WO2010148842A1

WO2010148842A1 - Lithium ion battery

Info

Publication number: WO2010148842A1
Application number: PCT/CN2010/072952
Authority: WO
Inventors: Lei Han; Tianzeng Bao
Original assignee: Byd Company Limited
Priority date: 2009-06-26
Filing date: 2010-05-19
Publication date: 2010-12-29
Also published as: EP2430695A4; US20120135286A1; JP2012531020A; KR20120046199A; US8252438B2; EP2430695A1; CN201682023U; KR101366981B1

Abstract

A lithium ion battery comprises a shell (1), an electric core (3) disposed in the shell with a space (4) formed therebetween, and a non-aqueous electrolyte housed in the shell (1), in which the space (4) is filled with a non-aqueous electrolyte resistance filler The lithium ion battery according to the present invention may have a great capacity, good safety performance and cycle performance

Description

LITHIUM ION BATTERY

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority and benefits of Chinese Patent Application Serial No. 200920133723.3, filed with the State Intellectual Property Office of the P. R. China on June 26, 2009, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

TECHNICAL FIELD

The present invention relates to a lithium ion battery.

BACKGROUND

Lithium ion batteries have been developed rapidly in the last twenty years. As a type of new energy, lithium ion batteries may have many advantages such as high voltage, high capacity, low consumption, no memory effect, no pollution, small volume, high specific energy, low internal resistance, low self-discharge rate, multiple cycle times, good safety performance, and various volume and appearance. Therefore, the lithium ion batteries are one of the most important kinds of batteries. Now lithium ion batteries are getting more and more attentions and have been widely used in various kinds of electronic products such as notebooks and mobile telephones.

As demands for lithium ion batteries are increasing, requirements for their preparation technologies are higher so as to obtain batteries with higher energy density and better electrochemical performance. The developmental trend of the battery technology is improving the capacity, cycle performance, safety performance and high temperature storage performance of the lithium ion batteries.

It is known in the art that the internal volume of the battery may comprise: the volume of the electric core and the battery structural parts, the volume of electrolyte and the preserved gas swelling volume. Currently, due to the limitation of the injection molding technology for manufacturing the structural parts and the compressibility of the volume of the electric core, a remaining space may be formed in the battery shell. Due to the presence of the remaining space, the amount of the electrolyte to be filled may be increased, and while the battery swells in use,, the distance between the electrode plates may be increased, thereby increasing the length of the ion exchange path, decreasing the battery cycle performance, and increasing the cost and the weight of the battery. Moreover, the remaining space may allow occurring of the wrinkles of the ion exchange film of the electric core, and the wrinkles may cause the generation of the lithium dendrites and further cause potential safety hazard. Furthermore, due to the presence of the remaining space, after the electrolyte is filled, the separator is immersed by the electrolyte and may swell so that the surfaces of the electrode plates and the separator may not be in close proximity, thus affecting the battery capacity.

SUMMARY

The present invention is directed to provide a lithium ion battery that may have simple structure, and good safety performance and cycle performance.

An embodiment of the present invention provides a lithium ion battery comprising a shell, an electric core disposed in the shell with a space formed therebetween, and non-aqueous electrolyte housed in the shell, in which the space is filled with a non-aqueous electrolyte resistance filler.

According to another embodiment of the present invention, the filler may comprise spheroidal particles having an average diameter of about 1 mm- 15 mm. According to yet another embodiment of the present invention, the filler may comprise hollow spheroidal particles having an average inner diameter of about 1 mm- 10 mm, and an average external diameter of about 2 mm- 15 mm.

Embodiments of the present invention may have the following advantages that: the space between the shell and the electric core may be reduced, so that the battery safety performance may be effectively improved and the cycle performance may be enhanced.

DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view showing the remaining space inside a battery: in which, 1 : a battery shell; 2: positive and negative terminals; 3: a battery electric core; 4: a remaining space inside the battery; 5: battery lugs; and 6: electrical connectors.

DETAILED DESCRIPTION OF THE EMBODIMENTS

According to an embodiment of the present invention, the lithium ion battery may comprise a shell, an electric core disposed in the shell with a space formed between the electric core and the shell, and non-aqueous electrolyte housed in the shell. The space between the shell and the electric core may be filled with a filler.

There is no particular limitation on the amount of the filler which may be adjusted according to the size of the battery.

According to an embodiment of the present invention, the filler may be one or more compounds selected from a group including polyphenylene sulfide, polyphenylether, polyethylene, polypropylene, polytetrafluoroethylene, polyperchlorethylene, high density polyethylene, and polyvinylidene chloride. There is no special restriction on the proportion of the compositions of the filler when the filler is a mixture comprising two or more compounds above.

According to another embodiment of the present invention, the filler may have a particle, strip, stick or board shape. In a particular example, the filler may comprise spheroidal particles having an average diameter of lmm- 15mm. According to another embodiment, the filler may comprise hollow spheroidal particles having an average inner diameter of about lmm- 10mm, and an average external diameter of about 2mm- 15mm. Comparing to filing the remaining space with only the electrolyte in the prior art, according to the present embodiment, hollow spheroidal particles may be filled in the battery thus decreasing the amount of the electrolyte to be filled, so that the cost of the battery may be reduced. Meanwhile, because of the presence of the filler, the deformation of the electric core during charging and discharging may be reduced, and the distance between the electrode plates may be shortened by the filler so that the charging efficiency and the battery capacity may be enhanced. Moreover, the filler according to some embodiments of the present invention may be elastic, when the battery swells during charging and discharging, the internal stress may be released via the filler. Therefore, wrinkles of the separator may be avoided and the safety performance may be enhanced.

The separator used during winding may be any kind of lithium battery separators well known in the art. The separator may be interposed between the positive electrode plate and the negative electrode plate. The separator is electrically insulating and also has good electrolyte retaining performance. According to some embodiments of the present invention, the separator may be any kind of separators used in the secondary lithium ion batteries known in the art, such as polyolefm micro-porous membrane, polyethylene felt, glass fiber felt or ultrafme glass fiber paper.

The battery shell may be any kind of those used for preparing batteries well known in the art. According to some embodiments, the battery shell may be made of aluminum or steel.

The positive electrode plate may be any kind of those well known in the art. Generally, the positive electrode plate may comprise a current collecting substrate and a positive electrode active material coated and/or filled thereon. The current collecting substrate may be any one well known in the art such as aluminum foil or copper foil. The positive electrode active material may comprise a positive electrode active substance and an adhesive, in which the positive electrode active substance may be any one known in the art of the lithium ion battery. According to some embodiments of the present invention, the positive electrode active substance may be LiCoO₂, LiFePO₄, or LiMnO₂ etc. The adhesive may be any one well known in the art such as polyvinylidene fluoride (PVDF). Generally, the amount of the adhesive may be about 0.01-8 wt % of the weight of the positive electrode active substance. According to an embodiment, the amount of the adhesive is about 1-5 wt % of the weight of the positive electrode active substance. The positive electrode active material may also comprise positive electrode aids additives. The positive electrode aids may be any one well known in the art and may be selected from conductive agents, for example, at least one of acetylene black, conductive carbon black and conductive graphite. The content of the additives may be about 0-15 wt % of the weight of the positive electrode active substance. According to an embodiment of the present invention, the additives may be about 0-10 wt % of the weight of the positive electrode active substance.

The negative electrode plate may be any kind of those well known in the art and may comprise a conductive current collecting substrate and a negative electrode active material coated and/or filled thereon. The conductive substrate may be any one well known in the art such as copper foil. The negative electrode active material may comprise a negative electrode active substance and an adhesive. The negative electrode active substance may be any one commonly used in lithium ion batteries, such as natural graphite, and artificial graphite. The adhesive may be any one well known in the art such as polyvinylidene fluoride (PVDF) and polyvinyl alcohol. The adhesive may be about 0.01-10 wt % of the weight of the negative electrode active substance. According to an embodiment, the adhesive may be about 1-9 wt % of the weight of the negative electrode active substance.

The separator may be disposed between the positive electrode plate and the negative electrode plate, and may be any one commonly used in the lithium ion batteries. According to some embodiments, the separator may be made from a material such as polypropylene felt, polyethylene felt, polyethylene micro-porous film or ultrafine glass fiber paper, that has electric insulating performance and electrolyte retaining performance.

The preparation method of the positive electrode plate may comprise steps of: coating a slurry containing a positive electrode active substance and an adhesive onto a current collecting substrate having a large width; drying the substrate coated with the slurry, rolling the dried substrate and then cutting the substrate into positive electrode plates. The solvent dissolving the positive electrode active substance and the adhesive may be any conventional solvent known in the art. According to some embodiments of the present invention, the solvent may be N-methyl-2-pyrrolidone (NMP), dimethyl formamide (DMF) and so on. The dosage of the solvent may satisfy that the slurry be able to coated onto the current collector. Generally, the amount of the solvent may be about 40-90 wt % of the weight of the positive electrode active substance. In a specific example, the amount of the solvent may be about 50-85 wt % of the weight of the positive electrode active material. The drying temperature may be about 50-160 ^°C . In a specific example, the drying temperature may be about 80-150 ^°C . The rolling step may be used to adjust the thickness of the positive electrode plate, and the thickness may be varied in a broad range depending on a variety of batteries. The width of the positive electrode plate may be adjusted by cutting according to different requests, and the width may be varied in a broad range depending on a variety of batteries.

The preparation method of the negative electrode plate may be substantially the same as that of the positive electrode plate, except that the slurry which contains a positive electrode active substance and an adhesive is replaced by the slurry which contains a negative electrode active substance and an adhesive.

The winding method of the positive electrode plate, negative electrode plate and the separator has been described above, so that detailed descriptions thereof are omitted here for briefness.

The non-aqueous electrolyte may comprise a lithium salt electrolyte and a non-aqueous solvent. The lithium salt electrolyte may be one or more electrolytes selected from a group including lithium hexafluorophosphate (LiPF₆), lithium perchlorate (LiClO₄), lithium tetrafluoroborate (LiBF₄), lithium hexafluoro arsenate (LiAsF₆), lithium halide, lithium aluminum tetrachloride and lithium fluoro-alkyl sulfonate. The organic solvent may be a mixture of chain-like acid esters or cyclic acid esters. The chain-like acid ester may be at least one esters selected from a group including dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), dipropyl carbonate (DPC) and other fluorine-containing, sulfur-containing or unsaturated bond-containing chain-like organic esters. The cyclic acid ester may be one or more esters selected from a group including ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), γ-butyrolactone (γ-BL), sultone and other fluorine-containing, sulfur-containing or unsaturated bond-containing cyclic organic esters. In the non-aqueous electrolyte solution, the concentration of the lithium salt electrolyte may be about 0.1-2 mol/L. According to a specific example, the concentration of the lithium salt electrolyte may be about 0.8-1.2 mol/L.

The winding method of the positive electrode plate, negative electrode plate and the separator disposed between the positive electrode plate and the negative electrode plate into the electric core, and the assembly method of the battery are well known in the art, so that detailed descriptions thereof are omitted here for briefness.

An embodiment of a secondary lithium ion battery comprising a laminated core will be described below.

The secondary lithium ion battery according to the present embodiment may comprise a battery shell, a battery pole and an electric core. The shell may be quadrangular or cylindrical and be generally made of a metal material. The battery pole may comprise a positive pole and a negative pole. The electric core may be formed by superposing or winding the positive electrode plate, the separator and the negative electrode plate alternatively in turn in the thickness direction of the battery. A positive leading-out tab and a negative leading-out tab may be provided at an upper end and a lower end of each of the positive and negative electrode plates, respectively. According to some embodiments, the positive and negative leading-out tabs of the positive and negative electrode plates in adjacent layers are located at the upper and lower ends of the electric core respectively, or both of the positive and negative leading-out tabs of the positive and negative electrode plates in adjacent layers are located at the upper end or the lower end of the electric core. The separator may be a polyethylene micro-porous membrane or a laminated polypropylene and polyethylene micro-porous membrane. The positive electrode plate, the separator and the negative electrode plate mentioned above are superposed or wound to form an electric core.

The positive electrode may comprise a lithium-transition metal composite oxide which is an active substance with a specific structure and can react reversibly with the lithium ion. The active material may be one or a mixture of Li_xNi^_yCoO₂ (in which 0.9≤x≤l.l, O≤y≤l.O), Li_xMn2-_yByθ2 (in which B may be a transition metal, 0.9≤x≤l.l, O≤y≤l.O), etc. Besides, the positive electrode plate may also comprise a metal current collector (generally aluminum foil), a carbon system conductive agent and an adhesive for binding the positive material onto the current collector. The carbon system conductive agent may be carbon black, carbon fiber, graphite, etc, and one or a mixture of the aforementioned conductive agents may be selected. The adhesive may be one of fluorine-containing resins and polyolefm compounds such as PVDF, PTFE, VDF-HFP-TFE copolymer, and SBR, and one or a mixture of the above agents may be selected.

The negative electrode active material may be a carbon system material that may realize repeated lithium ion intercalation and de-intercalation. According to one embodiment of the present invention, the negative electrode active material may be one or more materials selected from a group including graphite, petroleum coke, organic cracked carbon, MCMB, and MCF. Besides, the negative electrode may also comprise a metal current collector (generally, copper foil) and an adhesive for binding the negative electrode active material onto the current collector. According to another embodiment of the present invention, the adhesive may comprise one or more of fluorine-containing resins and polyolefm compounds such as PVDF, PTFE, VDF-HFP-TFE copolymer, and SBR, and one or a mixture of the above agents may be selected. The positive and negative slurries may be formed by dissolving an adhesive into a certain solvent, and then adding an active substance and a conductive agent into the solution, and finally adequately dispersing the solution. According to one embodiment of the present invention, the solvent may be one or more solvents selected from a group including NMP, DMF, DEF, DMSO, THF, water and alcohols, etc.

The electrolyte solution may be a mixed solution of an electrolyte salt and a solvent. According to some embodiments of the present invention, the electrolyte salt may be a lithium salt which may be one or more salts selected from a group including LiClO₄, LiPF₆, LiBF₄, LiAsF₆, lithium halide, lithium aluminum tetrachloride, and lithium fluoro-alkyl sulfonate, etc. The solvent may be a mixture of chain-like acid ester and cyclic acid ester. The chain-like acid ester may be at least one esters selected from a group including DMC, DEC, EMC, MPC, DPC, MA, EA, PA, dimethoxyethane and other fluorine-containing, sulfur-containing or unsaturated bond-containing chain-like organic ester. The cyclic acid ester may be one or more compounds selected from a group including ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), γ-butyrolactone (γ-BL), sultone and other fluorine-containing, sulfur-containing or unsaturated bond-containing cyclic organic ester.

According to an embodiment of the present invention, while preparing the positive electrode plate, certain amounts of a positive electrode active material, a conductive agent, an adhesive and a solvent are mixed according to a certain ratio to form a uniform slurry, and the slurry is coated onto the positive current collector uniformly, dried and calendered to obtain the positive electrode plate, and then a certain width of the coating on the edge of the positive electrode plate was removed so that a certain width of the positive leading-out tab may be exposed, and finally the formed positive electrode plate is sandwiched into a polypropylene micro-porous separator or a laminated polyethylene and polypropylene micro-porous separator and then the separator is sealed to form a positive electrode plate bag.

According to an embodiment of the present invention, while preparing the negative electrode plate, certain amounts of a negative electrode active material, an adhesive and a solvent are mixed according to a certain ratio to form a uniform slurry, and the slurry is coated onto the negative current collector uniformly, dried and calendered to obtain the negative electrode plate, and then a certain width of the coating on the edge of the negative electrode plate was removed so that a certain width of the negative leading-out tab may be exposed, and finally the formed negative electrode plate is sandwiched into a polypropylene micro-porous separator or a laminated polyethylene and polypropylene micro-porous separator and then the separator is sealed to form a negative electrode plate bag.

The above sealed positive and negative bags are staggered and laminated to form an electric core of a lithium ion battery. The electric core may be clipped tightly by an upper clamping plate and a lower clamping plate. The leading-out tabs and the electrode poles are then connected by a flexible connector to form a current collecting structure. According to some embodiments, the connection between the flexible connector and the electrode plates may be riveting, while the connection between the flexible connector and the electrode poles may be bolting. The electric core may be placed into the battery shell 8, and then an electrolyte formed by dissolving LiPF₆ with a concentration of lmol/dm³ in the mixed solvent of EC/DMC = 1 :1 may be injected into the battery shell which may be then sealed, thus obtaining the lithium ion battery according to the present embodiment.

In the lithium ion battery according to an embodiment of the present invention, the length, width and height of the shell may have a ratio of 50-800:30-500:5-500.

For the electric core according to an embodiment of the present invention, the length, width and height may have a ratio of 45-795:25-495:5-100.

Example 1

The lithium ion battery according to the present example was prepared, in which the shell was made of aluminum and was substantially rectangular parallelepiped, with a length of 28 mm, a width of 100 mm, and a height of 356 mm.

(1) Preparation of a Positive Electrode Plate 1

100 parts by weight of LiCoO₂ positive electrode active material, 5 parts by weight of acetylene black conductive agent, and 5 parts by weight of PVDF adhesive were added into 50 parts by weight of NMP and the mixture was mixed uniformly. The mixture was then uniformly coated onto an aluminum foil having a thickness of about 0.016 mm. The leading-out tab area was formed by removing the positive material coatings from a portion of the aluminum foil, and the electrode plate was then placed in a vacuum oven at about 120^°C for drying. The dried current collector was cut into a positive electrode plate with a size of about 2010^χ296><0.138 mm. The weight of the coating on the positive electrode plate may be about 149.62 g.

(2) Preparation of a Negative Electrode plate 2

100 parts by weight of artificial graphite negative electrode active material and 9 parts by weight of PVDF adhesive were added into 50 parts by weight of NMP and the mixture was mixed uniformly to form a slurry. The slurry was then uniformly coated onto a copper foil with a thickness of 0.012 mm. The leading-out tab area was formed by removing the negative material coatings form a portion of the copper foil, and the electrode plate was further placed in a vacuum oven at about 120^°C for drying. The dried current collector was cut into a negative electrode plate with a size of about 2290^χ305x0.121 mm. The weight of the coating on the negative electrode plate was about 85.44 g.

(3) Preparation of a Flat Type Electric Core

The positive electrode plate 1, the negative electrode plate 2 prepared above and a separator 3 were wound into a flat type electric core having a size of 300^χ300x50 mm.

(4) Assembly of a Battery

LiPF₆ was solved in a EC and DMC mixed solvent (EC/DMC was about 1 : 1 by volume) to form a non-aqueous electrolyte solution in which the concentration of the LiPF₆ was about lmol/L. The dosage of the non-aqueous electrolyte solution was about 360 g for each electric core. The flat type electric core obtained in step (3) was accommodated in a battery shell 1 having a size of 28^χ 100^χ356 mm, and 40 grams in total of PPS particle and polyphenylene oxide particle with an average diameter of 2 mm were filled in the space between the battery shell and the electric core. The non-aqueous electrolyte above was injected into the battery and the battery was then sealed by a cover board so as to form a lithium ion battery Cl. 2000 batteries were prepared according to the present example.

Comparative Example 1

The preparation method in Comparative Example 1 was the same as that in Example 1 except that no filler was filled into the space between the shell and the electric core. A sample TC 1 was obtained. 2000 batteries were prepared accordingly.

Example 2

The preparation method in Example 2 was the same as that in Example 1 except that the filler was about 30 grams of a hollow spherical polytetrafluoroethylene particle having an outer diameter of 2 mm and an inner diameter of 1 mm. The obtained sample was denoted as C2, and 2000 batteries were prepared accordingly.

Example 3

The preparation method in Example 3 was the same as that in Example 1 except that the filler was about 30 grams of a hollow spherical HDPE particle having an outer diameter of 12 mm and an inner diameter of 1 mm. The obtained sample was denoted as C3, and 2000 batteries were prepared accordingly.

Example 4

The preparation method in Example 4 was the same as that in Example 1 except that the filler was 30 grams of hollow spherical particles of HDPE having an outer diameter of 8 mm and an inner diameter of 5 mm. The obtained sample was denoted as C4, and 2000 batteries were prepared accordingly.

Tests

The cycle performance, battery capacity, battery inner resistance of the battery samples TCl, Cl, C2, C3 and C4 were tested below.

The Cycle Performance Test

The cycle performance test was performed by using the equipment BK-7024L/60 commercially available from Guangdong Lanqi Electronic Experiment Co. Ltd. The operation conditions were as follows: constant current: about 0-60A; current resolution: about 10 mA; current set accuracy: about ± (0.1% RD+0.1% FS); test accuracy: about ± (0.1% RD+0.1% FS); voltage test range: about 0-5V; voltage resolution: about 1 mV; voltage to be tested range: about 2.5-4.5 V; constant voltage set range: about DC 2.5-4.5V; constant voltage set accuracy: about ± (0.1% RD + 0.1% FS); voltage test accuracy: about ± (0.1% RD+0.1% FS); time range: about 0-30000 min/work step; and precision: about ± 0.1%. The test results were shown in table 2.

The Inner Resistance Test

HK3560, Taiwan Hepu Inner Resistance Test Equipment was used and the test results were shown in table 1.

Battery Capacity Test

While testing the battery performance, the samples were placed into a BCT-0105 battery capacity tester commercially available from Shenzhen Chaosisi Electronic Co. Ltd. The test results were shown in table 1.

Table 1

Table 2

It can be seen from table 1 that the samples prepared according to the embodiments of the present invention may have a inner resistance up to about 1.0 mΩ which is lower than the 1.3 mΩ in the Comparative Example. The lower the inner resistance, the higher the safety performance. The battery capacity of the samples prepared according to the embodiments of the present invention reach 57500 mAh which is higher than the 55000 mAh in the Comparative Example. It can be seen from table 2 that after 500 cycles at normal temperature the sample in the Comparative Example has a much lower remaining capacity of 96.7%. After 200 cycles at 60^°Cthe sample in the Comparative Example has a much lower remaining capacity of 95.4%.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications all falling into the scope of the claims and their equivalents can be made in the embodiments without departing from spirit and principles of the invention.

Claims

What is claimed is:

1. A lithium ion battery, comprising: a shell, an electric core disposed in the shell with a space formed therebetween, and a non-aqueous electrolyte housed in the shell, wherein the space is filled with a non-aqueous electrolyte resistance filler.

2. The lithium ion battery according to claim 1, wherein the filler is a particulate material.

3. The lithium ion battery according to claim 2, wherein the particulate material comprises spheroidal particles having an average diameter of about 1 mm- 15 mm.

4. The lithium ion battery according to claim 3, wherein the particulate material comprises hollow spheroidal particles having an average inner diameter of about 1 mm- 10 mm and an average external diameter of about 2 mm- 15 mm.

5. The lithium ion battery according to claim 1, wherein the filler is one or more compounds selected from a group including polyphenylene sulfide, polyphenylether, polyethylene, polypropylene, polytetrafluoroethylene, polyperchlorethylene, high density polyethylene, and polyvinylidene chloride.

6. The lithium ion battery according to claim 1, wherein the electric core is formed by superposing or winding a positive electrode plate, a negative electrode plate, and a separator between the positive electrode plate and negative electrode plate.

7. The lithium ion battery according to claim 1, wherein the shell has a ratio of length:width:height of about 50-800:30-500:5-500.

8. The lithium ion battery according to claim 1, wherein the electric core has a ratio of length:width:height of about 45-795:25-495:5-100.