CN102332558A

CN102332558A - Lithium-ion battery and its positive pole piece

Info

Publication number: CN102332558A
Application number: CN201110067954A
Authority: CN
Inventors: 周铁刚; 涂健; 陈轩
Original assignee: Ningde Amperex Technology Ltd; Dongguan Amperex Electronics Technology Ltd; Dongguan Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd; Dongguan Amperex Electronics Technology Ltd; Dongguan Amperex Technology Ltd
Priority date: 2011-03-22
Filing date: 2011-03-22
Publication date: 2012-01-25

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery and a positive pole piece thereof, which comprise a current collector, a bottom layer coated on the current collector, and a top layer coated on the bottom layer, wherein the two layers form a positive pole material layer.

Description

Lithium ion battery and anode pole piece thereof

Technical field

The present invention relates to technical field of lithium ion, especially a kind of lithium ion battery and anode pole piece thereof.

Background technology

Lithium ion battery is a kind of battery with higher energy density and good environmental-protecting performance, and it has advantages such as energy height, reliability is high, processability is good, thereby is used on the portable electric appts gradually.

Electric core in the lithium ion battery generally comprises positive plate, barrier film and the negative plate that mutual superposition is reeled, and barrier film is interval between the adjacent positive and negative plate with two kinds of pole pieces insulation, is used to keep electrolyte simultaneously.Electricity core and electrolyte all are to put into battery case or packaging film, are used for guaranteeing that lithium ion battery can operate as normal under airtight environment.

Positive plate comprise plus plate current-collecting body that general employing aluminium foil is made and attached on the plus plate current-collecting body, contain the anodal diaphragm of positive active material.Between positive active material and positive active material and aluminium foil rely on binding agent to bond together.Because cathode active material self characteristics influence; Such as compacted density, and the positive electrode of relatively low compacted density (such as LiFePO4, lithium manganate material); Because the compacted density that self is lower; Even cause positive electrode active materials after colding pressing, to contact still bad (like Fig. 1) between its particle and the collector, cause the variation that circulates, the high rate performance variation.

Summary of the invention

The objective of the invention is to: provide a kind of positive active material colding pressing after, to have good the contact and the anode pole piece of adhesive property between its particle and the collector to prior art problems.Adopt this anode pole piece lithium ion battery its have good high rate performance, and excellent cycle performance.

In order to achieve the above object, the present invention adopts following technical scheme:

A kind of anode slice of lithium ion battery comprises collector; Be coated in the bottom on the collector, be coated in the top layer on the bottom, two-layer composition positive electrode material layer, the compacted density of described bottom is big than top layer.

Wherein, further limit as the present invention, the thickness of said bottom is 0.01um～30um.

Wherein, the thickness of said bottom further is preferably 0.5um.

Wherein, further limit, contain conductive agent and binding agent in the said positive electrode material layer at least as the present invention.

Wherein, further limit as the present invention, said conductive agent and the binding agent solid content in positive electrode material layer is respectively 1%～90%, 1%～90%.

Wherein, further limit as the present invention, described binding agent be in polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), the rubber (SBR) one or more, its solid content in positive electrode material layer further is preferably 1%～75%.

Wherein, further limit as the present invention, said conductive agent is one or more in conductive carbon black, gas-phase carbon fiber, the CNT, and its solid content in positive electrode material layer further is preferably 1%～75%.

A kind of anode slice of lithium ion battery its preparation method may further comprise the steps: at first, preparation has higher pressure real density base pastes, gets binding agent and is dissolved in the solvent, and stirring and dissolving fully back forms settled solution; The bottom active material that in above-mentioned settled solution, adds conductive agent and higher pressure real density; The slurry that stirs is coated on the anode collection surface; Evaporation removes and desolvates, and obtains having the pole piece of higher pressure real density active material, and this pole piece is through subsequent use behind the cold pressing process; Secondly, prepare the top level slurry of relatively low compacted density, get binding agent and be dissolved in the solvent, stirring and dissolving fully back forms settled solution; In above-mentioned settled solution, add the top layer active material of conductive agent and relatively low compacted density, the slurry that stirs is coated on the surface of bottom, and evaporation removes and desolvates, and obtains having the anode pole piece of different compacted density structures.

Wherein, as the present invention's qualification in a more progressive step, the compacted density of said bottom is than the big 0.1 gram/cubic centimetre of the compacted density～5 gram/cubic centimetres of top layer.

The present invention also provides a kind of lithium rechargeable battery; This battery comprises battery container, electrode group and electrolyte; Said electrode group and electrolyte are sealed in the battery container; Said electrode group comprises positive pole, negative pole and the barrier film between both positive and negative polarity, said just very above-mentioned anode slice of lithium ion battery.

Beneficial effect of the present invention: the present invention adopts and is coated in the bottom on the collector; Be coated in the top layer on the bottom, two-layer composition positive electrode material layer, the compacted density of described bottom is big than top layer; This technical scheme has the bottom of relatively high pressure real density through cold pressing process; Particle can embed in the plus plate current-collecting body, has excellent contact with collector, has obviously improved low compacted density cathode film sheet and the big problem of plus plate current-collecting body contact impedance; Improve the chemical property of lithium ion battery, improved the high rate performance and the cycle performance that discharge and recharge.

Description of drawings

Below in conjunction with accompanying drawing and each specific embodiment, the present invention and useful technique effect thereof are elaborated, wherein:

Fig. 1 is the cyclic curve figure that the battery of based lithium-ion battery positive plate embodiment 1 of the present invention discharges with 0.5C charging 0.5C in the time of 25 ℃;

Fig. 2 is the cyclic curve figure that the battery of based lithium-ion battery positive plate embodiment 2 of the present invention discharges with 0.5C charging 0.5C in the time of 25 ℃;

Fig. 3 is no primer coating technology lithium ion battery cyclic curve figure with 0.5C charging 0.5C discharge in the time of 25 ℃;

Fig. 4 is the test curve of the battery 1C discharge-rate of anode slice of lithium ion battery embodiment 1 of the present invention;

Fig. 5 is the test curve of the battery 3C discharge-rate of anode slice of lithium ion battery embodiment 1 of the present invention;

Fig. 6 is the test curve of the battery 1C discharge-rate of anode slice of lithium ion battery embodiment 2 of the present invention;

Fig. 7 is the test curve of the battery 3C discharge-rate of anode slice of lithium ion battery embodiment 2 of the present invention;

Fig. 8 is the test curve of the anode slice of lithium ion battery 1C discharge-rate of prior art;

Fig. 9 is the test curve of the anode slice of lithium ion battery 3C discharge-rate of prior art.

Embodiment

Be further described for the present invention below in conjunction with embodiment.

Embodiment 1:

At first preparation has higher pressure real density base pastes, gets binding agent PVDF and is dissolved in the solvent, and stirring and dissolving NMP fully back forms settled solution; The bottom active material that in above-mentioned settled solution, adds Super-P (conductive carbon black) conductive agent and higher pressure real density (compacted density 4.2 gram/cubic centimetres) cobalt acid lithium; Wherein cobalt acid lithium, Super-P (conductive carbon black), PVDF are 95.0: 3.0: 2.0 according to mass ratio; Solid content 70%; The base pastes that stirs is coated on the anode collection surface, and evaporation removes and desolvates 10 microns of coating thicknesss; Obtain having the pole piece of higher pressure real density active material, this pole piece is through subsequent use behind the cold pressing process.

Secondly, prepare the top level slurry of relatively low compacted density, get the PVDF binding agent and be dissolved in NMP (N-methyl pyrrolidone) solvent, stirring and dissolving fully back forms settled solution; The LiFePO4 top layer active material that in above-mentioned settled solution, adds Super-P (conductive carbon black) conductive agent and relatively low compacted density (compacted density 2.2 gram/cubic centimetres); Wherein LiFePO4, Super-P (conductive carbon black), PVDF are 85.0: 5.0: 10.0 according to mass ratio; The slurry that stirs is coated on the surface of bottom; Evaporation removes and desolvates, and obtains having the anode pole piece of different compacted density structures.This anode pole piece is cut (being about to the size that required size was cut out, cut into to negative plate) according to design size, and the positive pole ear that again that 0.1mm is thick lug aluminum strip is processed is connected on the aluminium foil, makes positive plate, sees Fig. 2.

Preparation negative plate: with graphite, Super-P, CMC (water based adhesive; Carboxymethyl cellulose), SBR (Styrene Butadiene Rubber; A kind of rubber) according to mass ratio 95.5: 1.5: 1.5: 1.5 add in the deionized waters; Mix and stir obtaining having the slurry of certain flowability, more above-mentioned slurry is coated in the two sides of the thick metal copper foil of 9 μ m, be dried into negative plate with certain flexibility.Through colding pressing, cut (being about to the size that required size was cut out, cut into to negative plate), will be connected on the Copper Foil with the negative lug that the thick nickel sheet of 0.1mm is processed again then, make negative plate.

Preparation lithium ion battery: process naked electric core to the positive plate of making, negative plate and barrier film (barrier film can adopt polypropylene (PP)-polyethylene (PE)-three layers of laminated film of polypropylene (PP) or polypropylene (PP) or polyethylene (PE) single thin film) through winding method; Then with the electric core battery packages shell (aluminum-plastic composite membrane of packing into; Aluminum hull or box hat) in, (electrolyte is with lithium hexafluoro phosphate (LiPF in it, to inject electrolyte ₆)) be lithium salts, the ethylene carbonate with 20%, 30% methyl ethyl carbonate and 50% dimethyl carbonate are solvent), again through change into, technology such as ageing makes the finished product battery.

A plurality of lithium ion battery samples to making by present embodiment carry out volume test, and test result is referring to table 1.

The battery capacity test result of table 1 embodiment 1

The sample sequence number	The charge/discharge multiplying power	Capacity data (mAh)
			1	0.5C/0.5C	1052
2	0.5C/0.5C	1058
			3	0.5C/0.5C	1056
4	0.5C/0.5C	1051
			5	0.5C/0.5C	1053
6	0.5C/0.5C	1057

Embodiment 2:

Present embodiment and embodiment 1 difference are: the bonding agent of described positive pole is CMC; Its solid content at positive electrode material layer is 15%, and with anode pole piece, cathode pole piece and barrier film adopt the mode of piling up to make naked electric core; Other is identical with embodiment 1, repeats no more here.

A plurality of lithium ion battery samples to making by present embodiment carry out volume test, and test result is referring to table 2.

The battery capacity test result of table 2 embodiment 2

The sample sequence number	The charge/discharge multiplying power	Capacity data (mAh)
			1	0.5C/0.5C	1056
2	0.5C/0.5C	1057
			3	0.5C/0.5C	1051
4	0.5C/0.5C	1054
			5	0.5C/0.5C	1054
6	0.5C/0.5C	1056

Comparing embodiment 1:

Please with reference to table 3 for the ease of explanation, describe technique effect of the present invention in detail below in conjunction with the test result of the battery capacity of prior art lithium ion battery.Wherein, the prior art lithium ion battery is a plus plate current-collecting body with the thick aluminium foil of 16 μ m, and anode pole piece adopts the active material single coated of cobalt acid lithium, and other cathode pole piece, lithium ion battery manufactured materials and step are identical with embodiment 1, repeat no more here.The test result of battery capacity is seen table 3.

The battery capacity test result of the traditional lithium ion battery of table 3

The sample sequence number	The charge/discharge multiplying power	Capacity data (mAh)
			1	0.5C/0.5C	1050
2	0.5C/0.5C	1052
			3	0.5C/0.5C	1050
4	0.5C/0.5C	1058
			5	0.5C/0.5C	1056
6	0.5C/0.5C	1053

Contrast through table 1 to table 3 can find out that capacity of lithium ion battery and the traditional handicraft of using the present invention to make are suitable.

See also Fig. 1 to 3, can contrast and find out, the lithium ion battery that uses the embodiment of the invention 1 and 2 making is under 25 ℃, and during with 0.5C charging, 0.5C discharge, cycle performance is better.

Can find out with Fig. 8-9 contrast from Fig. 4-7, utilize the made lithium ion battery of the present invention's technology, except that having excellent cycle performance, also have good discharge-rate performance.

Embodiment 3, are with embodiment 1 difference: bottom coating layer thickness is changed to 30 microns, and other is identical with embodiment 1, repeats no more here.

Embodiment 4, are with embodiment 1 difference: bottom coating layer thickness is changed to 0.01 micron, and other is identical with embodiment 1, repeats no more here.

Embodiment 5, are with embodiment 1 difference: bottom coating layer slurry solid content is changed to 75%, and other is identical with embodiment 1, repeats no more here.

Embodiment 6, are with embodiment 1 difference: bottom coating layer slurry solid content is changed to 1%, and other is identical with embodiment 1, repeats no more here.

Embodiment 7, are with embodiment 1 difference: bottom coating layer slurry conductive agent is changed to the gas-phase carbon fiber, and other is identical with embodiment 1, repeats no more here.

Embodiment 8, are with embodiment 1 difference: bottom coating layer slurry conductive agent is changed to CNT, and other is identical with embodiment 1, repeats no more here.

Embodiment 9, are with embodiment 1 difference: bottom coating layer slurry active material is changed to the cobalt acid lithium of submicrometer structure, solid content 1%, compacted density 0.1 gram/cubic centimetre; The upper strata active material changes to the LiFePO4 of nanostructure, compacted density 0.05 gram/cubic centimetre, and other is identical with embodiment 1, repeats no more here.

Embodiment 10, are with embodiment 1 difference: bottom coating layer slurry active material is changed to the cobalt acid lithium that compacted density is 4.5 gram/cubic centimetres, and the upper strata active material changes to LiFePO4, and other is identical with embodiment 1, repeats no more here.

In sum, the anode pole piece that the present invention adopts the double-coated layer of cloth replaces the anode pole piece of the single coated of traditional lithium ion battery, has obviously improved the discharge-rate performance of lithium ion battery, has improved the chemical property of lithium ion battery.

According to the announcement and the instruction of above-mentioned specification, those skilled in the art in the invention can also carry out suitable change and modification to above-mentioned execution mode.Therefore, the embodiment that discloses and describe above the present invention is not limited to also should fall in the protection range of claim of the present invention modifications more of the present invention and change.In addition, although used some specific terms in this specification, these terms are explanation for ease just, the present invention is not constituted any restriction.

Claims

1. A lithium-ion battery positive electrode sheet, comprising a current collector; the bottom layer coated on the current collector, the top layer coated on the bottom layer, and two layers form the positive electrode material layer, characterized in that: the compaction of the bottom layer The density is higher than that of the top layer.

2 . The positive electrode sheet of a lithium ion battery according to claim 1 , wherein the bottom layer has a thickness of 0.01 um to 30 um. 3 .

3. A lithium-ion battery positive pole piece according to claim 1, characterized in that: the thickness of the bottom layer is 0.5um.

4 . The anode sheet of a lithium ion battery according to claim 1 , wherein the anode material layer contains at least a conductive agent and a binder.

5. A lithium-ion battery positive electrode sheet according to claim 1, characterized in that: the solid content of the conductive agent and the binder in the positive electrode material layer are 0.1% to 90%, 0.1% to 90%, respectively. %.

6. A lithium ion battery positive pole piece according to claim 5, characterized in that: the binder is polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), rubber (SBR ), and its solid content in the positive electrode material layer is 1% to 75%.

7. A kind of positive pole piece of lithium ion battery according to claim 5, it is characterized in that: described conductive agent is one or more in conductive carbon black, gas-phase carbon fiber, nano-carbon tube, and it is in positive electrode material layer The solid content is 1% to 75%.

8. A kind of lithium-ion battery positive pole piece according to claim 1, is characterized in that: its preparation method comprises the following steps: first, prepare bottom layer slurry with higher compaction density, take binder and dissolve in solvent , stir and dissolve fully to form a clear solution; add conductive agent and higher compaction density bottom layer active material to the above clear solution, and evenly stir the slurry to coat the surface of the positive electrode current collector, and evaporate to remove the solvent to obtain a higher pressure The pole piece of solid density active material, the pole piece is used after the cold pressing process; secondly, prepare the top layer slurry with relatively low compaction density, take the binder and dissolve it in the solvent, and form a clear solution after stirring and dissolving fully; A conductive agent and a top-layer active material with a relatively low compaction density are added to the above clarified solution, the uniformly stirred slurry is coated on the surface of the bottom layer, and the solvent is evaporated to obtain positive electrode sheets with different compaction density structures.

9 . The positive electrode sheet of a lithium ion battery according to claim 8 , wherein the compacted density of the bottom layer is 0.1 g/cm 3 to 5 g/cm 3 larger than that of the top layer. 10 .

10. A lithium-ion secondary battery, the battery comprises a battery case, an electrode group and an electrolyte, the electrode group and the electrolyte are sealed in the battery case, the electrode group includes a positive pole, a negative pole and an electrode located between the positive and negative poles The separator between them is characterized in that, the positive pole is the positive pole piece of the lithium ion battery described in any one of claims 1-9.