Patent Application
20230223546
The present invention relates generally to methods for producing anodes for lithium batteries. More specifically, the invention relates to a method for producing an anode, wherein the anode active material is formed following a reaction between a lithiophilic material and a lithium material in molten form or following deposit of the lithium material on a lithiophilic surface. The current collector and/or at least one other layer of the anode may comprise a continuous 3D structure.
Lithium metal, with a theoretical0 specific energy of 3860 mAh/g, constitutes a good anode material for an energy storage system (ESS) or battery, in comparison for example to a material such as graphite which has a theoretical specific energy of 372 mAh/g.
A thin foil of Li metal is needed to increase the energy density of the battery and to decrease the production cost of the anode. However, Li has a low mechanical strength and electronic conductivity (less than 5 times and 3 times compared to copper and aluminium, respectively). Accordingly, a thin free-standing Li is difficult to produce and to handle. It is known in the art to use a thin layer of Li deposited on a substrate made of a conductive material. Typically, a substrate also called current collector that has good mechanical properties and a good electronic conductivity, is selected. Even a layer of Li with a thickness as low as 4 to 5 microns on the substrate constitutes a better solution than using a free-standing Li.
Methods for depositing a thin layer of Li on a metal substrate are known in the art. Such methods include for example the physical vapour deposition (PVD) technique. However, several drawbacks are associated to PVD such as the fact that the deposition rate is rather low, and the overall technique is quite expensive.
Also, it has been observed that when a layer of Li is deposited on the current collector, an interaction occurs between Li and the conductive material, which leads to the formation of cracks in the current collector. This is described herein below in more detail. The formation of cracks in the current collector becomes particularly prevalent when a more desirable thinner current collector is used, and also when other deposition techniques are conducted, which involve the use of lithium at elevated temperatures.
There is still a need for efficient and cost-effective methods for producing anodes for lithium batteries. In particular, there is a need for such methods which allow for other Li deposition techniques than PVD, and which do not lead to the current collector being damaged.
The inventors have designed and performed a method for producing an anode for lithium batteries. The method comprises: providing a current collector, forming a layer of protective material thereon, depositing a lithiophilic material on the layer of protective material, and depositing a molten lithium material on the layer of lithiophilic material. The lithiophilic material and the molten lithium material subsequently react to form the anode active material. The current collector and/or at least one other layer of the anode may comprise a continuous 3D structure on a surface thereof. The method may also comprise a plasma treatment which may lead to the formation of a lithiophilic surface. The protective material deposited on the current collector constitutes a barrier between the current collector and lithium in the anode active material, therefore formation of cracks in the current collector is avoided.
In embodiments of the invention, deposit of the lithiophilic material on the protective layer is followed by a plasma treatment leading to a plasma treated lithiophilic material, prior to depositing the molten lithium material.
In embodiments of the invention, the protective layer is subjected to a plasma treatment leading to the formation of a lithiophilic surface, on which the molten lithium material is deposited.
The plasma treatment may be a thermal atmospheric pressure plasma or any other suitable plasma treatments.
In embodiments of the invention, the current collector is provided with a continuous 3D structure formed on its surface. In addition, at least one other layer of the anode including the protective layer, the lithiophilic surface, the layer of the anode active material, and the layer of surface treatment agent may comprise a continuous 3D structure. The continuous 3D structure may be formed by electrochemical or chemical deposition of a conductive material on the surface.
Alternatively, regarding the current collector for example, the continuous 3D structure may be formed by providing some roughness at a surface thereof using a technique which may comprise a mechanical and/or a laser treatment, electrochemical oxidation, chemical etching, or any other suitable techniques.
In embodiments of the invention, the lithium material in molten form comprises lithium or an alloy thereof.
In embodiments of the invention, there is provided an anode that comprises a current collector, a layer of protective material deposited on the current collector, and a layer of anode active material which is formed following a reaction between a lithiophilic material and a lithium material in molten form or which is formed following deposit of the lithium material on a lithiophilic surface. In embodiments of the invention, the anode is single-sided, or the anode is double-sided. In embodiments of the invention, the current collector has a thickness between about 4 to about 5 μm.
In embodiments of the invention, there is provided an apparatus adapted for conducting the method described herein to produce the anode described herein.
In embodiments of the invention, the lithium battery is a lithium-ion battery or an all-solid-state battery.
The invention thus provides the following in accordance with aspects thereof:
Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
In the appended drawings:
Before the present invention is further described, it is to be understood that the invention is not limited to the particular embodiments described below, as variations of these embodiments may be made and still fall within the scope of the appended claims. It is also to be understood that the terminology employed is for the purpose of describing particular embodiments; and is not intended to be limiting. Instead, the scope of the present invention will be established by the appended claims.
In order to provide a clear and consistent understanding of the terms used in the present specification, a number of definitions are provided below. Moreover, unless defined otherwise, all technical and scientific terms as used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure pertains.
Use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one”. Similarly, the word “another” may mean at least a second or more.
As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.
As used herein the term “textured current collector” refers to a current collector which has at least one surface with a continuous 3D structure formed thereon. The continuous 3D structure may be formed by electrochemical deposition of a conductive material, or by a technique comprising a mechanical and/or laser treatment, electrochemical oxidation (dissolution), chemical etching, or any other suitable techniques. It should be noted that the term “textured” is also used herein in connection with any other layer of the anode which comprises a continuous 3D structure. Such layer is for example the protective layer, the layer of active anode material, and the layer of surface treatment agent.
As used herein the term “lithiophilic surface” refers to a surface which has an affinity for lithium. The surface may be a surface of the current collector having a protective material thereon. Also, the surface may comprise a continuous 3D structure. The lithiophilic property may be conferred to the surface upon a plasma treatment.
The inventors have designed and performed a method for producing an anode for lithium batteries.
Our data confirm that when molten Li metal is applied to a Cu or Al foil (even at temperatures as low as 210° C.), the surface of the current collector metal starts forming an alloy and once the applied layer of molten Li solidifies, fragments of the current collector material can be found inside the Li layer or on its surface.
It should be noted that in
In the cases where the current collector thickness is very small, as the result of the interaction between the Li layer and the current collector surface, important holes start to appear in the current collector material. This may be an important disadvantage especially when the objective is to use very thin current collector foils (for example 4-5 μm) in order to minimize the production cost of the anode and to maximize the specific and volumetric energy density of the battery.
It should be noted that different categories of lithiophilic materials can be deposited on the barrier layer using electrochemical methods under controlled conditions (in terms of thickness and morphology of the deposit) in a time effective and scalable electrochemical set up. Depending on the nature of the lithiophilic material, at the stage of its deposition, the current collector may receive a cathodic current (becoming the cathode electrode during the lithiophilic deposition) or an anodic current. Accordingly, the current collector can be used as a cathode (for the deposition of elements such as Zn, Sn, Si, metallic borides, or even oxides such as ZnO, MnO2, or SnO2), or as anode (for deposition or formation of compounds such as CuO, Cu2O, SnO2, or MnO2).
The advantages of the electrochemical deposition compared to other approaches are as follows:
Two sets of current collectors were prepared using a 5 μ thick copper foil. In one set a 40 nm layer of Zn was deposited on the copper foil in an electrolytic cell to prepare Cu—Zn foil samples. For the second set, a layer of 300 nm of Ni (the thickness was estimated by using a quartz microbalance crystal) was deposited electrochemically before the deposition of the 40 nm Zn layer to prepare Cu—Ni—Zn foil samples. In order to evaluate the effect of the interaction between molten Li and Cu foil, in the presence of a lithiophilic material such as Zn, the two sets of prepared samples were tested by being put in contact with the same quantity of molten Li under the same conditions. For each test (carried out in an Ar glove box equipped with purification units to insure H2O, O2 and N2 levels below 1 ppm), approximately 0.1 g of molten Li (prepared by heating Li to 250° C. in a stainless steel syringe and applied using a mechanically controlled piston) was deposited on the surface of the sample (having a surface area of around 14 cm2) placed on a sample holder that assured the flatness of the sample and that allowed to control its temperature at around 230° C. Once the Li droplet deposited, it started to extend over the sample surface due to the lithiophilic action of the Zn layer. Each sample was allowed to be in contact with the molten Li droplet for a certain time interval (4 times of 10, 30, 60, and 120 seconds were tested) and then the sample was allowed to cool down to room temperature.
In order to evaluate the effect of the thickness of the Zn layer on its lithiophilic property, five square samples of 5 μm Cu foils (14 cm2) were electroplated with 300 nm of Ni followed by a Zn layer having a thickness of 40, 60, 80, 100, or 150 nm. The same set up mentioned in Example 1 was used to deposit controlled droplets of molten Li (0.1 g) and measure the contact angle of the droplets as a function of time.
As can be seen in
To evaluate the lithiophilic effect of Sn, three square samples of 5 μm Cu foils (14 cm2) were electroplated with 300 nm of Ni followed by a Sn layer having a thickness of 40, 60, or 80 nm. The same set up mentioned in Example 1 was used to deposit controlled droplets of molten Li (0.1 g) and measure the contact angle of the droplets as a function of time.
To evaluate the lithiophilic effect of ZnO, a sample of Cu—Ni—ZnO was prepared by electrodepositing a thin layer of ZnO on a Cu foils (14 cm2) having a 300 nm electrodeposited layer of Ni protection. The ZnO layer was electrodeposited by using Cu—Ni foil as a cathode in an electrolysis cell containing a 0.1 M Zn(NO3)2 solution as electrolyte and a Zn plate as anode. The electrolysis was carried out at a current density of 5 mA/cm2 and a temperature of 62° C. for a duration of 36 seconds. The thickness of the ZnO layer is estimated to be around 30 nm. The sample was then placed in a glove box similar to the one mentioned in Example 1 and heated to 250° C. on a heating plate. Li was then melted on the surface of sample by placing a Li rod made of extruded Li. Once the Li had melted, the excess Li was removed using a hand operated blade made of high temperature silicon.
To evaluate the lithiophilic effect of Sn using a Li alloy, the same type of experiment mentioned in Example 3 was carried out using Cu—Ni—Sn (40 nm) and a Li—Mg alloy having aa weight Li:Mg ratio of 90%-10%. The variation of the contact angle for Cu—Ni and Cu—Ni—Sn (40 nm) with molten Li and that of Cu—Ni—Sn (40 nm) with Li—Mg alloy is presented in
This example shows the feasibility of using an easily scalable method for applying a thin and uniform layer of Li on a current collector such as a 5 μm Cu foil using molten Li. A sample of 5 μm Cu foils (130 cm2) was electroplated with 300 nm of Ni followed by a Sn layer having a thickness of 40 nm. The sample was then applied manually at a constant speed of 2 cm/s on the top surface of an anilox roll immersed partially in a reservoir containing molten Li at a temperature of 260° C. The anilox roll had a length of 700 mm and a diameter of 19 mm. It presented inverted pyramidal features (20 pyramids per 25 mm) and a depth of around 400 μm in each pyramid. An SEM image of the sample (after cryofracture) is showed in
In order to show the feasibility of the deposition of a surface treatment layer on the deposited Li layer of the proposed Li anode material, a Cu—Ni—Sn—Li sample similar to that produced in Example 6 was treated by DC sputter. An average target value of 50 nm of Zn was deposited by applying a DC current of 50 mA on a Zn target of 99.9% purity under a vacuum of 0.008 mbar and using highly pure Ar (grade 6.0; 99.9999% purity).
Two square samples of 5 μm Cu foils (14 cm2) were electroplated with 300 nm of smooth Ni followed by the electrodeposition of a rough Ni layer having a 3D effect. Contrary to the smooth Ni layer, the 3D layer was electrodeposited at a high current density of 2000 mA/cm2 and a total charge of 15 C/cm2 using an NiSO4, NH4Cl solution as electrolyte. One of the samples with the Ni3D was then treated with non thermal atmospheric pressure plasma using a Plasma Etch handheld plasma wand. The device had an output of 18 W and the sample was treated using the nearfield module (for electrically conducting materials) at a distance of 2 mm and at a speed of around 10 mm/s. The same set up described in Example 1 was used to deposit controlled droplets of molten Li (0.1 g) on Cu—Ni as well as Cu—Ni-3DNi with and without plasma treatment. Due to the roughness of the Cu—Ni-3DNi samples and the fast spreading of the molten Li drop, it was challenging to do a comparison of the lithiophilic activity using the contact angle parameter. In this case, the molten Li drop was allowed to spread on the surface for two minutes and the total surface area of the spread Li was measured and used as an indication of lithiophilic activity of the substrate surface. The results are presented in
As will be understood by a skilled person, the method according to the invention comprises the following steps: a) providing a current collector; b) depositing a layer of protective material on the surface of the current collector; c) depositing a layer of a lithiophilic material on the layer of protective material; and d) depositing a layer of lithium material in molten form on a layer of the lithiophilic material, whereby the lithiophilic material reacts with the molten lithium material to form the anode active material. In embodiments of the invention, the method comprises a subsequent step e) depositing a layer of a surface treatment agent on the anode active material formed. In embodiments of the invention, a step a1) forming a continuous 3D structure on a surface of the current collector to obtain a textured current collector is conducted prior to conducting step b).
In embodiments of the invention, step c) is followed by a step c1) which is a plasma treatment of the lithiophilic material to obtain a plasma treated lithiophilic material. Then step d) is conducted. In other embodiments, step c) is altogether replaced by step c1). In such embodiments, the plasma treatment is conducted on the protective layer leading to the formation of a lithiophilic surface; preferably, the protective layer comprises a continuous 3D structure and/or the protective layer comprises Ni. The plasma treatment may be a thermal atmospheric pressure plasma or any other suitable plasma treatments.
In embodiments of the invention, a continuous 3D structure may be formed on a surface of the anode active material layer and/or a surface of the surface treatment agent layer. Accordingly, a step d1), forming a continuous 3D structure on a surface of the anode active material layer, is conducted right after step d); and/or a step e1), forming a continuous 3D structure on a surface of the surface treatment agent layer, is conducted right after step e).
The step of forming a continuous 3D structure on a surface of the current collector to obtain a textured current collector or on any other layer of the anode, may comprise providing some roughness on the surface of the current collector. This step may comprise a mechanical and/or a laser treatment, electrochemical oxidation, chemical etching, or any suitable techniques known to a skilled person. In embodiments of the inventions, the continuous 3D structure may be conferred to the anode active material layer and/or the surface treatment layer.
The step of depositing a layer of protective material on the surface of the current collector, step b), may comprise electrochemical deposition, electroless plating, or any other suitable techniques known to a skilled person.
The step of depositing a layer of a lithiophilic material on the layer of protective material, step c), may comprise an electrochemical oxidation or reduction, or any other suitable techniques known to a skilled person.
The step of depositing a layer of lithium material in molten form on the layer of lithiophilic material or on the lithiophilic surface, step d), may comprise infiltration methods, wave soldering, use of heated nozzles, anilox rolls, or any other suitable techniques.
As will be understood by a skilled person, the invention also provides for an anode produced by the method according to the invention. The anode may be single-sided or double-sided. Also, the anode may have a thickness between about 4 to about 5 μm.
As will be understood by a skilled person, the invention further provides for an apparatus adapted to conduct the method according to the invention which produces the anode. Use of the anode in the manufacture of a lithium battery as well as the manufacturing method for producing a lithium battery comprising using of the anode are also within the scope of the invention. Moreover, the invention provides for a lithium battery comprising the anode. The lithium battery may be a lithium-ion battery or an all-solid-state battery.
As will be understood by a skilled person, other variations and combinations may be made to the various embodiments of the invention as described herein above.
The scope of the claims should not be limited by the preferred embodiments set forth in the examples; but should be given the broadest interpretation consistent with the description as a whole.
The description refers to a number of documents, the contents of which are herein incorporated by reference in their entirety.
This application claims benefit of U.S. Provisional Patent Application No. 63/299,247 filed on Jan. 13, 2022. The content of this application is incorporated herein in its entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63299247 | Jan 2022 | US |
