Positive electrode sheet of lithium iron phosphate type lithium ion battery, and preparation method thereof

Abstract

The present invention discloses a positive electrode sheet of a lithium iron phosphate type lithium ion battery, and a preparation method thereof. According to the present invention, a positive active material coating comprise a nano-lithium iron phosphate positive active material coating a and a nano-lithium iron phosphate positive active material coating b; nano-lithium iron phosphate positive active material slurry a is coated on a current collector; nano-lithium iron phosphate positive active material slurry b is coated on the nano-lithium iron phosphate positive active material coating a; electrode lugs are spot welded on reserved blank of the current collector. The method comprises the following steps that: A, a lithium iron phosphate positive active material is respectively mixed with a nano carbon black conductive agent, a polyvinylidene difluoride agglomerant and a N-methylpyrrolidone solvent according to the ratio to prepare the nano-lithium iron phosphate positive active material slurry a and the nano-lithium iron phosphate positive active material slurry b; B, the slurry prepared from the lithium iron phosphate are coated on a side or both sides of the current collector having a certain thickness to form the coatings; C, the positive electrode sheet having coatings is prepared. The lithium iron phosphate type lithium ion battery has characteristics of high capacity, high rate, good effect. With the positive electrode sheet provided by the present invention, the service life of the lithium ion battery is prolonged.

Description

technical field [0001] The invention relates to the field of chemical power supply, that is, battery manufacturing, in particular to a method for manufacturing positive pole pieces of lithium iron phosphate lithium ion batteries, which is suitable for manufacturing various types of primary and secondary lithium ion batteries. Background technique [0002] At present, the various types of lithium-ion battery positive pole pieces produced by the lithium-ion battery industry all use the structure of the positive pole piece as follows: single-layer single-side or single-layer positive active material with larger particle size (micron scale) Double-sided coating on the positive current collector; most of the positive active materials used in the production of positive pole pieces are lithium cobaltate or ternary materials or lithium iron phosphate, the conductive agent used is graphite, and the solvent is NMP (N-methylpyrrolidone ) and other additives to make a slurry, the slurry...

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Problems solved by technology

Since the positive electrode active material coating used is a single-layer coating layer of active material with a single particle size range and relatively coarse particles, the degree of adhesion between the positive electrode active material and the current collector is not uniform, and the adhesion is not firm, which causes the battery to fail. During use, the active material of the positive electrode falls off or the electrochemical reaction process of the electrodes is consistent, so that the capacity of the battery decreases rapidly, the cycle life is shortened sharply, and even the battery is scrapped due to a short circuit due to severe powder removal.

In addition, since the positive electrode active materials used in the production of existing lithium-ion batteries are all micron-sized lithium cobalt oxides or ternary materials or lithium iron phosphate, the slurry can only be used in the production of existing lithium-ion battery positive electrodes. The so-called single-layer "coating" process, due to the coarse particle size, in addition to the defect of weak adhesion to the positive electrode current collector, the porosity of the electrode active material coating is also large and uneven, which is not conducive to the wetting of the electrolyte , adsorption, electrode capacity and battery capacity are limited. At the same time, lithium-ion batteries produced with micron-sized lithium cobalt oxide or ternary materials or lithium iron phosphate positive electrode active materials have low specific capacity, poor high-current discharge effect and Short cycle life and other shortcomings make it difficult to meet the requirements of high-power electric tools and electric vehicle power for high-current and fast charging and discharging of power-type lithium-ion batteries

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