Improved anode

Abstract

This invention relates to anodes comprising: a current collector; and a layer comprising active material comprising silicon on the current collector, wherein the layer comprises regions surrounded by gaps; wherein the regions comprise silicon; wherein the regions comprise sloped lateral surfaces; wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode. Also disclosed are lithium-ion cells and batteries comprising the anode. Also disclosed are methods of preparing the anodes and the lithium-ion cells. Also disclosed are uses of the anodes.

Description

[0001] Improved anode

[0002] The present invention relates to an improved anode comprising a current collector and a silicon active material, to a method of preparing the anode, and to a use of the anode in a lithium-ion cell or battery. The anode has a specific stable configuration which results in a high cycle life of the lithium-ion cell or battery, while providing a high capacity.

[0003] Background

[0004] Silicon has a high capacity to store lithium and is therefore a promising active anode material for lithium-ion batteries. When a battery is charged, lithium ions are inserted into the anode. This process is also known as lithiation. When a battery is discharged, the reverse occurs: lithium ions are extracted from the anode, which is also known as delithiation.

[0005] However, lithiation and delithiation of a silicon-comprising anode causes the silicon to respectively expand and contract. Silicon is typically present in a layer on the current collector of an anode. The volumetric expansion of the anode layer comprising silicon can be over 300%. This expansion causes large anisotropic stresses to occur within the anode material, cracking, fracturing, and crumbling the anode layer comprising silicon and causing detachment of silicon or parts of the layer from the anode current collector.

[0006] The appearance of cracks throughout the entire silicon-comprising anode layer can already be observed after the first cycle of lithiation-delithiation. These cracks are considered to be major causes of anode pulverization, early capacity fade, and (early) cell failures, which decrease the functional life (i.e. cycle life) of the lithium-ion battery. Cracking is also considered to be disadvantageous because it increases the surface area of silicon particles exposed to the electrolyte, leading to accelerated side reactions and cell failure. Cracks may manifest in different ways, for example as a network of gaps across the top surface of the silicon- comprising anode layer.

[0007] The state of the art teaches a large variety of different compositions and methods to improve the stability of the silicon anode and to reduce the aforementioned cracking.

[0008] For example, US2019157682A1 provides an anode slurry for improving the stability of a silicon anode, comprising a silicon-based material, a porous carbon aerogel, a binder material, a carbon active material, and a solvent, wherein the porous carbon aerogel has an average pore size from about 80 nm to about 500 nm.

[0009] However, there remains a need for simpler and improved anodes for use in lithium-ion batteries.

[0010] Brief description of the invention

[0011] Applicants have surprisingly found a beneficial use of the cracking behavior of a silicon-comprising anode. It was found that a specific configuration of an anode comprising a current collector and a layer comprising active material comprising silicon can be used in a lithium-ion cell which results in a high cycle life of the lithium-ion cell, while still providing a high capacity. This specific configuration comprises regions surrounded by gaps, wherein the regions comprise sloped lateral surfaces and wherein the gaps take up a specific portion of the area of the top surface area of the anode. It was found that the first cycle of lith iation- delithiation causes the specific configuration to be formed which remains substantially stable. The capacity of the lithium-ion cell remains high even after several hundred cycles. Without being bound to theory, it is thought that the specific configuration helps accommodate stresses and provide space for volume changes during lithiation-delithiation, and reduces or prevents loss of parts of the anode layer comprising silicon, resulting in a longer cycle life of the lithium-ion cell.

[0012] The specific configuration of the anode according to the invention may be achieved by different methods and is not limited to the formation of cracks after a first cycle of lithiation-delithiation.

[0013] The present invention provides an anode, in particular a non-pristine anode, comprising: a. a current collector; b. a layer comprising active material comprising silicon on the current collector, wherein the layer comprises regions surrounded by gaps; wherein the regions comprise silicon; wherein the regions comprise sloped lateral surfaces; wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode.

[0014] In one aspect, the invention provides a method of preparing an anode, the method comprising: a. providing a current collector; b. depositing active material comprising silicon on the current collector; c. forming regions surrounded by gaps in the active material; i. wherein the regions comprise sloped lateral surfaces; ii. wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and ill. wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode.

[0015] In another aspect, the invention provides a method of preparing a lithium-ion cell, the method comprising: a. providing an anode, comprising providing a current collector and depositing active material comprising silicon on the current collector; b. providing the anode, a cathode, and an electrolyte comprising lithium; c. combining the anode, the cathode, and the electrolyte to form a lithium- ion cell; d. lithiating the anode; and e. delithiating the anode to form regions; i. wherein the regions are surrounded by gaps; ii. wherein the regions comprise sloped lateral surfaces; ill. wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and iv. wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode; and optionally repeating the lithiating and delithiating at least once.

[0016] In another aspect, the invention provides a method of preparing a lithium-ion cell, the method comprising: a. providing an anode, comprising providing a current collector, depositing active material comprising silicon on the current collector, and forming a plurality of columnar structures comprising silicon; b. providing the anode, a cathode, and an electrolyte comprising lithium; c. combining the anode, the cathode, and the electrolyte to form a lithium- ion cell; d. lithiating the anode; and e. delithiating the anode to connect the columnar structures and to form regions comprising the columnar structures; i. wherein the regions are surrounded by gaps; ii. wherein the regions comprise sloped lateral surfaces ill. wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and iv. wherein the gaps comprise an area of from 5% to 35% of the top surface of the anode; and optionally repeating the lithiating and delithiating at least once.

[0017] In yet another aspect, the invention provides a method of preparing a lithium-ion cell comprising the anode according to the invention using the method according to the invention.

[0018] In another aspect, the invention provides a lithium-ion cell comprising the anode according to the invention.

[0019] In yet another aspect, the invention provides a battery comprising the anode according to the invention or the lithium-ion cell according to the invention.

[0020] In another aspect, the invention provides a use of the anode according to the invention in a lithium-ion cell or a battery or a use of the anode according to the invention in the manufacture of a lithium-ion cell or a battery.

[0021] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

[0022] Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

[0023] The patent, scientific, and technical literature referred to herein establish knowledge that was available to those skilled in the art at the time of filing. The entire disclosures of the issued patents, published, and pending patent applications, and other publications that are cited herein are hereby incorporated by reference to the same extent as if each was specifically and individually indicated to be incorporated by reference. In the case of any inconsistencies, the present disclosure will prevail.

[0024] Various aspects of the invention are described in further detail below.

[0025] Description of the figures

[0026] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

[0027] Figure 1 shows schematical representations of anodes. The shown anodes in Figure 1 are subjected to a formation cycle of at least one charge and at least one discharge.

[0028] Figure 1 A represents a two-dimensional cross section of (part of) an anode not according to the invention. The anode comprises a current collector (101 ) having a current collector surface (102) and a layer comprising active material comprising silicon (103) on the current collector (101 ). The layer comprises three regions (104) surrounded by gaps (106). Each region has a top surface (105). Each region has lateral surfaces (107) that are not sloped, but (substantially) perpendicular to the current collector plane (108). The mean distance between the regions is the same at the top surface of the regions as near the current collector surface.

[0029] Figures 1 B-G each represent a two-dimensional cross section of (part of) an anode according to the invention. Figures 1 B-D, F, and G represent two- dimensional cross sections, while figure 1 E represents a tilted cross section. Each of the anodes comprises a current collector (201) having a current collector surface (202), a current collector plane (208), and a layer comprising active material comprising silicon (203) on the current collector (201 ). The layer comprises three regions (204) surrounded by gaps (206). Each region has a top surface (205). Each region comprises sloped lateral surfaces (207). The mean distance between the regions is greater at the top surface of the regions than near the current collector surface. Opposing sloped lateral surfaces (207) may be angled differently relative to each other as can be seen when comparing for example figures 1 B and 1C. The sloped lateral surfaces (207) may be sloped in various ways, for example they may be straight, substantially straight, or curved. A fully straight two-dimensional or three-dimensional surface may be difficult to achieve due to the properties of silicon, in particular when exposed to lithiation and delithiation. Figures 1 B and 1C show (substantially) straight sloped lateral surfaces (207), while figures 1 D and 1 E show curved sloped lateral surfaces (207). Curved sloped lateral surfaces may include areas that are oriented (substantially) perpendicular to the current collector plane. Some or all of the sloped lateral surfaces of a region may be converged or be joined to each other near the current collector surface as is illustrated in figures 1 F and 1G and indicated by the arrow (209). Some opposing lateral surfaces may also connect directly to the surface of the current collector so that (substantially) no or a very minimal area of current collector surface is exposed to the gaps, indicated by the arrow (210) (see e.g. Figures 1 B-1 F (210)), wherein the opposing lateral surfaces respectively may or may not touch each other at the current collector surface. Moreover, it is indicated in Figure 1 D how the slope of the lateral sloped surfaces may be computed or determined. An line can be drawn from the starting point of the sloped surface, indicated by point (211) in Figure 1 D, to a second point, relating to the end point of the sloped lateral surface, indicated by point 212 in Figure 1 D. The angle (213) between the line extending from (211) to (212) and the substrate surface (202) defines the angle of the sloped lateral surface.

[0030] Figure 2 shows top-down Scanning Electron Microscopy (SEM) images of anodes according to the invention after the first two charge / discharge cycles. Lithium-ion cells comprising an anode according to the invention were prepared as set out in the Examples and subjected to two cycles of lithiation-delithiation,

[0031] Figure 2A shows an anode that was included in a cell comprising an ether- based electrolyte. Figure 2B shows an anode that was included in a cell comprising a carbonate-based electrolyte. A plurality of regions (301 , light areas) surrounded by gaps (302, narrow dark areas) can be observed. The top surface of an individual region (301 ) is fully surrounded by gaps (302). The regions comprise silicon and are part of the active material layer of the anode. The regions comprise columnar structures comprising silicon that have been fused together. The gaps comprise an area of from 5% to 35% of the total top surface area of the anode (including the area of the gaps) as can be determined from these images. The bar in the bottom right corner represents 100 pm and each graduation is equivalent to 10 pm.

[0032] Batteries (or cells) made with both electrolytes form regions with gaps inbetween as is depicted in the figures 2A and 2B. However, the resulting pattern differs for the type of electrolyte that is used. The gaps formed using the ether- based electrolyte, as reflected in Figure 2A, have typically close to perpendicular angles between gaps. This may also be referred to as T shape gaps. The gaps formed using the carbonate-base elect electrolyte, as is reflected in Figure 2B, have typically larger and / or smaller than 90° angles. This may also be referred to as Y shape gaps. Although both patterns are randomized patterns, the type of electrolyte was found to be influencing the shape of the gaps, at least seen from a top view.

[0033] Figure 3 shows cross sectional SEM images of anodes according to the invention after the first two charge / discharge cycles. Figure 3A shows a crosssection, Figures 3B and 3C show tilted cross-sections. Lithium-ion cells comprising an anode according to the invention were prepared as set out in the Examples and subjected to two cycles of lithiation-delithiation.

[0034] Figures 3A, 3B, and 3C show a layer comprising active material comprising silicon (403) on a current collector (401). Samples as presented in the figures 3A, 3B, and 3C all were produced using an ether-based electrolyte. The current collector (401) comprises a plurality of nodules (412). Regions comprising silicon (404) can be observed in the active material layer (403). Gaps (406) are present in between the regions (404). The regions (404) comprise sloped lateral surfaces (407) and lateral surfaces that are substantially perpendicular to the current collector plane. Some of the lateral surfaces (410) are joined to each other near the current collector surface (409), while other lateral surfaces are attached directly to the current collector surface (411), some of which are thusly attached facing opposing lateral surfaces such that (substantially) no or a very minimal area of current collector surface is exposed to the gaps (413). It can be observed that the distance between regions is greater at the top surface (405) than near the current collector surface (402). Hence, the sloped lateral surfaces (407) (and the gaps) form a V-shape. The regions comprise columnar structures comprising silicon that have been fused together. Typical V-shapes are indicated by dashed ellipses. The bar in the bottom right corner represents 50 pm and each graduation is equivalent to 5 pm. The anode of Figure 3C appears to not comprise any lateral surfaces that are substantially perpendicular to the current collector plane or any lateral surfaces that are joined to each other near the current collector surface. The white arrows in Figure 3C represent 14.45 pm. Figure 4A shows capacity retention of two lithium- ion cells comprising an ether-based electrolyte comprising an ether-based electrolyte. The lithium-ion cell indicated by the dashed line “X” was according to the disclosure and comprised typical V-shapes. The lithium-ion cell indicated by the dotted line “Y” was not according to the disclosure and did not comprise any typical V-shapes. The cells were prepared as set out in the Examples. The capacity retention of a cell is the capacity after the indicated number of cycles of chargingdischarging (lithiation-delithiation) relative to its capacity after the first cycle of lithiation-delithiation. It can be observed that the cells according to the disclosure (“X”) retain at least 80% of their initial capacity after a higher number of cycles compared to comparative cells (“Y”). Where the term according to the disclosure is stated, this can also be understood as according to some embodiments of the invention.

[0035] Figure 4B shows capacity retention of two lithium-ion cells comprising a carbonate-based electrolyte. The lithium-ion cell indicated by the dashed line “X” was according to the disclosure and comprised typical V-shapes. The lithium-ion cell indicated by the dotted line “Y” was not according to the disclosure and did not comprise any typical V-shapes. The cells were prepared as set out in the Examples. The capacity retention of a cell is the capacity after the indicated number of cycles of charging-discharging (lithiation-delithiation) relative to its capacity after the first cycle of lithiation-delithiation. It can be observed that the cells according to the disclosure (“X”) retain at least 80% of their initial capacity after a higher number of cycles compared to comparative cells (“Y”).

[0036] The anodes according to the invention relatively improved the cycle life of cells comprising a carbonate-based electrolyte to a similar extent as cells comprising an ether-based electrolyte. Hence, the type of electrolyte did not appear to have a substantial effect on the anodes according to the invention regarding cycle life improvement.

[0037] Figure 5 shows top-down SEM images of anodes according to the invention after the first two charge / discharge cycles (Figure 5A) and after 400 charge / discharge cycles (Figure 5B). Lithium-ion cells comprising an anode according to the invention were prepared as set out in the Examples and subjected to two (5A) and 400 (5B) cycles of lithiation-delithiation. A plurality of regions (501 , light areas) surrounded by gaps (502, narrow dark areas) can be observed. The top surface of an individual region (501 ) is fully surrounded by gaps (502). The regions comprise silicon and are part of the active material layer of the anode. The regions comprise columnar structures comprising silicon that have been fused together. The gaps comprise an area of from 5% to 35% of the total top surface area of the anode (including the area of the gaps) as can be determined from these images. The bar in the bottom right corner represents 50 pm and each graduation is equivalent to 5 pm. It can be observed that the regions and gaps of the anode of lithium-ion cells according to the present invention remain substantially stable and intact even after 400 cycles of full charge / discharge. For example, the gaps typically comprise an area of from 5% to 35% of the total top surface area of the anode in either an anode according to the invention after the first two charge / discharge cycles (Figure 5A) or after 400 charge / discharge cycles (Figure 5B), while the size of the top surface area of the regions also remains substantially the same.

[0038] Figure 6 shows SEM images of pristine anode material, prior to lithiation and delithiation, prepared according to the method disclosed in the Examples.

[0039] Figure 6A shows a top-down view. It can be observed that most of the surface of the current collector is covered by a layer of silicon active material. The bar in the bottom right corner represents 50 pm and each graduation is equivalent to 5 pm.

[0040] Figure 6B shows a tilted cross section of the pristine anode cut perpendicular to the current collector plane. A layer of silicon active material (603) has been deposited on the current collector (601). The arrows indicate measurements of the thickness of the layer of silicon active material (from left to right: 9.96 pm, 10.0 pm, 9.39 pm) and the current collector (from left to right: 12.1 pm, 11 .4 pm, 13.2 pm). The current collector (601) comprises a plurality of nodules (612). The silicon active material layer (603) is in the form of a plurality of columnar structures. The bar in the bottom right corner represents 20 pm and each graduation is equivalent to 2 pm.

[0041] Further details of the Figures are disclosed in the Examples below. The SEM images of the pristine material shown in figures 6A and 6B was obtained by using a foil of type B as indicated in Table 1 . The regions and gaps will be formed during a subsequent formation step.

[0042] Figure 7 shows a result of the formation conditions on the regions and gap area% as found by the present invention. Figure 7 shows different samples in a top view, wherein the top view shown is taken using SEM pictures.

[0043] Detailed description of the invention

[0044] The present invention relates to an anode comprising: a. a current collector; b. a layer comprising active material comprising silicon on the current collector, wherein the layer comprises regions surrounded by gaps; wherein the regions comprise silicon; wherein the regions comprise sloped lateral surfaces; wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode.

[0045] The specific configuration of the anode of the invention comprises several aspects, which together enable the improved anode. Some of these aspects are schematically illustrated in Figures 1 B-1G, while an anode not according to the invention is schematically illustrated in Figure 1A.

[0046] Individual regions are surrounded by gaps when viewed from the top of the anode, i.e. viewed towards the layer comprising active material. The regions surrounded by gaps can be observed in Figures 2 and 5. The regions have lateral surfaces facing the gaps.

[0047] The regions are such that the silicon active material has a large amount of space for volumetric expansion during lithiation. This is provided by a large distance between the regions, which is generally greatest at the top surface of the region. However, the regions are also such that the contact area between the current collector surface and the silicon active material is large, which enables a strong adhesion between the regions and the current collector. This is provided by a small distance between the regions near the current collector surface. Some regions may be connected to each other near the current collector surface. Direct exposure of the current collector surface to the gaps is thus minimal. The difference in distance between the regions at the top and near the current collector generally manifests by the lateral surfaces of the regions being sloped, preferably at an angle of from 40° to 85° to the current collector plane. The regions may additionally comprise some lateral surfaces that are at a substantially perpendicular angle to the current collector plane. The lateral surfaces may connect directly to the surface of the current collector (see e.g. Figures 1 B-1 E), optionally leaving a small area of current collector surface exposed to the gaps. They may also directly join or connect to each other near the current collector surface, thereby preventing exposure of the current collector surface to the gaps (see e.g. Figures 1 F-1 G (209)). Opposing lateral surfaces may also connect directly to the surface of the current collector so that (substantially) no or a very minimal area of current collector surface remains exposed to the gaps (see e.g. Figures 1 B-1 F (210)). Hence, the gaps surrounding the regions generally become narrower from the top surface of the regions towards the current collector surface. This particular shape of at least one sloped lateral surface of a region, preferably wherein the sloped lateral surface has an angle of from 40° to 85° to the current collector plane, wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface, can be considered a lateral surface having a V- shape, examples of which can be observed by the dashed ellipses in Figure 3. The gap next to such a V-shaped lateral surface can then be considered to have the V- shape as well. The opposing lateral surface to the V-shaped sloped lateral surface may also be sloped or it may have a substantially perpendicular angle to the current collector plane. This V-shape is thought to contribute to the advantageous properties of the anode of the present invention.

[0048] The V-shape combined with the greater distance between regions at the top surface than near the current collector is in contrast to conventional regions of the prior art that do not possess this feature. These typically have lateral surfaces that are oriented substantially perpendicular to the current collector plane, for example illustrated in Figure 1 A.

[0049] A gap area of 5% to 35% of the total top surface area of the anode was found to optimally balance space for expansion with total active material capacity. A higher gap area contains insufficient active material, while a lower gap area provides insufficient space for expansion. The combined features as described above provide an anode that can be used in a lithium-ion cell which results in a high cycle life of the lithium-ion cell, while still providing a high capacity.

[0050] The layer comprising active material comprising silicon according to the disclosure may be continuous or discontinuous. The layer may comprise areas where the current collector surface is exposed to the gaps. Preferably, the area where the current collector surface is exposed to the gaps is minimal. This is in order to maximize the amount of active material of the anode. Suitably, the active material may be arranged on both sides or only one side of the current collector.

[0051] Preferably, the sloped lateral surfaces may have an angle of from 40° to 85° to the current collector plane. Suitably, the sloped lateral surfaces may have an angle of from 50° to 85°, of from 60° to 85°, of from 40° to 80°, of from 50° to 80°, of from 60° to 80°, of from 40° to 75°, of from 50° to 75°, or of from 60° to 75° to the current collector plane. The orientation of the lateral surfaces can be determined from a cross-sectional electron microscope image of the anode with a SOC of 0% to 10%, wherein the cross section is perpendicular to the plane of the current collector.

[0052] Suitably, the sloped lateral surfaces may have an angle of from 40° to 85° to the top surface plane of the active material or the top surface plane of the anode. Suitably, the sloped lateral surfaces may have an angle of from 50° to 85°, of from 60° to 85°, of from 40° to 80°, of from 50° to 80°, of from 60° to 80°, of from 40° to 75°, of from 50° to 75°, or of from 60° to 75° to the top surface plane of the active material. Suitably, the sloped lateral surfaces may have an angle of from 50° to 85°, of from 60° to 85°, of from 40° to 80°, of from 50° to 80°, of from 60° to 80°, of from 40° to 75°, of from 50° to 75°, or of from 60° to 75° to the top surface plane of the anode.

[0053] Suitably, the sloped lateral surfaces may be converged near the current collector surface. Suitably, the sloped lateral surfaces may be converged near the current collector surface at an angle of from 5° to 50° to each other. Suitably, the sloped lateral surfaces may be converged near the current collector surface at an angle of from 5° to 40°, of from 5° to 30°, of from 10° to 50°, of from 10° to 40°, of from 10° to 30°, of from 15° to 50°, of from 15° to 40°, or of from 15° to 30°, to each other. Suitably, the sloped lateral surfaces may be joined near the current collector surface. Suitably, the sloped lateral surfaces may be joined near the current collector surface at an angle of from 5° to 50° to each other. Suitably, the sloped lateral surfaces may be joined near the current collector surface at an angle of from 5° to 40°, of from 5° to 30°, of from 10° to 50°, of from 10° to 40°, of from 10° to 30°, of from 15° to 50°, of from 15° to 40°, or of from 15° to 30°, to each other.

[0054] Preferably, near the current collector surface may be at the bottom 20% of the layer comprising active material. Suitably, near the current collector surface may be at the bottom 15% of the layer comprising active material.

[0055] Suitably, the regions may further comprise lateral surfaces having a substantially perpendicular angle to the current collector plane. Preferably, the substantially perpendicular angle to the current collector plane may be an angle of more than 85° and up to 90° to the current collector plane.

[0056] Suitably, the sloped lateral surfaces may be converged with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface.

[0057] Suitably, the sloped lateral surfaces may be converged with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface at an angle of from 5° to 50°. Suitably, the sloped lateral surfaces may be converged with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface at an angle of from 5° to 40°, of from 5° to 30°, of from 10° to 50°, of from 10° to 40°, of from 10° to 30°, of from 15° to 50°, of from 15° to 40°, or of from 15° to 30°. Suitably, the sloped lateral surfaces may be joined with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface. Suitably, the sloped lateral surfaces may be joined with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface at an angle of from 5° to 50°. Suitably, the sloped lateral surfaces may be joined with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface at an angle of from 5° to 40°, of from 5° to 30°, of from 10° to 50°, of from 10° to 40°, of from 10° to 30°, of from 15° to 50°, of from 15° to 40°, or of from 15° to 30°.

[0058] Preferably, near the current collector surface may be at the bottom 20% of the layer comprising active material. Suitably, near the current collector surface may be at the bottom 15% of the layer comprising active material. Suitably, the lateral surfaces may extend substantially linearly. Suitably, the sloped lateral surfaces may extend substantially linearly.

[0059] Preferably, the sloped lateral surfaces may extend for a distance of at least 50% of the total thickness of the layer comprising active material. Suitably, the sloped lateral surfaces may extend for a distance of at least 60%, of at least 70%, or of at least 80% of the total thickness of the layer comprising active material. Suitably, the sloped lateral surfaces may extend for a distance of from 50% to 100% of the total thickness of the layer comprising active material. Suitably, the sloped lateral surfaces may extend for a distance of from 60% to 100%, of from 70% to 100%, or of from 80% to 100% of the total thickness of the layer comprising active material.

[0060] Suitably, the sloped lateral surfaces may extend from the current collector. Suitably, the sloped lateral surfaces may extend from near the current collector. Preferably, near the current collector surface may be at the bottom 20% of the layer comprising active material. Suitably, near the current collector surface may be at the bottom 15% of the layer comprising active material.

[0061] The orientation of the lateral surfaces as disclosed above can be determined from a cross-sectional electron microscope image of the anode with a SOC of 0% to 10% perpendicular to the plane of the current collector.

[0062] The mean distance between the regions is greater at the top surface of the regions than near the current collector surface. Preferably, the mean distance between the regions may be the mean distance between the regions parallel to the current collector plane. Determination of the mean distance between the regions can be determined from a cross-sectional electron microscope image of the anode with a SOC of 0% to 10% perpendicular to the plane of the current collector.

[0063] Preferably, at the top surface may be at the top 5% of the top surface of the regions. Suitably, at the top surface may be at the top 3% or top 1% of the top surface of the regions. Preferably, near the current collector may be at the bottom 20% of the layer comprising active material. Suitably, near the current collector surface may be at the bottom 15% of the layer comprising active material.

[0064] Suitably, the mean distance at the top surface may be at least 110% of the mean distance near the current collector. Suitably, the mean distance at the top surface may be at least 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 250%, 300%, 350%, 400%, 450%, or 500% of the mean distance near the current collector.

[0065] Preferably, the mean distance between the regions may be at least 1 gm at the top surface of the regions. Preferably, the mean distance between the regions at the top surface of the regions may be the mean distance between the regions parallel to the current collector plane. Determination of the mean distance between the regions at the top surface can be determined from a top-down electron microscope image of the anode with a SOC of 0% to 10%. “Top-down” is herein understood to mean a viewing orientation at the layer comprising active material at an angle perpendicular to the plane of the layer.

[0066] Suitably, the mean distance between the regions may be at least 2 pm or at least 3 pm at the top surface of the regions. Suitably, the mean distance between the regions may be of from 1 pm to 10 pm, of from 1 pm to 8 pm, of from 1 pm to 7 pm, of from 2 pm to 10 pm, of from 2 pm to 8 pm, of from 2 pm to 7 pm, of from 3 pm to 10 pm, of from 3 pm to 8 pm, or of from 3 pm to 7 pm, at the top surface of the regions.

[0067] Suitably, the distance between the regions may be of from 1 pm to 10 pm at the top surface of the regions. Preferably, the distance between the regions at the top surface of the regions may be the distance between the regions parallel to the current collector plane. Suitably, the distance between the regions may be of from 1 pm to 8 pm, of from 1 pm to 7 pm, of from 1 pm to 6 pm, of from 1 pm to 5 pm, of from 2 pm to 10 pm, of from 2 pm to 8 pm, of from 2 pm to 7 pm, of from 2 pm to 6 pm, of from 2 pm to 5 pm, of from 3 pm to 10 pm, of from 3 pm to 8 pm, or of from 3 pm to 7 pm, at the top surface of the regions.

[0068] The gaps comprise an area of from 5% to 35% of the top surface area of the anode. Determination of the gap area percentage can be determined from a top- down electron microscope image of the anode with a SOC of 0% to 10%. The area of the gaps is a percentage of the total two-dimensional area of the top-down electron microscope image. Hence, any surface area increases due to irregularities of the shape of the top surface of the active material layer are not taken into account. Suitably, the gaps comprise an area of from 8% to 35%, of from 10% to 35%, of from 12% to 35%, of from 15% to 35%, of from 17% to 35%, of from 20% to 35%, of from 22% to 35%, or from 24% to 35% of the top surface area of the anode. Suitably, the gaps comprise of from 8% to 30%, of from 10% to 30%, of from 12% to 30%, of from 15% to 30%, of from 17% to 30%, of from 20% to 30%, of from 22% to 30%, or from 24% to 30% of the top surface area of the anode. Preferably, the gaps comprise an area of from 12% to 35%, preferably 18% to 35%, of from 19% to 35%, of from 20% to 35%, of from 18% to 30%, of from 19% to 30%, of from 20% to 30%, or from 22% to 30% of the top surface area of the anode.

[0069] It was found that a higher gap area percentage generally related to a higher cycle life of a lithium-ion cell comprising the anode according to the present invention. This may be attributed to the increased lateral space for volumetric expansion during lithiation.

[0070] In an embodiment, the present invention relates to an anode comprising: a. a current collector; b. a layer comprising active material comprising silicon on the current collector, wherein the layer comprises regions surrounded by gaps; wherein the regions comprise silicon; wherein the regions comprise sloped lateral surfaces having an angle of from 40° to 85° to the current collector plane; wherein the mean distance between the regions parallel to the current collector plane is greater at the top surface of the regions than at the bottom 20% of the layer comprising active material; and wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode.

[0071] The expansion area provided by the gaps can be further balanced by the size of the regions. As the regions are surrounded by gaps, a smaller region undergoes proportionally (e.g. per cm2anode or per gram anode material) a higher amount of undesired side-reactions (e.g. reactions with the electrolyte which generally results in loss of active lithium and therefore decreases the capacity of the cell over its lifetime) during lithiation and / or delithiation than a larger region. However, a larger region has proportionally (e.g. per cm2anode or per gram anode material) less space for volumetric expansion. The top surface area of a region can be used as an indication for the potential of a region to undergo volumetric expansion and undesired side-reactions. Hence, the mean top surface area of regions per gram anode or active material or per cm2anode may therefore preferably be in a suitable range. It was found that for the anodes of the present invention a particular range of mean top surface area of the regions resulted in further improved anodes.

[0072] Preferably, the regions may have a mean top surface area of at least 150 pm2. Suitably, the regions may have a mean top surface area of at least 160 pm2, at least 170 pm2, at least 180 pm2, at least 190 pm2, at least 200 pm2, at least 210 pm2, at least 220 pm2, at least 230 pm2, at least 240 pm2, or at least 250 pm2. Determination of the mean top surface area of the regions can be determined from a top-down electron microscope image of the anode with a SOC of 0% to 10%. The mean top surface area of the regions is a two-dimensional area as determined from the top-down electron microscope image. Hence, any surface area increases due to irregularities of the shape of the top surface of the active material layer are not taken into account.

[0073] Suitably, the regions may have a mean top surface area of from 150 pm2to 1500 pm2. Suitably, the regions may have a mean top surface area of from 150 pm2to 1200 pm2, of from 150 pm2to 1250 pm2, of from 150 pm2to 1000 pm2, of from 150 pm2to 800 pm2, of from 150 pm2to 700 pm2, of from 150 pm2to 600 pm2, of from 150 pm2to 500 pm2, or of from 150 pm2to 400 pm2. Suitably, the regions may have a mean top surface area of from 170 pm2to 1200 pm2, of from 170 pm2to 1250 pm2, of from 170 pm2to 1000 pm2, of from 170 pm2to 800 pm2, of from 170 pm2to 700 pm2, of from 170 pm2to 600 pm2, of from 170 pm2to 500 pm2, or of from 170 pm2to 400 pm2. Suitably, the regions may have a mean top surface area of from 200 pm2to 1200 pm2, of from 200 pm2to 1250 pm2, of from 200 pm2to 1000 pm2, of from 200 pm2to 800 pm2, of from 200 pm2to 700 pm2, of from 200 pm2to 600 pm2, of from 200 pm2to 500 pm2, or of from 200 pm2to 400 pm2. Suitably, the regions may have a mean top surface area of from 220 pm2to 1200 pm2, of from 220 pm2to 1250 pm2, of from 220 pm2to 1000 pm2, of from 220 pm2to 800 pm2, of from 220 pm2to 700 pm2, of from 220 pm2to 600 pm2, of from 220 pm2to 500 pm2, or of from 220 pm2to 400 pm2. Preferably, the regions may have a mean top surface area of from 150 pm2to 872 pm2, of from 150 pm2to 870 pm2, of from 150 pm2to 850 pm2, or of from 150 pm2to 800 pm2. Preferably, the regions may have a mean top surface area of from 290 pm2to 872 pm2, of from 290 pm2to 870 pm2, of from 290 pm2to 850 pm2, or of from 290 pm2to 800 pm2. Preferably, the regions may have a mean top surface area of from 295 pm2to 872 pm2, of from 295 pm2to 870 pm2, of from 295 pm2to 850 pm2, or of from 295 pm2to 800 pm2. Suitably, at least 90% of the regions each may have a top surface area of at least 150 pm2. Suitably, at least 90% of the regions each may have a top surface area of at least 160 pm2, at least 170 pm2, at least 180 pm2, at least 190 pm2, at least 200 pm2, at least 210 pm2, at least 220 pm2, at least 230 pm2, at least 240 pm2, or at least 250 pm2.

[0074] Suitably, at least 90% of the regions each may have a top surface area of from 150 pm2to 600 pm2, of from 150 pm2to 500 pm2, or of from 150 pm2to 400 pm2. Suitably, at least 90% of the regions each may have a top surface area of from 170 pm2to 600 pm2, of from 170 pm2to 500 pm2, or of from 170 pm2to 400 pm2. Suitably, at least 90% of the regions each may have a top surface area of from 200 pm2to 600 pm2, of from 200 pm2to 500 pm2, or of from 200 pm2to 400 pm2. Suitably, at least 90% of the regions each may have a top surface area of from 220 pm2to 600 pm2, of from 220 pm2to 500 pm2, or of from 220 pm2to 400 pm2. Preferably, at least 90% of the regions each may have a top surface area of from 150 pm2to 872 pm2, of from 150 pm2to 870 pm2, of from 150 pm2to 850 pm2, or of from 150 pm2to 800 pm2. Preferably, at least 90% of the regions each may have a top surface area of from 290 pm2to 872 pm2, of from 290 pm2to 870 pm2, of from 290 pm2to 850 pm2, or of from 290 pm2to 800 pm2. Preferably, at least 90% of the regions each may have a top surface area of from 295 pm2to 872 pm2, of from 295 pm2to 870 pm2, of from 295 pm2to 850 pm2, or of from 295 pm2to 800 pm2.

[0075] Preferably, the gaps may be contiguous. Suitably, the gaps may be interconnected. Preferably, the regions may have a polygonal shape. Suitably, each of the regions may have a substantially different polygonal shape. The aforementioned configurations can be determined from a top-down electron microscope image of the anode with a SOC of 0% to 10%.

[0076] Without being bound to theory, it is thought that, in the present disclosure, the first cycle of lithiation and delithiation causes reactions that alter the structure of pristine silicon of the anode layer comprising active material on a current collector such that regions appear that are surrounded by gaps, wherein part of the silicon-comprising material in the regions is joined together. Deposited silicon on a current collector which has not undergone any lithiation or delithiation is also known in the art as pristine silicon. In one example according to the invention, pristine silicon may be deposited on a current collector such that columnar structures are formed. After the first cycle of lithiation and delithiation, some of the columnar structures may cluster and join together, while still being attached to the current collector, thereby resulting in the particular V-shape as disclosed above. Such columnar structures may therefore be particularly suitable for anodes according to the present invention, because the vertical structure of the columns may act as fracture points for formation of the regions surrounded by gaps. A region may be formed by one or more columns, preferably a region is formed by a plurality of columns.

[0077] Preferably, the regions may comprise columnar structures comprising silicon. Suitably, the columnar structures may extend in a substantially perpendicular direction from the surface plane of the current collector. The orientation of the columnar structures can be determined from a cross-sectional electron microscope image of the anode with a SOC of 0% to 10%, wherein the cross section is perpendicular to the plane of the current collector.

[0078] Suitably, at least 95% of the regions may comprise a plurality of interconnected or adjoined columnar structures comprising silicon. Suitably, at least 96%, at least 97%, at least 98%, at least 99%, about 100%, or substantially 100% of the regions may comprise a plurality of interconnected or adjoined columnar structures comprising silicon. Suitably, the columnar structures may extend in a substantially perpendicular direction from the surface plane of the current collector.

[0079] Suitably, the regions may comprise a solid electrolyte interphase (SEI) between the interconnected or adjoined columnar structures. Suitably, the interconnected or adjoined columnar structures may be directly connected. Suitably, the regions may comprise grain-like column boundaries between the interconnected or adjoined columnar structures.

[0080] In an embodiment, advantageously the layer comprising active material may be one wherein the boundaries of the columnar structures resemble grain-like column boundaries, preferably the boundaries of the columnar structures of the regions may resemble grain-like column boundaries.

[0081] Suitably, the gap between regions increases substantially linearly and / or substantially parabolically in relation to the distance from the current collector.

[0082] According to the present disclosure, “grain-like column boundaries” refers to a type of interface or region between interconnected or adjoining silicon columnar structures that resemble grain or crystal boundaries as customarily defined for grains consisting of crystalline atomic lattices. So, although the plurality of silicon columnar structures comprises potentially entirely amorphous silicon-based material, the silicon columnar structures may exhibit a grain-like engagement between interconnected or adjoining columnar structures.

[0083] Preferably, the anode may have undergone lithiation and delithiation at least once. Suitably, the anode may have undergone lithiation and delithiation at least twice. Preferably, the active material may have undergone lithiation and delithiation at least once. Suitably, the active material may have undergone lithiation and delithiation at least twice. Preferably, the silicon may have undergone lithiation and delithiation at least once. Suitably, the silicon may have undergone lithiation and delithiation at least twice.

[0084] It is understood that the specific configuration of the anode according to the invention is determined when the anode is in a substantially discharged and delithiated state (i.e., having a state of charge (SOC) of 0% to 10%).

[0085] Preferably, the anode may be substantially delithiated. Preferably, the active material may be substantially delithiated. Preferably, the silicon may be substantially delithiated. Suitably, substantially delithiated may be a state of lithiation wherein the anode, active material, or silicon comprises less than 10% lithium ions compared to a substantially fully lithiated state, preferably compared to a fully lithiated state.

[0086] The current collector of the anode may be preferably made of a material having good electrochemical stability, electrical conductivity, and mechanical strength. Suitably, the current collector may comprise copper, aluminium, nickel, titanium, carbon, iron, chromium, stainless steel, or an alloy thereof. Preferably, the current collector comprises copper, nickel, or an alloy thereof. More preferably, the current collector comprises copper or an alloy thereof. More preferably, the current collector comprises copper.

[0087] As disclosed above, volumetric expansion and reduction of the anode comprising a layer comprising active material comprising silicon causes large anisotropic stresses to occur within the anode material. As the layer comprising active material is attached to the current collector, the current collector preferably has properties that control any potential cracking, fracturing, crumbling, and detachment of the layer comprising active material or parts thereof from the anode current collector.

[0088] In one example, the current collector may have a particular resistance to breaking or (plastic) deformation, which may assist in managing the stresses of the active silicon material, thereby controlling the formation of the specific anode structure according to the present invention during the first cycle of lithiation- delithiation. The particular resistance to breaking or (plastic) deformation may also assist in maintaining the specific anode structure according to the present invention during further cycles.

[0089] Preferably, the current collector may have a thickness of from 5 pm to 20 pm.

[0090] Suitably, the current collector may have an ultimate tensile strength of at least 100 MPa. Suitably, the current collector may have an ultimate tensile strength of at least 150 MPa, at least 200 MPa, at least 220 MPa, at least 250 MPa, at least 260 MPa, at least 270 MPa, at least 280 MPa, or at least 290 MPa. Suitably, the current collector may have an ultimate tensile strength of from 100 MPa to 1000 MPa, of from 100 MPa to 500 MPa, of from 150 MPa to 1000 MPa, of from 150 MPa to 500 MPa, of from 200 MPa to 1000 MPa, of from 200 MPa to 500 MPa, of from 250 MPa to 1000 MPa, of from 250 MPa to 500 MPa, or of from 250 MPa to 480 MPa.

[0091] Suitably, the current collector may have a yield strength of at least 50 MPa. Suitably, the current collector may have a yield strength of at least 80 MPa, at least 90 MPa, at least 100 MPa, at least 110 MPa, at least 120 MPa, at least 130 MPa, at least 140 MPa, or at least 150 MPa. Suitably, the current collector may have a yield strength of from 50 MPa to 500 MPa, of from 50 MPa to 250 MPa, of from 80 MPa to 500 MPa, of from 80 MPa to 250 MPa, of from 100 MPa to 500 MPa, of from 100 MPa to 250 MPa, of from 120 MPa to 500 MPa, or of from 120 MPa to 250 MPa.

[0092] Ultimate tensile strength of materials is typically provided by commercial suppliers of the materials. Ultimate tensile strength may for example be determined by using a Universal Testing Machine (also known as a tensometer or force tester) and standard methods and calculations in the art.

[0093] Yield strength of materials is typically provided by commercial suppliers of the materials. Yield strength may for example be determined by using a Universal Testing Machine (also known as a tensometer or force tester) and standard methods and calculations in the art.

[0094] It was found that a particular roughness of the current collector further increases, and may even be considered a key element in, the advantageous configuration of the anode according to the invention, specifically with regard to the V-shape of the lateral surfaces of the regions, the gap area, and the top surface area of the regions according to the present invention. In addition, without being bound to theory, it is thought that a roughened current collector may be conducive to distributing the stresses generated in the anode during lithiation and delithiation, and that the roughness may improve the adhesion of the silicon active material to the current collector.

[0095] Preferably, the current collector may be roughened. Suitably, the current collector may comprise nodules. Suitably, the nodules have been formed using electrodeposition or electroplating.

[0096] Suitably, the current collector may exhibit a surface roughness value selected from at least one of the following: an Sdr value of at least 40%; an Sz value of at least 4 pm; an Sq value of at least 0.43 pm; and an Sa value of at least 0.2 pm; or any combination thereof. Suitably, the current collector may exhibit a surface roughness having an Sdr value of at least 40%, an Sz value of at least 4 pm, an Sq value of at least 0.43 pm, and an Sa value of at least 0.2 pm.

[0097] Suitably, the Sdr value may be at least 50%, at least 60%, at least 75%, at least 90%, at least 92%, at least 95%, at least 120%, at least 135%, at least 150%, or at least 160%. Suitably, the Sdr value may be of from 40% to 250%, of from 50% to 250%, of from 60% to 250%, of from 90% to 250%, of from 120% to 250%, of from 135% to 250%, of from 150% to 250%, or of from 160% to 250%. Suitably, the Sdr value may be of from 40% to 500%, of from 50% to 500%, of from 60% to 500%, of from 90% to 500%, of from 120% to 500%, of from 135% to 500%, of from 150% to 500%, or of from 160% to 500%.

[0098] Suitably, the Sz value may be at least 4.5 pm, at least 4.7 pm, at least 5 pm, at least 5.5 pm, at least 6 pm, at least 7.5 pm, or at least 8 pm. Suitably, the Sz value may be of from 4 pm to 14 pm, of from 4.5 pm to 14 pm, of from 4.7 pm to 14 pm of from 5 pm to 14 pm, of from 5.5 pm to 14 pm, of from 6 pm to 14 pm, of from 7.5 pm to 14 pm, or of from 8 pm to 14 pm. Suitably, the Sq value may be at least 0.45 pm, at least 0.5 pm, at least 0.55 Um, at least 0.6 pm, at least 0.7 pm, at least 0.8 pm, or at least 0.85 pm. Suitably, the Sq value may be of from 0.43 pm to 2.5 pm, of from 0.45 pm to 2.5 pm, of from 0.5 urn to 2.5 pm, of from 0.55 pm to 2.5 pm, of from 0.6 pm to 2.5 pm, of from 0.7 Um to 2.5 pm, of from 0.8 pm to 2.5 pm, or of from 0.85 pm to 2.5 pm.

[0099] Suitably, the Sa value may be at least 0.3 pm, at least 0.35 pm, at least 0.4 Um, at least 0.45 pm, or at least 0.65 pm. Suitably, the Sa value may be of from 0.2 Um to 0.9 pm, of from 0.3 pm to 0.9 pm, of from 0.35 pm to 1 pm, of from 0.4 pm to

[0100] 1 urn, or of from 0.65 pm to 1 pm. Suitably, the Sa value may be of from 0.2 pm to

[0101] 2 urn, of from 0.3 pm to 2 pm, of from 0.35 pm to 2 pm, of from 0.4 pm to 2 pm, or of from 0.65 pm to 2 pm.

[0102] Suitably, the current collector, in particular at least a surface of the current collector facing the active material, comprises a Summit Density (Sds) situated between 0.15 pm-2to 0.7 pm-2, preferably between 0.18 pm-2to 0.32 pm-2. Suitably, the current collector, in particular at least a surface of the current collector facing the active material, comprises a Mean Summit Curvature (Ssc) situated between 15 pm-1to 40 pm-1, preferably between 20 pm-1to 30 pm-1, more preferably between 18 pm-1to 26 pm-1. Suitably, the current collector, in particular at least a surface of the current collector facing the active material, comprises a Root Mean Square Gradient (Sdq) situated between 1.1 rad to 1.4 rad. It was surprisingly found that these surface parameters are beneficial to establish the regions that are surrounded by gaps, wherein the regions comprise sloped lateral surfaces. The sloped lateral surfaces (which may be referred to as V-shaped gaps), provided an improved cycle life to anodes used in cells. It is believed, without being bound to theory, that these surface parameters contribute to shaping the lateral sloped surfaces during the formation step. It is believed to be attributed, at least in part, to the bonding strength to the current collector.

[0103] It was surprisingly found, and without being bound to theory, that narrower peaks or nodules are related to the current collector roughness. This may contribute significantly to the sloped lateral surfaces (V-shape). The sharpness or narrowness of the surface peaks is defined for example by the Ssc parameter. Yet, and again without being bound to theory, it is believed that the Developed Interfacial Area Ration (Sdr) also contributes to the lateral sloped surfaces. The Sdr parameter defines the percentage of the definition area’s (peaks) additional surface area contributed by texture as compared to a planar definition area. This may be computed, for example, by the following formula ((rough area / projected area)*100% -100%). A flat surface, has an Sdr value of 0%. It was found that good results are achieved by Sdr values situated in the range of 140% to 250%, preferably of 165% to 200%, more preferably of 170% to 180%.

[0104] The surface parameters as outlined above are standard metrics used to characterize surface topography in three dimensions. Sa represents the arithmetic mean height, quantifying the average deviation of surface points from the mean plane. Sq is the root mean square height, providing a measure of surface roughness by accounting for the square of deviations from the mean plane. Sz defines the maximum height of the surface, determined as the sum of the largest peak height and the deepest valley depth within a sampling area. Sds measures the density of summits, reflecting the number of discrete peaks per unit area. Ssc quantifies the mean curvature of these summits, providing insight into their sharpness. Sdq represents the root mean square gradient of the surface, indicating the steepness of surface features. Lastly, Sdr calculates the developed interfacial area ratio, expressing the percentage increase in surface area due to surface texture compared to a flat reference plane. These parameters can be detected and calculated using surface measurement techniques such as confocal microscopy, white light interferometry, or atomic force microscopy, in conjunction with surface analysis software.

[0105] Surface roughness values of materials are typically provided by commercial suppliers of the materials. For example, the surface roughness may be determined by the standard method ISO 25178, preferably by using white light interferometry.

[0106] In one embodiment the current collector may exhibit a surface roughness having an Sdr value of at least 100%, an Sa value of at least 0.4 pm, an Sq value of at least 0.5 pm, and an Sz value of at least 4.5 pm.

[0107] It was found that particular properties of the silicon may further increase the advantageous configuration of the anode according to the invention, specifically with regard to the V-shape of the lateral surfaces of the regions, the gap area, and the top surface area of the regions according to the present invention. For example, without being bound to theory, it is thought that the mass loading of the silicon on the current collector and the porosity of the silicon may affect the number of lithium ions that can interact with silicon atoms (per gram silicon), also known in the art as silicon utilization, which plays an important role in the reactions during lithiation- delithiation of the active material and resultant formation of the anode according to the invention. Furthermore, the porosity of the silicon may affect the formation of the V-shape of the lateral surfaces of the regions, the gap area, and the top surface area of the regions according to the present invention.

[0108] Suitably, the layer comprising active material comprising silicon may have a thickness of from 5 pm to 20 pm. Suitably, the layer comprising active material comprising silicon may have a thickness of from 5 pm to 15 pm, or of from 8 pm to 20 pm.

[0109] Suitably, the silicon may comprise amorphous silicon, optionally further comprising nano-crystalline silicon. Suitably, the amorphous silicon and / or nanocrystalline silicon may optionally further comprise silicon-containing compounds. A silicon-containing compound may be a compound comprising a silicon atom bound to another atom different from silicon. Suitably, the active material may have an amorphous structure, optionally wherein the amorphous structure has nanocrystalline regions.

[0110] The term "amorphous silicon" herein is understood to mean as comprising protocrystalline silicon, which is a definition for amorphous silicon comprising a fraction of nano-crystalline silicon. This fraction may be up to about 30% of the silicon layer. For ease of reference the term amorphous silicon will be used herein to indicate that the silicon layer comprises amorphous silicon, in which nanocrystalline regions of the silicon layer may be present with a fraction of nanocrystalline silicon up to about 30%. The silicon layer according to the disclosure may comprise silicon oxide.

[0111] An adhesion layer comprising a metal, metal alloy and / or metal salts and / or oxide attached to the current collector may advantageously increase the adhesion of the silicon to the current collector of the anode of the present invention, see WO2021029769. Such an interstitial adhesion layer is not essential. According to the present disclosure, the current collector comprising a metal, metal alloy and / or metal salts and / or oxide adhesion layer may suitably comprise an adhesion layer. This adhesion layer increases the adhesion between silicon material and the current collector material as different complexes of silicon are being formed on the interphase between the current collector material and the silicon. Such an adhesion layer preferably may comprise nickel, zinc, or tin, such as ZnO or SnC>2. The adhesion layer can be formed by coating or depositing the metal, metal alloy and / or metal salts and / or oxide on the current collector material. Preferably, the adhesion layer may be in a layer at a thickness of from 0.1 to 5 nm, more preferably of from 1 to 2 nm.

[0112] Suitably, the current collector according to the disclosure may comprise a metal, metal alloy and / or metal salts and / or oxide. The metal, metal alloy and / or metal salts and / or oxide according to the disclosure may be advantageously selected from aluminium, copper, nickel, tin, tin, indium and zinc, preferably nickel, ZnO, or SnO2, more preferably ZnO.

[0113] Suitably, the current collector may comprise a copper or nickel core layer, preferably a core layer doped with oxides or fluorides of zinc, aluminium, tin or indium. Preferably, the metal, metal alloy and / or metal salts and / or oxide or the core layer may be in a layer at a thickness of from 0.1 to 5 nm, more preferably of from 1 to 2 nm. Preferably, a current collector according to the disclosure comprising copper or nickel may comprise nickel, ZnO, or SnO2.

[0114] Suitably, the anode may comprise an adhesion layer between the current collector and the layer comprising active material. Preferably, the adhesion layer may comprise nickel, zinc, tin, chromium, or silane. Preferably, the adhesion layer may comprise nickel, ZnO, or SnO2. More preferably, the adhesion layer may comprise ZnO.

[0115] The term “doping” is herein understood to mean introducing a trace of an element into a material to alter the original electrical properties of the material or to improve the crystal structure of the silicon material.

[0116] Lithium-ion cells and batteries

[0117] The present invention also relates to a lithium-ion cell comprising the anode according to the invention. A unit that incorporates at least an electrolyte, a cathode, a separator, and the anode according to the invention can be considered a lithium-ion cell. Preferably, the lithium-ion cell comprises an electrolyte, a cathode, a separator, and the anode according to the invention. Suitably, the lithium-ion cell comprises an electrolyte.

[0118] The anode according to the present invention can be used in any type of lithium-ion cell. Different types of cathodes, separators, or electrolytes are generally not expected to negatively affect the advantageous effects of the anode. The skilled person may suitably select specific cathodes, separators, and / or electrolytes that enhance specific capabilities of the lithium-ion cell independently from the anode according to the present invention.

[0119] In the context of the present disclosure a lithium-ion cell may contain one or more anodes.

[0120] Cathodes suitable to use in the present disclosure are known to the skilled person and are commercially available.

[0121] Separators are present to prevent short circuits forming between the cathode and anode, while still allowing ions to flow between both electrodes.

[0122] The separator may be suitably selected from: (i) a glass fiber; (ii) a porous polymer film with or without a ceramic coating, such as a polyethylene- or polypropylene-based material, or (iii) a composite (e.g., a porous film of inorganic particles and a binder). One exemplary polymeric separator is a Celgard© K1640 polyethylene (PE) membrane. Another exemplary polymeric separator is a Celgard© 2500 polypropylene membrane. Another exemplary polymeric separator is a Celgard© 3501 surfactant-coated polypropylene membrane. Another set of exemplary porous polymer film with a ceramic coating are the PE and PP separators obtainable from Gelon. One example of such a separator is the Gelon 16 pm thick PE Battery separator, which comprises a 12 pm thick polyethylene polymer film, coated on both sides with a 2 pm thick ceramic alumina layer to afford a separator with a porosity of 38%.

[0123] The separator may optionally be infused with an electrolyte.

[0124] An electrolyte is a component that transfers ions between the cathode and the anode. Electrolytes suitable to use in the present disclosure are known to the skilled person and are commercially available.

[0125] Suitably, the electrolyte may comprise a medium and a lithium salt. Suitably, the medium may be liquid or solid. Suitably, the medium may comprise other additives. Suitably, the medium may comprise a non-aqueous solvent. Suitably, the medium may comprise a diluent.

[0126] Suitably, the electrolyte may be solid such as a ceramic electrolyte, a polymer, or a gel. The lithium salt in a solid ceramic electrolyte is usually present as a lithium metal oxide. Examples of solid ceramic electrolytes are lithium super ion conductors, argyrodites, sulfide solid electrolytes, and perovskites optionally arranged as an amorphous structure. Suitably, the electrolyte may comprise a lithium salt. The lithium salt, or combination of lithium salts, participates in the cell’s charge and discharge processes. Lithium salts suitable to use in the present disclosure are known to the skilled person and are commercially available.

[0127] Suitably, the electrolyte may comprise a non-aqueous solvent. Suitably, the non-aqueous solvent may be selected such that the lithium salt has a solubility in the selected solvent of from 0.5 M (mole / dm3) to 5 M at 25 °C and 1 atm.

[0128] Suitably, the non-aqueous solvent may be selected from a nonaqueous solvent comprising at least one of the following components (i) an ester, (ii) a sulfur-containing solvent, (iii) a phosphorus-containing solvent, (iv) an ether, (v) a nitrile, or (vi) any combination thereof.

[0129] Examples of suitable esters include, but are not limited to: diethyl carbonate (DEC); difluoroethylene carbonate (DFEC); dimethyl carbonate (DMC); ethyl methyl carbonate (EMC); ethylene carbonate (EC); methyl 2, 2, 2, -trifluoroethyl carbonate (MFEC); propylene carbonate (PC); trifluoroethylene carbonate (TFEC); trifluoropropylene carbonate (TFPC); 2, 2, 2, -trifluorethyl trifluoroacetate; 2,2,2- trifluoroethyl acetate; alkyl carboxylic acid esters, such as ethyl acetate; ethyl propionate; ethyl trifluoroacetate; methyl butyrate, or any combination thereof.

[0130] Preferably, the sulphur-containing solvent may be selected from sulfone solvents, sulfoxide solvents or any combination thereof. Examples of suitable sulphur-containing solvents include, but are not limited to: dimethyl sulfone; dimethyl sulfone; ethyl methyl sulfone (EMS); ethyl vinyl sulfone (EVS); tetramethylene sulfone (TMS, sulfolane); dimethyl sulfoxide; ethyl methyl sulfoxide; ethyl methyl sulfone (EMS); ethyl vinyl sulfone (EVS); tetramethylene sulfone (TMS, sulfolane); dimethyl sulfoxide; ethyl methyl sulfoxide; or any combination thereof.

[0131] Preferably, the phosphorus-containing solvent may be selected from organophosphorus compounds (such as organic phosphate, phosphites, phosphonates, phosphoramides), phosphazenes (organic or inorganic) or any combination thereof. These phosphorus-containing solvents are generally flame retardant. Examples of suitable phosphorus-containing solvents include, but are not limited to: bis(2,2,2-trifluoroethyl) methyl phosphate; tributyl phosphate; triethylphosphate (TEPa); trimethyl phosphate (TMPa); triphenyl phosphate; tris (2,2,2-trifluoroethyl) phosphate; trimethyl phosphite; triphenyl phosphite; tris(2,2,2- trifluoroethyl) phosphite; dimethyl methylphosphonate; diethyl ethylphosphonate; diethyl phenylphosphonate; bis(2,2,2-trifluorethyl) methylphosphonate; hexamethylphosphoramide; hexamethoxyphosphazene (CAS: 957-13-1 ); hexamethoxycyclotriphosphazene (CAS: 6607-30-3); hexafluorophosphazene (CAS: 15599-91-4); or any combination thereof.

[0132] Examples of suitable ethers include, but are not limited to: 1 ,2- dimethoxyethane (DME); diethylene glycol dimethyl ether (diglyme, DEGDME); triethylene glycol dimethyl ether (triglyme); tetraethylene glycol dimethyl ether (tetraglyme); 1 ,3-dioxolane (DOL); allyl ether; or any combination thereof.

[0133] Examples of suitable nitriles include, but are not limited to: acetonitrile; propionitrile; succinonitrile; adiponitrile (CAS: 111-69-3); or any combination thereof.

[0134] Suitably, the non-aqueous solvent may comprise a carbonate and / or an ether.

[0135] Suitably, the carbonate may be selected from: diethyl carbonate (DEC); difluoroethylene carbonate (DFEC); dimethyl carbonate (DMC); ethyl methyl carbonate (EMC); ethylene carbonate (EC); methyl 2, 2, 2, -trifluoroethyl carbonate (MFEC); propylene carbonate (PC); trifluoroethylene carbonate (TFEC); trifluoropropylene carbonate (TFPC); or any combination thereof.

[0136] Suitably, the ether may be selected from: 1 ,2-dimethoxyethane (DME); diethylene glycol dimethyl ether (diglyme, DEGDME); triethylene glycol dimethyl ether (triglyme); tetraethylene glycol dimethyl ether (tetraglyme); 1 ,3-dioxolane (DOL); allyl ether; or any combination thereof.

[0137] Suitably, the electrolyte may comprise a diluent. The diluent may be advantageously selected such that the lithium salt has a solubility in the selected solvent of less than 0.3 M (mole / dm3) at 25 °C and 1 atm. Suitably, the diluent may be selected such that the lithium salt has a solubility in the selected diluent of less than 0.2 M, preferably of less than 0.1 M, more preferably of less than 0.05 M or of less than 0.01 M at 25 °C and 1 atm.

[0138] Suitably, the diluent may be selected from a diluent comprising one or more of: a fluoroalkyl ether; a fluorinated orthoformate, a fluorinated carbonate, a fluorinated borate; or a combination thereof.

[0139] Suitably, the diluent may be selected from: a fluoroalkyl ether; a fluorinated orthoformate, a fluorinated carbonate, a fluorinated borate; or a combination thereof. Examples of suitable diluents include, but are not limited to: 1 ,1 ,2,2- tetrafluoroethyl-2,2,2,3-tetrafuoropropyl ether (TTE); 1 ,1 ,2,2-tetrafluoroethyl-2,2,2- trifluoroethylether (TFTFE); 1 ,2,2,2-tetrafluoroethyl trifluoromethyl ether; 1 H,1 H,5H-octafluoropentyl 1 ,1 ,2,2-tetrafluoroethyl ether (OTE); bis(2,2,2- trifluoroethyl) carbonate; bis(2,2,2-trifluoroethyl) ether(BTFE); bis(2,2,2- trifluoroethyl) methyl orthoformate (BTFEMO); ethoxynonafluorobutane (EOFB); heptafluoroisopropyl methyl ether; methoxynonafluorobutane (MOFB); tris(2,2,2- trifluoroethyl) borate; tris(2,2,2-trifluoroethyl) orthoformate (TFEO); tris(2,2,3,3,3- pentafluoropropyl) orthoformate (TPFPO); tris(2,2,3,3-tetrafuoropropyl) orthoformate (TTPO); tris(2,2-difluoroethyl) orthoformate (TDFEO); tris(hexafluoroisopropyl) orthoformate (THFiPO); or any combination thereof.

[0140] Suitably, the electrolyte additionally may comprise an additive. The additive has a different composition than: (i) the lithium salt; (ii) the solvent; and (iii) the diluent. Optionally, the additive may be a flame retardant.

[0141] Suitably, the additive may comprise: 4-Fluoro-1 ,3-dioxolan-2-one (FEC, CAS: 114435-02-8), 1 ,3-Dioxol-2-one (VC, vinylene carbonate, CAS: 872-36-6), 1 ,4-Dicyanobutane, (adiponitrile, CAS: 111 -69-3), Lithium difluorophosphate (LiDFP), 4,5-dimethylene-1 ,3-dioxolan-2-one; 1 ,3,2-dioxathiolane-2-oxide (CAS: 3741-38-6); 1 ,3,2-dioxathiolane-2,2-dioxide(CAS: 1072-53-3); 1 ,3,2-dioxathiane- 2,2-dioxide (DTD, CAS: 1072-53-3); 3-methyl-1 ,4,2-dixoazol-5-one (CAS: 854849- 14-2); Tris(2,2,2-trifluoroehtyl)phosphite (TTFEPi, CAS: 370-69-4); 1 ,3,2- Dioxathiane 2-oxide (CAS: 4176-55-0); 1 -methylsulfonylethene (CAS: 3680-02-2); 1 -ethenylsulfonylethene (CAS: 77-77-0); or any combination thereof.

[0142] Suitably, the lithium-ion cell may comprise a non-aqueous solvent or diluent, wherein the non-aqueous solvent or diluent comprises a carbonate. Suitably, the carbonate may be a fluorinated carbonate. Suitably, the lithium-ion cell may comprise a non-aqueous solvent or diluent, wherein the non-aqueous solvent or diluent comprises a compound comprising an ether group.

[0143] The present invention also relates to a battery comprising the anode according to the invention or the lithium-ion cell according to the disclosure. In the context of the present disclosure a battery may contain one or more anodes or one or more lithium-ion cells. Suitably, the one or more anodes or lithium-ion cells according to the disclosure may be folded or rolled to obtain a suitable configuration for use in a battery.

[0144] Advantageously, the battery according to the disclosure may suitably have the electrolyte, cathode, separator, and anode in a rolled or folded configuration or contained within a non-metallic pouch.

[0145] Suitably, the battery may be a cylindrical, prismatic, pouch or coin battery. Several configurations of lithium-ion cells can also be combined in a battery. For example, a coin cell can have an internal cylindrical configuration (as disclosed in international patent application WO2015188959A1) or a pouch cell can have an internal prismatic configuration.

[0146] Suitably, the battery may comprise a non-aqueous solvent or diluent, wherein the non-aqueous solvent or diluent comprises a carbonate. Suitably, the carbonate may be a fluorinated carbonate. Suitably, the battery may comprise a non-aqueous solvent or diluent, wherein the non-aqueous solvent or diluent comprises a compound comprising an ether group.

[0147] Suitably, the lithium-ion cell or battery according to the disclosure additionally may comprise an electrode tab. Suitably, the electrode tab may comprise nickel or copper, or an alloy comprising nickel, copper, tin, silicon, copper and nickel, copper and tin, or copper and silicon. Preferably, the tab material may comprise nickel.

[0148] Suitably, the tab may be a sheet-like material comprising a metal with a thickness of from 1 pm to 1 mm. Suitably, the tab may be a sheet-like material comprising a metal with a thickness of from 10 to 500 pm, of from 20 to 200 pm, of from 50 to 150 pm, or about 100 pm.

[0149] Another aspect of the disclosure is the use of the anode according to the invention in a lithium-ion cell or for the manufacture of a lithium-ion cell. Another aspect of the disclosure is the use of the anode according to the invention in a battery or for the manufacture of a battery.

[0150] An additional aspect of the disclosure is the use of the anode, the lithium-ion cell, or the battery according to the disclosure as an energy storage and / or release device or for the manufacture of an energy storage and / or release device. The term “energy storage and / or release device” herein is understood to mean a secondary battery, including an electrode assembly of a cathode / separator / anode structure mounted in a suitable battery case. Such batteries include lithium-ion secondary batteries, which excel in providing high energy density, and a high capacity; and their use in secondary battery modules comprising a plurality of secondary batteries, which are typically connected in series with each other to form a battery pack that can be incorporated into a casing to form the module.

[0151] Methods of preparing anodes and lithium-ion cells

[0152] An anode according to the invention or a lithium-ion cell or battery according to the disclosure may be prepared by various methods.

[0153] The present disclosure also relates to a method of preparing an (pristine) anode, the method comprising: a. providing a current collector; b. depositing active material comprising silicon on the current collector; c. forming regions surrounded by gaps in the active material; i. wherein the regions comprise sloped lateral surfaces; ii. wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and ill. wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode.

[0154] Step b of depositing active material comprising silicon on the current collector may be performed by various methods and materials known in the art. Suitably, depositing active material comprising silicon may comprise depositing a slurry comprising the active material, or slurry coating the active material or a composition comprising the active material; and optionally drying the slurry. Suitably, depositing active material comprising silicon may comprise using physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0155] Step c of forming the regions surrounded by gaps may be performed by various methods known in the art. For example, some of the active material may be removed such that the desired configuration according to the invention is formed. The skilled person can select suitable means and materials known in the art to achieve this. An exemplary method of removing active material may be etching. Suitably, the etching may be chemical etching or milling, optionally including masking, or laser etching. Yet, it is preferred that step c of forming the regions surrounded by gaps is performed during lithiation and de-lithiation. It was surprisingly found by the applicant that it is possible to manipulate the formation of the regions and gaps. By changing the process conditions of the lithiation and de- lithiation, and in particular by changing the pressure and / or temperature it was found possible to achieve the desired characteristics. This is beneficial as this allows to eliminate an entire process step of etching, milling, masking, or laser etching from the process flow.

[0156] The present disclosure also relates to a method of preparing a lithium-ion cell, the method comprising: a. providing the anode prepared according to the method of the disclosure, a cathode, and an electrolyte comprising lithium; b. combining the anode, the cathode, and the electrolyte to form a lithium-ion cell; c. lithiating the anode; and d. delithiating the anode; optionally repeating the lithiating and delithiating at least once.

[0157] The present disclosure also relates to a method of preparing a lithium-ion cell, the method comprising: a. providing an anode, comprising providing a current collector and depositing active material comprising silicon on the current collector; b. providing the anode, a cathode, and an electrolyte comprising lithium; c. combining the anode, the cathode, and the electrolyte to form a lithium- ion cell; d. lithiating the anode; and e. delithiating the anode to form regions; i. wherein the regions are surrounded by gaps; ii. wherein the regions comprise sloped lateral surfaces; ill. wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and iv. wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode; and optionally repeating the lithiating and delithiating at least once.

[0158] The present disclosure also relates to a method of preparing a lithium-ion cell, the method comprising: a. providing an anode, comprising providing a current collector, depositing active material comprising silicon on the current collector, and forming a plurality of columnar structures comprising silicon; b. providing the anode, a cathode, and an electrolyte comprising lithium; c. combining the anode, the cathode, and the electrolyte to form a lithium- ion cell; d. lithiating the anode; and e. delithiating the anode to connect the columnar structures and to form regions comprising the columnar structures; i. wherein the regions are surrounded by gaps; ii. wherein the regions comprise sloped lateral surfaces; ill. wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and iv. wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode; and optionally repeating the lithiating and delithiating at least once.

[0159] The above methods may be used to create the anode according to the invention and / or the lithium-ion cell according to the disclosure. The anode comprised in the lithium-ion cell as prepared according to the method of the disclosure results in the specific configuration of an anode according to the invention with sloped lateral surfaces separated by a gap, providing a lithium-ion cell with high cycle life and a high capacity.

[0160] Suitably, the active material may be deposited as a layer. The skilled person may suitably provide multiple anodes and / or cathodes to prepare multiple lithium-ion cells, which may for example then be combined into a battery.

[0161] Suitably, the method of preparing a lithium-ion cell may further comprise, in addition to providing an anode, a cathode, and electrolyte, providing a separator; and combining the anode, the cathode, the separator, and the electrolyte to form a lithium-ion cell.

[0162] Combining an anode, a cathode, an electrolyte, and suitably a separator, to form a lithium-ion cell is well-known in the art. Suitably, combining the anode, the cathode, the separator, and the electrolyte to form a lithium-ion cell may comprise placing the separator onto the active material of the anode; placing a cathode onto the separator to form a stack; connecting the cathode and anode to electrode tabs; inserting the stack of the anode, separator, and cathode into a cell housing; adding the electrolyte; and sealing the cell housing so as to prevent the electrolyte being able to leave the cell housing. Suitably, the cell housing may be a pouch.

[0163] In the context of the present aspect of the disclosure: the anode; the separator; the cathode; and the electrolyte may be as described in any previous aspect or specific embodiment above.

[0164] In an embodiment, advantageously the anode may be one wherein the adjacent columnar structures are elongated in the perpendicular direction to the current collector plane. Such a morphology allows for greater freedom to the columns to expand or contract laterally with respect to the direction perpendicular to the current collector layer.

[0165] It was found that particular properties of the silicon may further increase the advantageous configuration of the anode according to the invention, specifically with regard to the V-shape of the lateral surfaces of the regions, the gap area, and the top surface area of the regions according to the present invention. For example, without being bound to theory, it is thought that the mass loading of the silicon on the current collector and the porosity of the silicon may affect the number of lithium ions that can interact with silicon atoms (per gram silicon), also known in the art as silicon utilization, which plays an important role in the reactions during lithiation- delithiation of the active material and resultant formation of the anode according to the invention. Furthermore, the porosity of the silicon may affect the formation of the V-shape of the lateral surfaces of the regions, the gap area, and the top surface area of the regions according to the present invention.

[0166] By controlling the depositing of active material comprising silicon on the current collector different characteristics of an anode according to the invention may be obtained. Suitably, the active material may have a silicon mass load of at least 1 mg / cm2. Suitably, the active material may have a silicon mass load of at least 1.2 mg / cm2or 1.3 mg / cm2. Suitably, the active material may have a silicon mass load of from 1 mg / cm2to 10 mg / cm2. Suitably, the active material may have a silicon mass load of from 1 mg / cm2to 3 mg / cm2or 5 mg / cm2. Suitably, the active material may have a silicon mass load of from 1 .2 mg / cm2to 3 mg / cm2, 5 mg / cm2, or 10 mg / cm2. Suitably, the active material may have a silicon mass load of from 1.3 mg / cm2to 3 mg / cm2, 5 mg / cm2, or 10 mg / cm2.

[0167] Preferably, the active material may have a porosity of less than 50%. Suitably, the active material may have a porosity of less than 30%. Suitably, the active material may have a porosity of from 1% to 30%.

[0168] Preferably, the porosity may be determined by the Barrett-Joyner-Halenda method pursuant to ISO 15901-2:2006. Gas accessible porosity and (average) pore size of the material according to the disclosure may be preferably determined according to the method specified by the ISO (International Organization for Standardization) standard: ISO 15901-2:2006 “Pore size distribution and porosity of solid materials by mercury porosimetry and gas adsorption — Part 2: Analysis of mesopores and macropores by gas adsorption” using nitrogen gas. Briefly, a N2adsorption-isotherm is measured at about -196 °C (liquid nitrogen temperature). According to the calculation method of Barrett-Joyner-Halenda (Barrett, E. P.; Joyner, L.G.; Halenda, P. P. (1951 ), “The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations from Nitrogen Isotherms”, Journal of the American Chemical Society, 73 (1): 373-380) the pore size and pore volume can be determined. The calculation method is well-known in the art. A brief experimental test method to determine the isotherm can be described as follows: a test sample is dried at a high temperature and under an inert atmosphere. The sample is then placed in the measuring apparatus. Next, the sample is brought under vacuum and cooled using liquid nitrogen. The sample is held at liquid nitrogen temperature during recording of the isotherm. Suitably, the layer comprising active material comprising silicon may have a thickness of from 5 pm to 20 pm. Suitably, the layer comprising active material comprising silicon may have a thickness of from 5 pm to 15 pm, or of from 8 pm to 20 pm.

[0169] Suitably, the silicon may comprise amorphous silicon, optionally further comprising nano-crystalline silicon. Suitably, the amorphous silicon and / or nanocrystalline silicon may optionally further comprise silicon-containing compounds. A silicon-containing compound may be a compound comprising a silicon atom bound to another atom different from silicon. Suitably, the active material may have an amorphous structure, optionally wherein the amorphous structure has nanocrystalline regions.

[0170] Suitably, the current collector may comprise copper, aluminium, nickel, titanium, carbon, iron, chromium, stainless steel, or an alloy thereof. Preferably, the current collector comprises copper, nickel, or an alloy thereof. More preferably, the current collector comprises copper or an alloy thereof. More preferably, the current collector comprises copper.

[0171] Preferably, the current collector may have a thickness of from 5 pm to 20 pm.

[0172] Suitably, the current collector may have an ultimate tensile strength of at least 100 MPa. Suitably, the current collector may have an ultimate tensile strength of at least 150 MPa, at least 200 MPa, at least 220 MPa, at least 250 MPa, at least 260 MPa, at least 270 MPa, at least 280 MPa, or at least 290 MPa. Suitably, the current collector may have an ultimate tensile strength of from 100 MPa to 1000 MPa, of from 100 MPa to 500 MPa, of from 150 MPa to 1000 MPa, of from 150 MPa to 500 MPa, of from 200 MPa to 1000 MPa, of from 200 MPa to 500 MPa, of from 250 MPa to 1000 MPa, of from 250 MPa to 500 MPa, or of from 250 MPa to 480 MPa.

[0173] Suitably, the current collector may have a yield strength of at least 50 MPa. Suitably, the current collector may have a yield strength of at least 80 MPa, at least 90 MPa, at least 100 MPa, at least 110 MPa, at least 120 MPa, at least 130 MPa, at least 140 MPa, or at least 150 MPa. Suitably, the current collector may have a yield strength of from 50 MPa to 500 MPa, of from 50 MPa to 250 MPa, of from 80 MPa to 500 MPa, of from 80 MPa to 250 MPa, of from 100 MPa to 500 MPa, of from 100 MPa to 250 MPa, of from 120 MPa to 500 MPa, or of from 120 MPa to 250 MPa.

[0174] Preferably, the current collector may be roughened. Suitably, the current collector may comprise nodules. Suitably, the nodules have been formed using electrodeposition or electroplating.

[0175] Suitably, the current collector may exhibit a surface roughness value selected from at least one of the following: an Sdr value of at least 40%; an Sz value of at least 4 pm; an Sq value of at least 0.43 pm; and an Sa value of at least 0.2 pm; or any combination thereof. Suitably, the current collector may exhibit a surface roughness having an Sdr value of at least 40%, an Sz value of at least 4 pm, an Sq value of at least 0.43 pm, and an Sa value of at least 0.2 pm.

[0176] Suitably, the Sdr value may be at least 50%, at least 60%, at least 75%, at least 90%, at least 92%, at least 95%, at least 120%, at least 135%, at least 150%, or at least 160%. Suitably, the Sdr value may be of from 40% to 250%, of from 50% to 250%, of from 60% to 250%, of from 90% to 250%, of from 120% to 250%, of from 135% to 250%, of from 150% to 250%, or of from 160% to 250%. Suitably, the Sdr value may be of from 40% to 500%, of from 50% to 500%, of from 60% to 500%, of from 90% to 500%, of from 120% to 500%, of from 135% to 500%, of from 150% to 500%, or of from 160% to 500%.

[0177] Suitably, the Sz value may be at least 4.5 pm, at least 4.7 pm, at least 5 pm, at least 5.5 pm, at least 6 pm, at least 7.5 pm, or at least 8 pm. Suitably, the Sz value may be of from 4 pm to 14 pm, of from 4.5 pm to 14 pm, of from 4.7 pm to 14 pm of from 5 pm to 14 pm, of from 5.5 pm to 14 pm, of from 6 pm to 14 pm, of from 7.5 pm to 14 pm, or of from 8 pm to 14 pm.

[0178] Suitably, the Sq value may be at least 0.45 pm, at least 0.5 pm, at least 0.55 pm, at least 0.6 pm, at least 0.7 pm, at least 0.8 pm, or at least 0.85 pm. Suitably, the Sq value may be of from 0.43 pm to 2.5 pm, of from 0.45 pm to 2.5 pm, of from 0.5 pm to 2.5 pm, of from 0.55 pm to 2.5 pm, of from 0.6 pm to 2.5 pm, of from 0.7 pm to 2.5 pm, of from 0.8 pm to 2.5 pm, or of from 0.85 pm to 2.5 pm.

[0179] Suitably, the Sa value may be at least 0.3 pm, at least 0.35 pm, at least 0.4 pm, at least 0.45 pm, or at least 0.65 pm. Suitably, the Sa value may be of from 0.2 pm to 0.9 pm, of from 0.3 pm to 0.9 pm, of from 0.35 pm to 1 pm, of from 0.4 pm to

[0180] 1 pm, or of from 0.65 pm to 1 pm. Suitably, the Sa value may be of from 0.2 pm to

[0181] 2 pm, of from 0.3 pm to 2 pm, of from 0.35 pm to 2 pm, of from 0.4 pm to 2 pm, or of from 0.65 pm to 2 pm. In one embodiment the current collector may exhibit a surface roughness having an Sdr value of at least 100%, an Sa value of at least 0.4 gm, an Sq value of at least 0.5 gm, and an Sz value of at least 4.5 gm.

[0182] Advantageously, according to the method of the disclosure, the method may comprise, prior to providing the current collector, a step of adding an adhesion layer to the current collector.

[0183] Suitably, depositing active material comprising silicon on the current collector may comprise controlling the mixture, flow rate and / or pressure of an operating gas comprising a precursor gas comprising silicon.

[0184] By controlling various parameters such as mixing ratio, flow rate and / or pressure of an operating gas comprising a precursor gas comprising silicon to different predetermined values different silicon layers with different structures and properties can be obtained when depositing the silicon active material on the current collector.

[0185] During the formation process, small clusters of amorphous silicon may be typically formed by gas phase reaction. The silicon is deposited with a process called ballistic growth, in which particles move towards the substrate and adhere to it.

[0186] During the formation process, columnar structures may extend essentially perpendicularly to a surface of the current collector. The plurality of silicon columnar structures is arranged adjacent to each other.

[0187] Suitably, the operating gas may comprise a gas selected from: monosilane, disilane, trisilane, and chlorosilanes.

[0188] Suitably, the operating gas may comprise an alloying compound, for forming a silicon alloy.

[0189] Suitably, the operating gas may comprise a support gas comprising argon, helium, molecular nitrogen and / or molecular hydrogen.

[0190] Suitably, controlling the mixture, flow rate and / or pressure of an operating gas according to the disclosure advantageously may comprise controlling the ratio of the precursor gas to the support gas of from 0.05:1 to 5:1 , advantageously wherein the concentration molecular hydrogen in the support gas is of from 5 to 95% (mol / mol). Suitably, controlling the mixture, flow rate and / or pressure of an operating gas according to the disclosure may comprise controlling the pressure of from 0.05 to 0.3 mbar.

[0191] Suitably, controlling the power input and / or frequency according to the disclosure may comprise controlling the power input with a power of from 800 to 6000 W or of from 800 to 6000 W / m. An antenna wire with a length of 1 m, which is used as a means or source of power, is thus controlled with regard to power input by providing power of from 800 to 6000 W. A deposition tool can have one or more antennas, each having their own supply of microwave power.

[0192] Suitably, controlling the power input and / or frequency according to the disclosure may comprise controlling the frequency with a frequency of from 300 MHz to 30 GHz, preferably with a frequency of about 915 MHz, about 2.45 GHz, or about 5.8 GHz. Suitably, the frequency may comprise a frequency in the range of the C, L, or S bands as set according to the Institute of Electrical and Electronics Engineers. Suitably, the frequency may be of from 2.3 to 2.6 GHz.

[0193] Suitably, active material comprising silicon according to the method of the disclosure may comprise depositing silicon at a substrate temperature of from 10 °C to 300 °C. Suitably, the substrate temperature may be of from 25 °C to 300 °C, of from 120 °C to 300 °C, or of from 120 °C to 200 °C.

[0194] Preferably, depositing active material comprising silicon according to the method of the disclosure may comprise using physical vapor deposition (PVD) or chemical vapor deposition (CVD). More preferably, depositing active material comprising silicon may comprise using plasma-enhanced CVD (PECVD). In an embodiment, advantageously using PECVD comprises creating plasma by generating electromagnetic waves via an antenna wire, preferably wherein each end of the antenna wire may be coupled to a generator configured to generate electromagnetic waves.

[0195] Different types of electrolytes suitable to use in the present disclosure are known to the skilled person and are commercially available.

[0196] Suitably, the electrolyte may comprise a medium and a lithium salt. Suitably, the medium may be liquid or solid. Suitably, the medium may comprise other additives. Suitably, the medium may comprise a non-aqueous solvent. Suitably, the medium may comprise a diluent. Suitably, the electrolyte may be solid such as a ceramic electrolyte, a polymer, or a gel. The lithium salt in a solid ceramic electrolyte is usually present as a lithium metal oxide. Examples of solid ceramic electrolytes are lithium super ion conductors, argyrodites, sulfide solid electrolytes, and perovskites optionally arranged as an amorphous structure.

[0197] Suitably, the electrolyte may comprise a lithium salt. The lithium salt, or combination of lithium salts, participates in the cell’s charge and discharge processes. Lithium salts suitable to use in the present disclosure are known to the skilled person and are commercially available.

[0198] Suitably, the electrolyte may comprise a non-aqueous solvent. Suitably, the non-aqueous solvent may be selected such that the lithium salt has a solubility in the selected solvent of from 0.5 M (mole / dm3) to 5 M at 25 °C and 1 atm.

[0199] Suitably, the non-aqueous solvent may be selected from a nonaqueous solvent comprising at least one of the following components (i) an ester, (ii) a sulfur-containing solvent, (iii) a phosphorus-containing solvent, (iv) an ether, (v) a nitrile, or (vi) any combination thereof.

[0200] Suitably, the non-aqueous solvent may comprise a carbonate and / or an ether.

[0201] Suitably, the carbonate may be selected from: diethyl carbonate (DEC); difluoroethylene carbonate (DFEC); dimethyl carbonate (DMC); ethyl methyl carbonate (EMC); ethylene carbonate (EC); methyl 2, 2, 2, -trifluoroethyl carbonate (MFEC); propylene carbonate (PC); trifluoroethylene carbonate (TFEC); trifluoropropylene carbonate (TFPC); or any combination thereof.

[0202] Suitably, the ether may be selected from: 1 ,2-dimethoxyethane (DME); diethylene glycol dimethyl ether (diglyme, DEGDME); triethylene glycol dimethyl ether (triglyme); tetraethylene glycol dimethyl ether (tetraglyme); 1 ,3-dioxolane (DOL); allyl ether; or any combination thereof.

[0203] Suitably, the electrolyte may comprise a diluent. The diluent may be advantageously selected such that the lithium salt has a solubility in the selected solvent of less than 0.3 M (mole / dm3) at 25 °C and 1 atm. Suitably, the diluent may be selected such that the lithium salt has a solubility in the selected diluent of less than 0.2 M, preferably of less than 0.1 M, more preferably of less than 0.05 M or of less than 0.01 M at 25 °C and 1 atm. Suitably, the diluent may be selected from a diluent comprising one or more of: a fluoroalkyl ether; a fluorinated orthoformate, a fluorinated carbonate, a fluorinated borate; or a combination thereof.

[0204] Suitably, the diluent may be selected from: a fluoroalkyl ether; a fluorinated orthoformate, a fluorinated carbonate, a fluorinated borate; or a combination thereof.

[0205] Suitably, the electrolyte additionally may comprise an additive. The additive has a different composition than: (i) the lithium salt; (ii) the solvent; and (iii) the diluent. Optionally, the additive may be a flame retardant.

[0206] Suitably, the additive may comprise: 4-Fluoro-1 ,3-dioxolan-2-one (FEC, CAS: 114435-02-8), 1 ,3-Dioxol-2-one (VC, vinylene carbonate, CAS: 872-36-6), 1 ,4-Dicyanobutane, (adiponitrile, CAS: 111 -69-3), Lithium difluorophosphate (LiDFP), 4,5-dimethylene-1 ,3-dioxolan-2-one; 1 ,3,2-dioxathiolane-2-oxide (CAS: 3741-38-6); 1 ,3,2-dioxathiolane-2,2-dioxide(CAS: 1072-53-3); 1 ,3,2-dioxathiane- 2,2-dioxide (DTD, CAS: 1072-53-3); 3-methyl-1 ,4,2-dixoazol-5-one (CAS: 854849- 14-2); Tris(2,2,2-trifluoroehtyl)phosphite (TTFEPi, CAS: 370-69-4); 1 ,3,2- Dioxathiane 2-oxide (CAS: 4176-55-0); 1 -methylsulfonylethene (CAS: 3680-02-2); 1 -ethenylsulfonylethene (CAS: 77-77-0); or any combination thereof.

[0207] The shape of the regions may be suitably configured by charging the lithium-ion cell to a certain voltage or series of voltages during the first, and optionally the second, lithiation of the anode. The mean top surface area of the regions and the gap area percentage may suitably be configured in particular by the charging and discharging protocol.

[0208] Preferably, lithiating the anode may comprise charging the lithium-ion cell from approximately 0.2 V, preferably 1.0 V to 5.0 V, preferably 2.0 V to 4.2 V, wherein the upper boundary may be adjusted according to the cathode that is used. Preferably, lithiating the anode may comprise charging the lithium-ion cell to at least 3.8 V. Suitably, lithiating the anode may comprise charging the lithium-ion cell to at least 3.7 V, at least 3.75 V, at least 3.8 V, at least 3.85 V, at least 3.9 V, at least 3.95 V, at least 4.0 V, at least 4.05 V, at least 4.1 V, at least 4.15 V, or at least 4.2 V. The charging during lithiation may be situated between a charge rate of 0.01 C to 5.0 C, however preferably the charge rate is 0.1 C. The temperature during the charging is preferably situated between 10°C - 70°C, preferably the temperature is 30 °C. The pressure during discharging may be situated between 10 Bar and 1000 Bar, preferably the pressure is 100 Bar. Instead of Bar, it is imaginable that the expression of kg / cm2 is used. For which for example 90 kg / cm2 is an imaginable pressure. The values of pressure can be converted from Bar to kg / cm2, wherein 1 bar equals approximately 1 .01972 kg / cm2.

[0209] Suitably, lithiating the anode may comprise charging the lithium-ion cell to at least 3.6 V at a silicon utilization of at least 1000 mAh / g. Suitably, lithiating the anode may comprise charging the lithium-ion cell to at least 3.8 V at a silicon utilization of at least 1500 mAh / g. Suitably, lithiating the anode may comprise charging the lithium-ion cell to at least 4.0 V at a silicon utilization of at least 2000 mAh / g. Suitably, lithiating the anode may comprise charging the lithium-ion cell to at least 4.2 V at a silicon utilization of at least 2500 mAh / g.

[0210] The shape of the regions may be suitably configured or altered during the formation step, preferably during the formation step, in particular (the first) charging and / or discharging, the lithium-ion cell to a certain voltage or series of voltages during the first, and optionally the second, lithiation and / or delithiation of the anode. The mean top surface area of the regions and the gap area percentage may suitably be configured in particular by the formation protocol.

[0211] Preferably, delithiating the anode may comprise discharging the lithium-ion cell from approximately 5.0 V to 2.0 V, preferably 4.2 V to 2.5 V, wherein the upper boundary of 4.2 V may be adjusted according to the cathode that is used. The discharging during delithiation may be situated between a discharge rate of 0.01 C to 5.0 C, however preferably the discharge rate is 0.1 C. The temperature during the discharging is preferably situated between 10°C - 70°C, preferably the temperature is 30 °C. The pressure during discharging may be situated between 10 Bar and 1000 Bar, preferably the pressure is 100 Bar.

[0212] Suitably, during step d of lithiating the anode, the cell is charged from approximately 0.2 V, preferably 1 .0 V to 5.0 V, preferably 1 .0 V to 4.2 V. Suitably, during step d of lithiating the anode, a charge rate situated between 0.001 C to 5.0 C, preferably 0.1C. Suitably, during step d of lithiating the anode, a temperature situated between 10 degrees Celsius to 70 degrees Celsius, preferably between 30 degrees Celsius to 45 degrees Celsius. Suitably, during step d of lithiating the anode, a pressure is situated between 0 Bar and 5000 Bar, preferably between 10 Bar to 1000 Bar, preferably approximately 100 bar. Suitably, during step e of delithiating the anode, the cell is discharged of from approximately 5.0 V to 2.0 V, preferably 4.2 V to 2.5 V. Suitably, during step e of delithiating the anode, a charge rate situated between 0.001 C to 5.0 C, preferably 0.1 C. Suitably, during step e of delithiating the anode, a temperature situated between 10 degrees Celsius to 70 degrees Celsius, preferably between 30 degrees Celsius to 45 degrees Celsius. Suitably, during step e of delithiating the anode, a pressure is situated between 0 Bar and 5000 Bar, preferably between 10 Bar to 1000 Bar, preferably approximately 100 bar. Suitably, the method comprises the step of increasing the mean top surface area by lowering the pressure during the formation cycle, preferably the discharge of the formation cycle. Suitably, the method comprises the step of reducing the gap area % by lowering the pressure during the formation cycle, preferably the discharge of the formation cycle. Suitably, the method comprises the step of decreasing the mean top surface area by increasing the temperature during the formation cycle. Suitably, the method comprises the step of increasing the gap area % by increasing the temperature during formation.

[0213] Suitably, the method comprises the step of increasing the mean top surface area by increasing the C-rate during the formation cycle.

[0214] As disclosed above, without being bound to theory, it is thought that, in the present disclosure, the first cycle of lithiation and delithiation causes reactions that alter the structure of pristine silicon on a current collector such that regions appear that are surrounded by gaps, wherein part of the silicon in the regions is joined together. It seems that the formation temperature is related to gap area, increasing the temperature increases the gap area. Similarly, the pressure seems to be correlated predominantly to the mean top surface area. Particularly when reducing the pressure during the formation discharge the cluster size or mean top surface area is increased. The gap area is only marginally effected by reducing the pressure in the discharge of formation. It was also found that an increase in temperature during formation, for example raising the temperature from 30 degrees Celsius to 45 degrees Celsius was found to increase the gap area, whilst only marginally affecting the cluster size. Finally, it was found that the charge and / or discharge rate during formation influences predominantly the mean top surface area.

[0215] Suitably, delithiating the anode may comprise connecting the columnar structures via a solid electrolyte interphase (SEI). Suitably, delithiating the anode may comprise fusing parts of the columnar structures.

[0216] Suitably during step d of lithiating the anode, the cell is charged from approximately 0.2 V, preferably 1 .0 V to 5.0 V, preferably 1 .0 V to 4.2 V. Suitably, during step d of lithiating the anode, a charge rate situated between 0.001 C to 5.0 C, preferably 0.1C. Suitably, during step d of lithiating the anode, a temperature situated between 10 degrees Celsius to 70 degrees Celsius, preferably between 30 degrees Celsius to 45 degrees Celsius. Suitably, during step d of lithiating the anode, a pressure is situated between 10 Bar to 1000 Bar, preferably approximately 100 bar. Suitably, during step e of delithiating the anode, the cell is discharged of from approximately 5.0 V to 2.0 V, preferably 4.2 V to 2.5 V. Suitably, during step e of delithiating the anode, a charge rate situated between 0.001 C to 5.0 C, preferably 0.1C. Suitably, during step e of delithiating the anode, a temperature situated between 10 degrees Celsius to 70 degrees Celsius, preferably between 30 degrees Celsius to 45 degrees Celsius. Suitably, during step e of delithiating the anode, a pressure is situated between 10 Bar to 1000 Bar, preferably approximately 100 bar. It was surprisingly found that the formation cycle(s) influenced the shape and size of regions and gaps. That is, by subjecting the pristine anode in the cell to a formation cycle as defined in these conditions, the mean top surface area can be adjusted according to the need. This may be achieved by for example increasing the C-rate during formation or by decreasing pressure during formation discharge. The latter (i.e. reducing pressure) also reduces the gap area %. The gap area % may be increased by for example increasing the temperature during formation.

[0217] It was found that the formation conditions allow for changing the regions (701) and gaps (702), was will be shown based on Figure 7A, 7B, and 7C, with reference to the samples of Table 2. Figures 7A-7C each show a dashed line, which separates the results of a first sample from that of another sample. On the left side in each of the figures, the result of Sample 2-1 of Table 2 is depicted, which is a sample according to the invention using foil B. Sample 2-1 is considered the “base” example for comparison. In Figure 7A, Sample 2-1 is compared to Sample 2-2 as shown in Table 2. In sample 2-2 the pressure during the discharge step of the formation cycle is reduced, to a pressure of 0 kg / cm2, compared to a pressure of 90 kg / cm2 which is applied in the formation discharge for sample 2-1. All remaining conditions are kept the same. It was found that this yielded a substantially larger mean top surface area. The reduction of pressure in sample 2-2 also caused a slight reduction of the gap area %. Hence, without being bound to any theory, it is believed that reducing the pressure, at least in the formation discharge, causes an increase in mean top surface area and a reduction in the gap area%, although the effect on the mean top surface area is larger.

[0218] Figure 7B shows a comparison of Sample 2-1 with sample 2-3 of Table 2. For sample 2-3 the temperature during formation was increased from 30 degrees Celsius (for sample 2-1) to a temperature of 45 degrees Celsius. The increased temperature causes an increase of the gap area %, and a reduction in mean top surface area. Hence, without being bound to any theory, it is believed that increasing the temperature, at least during the formation, causes an increase in gap area % and a reduction in the mean top surface area.

[0219] Figure 7C shows a comparison between Sample 2-1 and sample 2-4 of Table 2. Sample 2-4 reflects a sample where during the formation a higher C-rate is chosen. Where sample 2-1 was subjected to formation with a C-rate of 0.1 , sample 2-4 was subjected to formation with a C-rate of 1 . It was observed that by increasing the C- rate of the formation process the mean top surface area increases. Also, albeit marginally, the gap area % increased during the higher C-rate of the formation.

[0220] Hence, without being bound to any theory, it is believed that increasing the C-rate, at least in the formation, causes an increase in mean top surface area and a marginal increase in the gap area %, although the effect on the mean top surface area is larger.

[0221] Suitably, depositing active material comprising silicon on the current collector may comprise forming a layer. Suitably, the layer may be continuous or discontinuous. The layer may comprise areas where the current collector surface is exposed to the gaps. Preferably, the area where the current collector surface is exposed to the gaps is minimal. Suitably, the active material may be arranged on both sides or only one side of the current collector.

[0222] Preferably, the sloped lateral surfaces may have an angle of from 40° to 85° to the current collector plane. Suitably, the sloped lateral surfaces may have an angle of from 50° to 85°, of from 60° to 85°, of from 40° to 80°, of from 50° to 80°, of from 60° to 80°, of from 40° to 75°, of from 50° to 75°, or of from 60° to 75° to the current collector plane.

[0223] Suitably, the sloped lateral surfaces may have an angle of from 40° to 85° to the top surface plane of the active material or the top surface plane of the anode. Suitably, the sloped lateral surfaces may have an angle of from 50° to 85°, of from 60° to 85°, of from 40° to 80°, of from 50° to 80°, of from 60° to 80°, of from 40° to 75°, of from 50° to 75°, or of from 60° to 75° to the top surface plane of the active material. Suitably, the sloped lateral surfaces may have an angle of from 50° to 85°, of from 60° to 85°, of from 40° to 80°, of from 50° to 80°, of from 60° to 80°, of from 40° to 75°, of from 50° to 75°, or of from 60° to 75° to the top surface plane of the anode.

[0224] Suitably, the sloped lateral surfaces may be converged near the current collector surface. Suitably, the sloped lateral surfaces may be converged near the current collector surface at an angle of from 5° to 50° to each other. Suitably, the sloped lateral surfaces may be converged near the current collector surface at an angle of from 5° to 40°, of from 5° to 30°, of from 10° to 50°, of from 10° to 40°, of from 10° to 30°, of from 15° to 50°, of from 15° to 40°, or of from 15° to 30°, to each other. Suitably, the sloped lateral surfaces may be joined near the current collector surface. Suitably, the sloped lateral surfaces may be joined near the current collector surface at an angle of from 5° to 50° to each other. Suitably, the sloped lateral surfaces may be joined near the current collector surface at an angle of from 5° to 40°, of from 5° to 30°, of from 10° to 50°, of from 10° to 40°, of from 10° to 30°, of from 15° to 50°, of from 15° to 40°, or of from 15° to 30°, to each other.

[0225] Preferably, near the current collector surface may be at the bottom 20% of the layer comprising active material. Suitably, near the current collector surface may be at the bottom 15% of the layer comprising active material.

[0226] Suitably, the regions may further comprise lateral surfaces having a substantially perpendicular angle to the current collector plane. Preferably, the substantially perpendicular angle to the current collector plane may be an angle of more than 85° and up to 90° to the current collector plane.

[0227] Suitably, the sloped lateral surfaces may be converged with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface.

[0228] Suitably, the sloped lateral surfaces may be converged with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface at an angle of from 5° to 50°. Suitably, the sloped lateral surfaces may be converged with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface at an angle of from 5° to 40°, of from 5° to 30°, of from 10° to 50°, of from 10° to 40°, of from 10° to 30°, of from 15° to 50°, of from 15° to 40°, or of from 15° to 30°. Suitably, the sloped lateral surfaces may be joined with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface. Suitably, the sloped lateral surfaces may be joined with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface at an angle of from 5° to 50°. Suitably, the sloped lateral surfaces may be joined with the lateral surfaces having a substantially perpendicular angle to the current collector plane near the current collector surface at an angle of from 5° to 40°, of from 5° to 30°, of from 10° to 50°, of from 10° to 40°, of from 10° to 30°, of from 15° to 50°, of from 15° to 40°, or of from 15° to 30°.

[0229] Preferably, near the current collector surface may be at the bottom 20% of the layer comprising active material. Suitably, near the current collector surface may be at the bottom 15% of the layer comprising active material.

[0230] Suitably, the lateral surfaces may extend substantially linearly. Suitably, the sloped lateral surfaces may extend substantially linearly.

[0231] Preferably, the sloped lateral surfaces may extend for a distance of at least 50% of the total thickness of the layer comprising active material. Suitably, the sloped lateral surfaces may extend for a distance of at least 60%, of at least 70%, or of at least 80% of the total thickness of the layer comprising active material. Suitably, the sloped lateral surfaces may extend for a distance of from 50% to 100% of the total thickness of the layer comprising active material. Suitably, the sloped lateral surfaces may extend for a distance of from 60% to 100%, of from 70% to 100%, or of from 80% to 100% of the total thickness of the layer comprising active material.

[0232] Suitably, the sloped lateral surfaces may extend from the current collector. Suitably, the sloped lateral surfaces may extend from near the current collector. Preferably, near the current collector surface may be at the bottom 20% of the layer comprising active material. Suitably, near the current collector surface may be at the bottom 15% of the layer comprising active material.

[0233] The orientation of the lateral surfaces as disclosed above can be determined from a cross-sectional electron microscope image of the anode with a SOC of 0% to 10% perpendicular to the plane of the current collector. The mean distance between the regions is greater at the top surface of the regions than near the current collector surface. Preferably, the mean distance between the regions may be the mean distance between the regions parallel to the current collector plane. Determination of the mean distance between the regions can be determined from a cross-sectional electron microscope image of the anode with a SOC of 0% to 10% perpendicular to the plane of the current collector.

[0234] Preferably, at the top surface may be at the top 5% of the top surface of the regions. Suitably, at the top surface may be at the top 3% or top 1% of the top surface of the regions. Preferably, near the current collector may be at the bottom 20% of the layer comprising active material. Suitably, near the current collector surface may be at the bottom 15% of the layer comprising active material.

[0235] Suitably, the mean distance at the top surface may be at least 110% of the mean distance near the current collector. Suitably, the mean distance at the top surface may be at least 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 250%, 300%, 350%, 400%, 450%, or 500% of the mean distance near the current collector.

[0236] Preferably, the mean distance between the regions may be at least 1 pm at the top surface of the regions. Preferably, the mean distance between the regions at the top surface of the regions may be the mean distance between the regions parallel to the current collector plane.

[0237] Suitably, the mean distance between the regions may be at least 2 pm or at least 3 pm at the top surface of the regions. Suitably, the mean distance between the regions may be of from 1 pm to 10 pm, of from 1 pm to 8 pm, of from 1 pm to 7 pm, of from 2 pm to 10 pm, of from 2 pm to 8 pm, of from 2 pm to 7 pm, of from 3 pm to 10 pm, of from 3 pm to 8 pm, or of from 3 pm to 7 pm, at the top surface of the regions.

[0238] Suitably, the distance between the regions may be of from 1 pm to 10 pm at the top surface of the regions. Preferably, the distance between the regions at the top surface of the regions may be the distance between the regions parallel to the current collector plane. Suitably, the distance between the regions may be of from 1 pm to 8 pm, of from 1 pm to 7 pm, of from 1 pm to 6 pm, of from 1 pm to 5 pm, of from 2 pm to 10 pm, of from 2 pm to 8 pm, of from 2 pm to 7 pm, of from 2 pm to 6 pm, of from 2 pm to 5 pm, of from 3 pm to 10 pm, of from 3 pm to 8 pm, or of from 3 pm to 7 pm, at the top surface of the regions. The gaps comprise an area of from 5% to 35% of the top surface area of the anode. Determination of the gap area percentage can be determined from a top- down electron microscope image of the anode with a SOC of 0% to 10%. The area of the gaps is a percentage of the total two-dimensional area of the top-down electron microscope image. Hence, any surface area increases due to irregularities of the shape of the top surface of the active material layer are not taken into account. Suitably, the gaps comprise an area of from 8% to 35%, of from 10% to 35%, of from 12% to 35%, of from 15% to 35%, of from 17% to 35%, of from 20% to 35%, of from 22% to 35%, or from 24% to 35% of the top surface area of the anode. Suitably, the gaps comprise of from 8% to 30%, of from 10% to 30%, of from 12% to 30%, of from 15% to 30%, of from 17% to 30%, of from 20% to 30%, of from 22% to 30%, or from 24% to 30% of the top surface area of the anode. Preferably, the gaps comprise an area of from 18% to 35%, of from 19% to 35%, of from 20% to 35%, of from 18% to 30%, of from 19% to 30%, of from 20% to 30%, or from 22% to 30% of the top surface area of the anode.

[0239] Preferably, the regions may have a mean top surface area of at least 150 pm2. Suitably, the regions may have a mean top surface area of at least 160 pm2, at least 170 pm2, at least 180 pm2, at least 190 pm2, at least 200 pm2, at least 210 pm2, at least 220 pm2, at least 230 pm2, at least 240 pm2, or at least 250 pm2. Determination of the mean top surface area of the regions can be determined from a top-down electron microscope image of the anode with a SOC of 0% to 10%. The mean top surface area of the regions is a two-dimensional area as determined from the top-down electron microscope image. Hence, any surface area increases due to irregularities of the shape of the top surface of the active material layer are not taken into account.

[0240] Suitably, the regions may have a mean top surface area of from 150 pm2to 1500 pm2. Suitably, the regions may have a mean top surface area of from 150 pm2to 1200 pm2, of from 150 pm2to 1250 pm2, of from 150 pm2to 1000 pm2, of from 150 pm2to 800 pm2, of from 150 pm2to 700 pm2, of from 150 pm2to 600 pm2, of from 150 pm2to 500 pm2, or of from 150 pm2to 400 pm2. Suitably, the regions may have a mean top surface area of from 170 pm2to 1200 pm2, of from 170 pm2to 1250 pm2, of from 170 pm2to 1000 pm2, of from 170 pm2to 800 pm2, of from 170 pm2to 700 pm2, of from 170 pm2to 600 pm2, of from 170 pm2to 500 pm2, or of from 170 pm2to 400 pm2. Suitably, the regions may have a mean top surface area of from 200 pm2to 1200 pm2, of from 200 urn2to 1250 urn2, of from 200 urn2to 1000 |jm2, of from 200 urn2to 800 urn2, of from 200 urn2to 700 urn2, of from 200 |jm2to 600 urn2, of from 200 urn2to 500 urn2, or of from 200 urn2to 400 urn2. Suitably, the regions may have a mean top surface area of from 220 pm2to 1200 pm2, of from 220 pm2to 1250 pm2, of from 220 pm2to 1000 pm2, of from 220 pm2to 800 pm2, of from 220 pm2to 700 pm2, of from 220 pm2to 600 pm2, of from 220 pm2to 500 pm2, or of from 220 pm2to 400 pm2. Preferably, the regions may have a mean top surface area of from 150 pm2to 872 pm2, of from 150 pm2to 870 pm2, of from 150 pm2to 850 pm2, or of from 150 pm2to 800 pm2. Preferably, the regions may have a mean top surface area of from 290 pm2to 872 pm2, of from 290 pm2to 870 pm2, of from 290 pm2to 850 pm2, or of from 290 pm2to 800 pm2. Preferably, the regions may have a mean top surface area of from 295 pm2to 872 pm2, of from 295 pm2to 870 pm2, of from 295 pm2to 850 pm2, or of from 295 pm2to 800 pm2.

[0241] Suitably, at least 90% of the regions each may have a top surface area of at least 150 pm2. Suitably, at least 90% of the regions each may have a top surface area of at least 160 pm2, at least 170 pm2, at least 180 pm2, at least 190 pm2, at least 200 pm2, at least 210 pm2, at least 220 pm2, at least 230 pm2, at least 240 pm2, or at least 250 pm2.

[0242] Suitably, at least 90% of the regions each may have a top surface area of from 150 pm2to 600 pm2, of from 150 pm2to 500 pm2, or of from 150 pm2to 400 pm2. Suitably, at least 90% of the regions each may have a top surface area of from 170 pm2to 600 pm2, of from 170 pm2to 500 pm2, or of from 170 pm2to 400 pm2. Suitably, at least 90% of the regions each may have a top surface area of from 200 pm2to 600 pm2, of from 200 pm2to 500 pm2, or of from 200 pm2to 400 pm2. Suitably, at least 90% of the regions each may have a top surface area of from 220 pm2to 600 pm2, of from 220 pm2to 500 pm2, or of from 220 pm2to 400 pm2. Preferably, at least 90% of the regions each may have a top surface area of from 150 pm2to 872 pm2, of from 150 pm2to 870 pm2, of from 150 pm2to 850 pm2, or of from 150 pm2to 800 pm2. Preferably, at least 90% of the regions each may have a top surface area of from 290 pm2to 872 pm2, of from 290 pm2to 870 pm2, of from 290 pm2to 850 pm2, or of from 290 pm2to 800 pm2. Preferably, at least 90% of the regions each may have a top surface area of from 295 pm2to 872 pm2, of from 295 pm2to 870 pm2, of from 295 pm2to 850 pm2, or of from 295 pm2to 800 pm2. Preferably, the gaps may be contiguous. Suitably, the gaps may be interconnected. Preferably, the regions may have a polygonal shape. Suitably, each of the regions may have a substantially different polygonal shape.

[0243] Without being bound to theory, it is thought that, in the present disclosure, the first cycle of lithiation and delithiation causes reactions that alter the structure of pristine silicon of the anode layer comprising active material on a current collector such that regions appear that are surrounded by gaps, wherein part of the silicon-comprising material in the regions is joined together.

[0244] In one example according to the invention, pristine silicon may be deposited on a current collector such that columnar structures are formed. After the first cycle of lithiation and delithiation, some of the columnar structures may cluster and join together, while still being attached to the current collector, thereby resulting in the particular V-shape as disclosed above. Such columnar structures may therefore be particularly suitable for anodes according to the present invention, because the vertical structure of the columns may act as fracture points for formation of the regions surrounded by gaps.

[0245] Preferably, the regions may comprise columnar structures comprising silicon. Suitably, the columnar structures may extend in a substantially perpendicular direction from the surface plane of the current collector. The orientation of the columnar structures can be determined from a cross-sectional electron microscope image of the anode with a SOC of 0% to 10%, wherein the cross section is perpendicular to the plane of the current collector.

[0246] Suitably, at least 95% of the regions may comprise a plurality of interconnected or adjoined columnar structures comprising silicon. Suitably, at least 96%, at least 97%, at least 98%, at least 99%, about 100%, or substantially 100% of the regions may comprise a plurality of interconnected or adjoined columnar structures comprising silicon. Suitably, the columnar structures may extend in a substantially perpendicular direction from the surface plane of the current collector.

[0247] Suitably, the regions may comprise a solid electrolyte interphase (SEI) between the interconnected or adjoined columnar structures. Suitably, the interconnected or adjoined columnar structures may be directly connected. Suitably, the regions may comprise grain-like column boundaries between the interconnected or adjoined columnar structures. In an embodiment, advantageously the layer comprising active material may be one wherein the boundaries of the columnar structures resemble grain-like column boundaries, preferably the boundaries of the columnar structures of the regions may resemble grain-like column boundaries.

[0248] Definitions

[0249] As used herein, the singular terms "a", "an," and "the" include the plural reference unless the context clearly indicates otherwise. It is to be understood that this invention is not limited to the particular methodology, protocols, and reagents described, as these may vary, depending upon the context they are used by those of skill in the art.

[0250] As used herein, the term “substantially” refers to a great extent or degree. The exact allowable degree may depend on the specific context.

[0251] For example, the term “substantially” in the context of a substantially fully lithiated anode as disclosed herein would mean that the anode may comprise at least 90%, at least 95%, at least 97%, or at least 99%, of the maximum amount of lithium ions. A substantially fully delithiated anode as disclosed herein would mean that the anode may comprise at most 10%, at most 5%, at most 3%, or at most 1%, of the maximum amount of lithium ions.

[0252] For example, the term “substantially” in the context of a substantially perpendicular angle or direction as disclosed herein would mean that the substantial perpendicular angle or direction may comprise an angle or direction of from 85° to 90°, of more than 85° and up to 90°, of from 85.1 ° to 90°, of from 86° to 90°, of from 87° to 90°, or of from 88° to 90°.

[0253] As used herein, the term “cycle life” refers to the number of complete charge-discharge cycles a battery can perform before its capacity falls below 80% of its initial rated capacity.

[0254] Aspects of the invention are demonstrated by the following non-limiting examples. The invention is not limited to the examples, which merely serve to stipulate the advantages of the present invention. The preferred regions and gaps can be adjusted according to the preference by changing the current collector material and selecting formation conditions. Throughout this disclosure, the comparative samples and the samples according to the invention were produced based on different foils, types A and B respectively. The differences between the two foils can be, inter alia, characterized by roughness parameters as set out in the table below. Foil B may comprise nodules, which are arranged on at least one side of the foil layer. The Nodules may be seen in e.g., Figure 6B, indicated with reference 612.

[0255] Example 1

[0256] Preparation of pristine anode material and pouch lithium cell

[0257] A roll of roughened copper foil current collector material (Sa 0.3-0.9 pm, Sz 4.5-10 pm, and Sdr 120-250%, all as determined by standard method ISO 25178, and ultimate tensile strength 250-480 MPa) having a thickness of from 10 to 15 pm was fed into a plasma enhanced chemical vapour deposition (PECVD) device that comprises an unwinding chamber, two deposition chambers and a rewinding chamber. These chambers are all connected and are normally operated under vacuum (0.05-0.2 mbar). The foil was transported by a system of tension rolls and two heated drums that control the temperature of the foil. A first silicon layer was deposited onto the same side of the copper substrate by PECVD, at a substrate temperature of from 10 to 300 °C. In this process magnetron radiation with a frequency of 2.45 GHz was used to excite a gas mixture containing a silicon precursor gas and support gases. Silane (SiH4) was the source of silicon, whereas argon (Ar) and hydrogen (H2) were added to stabilize the plasma, influence the material structure and improve the deposition rate. The gas was injected via “gas showers” that distribute the gas evenly.

[0258] The magnetron (microwave) radiation was introduced into the vacuum chamber by means of an antenna. To ensure a homogeneous plasma, both sides of the antenna are connected to a magnetron radiation source. Magnetron heads are thus located on each side of the antenna. These magnetron heads are connected to the antenna. Gases are injected via the gas showers proximal to the magnetron heads. The antenna is protected from the reactive environment by a quartz tube. The plasma is confined by a magnetic field that is generated by an array of permanent magnets.

[0259] The production rate of silicon was determined by the process conditions, power input per source, and by the number of microwave sources in operation. The gas flow was scaled with the MW power input, which was 800-6000 W / m. Ten antennas or sources of power input were used.

[0260] Figure 6A is a representative top-down Scanning Electron Microscopy (SEM) image of the material obtained. Figure 6B is a representative cross-sectional SEM image of the material obtained. It was established that the deposited pristine silicon layer had a thickness of from 8 to 20 pm and the current collector had a thickness of from 10 to 15 pm. BJH analysis determined that the active material had a porosity of 0-50%.

[0261] Next, a pouch cell was built by stacking (i) the anode material as prepared above; (ii) as a ceramic separator, a 12 pm polymer polypropylene membrane coated on both sides with a 2 pm layer of alumina was employed, which was sourced from Gelon LIB Group, China; and (iii) as cathode material, a 2.5 or 3.5 mAh / cm2lithium nickel manganese cobalt oxide NMC 622 anode was employed which is commercially available from CUSTOMCELLS. Both the cathode and anode were connected to an external circuit by electrode tabs that were welded by conventional means to the electrodes by conventional means. The tabbed and stacked unit was pouched within a laminated aluminium pouching material, which was sealed on three sides. A suitable ether-based electrolyte was added to the laminated aluminium pouch under a dry atmosphere, and then vacuum sealed.

[0262] However, after building the cells and prior to cycling, the anodes are subjected to a formation step. A formation step is comparable to a regular cycle step (charge and discharge), but is performed under different conditions compared to regular cycle conditions during consumer usage. The formation cycles for the samples may have 2 cycles. A first charge between 0.2 V to 5.0 V, preferably between 1 .0 V or 2.0 V to 4.2 V with C-rate of 0.1 C. These initial cycles are called formation cycles. During the lithiation and de-lithiation the regions in active material are being formed.

[0263] Cells comprising anodes according to the invention prepared according to Example 1 as set out above and comparative cells comprising comparative anodes were evaluated for their cycle life / capacity retention properties. Here, cells comprising the comparative anodes relate to the anodes using foil layer A, whereas the cells according to the invention use foil layer B.

[0264] The cycling conditions used were C / 2 rate, 3 V to 4.2 V (Constant Voltage [CV] step at 4.2 V until C / 20 rate) at 25 °C. These cycling conditions relate to the postformation cycling conditions. Prior to subjecting the cells to a cycling condition, the cells are subjected to the formation process. The formation process is described below with respect to the second set of examples and Table 2.

[0265] The anodes were evaluated for their morphological properties at 0% state of charge (SOC) after two (e.g. see Figures 2, 3, and 5A) or 400 cycles (e.g. see Figure 5B). The lithium-ion cells were disassembled under inert conditions and analysed by Scanning Electron Microscopy (SEM). Representative SEM images of anodes according to the invention with typical V-shapes are reproduced in Figures 2, 3, and 5.

[0266] The presence or absence (respectively indicated by “+” or “-”) of a V-shape (V- shaped lateral surfaces according to the disclosure) in the anodes was assessed from representative cross-sectional SEM images taken after formation (i.e. after the first two cycles of lithiation-delithiation) at 0% SOC. Typical V-shapes scored as “+” of the above examples are shown in Figure 3, indicated by dashed ellipses.

[0267] The determination of V-shapes from cross-sectional SEM images was performed as follows. First, the distance between regions at the top surface was determined to be greater than the distance between the same regions near the current collector. At least one of the regions comprises a sloped lateral surface, in particular wherein the sloped lateral surface is at an angle of from 40° to 85° to the current collector plane. The distance between the regions typically becomes less from the top surface of the regions towards the current collector surface. Gap area percentage and mean top surface area were assessed from representative top-down SEM images taken after formation (i.e. after the first two cycles of lithiation-delithiation) at 0% SOC. Quantification was performed via the public domain Java image processing program Imaged using a custom algorithm for identifying gaps and regions. The gap area percentage was calculated by dividing the area identified as gaps from the total area of the image. For this study, the SEM images were taken using Hitachi SEM (type FlexSEM 1000 II), although the skilled person would be able to achieve similar SEM images based on other techniques. The magnification is set to 500, and may optionally be set to 1000. The acceleration voltage of 5 kV is applied. Using this equipment, the brightness and contrast is automatically calculated using the equipment software. In case other software is used, it may require an adjustment of brightness and contrast. The resulting image is cropped to remove artifacts, an contains over 500 K pixels. Based on the cropped image, the picture is converted into black-white colour tones only, to enhance contrast between gaps and regions. In the present study, the gaps are coloured in white, whereas the regions are coloured in the black. Using image analysis scripts, the surface area of white (or black) pixels can be determined. The gap area (%) is calculated by dividing the gap area (white pixels) by the total area (total amount of pixels). This way of analysing the anode structure can optionally also be used for determining the (mean) surface area of the regions, and / or determining the gap area %, and / or the mean distance between zones. The calculation of the mean region area or mean top surface area may also be determined by measuring the pixels in a black area (corresponding to a region). Knowing the total amount of pixels and scale, the area of each individual region can be determined in pm2. The mean value of all individual regions yields the mean top surface area. Hence, it is not necessarily the case that all regions are the same size, but some variation between regions is imaginable. The mean top surface area therefore reflects a kind of average size of the regions.

[0268] Duplicates of the lithium-ion cells as assessed above by SEM were assayed for capacity retention. The number of charge-discharge cycles when the lithium-ion cell reached 80% of its initial capacity was recorded.

[0269] Results are presented in Table 1 . Figure 4A shows representative results of a lithium-ion battery comprising an anode according to the invention (indicated by “X”) and a lithium-ion battery comprising an anode not according to the invention (indicated by “Y”). Here, for each example the foil type as outlined in the beginning of this section is indicated specifically. Table 1

[0270] As shown in Table 1 for Examples 1 -1 to 1 -8, 1 -11 , 1-12, and 1 -15 to 1-20, the presence of a V-shape of the lateral surfaces of the regions, capacity retention greater than 80% was maintained for more cycles. However, in Examples 1 -9, 1 - 10, 1 -13, and 1 -14 in which no V-shape of the lateral surfaces or gaps could be observed (e.g. the lateral surfaces of the regions were (substantially) perpendicular to the current collector plane), capacity retention greater than 80% was maintained for less cycles. It was in this respect thus observed that the foil layer A that was used for the comparative examples did not show presence of such V-shaped gaps. Therefore it is concluded that the foil layer B surface parameters allow for forming such beneficial V-shaped gaps.

[0271] As can be seen from Table 1 and Figure 4A, lithium-ion cells according to the disclosure can undergo at least 232 cycles before capacity retention falls to 80%. In contrast, lithium-ion cells comprising anodes without V-shaped lateral surfaces can only undergo at most 187 cycles before capacity retention falls to 80%.

[0272] The results demonstrated that lithium-ion cells according to the disclosure demonstrated that lithium-ion cells according to the present disclosure retained high capacity retention for significantly more charge cycles than the examples without V-shaped lateral surfaces.

[0273] Similar results were achieved by using a commercially available carbonate-based electrolyte. Figure 4B shows representative results of a lithium-ion cell comprising an anode according to the invention (indicated by “X”) and an anode not according to the invention having no V-shapes (indicated by “Y”), each cell comprising a commercially available carbonate-based electrolyte instead of an ether-based electrolyte. Absence of any V-shape clearly resulted in a lower number of cycles before capacity retention falls to 80% of initial capacity compared to the presence of V-shapes.

[0274] It was found that lithium-ion cells according to the invention comprising the carbonate-based electrolyte generally resulted in a similar relative increase in cycle life when compared to the ether-based electrolyte as used for Examples 1 -1 to 1 - 20. The V-shape is therefore beneficial for cycle life for both types of electrolytes. Hence, when using the anode according to the present invention the type of electrolyte does not seem to affect the increase in cycle life.

[0275] However, it was found that the rate capability of lithium-ion cells comprising an anode according to the invention and comprising a carbonate-based electrolyte was increased when compared to lithium-ion cells comprising an anode according to the invention and comprising an ether-based electrolyte.

[0276] Thus, lithium-ion cells according to the present disclosure demonstrate improved capacity retention, and hence cycle-life, compared to lithium-ion cells without V-shaped gaps or lateral surfaces. In addition to the presence or absence of the V-shaped gaps it was moreover surprisingly found that a smaller mean top surface area and relatively high gap area (%) can further improve the cycle life. In order to demonstrate how the mean top surface area can be influence, as well as the gap area Table 2 is included. According to a second set of examples, which are presented in Table 2 below, indicate under which conditions it was found to influence the mean top surface area and / or gap area. All cells in Table 2 were produced using foil type B as shown in Table 1 . Particularly the formation conditions, such as pressure, charge / discharge rate, and temperature were found to influence the results of top surface area and gap area. Due to extensive resource requirements only a selection of examples is provided below in Table 2. For example, but not being bound to any theory, it seems that not applying a pressure during formation discharge causes an increase in mean top surface area whilst keeping a somewhat similar gap area, at least in comparing cell numbers 2-1 and 2-2. Hence, lowering pressure increases the mean top surface area. Based on the examples 2-1 and 2-3 it is concluded that by increasing the temperature from 30 degrees Celsius to 45 degrees Celsius causes an increase in gap area. At the same time, the increased temperature causes a reduction in mean top surface area. When comparing examples 2-1 and 2-4, it is concluded that the influence on the C-rate during the first charge mainly influences mean top surface area. Increasing the C-rate during first charge increased the mean top surface area. The resulting gap area and mean top surface area as depicted in Table 2 were obtained by means of the same analysis as elaborated above, i.e., based on image analysis of a top view.

[0277] Table 2

Claims

Claims1 . An anode comprising: a. a current collector; b. a layer comprising active material comprising silicon on the current collector, wherein the layer comprises regions surrounded by gaps; wherein the regions comprise silicon; wherein the regions comprise sloped lateral surfaces; wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode.

2. The anode according to claim 1 , wherein the regions have a mean top surface area of at least 150 pm2.

3. The anode according to claim 1 or 2, wherein the regions have a mean top surface area of from 150 pm2to 500 pm2, or of from 150 pm2to 870 pm2.

4. The anode according to any one of claims 1 to 3, wherein the gaps comprise an area of from 12%, preferably 18%, to 35% of the top surface area of the anode.

5. The anode according to any one of claims 1 to 4, wherein the mean distance between the regions is at least 1 pm at the top surface of the regions.

6. The anode according to any one of claims 1 to 5, wherein the regions comprise columnar structures comprising silicon, preferably wherein the columnar structures extend in a substantially perpendicular direction from the surface plane of the current collector.

7. The anode according to any one of claims 1 to 6, wherein at least 95% of the regions comprise a plurality of adjoined columnar structures comprising silicon, preferably wherein the columnar structures extend in a substantially perpendicular direction from the surface plane of the current collector.

8. The anode according to claim 7, wherein the regions comprise a solid electrolyte interphase (SEI) or grain-like column boundaries between the adjoined columnar structures.

9. The anode according to any one of claims 1 to 8, wherein the gap between regions increases substantially linearly and / or substantially parabolically in relation to an increasing distance from the current collector.

10. The anode according to any one of claims 1 to 9, wherein the sloped lateral surfaces have an angle of from 40° to 85° to the current collector plane.11 . The anode according to any one of claims 1 to 10, wherein the anode has undergone lithiation and delithiation at least one time or two times.

12. The anode according to any one of claims 1 to 11 , wherein the silicon comprises amorphous silicon, optionally further comprising nano-crystalline silicon.

13. The anode according to any one of claims 1 to 12, wherein the current collector comprises copper, aluminium, nickel, titanium, carbon, iron, chromium, stainless steel, or an alloy thereof.

14. The anode according to any one of claims 1 to 13, wherein the current collector, at least a surface of the current collector facing the active material, comprises a Mean Summit Curvature [Ssc] situated between 15 pm-1to 40 pm-1, preferably between 18 pm-1to 26 pm-1.

15. The anode according to any one of the claims 1 to 14, wherein the current collector, at least a surface of the current collector facing the active material, comprises a Root Mean Square Gradient [Sdq] situated between 1.1 rad to 1 .4 rad.

16. The anode according to any one of the claims 1 to 15, wherein the current collector, at least a surface of the current collector facing the active material, comprises Developed Interfacial Area Ration (Sdr) of above 140%, preferably situated between 140% to 250%, preferably between 165% and 180%.

17. The anode according to any one of claims 1 to 16, wherein the current collector: a. has an ultimate tensile strength of at least 100 MPa; and / or b. has a yield strength of at least 50 MPa; and / or c. has a thickness of from 5 to 20 gm; and / or d. exhibits a surface roughness value selected from at least one of the following: an Sdr value of at least 40%; an Sz value of at least 4 gm; an Sa value of at least 0.2 gm; and an Sq value of at least 0.43 gm.

18. The anode according to any one of claims 1 to 17, wherein the current collector has an ultimate tensile strength of at least 250 MPa.

19. The anode according to any one of claims 1 to 18, wherein the current collector exhibits a surface roughness having: an Sdr value situated between 170% and 180%, preferably of at least 120%, an Sz value situated between 4.5 gm and 8.5 gm, preferably of at least 4.5 pm, and an Sa value situated between 0.3 gm and 0.7 gm, preferably of at least 0.3 gm.

20. The anode according to any one of claims 1 to 19, wherein the current collector comprises nodules.21 . The anode according to any one of claims 1 to 20, wherein the anode comprises an adhesion layer between the current collector and the layer comprising active material, preferably wherein the adhesion layer comprises nickel, zinc, tin, chromium, or silane, for example ZnO or SnC>2.

22. A method of preparing a lithium-ion cell, the method comprising: a. providing an anode, comprising providing a current collector and depositing active material comprising silicon on the current collector; b. providing the anode, a cathode, and an electrolyte comprising lithium; c. combining the anode, the cathode, and the electrolyte to form a lithium- ion cell; d. lithiating the anode; and e. delithiating the anode to form regions; i. wherein the regions are surrounded by gaps;ii. wherein the regions comprise sloped lateral surfaces; ill. wherein the mean distance between the regions is greater at the top surface of the regions than near the current collector surface; and iv. wherein the gaps comprise an area of from 5% to 35% of the top surface area of the anode; and optionally repeating the lithiating and delithiating at least once.

23. The method of preparing a lithium-ion cell according to claim 22, wherein step a further comprises forming a plurality of columnar structures comprising silicon, and wherein step e further comprises the step of delithiating the anode to connect the columnar structures and to form regions comprising columnar structures.

24. The method according to claim 23, wherein the electrolyte comprises a nonaqueous solvent or diluent, wherein the non-aqueous solvent or diluent comprises a carbonate or a compound comprising an ether group.

25. The method according to any one of claims 22 to 24, wherein depositing comprises using physical vapor deposition (PVD) or chemical vapor deposition (CVD).

26. The method according to any one of claims 22 to 25, wherein lithiating the anode comprises charging the lithium-ion cell to at least 3.8 V, preferably to at least 4.0 V.

27. The method according to any one of claims 22 to 26, wherein delithiating the anode comprises: connecting the columnar structures via a solid electrolyte interphase or grain-like boundaries; or fusing parts of the columnar structures.

28. The method according to any one of claims 22-27, wherein during step d of lithiating the anode, the cell is charged from approximately 0.2 V to 5.0 V, preferably 1 .0 V to 4.2 V.

29. The method according to any one of claims 22-28, wherein during step d of lithiating the anode, a charge rate situated between 0.001 C to 5.0 C, preferably 0.1C.

30. The method according to any one of claims 22-29, wherein during step d of lithiating the anode, a temperature situated between 10 degrees Celsius to 70 degrees Celsius, preferably between 30 degrees Celsius to 45 degrees Celsius.31 . The method according to any one of claims 22-30, wherein during step d of lithiating the anode, a pressure is situated between 0 Bar and 5000 Bar, preferably between 10 Bar to 1000 Bar, preferably approximately 100 bar.

32. The method according to any one of claims 22-31 , wherein during step e of delithiating the anode, the cell is discharged of from approximately 5.0 V to 2.0 V, preferably 4.2 V to 2.5 V.

33. The method according to any one of claims 22-32 wherein during step e of delithiating the anode, a charge rate situated between 0.001 C to 5.0 C, preferably 0.1 C.

34. The method according to any one of claims 22-33, wherein during step e of delithiating the anode, a temperature situated between 10 degrees Celsius to 70 degrees Celsius, preferably between 30 degrees Celsius to 45 degrees Celsius.

35. The method according to any one of claims 22-34, wherein during step e of delithiating the anode, a pressure is situated between 0 Bar and 5000 Bar, preferably between 10 Bar to 1000 Bar, preferably approximately 100 bar.

36. A method of preparing a lithium-ion cell comprising the anode according to any one of claims 1 to 21 using the method according to any one of claims 18 to 35.

37. A lithium-ion cell comprising the anode according to any one of claims 1 to 21.

38. A battery comprising the anode according to any one of claims 1 to 21 or the lithium-ion cell according to claim 37.

39. The lithium-ion cell according to claim 37 or the battery according to claim 38, wherein the lithium-ion cell or the battery comprises a non-aqueous solvent or diluent, wherein the non-aqueous solvent or diluent comprises a carbonate or a compound comprising an ether group.

40. Use of the anode according to any one of claims 1 to 21 in a lithium-ion cell or a battery or in the manufacture of a lithium-ion cell or a battery.

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