Background technology
In the suitability for industrialized production of at present domestic and international polymer Li-ion battery, the packaging technology of battery core body mainly contains two kinds: lamination and coiling.Winding process is suitable for making compact battery core body such as mp3 or bluetooth equipment battery.The battery of mobile phone, PDA, mobile DVD and the required bigger model of other portable electric appts then is suitable for lamination technology.
In the cyclic process of battery core body, the minority active material can come off from pole piece, if these active materials ooze out from the two ends of battery core body, will cause the inner micro-short circuit of battery core body, causes adverse consequencess such as self-discharge rate increase, low-voltage, capacity attenuation.In addition, in lamination technology, along with increasing of pole piece thickness, have the minority pole piece in the lug welding process and extract out, because the barrier film at battery core body two ends does not seal, pole piece can exceed barrier film and cause internal short-circuit.Therefore, when carrying out thick battery core body design, be subjected to a lot of limitations.
Summary of the invention
Technical problem to be solved by this invention is: provide a kind of and overcome above-mentioned deficiency, intercept the gel synergizing type polymer lithium ion battery of the active material seepage that comes off and reduce battery core body production fraction defective, the simple battery preparation method of technology.
The present invention is achieved through the following technical solutions:
A kind of gel synergizing type polymer lithium ion battery, comprise the battery core body that constitutes by anode pole piece, cathode pole piece, barrier film surface at positive and negative electrode place, described battery core body two ends is provided with polymer gel, described polymer gel is polymethyl methacrylate, polyacrylonitrile or contains Kynoar and the copolymer of hexafluoropropylene that wherein the molecular weight of hexafluoropropylene accounts for 10~20% of molecular weight of copolymer.
Further, the invention provides a kind of method for preparing gel synergizing type polymer lithium ion battery, it comprises the steps:
1) the low boiling point solvent water-bath with 300ml~500ml is heated to 40 ℃~50 ℃ and constant temperature;
2) slowly add polymethyl methacrylate, the polyacrylonitrile of 15~20g or contain Kynoar and the copolymer of hexafluoropropylene while stirring, stirred 3~4 hours, described polymer is dissolved in the described solvent fully, promptly form the gel precursor solution;
3) two ends with the battery core body behind lamination or the coiling apply the gel precursor solution, make the barrier film at two ends bond together;
4) the battery core body is placed in 60~75 ℃ dry 6~8 hours, removes the low boiling point solvent in the described solution;
5) more successively by the lug welding, the aluminum plastic film packing, electrolyte injects, and the polymeric preceramic body and the electrolyte at electric core two ends are soaked into fully, through electric core electrochemical activation, forms gel, makes gel synergizing type polymer lithium ion battery at last.
The present invention has following beneficial effect:
A. retention of charge: the battery core body that will be full of electricity (4.2V) is at room temperature opened a way and was placed 28 days, surveys its voltage and discharge capacity.
Test result: the battery core body that gluing is handled, the capacity hold facility is 95%, and voltage is about 4.1V; Do not make the battery core body that gluing is handled, the capacity hold facility is 87%, and voltage is about 3.97.
B. cycle performance: 1C discharged and recharged for 300 weeks, the battery core body that gluing is handled, residual capacity is more than 70%, and does not make the battery core body that gluing is handled, after 100 weeks of circulation, capacity attenuation is accelerated, and 300 all circulation volumes are 50~60%, and the pole piece two-end thickness obviously increases simultaneously, tomography shape projection is arranged, dissect the back and find, on the negative plate especially negative pole two to make a clean sweep of material serious, dendrite is met water and is promptly fired; And the battery core body that gluing is handled, the back dissection of 300 week of circulation finds that two-end thickness does not have significant change, barrier film still bonds together, positive/negative plate is come by obstruct fully, and the active material that the minority pole piece comes off still rests in the middle of the pole piece, does not cause the inner micro-short circuit of battery core body.
Therefore, the battery core body that gluing is handled, retention of charge improves, cycle performance strengthens (decay is slowed down), the phenomenon that pole piece thickens no longer appears in the battery core body two ends after the long-term circulation (more than 300 weeks), and in addition, high internal resistance, low-voltage phenomenon also have clear improvement.