RU2383086C1 - Method for manufacturing of lithium-ion accumulator electrodes - Google Patents

Abstract

FIELD: electricity. ^ SUBSTANCE: invention is related to the field of chemical sources of current, namely to production of lithium-ion accumulator electrodes. Result is achieved by the fact that in available method of electrode manufacturing, which consists in production of active mass, preparation of active mass layers, their connection to current shunt with the help of gluing, performance of further drying in process of active mass layers connection with current shunt, aqueous solution of gelatin is used, which contains N-methylpyrrolidone in the range of concentrations making 70-80 wt % of overall amount of liquid components. ^ EFFECT: manufacturing of electrodes having improved contact between active mass and current shunt. ^ 2 dwg, 2 ex

Description

The invention relates to the field of chemical current sources, in particular to the manufacture of electrodes of a lithium-ion battery.

A known method of manufacturing electrodes [R.J. Brod, K. Tagawa. Fundamentals of the production of lithium-ion batteries. Electrochemical power. 2004.V.4. No. 4], which consists in preparing a mixture consisting of an electrochemically active material, a binder, and a solvent, applying it to a down conductor, followed by drying. Polyvinylidene fluoride dissolved in N-methylpyrrolidone is used as a binder.

The disadvantage of this method is the introduction of a relatively large amount of ballast substance polyvinylidene fluoride ~ 10%, which reduces the capacity of the electrodes. Another disadvantage of this method is the interaction of polyvinylidene fluoride with a charged anode to form LiF, which leads to an increase in the impedance of the negative electrode.

A common feature of the analogue with the claimed method is the preparation of a mixture containing electrochemically active material, and the application of layers of the active mass on both sides of the collector using an adhesive solution to create contact between the active mass and the collector of the electrode.

A known method of manufacturing anodes (US patent No. 6432576, publ. 2002), which consists in preparing a mixture consisting of an electrochemically active material, a binder and a solvent, applying it to the collector, followed by drying. As an adhesive solution, an aqueous solution of styrene-butadiene latex, thickened with carboxymethyl cellulose, is used.

The disadvantage of this method is the large proportion of the uncovered surface of graphite (anode active material), since carboxymethyl cellulose forms a thread-like pattern on the surface, which leads to the formation of a poor-quality film of solid phase electrolyte (solid electrolyte interface), and, as a result, the losses of the first cycle increase and decreases battery life.

The disadvantage of this method is the relatively low adhesion of the active mass to the surface of the electrode down conductors due to the level of wettability of the adhesive based on water.

A common feature of the analogue with the claimed method is the preparation of a mixture containing electrochemically active material, and the application of layers of the active mass on both sides of the collector using an adhesive solution to create contact between the active mass and the collector of the electrode.

A known method of manufacturing electrodes [(S. Pejovnik and other. “Electrochemical binding and wiring in battery materials.” Journal of Power Sources, 184 (2008) p. 593-597)] (selected as a prototype), which consists in preparing a mixture consisting from an electrochemically active material, a binder and a solvent, and applying it to a down conductor, followed by drying. An adhesive solution is an aqueous gelatin solution. Gelatin, unlike carboxymethyl cellulose, forms a homogeneous continuous film on the surface of the particles of the active material.

The disadvantage of this method is the relatively low adhesion of the active mass to the surface of the electrode down conductors (both copper on the anode and aluminum on the cathode) due to the insufficient wettability of the adhesive based on water.

A common feature of the prototype with the claimed method is the preparation of a mixture containing electrochemically active material, and the application of layers of the active mass on both sides of the collector using an adhesive solution to create contact between the active mass and the collector of the electrode - an aqueous gelatin solution.

The technical result of the proposed method is the manufacture of electrodes having improved contact between the active mass and the collector.

This result is achieved by the fact that in the known method of manufacturing the electrode, which consists in manufacturing an active mass, obtaining active mass layers, connecting them to a down conductor by gluing, conducting subsequent drying when connecting the active mass layers to a down conductor, use an aqueous solution of gelatin containing N- methylpyrrolidone in the concentration range of 70-80 wt.% of the total amount of the liquid component of the solution (N-methylpyrrolidone and water).

When the concentration of N-methylpyrrolidone is less than 70%, the wettability of the down conductors deteriorates (Figure 1), and when the concentration of N-methylpyrrolidone is more than 80%, gelatin coagulates (precipitates). Wettability is determined as follows. A drop of an aqueous solution is applied to the surface of a collector located at a constant angle to a horizontal surface

N-methylpyrrolidone of various concentrations. Drops have the same volume. The area of the drop’s trail is measured at the moment when the “tail” of the drop begins to move. Wettability is calculated by the formula: C = 100- (b / l) × 100, where b, l are the width and length of the droplet, respectively. A comparison of the contact quality for anodes made with and without N-methylpyrrolidone is shown in FIG. 2. Quality control was performed by bending the electrode 360 ° С and vice versa.

Production is carried out in the following sequence. An aqueous solution of gelatin of the required concentration is prepared by adding a portion of gelatin to a deionized water at a temperature of 60-70 ° C. Then, with stirring, the gelatin is completely dissolved, the solution at a temperature of 2-5 ° C is maintained for a day. Then the required amount of N-methylpyrrolidone is added.

The electrochemically active material with the addition of an adhesive and a solvent is loaded into the mixer, after preparing a homogeneous paste, the solvent is removed by drying and the charge is passed through a sieve. Next, by rolling, sheets containing the active mass are obtained, and they are labeled on the collector with a prepared aqueous solution.

Distinctive features of the proposed method for the manufacture of electrodes of a lithium-ion battery from the prototype, which determine its compliance with the “novelty” criterion, are as follows: when gluing the active mass layers by gluing, the adhesive is used in the form of an aqueous gelatin solution containing N-methylpyrrolidone in the concentration range of 70-80% of the total amount of liquid components. When conducting a search in the literature did not find a method containing the above distinctive features, giving in combination with the known features of the above technical result. Therefore, according to the authors, the proposed method for the manufacture of electrodes of a lithium-ion battery meets the criterion of "inventive step".

Examples of the implementation of the proposed method

1. Anode

96% of graphite is mixed with a 4% aqueous solution of gelatin in a mixer for 2 hours with further removal of water by vacuum drying at 70-90 ° C with continuous stirring. The dried paste is wiped through a sieve with a decreasing mesh size to obtain a mixture. The mesh size of the last sieve is 100 microns. Next, sheets of active mass are obtained by rolling.

The copper tape is degreased with acetone, then heat treated at a temperature of 450 ° C for an hour in a hydrogen environment. A 27 wt.% Aqueous solution of gelatin is prepared by adding a portion of gelatin to deionized water at a temperature of 50-60 ° C, followed by stirring until it is completely dissolved; the solution at a temperature of 2-5 ° C is kept for a day. Then add 63 wt.% N-methylpyrrolidone of the total weight of the solution, stirring until it is completely dissolved. A layer of the solution is applied on both sides of the copper tape and the rolled metal is glued by rolling on both sides of the collector. Then produce drying at a temperature of 120-130 ° C.

2. The cathode

91% LiCoO _{2 is} mixed with 4% graphite KS-6, 2% carbon black Super P and 3% polyvinylidene fluoride with the addition of N-methylpyrrolidone. Next, the solvent is removed by vacuum drying at 60-75 ° C with continuous stirring. The dried paste is wiped through a sieve with a decreasing mesh size to obtain a mixture. The mesh size of the last sieve is 100 microns. Next, sheets of active mass are obtained by rolling.

The aluminum strip is degreased with acetone, then heat treated at a temperature of 270 ° C for an hour in a hydrogen environment. A 27 wt.% Aqueous solution of gelatin is prepared by adding a portion of gelatin to deionized water at a temperature of 50-60 ° C, followed by stirring until it is completely dissolved; the solution at a temperature of 2-5 ° C is kept for a day. Then add 63 wt.% N-methylpyrrolidone of the total weight of the solution, stirring until it is completely dissolved.

A layer of the solution is applied on both sides of the aluminum tape and the rolled metal is glued by rolling on both sides of the collector. Then produce drying at a temperature of 120-130 ° C.

Claims (1)

A method of manufacturing electrodes of a lithium-ion battery by manufacturing an active mass to obtain active mass layers and connecting them to a down conductor using gluing, subsequent drying and using an aqueous solution of gelatin as an adhesive solution, characterized in that N- is added to the aqueous gelatin solution methylpyrrolidone in the concentration range of 70-80% of the total amount of liquid components.

Images