A metal oxide film on the surfaces of electrode active material situated on a metal substrate

Abstract

A method for producing a metal oxide film on the surfaces of electrode active material situated on a metal substrate is disclosed. The method comprises: subjecting in a continuous manner the deposition surfaces of the electrode active material to alternately repeating surface reactions of two or more different precursors in a reaction space by exposing the deposition surfaces to one precursor at a time for a time period of 1 millisecond 20 seconds, to form a discontiguous metal oxide film on the surfaces of the electrode active material, wherein the discontiguous metal oxide film exhibits a thickness gradient varying from thicker to thinner in the direction from the outer surface towards the inner surface of the layer of electrode active material.

Description

[0001] A METAL OXIDE FILM ON THE SURFACES OF ELECTRODE ACTIVE MATERIAL SITUATED ON A METAL SUBSTRATE

[0002] FIELD OF INVENTION

[0003] The present disclosure relates to a method for producing a metal oxide film on the surfaces of electrode active material situated on a metal substrate . The present disclosure further relates to an obj ect comprising a discontiguous metal oxide film on the surfaces of electrode active material situated on a metal substrate . The present disclosure further relates to the use of the method as disclosed in the current specifi cation for increasing specific capacity and / or cycling stability of a battery . The present disclosure further relates to the use of the obj ect as disclosed in the current specification for increasing specific capacity and / or cycling stability of a battery .

[0004] BACKGROUND

[0005] A rechargeable battery, storage battery, or secondary cell as it may also be called, is a type of electrical battery which can be charged, discharged into a load, and recharged many times , as opposed to a dis posable battery or primary battery, which is supplied fully charged and discarded after use . A lithium-ion, or Li-ion battery, is a type of rechargeable battery which uses the reversible reduction of lithium ions to store energy . The negative electrode of a conventional lithium-ion cell i s typically graphite , a form of carbon . This negative electrode is sometimes called the anode as it acts an anode during discharge . The positive electrode is typically a metal oxide ; the positive electrode is sometimes called the cathode as it acts a cathode during discharge . The inventor has recogni zed the need of a battery having an increased capacity and lifetime . SUMMARY

[0006] A method for producing a metal oxide film on the surfaces of electrode active material situated on a metal substrate is disclosed . The electrode active material forms a layer on the substrate and the layer has an inner surface close to the metal substrate and an outer surface , which i s opposite to the inner surface . The method comprises :

[0007] - subj ecting in a continuous manner the deposition surfaces of the electrode active material to alternately repeating surface reactions of two or more different precursors in a reaction space by exposing the deposition surfaces to one precursor at a time for a time period of 1 millisecond - 20 seconds , to form a discontiguous metal oxide film on the surfaces of the electrode active material , wherein the discontiguous metal oxide film exhibits a thickness gradient varying from thicker to thinner in the direction from the outer surface towards the inner surface of the layer of electrode active material .

[0008] Further is disclosed an obj ect comprising a discontiguous metal oxide film on the surfaces of electrode active material situated on a metal substrate , wherein the electrode active material forms a layer on the substrate and wherein the layer has an inner surface close to the metal substrate and an outer surface , which is oppos ite to the inner surface , and wherein the discontiguous metal oxide film exhibits a thickness gradient varying from thicker to thinner in the direction from the outer surface towards the inner surface of the layer of electrode active material .

[0009] Further is disclosed the use of the method as disclosed in the current specification for increasing specific capacity and / or cycling stability of a battery .

[0010] The present disclosure further relates to the use of the obj ect as disclosed in the current specification for increasing specific capacity and / or cycling stability of a battery .

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings , which are included to provide a further understanding of the method and the substrate and constitute a part of this specification, illustrate embodiments and together with the description help to explain the principles of the above . In the drawings :

[0013] Fig . 1 is a schematical illustration of an obj ect comprising a discontiguous metal oxide film on the surfaces of electrode active material situated on a metal substrate according to one embodiment ; and

[0014] Fig . 2a and 2b discloses the test results of example 1 .

[0015] DETAILED DESCRIPTION

[0016] A method for producing a metal oxide film on the surfaces of electrode active material situated on a metal substrate is disclosed . The electrode active material forms a layer on the substrate and the layer has an inner surface close to the metal substrate and an outer surface , which i s opposite to the inner surface . The method comprises :

[0017] - subj ecting in a continuous manner the deposition surfaces of the electrode active material to alternately repeating surface reactions of two or more different precursors in a reaction space by exposing the deposition surfaces to one precursor at a time for a time period of 1 millisecond - 20 seconds , to form a discontiguous metal oxide film on the surfaces of the electrode active material , wherein the discontiguous metal oxide film exhibits a thickness gradient varying from thicker to thinner in the direction from the outer surface towards the inner surface of the layer of electrode active material .

[0018] Further is disclosed an obj ect comprising a discontiguous metal oxide film on the surfaces of electrode active material situated on a metal substrate , wherein the electrode active material forms a layer on the substrate and wherein the layer has an inner surface close to the metal substrate and an outer surface , which is oppos ite to the inner surface , and wherein the discontiguous metal oxide film exhibits a thickness gradient varying from thicker to thinner in the direction from the outer surface towards the inner surface of the layer of electrode active material .

[0019] In one embodiment , the obj ect is a battery, such as a lithium-ion battery . In one embodiment , the metal oxide film is an aluminum oxide film .

[0020] Further is disclosed the use of the method as disclosed in the current specification for increasing specific capacity and / or cycling stability of a battery .

[0021] The present disclosure further relates to the use of the obj ect as disclosed in the current specifi cation for increasing specific capacity and / or cycling stability of a battery .

[0022] By the term "electrode active material" is to be understood in this specification, unless otherwise stated, to refer to cathode materials , anode materials , anode foils , and / or electrochemically active materials , including solvents , additives , and electrolyte salts that may contribute to the electrochemical processes necessary for energy storage .

[0023] The electrode active material used may be in the form of a powder or granules . In one embodiment , the electrode active material is a cathode active material . The cathode active material may be a cathode foil .

[0024] The inventor surprisingly found out that it is possible to form a discontiguous metal oxide fi lm that exhibits a thickness gradient varying from thicker to thinner in the direction from the outer surface towards the inner surface of the layer of electrode active material . By the term "thickness gradient" is to be understood in this specification, unless otherwise stated, that the film does not have a uniform thickness throughout the metal oxide film, but the thickness of the formed fi lm varies . This may also be referred to as the metal oxide film being "discontiguous" or "non-continuous" . In one embodiment , the thickness gradient varies from 0 . 01 to 5 nm, or 0 . 1 to 5 nm, or from 0 . 3 to 4 . 5 nm, or from 0 . 5 to 3 nm, or from 0 . 7 to 3 . 5 nm, or from 1 . 0 to 3 . 0 nm, in the direction from the inner surface towards the outer surface of the layer of the electrode active material . Thus , the metal oxide film is thicker when moving closer to the outer surface of the layer of electrode active material and thinner when moving closer or towards to the inner surface of the layer of electrode active material . Thus the metal oxide film formed closer to the inner surface of the layer of electrode active material is thinner in thickness than the metal oxide film formed closer to the outer surface of the layer of electrode active material .

[0025] The inventor surprisingly found out that a discontiguous metal oxide film may be formed by regulating the time that the deposition surface is exposed to each of the precursors .

[0026] In this specification, unless otherwise stated, the term "the surface" , " surfaces of the electrode active material" , or "deposition surface" , is used to addres s the surface of the substrate or the surface of the already formed film or deposit on the substrate . Therefore , the terms "surface" , "surfaces of the electrode active material" , and "deposition surface" include the surfaces of the electrode active material which have not yet been exposed to any precursors and the surfaces which have been exposed to one or more precursors . The "deposition surface" thus changes during the deposition process when chemicals get chemisorbed onto the surface .

[0027] The method comprises subj ecting in a continuous manner the deposition surfaces of the electrode active material to alternately repeating surface reactions of two or more different precursors in a reaction space . By the term "in a continuous manner" is to be understood in this specification, unless otherwise stated, as referring to a process , where the substrate with the electrode active material is continuously exposed to one precursor after another, one precursor at a time , with purging periods between .

[0028] In one embodiment , exposing the deposition surfaces to one precursor at a time is carried out for a time period of 1 millisecond - 16 seconds , or 10 milliseconds - 5 seconds , or 30 mill iseconds - 1 . 5 seconds , or 50 mi lli seconds to 1 second, or 100 mil liseconds to 0 . 5 seconds . In one embodiment , expos ing the deposition surfaces to one precursor at a time is carried out for a time period of 1 - 209 milliseconds , or 210 - 999 milliseconds , or 1 - 16 seconds . After the specified time period, the deposition surfaces are exposed to the following precursor . The inventor surprisingly found out that by using the rather short period of time for exposing each of the used precursors to the deposition surface , one is able to grow a discontiguous metal oxide film . As the surface of the electrode active material is a porous network, the precursor needs time to permeate and react throughout that network . Us ing a shorter period of time may thus have the added utility of the less precursor being able to penetrate the layer of electrode active material from the outer surface to the inner surface . Thus , by subj ecting the deposition surface to the precursor for a shorter period of time , one may control the eff iciency of the permeation, and thus the thickness of the formed metal oxide film . Using a In one embodiment, the deposition surfaces are exposed to one precursor at a time in an amount of 0.001 - 16 mg, or 0.01 - 10 mg, or 0.05 - 7.5 mg, or 0.1 - 5 mg, or 1 - 3 mg, of the precursor per each time period. In one embodiment, the deposition surfaces are exposed to one precursor at a time in an amount of 0.001 - 16 mg, or 0.01 - 10 mg, or 0.05 - 7.5 mg, or 0.1 - 5 mg, or 1 - 3 mg, of the precursor per each time period.

[0029] In one embodiment, exposing the deposition surfaces in a continuous manner to one precursor at a time is carried out by moving the electrode active material situated on the metal substrate in the reaction chamber at a speed of 1 - 1700 mm / s, or 5 - 1000 mm / s, or 10 - 700 mm / s, or 25 - 400 mm / s, or 50 - 350 mm / s, or 100 - 250 mm / s.

[0030] In one embodiment, each precursor is fed into the reaction space through at least one nozzle of a size of 100 - 2200 mm long, or 200 - 800 mm long, or 300 - 400 mm long. In one embodiment, each precursor is fed into the reaction space through at least one nozzle of a size of 100 - 399 mm long, or 400 - 799 mm long, or 800 - 2200 mm .

[0031] The metal oxide film may be produced on the surfaces of the electrode active material in a reaction space by continuous atomic layer deposition (ALD) type process. The ALD-type process is a method for depositing uniform and conformal deposits or layers over substrates of various shapes, even over complex three dimensional structures. In the ALD-type process, the substrate is alternately exposed to at least two different precursors (chemicals) , usually one precursor at a time, to form on a deposit or a film by alternately repeating essentially self-limiting surface reactions between the surface of the substrate (on the later stages, naturally, the surface of the already formed layer on the substrate) and the precursors. As a result, the deposited material is "grown" on the substrate molecule layer by molecule layer .

[0032] The distinctive feature of the ALD-type process is that the surface to be deposited is exposed to two or more different precursors in an alternate manner with usually a purging period in between the precursor pulses . During a purging period the deposition surface is exposed to a flow of gas which does not react with the precursors used in the process . This gas , often called the carrier gas is therefore inert towards the precursors used in the process and removes e . g . surplus precursor and by-products resulting from the chemisorption reactions of the previous precursor pulse . This purging can be arranged by different means . The basic requirement of the ALD-type process is that the deposition surface is purged between the introduction of a precursor for a metal and a precursor for a non-metal . The purging period ensures that the gas phase growth is limited and only surfaces exposed to the precursor gas participate in the growth . The alternate or sequential exposure of the deposition surface to different precursors can be carried out in different manners . In a batch type process at least one substrate is placed in a reaction space , into which precursor and purge gases are being introduced in a predetermined cycle . Spatial atomic layer deposition is an ALD-type process based on the spatial separation of precursor gases or vapors . The di fferent precursor gases or vapors can be confined in specific process areas or zones while the substrate passes by . In the continuous ALD-type process constant gas flow zones separated in space and a moving substrate are used in order to obtain the time sequential exposure . By moving the substrate through stationary zones , providing precursor exposure and purging areas , in the reaction space , a continuous coating process is achieved enabling roll-to-roll coating of a substrate . In continuous ALD-type process the cycle time depends on the speed of movement of the substrate between the gas flow zones .

[0033] Other names besides atomic layer deposition (ALD) have also been employed for these types of processes , where the alternate introduction of or exposure to two or more di fferent precursors lead to the growth of the layer, often through essentially self-limiting surface reactions . These other names or process variants include atomic layer epitaxy (ALE) , atomic layer chemical vapour deposition (ALCVD) , and corresponding plasma enhanced variants . Unless otherwise stated, also these processes will be collectively addressed as ALD-type processes in this specification .

[0034] In one embodiment , the continuous ALD-type process comprises spatial ALD-type process and / or roll-to- roll coating .

[0035] In one embodiment , an obj ect compri sing a discontiguous metal oxide film ( 1 ) on the surfaces of electrode active material situated on a metal substrate ( 3 ) obtainable by the method as disclosed in the current specification .

[0036] The method has the added uti lity of one being able to produce a discontiguous metal oxide film on the surfaces of an electrode active material . The being able to produce a discontiguous metal oxide film has the added utility of improving the specific capacity and / or the cycling stability of a battery when used therein .

[0037] The method has the added utility of being a fast method for producing a metal oxide film with the above properties .

[0038] EXAMPLES

[0039] Reference will now be made in detail to the described embodiments , examples of which are illustrated in the accompanying drawings .

[0040] The description below discloses some embodiments in such a detail that a person skilled in the art is able to uti li ze the method based on the di sclosure . Not all steps of the embodiments are discussed in detail , as some of the steps will be obvious for the person skilled in the art based on this specification .

[0041] In Fig . 1 is illustrated the production in a reaction space of an obj ect comprising a discontiguous metal oxide fi lm 1 on the surfaces of electrode active material situated on a metal substrate 3 , when precursors are exposed on the deposition surface from ALD coating heads 4 . The electrode active material forms a layer 2 on the substrate and the layer has an inner surface 2a close to the metal substrate and an outer surface 2b, which is opposite to the inner surface . The discontiguous metal oxide film 1 exhibits a thickness gradient varying from thicker to thinner in the direction from the outer surface 2b towards the inner surface 2a of the layer of electrode active material 2 .

[0042] EXAMPLE 1 - Method for producing a discontiguous metal oxide film on the surfaces of electrode active material situated on a metal substrate

[0043] In this example a discontiguous aluminum oxide (AI2O3 ) film was produced on NCM811 cathode foils . Ni- rich LiNio .8Coo .1Mno .1O2 (NCM811 ) is a cathode material normally used for lithium-ion batteries (LIBs ) .

[0044] The following materials and parameters were used to produce the aluminum oxide films :

[0045] Sample 1 :

[0046] Precursors used : trimethylaluminium ( TMA) and H2O Time period for exposing to each precursor : 160 mil liseconds

[0047] Temperature of the reactor chamber : 125 °C

[0048] Sample 2 :

[0049] Precursors used : trimethylaluminium ( TMA) and H2O Time period for exposing to each precursor: 53 milliseconds

[0050] Temperature of the reactor chamber: 125 °C

[0051] Comparative sample:

[0052] A bare or uncoated NCM811 cathode foil was used as a comparative sample.

[0053] The prepared samples were subjected to a coin cell test (Half Cell) , which is a standard way to test materials for batteries. The coin cell test was carried out by long cycling conditions of 0.5 C and 3.0-4.4 V.

[0054] The results can be seen in Figs. 2a and 2b. Fig. 2a shows the specific capacity vs cycles and Fig. 2b. shows the capacity retention vs cycles. From the results one can see that both the specific capacity and capacity retention improved with samples 1 and 2 compared to the comparative sample.

[0055] It is obvious to a person skilled in the art that with the advancement of technology, the basic idea may be implemented in various ways. The embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.

[0056] The embodiments described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment. A method, an object, and uses as disclosed herein, may comprise at least one of the embodiments described hereinbefore. It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item refers to one or more of those items. The term "comprising" is used in this specification to mean including the feature (s) or act(s) followed thereafter, without excluding the presence of one or more additional features or acts.

Claims

CLAIMS1. A method for producing a metal oxide film (1) on the surfaces of electrode active material situated on a metal substrate (3) , wherein the electrode active material forms a layer (2) on the substrate and wherein the layer has an inner surface (2a) close to the metal substrate and an outer surface (2b) , which is opposite to the inner surface, and wherein the method comprises :- subjecting in a continuous manner the deposition surfaces of the electrode active material to alternately repeating surface reactions of two or more different precursors in a reaction space by exposing the deposition surfaces to one precursor at a time for a time period of 1 millisecond - 20 seconds, to form a discontiguous metal oxide film on the surfaces of the electrode active material, wherein the discontiguous metal oxide film exhibits a thickness gradient varying from thicker to thinner in the direction from the outer surface towards the inner surface of the layer of electrode active material.

2. The method of any one of the preceding claims, wherein the thickness gradient varies from 0.01 to 5 nm, or 0.1 to 5 nm, or from 0.3 to 4.5 nm, or from 0.5 to 3 nm, or from 0.7 to 3.5 nm, or from 1.0 to 3.0 nm, in the direction from the inner surface (2a) towards the outer surface (2b) of the layer of the electrode active material (2) .

3. The method of any one of the preceding claims, wherein exposing the deposition surfaces to one precursor at a time is carried out for a time period of 1 millisecond - 16 seconds, or 10 milliseconds - 5 seconds, or 30 milliseconds - 1.5 seconds, or 50 milliseconds to 1 second, or 100 milliseconds to 0.5 seconds.

4. The method of any one of the preceding claims, wherein the deposition surfaces are exposed to one precursor at a time in an amount of 0.001 - 16 mg,or 0.01 - 10 mg, or 0.05 - 7.5 mg, or 0.1 - 5 mg, or 1 - 3 mg, of the precursor per each time period.

5. The method of any one of the preceding claims, wherein exposing the deposition surfaces in a continuous manner to one precursor at a time is carried out by moving the electrode active material situated on the metal substrate in the reaction chamber at a speed of 1 - 1700 mm / s, or 5 - 1000 mm / s, or 10 - 700 mm / s, or 25 - 400 mm / s, or 50 - 350 mm / s, or 100 - 250 mm / s.

6. The method of any one of the preceding claims, wherein each precursor is fed into the reaction space through at least one nozzle of a size of 100 - 2200 mm long, or 200 - 800 mm long, or 300 - 400 mm long .

7. The method of any one of the preceding claims, wherein the electrode active material (2) is in the form of a powder or granules.

8. The method of any one of the preceding claims, wherein the electrode active material (2) is cathode active material.

9. The method of claim 7, wherein the cathode active material (2) is a cathode foil.

10. The method of any one of the preceding claims, wherein the metal oxide film (1) is produced on the surfaces of the electrode active material (2) in a reaction space by continuous atomic layer deposition (ALD) type process.

11. The method of claim 9, wherein the continuous ALD-type process comprises spatial ALD-type process and / or roll-to-roll coating.

12. An object comprising a discontiguous metal oxide film (1) on the surfaces of electrode active material situated on a metal substrate (3) , wherein the electrode active material forms a layer (2) on the substrate and wherein the layer has an inner surface (2a) close to the metal substrate and an outer surface (2b) , which is opposite to the inner surface, and wherein thediscontiguous metal oxide film exhibits a thickness gradient varying from thicker to thinner in the direction from the outer surface towards the inner surface of the layer of electrode active material.

13. The object of claim 12, wherein the thickness gradient varies from 0.01 to 5 nm, or 0.1 to 5 nm, or from 0.3 to 4.5 nm, or from 0.5 to 3 nm, or from 0.7 to 3.5 nm, or from 1.0 to 3.0 nm, in the direction from the inner surface (2a) towards the outer surface (2b) of layer of electrode active material (2) .

14. The object of any one of claims 12 - 13, wherein the electrode active material (2) is in the form of a powder or granules.

15. The object of any one of claims 12 - 14, wherein the electrode active material (2) is cathode active material.

16. The object of claim 15, wherein the cathode active material (2) is a cathode foil.

17. The object of any one of claims 12 - 16, wherein the object is a battery, such as a lithium-ion battery .

18. Use of the method of any one of claims 1 - 11 for increasing specific capacity and / or cycling stability of a battery.

19. Use of the object of any one of claims 12 - 17 for increasing specific capacity and / or cycling stability of a battery.

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