Anode with a double layer for use in lithium-ion batteries - Patent Application 20070122997

Abstract

The present disclosure relates generally to battery cells, and more particularly to an anode active material including two layers for use in lithium-ion battery cells.

Description

[Technical Field]

[0001] The present disclosure relates generally to battery cells, and more particularly to an anode having a bilayer anode active material for use in lithium ion battery cells. [Background technology]

[0002] Lithium-ion (Li-ion) batteries are widely used as power sources for consumer electronics, which require Li-ion batteries that deliver higher volumetric energy density and can sustain more discharge-charge cycles. Summary of the Invention

[0003] In a first aspect, the present disclosure is directed to an anode including an anode current collector, a first layer disposed on the anode current collector, and a second layer disposed on the first layer. The first layer includes silicon and the second layer includes graphite. The first and second layers together can be considered the anode active material.

[0004] In some variations, the anode current collector comprises copper or nickel. In some variations, the anode current collector is copper, such as copper foil. In some variations, the anode current collector is nickel, such as nickel foil. In some variations, the anode current collector is carbon-coated copper foil. In some variations, the anode current collector is carbon-coated nickel foil. In some variations, the first layer can be 5% to 60% by weight of the total weight of the first and second layers. In some variations, the first layer is 10% to 30% by weight of the total weight of the first and second layers. In further variations, the first layer is 15% to 25% by weight of the total weight of the first and second layers.

[0005] In a second embodiment, the first layer includes a first binder. In some variations, the first binder is present in an amount of 5% to 15% by weight of the first layer. In some variations, the first binder is selected from polyacrylic acid (PAA), polyimide (PI), polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethyleneimine (PI), polyurethane (PU), derivatives thereof, copolymers thereof, and combinations thereof. In further variations, the first binder is polyurethane. The first layer can also include carboxymethyl cellulose (CMC). In further variations, the first layer can include carbon nanotubes. In further variations, the first layer can include carbon black.

[0006] In a third aspect, the second layer includes a second binder. In some variations, the second binder is present in an amount of 1% to 10% by weight. In some variations, the second binder is selected from styrene butadiene rubber (SBR), CMC, and a combination of both SBR and CMC. In further variations, the second binder is a combination of SBR and CMC. In some variations, the SBR is present in an amount of 0.5% to 5% by weight. In some variations, the CMC is present in an amount of 0.5% to 5% by weight. In further variations, the second layer includes carbon black.

[0007] In a fourth aspect, a battery cell includes a cathode having a cathode active material disposed on a cathode current collector, an anode as described herein, a separator disposed between the cathode and the anode, and an electrolyte fluid disposed between the cathode and the anode.

[0008] The disclosure will be readily understood from the following detailed description when taken in conjunction with the accompanying drawings, in which like reference numerals designate like structural elements and in which: [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 2 is a top view of a battery cell according to an exemplary embodiment.

[0010] [Figure 2] FIG. 2 is a side view of a set of layers for a battery cell according to an exemplary embodiment.

[0011] [Figure 3A] FIG. 1 is a side view of an anode including an anode current collector, a first layer including a silicon-containing active material disposed on the anode current collector, and a second layer including graphite disposed on the first layer, according to an exemplary embodiment.

[0012] [Figure 3B] FIG. 2 is a side view of a copper foil anode current collector and a single layer including both silicon-containing active material and graphite disposed on the anode current collector, according to an exemplary embodiment.

[0013] [Figure 4] FIG. 1 illustrates the cycling performance of an anode having a first silicon-containing layer disposed on the anode and a second graphite-containing layer disposed on the silicon-containing layer compared to silicon and graphite combined in a single layer, according to an illustrative embodiment.

[0014] [Figure 5A] 1 is a scanning electron microscope (SEM) image of a first silicon-containing layer disposed on a copper anode current collector and a second graphite-containing layer disposed on the silicon-containing layer, according to an example embodiment.

[0015] [Figure 5B] 1 is an SEM image of an anode including an anode current collector and a single layer including both silicon and graphite disposed on the anode current collector, according to an exemplary embodiment.

[0016] [Figure 6A]1 is an SEM image of a graphite-containing layer without silicon-containing particles, according to an example embodiment;

[0017] [Figure 6B] 1 is an SEM image of a single layer combining both graphite and silicon containing particles according to an example embodiment;

[0018] [Figure 7A] 1 is a scanning electron microscope image of carbon nanotube particles arranged in a single layer of silicon-containing active material, according to an exemplary embodiment.

[0019] [Figure 7B] 1 is a scanning electron microscope image of carbon nanotube particles arranged in a layer containing bonded silicon and graphite, according to an example embodiment.

[0020] [Figure 8A] FIG. 1 illustrates capacity retention as a function of cycle number for two batteries, a first battery with an anode having a first silicon-containing layer disposed on the anode and a second graphite-containing layer disposed on the silicon-containing layer, and a second battery having a single layer of combined silicon and graphite disposed on the anode, according to an exemplary embodiment.

[0021] [Figure 8B] FIG. 1 illustrates capacity retention as a function of cycle number for two batteries, a first battery with an anode having a first silicon-containing layer disposed on the anode and a second graphite-containing layer disposed on the silicon-containing layer, and a second battery having a single layer of combined silicon and graphite disposed on the anode, according to an exemplary embodiment.

[0022] [Figure 9]FIG. 9 illustrates the discharge capacity over 100 cycles of three batteries: a battery 902 with an anode having a first silicon-containing layer disposed on the anode and a second graphite-containing layer disposed on the silicon-containing layer; a battery 904 with only a silicon-containing layer; and a battery 906 with only a graphite layer, according to an example embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] Reference will now be made in detail to exemplary embodiments as illustrated in the accompanying drawings. It should be understood that the following description is not intended to limit these embodiments to a single preferred embodiment. On the contrary, the following description is intended to cover alternatives, modifications, and equivalents, as may be included within the spirit and scope of the described embodiments as defined by the appended claims.

[0024] The present disclosure is directed to an anode including an anode current collector, a first layer disposed on the anode current collector, and a second layer disposed on the first layer. The first layer includes silicon (also referred to herein as a "silicon-containing layer"). The silicon may also be referred to as a "silicon-containing active material." The second layer includes graphite (also referred to herein as a "graphite-containing layer").

[0025] In some variations, the first layer disposed on the anode current collector is a graphite-containing layer and the second layer is a silicon-containing layer. In such variations, the graphite-containing layer can include any additional component in any amount as described for the graphite-containing layer herein. Similarly, the silicon-containing layer can include any component in any amount as described for the graphite-containing layer herein.

[0026] The different layers for silicon and graphite can include different binders. In various embodiments, the binder can help maintain contact between particles, allowing for increased electrical conductivity. In variations, the binder in the silicon-containing layer can have stronger adhesion / cohesion than the binder in the graphite-containing layer. Furthermore, the silicon-containing layer can include a greater amount of binder than the graphite-containing layer.

[0027] FIG. 1 shows a top view of a battery cell 100, according to one embodiment. The battery cell 100 may correspond to a lithium-ion or lithium polymer battery cell used to power devices used in consumer, medical, aerospace, defense, and / or transportation applications. The battery cell 100 includes a stack 102 containing multiple layers, including a cathode with a cathode active coating, a separator, and an anode with an anode active coating. More specifically, the stack 102 may include a strip of cathode active material (e.g., aluminum foil coated with a lithium compound) and a strip of anode active material (e.g., copper foil, nickel foil, carbon-coated copper foil, or carbon-coated nickel foil). The stack 102 also includes a strip of separator material (e.g., a microporous polymer membrane or a nonwoven mat) disposed between the strip of cathode active material and the strip of anode active material. The cathode layer, anode layer, and separator layer may remain flat in a planar configuration or may be rolled up in a rolled configuration (e.g., "roll cake"). An electrolyte solution is disposed between each cathode and anode.

[0028] During assembly of the battery cell 100, the stack 102 can be enclosed within a container, such as a pouch or a rigid container. The stack 102 can be in a flat or rolled configuration, although other configurations are possible. In some variations, the container can be a pouch. In such variations, the pouch is a flexible sheet folded along crease 112. In various embodiments, the flexible sheet is made of aluminum with a polymer film, such as polypropylene. After folding the flexible sheet, the flexible sheet can be sealed, for example, by applying heat along side seals 110 and along terrace seals 108. To improve packaging efficiency of the battery cell 100, density of the battery cell 100, or both, the flexible pouch can be 120 microns or less thick. In other variations, the container is a metal container that can be welded along seams.

[0029] The stack 102 may also include a set of conductive tabs 106 coupled to the cathode and anode. The conductive tabs 106 may extend through a seal of the pouch (e.g., formed using sealing tape 104) to provide terminals for the battery cell 100. The conductive tabs 106 may then be used to electrically couple the battery cell 100 to one or more other battery cells to form a battery pack. For example, a battery pack may be formed by coupling battery cells in a series, parallel, or series-parallel configuration. The coupled cells may be enclosed in a hard case to complete the battery pack, or may be incorporated into the enclosure of a portable electronic device such as a laptop computer, tablet computer, mobile phone, personal digital assistant (PDA), digital camera, and / or portable media player.

[0030] FIG. 2 shows a perspective view of a battery cell 200 (e.g., the battery cell 100 of FIG. 1 ) according to an embodiment of the present disclosure. The battery includes a cathode 202 including a current collector 204 and a cathode active material 206, and an anode 210 including an anode current collector 212 and an anode active material 214. A separator 208 is disposed between the cathode 202 and the anode 210. An electrolyte fluid 216 is disposed between the cathode 202 and the anode 210 and in contact with the separator 208. To fabricate the battery cell, the cathode 202, the separator 208, and the anode 210 may be stacked in a planar configuration or may be stacked and then wound into a wound configuration. The electrolyte fluid 216 may then be added. Prior to assembly of the battery cell, the set of layers may correspond to a cell stack.

[0031] The cathode current collector, cathode active material, anode current collector, anode active material, and separator may be any material known in the art, hi some variations, the cathode current collector may be aluminum foil and the anode current collector may be copper foil.

[0032] The cathode active material may be any material known in the art. For example, the cathode active material may be any of the cathode active materials described in U.S. Patent No. 10,297,823, the entire contents of which are incorporated herein by reference. As a further example, the compound may be any one of the compounds of formula (Ia) to formula (VIIIb) in U.S. Patent No. 10,297,823, the entire contents of which are incorporated herein by reference.

[0033] The separator may include a microporous polymer membrane or a nonwoven mat. Non-limiting examples of microporous polymer membranes or nonwoven mats include polyethylene (PE), polypropylene (PP), polyamide (PA), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyester, and polyvinylidene difluoride (PVdF). However, other microporous polymer membranes or nonwoven mats are also possible (e.g., gel polymer electrolytes). In some variations, the separator may be a separator such as that disclosed in U.S. Pat. No. 10,153,474, the entire contents of which are incorporated herein by reference.

[0034] Generally, a separator refers to a structure within a battery, such as an intervening layer, that allows ion transport between the cathode and anode while preventing physical contact between the two. Separators are formed from materials with pores that provide channels for ion transport, which may include absorbing an ion-containing electrolyte fluid. Separator materials can be selected according to chemical stability, porosity, pore size, permeability, wettability, mechanical strength, dimensional stability, softening temperature, and thermal shrinkage. These parameters can affect battery performance and safety during operation.

[0035] Generally, the electrolyte fluid can serve as a conductive pathway for the movement of cations that migrate from the negative electrode to the positive electrode during discharge. The electrolyte fluid can include any electrolyte fluid known in the art. In various embodiments, the electrolyte fluid can be, for example, the electrolyte fluid described in U.S. Patent Application No. 17 / 865,991, the entire contents of which are incorporated herein by reference.

[0036] Figure 3A shows a side view of an anode 300. The anode 300 includes an anode current collector 302. A first layer 304 including silicon 305 is disposed on the anode current collector 302. A second layer 306 including graphite 307 is disposed on the first layer 304. In contrast, Figure 3B shows a side view of an anode including the anode current collector 302 and a single layer 308 including both silicon 305 and graphite 307 disposed on the anode current collector 302.

[0037] In various embodiments, the silicon-containing layer and the graphite-containing layer can be present in weight percent ratios. In some variations, the silicon-containing layer is 60% or less of the total weight percent of the two layers. In some variations, the silicon-containing layer is 55% or less of the total weight percent of the two layers. In some variations, the silicon-containing layer is 50% or less of the total weight percent of the two layers. In some variations, the silicon-containing layer is 45% or less of the total weight percent of the two layers. In some variations, the silicon-containing layer is 40% or less of the total weight percent of the two layers. In some variations, the silicon-containing layer is 35% or less of the total weight percent of the two layers. In some variations, the silicon-containing layer is 30% or less of the total weight percent of the two layers. In some variations, the silicon-containing layer is 25% or less of the total weight percent of the two layers. In some variations, the silicon-containing layer is 20% or less of the total weight percent of the two layers. In some variations, the silicon-containing layer comprises 15% or less of the total weight percent of the two layers, hi some variations, the silicon-containing layer comprises 10% or less of the total weight percent of the two layers.

[0038] In some variations, the silicon-containing layer is at least 5 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 10 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 15 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 20 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 25 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 30 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 35 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 40 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 45 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 50 wt% of the total weight percent of the two layers. In some variations, the silicon-containing layer is at least 55% by weight of the total weight percent of the two layers.

[0039] In some variations, the graphite-containing layer comprises at least 30% by weight of the total weight of the two layers. In some variations, the graphite-containing layer comprises at least 35% by weight of the total weight of the two layers. In some variations, the graphite-containing layer comprises at least 40% by weight of the total weight of the two layers. In some variations, the graphite-containing layer comprises at least 45% by weight of the total weight of the two layers. In some variations, the graphite-containing layer comprises at least 50% by weight of the total weight of the two layers. In some variations, the graphite-containing layer comprises at least 55% by weight of the total weight of the two layers. In some variations, the graphite-containing layer comprises at least 60% by weight of the total weight of the two layers. In some variations, the graphite-containing layer comprises at least 65% by weight of the total weight of the two layers. In some variations, the graphite-containing layer comprises at least 70% by weight of the total weight of the two layers. In some variations, the graphite-containing layer is at least 75% by weight of the total weight of the two layers. In some variations, the graphite-containing layer is at least 80% by weight of the total weight of the two layers. In some variations, the graphite-containing layer is at least 85% by weight of the total weight of the two layers. In some variations, the graphite-containing layer is at least 90% by weight of the total weight of the two layers.

[0040] In some variations, the graphite-containing layer comprises 95% or less by weight of the two layers. In some variations, the graphite-containing layer comprises 90% or less by weight of the two layers. In some variations, the graphite-containing layer comprises 85% or less by weight of the two layers. In some variations, the graphite-containing layer comprises 80% or less by weight of the two layers. In some variations, the graphite-containing layer comprises 75% or less by weight of the two layers. In some variations, the graphite-containing layer comprises 70% or less by weight of the two layers. In some variations, the graphite-containing layer comprises 65% or less by weight of the two layers. In some variations, the graphite-containing layer comprises 60% or less by weight of the two layers. In some variations, the graphite-containing layer comprises 55% or less by weight of the two layers. In some variations, the graphite-containing layer comprises 50% or less of the total weight of the two layers. In some variations, the graphite-containing layer comprises 45% or less of the total weight of the two layers. In some variations, the graphite-containing layer comprises 40% or less of the total weight of the two layers. In some variations, the graphite-containing layer comprises 35% or less of the total weight of the two layers.

[0041] In some variations, the silicon-containing layer is 15-25 wt% of the total weight of the two layers, and the graphite-containing layer is 75-85 wt% of the two layers.

[0042] These layers can also have a range of thicknesses.

[0043] In some variations, the silicon-containing layer is at least 4 μm thick. In some variations, the silicon-containing layer is at least 8 μm thick. In some variations, the silicon-containing layer is at least 10 μm thick. In some variations, the silicon-containing layer is at least 15 μm thick. In some variations, the silicon-containing layer is at least 20 μm thick. In some variations, the silicon-containing layer is at least 25 μm thick. In some variations, the silicon-containing layer is at least 30 μm thick. In some variations, the silicon-containing layer is at least 35 μm thick. In some variations, the silicon-containing layer is at least 40 μm thick. In some variations, the silicon-containing layer is at least 45 μm thick.

[0044] In some variations, the silicon-containing layer is 50 μm or less thick. In some variations, the silicon-containing layer is 45 μm or less thick. In some variations, the silicon-containing layer is 35 μm or less thick. In some variations, the silicon-containing layer is 30 μm or less thick. In some variations, the silicon-containing layer is 25 μm or less thick. In some variations, the silicon-containing layer is 20 μm or less thick. In some variations, the silicon-containing layer is 15 μm or less thick. In some variations, the silicon-containing layer is 10 μm or less thick. In some variations, the silicon-containing layer is 8 μm or less thick.

[0045] In some variations, the graphite layer is at least 2.5 μm thick. In some variations, the graphite layer is at least 3 μm thick. In some variations, the graphite layer is at least 5 μm thick. In some variations, the graphite layer is at least 10 μm thick. In some variations, the graphite layer is at least 15 μm thick. In some variations, the graphite layer is at least 20 μm thick. In some variations, the graphite layer is at least 30 μm thick. In some variations, the graphite layer is at least 40 μm thick. In some variations, the graphite layer is at least 50 μm thick. In some variations, the graphite layer is at least 60 μm thick. In some variations, the graphite layer is at least 70 μm thick. In some variations, the graphite layer is at least 80 μm thick. In some variations, the graphite layer is at least 90 μm thick. In some variations, the graphite layer is at least 100 μm thick. In some variations, the graphite layer is at least 150 μm thick. In some variations, the graphite layer is at least 200 μm thick. In some variations, the graphite layer is at least 250 μm thick. In some variations, the graphite layer is at least 300 μm thick. In some variations, the graphite layer is at least 350 μm thick. In some variations, the graphite layer is at least 400 μm thick. In some variations, the graphite layer is at least 450 μm thick. In some variations, the graphite layer is at least 500 μm thick. In some variations, the graphite layer is at least 550 μm thick. In some variations, the graphite layer is at least 600 μm thick. In some variations, the graphite layer is at least 650 μm thick. In some variations, the graphite layer is at least 700 μm thick. In some variations, the graphite layer is at least 750 μm thick. In some variations, the graphite layer is at least 800 μm thick.In some variations, the graphite layer is at least 850 μm thick. In some variations, the graphite layer is at least 900 μm thick. In some variations, the graphite layer is at least 950 μm thick.

[0046] In some variations, the graphite layer is 1000 μm or less thick. In some variations, the graphite layer is 950 μm or less thick. In some variations, the graphite layer is 900 μm or less thick. In some variations, the graphite layer is 850 μm or less thick. In some variations, the graphite layer is 800 μm or less thick. In some variations, the graphite layer is 750 μm or less thick. In some variations, the graphite layer is 700 μm or less thick. In some variations, the graphite layer is 650 μm or less thick. In some variations, the graphite layer is 600 μm or less thick. In some variations, the graphite layer is 550 μm or less thick. In some variations, the graphite layer is 500 μm or less thick. In some variations, the graphite layer is 450 μm or less thick. In some variations, the graphite layer is 400 μm or less thick. In some variations, the graphite layer is 350 μm or less thick. In some variations, the graphite layer is 300 μm or less thick. In some variations, the graphite layer is 250 μm or less thick. In some variations, the graphite layer is 200 μm or less thick. In some variations, the graphite layer is 150 μm or less thick. In some variations, the graphite layer is equal to 90 or 80 μm thick. In some variations, the graphite layer is 70 μm or less thick. In some variations, the graphite layer is 60 μm or less thick. In some variations, the graphite layer is 55 μm or less thick. In some variations, the graphite layer is 50 μm or less thick. In some variations, the graphite layer is 45 μm or less thick. In some variations, the graphite layer is 30 μm or less thick. In some variations, the graphite layer is 25 μm or less thick. In some variations, the graphite layer is 20 μm or less thick. In some variations, the graphite layer is 15 μm or less thick. In some variations, the graphite layer is 10 μm or less thick. In some variations, the graphite layer is 5 μm or less thick.In some variations, the graphite layer is 3 μm or less in thickness. Silicon-containing layer

[0047] The silicon-containing layer can include any silicon compound known in the art. As described herein, silicon can also be referred to as a silicon-containing active material. In various non-limiting examples, silicon can be found in silicon-carbon composites, silicon monoxide (SiO x , also referred to herein as "silicon oxide"), a silicon-metal alloy, or a silicon-metal oxide. In some variations, the silicon is silicon oxide. Anode active materials that include silicon can achieve higher specific capacities than those that do not include silicon.

[0048] The silicon-containing layer can include a binder different from the graphite-containing layer. In some variations, the binder is selected from polyacrylic acid (PAA), polyimide (PI), polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethyleneimine (PI), polyurethane (PU), derivatives thereof, copolymers thereof, and combinations thereof. In some variations, the binder is selected from polyacrylic acid (PAA), polyimide (PI), polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethyleneimine (PI), polyurethane (PU), and combinations thereof. In some variations, the silicon-containing layer can include a polyurethane binder. In various embodiments, the silicon-containing layer can include a polyacrylic acid binder.

[0049] In some variations, the silicon-containing layer comprises at least 1 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 2 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 3 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 4 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 5 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 6 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 7 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 8 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 9 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 10 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 11 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 12 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 13 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 14 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 15 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 16 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 17 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 18 wt% binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises at least 19% by weight of the binder based on the total weight percent of the silicon-containing layer.

[0050] In some variations, the silicon-containing layer comprises 20 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 19 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 18 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 17 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 16 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 15 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 14 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 13 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 12 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 11 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 10 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 9 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 8 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 7 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 6 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 5 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 4 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 3 wt% or less of a binder, based on the total weight percent of the silicon-containing layer. In some variations, the silicon-containing layer comprises 2 wt% or less of a binder, based on the total weight percent of the silicon-containing layer.

[0051] In some variations, the first layer can include carbon nanotubes (CNTs), vapor grown carbon fibers (VGCFs), graphite (e.g., conductive graphite), carbon black, one of each individually, or a combination of two or more of the above.

[0052] In some additional variations, carbon nanotubes can be added to the silicon-containing layer. In some variations, the CNTs are single-walled CNTs. In some variations, the CNTs are multi-walled CNTs. In some variations, the CNTs can be a combination of single-walled and multi-walled CNTs.

[0053] In some variations, the CNTs may be at least 0.1 wt% of the silicon-containing layer. In some variations, the CNTs may be at least 0.2 wt% of the silicon-containing layer. In some variations, the CNTs may be at least 0.3 wt% of the silicon-containing layer. In some variations, the CNTs may be at least 0.4 wt% of the silicon-containing layer. In some variations, the CNTs may be at least 0.5 wt% of the silicon-containing layer. In some variations, the CNTs may be at least 0.6 wt% of the silicon-containing layer. In some variations, the CNTs may be at least 0.7 wt% of the silicon-containing layer. In some variations, the CNTs may be at least 0.8 wt% of the silicon-containing layer. In some variations, the CNTs may be at least 0.9 wt% of the silicon-containing layer.

[0054] In some variations, the CNTs may be 1.0 wt % or less of the silicon-containing layer. In some variations, the CNTs may be 0.9 wt % or less of the silicon-containing layer. In some variations, the CNTs may be 0.8 wt % or less of the silicon-containing layer. In some variations, the CNTs may be 0.7 wt % or less of the silicon-containing layer. In some variations, the CNTs may be 0.6 wt % or less of the silicon-containing layer. In some variations, the CNTs may be 0.5 wt % or less of the silicon-containing layer. In some variations, the CNTs may be 0.4 wt % or less of the silicon-containing layer. In some variations, the CNTs may be 0.3 wt % or less of the silicon-containing layer. In some variations, the CNTs may be 0.2 wt % or less of the silicon-containing layer.

[0055] In some variations, the silicon-containing layer comprises CMC. In some variations, the CMC is at least 0.1 wt% of the silicon-containing layer. In some variations, the CMC is at least 0.2 wt% of the silicon-containing layer. In some variations, the CMC is at least 0.3 wt% of the silicon-containing layer. In some variations, the CMC is at least 0.4 wt% of the silicon-containing layer. In some variations, the CMC is at least 0.5 wt% of the silicon-containing layer. In some variations, the CMC is at least 0.6 wt% of the silicon-containing layer. In some variations, the CMC is at least 0.7 wt% of the silicon-containing layer. In some variations, the CMC is at least 0.8 wt% of the silicon-containing layer. In some variations, the CMC is at least 0.9 wt% of the silicon-containing layer. In some variations, the CMC is at least 1.0 wt% of the silicon-containing layer. In some variations, the CMC is at least 1.1 wt% of the silicon-containing layer. In some variations, the CMC is at least 1.2 wt% of the silicon-containing layer. In some variations, the CMC is at least 1.3% by weight of the silicon-containing layer. In some variations, the CMC is at least 1.4% by weight of the silicon-containing layer.

[0056] In some variations, the CMC is 1.5% or less by weight of the silicon-containing layer. In some variations, the CMC is 1.4% or less by weight of the silicon-containing layer. In some variations, the CMC is 1.5% or less by weight of the silicon-containing layer. In some variations, the CMC is 1.2% or less by weight of the silicon-containing layer. In some variations, the CMC is 1.1% or less by weight of the silicon-containing layer. In some variations, the CMC is 1.0% or less by weight of the silicon-containing layer. In some variations, the CMC is 0.9% or less by weight of the silicon-containing layer. In some variations, the CMC is 0.8% or less by weight of the silicon-containing layer. In some variations, the CMC is 0.7% or less by weight of the silicon-containing layer. In some variations, the CMC is 0.6% or less by weight of the silicon-containing layer. In some variations, the CMC is 0.5% or less by weight of the silicon-containing layer. In some variations, the CMC is 0.4% or less by weight of the silicon-containing layer. In some variations, the CMC is 0.3% or less by weight of the silicon-containing layer. In some variations, the CMC is 0.2% or less by weight of the silicon-containing layer. graphite-containing layer

[0057] The graphite-containing layer can include a different binder than the silicon-containing layer. In some variations, the binder is SBR. In some variations, the binder is CMC. In some variations, the binder is a combination of SBR and CMC. A different binder is used to prepare a slurry for each active material, and then each material with a different binder and / or different amount of binder is coated separately.

[0058] In some variations, the weight percent of SBR is at least 0.5 weight percent of the graphite-containing layer. In some variations, the weight percent of SBR is at least 1.0 weight percent of the graphite-containing layer. In some variations, the weight percent of SBR is at least 2.0 weight percent of the graphite-containing layer. In some variations, the weight percent of SBR is at least 3.0 weight percent of the graphite-containing layer. In some variations, the weight percent of SBR is at least 4.0 weight percent of the graphite-containing layer. In some variations, the weight percent of SBR is at least 5.0 weight percent of the graphite-containing layer.

[0059] In some variations, the weight percent of SBR is 6.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of SBR is 5.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of SBR is 4.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of SBR is 3.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of SBR is 2.0% or less by weight of the graphite-containing layer.

[0060] In some variations, the weight percent of CMC is at least 0.1 weight percent of the graphite-containing layer. In some variations, the weight percent of CMC is at least 0.5 weight percent of the graphite-containing layer. In some variations, the weight percent of CMC is at least 1.0 weight percent of the graphite-containing layer. In some variations, the weight percent of CMC is at least 1.3 weight percent of the graphite-containing layer. In some variations, the weight percent of CMC is at least 1.5 weight percent of the graphite-containing layer. In some variations, the weight percent of CMC is at least 1.7 weight percent of the graphite-containing layer. In some variations, the weight percent of CMC is at least 2.0 weight percent of the graphite-containing layer. In some variations, the weight percent of CMC is at least 3.0 weight percent of the graphite-containing layer. In some variations, the weight percent of CMC is at least 4.0 weight percent of the graphite-containing layer.

[0061] In some variations, the weight percent of CMC is 5.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of CMC is 4.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of CMC is 3.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of CMC is 2.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of CMC is 1.7% or less by weight of the graphite-containing layer. In some variations, the weight percent of CMC is 1.3% or less by weight of the graphite-containing layer. In some variations, the weight percent of CMC is 1.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of CMC is 0.5% or less by weight of the graphite-containing layer.

[0062] In some variations, the weight percent of the SBR and CMC combination is at least 1.0 weight percent of the graphite-containing layer. In some variations, the weight percent of the SBR and CMC combination is at least 2.0 weight percent of the graphite-containing layer. In some variations, the weight percent of the SBR and CMC combination is at least 3.0 weight percent of the graphite-containing layer. In some variations, the weight percent of the SBR and CMC combination is at least 4.0 weight percent of the graphite-containing layer. In some variations, the weight percent of the SBR and CMC combination is at least 5.0 weight percent of the graphite-containing layer. In some variations, the weight percent of the SBR and CMC combination is at least 6.0 weight percent of the graphite-containing layer. In some variations, the weight percent of the SBR and CMC combination is at least 7.0 weight percent of the graphite-containing layer. In some variations, the weight percent of the SBR and CMC combination is at least 8.0 weight percent of the graphite-containing layer. In some variations, the weight percent of the combination of SBR and CMC is at least 9.0 weight percent of the graphite-containing layer.

[0063] In some variations, the weight percent of the combination of SBR and CMC is 10.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of the combination of SBR and CMC is 9.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of the combination of SBR and CMC is 8.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of the combination of SBR and CMC is 7.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of the combination of SBR and CMC is 6.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of the combination of SBR and CMC is 5.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of the combination of SBR and CMC is 4.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of the combination of SBR and CMC is 3.0% or less by weight of the graphite-containing layer. In some variations, the weight percent of the combination of SBR and CMC is 2.0% or less by weight of the graphite-containing layer.

[0064] 4 shows the capacity as a function of the number of battery cycles for a first battery 402, which is a battery cell having an anode similar to that of FIG. 3A (having a silicon-containing layer disposed on a copper foil substrate and a graphite-containing layer disposed on the silicon-containing layer). Specifically, the anode of battery 402 includes a first layer including 85.00 wt. % silicon oxide, 9.80 wt. % PU binder, 0.70 wt. % binder CMC, 5.00 wt. % SFG-6L additive, and 0.5 wt. % SWCNTs (single-walled carbon nanotubes) disposed on a copper foil substrate, and a second layer of 95.60 wt. % graphite with 2.00 wt. % SBR binder and 1.30 wt. % CMC binder. The anode of the second battery 404 contained a single layer of both silicon oxide and graphite, with 94.21 wt% active material consisting of 20 wt% silicon oxide and 80 wt% graphite, 4.71 wt% of a combination of PU binder, SBR binder, and CMC binder, 0.14 wt% SWCNTs, and 0.94 wt% Super P (carbon black). The batteries with both anode active materials maintained approximately the same capacity up to 28 cycles. However, the battery with both silicon-containing and graphite-containing layers as anode active materials maintained capacity from 28 to 46 cycles. The battery with a single layer of anode active material exhibited a steeper decline. The bilayer anode active material resulted in substantially improved battery performance.

[0065] Figure 5A shows an SEM image of the layers shown in Figure 3A. The image shows a copper current collector 502, a first layer including silicon oxide 504 disposed on the copper current collector 502, and a second layer of graphite 506 disposed on the first layer including silicon oxide 504. Figure 5B shows an image of a single layer including both graphite and silicon oxide in Figure 3B. The image shows the copper current collector 502 and the single layer including both graphite 506 and silicon oxide 504.

[0066] Figure 6A shows an SEM image of the graphite-containing layer shown in Figure 3A without silicon oxide. Specifically, only graphite 602 is visible in the image of the graphite-containing layer. This image does not show any silicon oxide particles. In contrast, Figure 6B shows an SEM image of graphite and silicon oxide bonded in a single layer, such as that shown in Figure 3B. Silicon oxide particles 604 can be seen interspersed among the graphite 602.

[0067] FIG. 7A shows CNT particles 702 and silicon oxide particles 704 when the silicon oxide and graphite are separated into two layers. In a variation, the CNTs are more effective on the silicon-containing layer alone when the same total amount of CNTs is added. FIG. 7B shows CNT particles 702 in a single layer of bonded silicon oxide particles 704 and graphite 706. However, when the silicon oxide and graphite are bonded in a single layer, the CNTs are shared between the graphite and silicon oxide. The CNT particles coated both the silicon oxide and graphite in a single layer, unlike the case of only silicon oxide as in the two-layer anode active material.

[0068] Both Figures 8A and 8B show a comparison of capacity retention as a function of cycle number for a bilayer anode active material having separate silicon- and graphite-containing layers and a single-layer anode active material. The anode active materials are the same as those shown in Figure 4. In both Figures 8A and 8B, the capacity retention as a function of cycle number is higher for the bilayer anode active material 402 than for the single-layer anode active material 404.

[0069] 9 shows the discharge capacity over various cycle numbers for three batteries: a battery 902 with an anode having a first silicon-containing layer disposed on the anode and a second graphite-containing layer disposed on the silicon-containing layer, a battery 904 with only a silicon-containing layer, and a battery 906 with only a graphite layer. The results demonstrate that the batteries with two anode layers exhibit improved electrochemical performance over batteries with a single layer anode.

[0070] The anodes described herein may be useful in battery cells, including those used in electronic devices and consumer electronic products. The term "electronic device" as used herein may refer to any electronic device known in the art. For example, the electronic device may be any communication device, such as a telephone, such as a mobile phone or landline phone, or a smartphone, including an iPhone®, and an electronic email sending / receiving device. The electronic device may also be an entertainment device, including a portable DVD player, a conventional DVD player, a Blu-ray Disc player, a video game console, a music player, such as a portable music player (e.g., an iPod®), or the like. The electronic device may also be part of a display, such as a digital display, a TV monitor, an e-reader, a portable web browser (e.g., an iPad®), a wristwatch (e.g., an Apple Watch), or a computer monitor. The electronic device may also be part of a device that provides control, such as controlling the streaming of images, video, and audio (e.g., an Apple TV®), or may be a remote control for an electronic device. Furthermore, the electronic device may be part of a computer or its accessories, such as a hard drive tower housing or casing, a laptop housing, a laptop keyboard, a laptop trackpad, a desktop keyboard, a mouse, and speakers. The anode cells, lithium metal batteries, and battery packs may also be applied in devices such as watches or clocks.

[0071] In the foregoing description, for purposes of explanation, specific terminology was used to provide a thorough understanding of the described embodiments. However, it will be apparent to those skilled in the art that specific details are not required to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the embodiments to the precise form disclosed. It will be apparent to those skilled in the art that numerous modifications and variations are possible in light of the above teachings.

Claims

1. an anode current collector; a first layer disposed on the anode current collector and comprising a silicon-containing active material; a second layer disposed on the first layer, the second layer comprising graphite; an anode.

2. 10. The anode of claim 1, wherein the anode current collector comprises copper or nickel.

3. 3. The anode according to claim 1, wherein the first layer accounts for 5 to 60% by weight of the total weight of the first and second layers.

4. 4. The anode according to claim 1, wherein the first layer is 10% to 30% by weight of the total weight of the first layer and the second layer.

5. 5. The anode of claim 1, wherein the first layer is 15% to 25% by weight of the total weight of the first layer and the second layer.

6. The anode of claim 1 , wherein the first layer comprises a first binder.

7. 7. The anode of claim 6, wherein the first binder is selected from polyacrylic acid (PAA), polyimide (PI), polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethyleneimine (PI), polyurethane (PU), derivatives thereof, copolymers thereof, and combinations thereof.

8. 8. The anode of claim 7, wherein the first binder comprises polyurethane or polyacrylic acid.

9. The anode of claim 8 wherein the first binder is polyurethane.

10. 10. The anode of claim 6, wherein the first layer comprises carboxymethyl cellulose (CMC).

11. 11. The anode of claim 1, wherein the first layer comprises single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor grown carbon fiber (VGCF), graphite, or carbon black.

12. 12. The anode of claim 6, wherein the first binder is in an amount of 5% to 20% by weight of the first layer.

13. The anode of claim 1 , wherein the second layer comprises a second binder.

14. 14. The anode of claim 13, wherein the second binder is in an amount of 1% to 10% by weight of the second layer.

15. 15. The anode of claim 13 or 14, wherein the second binder is selected from styrene butadiene rubber (SBR), CMC, and a combination of both.

16. 16. The anode of claim 13, wherein the second binder is a combination of SBR and CMC.

17. 17. The anode of claim 15 or 16, wherein the SBR is in an amount of 0.5% to 5% by weight.

18. 18. The anode of claim 15, wherein the CMC is in an amount of 0.5% to 5% by weight.

19. 19. The anode of claim 1, wherein the second layer comprises carbon black.

20. a cathode including a cathode active material disposed on a cathode current collector; An anode according to any one of claims 1 to 19; a separator disposed between the cathode and the anode; an electrolyte fluid disposed between the cathode and the anode; , a battery cell.

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