CN2672885Y

CN2672885Y - Lithium ion secondary cell

Info

Publication number: CN2672885Y
Application number: CNU2003201253480U
Authority: CN
Inventors: 刘卫平; 刘斯源; 陈署初; 彭高平; 邓鹏�
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2003-12-26
Filing date: 2003-12-26
Publication date: 2005-01-19
Anticipated expiration: 2013-12-26

Abstract

The utility model discloses a lithium ion secondary battery, which comprises a core component formed by a positive electrode slice, a negative electrode slice, a membrane and electrolyte while the core component and the electrolyte are installed in the battery case, wherein the core component in the battery case has a gap along the overlap direction of the slices and the gap width is 3-20% of the thickness of the overlap part of the core component. The utility model has the advantages of slow capacitance attenuation and excellent circulating performance.

Description

Lithium rechargeable battery

[technical field]

The utility model relates to lithium rechargeable battery, relates in particular to the lithium rechargeable battery that a kind of capacity attenuation is slow, cycle performance is outstanding.

[background technology]

When lithium rechargeable battery was widely used as the energy of each class of electronic devices, people were also more and more higher to the requirement of battery performance.No matter be that to have a capacity big, the cylinder type lithium ion secondary battery that energy density is high, the square lithium ion secondary battery of still suitable each electronic product, people are for the consideration in its service time and useful life, not only require the battery initial capacity to want high, but also require battery capacity attenuation in repeated charge slow, and show excellent cycle performance, prolong the useful life of battery.

Each present battery production producer is all at the content that increases anode and cathode active materials in the battery as best one can, and purpose is to improve the capacity of battery.And this way just makes in the battery case that the positive and negative electrode of taking in the effective space is more and more crowded, though the initial capacity of battery is higher, but discharge and recharge in the use because the expansion of the crowded and pole piece of pole piece, just make the electrolyte between pole piece be extruded, finally cause the capacity of battery to be decayed fast, shortened the cycle life of battery greatly.

And lithium ion battery discharges and recharges normally and necessarily requires to have between positive and negative plate an amount of electrolyte to support.The electrolyte content deficiency will cause electrode charge and discharge insufficient, thereby the capacity of battery is decayed, reduction useful life, also can make simultaneously battery produce a large amount of heat in overcharging and make the too high and damage battery of the temperature of battery discharging and recharging because of the increase of the internal resistance of cell.

In Japanese patent application publication No. is in the patent of flat 1-294373, proposed to make the above space of average every 1AH Capacity design 0.3cc in the non-aqueous secondary batteries, but this space is arranged on battery upper end or whirlpool shape battery middle part, and size is regulated by the amount that adds electrolyte.The gas that makes battery produce when repeated charge like this has living space and holds, and can not make the battery breakage, thereby improves the trustworthiness in the battery charging and discharging use.Yet this way still can not guarantee the amount of the electrolyte between pole piece, electrolyte also can be extruded to battery upper end or middle part when pole piece expands, can't participate in storing the electricity reaction, can't fundamentally solve the fast problem of battery capacity decay, the number of times capable of circulation of battery does not still improve.

[utility model content]

The purpose of this utility model is to provide the lithium rechargeable battery that a kind of capacity attenuation is slow, cycle performance is outstanding.

The purpose of this utility model is achieved through the following technical solutions:

A kind of lithium rechargeable battery, comprise that the pole piece assembly and the electrolyte that are formed by positive plate, negative plate, barrier film are accommodated in the battery case jointly, wherein, along leaving the gap on the overlapping direction of sheet, its gap width is 3～20% of a pole piece assembly lap thickness to described pole piece assembly in battery case.

Further be distributed in equably between the overlapping sheet and sheet in the gap of leaving on the overlapping direction of sheet for described pole piece assembly.

Further the preferred gap width is 5～15% of a pole piece assembly lap thickness.

The advantage of the utility model lithium rechargeable battery is: by leave suitable gap between the positive and negative plate of pole piece assembly, can guarantee battery after injecting electrolyte and the electrolyte between the charge and discharge process pole piece after this be not extruded, thereby obtain the lithium rechargeable battery that capacity attenuation is slow, cycle performance is outstanding.

[description of drawings]

Fig. 1 is the generalized section of a kind of embodiment of the utility model lithium rechargeable battery.

Fig. 2 is the cross section vertical view of Fig. 1 lithium rechargeable battery.

The state diagram of overlooking that Fig. 3 puts into battery case for the scroll pole piece assembly of battery among Fig. 1.

[embodiment]

Below in conjunction with accompanying drawing the utility model is further described.

Please refer to Fig. 1 and Fig. 2, be the generalized section of the lithium rechargeable battery of a kind of embodiment of the utility model.This battery is a cylindrical battery, comprise that the pole piece assembly 4 and the electrolyte that are formed by positive plate 1, negative plate 2, barrier film 3 are accommodated in the battery case 5 jointly, wherein pole piece assembly 4 is a scroll, form by positive and negative plate and membrane coil are rich, in battery case,, that is: radially leave gap 6 along scroll pole piece assembly 4 along leaving the gap on the overlapping direction of sheet.This gap is distributed between the pole piece of each volume comparatively equably, and its gap width is 3～20% of a pole piece assembly lap thickness.For its pole piece assembly lap thickness of this cylindrical battery is the desirable external diameter of scroll pole piece assembly.Its desirable external diameter refers to: during volume was rich, the central shaft of the rich certain diameter of positive and negative plate and barrier film was seamlessly closely rolled up the rich pole piece assembly external diameter (please refer to the assembly of pole piece shown in Fig. 3) that obtains.

In this lithium rechargeable battery, leave 3～20% gap width of the desirable external diameter of pole piece assembly between positive and negative plate altogether, can guarantee battery after injecting electrolyte and the electrolyte between the charge and discharge process pole piece after this be not extruded.If this excesssive gap, surpass 20% of the desirable external diameter of pole piece assembly, battery active material on the positive/negative plate in charge and discharge process is peeled off even is come off from collector body easily, thereby the capacity of lithium ion battery is lost, and finally shortens the cycle life of lithium ion battery; If this space is too small,, the effect that prevents that electrolyte from extruding will do not had less than 3% of the desirable external diameter of pole piece assembly.In practice, the preferred gap width is 5～15% of a pole piece assembly lap thickness.Have the battery of the pole piece making of such gap width, capacity attenuation is slow, cycle performance is outstanding.

In lithium rechargeable battery, the pole piece of cylindrical battery is longer, and the general rich mode of volume that adopts is made scroll pole piece structure.This kind battery just more will be reserved the gap of the desirable external diameter 3～20% of its pole piece in when design, and such battery not only can keep good initial capacity, and capacity attenuation speed slows down greatly, and cycle performance improves greatly.

For square lithium ion secondary battery, no matter its pole piece is the rich formula or stacked of volume, or other modes, as long as sheet and the overlapping part of sheet are arranged, adopts the utility model all can obtain certain effect.And for rectangular cell, the overlapping direction of sheet is the stacked direction of pole piece assembly (being generally the thickness direction of battery), and lap thickness is the thickness of cell thickness direction pole piece assembly.

Making and test with cylindrical lithium ion secondary battery is example below, further the utility model described.

[embodiment]

Design also make to be adopted cylindrical lithium ion secondary battery 18650 types of the present utility model (can with reference to figure 1), at first determines battery positive and negative plate, the thickness of barrier film and the relation of length, carries out battery then and makes.If following parameter:

T _R: gap width;

T _C: the battery case internal diameter;

T _D: the desirable external diameter of the back Battery Pole Core of reeling;

T _P: the average thickness of positive plate during assembling;

L _P: the total length of positive plate during assembling;

T _N: the average thickness of negative plate during assembling;

L _N: the total length of negative plate during assembling;

T _S: the average thickness of barrier film during assembling;

L _S: the total length of barrier film during assembling;

D: the diameter of used volume pin during the coiling battery pole piece.

P: clearance rate, P=T _R/ T _D

Battery case internal diameter T wherein _C=17.6mm according to the structure of this cylindrical battery, has following formula to set up: 1, T _R=T _C-T _D

2、

T_{P} \times L_{P} + T_{N} \times L_{N} + T_{S} \times T_{S} = \frac{1}{4} π ({T_{D}}^{2} - D^{2})

That is:

T_{D} = \frac{\sqrt{4 (T_{P} \times L_{P} + T_{N} \times L_{N} + T_{S} \times L_{S}) + π D^{2}}}{\sqrt{π}}

Exist according to the given P value of the utility model earlier, try to achieve T then _D, obtain the thickness of positive plate, negative plate and barrier film and the relativeness of length, can draw the thickness and the length parameter of positive plate, negative plate and barrier film after adjusting according to other performance requirement of battery again.

In the present embodiment, positive pole: adopt positive active material LiCoO2, conductive agent acetylene black, adhesive PVDF mixed in NMP by weight 100: 7: 5.Be two-sided dressing on the aluminium foil of 20 μ m at thickness, smear evenly.The baking drying is suppressed afterwards in vacuum oven.

Negative pole: adopt negative electrode active material graphite, adhesive PVDF mixed in NMP by weight 100: 10.Be two-sided dressing on the Copper Foil of 15 μ m at thickness, smear evenly that baking is dry in vacuum oven.Suppress after the vacuumize.

Barrier film: adopt the thick PP/PE/PP material of 25 μ m.

Thick according to given its sheet of this battery: anodal T _P=0.160mm, negative pole L _P=0.150mm, barrier film T _S=0.025mm.Determine length of a film according to above-mentioned formula again, see the following form 1:

Table 1

P(％)	Lp (mm)	Ln (mm)	Ls (mm)
P(％)	Lp (mm)	Ln (mm)	Ls (mm)	2％	595	660	1300
3％	583	648	1275	2％	595	660	1300
3％	583	648	1275	4％	570	635	1251
5％	559	624	1227	4％	570	635	1251
5％	559	624	1227	8％	525	590	1160
10％	504	569	1118	8％	525	590	1160
10％	504	569	1118	13％	475	540	1060
15％	457	522	1023	13％	475	540	1060
15％	457	522	1023	16％	448	513	1006
20％	415	480	940	16％	448	513	1006
20％	415	480	940	22％	400	465	909
25％	378	443	866	22％	400	465	909

More than in the table, the P value gets 2%, 3%, 4%, 5%, 8%, 10%, 13%, 15%, 16%, 20%, 22%, 25% respectively, makes battery A, B, C, D, E, F, G, H, I, G, K, L.In manufacturing process, positive and negative plate and membrane coil are had mercy on into scroll pole piece assembly, at first obtain desirable pole piece (see figure 3), be placed in the battery case, (this gap width both had been T because its periphery leaves gap 6 ' with internal surface of battery shell _R).The pole piece assembly begins to unclamp in battery case, makes gap 6 ' be distributed in comparatively equably between the overlapping sheet and sheet, injects electrolyte, will have some gaps to store electrolyte between each volume of battery pole piece.

[comparative example]

Make the comparative example battery, this Battery Pole Core inter-module is not reserved the gap, and remove positive and negative plate and barrier film length and be respectively 605mm, 670mm, outside the 1320mm, all the other are with the embodiment battery.But after this battery volume was rich, the desirable external diameter of scroll pole piece is near battery case internal diameter 17.6mm, and was very close to each other.

Battery performance test:

The foregoing description, comparative example battery are done cycle performance test: make continuous charge-discharge test with the electric current of 1CmA, record when the capacity of battery drop to its initial capacity 80% the time the cycle-index of process.Test result sees the following form 2:

Table 2

		T _R(mm)	P	Cycle-index (inferior) when capacity is 80 % of initial capacity
		T _R(mm)	P		The comparative example battery		0	0	87
The embodiment battery	A	0.35	2％	126	The comparative example battery		0	0	87
	A	0.35	2％	126	B	0.51	3％	268
	C	0.68	4％	322	B	0.51	3％	268
	C	0.68	4％	322	D	0.84	5％	378
	E	1.30	8％	435	D	0.84	5％	378
	E	1.30	8％	435	F	1.60	10％	423
	G	2.02	13％	378	F	1.60	10％	423
	G	2.02	13％	378	H	2.30	15％	355
	I	2.43	16％	289	H	2.30	15％	355
	I	2.43	16％	289	J	2.93	20％	255
	K	3.17	22％	202	J	2.93	20％	255
	K	3.17	22％	202	L	3.52	25％	167

As can be seen from the above table: the utility model battery, pole piece clearance rate are 3～20% o'clock, and battery capacity is that 80% o'clock cycle-index of initial capacity is more than 250 times; The pole piece clearance rate is 5～15% o'clock, and battery capacity is that 80% o'clock cycle-index of initial capacity is more than 350 times.Its cycle performance is outstanding, and capacity attenuation is slow.

Above-mentioned execution mode just embodies a kind of scheme of technical solutions of the utility model; for those skilled in the art; no matter which kind of change it does to the pole piece modular construction; as long as in the utility model technical scope; all embodied principle of the present utility model, belonged within the protection range of the present utility model.

Claims

1, a kind of lithium rechargeable battery, comprise that the pole piece assembly and the electrolyte that are formed by positive plate, negative plate, barrier film are accommodated in the battery case jointly, it is characterized in that: along leaving the gap on the overlapping direction of sheet, its gap width is the 3-20% of pole piece assembly lap thickness to described pole piece assembly in battery case.

2, lithium rechargeable battery as claimed in claim 1 is characterized in that: described pole piece assembly is distributed between the overlapping sheet and sheet equably in the gap of leaving on the overlapping direction of sheet.

3, lithium rechargeable battery as claimed in claim 1 is characterized in that: described pole piece assembly is 5～15% of a pole piece assembly lap thickness along the gap width that leaves on the overlapping direction of sheet in battery case.