CN104993145A - Electrode with fluorinated graphene as conductive agent and application in lithium ion batteries - Google Patents

Abstract

The invention uses the fluorinated graphene as the electrode of the conductive agent and its application in the lithium ion battery. Add 1-30% fluorinated graphene conductive agent to the positive electrode active material, add fluorinated graphene conductive additive to the positive electrode of the assembled lithium ion battery, and the lithium ion battery whose negative electrode is the same as the negative electrode of the existing industrialized lithium ion battery. The battery of the invention significantly improves the liquid retention coefficient of the electrolyte and improves the electrochemical performance of the battery.

Description

Electrode with fluorinated graphene as conductive agent and its application in lithium ion battery

technical field

The invention relates to the technical field of batteries, in particular to an electrode using fluorinated graphene as a conductive agent and its application in lithium ion batteries.

Background technique

At present, lithium-ion batteries have entered every aspect of people's lives, and conductive agents play an important role in lithium-ion batteries. At present, the conductive agents used in lithium-ion batteries mainly include carbon black, carbon nanotubes, nano-metal powders, and nano-carbon fibers. The wettability needs to be further improved.

Since Andre K. Geim (Andre K. Geim, University of Manchester, UK) prepared graphene materials in 2004, it has received widespread attention due to its unique structure and photoelectric properties. Graphene is hailed as a rising "new star" in the field of materials science and condensed matter physics. Its many novel and unique properties and potential applications are attracting many scientific and technological workers. Single-layer graphene has a large specific surface area, excellent electrical and thermal conductivity and low thermal expansion coefficient. Such as: 1. High strength, Young's molar weight, (1,100 GPa), breaking strength: (125GPa); 2. High thermal conductivity, (5,000 W/mK); 3. High electrical conductivity, carrier transport rate, ( 200,000 cm2/V*s); 4. High specific surface area, (theoretical calculation value: 2,630 m2/g). In particular, its high conductivity, large specific surface properties and its two-dimensional nanoscale structural properties of monomolecular layers can be used as electrode materials in supercapacitors and lithium-ion batteries.

Fluorinated graphene has high electrical conductivity and has a similar chemical composition to LiPF ₆ , the main component of the electrolyte, so it has good compatibility with the electrolyte.

Based on the above reasons, there is no report about fluorinated graphene as a battery conductor. We therefore propose the following inventions.

Contents of the invention

The object of the present invention is to provide an electrode using fluorinated graphene as a conductive agent and its application in lithium ion batteries.

As a new type of material, fluorinated graphene is used as a conductive agent in batteries, which can not only improve the conductivity of the electrode, but also improve the wettability of the pole piece and the electrolyte, thereby greatly reducing the lithium ion density. The polarization phenomenon in the charging and discharging process of ion batteries has broad application prospects in the battery field.

The technology of the present invention is as follows:

Fluorinated graphene or fluorinated graphene is mixed with the current commonly used conductive agent according to a certain ratio as the conductive agent, and the amount of fluorinated graphene accounts for 1-30% by weight of the entire positive electrode active material. If the fluorine If graphene is mixed with other conductive agents, the proportions a and b of several conductive agents satisfy a+b=1, and a and b are both less than 1 and greater than 0.

Then add the above-mentioned conductive agent into the positive electrode slurry of the lithium ion battery, mix evenly, and then complete the steps of coating, rolling, slitting, welding, winding, assembling, forming and volume separation. The negative pole is the same as the negative pole of the existing industrialized lithium ion battery.

The invention has the following advantages: 1. Improve the conductivity of the electrode; 2. Improve the wettability of the electrode and the electrolyte; thereby greatly reducing the polarization phenomenon in the charging and discharging process of the lithium ion battery and improving the electrochemical performance of the battery.

Detailed ways

Embodiment one:

Take 90Kg of lithium iron phosphate powder, 5Kg of fluorinated graphene, and 250Kg of 2% PVDF glue, mix evenly at high speed with a double-planetary vacuum mixer, and coat it on aluminum foil. The machine presses the pole pieces to 0.156-0.164mm, and then completes the follow-up sheet production, battery assembly and formation, and capacity separation processes according to the battery manufacturing process of 503759-850. The negative electrode is the same as the negative electrode of the existing industrial lithium-ion battery. The negative electrode uses graphite, sp, cmc and SBR system, and the ratio is C:sp:CMC:SBR=96:1:1.5:1.5.

In addition, 90Kg of lithium iron phosphate powder, 5Ksp conductive carbon black, and 250Kg of 2% PVDF glue were used as a comparative experiment.

After the battery is made, compare the electrolyte retention, internal resistance and battery rate cycle performance data.

The test data is as follows:

It can be seen from the data that the use of fluorinated graphene can significantly improve the rate and cycle performance of the battery.

Embodiment two:

Take 90Kg of lithium iron phosphate powder, 2.5Kg of fluorinated graphene, 2.5Kg of sp conductive carbon black, and 250Kg of 2% PVDF glue, stir them evenly with a double planetary vacuum mixer at high speed, and coat them on aluminum foil. The surface density of double-sided coating is 32mg/cm2, and then use the roll machine to press the pole pieces to 0.156-0.164mm, and then follow the 503759-850 battery manufacturing process to complete the subsequent film production, battery assembly, formation, and capacity separation processes. The negative electrode is the same as the negative electrode of the existing industrial lithium-ion battery. The negative electrode uses graphite, sp, cmc and SBR system, and the ratio is C:sp:CMC:SBR=96:1:1.5:1.5.

After the battery is manufactured, compare the electrolyte retention, internal resistance and battery rate cycle performance data.

The test data is as follows:

It can be seen from the above data that the effect of using the mixed conductive agent of fluorinated graphene and sp is also better than that of using sp conductive carbon black alone.

Claims (4)

1. one kind mixes electrode as conductive agent with fluorinated graphene or using fluorinated graphene and now conventional conductive agent according to certain proportioning, the percentage by weight that it is characterized in that adding fluorinated graphene in positive active material is the 1-30% of active material weight, if by fluorinated graphene and other conductive agents used in combination, the then proportioning a of several conductive agent, b meets a+b=1, and a, b are less than 1, be greater than 0.

2. as claimed in claim 1 mix electrode as conductive agent with fluorinated graphene or using fluorinated graphene and the conductive agent commonly used now according to certain proportioning, it is characterized in that getting positive active material and binding agent, add the mixture of fluorinated graphene that percentage by weight is active material weight 1-30% or fluorinated graphene and other conductive agents, after mixing, be coated on aluminium foil, then pole piece dried under vacuum 80-120 degree.

3. as claimed in claim 1 mix electrode as conductive agent with fluorinated graphene or using fluorinated graphene and the conductive agent commonly used now according to certain proportioning, its feature is when mixing as conductive agent using fluorinated graphene with other conductive agents, other conductive agents are conductive black, Graphene, carbon nano-fiber, carbon nano-tube, electrically conductive graphite and electrical-conductive nanometer metal dust.

4. as claimed in claim 1 mix electrode as conductive agent with fluorinated graphene or using fluorinated graphene and the conductive agent commonly used now according to certain proportioning, application in lithium ion battery, it is characterized in that assembled lithium ion battery is that to add fluorinated graphene be conductive agent to positive pole, and the lithium ion battery that negative pole is identical with existing industrialization lithium ion battery negative.