DE102017218712A1 - ACTIVE MATERIAL FOR A NEGATIVE ELECTRODE, NEGATIVE ELECTRODE, ELECTROCHEMICAL ENERGY STORAGE, VEHICLE AND MANUFACTURING METHOD - Google Patents

Abstract

The invention relates to an active material for a negative electrode, in particular a lithium-ion cell, a negative electrode with such an active material, an electrochemical energy storage device with such a negative electrode, a vehicle with such an electrochemical energy store and a manufacturing method for such an active material. The active material contains porous carbon particles, particularly graphite particles, with pores of average pore size and silicon particles whose average particle size is smaller than the average pore size of the pores of the porous carbon particles and which are disposed inside the pores of the porous carbon particles. The active material has ion-conducting elements, preferably on an inorganic basis, which pass through the porous carbon particles and connect an outer region of the porous carbon particles in an ion-conducting manner with the silicon particles.

Description

The present invention relates to an active material for a negative electrode, in particular for a lithium-ion cell, a negative electrode having such an active material, an electrochemical energy store having such a negative electrode, a vehicle having such an electrochemical energy store, and a manufacturing method for such active material.

The high energy density and power output of current electrochemical energy storage, which are used for example in mobile communication devices or electrically driven vehicles, is achieved by the use of special materials for electrodes, separators and / or electrolytes of these energy storage. For example, graphite-based negative electrodes are known to which another material is added to increase the energy density.

The document US 8,778,541 B2 discloses a negative electrode having a metal-carbon composite containing a porous carbon material with cavities and a metal material for reversibly storing and emitting lithium ions. The metal material is disposed on a surface of the porous carbon material including the inner surface of the cavities of the porous carbon material.

It is an object of the invention to improve an operating characteristic of an electrochemical energy storage device.

This object is achieved by a negative electrode active material, a negative electrode, an electrochemical energy storage, and an active material production method according to the independent claims.

One aspect of the invention relates to an active material for a negative electrode, in particular a lithium ion cell, which has porous carbon particles, in particular graphite particles, with pores of average pore size and silicon particles whose average particle size is smaller than the average pore size of the porous carbon particles and the are arranged within the pores of the porous carbon particles. In particular, the active material has ion conducting elements, preferably on an inorganic basis, which penetrate the porous carbon particles and connect an outer region of the porous carbon particles to the silicon particles in an ion-conducting manner.

Among porous carbon particles in the sense of the invention, in particular so-called colloids, i. small solid bodies or particles, which consist of carbon, in particular graphite, or at least contain carbon, in particular graphite, and so-called. Kavitäten, i. Hollow spaces, which are also called pores, have. The porous carbon particles are preferably substantially spherical and may be part of aerosols, suspensions, powders and / or the like, especially dispersible.

For the purposes of the invention, silicon particles are in particular colloids which consist of silicon or at least contain silicon. The silicon particles are preferably substantially spherical and may be part of aerosols, suspensions, powders and / or the like, in particular dispersible. The silicon particles are preferably suitable for binding metal ions, in particular lithium ions, and / or for releasing metal ions bound thereto, in particular lithium ions.

In the context of the invention, ionic conducting elements, in particular lithium-ion conducting elements, are in particular colloids, which preferably consist of an inorganic, in particular ceramic, material or at least contain it. The ion-conducting elements preferably have a substantially elongated, in particular ellipsoidal, cylindrical or chain-like shape and may be part of aerosols, suspensions, powders and / or the like, in particular dispersible. In particular, the ion conducting elements are suitable for conducting metal ions, preferably lithium ions.

Under an outer region of the porous carbon particles in the sense of the invention, in particular the environment, i. to understand the volume surrounding the carbon particles. An ion-conducting connection between the outer region of the carbon particles and the silicon particles thus enables the transport of metal ions, in particular lithium ions, which are outside the carbon particles, into the interior of the carbon particles, in particular into the pores of the carbon particles, in particular to the silicon particles, and vice versa.

The invention is based in particular on the approach of providing an active material with a blend of carbon or graphite and silicon, in which the silicon is arranged in particle form within the carbon and is preferably completely enclosed by a carbon matrix. For this purpose, the carbon is preferably also in particle form, each carbon particle having a plurality of pores with an average pore size in which the silicon particles are arranged. To the transport of metal ions, in particular lithium ions, of a Outside of the carbon particles to allow or at least improve the silicon within the carbon particles, ion guide elements are provided, which enforce the carbon particles in a preferred manner, that is at least partially contained in a carbon structure, from which the carbon particles are formed. Preferably, the, in particular ceramic, lonenleitelemente thus form ion channels, through which the metal ions can be passed from an outer region of the carbon particles in the pores of the carbon particles, in particular through the pores, to the silicon particles.

In this case, the ion-conducting connection between the outer region of the carbon particles and the silicon particles is preferably not formed exclusively by the ion-conducting elements. In particular, metal ions may be taken up over an outer surface of the carbon particles and conducted through the carbon particles to the ion conducting elements, which then direct the metal ions through the pores of the carbon particles to the silicon particles. In this case, the ion guide elements are preferably designed to bridge the volume of the pores between the corresponding pore walls of the pores and the silicon particles arranged in the pores in an ion-conducting manner. Thus, in particular, the ion guide elements can form part of an ion-conducting connection between the outer region of the carbon particles and the silicon particles.

Preferably, the proportion of silicon in a carbon particle is substantially between 0.5 and 40%, in particular between 1 and 25%, preferably between 2 and 20%, in particular with respect to the weight of the carbon particles.

The active material according to the invention thus makes it possible to significantly increase the specific energy of an electrochemical energy store compared to energy stores that have negative electrodes with an active material that contains essentially exclusively graphite. The porosity of the carbon particles enables volume thrusts of the silicon particles in operation of an energy storage device having a negative electrode containing the active material of the present invention without damaging the active material or the negative electrode with the active material. The lonenleitelemente which enforce the carbon particles, the achievement of a particularly high and reliable conductivity of the carbon particles with respect to metal ions, in particular lithium ions is possible.

Overall, the invention makes it possible to increase the kinetics of ion conduction with respect to metal ions, in particular lithium ions. As a result, energy storage can be realized with a low cell internal resistance, an improved current load and / or an increased cycle stability, lifetime and / or reliability.

In a preferred embodiment of the invention, the active material further comprises a binder material and / or a Leitruß, wherein the porous carbon particles with the binder material and / or Leitruß form an active material matrix, and wherein an outer region of the active material matrix ion-conducting connected by the ion conducting with the silicon particles is. Preferably, the active material matrix, in particular together with the Leitruß, so penetrated by the lonenleitelementen that metal ions, in particular lithium ions, which are outside of the active material matrix, by lonenleitelemente and / or Leitruß into the pores of the carbon particles, in particular through the pores can be passed to the silicon particles. The ion conducting elements and / or the conductive carbon black preferably form ion channels for the transport of metal ions through the active material matrix. Thereby, the active material can be efficiently applied to a collector foil and an electrolyte and / or a separator in an energy storage efficiently, i. surface, while allowing a high conductivity with respect to the metal ions.

In a further preferred embodiment of the invention, the ion-conducting elements contain garnet, oxide, perovskites, sulfides and / or mixtures thereof. The ion-conducting elements are preferably formed from a garnet, oxide, perovskite, sulfide and / or a mixture thereof. As a result, the ion conducting elements can be integrated particularly well into the carbon particles and optionally into the active material matrix, at the same time enabling a high conductivity with respect to the metal ions.

In a further preferred embodiment of the invention, the porous carbon particles have an average size between 1 and 100 μm, preferably between 5 and 50 μm, in particular between 10 and 25 μm, with an average pore size between 100 and 5000 nm, preferably 250 and 2500 nm, especially 500 and 1000 nm, on. As a result, the carbon particles can easily be processed, in particular applied to a collector foil of a negative electrode and / or optionally incorporated into the active material matrix, preferably dispersed in the binder material. In addition, the carbon particles in the stated size have a large-area surface over which the metal ions can advantageously be transported or conducted into the interior of the carbon particles, in particular to the silicon particles.

In a further preferred embodiment of the invention, the silicon particles have an average particle size between 10 and 2500 nm, preferably between 50 and 1000 nm, in particular between 100 and 500 nm. As a result, the silicon particles can easily be processed, in particular introduced into the pores of the carbon particles, where sufficient space is available to compensate for volume increases of the silicon particles due to the uptake of metal ions in the silicon particles.

A second aspect of the invention relates to a negative electrode having a collector foil suitable for transporting electric charges and an active material applied to the collector foil according to the first aspect of the invention.

A third aspect of the invention relates to an electrochemical energy store, in particular a lithium-ion cell, with a positive electrode, a negative electrode according to the second aspect of the invention, a separator and / or an electrolyte.

A fourth aspect of the invention relates to a vehicle, in particular motor vehicle, with an electrochemical energy store according to the third aspect of the invention.

A fifth aspect of the invention relates to a process for producing an active material for a negative electrode, in particular for a lithium ion cell, wherein porous carbon particles, in particular graphite particles having pores of an average pore size, with silicon particles whose average particle size is smaller than that average pore size of the pores of the porous carbon particles, and lonenleitelementen be mixed in such a way that the silicon particles penetrate into the pores of the porous carbon particles and the ion conducting the porous carbon particles in such a way that an outer region of the porous carbon particles is ion-conductively connected to the silicon particles.

The features and advantages described in relation to the first aspect of the invention and its advantageous embodiment apply, at least where technically feasible, for the second, third, fourth and fifth aspects of the invention and its advantageous embodiment and vice versa.

• 1 ein Ausführungsbeispiel eines porösen Kohlenstoffpartikels, in dessen Poren Siliziumpartikel enthalten sind; und
• 2 ein Ausführungsbeispiel eines elektrochemischen Energiespeichers.

Further features, advantages and possible applications of the invention will become apparent from the following description in conjunction with the figures, in which the same reference numerals for the same or corresponding elements of the invention are used throughout. It shows at least partially schematically:

• 1 an embodiment of a porous carbon particle, in whose pores silicon particles are contained; and
• 2 an embodiment of an electrochemical energy storage.

1 shows an embodiment of a porous carbon particle 1 in whose pores 2 silicon particles 3 for receiving and releasing metal ions 4 , In particular, lithium ions are included. The carbon particle 1 is here with lonenleitelementen 5 for transporting the metal ions 4 interspersed. For clarity, only one of the pores shown is in each case 2 , one of the silicon particles shown 3 and one of the lonenleitelemente 5 provided with a reference numeral.

The carbon particle 1 has an average size, in particular a diameter, substantially between 1 and 100 μm, preferably between 5 and 50 μm, in particular between 10 and 25 μm. For the carbon particle 1 it is therefore a so-called colloidal particle which is or may be dispersed and / or is or may be part of an aerosol, a dispersion or a powder.

The silicon particles 3 have a smaller size, in particular diameter, than the carbon particle 1 , The average particle size of the silicon particles 3 is substantially substantially between 10 and 2500 nm, preferably between 50 and 1000 nm, in particular between 100 and 500 nm. These are the silicon particles 3 also colloidal particles, which are preferably or may be dispersed and / or are part of an aerosol, a dispersion or a powder or may be.

The carbon particle 1 , which is preferably formed as graphite particles, in particular has a carbon structure 1a on, in which the pores 2 , which are also referred to as cavities or cavities are formed. An average pore size of the pores 2 is substantially substantially between 100 and 5000 nm, preferably between 250 and 2500 nm; in particular between 500 and 1000 nm. Due to their smaller size, the silicon particles 3 suitable from the pores 2 of the carbon particle 2 to be included or included.

At the same time provide the pores 2 the silicon particles 3 enough space to damage the carbon structure 1a at volume spikes of silicon particles 3 , for example, by incorporation of metal ions 4 , to avoid.

Because of the silicon particles 3 not solid in the carbon particle 1 , especially in the Carbon structure 1a , arranged or positioned, but with play, ie movable, in the pores 2 are included, there is at least in part no or at least no pronounced contact between the carbon structure 1a and the silicon particles 3 , In particular, the direct ion conduction is of the carbon structure 1a to the silicon particles 3 through the pores 2 , especially within the volume of the pores 3 , impaired.

The ion-conducting elements 5, which preferably consist of an inorganic, in particular ceramic, material and the carbon particles 1 enforce, ie in the carbon structure 1a of the carbon particle 1 integrated or in the carbon structure 1a are included, are advantageously adapted to an outdoor area 6 of the carbon particle 1 ionically conductive with the silicon particles 3 connect to. The ion-conducting elements 5, which contain, for example, a garnet or a sulfite, thus preferably form at least part of a connection between the external environment of the carbon particle 1 and the silicon particles 3 inside the carbon particle 1 , especially in the pores 2 of the carbon particle 1 leading to the conduction of the metal ions 4 suitable is.

The ion-conducting elements 5 can depend on their arrangement within the carbon particle 1 a direct connection to the ion pipe between the outside area 6 and silicon particles 3 in the pores 2 of the carbon particle 1 for the transport of metal ions 4 manufacture, such as by one end of an ion guide 5 from the outer surface 1b of the carbon particle 1 protrudes and the opposite end of the ion guide 5 the silicon particle 3 contacted. The metal ions can 4 directly outside the carbon particle 1 taken up by the lonenleitelementen 5 and by the carbon structure 1a and the pores 2 to the silicon particles 3 be transported.

Alternatively or additionally, the lonenleitelemente 5 also an indirect connection between the outdoor area 6 and silicon particles 3 effect, such as by one end of a lonenleitelements 5 in the carbon particles 1 , in particular in the carbon structure 1a , protrudes and the opposite end of the lonenleitelements 5 the silicon particles 3 contacted. This will be metal ions 4 over the outer surface 1b of the carbon particle 1 taken and about the carbon structure 1a up to the ion guide elements 5 and from there through the pores 2 through to the silicon particles 3 transported.

The ion guide elements 5 can also have an end in the pores 2 protrude, instead of the silicon particles 3 to contact directly. The conductivity of the carbon particle 1 concerning the metal ions 4 up to the silicon particles 3 is also characterized by a carbon particle 1 increased without lonenleitelemente 5.

2 shows an embodiment of an electrochemical energy storage 10 , such as a lithium-ion cell, with a positive electrode 11 , a separator penetrated by an electrolyte 12 and a negative electrode 13 , where the negative electrode 13 an active material 14 with a variety of porous carbon particles 1 , In whose pores arranged silicon particles and which are interspersed by ionic guide elements (see 1 ), having. By using the negative electrode 13 with the active material 14 is a reduction of the internal resistance of the energy storage 10 allows, the energy storage 10 at the same time be more heavily loaded in terms of current flows in its interior.

LIST OF REFERENCE NUMBERS

1

Carbon particles

1a

Carbon structure

1b

outer surface

2

pore

3

silicon particles

4

metal ion

5

lonenleitelement

6

outdoors

10

energy storage

11

positive electrode

12

separator

13

negative electrode

14

active material

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 8778541 B2 [0003]

Claims (9)

Active material (14) for a negative electrode (13), in particular a lithium-ion cell, comprising porous carbon particles (1), in particular graphite particles, having pores (2) of an average pore size, Silicon particles (3) whose average particle size is smaller than the average pore size of the pores (3) of the porous carbon particles (1) and located inside the pores (2) of the porous carbon particles (1), and Ion guide elements (5) which pass through the porous carbon particles (1) and connect an outer region (6) of the porous carbon particles (1) in an ion-conducting manner to the silicon particles (3). Active material (14) after Claim 1 , further comprising a binder material and / or a Leitruß, wherein the porous carbon particles (1) with the binder material and / or Leitruß form an active material matrix, and wherein an outer region of the active material matrix through the ion conducting elements (5) with the silicon particles (3) ion conducting connected is. Active material (14) according to one of the preceding claims, wherein the ion-conducting elements (5) contain garnet, oxide, perovskites, sulphides and / or mixtures thereof. Active material (14) according to one of the preceding claims, wherein the porous carbon particles (1) have an average size between 1 and 100 μm, preferably between 5 and 50 μm, in particular between 10 and 25 μm, with an average pore size between 100 and 5000 nm, preferably 250 and 2500 nm, in particular 500 and 1000 nm. Active material (14) according to one of the preceding claims, wherein the silicon particles (3) have an average particle size between 10 and 2500 nm, preferably between 50 and 1000 nm, in particular between 100 and 500 nm. Negative electrode (13) having a collector foil suitable for transporting electric charges and an active material (14) applied to the collector foil according to one of the preceding claims. Electrochemical energy store (10), in particular lithium-ion cell, with a positive electrode (11), a negative electrode (13) according to Claim 6 , a separator (12) and / or an electrolyte. Vehicle, in particular motor vehicle, with an electrochemical energy store (10) according to Claim 7 , Method for producing an active material (14) for a negative electrode (13), in particular for a lithium-ion cell, wherein porous carbon particles (1), in particular graphite particles, having pores (2) of an average pore size, with silicon particles (3) whose average particle size is smaller than the average pore size of the pores (2) of the porous carbon particles (1), and ion conducting elements (5) are mixed in such a manner that the silicon particles (2) penetrate into the pores (2) of the porous carbon particles (1 ) and the ion guide elements (5) penetrate the porous carbon particles (1) in such a way that an outer region (6) of the porous carbon particles (1) is ionically conductively connected to the silicon particles (3).

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