CN115241416A - A kind of solid-state battery composite negative electrode and preparation method thereof - Google Patents

Abstract

The invention provides a solid-state battery composite negative electrode and a preparation method thereof, wherein the solid-state battery composite negative electrode is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, the first negative electrode layer is composed of a carbon-based active material, a conductive agent, a binder and a solid electrolyte, the second negative electrode layer is composed of a silicon-based active material, a conductive agent, a binder and a solid electrolyte, and the third negative electrode layer is composed of a carbon-based active material, a conductive agent, a binder and a solid electrolyte. According to the solid-state battery composite cathode, the silicon and the solid electrolyte layer and the silicon and the current collector are separated by the carbon material, so that the cycle stability of the solid-state battery is improved; meanwhile, a concentration gradient is arranged in the negative electrode, so that the negative electrode is ensured to have a good electron passage and an ion passage.

Description

A kind of solid-state battery composite negative electrode and preparation method thereof

technical field

The invention belongs to the technical field of lithium ion batteries, and in particular relates to a solid-state battery composite negative electrode and a preparation method thereof.

Background technique

At present, most of the safety problems of electric vehicles are caused by power batteries. While the industry continues to pursue high energy density of batteries to improve the driving range of the vehicle, safety problems have become more prominent. Solid-state batteries that replace organic electrolytes with solid-state electrolytes are expected to become safe alternatives to lithium-ion batteries currently on the market. To realize high-energy-density sulfide all-solid-state batteries, electrode active materials play a decisive role. Among them, silicon anode has been recognized as one of the next-generation advanced anode materials due to its ultra-high theoretical specific capacity, suitable lithium intercalation potential, huge natural reserves, extensive access and low cost.

The prior art discloses an all-solid-state battery with a silicon negative electrode and a sulfide solid electrolyte, which includes a battery core, the battery core includes a negative electrode, a solid electrolyte layer and a positive electrode, and the negative electrode includes a current collector and is laminated and fixed on the side of the current collector. The lithium intercalation layer is formed by pressing the mixed powder including the sulfide electrolyte powder and the silicon-containing negative electrode powder. The silicon content in the mixed powder is 40-53wt%, and the particle size of the sulfide electrolyte powder The particle size of the silicon-containing negative electrode powder is 10-100 nm, and the porosity of the lithium intercalation layer is 15-23%. The adaptive adjustment reduces the possibility of cracking and pulverization of the lithium intercalation layer, and ensures the stable electrical contact between the intercalation and desulfurization layer, the current collector and the solid electrolyte layer respectively, thereby slowing down the capacity decay of the high-silicon anode solid-state battery and improving the high-silicon anode solid-state battery. cycle performance.

The prior art also discloses a negative electrode for a sulfide all-solid-state battery, comprising negative electrode material particles, characterized in that the negative electrode material particles have: a lamination part, and the lamination part has a plurality of Si-based material layers and a plurality of voids layers, the Si-based material layers containing at least one Si-based material selected from the group consisting of Si and Si alloys, the Si-based material layers and the void layers being alternately stacked; and a cover film, the cover film The surface of the laminated part is covered so as to cover at least the void layer.

The prior art also discloses a method for preparing a lithium-silicon alloy composite negative electrode material covered by a sulfide electrolyte. In this method, silicon powder and lithium metal particles are mixed with high-energy nodular graphite in an argon atmosphere, and then the lithium-silicon alloy obtained by ball milling is mixed with sulfided The electrolyte raw materials are mixed and reacted in a solvent, and finally the composite electrode obtained after the mixture is decompressed, distilled and sintered is sputtered onto the solid sulfide electrolyte by using a magnetron sputtering equipment. The electrolyte-coated lithium-silicon alloy composite anode can effectively improve the interface problem of ion transport between the two-phase interface of the electrolyte and the electrode material, improve the transport efficiency of lithium ions, and reduce the resistance of ion transport, thereby improving the charge-discharge specific capacity of the composite electrode material. , Coulombic efficiency and cycle performance.

However, in order to realize the large-scale application of Si anodes, the following disadvantages still need to be overcome: the huge volume expansion of Si during lithium intercalation, the huge collision causes the Si particles to be easily broken during the charge-discharge cycle and then fall off from the current collector, and the expansion As a result, the mechanical contact of the interface is deteriorated and the battery is short-circuited.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a solid-state battery composite negative electrode and a preparation method of a solid-state battery composite negative electrode in view of the above-mentioned deficiencies of the prior art, so as to solve the problem of improving the cycle stability of the solid-state battery and avoiding the existing Si The Si particles in the negative electrode are easily broken and then fall off from the current collector, and the mechanical contact of the interface deteriorates during expansion, which can easily lead to the problem of short circuit of the battery.

The purpose of this invention is to realize through the following technical solutions:

A composite negative electrode for a solid-state battery, characterized in that it is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of a carbon-based active material, a conductive agent, a binder, and a solid-state battery. The second negative electrode layer is composed of silicon-based active material, conductive agent, binder and solid electrolyte; the third negative electrode layer is composed of carbon-based active material, conductive agent, binder and solid electrolyte.

Further, in the first and third negative electrode layers, the carbon-based active material is one of natural graphite, artificial graphite, and hard carbon.

Further, the silicon-based active material in the second negative electrode layer is one of silicon element and silicon oxide.

Further, the conductive agent includes any one or a combination of at least two of acetylene black, ketjen black, fumed carbon fiber, carbon nanotube, carbon nanofiber, and graphene.

Further, the binder includes styrene butadiene rubber, carboxymethyl cellulose, acrylonitrile butadiene rubber, butadiene rubber, butyl rubber, polyvinylidene fluoride, polytetrafluoroethylene or polyimide any one or a combination of at least two.

Further, the solid electrolyte is a sulfide electrolyte or a polymer electrolyte.

Further, in the first negative electrode layer, the mass ratio of the active material to the solid electrolyte is between 70:30 and 90:10; in the second negative electrode layer, the mass ratio of the active material to the solid electrolyte is 60:40 Between ~80:10; in the third negative electrode layer, the mass ratio of the active material to the solid electrolyte is between 50:50 and 70:30.

Further, in the first negative electrode layer, the conductive agent accounts for 0.1%-1%; in the second negative electrode layer, the conductive agent accounts for 1%-4%; in the third negative electrode layer, the conductive agent accounts for than 0.5%-2%.

Further, the thickness of the first negative electrode layer is 5-15 μm; the thickness of the second negative electrode layer is 20-60 μm; the thickness of the third negative electrode layer is 5-30 μm.

The preparation method of the solid-state battery composite negative electrode comprises the following steps:

S1: prepare the required slurries for the first negative electrode layer, the second negative electrode layer, and the third negative electrode layer respectively according to the composition;

S2: the second negative electrode layer and the third negative electrode layer are coated on the current collector by extrusion or transfer;

S3: The first negative electrode layer is coated on the second negative electrode layer by gravure or screen printing.

Separate silicon and carbon to form silicon layer, carbon layer 1 and carbon layer 2 respectively; separate silicon and electrolyte layer by the first negative electrode layer to provide buffer; separate silicon and current collector by the third negative electrode layer; The degree of transfer difficulty can adjust the content of conductive agent and electrolyte; it can increase the silicon content and improve the cycle stability.

Compared with the prior art, the beneficial effects of the present invention are:

The invention provides a solid-state battery composite negative electrode, the composite negative electrode is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of carbon-based active material, conductive agent, binder, solid state Electrolyte composition; the second negative electrode layer is composed of silicon-based active material, conductive agent, binder, and solid electrolyte; the third negative electrode layer is composed of carbon-based active material, conductive agent, binder, and solid electrolyte; It is separated from the solid electrolyte layer, silicon and current collector to improve the cycle stability of the solid-state battery; at the same time, a concentration gradient is set inside the negative electrode to ensure that the negative electrode has a good electron path and ion path.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

Figure 1 Schematic diagram of graphite, silicon, and silicon-oxygen in the composite negative electrode of solid-state battery.

Detailed ways

Below in conjunction with embodiment, the present invention is further described:

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, the drawings only show some but not all structures related to the present invention.

It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further definition and explanation in subsequent figures. Meanwhile, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

The solid-state battery composite negative electrode of the present invention is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of a carbon-based active material, a conductive agent, a binder and a solid electrolyte; The second negative electrode layer is composed of a silicon-based active material, a conductive agent, a binder and a solid electrolyte; the third negative electrode layer is composed of a carbon-based active material, a conductive agent, a binder and a solid electrolyte.

Among them, the components of the first negative electrode layer:

In the first negative electrode layer, the mass ratio of the active material to the solid electrolyte is between 70:30 and 90:10;

The conductive agent accounts for 0.1%-1%;

The thickness of the first negative electrode layer is 5-15 μm.

Components of the second negative electrode layer:

In the second negative electrode layer, the mass ratio of the active material to the solid electrolyte is between 60:40 and 80:20;

The conductive agent accounts for 1%-4%;

The thickness of the second negative electrode layer is 20-60 μm.

Components of the third negative electrode layer:

In the third negative electrode layer, the mass ratio of the active material to the solid electrolyte is between 50:50 and 70:30;

The conductive agent accounts for 0.5%-2%;

The thickness of the third negative electrode layer is 5-30 μm.

Specifically, in the first and third negative electrode layers, the carbon-based active material is one of natural graphite, artificial graphite, and hard carbon; the silicon-based active material in the second negative electrode layer is simple silicon, silicon oxide a kind of.

The conductive agent includes any one or a combination of at least two of acetylene black, Ketjen black, fumed carbon fiber, carbon nanotube, carbon nanofiber, and graphene.

The binder includes any of styrene butadiene rubber, carboxymethyl cellulose, acrylonitrile butadiene rubber, butadiene rubber, butyl rubber, polyvinylidene fluoride, polytetrafluoroethylene or polyimide. one or a combination of at least two

The solid electrolyte is a sulfide electrolyte or a polymer electrolyte.

The preparation method of the solid-state battery composite negative electrode of the present invention is different from the silicon carbon negative electrode, in which silicon and carbon are separated to form a silicon layer, a carbon layer 1 and a carbon layer 2 respectively. The silicon and the electrolyte layer are separated by the first negative electrode layer to provide a buffer; the silicon and the current collector are separated by the third negative electrode layer; the content of conductive agent and electrolyte can be adjusted in different layers according to the difficulty of ion transport; the silicon content can be increased and the cycle stability can be improved .

Example 1

A solid-state battery composite negative electrode is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of natural graphite, acetylene black, styrene-butadiene rubber and sulfide electrolyte; the The second negative electrode layer is composed of silicon, acetylene black, styrene-butadiene rubber and sulfide electrolyte; the third negative electrode layer is composed of natural graphite, acetylene black, styrene-butadiene rubber and sulfide electrolyte.

Among them, in the first electrode layer, the mass ratio of natural graphite and sulfide electrolyte is 90:10, the conductive agent accounts for 0.3%, and the thickness of the first negative electrode layer is 10 μm. In the second negative electrode layer, the mass ratio of silicon to sulfide electrolyte is 70:30, the conductive agent accounts for 2%, and the thickness of the second negative electrode layer is 30 μm. In the third negative electrode layer, the mass ratio of natural graphite and sulfide electrolyte is 60:40, the conductive agent accounts for 1%, and the thickness of the third negative electrode layer is 20 μm.

Example 2

A solid-state battery composite negative electrode is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of artificial graphite, acetylene black, carboxymethyl cellulose and polymer electrolyte; The second negative electrode layer is composed of silicon, acetylene black, carboxymethyl cellulose and polymer electrolyte; the third negative electrode layer is composed of artificial graphite, acetylene black, carboxymethyl cellulose and polymer electrolyte.

Among them, in the first electrode layer, the mass ratio of artificial graphite and polymer electrolyte is 80:20, the conductive agent accounts for 0.5%, and the thickness of the first negative electrode layer is 10 μm. In the second negative electrode layer, the mass ratio of silicon to polymer electrolyte is 70:30, the conductive agent accounts for 2%, and the thickness of the second negative electrode layer is 40 μm. In the third negative electrode layer, the mass ratio of artificial graphite and polymer electrolyte is 60:40, the conductive agent accounts for 1%, and the thickness of the third negative electrode layer is 10 μm.

Example 3

A solid-state battery composite negative electrode, which is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of artificial graphite, Ketjen black, polyvinylidene fluoride and polymer electrolyte. ; the second negative electrode layer is composed of silicon, ketjen black, polyvinylidene fluoride and polymer electrolyte; the third negative electrode layer is composed of hard carbon, ketjen black, polyvinylidene fluoride and polymer electrolyte.

Among them, in the first electrode layer, the mass ratio of artificial graphite and polymer electrolyte is 70:30, the conductive agent accounts for 0.8%, and the thickness of the first negative electrode layer is 5 μm. In the second negative electrode layer, the mass ratio of silicon to polymer electrolyte is 60:40, the conductive agent accounts for 3%, and the thickness of the second negative electrode layer is 30 μm. In the third negative electrode layer, the mass ratio of hard carbon to polymer electrolyte is 60:40, the conductive agent accounts for 1%, and the thickness of the third negative electrode layer is 10 μm.

Example 4

A composite negative electrode for a solid-state battery is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of hard carbon, Ketjen black, polyvinylidene fluoride and polymer electrolyte ; the second negative electrode layer is composed of silicon, ketjen black, polyvinylidene fluoride and polymer electrolyte; the third negative electrode layer is composed of hard carbon, ketjen black, polyvinylidene fluoride and polymer electrolyte.

Among them, in the first electrode layer, the mass ratio of hard carbon and polymer electrolyte is 90:10, the conductive agent accounts for 0.3%, and the thickness of the first negative electrode layer is 10 μm. In the second negative electrode layer, the mass ratio of silicon to polymer electrolyte is 70:30, the conductive agent accounts for 2%, and the thickness of the second negative electrode layer is 40 μm. In the third negative electrode layer, the mass ratio of hard carbon to polymer electrolyte is 60:40, the conductive agent accounts for 1%, and the thickness of the third negative electrode layer is 10 μm.

Example 5

A solid-state battery composite negative electrode is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of natural graphite, acetylene black, styrene-butadiene rubber and sulfide electrolyte; the The second negative electrode layer is composed of silicon, acetylene black, styrene-butadiene rubber and sulfide electrolyte; the third negative electrode layer is composed of natural graphite, acetylene black, styrene-butadiene rubber and sulfide electrolyte.

Among them, in the first electrode layer, the mass ratio of natural graphite and sulfide electrolyte is 90:10, the conductive agent accounts for 0.1%, and the thickness of the first negative electrode layer is 5 μm. In the second negative electrode layer, the mass ratio of silicon to sulfide electrolyte is 80:10, the conductive agent accounts for 4%, and the thickness of the second negative electrode layer is 60 μm. In the third negative electrode layer, the mass ratio of natural graphite and sulfide electrolyte is 50:50, the conductive agent accounts for 0.5%, and the thickness of the third negative electrode layer is 5 μm.

Example 6

A solid-state battery composite negative electrode is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of natural graphite, acetylene black, styrene-butadiene rubber and sulfide electrolyte; the The second negative electrode layer is composed of silicon, acetylene black, styrene-butadiene rubber and sulfide electrolyte; the third negative electrode layer is composed of natural graphite, acetylene black, styrene-butadiene rubber and sulfide electrolyte.

Among them, in the first electrode layer, the mass ratio of natural graphite and sulfide electrolyte is 90:10, the conductive agent accounts for 1%, and the thickness of the first negative electrode layer is 15 μm. In the second negative electrode layer, the mass ratio of silicon to sulfide electrolyte is 70:30, the conductive agent accounts for 1%, and the thickness of the second negative electrode layer is 20 μm. In the third negative electrode layer, the mass ratio of natural graphite and sulfide electrolyte is 70:30, the conductive agent accounts for 2%, and the thickness of the third negative electrode layer is 30 μm.

Example 7

A solid-state battery composite negative electrode is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of artificial graphite, acetylene black, carboxymethyl cellulose and polymer electrolyte; The second negative electrode layer is composed of silicon, acetylene black, styrene-butadiene rubber and sulfide electrolyte; the third negative electrode layer is composed of artificial graphite, acetylene black, carboxymethyl cellulose and polymer electrolyte.

Among them, in the first electrode layer, the mass ratio of artificial graphite and polymer electrolyte is 80:20, the conductive agent accounts for 0.5%, and the thickness of the first negative electrode layer is 10 μm. In the second negative electrode layer, the mass ratio of silicon to sulfide electrolyte is 70:30, the conductive agent accounts for 2%, and the thickness of the second negative electrode layer is 30 μm. In the third negative electrode layer, the mass ratio of artificial graphite and polymer electrolyte is 60:40, the conductive agent accounts for 1%, and the thickness of the third negative electrode layer is 10 μm.

Example 8

A solid-state battery composite negative electrode is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of natural graphite, acetylene black, styrene-butadiene rubber and sulfide electrolyte; the The second negative electrode layer is composed of silicon, Ketjen black, polyvinylidene fluoride and polymer electrolyte; the third negative electrode layer is composed of natural graphite, acetylene black, styrene-butadiene rubber and sulfide electrolyte.

Among them, in the first electrode layer, the mass ratio of natural graphite and sulfide electrolyte is 90:10, the conductive agent accounts for 0.3%, and the thickness of the first negative electrode layer is 10 μm. In the second negative electrode layer, the mass ratio of silicon to polymer electrolyte is 60:40, the conductive agent accounts for 3%, and the thickness of the second negative electrode layer is 30 μm. In the third negative electrode layer, the mass ratio of natural graphite and sulfide electrolyte is 60:40, the conductive agent accounts for 1%, and the thickness of the third negative electrode layer is 10 μm.

Example 9

A method for preparing a composite negative electrode of a solid-state battery, comprising the following steps: respectively preparing the required slurry for a first negative electrode layer, a second negative electrode layer, and a third negative electrode layer according to the composition; Transfer coating on the current collector; the first negative electrode layer is coated on the second negative electrode layer by gravure or screen printing.

The preparation method separates silicon and carbon to form silicon layer, carbon layer 1 and carbon layer 2 respectively; separate silicon and electrolyte layer by a first negative electrode layer to provide buffer; separate silicon from current collector by a third negative electrode layer; different layers The content of conductive agent and electrolyte can be adjusted according to the difficulty of ion transport; the silicon content can be increased and the cycle stability can be improved.

Table 1

Loop (100 times) 0.1C/1C capacity Example 1 85% 80% Example 2 84% 80% Example 3 85% 83% Example 4 88% 85% Example 5 86% 83% Example 6 80% 76% Example 7 81% 78% Example 8 80% 75%

The invention provides a solid-state battery composite negative electrode, the composite negative electrode is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of carbon-based active material, conductive agent, binder, solid state Electrolyte composition; the second negative electrode layer is composed of silicon-based active material, conductive agent, binder, and solid electrolyte; the third negative electrode layer is composed of carbon-based active material, conductive agent, binder, and solid electrolyte; It is separated from the solid electrolyte layer, silicon and current collector to improve the cycle stability of solid state batteries. At the same time, a concentration gradient is set inside the negative electrode to ensure good electron and ion paths inside the negative electrode.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention. The scope is determined by the scope of the appended claims.

Claims (10)

1. A composite negative electrode of a solid-state battery, characterized in that: it is composed of a first negative electrode layer, a second negative electrode layer and a third negative electrode layer, wherein the first negative electrode layer is composed of carbon-based active material, conductive agent, binder and solid electrolyte; the second negative electrode layer is composed of silicon-based active material, conductive agent, binder and solid electrolyte; the third negative electrode layer is composed of carbon-based active material, conductive agent, binder and solid electrolyte. 2. A solid-state battery composite negative electrode according to claim 1, characterized in that: in the first and third negative electrode layers, the carbon-based active material is one of natural graphite, artificial graphite, and hard carbon. 3 . The solid-state battery composite negative electrode according to claim 1 , wherein the silicon-based active material in the second negative electrode layer is one of silicon element and silicon oxide. 4 . 4. a kind of solid-state battery composite negative electrode according to claim 1, is characterized in that: described conductive agent comprises any one in acetylene black, Ketjen black, gas phase carbon fiber, carbon nanotube, carbon nanofiber, graphene or a combination of at least two. 5. A solid-state battery composite negative electrode according to claim 1, wherein the binder comprises styrene-butadiene rubber, carboxymethyl cellulose, acrylonitrile butadiene rubber, butadiene rubber, butyl Any one or a combination of at least two of rubber, polyvinylidene fluoride, polytetrafluoroethylene or polyimide. 6 . The composite negative electrode of a solid-state battery according to claim 1 , wherein the solid-state electrolyte is a sulfide electrolyte or a polymer electrolyte. 7 . 7 . The composite negative electrode for a solid-state battery according to claim 1 , wherein in the first negative electrode layer, the mass ratio of the active material to the solid electrolyte is between 70:30 and 90:10; 7 . In the second negative electrode layer, the mass ratio of the active material to the solid electrolyte is between 60:40 and 80:10; in the third negative electrode layer, the mass ratio of the active material to the solid electrolyte is between 50:50 and 70:30. . 8 . The composite negative electrode of a solid-state battery according to claim 1 , wherein: in the first negative electrode layer, the conductive agent accounts for 0.1%-1%; in the second negative electrode layer, the conductive agent accounts for 0.1%-1%. 9 . 1%-4%; in the third negative electrode layer, the conductive agent accounts for 0.5%-2%. 9 . The solid-state battery composite negative electrode according to claim 1 , wherein the thickness of the first negative electrode layer is 5-15 μm; the thickness of the second negative electrode layer is 20-60 μm; the third negative electrode layer has a thickness of 20-60 μm; 10 . The thickness of the negative electrode layer is 5-30 μm. 10. The preparation method of a solid-state battery composite negative electrode according to claim 1, characterized in that, comprising the following steps: S1: prepare the required slurries for the first negative electrode layer, the second negative electrode layer, and the third negative electrode layer respectively according to the composition; S2: the second negative electrode layer and the third negative electrode layer are coated on the current collector by extrusion or transfer; S3: The first negative electrode layer is coated on the second negative electrode layer by gravure or screen printing.

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