CN1419308A - Safety high-energy lithium ion electric core and making method thereof - Google Patents

Abstract

The invention relates to a lithium cell with high capacity. The lithium cell with the capacity of more than 2 Ah or what is called the dynamic cell has the possibility of ignitino or explosion for its hgh density of energy when the cell gets out of order, fall into fail, or be used improperly such as the cell is pressed with high pressure, pierced with a needle, short-circuited or put in a high temperature environment. The person and property safety is threatened greatly. The safety design and manufacture process of the invention can prevent the ignition or explosion of the cell.

Description

A kind of safe high-energy lithium-ion electric core and manufacture method thereof

Technical field the present invention is relevant with jumbo lithium ion battery.

Background technology is in recent years along with the development of technology such as electric bicycle, electric automobile, mine lamp, the lithium ion battery little to volume, that energy density is high moves the energy, as capacity more than 2Ah lithium-ion electric core or be called electrokinetic cell and proposed urgent demand.

On the other hand; the lithium-ion electric core that energy density is high; when charger or protective circuit break down or lost efficacy; or other misuses; be subjected to all might taking place on fire under the situations such as powerful extruding, acupuncture, short circuit, high temperature as battery or blast; thereby the person and property safety to the user cause very big threat, hampered the safe handling of lithium ion battery greatly and popularize before problem does not have to solve.

Therefore, for preventing that the higher lithium ion battery of store electricity chemical energy from taking place on fire or blast, need carry out systematically Safety Design and manufacturing to most crucial lithium-ion electric core, single safeguard procedures are difficult to guarantee the fail safe of electric core, such as the PP/PE/PP composite diaphragm that adopts usually, when electric in-core portion temperature rises to 135 ℃, can produce barrier film closes, stop the migration of lithium ion, but often overcharge at big electric current, or barrier film can not closed moment fully during short circuit, and thermo-lag effect, electricity in-core portion temperature can continue to increase, electrolyte also can continue to decompose, the interior pressure continues to increase, this may cause barrier film Yin Wendu higher and occur sharply shrinking, the short circuit of positive/negative plate occurrence of large-area, at this moment energy can sharply discharge moment, organic bath is heated and takes place violent the decomposition, the electricity core can take place on fire, blast, so how the high lithium-ion electric core of capacity guarantees that the large tracts of land short circuit does not appear in positive/negative plate, control electric in-core portion's electrolyte decomposition and temperature, it is that solution is on fire that pressure raises, the important channel of blast.

Traditional cylindrical machinery seals lithium-ion electric core, adopt the aluminium flake indentation explosion-proof, in fact since the opening pressure precision generally at ± 0.5MPa, the opening pressure precision is low, the opening pressure height overcharges time electricity in-core temperature and rises too high when can cause, barrier film shrinks severe, and battery takes place, and probability on fire, blast is higher, even when explosion-proof valve is opened sometimes and do not explode and subsequent explosion takes place behind certain hour; The big capacity of mechanical in addition mouth-sealing method manufacturing electricity core has very big difficulty such as square 10Ah electricity core, exist rate of finished products low, seal to change into and be difficult for getting rid of the gas that produces when changing into and easily cause electric core bulge or the like disadvantage.

During the design of general lithium ion battery at the outside series connection of electric core PPTC thermistor, purpose is that resistance increases experience heat when electric core temperature raises after, and charging current reduces, and controls the energy accumulation of electric in-core portion, because thermo-lag and speed of expansion are slow, the control effect is still waiting to improve during actual the use.Welded lithium-ion electric core is inner if adopt PPTC, because can not be as the lithium-ion electric core of mechanical enclosuring structure, there is the sealed insulation pad that PPTC and electrolyte are kept apart, therefore, electrolyte can take place important motion device one polymer among the PPTC is played corrosiveness, directly cause PPTC to lose efficacy.

Summary of the invention is for avoiding above-mentioned defective, produce a kind of capacity and be higher than the still intrinsically safe lithium-ion electric core of 2Ah, the present invention proposes following method and structure design, adopt laser welding between electricity core cover plate and the housing, housing both can be that the band bottom shell body also can be the housing of making at square tube or the pipe weldering end; Adopt the opening chemical synthesis technology to replace original mechanical sealing process; Temperature control element design is in electric in-core portion, so that experience electric core temperature inside more quickly, allow by normal safe current during the temperature control element design, just in short circuit or overcharge or just work during unexpected high temperature, design principle is to reduce electric current or open circuit before sharply shrinking appears in barrier film, temperature control element both can adopt fusing point to be lower than 130 ℃ low melting point alloy, also can adopt the thermistor element (PPTC) of positive temperature coefficient.Temperature control element is connected between one of them pole and lug of electric in-core portion; The equal explosion-proof copper film of good accurate, the low-pressure startup of soldering in advance of upper cover plate or lower cover or the two in addition, in electric core temperature, when interior pressure is not too high, can open ejection high-temperature gas and electrolyte, take away the part heat, explosion-proof copper film opening pressure precision is controlled at ± 0.2MPa, opening pressure is opened to good to be controlled at 0.3-0.7MPa in the 0.2-1.5MPa scope.

It is the low melting point alloy manufacturing of 75-130C that temperature control element adopts fusing point, is good with fusing point in 75-100 ℃ of scope wherein, material main component and content following (wt.%): Bi 30-70, Pb 10-50, Sn 10-45, In 0-28.Low-melting alloy carried out surfacecti proteon before being connected on the pole handles, with avoid its with pole material and ear pole material between and alloy inside corrode because of electrode potential is different.Surfacecti proteon is handled and can be adopted protection retes such as electroplating Cu or Ni or Electroless Plating Ni-B or Ni-P or to apply not the elastic attachment adhesive that reacts with electrolyte, also can with after pole be connected with lug to connecting portion coating fluid sealant.Fusing disconnects when guaranteeing that temperature is higher than the fusing point of low-melting alloy, requires the metallic diaphragm of plating thin what guarantee to try one's best under the anticorrosion prerequisite, is generally less than 0.05mm; Also can be at temperature control element two ends metal lining coating, middle one section is not plated, but coating does not form thin protective film with the elastic attachment adhesive that electrolyte reacts.In addition for preventing that the melt that melts under the drippage of back from overlapping short circuit with positive/negative plate, place a plastics collecting board in the low-melting alloy bottom, the melt and positive/negative plate, the barrier film that fall are kept apart, the plastics collecting board can adopt manufacturings such as polypropylene material or polytetrafluoroethylmaterial material, the periphery of collecting board can have been made chimb, have narrow groove on the collecting board, allow lug to pass.

Temperature control element also can adopt the polymer thermistor material (PPTC) of positive temperature coefficient to make, the elastic attachment adhesive film that before being connected on the pole composite material position surface-coated is not reacted with electrolyte.

Adopt the present invention, can be with electrolyte decomposition reaction and electric in-core portion's heating decay or termination fast, control electric in-core portion's temperature rise and pressure, guarantee that barrier film can occurrence of large-area not melt, be unlikely the short circuit of positive/negative plate occurrence of large-area, the electricity core can not blasted and be on fire, and the fail safe of electric core, reliability are very high.

Embodiment 10Ah rectangular lithium ion electricity core, housing and cover plate all adopt 304 stainless steels, and explosionproof hole is opened at the upper cover plate center, and the hole is of a size of: 8*18, vacuum brazing copper thickness: 15 microns; The negative pole pole adopts the fine copper manufacturing, the bottom connects the low-melting alloy of 92 ℃ of fusing points, the alloy material composition is: Bi 50, Pb 30, Sn 20, alloy sheet thickness 3mm, wide 10mm, long 20mm, two has connecting hole, and middle 3mm applies fluid sealant, two ends electro-coppering, copper coating thickness 0.04mm, negative lug adopts the copper strips of an end perforate, and the aluminium strip of perforate in the middle of positive pole ear adopts adopts bolt tight with low-melting alloy after negative lug being passed the narrow groove of plastic septum, positive pole ear adopts bolt tight with the junction of positive terminal bottom after passing the narrow groove of plastic septum, the high 3mm in anti-limit around the plastic septum; The upper cover plate seal is assembled back and housing spot welding location, laser welding upper cover plate and housing then, will be after the vacuumize of electric core semi-finished product inject electrolyte by liquid injection hole, change into after sticking gummed paper, changing into finishes tears gummed paper off and with stainless steel ball liquid injection hole is sealed.The electric core of making is done safety test, and 3C/10V overcharges, short circuit, acupuncture, extruding are all not on fire, do not explode electric core safety.

Claims (9)

1. safe high-energy lithium-ion electric core and manufacture method thereof, it is characterized in that, upper cover plate has two positive and negative terminals of drawing, between electric in-core one of them pole of portion and lug, be serially connected with temperature control element, have the Copper Foil rupture pressure disc that explosionproof hole and soldering have low-pressure to start on the cover plate in advance, the electric core shell body adopts laser welding sealing with cover plate, the opening chemical synthesis technology.

2. temperature control element according to claim 1 is characterized in that, temperature control element employing fusing point is 75-130 ℃ low melting point alloy manufacturing, is good with fusing point in 75-100 ℃ of scope wherein.

3. temperature control element according to claim 1 is characterized in that, temperature control element adopts the thermistor material manufacturing of positive temperature coefficient, the elastic attachment adhesive film that surface-coated does not react with electrolyte before being connected on the pole.

4. Copper Foil rupture pressure disc according to claim 1 is characterized in that the rupture pressure disc opening pressure is controlled at 0.2-1.5MPa, is good with the 0.3-0.7MPa unlatching.

5. temperature control element according to claim 2 is characterized in that, low-melting alloy carried out surfacecti proteon before being connected on the pole handles.

6. temperature control element according to claim 5, it is characterized in that, the coats of metal such as Cu, Ni or Ag handle to adopt are electroplated in the low-melting alloy surfacecti proteon, also can Electroless Plating Ni-B or the elastic attachment adhesive that do not react with electrolyte of protection rete such as Ni-P or coating.

7. temperature control element according to claim 5 is characterized in that, temperature control element two ends metal lining coating, and middle one section is not plated, but coating does not form rete with the elastic attachment adhesive that electrolyte reacts.

8. temperature control element according to claim 2 is characterized in that, temperature control element and below the positive/negative plate barrier film between a plastic septum is arranged, its periphery is made chimb, has narrow groove on the collecting board, allows lug to pass.

9. low-melting alloy according to claim 2 is characterized in that alloying component is as follows: Bi 30-70, Pb 10-50, Sn 10-45, In 0-28.