ELECTRODE FEATURING LITHIUM-RICH NICKEL-MANGANE OXIDES

Abstract

A cathode for use in a lithium-ion battery, comprising an active material present in an amount of 70 to 99 wt.%, wherein the active material comprises a lithium-rich nickel-manganese oxide; a conductive network of a mixture of conductive elements present in an amount of 0.25 to 20 wt.%, wherein the mixture of conductive elements comprises two or more low-aspect-ratio particles, plate-like particles, and needle-like particles; and a binder system present in an amount of 0.25 to 10 wt.%, wherein the binder system comprises a primary binder polymer and an acid group or a salt thereof, the amounts being based on a total weight of the cathode.

Description

INTRODUCTION

[0001] The disclosure relates to electrodes for lithium-ion batteries and batteries having such electrodes.

[0002] There is a need for advanced energy storage devices and systems to meet the energy and / or power requirements for a variety of products, including automotive products such as start-stop systems (e.g., 12V start-stop systems), battery-assisted systems, hybrid electric vehicles ("HEVs"), and electric vehicles ("EVs"). Typical lithium-ion batteries comprise at least two electrodes and an electrolyte and / or separator. One of the two electrodes serves as the cathode, and the other electrode serves as the anode. A separator and / or electrolyte may be disposed between the negative and cathodes. The electrolyte is suitable for conducting lithium ions between the electrodes and, like the two electrodes, may be in solid and / or liquid form and / or as a hybrid thereof.In cases of solid-state batteries, which comprise solid-state electrodes and a solid-state electrolyte, the solid-state electrolyte can physically separate the electrodes, eliminating the need for a separate separator.

[0003] Conventional rechargeable lithium-ion batteries work by reversibly shunting lithium ions between the anode and cathode. For example, lithium ions can move from the cathode to the anode when charging the battery and in the opposite direction when discharging. Such lithium-ion batteries can reversibly supply power to an associated charging device when needed. More specifically, the lithium-ion battery can supply electrical current to a load device until the anode's lithium content is effectively depleted. The battery can then be recharged by passing a suitable direct electrical current in the opposite direction between the electrodes.

[0004] The performance of a lithium-ion battery may decrease after cycling. For example, capacity loss may occur after cycling.

[0005] It would be desirable to have a battery that has high operating voltage and high reversible capacities, while also having good cycling stability and reduced voltage drop. SUMMARY

[0006] In an exemplary embodiment, a cathode for use in a lithium-ion battery is disclosed, the cathode comprising an active material present in an amount of 70 to 99 wt. %, the active material comprising a lithium-rich nickel manganese oxide; a conductive network composed of a mixture of conductive elements present in an amount of 0.25 to 20 wt. %, the mixture of conductive elements comprising two or more low aspect ratio particles, plate-like particles, and needle-like particles; and a binder system present in an amount of 0.25 to 10 wt. %, the binder system comprising a primary binder polymer and an acid group or a salt thereof. The amounts are based on a total weight of the cathode.

[0007] Additionally, the cathode may comprise one or more of the features described herein. The lithium-rich nickel manganese oxide may have the formula xLi2MnO3*(1-x)LiMO2, where 0 < x ≤ 0.5, M comprises Ni, Mn, and optionally Co, and the Ni:Mn molar ratio is in the range of 1:4 to 1:1.

[0008] The mixture of conductive elements may comprise the low aspect ratio particles in an amount of 0.1 to 10 wt%, the plate-like particles in amounts of 0 to 10 wt% based on the total weight of the cathode, and the needle-like particles in amounts of 0.05 to 5 wt% based on the total weight of the cathode.

[0009] The cathode may comprise 90 to 99 wt% of the lithium-rich nickel manganese oxide, based on the total weight of the cathode.

[0010] The low aspect ratio particles can be soot, the plate-like particles can be graphene nanoplatelets, and the needle-like particles can be carbon nanotubes.

[0011] The low aspect ratio particles can have an average particle size of 2 to 200 nanometers and an aspect ratio of 2:1 to 1:1.

[0012] The plate-like particles may have a thickness in a range of 5 nanometers to 100 nanometers and a dimension orthogonal to the thickness in a range of 1 to 25 micrometers.

[0013] The needle-like particles can have a length of 0.1 to 100 micrometers and an aspect ratio of 10 to 5000.

[0014] The active material may further comprise up to 60 wt.% of one or more additional metal oxides or phosphates. The additional metal oxides or phosphates may be lithium manganese oxide (Li (1+x) Mn2O4, where 0.1 ≤ x ≤ 1) (LMO), lithium nickel manganese oxide (LiNi 0,5 Mn 1,5 O4) (LNMO), lithium cobalt oxide (LiCoO2) (LCO), lithium nickel manganese cobalt oxide (LiNi 1-x-y Co x Mn y O2) (where 0 ≤ x ≤1 and 0 ≤ y ≤ 1) (NMC), lithium cobalt manganese aluminum oxide (LiNi 1-x-y-z Co x Mn y Al z O2, where 0.0 < x+y+z < 0.25) (NCMA), lithium iron phosphate (LiFePO4), lithium vanadium phosphate (LiVPO4), lithium manganese iron phosphate (LiMn 1-x Fe x PO4, where 0 ≤ x ≤ 1) or a combination thereof.

[0015] A portion of the conductive elements can be functionalized with hydroxyl or carboxyl groups.

[0016] The primary binder polymer may comprise polyvinylidene fluoride.

[0017] The acid group can be a carboxylic acid or a sulfonic acid.

[0018] The acid group can be present in amounts ranging from 0.05 to 10 milliequivalents per gram of the binder system.

[0019] The acid group can be present on an acid-functional polymer that differs from the primary binder polymer.

[0020] The acid group may be present in an amount of 0.05 to 10 milliequivalents per gram of the acid-functional polymer.

[0021] The binder system may comprise 50 to 95 wt% primary binder polymer and 5 to 50 wt% acid functional polymer, based on the total weight of the binder system.

[0022] The acid-functional polymer may comprise an acid-functional polymer, polyvinylidene fluoride, (co)polymer or aromatic ionomer, sulfo-phenylated polyphenylene, a sulfonated derivative of poly(arylene ether), poly(arylene ether sulfone), poly(arylene sulfide), sulfonated polyimide, sulfonated polyphenylene, or combinations thereof.

[0023] In a particular embodiment, the cathode comprises 90 to 99 wt.% of the lithium-rich nickel-manganese oxide having the formula Li[Li 1 / 3-2x / 3 Ni x Mn 2 / 3-x / 3 ]O2, wherein 0 < x < 0.5, 0.5 to 5 wt.% of the primary binder polymer, 0.1 to 1 wt.% of an acid-functional polymer, 0.05 to 1 wt.% of the carbon nanotubes, 0.1 to 5 wt.% of the carbon black, and 0 to 3 wt.% of the graphene nanoplatelets, wt.% being based on the total weight of the cathode.

[0024] In another exemplary embodiment, an electrochemical cell is disclosed comprising an anode arranged on a current collector, an anode arranged on an anode current collector, and an electrolyte, wherein the cathode comprises an active material present in an amount of 70 to 99 wt.%, the active material comprising a lithium-rich nickel-manganese oxide; a conductive network of a mixture of conductive elements present in an amount of 0.25 to 20 wt.%, the mixture of conductive elements comprising two or more particles with low aspect ratios, plate-like particles, and needle-like particles; and a binder system present in an amount of 0.25 to 10 wt.%, the binder system comprising a primary binder polymer and an acid group or a salt thereof. The cathode in the electrochemical cell may comprise one or more of the additional features described herein.

[0025] The aforementioned features and advantages, as well as other features and advantages of the disclosure, are readily apparent from the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further features, advantages and details are listed only as examples in the following detailed description, which refers to the drawings, where: Fig. Figure 1 is a schematic cross-sectional side view of a battery cell; Fig. Figure 2 is a schematic cross-sectional side view of an electrochemical cell of a battery comprising the cathode of Fig. 1; Fig. Figure 3A is a graph of capacity versus cycles for the cathode formulations described in Example 1; Fig.Figure 3B is a graph of discharge retention versus cycling for the cathode formulations described in Example 1; Fig. Figure 4 is a voltage versus capacity graph for a battery having a comparable cathode formulation; Fig. 5 is a voltage versus capacity diagram for a battery that has a cathode formulation according to an example; Fig. 6A is a diagram of capacity versus cycles for the cathode formulations described in Example 3; and Fig. Figure 6B is a diagram of discharge retention versus cycles for the cathode formulations described in Example 3. DETAILED DESCRIPTION

[0027] Lithium-rich active materials (LMRs) for cathodes can provide high average operating voltages and high capacities, but the practical implementation of these materials has been challenging. One challenge is poor cycling stability (e.g., voltage drop and capacity decay during cycling). Various approaches have been proposed to address these challenges, including surface modification of the LMR with metal oxides, doping of the LMR, annealing of the LMR, and managing the morphology or structure. These complex approaches primarily focus on the LMR itself. Surprisingly, it has been discovered that selecting the formulation of the active materials, binder, and conductive elements of a cathode can be a simple and cost-effective approach to harness the benefits of using LMR materials while significantly improving cycling stability (e.g.,Reducing voltage drop and / or capacitance drop).

[0028] The following description is merely exemplary and is not intended to limit the present disclosure, its application, or its use. It is understood that in the drawings, corresponding reference numerals denote identical or corresponding parts and features.

[0029] The cathode disclosed herein comprises an active material of lithium-rich nickel manganese oxide, a mixture of conductive elements of different geometries forming a conductive network, and a binder system incorporating acid functionality. Active material

[0030] The active material comprises lithium-rich nickel-manganese oxide. By lithium-rich, we mean that the molar ratio of lithium to other metals (e.g., nickel, manganese, and optionally an additional transition metal such as Co) in the active material is greater than 1:1, e.g., 1.1:1 to 1.49:1. For example, the lithium-rich nickel-manganese oxide can be represented as xLi2MnO3 * (1-x)LiMO2; 0 < x ≤ 0.5, where M comprises Ni and Mn, and where the molar ratio of Ni:Mn ranges from 1:4 to 1:1. In one example, M consists of, or consists essentially of, Ni and Mn. In another example, M further comprises an additional transition metal such as Co. When such an additional transition metal (e.g., Co) is present, the ratio of additional transition metal to Mn can be less than 1:5 or less than 1:10. As another example, the lithium-rich metal oxide can be represented by the formula Li[Li 1 / 3-2y / 3 Ni y Mn 2 / 3-y / 3]O2, where 0 < y < 0.5.

[0031] The active material can be in the form of particles with an average particle size of 0.5 to 30 or even 20 micrometers (i.e., µm or micrometers). The particle size can be measured, for example, by light scattering of a solvent dispersion using low-angle laser light scattering (LALLS) or by electron microscopy of a dry powder or coating.

[0032] Optionally, the active material may comprise, in addition to the lithium-rich nickel manganese oxide, one or more additional metal oxides or phosphates, such as lithium manganese oxide (Li (1+x) Mn2O4, where 0.1 ≤ x ≤ 1) (LMO), Lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4) (LNMO), lithium cobalt oxide (LiCoO2) (LCO), lithium nickel manganese cobalt oxide (LiNi 1-x-yC O x Mn y O2) (where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1) (NMC), lithium cobalt manganese aluminum oxide (LiNi 1-x-y-zCO x Mn y Al z O2, where 0.0 < x+y+z < 0.25) (NCMA), lithium iron phosphate (LiFePO4), lithium vanadium phosphate (LiVPO4), lithium manganese iron phosphate (LiMn 1-x Fe x PO4, where 0 ≤ x ≤ 1), and combinations thereof. The amount of these additional metal oxides can be 0, 0.5, 1, 2, 3, 5, 5 up to 60, 50, 40, 30, 20, or 10 wt.%, based on the total weight of the active material. The active material can be cobalt-free.

[0033] The active material may be present in the cathode in amounts of 50, 60, 70, 80, 85, 90, 92 or 95 up to 99 or up to 98 wt%, based on the total weight of the cathode. Conductive elements

[0034] The conductive elements comprise small particles of different geometries. In particular, the conductive elements comprise two or more of the following particles: small particles with low aspect ratios, plate-like particles, and needle-like particles. For example, the conductive elements are a binary mixture of small particles with low aspect ratios and needle-like particles. In another example, the conductive elements are a binary mixture of small particles with low aspect ratios and plate-like particles. In another example, the conductive elements are a binary mixture of plate-like particles and needle-like particles. In another example, the conductive particles can be a ternary mixture of small particles with low aspect ratios, plate-like particles, and needle-like particles.

[0035] The small particles with low aspect ratios can be essentially spherical or irregular, with an aspect ratio of the longest to the shortest dimension of 2:1 to 1:1, 1.5:1 to 1:1, or 1.2:1 to 1:1. For example, the small particles with low aspect ratios can be soot. The particles with low aspect ratios, such as soot, can have an average particle diameter of 2 to 200, 150, or 200 nanometers. The particle size can be measured, for example, by low-angle laser light scattering (LALLS). The particles with low aspect ratios can have a surface area in a range of 10 to 500 square meters per gram (m 2 / g) and an electrical conductivity in a range of 0.5 S / cm to 50 S / cm. The soot can be furnace soot with a surface area of ​​approximately 45-65 m 2 / g in various embodiments. Alternatively, the carbon black could, for example, be acetylene carbon black with a surface area of ​​approximately 130-240 m². 2 / g in various implementations. Alternatively, the carbon black could be, for example, another acetylene carbon black with a surface area of ​​approximately 280 to 320 m². 2 / g in different implementations.

[0036] The surface area can be measured, for example, using the Brunauer-Emmett-Teller (BET) method.

[0037] Electrical conductivity can be measured, for example, using a 4-point probe measurement or using a potentiostat that applies various currents (I) in amperes [A] to an electrode and measures the corresponding voltages [V]. Using Ohm's law, V = I*R, the resistance (R) in ohms [Ω] can be calculated (R = V / I).

[0038] The plate-like particles may have a thickness of about 5 to 100 nanometers and a dimension orthogonal to the thickness of about 1 to 25 micrometers. For example, the plate-like structures may be graphene sheets or graphene sheet stacks comprising at least two graphene sheets stacked one on top of the other. Each graphene sheet is formed from a single layer of carbon atoms arranged in a honeycomb lattice. The graphene sheet stacks may be in the form of graphite flakes and may contain more than 10 graphene sheets, or more than 20 graphene sheets and up to 50 stacked graphene sheets. Alternatively, the graphene sheet stacks may also be in the form of graphene nanoplatelets, which have a disc- or lens-like shape and consist of stacks of 2 to 10 graphene sheets.The plate-like structures, such as graphene nanoplatelets, may have an aspect ratio of greater than or equal to about 20 or an aspect ratio of greater than or equal to about 100 up to 1000. The plate-like structures, such as graphene nanoplatelets, may have a dimension orthogonal to the thickness (e.g., diameter) in a range of 1 to 25 or 2 to 10 micrometers and thicknesses in a range of 5 nanometers to 100 nanometers. The plate-like structures, such as graphene nanoplatelets, may have a porosity of about 90%. The plate-like structures, such as graphene nanoplatelets, may have a surface area in a range of 10 m. 2 / g up to 200 m 2 / g. The plate-like structures, such as graphene nanoplatelets, can have an electrical conductivity of about 100 Siemens per centimeter (S / cm), measured in a direction perpendicular to a major surface, and an electrical conductivity of about 10 7S / cm, measured in a direction parallel to a major surface.

[0039] Porosity can be measured using the mercury intrusion method, for example. Surface area can be measured using the low-angle laser light scattering method, for example.

[0040] The needle-like structures (e.g., having an aspect ratio (length:diameter or length:width) of greater than or equal to about 10, greater than or equal to 50, greater than or equal to 100, or greater than or equal to about 500, greater than or equal to about 1000 and up to 5000, or up to 3000. For example, the needle-like conductive particles may comprise carbon nanotubes. The needle-like conductive particles, such as carbon nanotubes, may have a substantially cylindrical cross-section in a direction orthogonal to the longest dimension (length). The needle-like conductive particles, such as carbon nanotubes, may have aspect ratios (length:diameter (or length:width if not cylindrical)) of greater than or equal to about 10, greater than or equal to 50, greater than or equal to 100, or greater than or equal to about 500, greater than or equal to about 1000 and up to to 5000 or up to 3000.The needle-like conductive particles, such as carbon nanotubes, can have dimensions orthogonal to the length (e.g., diameter) in a range of 0.5 nanometers to 50 nanometers and lengths in a range of 0.1, 0.5, 1, 2, or 3 micrometers up to 100, up to 50, up to 20, or up to 10 micrometers.

[0041] The needle-like conductive particles, such as carbon nanotubes, can have a porosity greater than about 97%. The needle-like conductive particles can be in the form of single-walled carbon nanotubes (SWCNTs) and / or multi-walled carbon nanotubes (MWCNTs). The needle-like conductive particles, such as carbon nanotubes, can have surface areas ranging from 50, 100, 200, 300, or 400 to 1300, 1000, 700, or 500 m². 2 / g and electrical conductivities in a range of 102 S / cm to 106 S / cm. In particular, the MWCNTs can have a surface area of, for example, 260 to 350 or 280 to 320 m 2 / g. The SWCNTs can have a surface area of, for example, 380 to 420 m 2 / g. Bundling the carbon nanotubes can reduce the measured surface area.

[0042] Optionally, a portion of the conductive elements, for example the carbon nanotubes, may comprise one or more functional hydroxyl groups (-OH) and / or functional carboxyl groups (-COOH), which may contribute to a uniform distribution of the carbon nanotubes over the entire thickness of the cathode.

[0043] The total amount of conductive elements in the cathode can range from 0.25, 0.5, or 1 wt.% up to 49.8, up to 25, up to 20, up to 10, or up to 5 wt.%, based on the total weight of the cathode. Particles with low aspect ratios, such as carbon black, can be present in amounts ranging from 0.1 or 0.25 wt.% up to 10, up to 5, up to 3, or up to 2 wt.%, based on the total weight of the cathode.

[0044] The plate-like conductive particles, such as graphene sheet stacks, can be present in amounts of 0, 0.1, or 0.25 up to 10, up to 5, up to 3, or up to 2 wt%, based on the total weight of the cathode. The needle-like conductive particles, such as carbon nanotubes, can be present in amounts of 0 or 0.05 up to 5, 3, or 1 wt%, based on the total weight of the cathode.

[0045] As a specific example, the conductive elements can be 0.7 to 1 wt% carbon black, 0.5 to 0.7 wt% graphene nanoplatelets, and 0.05 to 0.15 wt% single-walled carbon nanotubes (SWCNTs) in a ternary mixture, based on the total weight of the cathode. As another example, the conductive elements can be 0.25–1.5% multi-walled carbon nanotubes (MWCNTs) and 1.25–0% carbon black in a binary mixture. Binder system

[0046] The cathode comprises a binder system. The binder system comprises a primary polymeric binder. For example, the primary polymeric binder can be a primary polymeric binder such as polyvinylidene fluoride (PVDF) homopolymer or copolymer. The binder system comprises acid functional groups or salts thereof. The acid functional groups can contribute to the dispersion of the other components of the cathode. Examples of acid functional groups or salts thereof are carboxylic acid groups, sulfonic acid groups, and salts thereof. The acid functionality can be present in the binder system in amounts of 0.0025 to 3 milliequivalents (meq) per gram of the binder system. The acid functionality can be provided by an acid-functional polymer that is different from the primary polymeric binder. For example, the binder system can comprise 50 to 95 or 70 to 90 wt. % primary binder polymer and 5 to 50 or 10 to 30 wt.-% acid-functional polymer, based on the total weight of the binder system. The amount of acid functionality in this acid-functional polymer can range from 0.05 to 5 milliequivalents per gram of acid-functional polymer. The acid-functional polymer can comprise acid-functionalized PVDF homopolymer or copolymer, sulfophenylated polyphenylene (SPPP-H) and a sulfonated derivative of poly(arylene ether) (SPAE), poly(arylene ether sulfone) (SPAES), poly(arylene sulfide) (SPAS), sulfonated polyimide (SPI), sulfonated polyphenylene (SPP), or a combination of two or more thereof. The acid-functionalized PVDF (co)polymer can be, for example, P(VDF (vinylidene fluoride) : TFE (tetrafluoroethylene) : 4:1 mass fraction).

[0047] The polymer binder system can, for example, comprise 95-50% polyvinylidene fluoride (PVDF) homopolymer with 5-50% acid-functionalized PVDF (co)polymer or aromatic ionomer. The acid-functionalized PVDF (co)polymer can, for example, be P(VDF (vinylidene fluoride) : TFE (tetrafluoroethylene) :: 4:1 mass fraction) with approximately 0.10 to 0.15 meq of carboxylic acid per gram of polymer.

[0048] As another example, the acid-functionalized polymer may have a different backbone composition and acid loading, such as sulfo-phenylated polyphenylene (SPPP-H) with approximately 3 to 3.5 meq of sulfonic acid per gram of polymer.

[0049] For example, the acid-functionalized polymer may have a meq value between approximately 0.05 and 10.0 per gram of polymer.

[0050] The acid-functionalized polymer can be, for example, one of sulfophenylated polyphenylene (SPPP-H) and a sulfonated derivative of poly(arylene ether) (SPAE), poly(arylene ether sulfone) (SPAES), poly(arylene sulfide) (SPAS), sulfonated polyimide (SPI), sulfonated polyphenylene (SPP), and combinations thereof, and one or more cations selected from H+, Li+, Na+, K+ and NH4+.

[0051] The binder system is present in the cathode in amounts of 0.25, 0.5 or 1 up to 45, up to 20, up to 10 or up to 5 wt.%, based on the total weight of the cathode.

[0052] In a specific example, the cathode can contain 90 to 99 wt.% of the lithium-rich nickel-manganese oxide, which has the formula Li[Li 1 / 3-2x / 3 Ni x Mn 2 / 3-x / 3]O2, where 0 < x < 0.5, 0.5 to 5 percent of the primary binder polymer, 0.0.5 to 5 percent of the primary binder polymer, 0.1 to 1 percent of an acid-functional polymer, 0.05 to 1 percent of single-walled carbon nanotubes, 0.1 to 3 percent of the carbon black, and 0.1 to 2 wt% of the graphene nanoplatelets, the percentages being based on the total weight of the cathode.

[0053] In another particular example, the cathode comprises 90 to 99 wt.% of lithium-rich nickel-manganese oxide with the formula Li[Li 1 / 3-2x / 3 Ni x Mn 2 / 3-x / 3 ]O2, where 0 < x < 0.5, 0.5 to 5 percent of the primary binder polymer, 0.1 to 1 percent of an acid functional polymer, 0.05 to 1.5 percent of multi-walled carbon nanotubes, and 0.1 to 3 percent of carbon black, the percentages being based on the total weight of the cathode. Cathode and method for forming a cathode

[0054] The cathode can be formed by combining the active material, the conductive material, and the binder system in a solvent and coating this mixture onto a substrate. The substrate can be a current collector for the cathode. The coating is dried to form the cathode. For example, the conductive materials can be combined with a solvent such as N-methylpyrrolidone (NMP) and stirred for a period of time, approximately 5 to 15 minutes. The binder system can then be added with an additional 2 to 10 minutes of stirring. The active cathode material can then be added with an additional 2 to 10 minutes of stirring. Additional solvent can be added with subsequent stirring to obtain a slurry with a viscosity suitable for the coating. The slurry can be coated onto the substrate (e.g., the current collector) and then dried.Drying can be done, for example, in an oven at 50 to 120 °C and / or under vacuum.

[0055] According to an exemplary embodiment, as shown in Fig.As shown in Figure 1, the cathode 12 comprises a composite material of active material particles 32, a binder 34, a dispersion agent (not shown), and a combination of electrically conductive additives (36, 38, 40). In assembly, the cathode 12 is arranged on the main surface 20 of a current collector 22 in the form of a continuous, uniform layer of material. The cathode 12 may include open pores 44, defined by its porous structure, which can be infiltrated with an electrolyte 18. The thickness of the cathode 12, measured from the main surface 20 of the cathode current collector 22 to an adjacent surface 42, may range from 5 micrometers to 600 micrometers.The particles of the active material 32, the binder 34, the dispersant and the combination of electrically conductive carbon additives are distributed substantially homogeneously over the entire cathode 12 on the main surface 20 of a cathode current collector 22. Electrochemical cell

[0056] The cathode can be used in an electrochemical cell comprising the cathode, an anode, and an electrolyte. For example, as in Fig.As shown in Figure 2, the electrochemical cell 10 can comprise a cathode 12, an anode 14 spaced apart from the cathode 12, and a porous separator 16 arranged between the positive terminal and the anodes 12 and 14. The cathode and anode 12 and 14, as well as the porous separator 16, are infiltrated with an electrolyte 18, which provides a medium for the conduction of lithium ions through them. The cathode 12 is arranged on a main surface 20 of a cathode current collector 22, and the anode 14 is arranged on a main surface 24 of an anode current collector 26. In practice, the cathode and anode current collectors 22 and 26 can be electrically connected to a power source or load 28 via an external circuit 30. The electrochemical cell 10 may be combined with one or more additional electrochemical cells to form a lithium-ion battery.

[0057] The anode 14 comprises an active material. The active material can be, for example, graphite, a silicon-based graphite mixture, or a silicon-based particle. The anode 14 can also comprise a binder. The binder can be the same or different from the binder for the cathode. The binder can be, for example, PVDF, polyacrylonitrile (PAN), guar gum (GG), gum arabic (GA), polysaccharide lambda-carrageenan (CGN), cellulose polymers such as carboxymethylcellulose (CMC), sodium alginate (SA), polyimide (PI), polyvinyl alcohol (PVA), chitosan (CS), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), or ammonia-polyacrylic acid PAA-NH3.

[0058] The anode 14 may comprise conductive elements such as soot, graphene, carbon nanotubes, or combinations thereof.

[0059] The separator 16 may, for example, comprise a polymer film, such as a polypropylene film or a coated polypropylene film.

[0060] The electrolyte 18 can, for example, comprise a metal salt such as a lithium salt dissolved in one or more solvents, optionally with additional electrolyte additives. For example, the lithium salt can comprise lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The molarity can be 0.5 to 2 molars. The solvent can be, for example, ethyl methyl carbonate (EMC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), polyethylene carbonate (PEC), vinyl carbonate (VC), trimethyl phosphate (TMP), sulfolane (SL), difluorobenzene (DFC), or a combination thereof.The electrolyte additive may, for example, comprise VC, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorophosphate (LiDFP), FEC, lithium bisoxalatoborate (LiBOB), prop-1-ene-1,3-sulfone (PES), ethylene sulfite (ES), succinonitrile (SCN), TMP or tris(trimethylsilyl)phosphite (TMPi) or a combination thereof. Examples Example 1

[0061] The formulations were prepared by combining and mixing lithium-rich (LMR) active particles with the formula Li[Li 1 / 3-2x / 3 Ni x Mn 2 / 3-x / 3 ]O2, where 0.3 ≤ x ≤ 0.4 PVDF as primary polymer binder, furnace black with 65 m 2 / g surface area as soot, graphene nanoplatelets with 65 m 2 / g surface, single-walled carbon nanotubes with 400 m 2 / g surface area and an acid functional polymer having a sulfophenylated polyphenylene (sPPP) backbone composition in N-methyl-2-pyrrolidone (NMP) solvent with a combined solids weight of 60% based on a total weight of the blend.

[0062] The specific formulations prepared are shown in Table 1. The conductive additives were first combined with NMP and milled for 10 minutes. The binder and dispersant polymer were added and mixed for an additional 5 minutes. Then, the LMR particles were added and mixed for an additional 5 minutes. Additional solvent was added and mixed for 10 minutes. This mixture was coated onto a current collector and dried.

[0063] An electrochemical cell comprising these cathodes of formulas 1-3 and an anode (containing active silicon-graphite particles, a mixture of conductive elements, and a water-based binder), a polypropylene separator, and a high-voltage-stable LiPF6-based electrolyte (Electrolyte A) was fabricated. These cells were charged to 4.6 V and discharged twice to 2 volts (C-rate) of C / 3 (charging or discharging over 3 hours for a full-capacity battery) at a constant voltage. The C-rate is the measure of the current at which a battery is charged and discharged.

[0064] The cells were then discharged to 2 volts at a C-rate of C / 3 and tested for their specific discharge capacity in milliamperes per gram [mAh / g] and discharge capacity retention. Discharge retention capacity was calculated by dividing each specific discharge capacity by the highest discharge capacity during the entire cycling cycle, cycled, and evaluated for capacity and discharge retention. Fig. 3A represents the specific capacity in milliampere hours per gram of mass (mAh / g) on ​​the y-axis and the number of cycles on the x-axis. Fig.Figure 3B represents the discharge retention (%) on the y-axis and the number of cycles on the x-axis. Formulation 1 is represented by the triangles, formulation 2 by the circles, and formulation 3 by the stars. The comparative formulation 1, which includes only carbon black as a conductive additive, shows a significantly faster decrease in capacity and discharge duration compared to compositions containing a mixture of conductive carbons as a conductive additive. Table 1 formulation Weight% active material Wt% Primary polymer binder Wt% acid-functional polymer Ge w.% soot Wt% graphene nanoplatelets Wt.% SWC NT 1 (comparative) 97 1,5 0 1,5 0 0 2 97 1,2 0,3 0,8 0,6 0,1 3 97 1,0 0,25 1,0 5 0,6 0,1 Example 2

[0065] Electrochemical cells prepared as in Example 1 using formulations 1 and 2 were evaluated for voltage drop during discharge. Fig. 4 and Fig. 5, the y-axis is the voltage (V) and the x-axis is the capacity in milliampere-hours per gram of mass (mAh / g). The voltage profile for formulation 1 is shown in Fig.4 for cycle 1 (square), cycle 2 (circle) and cycle 3 (triangle). The stress profile for formula 1 is shown in Fig. 5, where cycle 1 is represented by a square symbol, cycle 3 by an inverted triangle symbol, cycle 200 by a star symbol, and cycle 400 by a diamond symbol. As in Fig. 4 and Fig. As shown in Figure 5, formulation 2 shows significantly better cyclization stability than comparative formulation 1. Example 3

[0066] Electrochemical cells prepared as disclosed in Example 1 using formulation 2 (1.2 wt% PVDF and 0.3 wt% of the acid-functionalized polymer) and a comparative formulation 4 containing 1.5% PVDF but without dispersion polymer Fig. 6A, shows on the y-axis the specific capacity in milliampere hours per gram of mass (mAh / g) and on the x-axis the number of cycles. Fig.Figure 6B represents the discharge retention (%) on the y-axis and the cycle number on the x-axis. Formulation 2 is represented by solid circles, while comparative formulation 4 is represented by open circles. Both formulations comprise 0.1 wt% single-walled carbon nanotubes, 0.8 wt% furnace black, and 0.6 wt% graphene nanoparticles. As shown in Fig. 6A and Fig. As shown in Figure 6B, incorporating the dispersion polymer into the binder system improves durability. Example 4

[0067] Electrochemical cells prepared as in Example 1 using Formulation 3. Formulation 5 does not include graphene. Formulation 6 omits the graphene and uses a different carbon black, including an acetylene black from Denka and multi-walled carbon nanotubes from Cabot. The amounts are shown in Table 2. The cells used a different electrolyte B. Each formulation demonstrated a discharge retention of over 97% at 100 cycles. formulation Weight -% active material Wt% Primary polymer binder Wt% acid-functional polymer wt.% soot Wt% graphene nanoplatelets Wt.% SWC NT Wt.% MW CNT 3 97 1,0 0,25 1,0 5 0,6 0,1 - 5 97 1 0,25 1,4 - 0,1 - 6 97 1,0 0,25 0,5 8 - - 1,17

[0068] The terms "a / an / an" do not imply a quantity limitation, but denote the presence of at least one of the mentioned items. The term "or" means "and / or" unless the context clearly indicates otherwise. References to "an aspect" throughout this specification mean that a particular element (e.g., a feature, structure, step, or property) described in connection with the aspect is included in at least one of the aspects described herein and may or may not be present in other aspects. In addition, it is understood that the described elements in the various aspects may be combined in any suitable manner.

[0069] When an element such as a layer, film, region, or substrate is described as lying "on" another element, it may lie directly on top of the other element, or there may be intervening elements. In contrast, when an element is described as lying "directly on" another element, there are no intervening elements.

[0070] Unless otherwise indicated herein, all examination standards are the most recent standard in effect on the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the examination standard appears.

[0071] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0072] Although the above disclosure has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalent elements may be substituted without departing from the scope of the disclosure. In addition, many changes may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, the present disclosure is not intended to be limited to the specific embodiments, but is intended to include all embodiments falling within its scope.

Claims

[1] A cathode for use in a lithium-ion battery, the cathode comprising an active material present in an amount of 70 to 99 wt.%, wherein the active material comprises a lithium-rich nickel-manganese oxide; a conductive network comprising a mixture of conductive elements present in an amount of 0.25 to 20 wt.%, wherein the mixture of conductive elements comprises two or more low aspect ratio particles, plate-like particles, and needle-like particles, and a binder system present in an amount of 0.25 to 10 wt.%, wherein the binder system comprises a primary binder polymer and an acid group or a salt thereof, where the amounts are based on a total weight of the cathode. [2] The cathode of claim 1, wherein the lithium-rich nickel-manganese oxide has the formula xLi2MnO3*(1-x)LiMO2, where 0 < x ≤ 0.5, M comprises Ni, Mn and optionally Co, and the molar ratio of Ni:Mn is in the range of 1:4 to 1:

1. [3] The cathode according to claim 1, wherein the mixture of conductive elements comprises the low aspect ratio particles in an amount of 0.1 to 10 wt%, the plate-like particles in amounts of 0 to 10 wt% based on the total weight of the cathode, and the needle-like particles in amounts of 0.05 to 5 wt% based on the total weight of the cathode, and wherein the low aspect ratio particles are carbon black, the plate-like particles are graphene nanoplatelets, and the needle-like particles are carbon nanotubes. [4] The cathode of claim 1, wherein the active material further comprises up to 60 wt% of one or more additional metal oxides or phosphates. [5] The cathode of claim 1, wherein the primary binder polymer comprises polyvinylidene fluoride. [6] The cathode of claim 1, wherein the acid group is a carboxylic acid or sulfonic acid present in amounts of 0.05 to 10 milliequivalents per gram of binder system. [7] The cathode of claim 1, wherein the acid group is provided on an acid-functional polymer different from the primary binder polymer, and the acid group is present in an amount of 0.05 to 10 milliequivalents per gram of the acid-functional polymer. [8] The cathode of claim 7, wherein the binder system comprises 50 to 95 wt% primary binder polymer and 5 to 50 wt% acid functional polymer, based on the total weight of the binder system. [9] The cathode of claim 7, wherein the acid functional polymer comprises an acid functional polymer, polyvinylidene fluoride, (co)polymer or aromatic ionomer, sulfo-phenylated polyphenylene, sulfonated derivative of poly(arylene ether), poly(arylene ether sulfone), poly(arylene sulfide), sulfonated polyimide, sulfonated polyphenylene, or combinations thereof. [10] An electrochemical cell comprising the cathode disposed on a current collector, an anode disposed on an anode current collector, and an electrolyte, the cathode comprising an active material present in an amount of 70 to 99 wt.%, wherein the active material comprises a lithium-rich nickel-manganese oxide; a conductive network composed of a mixture of conductive elements present in an amount of 0.25 to 20 wt.%, wherein the mixture of conductive elements comprises two or more low aspect ratio particles, plate-like particles and needle-like particles, and a binder system present in an amount of 0.25 to 10 wt.%, wherein the binder system comprises a primary binder polymer and an acid group or a salt thereof, where the amounts are based on a total weight of the cathode.

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