternary system start-stop lithium ion battery according to claim 1, characterized in that: the positive current collector is an aluminum foil or a polished foil with coating layers on the front surface and the back surface; the coating layer is one of conductive carbon black, carbon nano tubes and graphene; the total thickness of the coating layer is 1 um-2 um.

6. The ternary system start-stop lithium ion battery according to claim 2, characterized in that: the negative active material is one or a mixture of artificial graphite, natural graphite and soft carbon.

7. The ternary system start-stop lithium ion battery according to claim 2, characterized in that: the negative electrode conductive agent is a mixture of conductive carbon black and nano-grown carbon fiber, and the mass ratio of the conductive carbon black to the nano-grown carbon fiber is 1: 2-2: 1.

8. the ternary system start-stop lithium ion battery according to claim 1, characterized in that: the diaphragm is a coating diaphragm, and the film porosity of the coating diaphragm is not lower than 44%.

9. The ternary system start-stop lithium ion battery according to claim 1, characterized in that: the aluminum shell is a square aluminum shell; the square aluminum shell is internally provided with a laminated cell, the two sides of the upper part of the laminated cell are respectively provided with a pole lug, the pole lugs on the two sides are directly connected with the cover plate, and the pole posts penetrate through the cover plate and extend to the pole lugs.

10. The preparation method of the ternary system start-stop lithium ion battery of any one of claims 1 to 9 is characterized in that: the method comprises the following steps:

step one, preparing a positive pole piece: the weight percentages are as follows: 92-96 wt% of positive electrode active substance, 2.5-4.8 wt% of positive electrode conductive agent and 1.5-3.2 wt% of positive electrode binder, and fully mixing the components of the positive electrode material to prepare positive electrode slurry; the weight percentages are as follows: 87.5-90 wt% of alpha-aluminum oxide and 10-12.5 wt% of polyvinylidene fluoride, and fully mixing the components of the insulating coating to prepare insulating coating slurry; coating the positive electrode slurry and the insulating coating slurry on the surface of a positive electrode current collector, and then drying and rolling to form a positive electrode piece; the density of the two-sided coating surface of the positive pole piece is 100-130 g/m²；

Step two, preparing a negative pole piece: the weight percentages are as follows: 92-95 wt% of a negative electrode active material, 2.5-4.5 wt% of a negative electrode conductive agent, and 2.5-3.5 wt% of a negative electrode binder and a negative electrode dispersant, wherein the negative electrode material components are fully mixed to prepare a negative electrode slurry, the negative electrode slurry is uniformly coated on the surface of a negative electrode current collector, and then drying and rolling are carried out to form a negative electrode plate; the density of the two-sided coating surface of the negative pole piece is 63-82 g/m²；

Step three, preparing a laminated roll core: respectively die-cutting the positive pole piece prepared in the step one and the negative pole piece prepared in the step two into small pieces, and sequentially overlapping the small positive pole piece, the diaphragm and the small negative pole piece in a Z shape to form a naked electric core; the distance D1 between the positive pole piece and the negative pole piece is 2-3 mm, the distance D2 between the positive pole piece and the negative pole piece is 3-4 mm, and the distance D3 between the positive pole piece and the negative pole piece is 2-3 mm; the porosity of the diaphragm is 44% -50%;

step four, assembling the battery: and (4) placing the bare cell prepared in the step three into a square aluminum shell, and performing welding, liquid injection, formation and capacity grading processes to obtain the lithium ion battery.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a ternary system start-stop lithium ion battery.

Background

At present, with the requirements of policies on energy reduction and the promotion of environmental awareness of people, the processes of fuel oil removal and lead removal are promoted, and the lithium ion battery is widely applied to new energy automobiles. Because the automatic start-stop technology can reduce unnecessary idling of the engine during midway parking and supply power to electrical appliances in the vehicle, the lithium ion start-stop battery has better emission performance and fuel economy, and becomes a favored object of various large host factories. At present, most lithium ion start-stop batteries adopt a lithium iron phosphate system, but with the gradual intelligent development of automobiles, the requirements on the output power, the temperature compatibility, the cycle performance and the safety performance of the start-stop batteries are continuously improved due to the increase of vehicle-mounted electric appliances, and the existing lithium iron phosphate system start-stop batteries can not meet the increasingly improved performance requirements gradually.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a ternary system start-stop lithium ion battery with good high-low temperature performance and strong safety performance.

The invention also aims to provide a preparation method of the ternary system start-stop lithium ion battery.

The technical scheme of the invention is as follows: the utility model provides a ternary system opens stops lithium ion battery, includes positive pole piece, negative pole piece, diaphragm, electrolyte and aluminum hull, positive pole piece includes the anodal mass flow body and the anodal material of coating on the anodal mass flow body, negative pole piece includes the negative pole mass flow body and the negative pole material of coating on the negative pole mass flow body, positive pole piece, diaphragm and negative pole piece adopt zigzag lamination to ally oneself with into roll core, including ternary nickel cobalt lithium manganate material among the anodal material.

The lamination core adopts the mode of positive pole piece and negative pole piece dislocation lamination, and wherein interval D1 is exceeded negative pole piece 2mm ~3mm for positive pole piece on positive pole piece and the negative pole piece, and interval D2 is exceeded positive pole piece 3mm ~4mm for the negative pole piece under positive pole piece and the negative pole piece, and positive pole piece and negative pole piece left/right interval D3 are exceeded positive pole piece 2mm ~3mm for the negative pole piece.

The density of the double-sided coating surface of the positive electrode material is 100-130 g/m²(ii) a The density of the two-sided coating surface of the negative electrode material is 63-82 g/m²。

The tab side of the positive pole piece is coated with an insulating coating; the insulating coating is composed of inorganic powder and a binder, and the mass ratio of the inorganic powder to the binder is 7: 1-9: 1; the inorganic powder is alpha-aluminum oxide, and the binder is polyvinylidene fluoride; the width Wi of the insulating coating coated on the positive pole piece is 5-7 mm.

The electrolyte consists of a solvent, lithium salt and an additive; the additive consists of lithium difluorooxalate phosphate and 1, 3-propane sultone, and the mass ratio of the lithium difluorooxalate phosphate to the 1, 3-propane sultone is as follows: 1.5-1.5: 1.

the weight percentage of each component of the anode material is as follows: 92-96 wt% of positive electrode active substance, 2.5-4.8 wt% of positive electrode conductive agent and 1.5-3.2 wt% of positive electrode binder; the negative electrode material comprises the following components in percentage by weight: 92-95 wt% of negative electrode active material, 2.5-4.5 wt% of negative electrode conductive agent, and 2.5-3.5 wt% of negative electrode binder and negative electrode dispersant.

The positive active material is one or more of NCM111, NCM523, NCM622 and NCM 811.

The positive electrode conductive agent is one or two of carbon nano tube or graphene and conductive carbon black according to the following mass ratio of 1: 2-2: 1 are mixed to obtain the product.

The positive current collector is an aluminum foil or a polished foil with coating layers on the front surface and the back surface; the coating layer is one of conductive carbon black, carbon nano tubes and graphene; the total thickness of the coating layer is 1 um-2 um.

The negative active material is one or a mixture of artificial graphite, natural graphite and soft carbon.

The negative electrode conductive agent is a mixture of conductive carbon black and nano-grown carbon fiber, and the mass ratio of the conductive carbon black to the nano-grown carbon fiber is 1: 2-2: 1.

the diaphragm is a coating diaphragm, and the film porosity of the coating diaphragm is not lower than 44%.

The aluminum shell is a square aluminum shell; the square aluminum shell is internally provided with a laminated cell, the two sides of the upper part of the laminated cell are respectively provided with a pole lug, the pole lugs on the two sides are directly connected with the cover plate, and the pole posts penetrate through the cover plate and extend to the pole lugs.

The preparation method of the ternary system start-stop lithium ion battery comprises the following steps:

step one, preparing a positive pole piece: the weight percentages are as follows: 92-96 wt% of positive electrode active material, 2.5-4.8 wt% of positive electrode conductive agent and 1.5-3.2 wt% of positive electrode binder, and all the components of the positive electrode material are fully mixed to prepare positive electrode slurry.

The weight percentages are as follows: 87.5-90 wt% of alpha-aluminum oxide and 10-12.5 wt% of polyvinylidene fluoride, and all the components of the insulating coating are fully mixed to prepare insulating coating slurry.

Coating the positive electrode slurry and the insulating coating slurry on corresponding positions of the surface of the positive electrode current collector, and then drying and rolling to form a positive electrode piece; the density of the two-sided coating surface of the positive pole piece is 100-130 g/m²。

Step two, preparing a negative pole piece: the weight percentages are as follows: 92-95 wt% of a negative electrode active material, 2.5-4.5 wt% of a negative electrode conductive agent, and 2.5-3.5 wt% of a negative electrode binder and a negative electrode dispersant, wherein the negative electrode material components are fully mixed to prepare a negative electrode slurry, the negative electrode slurry is uniformly coated on the surface of a negative electrode current collector, and then drying and rolling are carried out to form a negative electrode plate; the density of the two-sided coating surface of the negative pole piece is 63-82 g/m²。

Step three, preparing a laminated roll core: respectively die-cutting the positive pole piece prepared in the step one and the negative pole piece prepared in the step two into small pieces, and sequentially overlapping the small positive pole piece, the diaphragm and the small negative pole piece in a Z shape to form a naked electric core; the distance D1 between the positive pole piece and the negative pole piece is 2-3 mm, the distance D2 between the positive pole piece and the negative pole piece is 3-4 mm, and the distance D3 between the positive pole piece and the negative pole piece is 2-3 mm; the porosity of the diaphragm is 44% -50%.

Step four, assembling the battery: and (4) placing the bare cell prepared in the step three into a square aluminum shell, and performing welding, liquid injection, formation and capacity grading processes to obtain the lithium ion battery.

Compared with the prior art, the invention has the following beneficial effects: the invention adopts the mode of coating the insulating coating on the positive pole piece and combining the staggered lamination, increases the safety performance of the battery cell, further reduces the internal resistance of the battery cell by adopting low coating surface density, and improves the large-current charge-discharge performance of the battery cell. The invention adopts the electrolyte of the additives of lithium difluorooxalate phosphate and 1, 3-propane sultone, takes high and low temperature performance into consideration, further improves the cycle performance of the battery cell, and the throughput of the invention is 2 to 3 times of that of the prior art under the same test condition. The invention effectively improves the usable temperature range of the battery cell, and the usable temperature range of the battery cell is-40-85 ℃. The invention is mainly used for 48V start-stop lithium ion batteries.

Drawings

Fig. 1 is a schematic view of a lamination of a laminated core of the present invention.

FIG. 2 is a graph of three-pulse discharge at-30 ℃ of 50% SOC 10C 30S for examples of the invention and comparative examples.

FIG. 3 is a graph of 60 ℃ 3C-rate cyclic charge-discharge curves of examples and comparative examples of the present invention.

FIG. 4 is a-40 ℃ low temperature discharge curve of examples of the present invention and comparative examples.

In fig. 1, 1 is a positive electrode plate, 2 is a negative electrode plate, 3 is a separator.

Detailed Description

The present invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the embodiments of the invention are not limited thereto.

The ternary system start-stop lithium ion battery comprises a positive pole piece, a negative pole piece, a diaphragm, electrolyte and an aluminum shell, wherein the positive pole piece comprises a positive current collector and a positive material coated on the positive current collector, the negative pole piece comprises a negative current collector and a negative material coated on the negative current collector, and the positive material comprises the following components in percentage by weight: 92-96 wt% of positive electrode active material, 2.5-4.8 wt% of positive electrode conductive agent and 1.5-3.2 wt% of positive electrode binder. The negative electrode material comprises the following components in percentage by weight: 92-95 wt% of negative electrode active material, 2.5-4.5 wt% of negative electrode conductive agent, and 2.5-3.5 wt% of negative electrode binder and negative electrode dispersant. The positive pole piece, the diaphragm and the negative pole piece are connected into a roll core by adopting a Z-shaped lamination. The positive pole piece and the negative pole piece are mutually staggered and stacked, and a layer of diaphragm is clamped between each layer of positive pole piece and each layer of negative pole piece. The cross section of the diaphragm is folded in a Z shape. The positive electrode material comprises a ternary nickel cobalt lithium manganate material. The density of the double-sided coating surface of the positive electrode material is 100-130 g/m². The density of the two-sided coating surface of the negative electrode material is 63-82 g/m². The electrolyte consists of a solvent, a lithium salt and an additive. The additive consists of lithium difluorooxalate phosphate and 1, 3-propane sultone, and the mass ratio of the lithium difluorooxalate phosphate to the 1, 3-propane sultone is as follows: 1.5-1.5: 1.

the laminated roll core adopts a mode of staggered lamination of a positive pole piece and a negative pole piece, and as shown in figure 1, the laminated roll core sequentially comprises a positive pole piece 1, a diaphragm 3 and a negative pole piece 2 from top to bottom. The length Ln of the negative pole piece is 4-6 mm larger than the length Lp of the positive pole piece, and the width Wn of the negative pole piece is 0-1 mm larger than the width Wp of the positive pole piece. The width Wd of the diaphragm is 1-2 mm larger than the width Wn of the negative pole piece, and the length Ld of the diaphragm is 5-6 mm larger than the length Ln of the negative pole piece. The distance D1 between the positive pole piece and the negative pole piece is 2 mm-3 mm between the positive pole piece and the negative pole piece, the distance D2 between the positive pole piece and the negative pole piece is 3 mm-4 mm between the negative pole piece and the positive pole piece, and the distance D3 between the positive pole piece and the negative pole piece is 2 mm-3 mm between the negative pole piece and the positive pole piece. The right distance D3 between the positive pole piece and the negative pole piece is 2 mm-3 mm that the negative pole piece exceeds the positive pole piece. And coating an insulating coating on the tab side of the positive pole piece. The insulating coating is composed of inorganic powder and a binder, and the mass ratio of the inorganic powder to the binder is 7: 1-9: 1. The inorganic powder is alpha-alumina, and the binder is polyvinylidene fluoride. The width Wi of the insulating coating coated on the positive pole piece is 5-7 mm. According to the invention, the mode that the insulating coating is coated on the positive pole piece and the staggered lamination is combined is adopted, so that the potential safety hazard of short circuit can be avoided even if the lithium precipitation problem of the negative pole ear side due to climbing is caused and the diaphragm is pierced. Even if the positive electrode burrs pierce the diaphragm and are not in contact with the negative electrode, short circuit cannot be caused, the negative electrode burrs pierce the diaphragm and are in contact with the positive electrode insulating coating, short circuit cannot be caused due to the insulation of the coating, and the safety performance of the battery core is effectively improved.

The preparation method of the ternary system start-stop lithium ion battery comprises the following steps:

step one, preparing a positive pole piece: the weight percentages are as follows: 92-96 wt% of positive electrode active material, 2.5-4.8 wt% of positive electrode conductive agent and 1.5-3.2 wt% of positive electrode binder, and all the components of the positive electrode material are fully mixed to prepare positive electrode slurry. The weight percentages are as follows: 87.5-90 wt% of alpha-aluminum oxide and 10-12.5 wt% of polyvinylidene fluoride, and fully mixing the components of the insulating coating to prepare the insulating coating slurry. And uniformly coating the positive electrode slurry and the insulating coating slurry on corresponding positions on the surface of the positive electrode current collector, and then drying and rolling to form the positive electrode piece. The density of the two-sided coating surface of the positive pole piece is 100-130 g/m²。

Step two, preparing a negative pole piece: the weight percentages are as follows: 92-95 wt% of negative electrode active material, 2.5-4.5 wt% of negative electrode conductive agent, 2.5-3.5 wt% of negative electrode binder and negative electrode dispersant, fully mixing the components of the negative electrode material to prepare negative electrode slurry, uniformly coating the negative electrode slurry on the surface of a negative electrode current collector, and then drying and rolling to form a negative electrode pole piece. The density of the two-sided coating surface of the negative pole piece is 63-82 g/m²。

Step three, preparing a laminated roll core: and D, respectively die-cutting the positive pole piece prepared in the step one and the negative pole piece prepared in the step two into small pieces, and sequentially overlapping the small positive pole piece, the diaphragm and the small negative pole piece in a Z shape to form the bare cell. The distance D1 between the positive pole piece and the negative pole piece is 2 mm-3 mm between the positive pole piece and the negative pole piece, the distance D2 between the positive pole piece and the negative pole piece is 3 mm-4 mm between the negative pole piece and the positive pole piece, and the distance D3 between the positive pole piece and the negative pole piece is 2 mm-3 mm between the negative pole piece and the positive pole piece. The porosity of the diaphragm is 44% -50%.

Step four, assembling the battery: and (4) placing the bare cell prepared in the step three into a square aluminum shell, and obtaining the lithium ion battery through the working procedures of welding, liquid injection, formation, capacity grading and the like.

The above-described lithium ion battery manufacturing method was used to perform trial production of the batteries of examples and comparative examples.

Example 1

The anode material comprises the following raw materials in percentage by weight: 95wt% of NCM523 (positive electrode active material), 3wt% of a conductive carbon black and carbon nanotube mixture (positive electrode conductive agent, 1.6wt% of conductive carbon black, 1.4wt% of carbon nanotubes), 2wt% of polyvinylidene fluoride (positive electrode binder).

The insulating coating comprises the following raw materials in percentage by weight: 88wt% of alpha-alumina and 12wt% of polyvinylidene fluoride.

The cathode material comprises the following raw materials in percentage: 95wt% of artificial graphite and soft carbon mixture (negative electrode active material), 2wt% of conductive carbon black and nano-grown carbon fiber mixture (negative electrode conductive agent, 1wt% of conductive carbon black, 1wt% of nano-grown carbon fiber), 3wt% of styrene-butadiene rubber and sodium carboxymethyl cellulose (negative electrode binder and dispersant, 2wt% of styrene-butadiene rubber, 1wt% of sodium carboxymethyl cellulose).

The lithium salt in the electrolyte is lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide, and the mass ratio of the lithium salt to the lithium bis (fluorosulfonyl) imide is 2: 1, using ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate as solvents in the electrolyte, wherein the mass ratio of the ethylene carbonate to the methyl ethyl carbonate to the dimethyl carbonate is 1: 2: 2, additives in the electrolyte are lithium difluorooxalate phosphate and 1, 3-propane sultone, and the mass ratio of the lithium difluorooxalate phosphate to the 1, 3-propane sultone is 1: 1.5.

the density of the double-sided coating surface of the positive electrode is 110g/m²The density of the coated double-sided surface of the negative electrode is 70g/m²。

Example 2

The anode material comprises the following raw materials in percentage by weight: 92.5wt% of NCM523 (positive electrode active material), 4.5wt% of a conductive carbon black and carbon nanotube mixture (positive electrode conductive agent, 2.4wt% of conductive carbon black, 2.1wt% of carbon nanotubes), 3wt% of polyvinylidene fluoride (positive electrode binder).

The insulating coating comprises the following raw materials in percentage by weight: 89.5wt% of alpha-alumina and 10.5wt% of polyvinylidene fluoride.

The cathode material comprises the following raw materials in percentage: 92wt% of artificial graphite and soft carbon mixture (negative electrode active material), 4.5wt% of conductive carbon black and nano-grown carbon fiber mixture (negative electrode conductive agent, 2.5wt% of conductive carbon black, 2wt% of nano-grown carbon fiber), 3.5wt% of styrene-butadiene rubber and sodium carboxymethyl cellulose (negative electrode binder and dispersant, 2.5wt% of styrene-butadiene rubber, 1wt% of sodium carboxymethyl cellulose).

The lithium salt in the electrolyte is lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide, and the mass ratio of the lithium salt to the lithium bis (fluorosulfonyl) imide is 2: 1, using ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate as solvents in the electrolyte, wherein the mass ratio of the ethylene carbonate to the methyl ethyl carbonate to the dimethyl carbonate is 1: 2: 2, additives in the electrolyte are lithium difluorooxalate phosphate and 1, 3-propane sultone, and the mass ratio of the lithium difluorooxalate phosphate to the 1, 3-propane sultone is 1: 1.5.

the density of the double-sided coating surface of the positive electrode is 120g/m²The density of the coated double-sided surface of the negative electrode is 76g/m²。

Comparative example 1

The anode material comprises the following raw materials in percentage by weight: 95wt% of NCM523 (positive electrode active material), 3wt% of a conductive carbon black and carbon nanotube mixture (positive electrode conductive agent, 1.6wt% of conductive carbon black, 1.4wt% of carbon nanotubes), 2wt% of polyvinylidene fluoride (positive electrode binder).

The insulating coating comprises the following raw materials in percentage by weight: 88wt% of alpha-alumina and 12wt% of polyvinylidene fluoride.

The cathode material comprises the following raw materials in percentage: 95wt% of artificial graphite and soft carbon mixture (negative electrode active material), 2wt% of conductive carbon black and nano-grown carbon fiber mixture (negative electrode conductive agent, 1wt% of conductive carbon black, 1wt% of nano-grown carbon fiber), 3wt% of styrene-butadiene rubber and sodium carboxymethyl cellulose (negative electrode binder and dispersant, 2wt% of styrene-butadiene rubber, 1wt% of sodium carboxymethyl cellulose).

The lithium salt in the electrolyte is lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide, and the mass ratio of the lithium salt to the lithium bis (fluorosulfonyl) imide is 2: 1, using ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate as solvents in the electrolyte, wherein the mass ratio of the ethylene carbonate to the methyl ethyl carbonate to the dimethyl carbonate is 1: 2: 2, the additive in the electrolyte is lithium difluorooxalate phosphate.

The density of the two coating surfaces of the anode is 115g/m²The density of the coated double-sided surface of the negative electrode is 70g/m²。

Comparative example 2

The anode material comprises the following raw materials in percentage by weight: 95wt% of NCM523 (positive electrode active material), 3wt% of a conductive carbon black and carbon nanotube mixture (positive electrode conductive agent, 1.6wt% of conductive carbon black, 1.4wt% of carbon nanotubes), 2wt% of polyvinylidene fluoride (positive electrode binder).

The insulating coating comprises the following raw materials in percentage by weight: 89.5wt% of alpha-alumina and 10.5wt% of polyvinylidene fluoride.

The cathode material comprises the following raw materials in percentage: 95wt% of artificial graphite and soft carbon mixture (negative electrode active material), 2wt% of conductive carbon black and nano-grown carbon fiber mixture (negative electrode conductive agent, 1wt% of conductive carbon black, 1wt% of nano-grown carbon fiber), 3wt% of styrene-butadiene rubber and sodium carboxymethyl cellulose (negative electrode binder and dispersant, 2wt% of styrene-butadiene rubber, 1wt% of sodium carboxymethyl cellulose).

The lithium salt in the electrolyte is lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide, and the mass ratio of the lithium salt to the lithium bis (fluorosulfonyl) imide is 2: 1, using ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate as solvents in the electrolyte, wherein the mass ratio of the ethylene carbonate to the methyl ethyl carbonate to the dimethyl carbonate is 1: 2: and 2, the additive in the electrolyte is 1, 3-propane sultone.

The density of the two coating surfaces of the anode is 115g/m²The density of the coated double-sided surface of the negative electrode is 70g/m²。

The lithium battery performance detection cabinet is adopted to respectively carry out low-temperature cold start test, high-temperature multiplying power cycle test, low-temperature discharge test and high-temperature storage test on the lithium ion batteries in the embodiment and the comparative example.

1. -30 ℃ 50% SOC 10C 30S Cold Start test

The laminated aluminum-can batteries prepared in the examples and the comparative examples were adjusted to 50% SOC at normal temperature with 1C current, the batteries were left at-30 ℃ for 24 hours, discharged at 10C for 30 seconds at constant current, left for 10 minutes, discharged at 10C for 30 seconds, left for 30 seconds, discharged at 10C for 30 seconds, and then discharged at 10C for 30 seconds, and the test was terminated, and the voltage of the batteries during discharge was recorded, and the test results are shown in fig. 1. Comparative test results found that the batteries of example 1, example 2 and comparative example 1 had good low-temperature discharge performance at-30 ℃ at 50% SOC and 10C current for 30 seconds. The lithium bifluorodioxolate phosphate effectively improves the low-temperature performance of the battery.

2. 3C/3C cycle test at 60 DEG C

The laminated aluminum-can batteries prepared in the examples and comparative examples were adjusted to 80% SOC, left to stand in an environment of 60 ℃ for 4 hours, charged at a constant current of 3C to a 4.2V cutoff, and then discharged at a constant current of 3C to 2.8V, recorded as 1 cycle, and the above cycles were repeated, and after every 200 cycles, the capacity retention rate of each battery was tested, and the test results are shown in fig. 3. The comparative test results show that the capacity retention rate of the batteries in the examples 1 and 2 and the battery in the comparative example 2 can still reach more than 88% after 1500 times of 3C/3C cycles at 60 ℃. The battery containing the 1, 3-propane sultone has good high-temperature cycle performance.

3. Low temperature discharge test at-40 deg.C

The laminated aluminum-can batteries prepared in examples and comparative examples were adjusted to 100% SOC, left to stand in an environment of-40 ℃ for 24 hours, discharged at a constant current of 1C to 2.24V cutoff, and the low-temperature discharge capacity of the batteries was tested, and the test results are shown in fig. 4, and the comparative test results revealed that the batteries in examples 1, 2, and 1 exhibited a discharge percentage of 73% at-40 ℃.

4. High temperature storage test at 85 deg.C

The laminated aluminum-can batteries prepared in examples and comparative examples were adjusted to 80% SOC, stored at 85 ℃ for 24 hours, and tested for capacity retention and capacity recovery, the results of which are shown in table 1, and the batteries of examples 1, 2 and 2 were found to have good capacity retention and capacity recovery at 85 ℃.

TABLE 1

As can be seen from the test results of fig. 2 to 4 and table 1, the low-temperature discharge performance and the high-temperature cycle performance of the batteries of examples 1 and 2 according to the present invention were significantly higher than those of the battery of the comparative example.

The lithium ion battery adopts a structure that the positive pole piece and the negative pole which are coated by aluminum oxide (AT 9) are staggered and laminated, and the positive pole piece and the negative pole piece cannot be conducted even if a diaphragm breaks along the positive pole and the negative pole, so that the safety performance of a battery cell is improved; the lower coating surface density is adopted, so that the conductivity of the electrode is increased, the internal resistance of the battery is reduced, and the output power and the cycle performance are improved; the lithium bifluorodioxolate phosphate additive effectively improves the low-temperature discharge performance of the battery, and the 1, 3-propane sultone additive has good film forming performance and electrical conductivity and effectively improves the high-temperature performance of the battery.