Lithium-ion battery and method for manufacturing a lithium-ion battery

Abstract

The lithium-ion battery has a cathode including a composite cathode active material and an anode including an anode active material. The composite cathode active material includes at least first and second cathode active materials, where the second cathode active material is a compound having an olivine structure, and at least the degree of lithiation of the first cathode active material is different from the lithium content of the second cathode active material. The degree of lithiation of the first active cathode material, a, is higher than the degree of lithiation of the second active cathode material, b, before electrolyte filling or the first discharge and / or charge step of the lithium-ion battery. The anode active material is pre-lithiated before electrolyte filling or the first discharge and / or charge step of the lithium-ion battery. It also provides a method for manufacturing such a lithium-ion battery.

Description

[Technical Field]

[0001] The present invention relates to lithium-ion batteries and methods for manufacturing lithium-ion batteries. [Background technology]

[0002] In the following, the term "lithium-ion battery" is used synonymously with all prior art terms for galvanic elements and cells containing lithium, including lithium batteries, lithium cells, lithium-ion cells, lithium polymer cells, and lithium-ion rechargeable batteries. In particular, rechargeable batteries (secondary batteries) are included. Furthermore, the terms "battery" and "electrochemical cell" are used synonymously with "lithium-ion battery." Lithium-ion batteries may also be, for example, ceramic-based or polymer-based solid-state batteries.

[0003] A lithium-ion battery has at least two types of electrodes: a positive electrode (cathode) and a negative electrode (anode). Each of these electrodes contains at least one active material, and optionally, additives such as electrode binders and conductive additives may be used in combination.

[0004] A general explanation of lithium-ion technology can be found in Chapter 9 (Lithium-ion cell, Author Thomas Woehrle) of the lithium-ion battery handbook “Handbuchs Lithium-Ionen-Batterien” (Herausgeber Reiner Korthauer, Springer, 2013) and in Chapter 9 (Lithium-ion cell, Author Thomas Woehrle) of the book “Lithium-Ion Batteries: Basics and Applications” (Editor Reiner Korthauer, Springer, 2018). A suitable cathode active material is known from EP0017400 B1.

[0005] In lithium-ion batteries, both the cathode active material and the anode active material are required to have the function of reversibly intercepting and releasing lithium ions.

[0006] Current state-of-the-art lithium-ion batteries are assembled and packaged in a fully uncharged state. This corresponds to a state where lithium ions are fully intercalated, or stored, in the cathode, while the anode typically does not contain active, reversibly circulating lithium ions.

[0007] During the initial charging process of a lithium-ion battery (also called "formation"), lithium ions leave the cathode and are intercalated (stored) at the anode. This initial charging process involves a complex sequence of events, including numerous reactions that occur between the various components of the lithium-ion battery.

[0008] Of particular importance is the formation of an interface between the active material and the electrolyte (electrolyte solution) at the anode, also known as the "solid electrolyte interface" or "SEI". The formation of the SEI, which can be considered a protective layer, is basically due to the decomposition reaction between the surface of the anode active material and the electrolyte.

[0009] However, lithium is required to construct the SEI, and it cannot be used for subsequent cycling in the charge and discharge process. The difference between the initial charge capacity and the subsequent charge capacity is known as the formation loss in relation to the charge capacity, and can range from approximately 5% to 40% depending on the cathode and anode active materials used.

[0010] Therefore, the cathode active material must be supplied in larger quantities, i.e., in greater volume, to achieve the desired nominal capacity of the finished lithium-ion battery even after formation losses, which increases manufacturing costs and reduces the specific energy of the battery. This also increases the need for toxic metals and / or other metals that are not readily available, which are required for the production of cathode active materials such as cobalt and nickel.

[0011] From EP3255714B1, it is known to provide an additional lithium depot made of a lithium alloy in the cell so as to compensate for lithium loss during cell formation and / or cell operation. However, providing additional components requires a more complex cell structure and additional manufacturing processes, which in some cases involve increased labor and higher costs.

[0012] In the manufacture of cells known in the prior art, lithium-ion batteries are first assembled in a non-charged state and then formed. This formation is an extremely expensive process because it requires special equipment and high safety standards, especially with regard to fire protection.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0014]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0015] The object of the present invention is to provide a lithium-ion battery having a higher specific energy and a higher current carrying capacity, and to provide an inexpensive method for manufacturing such a lithium-ion battery. In particular, it is desirable that the method for manufacturing such a lithium-ion battery be simpler than known methods.

[0016] According to the present invention, the problem is solved by a lithium-ion battery having a cathode comprising a composite cathode active material and an anode comprising at least one anode active material. The composite cathode active material comprises at least a first and a second cathode active material, wherein the second cathode active material is a compound having an olivine structure. The first cathode active material has a degree of lithiation a, and the second cathode active material has a degree of lithiation b. The degree of lithiation b of the second cathode active material is lower than the degree of lithiation a of the first cathode active material before the first discharge and / or charge step of the lithium-ion battery. The anode active material is pre-lithified before the first discharge and / or charge step of the lithium-ion battery.

[0017] In particular, the lithiumization degree b of the first cathode active material before the lithium-ion battery is filled with electrolyte is lower than the lithiumization degree b of the second cathode active material. The lithiumization degree b of the second cathode active material is less than 1, especially before the lithium-ion battery is filled with electrolyte.

[0018] The term "degree of lithiation" refers to the content of reversibly circulating lithium in the form of lithium ions and / or metallic lithium relative to the maximum content of reversibly circulating lithium in the active material. In other words, the degree of lithiation is an indicator of the proportion of the maximum circulating lithium content intercalated within the structure of the active material.

[0019] A degree of lithiation of 1 indicates a fully lithified active material, while a degree of lithiation of 0 indicates a fully delithified active material.

[0020] For example, the degree of lithiation is 1 for stoichiometric olivine LiFePO4, and 0 for pure FePO4.

[0021] The first cathode active material may include or consist of all anodic active materials known in the prior art.

[0022] Preferably, the first cathode active material is selected from the group consisting of layered oxides containing perlithiated oxide (OLO), compounds having an olivine structure, compounds having a spinel structure, and combinations thereof.

[0023] The first cathode active material differs from the second cathode active material, at least with respect to its respective degree of lithiumization.

[0024] In this sense, the first and second cathode active materials can be selected from the same compound class, for example, two olivines with different lithium content and / or two olivines with different chemical compositions.

[0025] In particular, the first and second cathode active materials are structurally different. For example, the first cathode active material exists as a layered oxide, while the second cathode active material exists as a compound having an olivine structure. The layered oxide can contain perlithiated oxides (OLO).

[0026] Due to its olivine structure, the second cathode active material may exhibit lower kinetic inhibition than the first cathode active material with respect to lithium uptake, especially when the first cathode active material is a layered oxide.

[0027] By using a second cathode active material with a low degree of lithiation and generally low kinetic inhibition of lithium intercalation before the first discharge and / or charge step, a corresponding amount of lithium ions that can no longer be intercalated in the first cathode active material after the first charge step can be re-embedded in the cathode, leaving the anode, during the discharge step at a normal current rate. In particular, this portion is intercalated in the second cathode active material. As a result, formation losses occurring during the first charge step can be reduced, and consequently, the energy density, specific energy, or nominal capacity of a lithium-ion battery having such a composite cathode active material can be improved.

[0028] After filling with the electrolyte, lithium ions are also deposited in the second cathode active material, particularly during the first discharge cycle. Therefore, the ratio of the lithiation degrees of the first and second cathode active materials can change after filling with the electrolyte and / or after the first discharge and / or charging process. However, since formation losses occur almost exclusively during the first discharge and / or charging process, the initial state of the composite cathode active material is particularly important to avoid formation losses. Accordingly, the details regarding the lithiation degrees of the first and second cathode active materials in the composite cathode active material according to the present invention relate to the state before the first discharge and / or charging process, and especially to the state before filling with the electrolyte.

[0029] According to the present invention, the anode active material is pre-lithified before the first discharge and / or charge step of the lithium-ion battery. The term “pre-lithified” or “pre-lithified” indicates that, before the first discharge and / or charge step, particularly before being filled with the electrolyte, the lithium-ion battery is at least partially present in the structure of the anode active material, particularly intercalated and / or alloyed.

[0030] Lithium used as reserve lithium can later be used as a reserve lithium in the discharge and discharge cycles of the lithium-ion battery, and can also be used to form SEI before or during the first discharge and / or charge cycle of the lithium-ion battery. Thus, pre-lithiation can at least partially compensate for the formation losses that would otherwise occur. This can further reduce the amount of costly and toxic cathode active materials such as cobalt and nickel. Furthermore, the reaction that forms SEI does not have to occur only during the first discharge and / or charge cycle of the assembled lithium-ion battery, but can at least partially occur during the fabrication of the anode active material and / or anode, especially after the electrolyte has been filled.

[0031] In particular, the anode material is pre-lithified to the extent that it contains more lithium than is necessary to form the SEI during anode manufacturing and / or lithium-ion battery formation. Before the first discharge and / or charge step of the lithium-ion battery, especially before filling with the electrolyte, it is preferable that the anode active material has a degree of lithification c greater than 0 and further has a stable SEI.

[0032] The anode active material is particularly stoichiometrically pre-lithified, and the degree of lithiumization γ of the active material is less than 1. In particular, the degree of lithiumization γ of the anode active material can be in the range of 0.01 to 0.5, preferably in the range of 0.05 to 0.30. When graphite is used as the anode active material, this is Li 0.01≦x≦0.5 C6 or Li 0.05≦x≦0.30 This would correspond to the composition of C6. When silicon is used as the anode active material, this would be Li 0.375≦x≦1.857 Si1 or Li 0.1875≦x≦1.125 This would correspond to the composition of Si1.

[0033] By combining a partially delithified composite cathode active material with an optionally quasi-stoichiometrically prelithified anode active material, lithium-ion batteries can be at least partially directly charged after assembly and therefore immediately ready for use.

[0034] The first discharge and / or charge process can be carried out in the intended application, for example, directly at the end consumer. Individual electrochemical cells can also be connected first to form a battery module, and then discharge and / or charge for the first time.

[0035] In this way, the pre-charging and molding processes, i.e., the initial charging stage of the lithium-ion battery, can be omitted in the manufacturing process, thereby shortening the manufacturing time. Furthermore, it is possible to reduce power consumption in the manufacturing process and lower the size and operating rate of the required production equipment.

[0036] The difference between the degree of lithiumization of the first cathode active material and the degree of lithiumization of the second cathode active material should be 0.1 or greater.

[0037] Preferably, the difference between the degree of lithiation of the first cathode active material and the degree of lithiation of the second cathode active material may be 0.5 or greater. This large difference in the degree of lithiation of the two cathode active materials ensures that sufficient lithium from the anode can be taken up by the second active material in a kinetically advantageous manner. This can occur even after the first charging step, or even in the first discharge step prior to the first charging step, if the anode is pre-lithified to a corresponding degree.

[0038] In further modifications, the second cathode active material is completely delithified. In other words, lithium is not present in the second cathode active material before the first discharge and / or charge cycle of the lithium-ion battery, except for unavoidable impurities.

[0039] Partially or completely delithiated cathode active materials are commercially available or can be obtained by electrochemically extracting lithium from fully or partially lithiated cathode active materials. Chemical extraction of lithium from fully or partially lithiated cathode active materials is also possible, by eluting lithium with an acid, such as sulfuric acid (H2SO4).

[0040] The degree of lithiation of the composite cathode active material can be adapted to the pre-lithiation of the anode active material. In other words, the degree of lithiation of the composite cathode active material can be reduced by the amount of lithium used for pre-lithiation of the anode active material. In this way, the energy density or open-circuit voltage of the lithium-ion battery can be further optimized.

[0041] According to one embodiment, the first cathode active material comprises a layered oxide.

[0042] The layered oxide of the first cathode active material can contain nickel and cobalt, and in particular the layered oxide is a nickel-manganese-cobalt compound or a nickel-cobalt-aluminum compound.

[0043] Layered oxides can also contain other metals, as is known from the prior art. In particular, layered oxides can contain doping metals, such as magnesium, aluminum, tungsten, chromium, titanium, or combinations thereof.

[0044] In one modified example, the first cathode active material is a layered transition metal oxide having an α-NaCrO2 structure. Such cathode active materials are disclosed, for example, in EP0017400A1.

[0045] Lithium-nickel-manganese-cobalt compounds are also known by the abbreviation NMC and sometimes by the technical abbreviation NCM. NMC-based cathode active materials are used, in particular, in lithium-ion batteries for automobiles. NMC as a cathode active material has an advantageous combination of desirable properties, such as high specific capacity, reduced cobalt content, high current capability, and high intrinsic safety, which is reflected, for example, in sufficient stability in the case of overcharge.

[0046] NMC can be described by the general formula Li α Ni x Mn y Co z O2, where α represents the specification of the stoichiometric ratio of lithium and is usually between 0.8 and 1.15. Certain stoichiometries are indicated in the literature as a triple of numbers, such as NMC 811, NMC 622, NMC 532, and NMC 111. The triple of numbers indicates the relative values of the nickel:manganese:cobalt content for each example. That is, for example, NMC 811 is a cathode active material having the general formula unit LiNi 0.8 Mn 0.1 Co 0.1 O2, that is, α = 1, and further the so-called lithium- and manganese-rich NMC having the general formula unit Li 1+ε (Ni x Mn y Co z ) 1-ε O2 can also be used, where ε is especially between 0.1 and 0.6, preferably between 0.2 and 0.4. These lithium-rich layered oxides are also known as over-lithiated (layered) oxides (OLO).

[0047] According to the present invention, all general NMCs can be used as the first cathode active material.

[0048] Alternatively, a lithium-nickel-cobalt-aluminum compound can be used as the first cathode active material. This cathode active material is known by the abbreviation NCA and has the general formula unit Li α Nix Co y Al z This can be described using O2 and x+y+z=1. Here, α represents the stoichiometric ratio of lithium, which is usually between 0.80 and 1.15.

[0049] Alternatively, lithium-cobalt compounds or lithium-nickel-cobalt compounds can be used as the first cathode active material, which are known by the abbreviations LCO or LNCO, and have the general formula unit Li α CoO2 or Li α Ni x Co y This can be described using O2 as x + y = 1. Here, α indicates the stoichiometric ratio of lithium, which is usually between 0.80 and 1.15.

[0050] In the first cathode active material of the composite cathode active material according to the present invention, a is at least 1, where a represents the degree of lithiumization of the first cathode active material. Correspondingly, the first cathode active material is completely lithiumized.

[0051] In further embodiments, the first cathode active material is a layered oxide, a compound having an olivine structure, and / or a compound having a spinel structure, and the second cathode active material is a compound having an olivine structure. Preferably, the first cathode active material is a layered oxide, and the second cathode active material is a compound with an olivine structure.

[0052] In particular, the second cathode active material and optionally the first cathode active material include iron-based compounds, iron and manganese-based compounds, or cobalt and / or nickel-based compounds.

[0053] In particular, compounds having an olivine structure include iron phosphate, iron manganese phosphate, iron cobalt phosphate, iron manganese cobalt phosphate, cobalt manganese phosphate, nickel phosphate, nickel cobalt phosphate, nickel iron phosphate, nickel iron phosphate, nickel iron phosphate, nickel manganese phosphate, nickel manganese phosphate, or combinations thereof. Furthermore, compounds having an olivine structure may also be substances mentioned in relation to lithium, such as lithium iron phosphate.

[0054] The second cathode-active material having an olivine structure has a degree of lithium b in the range of 0 to 0.9, preferably 0 to 0.5. For example, an olivine compound has the general formula unit Li β It can be represented as MPO4, where M is selected from the group consisting of iron, cobalt, nickel, manganese, and combinations thereof.

[0055] Such olivine compounds exhibit fast and reversible kinetics for lithium-ion intercalation, resulting in high current capacity and excellent low-temperature behavior in lithium-ion batteries. Furthermore, because compounds with an olivine structure are extremely stable, they can further enhance the inherent safety of lithium-ion batteries.

[0056] Compounds with an olivine structure are commercially available, far cheaper than NMCs, and have lower toxicity. Furthermore, such olivine compounds are perfectly compatible with common electrode binders, electrolyte compositions, and conductive additives, such as conductive carbon black, and are also compatible with common cathode active material manufacturing processes, such as mixing, coating, calending, stamping, cutting, winding, lamination, and lamination processes.

[0057] Generally, "compounds having an olivine structure" or "olivine compounds" refer to substances whose crystal structure corresponds to olivine, such as LiFePO4.

[0058] Preferably, the delithified olivine compound, especially in the case of layered oxides, contains only iron and / or manganese and does not contain other toxic metals and / or optionally available metals. Therefore, the first cathode active material and / or the second cathode active material have higher mechanical and thermal elasticity. The same applies to lithium-ion secondary batteries consisting of composite cathode active materials.

[0059] The particle size of the olivine compound can be in the range of 0.05 to 30 μm, preferably 0.1 to 15 μm, and more preferably 0.2 to 5 μm. Such particle sizes are optimal for blending the olivine compound with further particles of the first and / or second cathode active material, particularly NMC. In this way, a homogeneous and high-density composite cathode electrode can be obtained.

[0060] The first cathode-active material can be a manganese-based compound having a spinel structure, particularly a LiMn2O4-based compound. Non-stoichiometric spinels, where lithium is localized at the manganese sites in the crystal structure, can also be used. Furthermore, nickel-manganese spinels with a higher potential relative to lithium are also possible, for example, Li 0 ≤ x ≤ 1. 1-x Ni 0.5 Mn 1.5 O4 is one example.

[0061] The difference between the degree of lithiumization a of the first cathode active material and the degree of lithiumization b of the second cathode active material can be at least 0.1, preferably at least 0.5.

[0062] Based on the total weight of the composite cathode active materials, the weight (mass) ratio of the second cathode active material is preferably lower than the mass ratio of the first cathode active material.

[0063] However, as a general rule, the ratio of the masses of the first and second cathode active materials can be selected as desired.

[0064] The second cathode active material is preferably present in a proportion of 1 to 50% by mass, particularly preferably 5 to 25% by mass, based on the total weight of the first and second cathode active materials.

[0065] The second cathode active material can be selected primarily on the criterion that the lithium intercalation rate is sufficiently fast. However, fast dynamics are usually associated with a lower specific energy of the second cathode active material. By lowering the weight ratio of the second cathode active material, sufficiently improved dynamics can be achieved without excessively reducing the overall specific energy achievable by the composite cathode active material.

[0066] The anode active material may be selected from the group consisting of carbonaceous materials, silicon, silicon dioxide, silicon alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys, and mixtures thereof. Preferably, the anode active material is selected from the group consisting of synthetic graphite, natural graphite, graphene, mesocarbon, doped carbon, hard carbon, soft carbon, fullerene, silicon-carbon composites, silicon, surface-coated silicon, silicon dioxide, silicon alloys, lithium, aluminum alloys, aluminum alloys, indium, tin alloys, cobalt alloys, and mixtures thereof.

[0067] In principle, all anodic active materials known from prior art are suitable, such as niobium pentoxide, titanium dioxide, and lithium titanate (Li4Ti5O). 12 Titanates such as ), tin dioxide, lithium, lithium alloys, and / or mixtures thereof are also suitable.

[0068] If the anode active material already contains lithium that does not participate in cyclization, i.e., lithium that is not active lithium, then according to the present invention, this ratio of lithium is not considered a component of pre-lithification. In other words, this ratio of lithium does not affect the degree of lithification b of the second active material.

[0069] In addition to the anode active material, the anode may have other components and additives such as carriers, binders, and / or conductivity enhancers. Any compound and material known in the prior art can be used as further components and additives.

[0070] In one embodiment, the anode active material is pre-lithified before the first discharge and / or charge step of the lithium-ion battery so that the assembled lithium-ion battery has a state of charge (SoC) in the range of 1-30%, preferably 3-25%, more preferably 5-20%.

[0071] The SoC indicates the usable capacity relative to the maximum capacity of the lithium-ion battery, and represents the capacity of the lithium-ion battery that can be easily measured, for example, through the voltage and / or current flow rate of the lithium-ion battery.

[0072] The amount of lithium that must be used for pre-lithiation of the anode active material to achieve a specific state of charge (SoC) before the first discharge and / or charge of a lithium-ion battery depends on whether or not the anode active material already has a SEI (Sectional Interval Intake) before the first discharge and / or charge. In such cases, the anode active material needs to be pre-lithified so that a sufficient amount of lithium is added for both SEI formation and the achievement of the corresponding capacity. The amount of lithium required for SEI formation can be estimated based on the anode active material used.

[0073] However, the SoC of a lithium-ion battery before the first discharge and / or charge process depends not only on the pre-lithification of the anode active material but also on the delithification of the composite cathode active material. The anode active material can be pre-lithified to at least the extent that any lithium missing in the composite cathode active material is compensated for. In particular, the anode active material can also be pre-lithified to the extent that there is an excess of lithium in the lithium-ion battery, while at the same time the SoC is present in the region before the first discharge and / or charge process of the lithium-ion battery.

[0074] The lithium-ion battery according to the present invention has a separator between the cathode and the anode, which separates the two electrodes from each other. The separator is permeable to lithium ions but inconductive to electrons.

[0075] Polymers can be used as separators and are selected from the group consisting of polyester, particularly polyethylene terephthalate; polyolefin, particularly polyethylene and / or polypropylene; polyacrylonitrile; polyvinylidene fluoride; polyvinylidene-hexafluoropropylene; polyetherimide; polyimide; aramid; polyether; polyetherketone; or mixtures thereof. Optionally, the separator may be additionally coated with a ceramic material, for example, Al2O3.

[0076] Furthermore, lithium-ion batteries have an electrolyte that conducts lithium ions, and can be either a solid electrolyte or a liquid electrolyte containing a solvent and at least one lithium-conducting salt dissolved therein, such as lithium hexafluorophosphate (LiPF6).

[0077] The solvent should preferably be inert. Examples of suitable solvents are organic solvents, such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate (FEC), sulfolane, 2-methyltetrahydrofuran, acetonitrile, and 1,3-dioxolane.

[0078] Ionic liquids can also be used as solvents. Such ionic liquids contain only ions. Particularly preferred cations that can be alkylated are imidazolium-cation, pyridinium-cation, pyrrolidinium-cation, guanidinium-cation, uronium-cation, thironium-cation, piperidinium-cation, morpholinium-cation, sulfonium-cation, ammonium-cation, and phosphonium-cation. Examples of usable anions are halide-ions, tetrafluoroborate-ions, trifluoroacetate-ions, triflate-ions, hexafluorophosphate-ions, phosphinate-ions, and tosylate-anions.

[0079] Examples of ionic liquids include N-methyl-N-propyl-piperidinium-bis(trifluoromethylsulfonyl)imide, N-methyl-N-butyl-pyrrolidinium-bis(trifluoromethylsulfonyl)imide, N-butyl-N-trimethyl-ammonium-bis(trifluoromethylsulfonyl)imide, triethylsulfonium-bis(trifluoromethylsulfonyl)imide, and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium-bis(trifluoromethylsulfonyl)imide.

[0080] In one embodiment, two or more of the above liquids can be used.

[0081] Preferred conductive salts are lithium salts that have an inert anion and are preferably non-toxic. Suitable lithium salts include, in particular, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and mixtures of these salts.

[0082] In the case of a liquid, the separator can be impregnated or moistened with a lithium salt electrolyte.

[0083] The lithium-ion battery according to the present invention can be provided particularly for automobiles or portable devices. Portable devices can be smartphones, power tools or electric tools, tablets or wearables.

[0084] The object of the present invention is also achieved by a method for manufacturing a lithium-ion battery comprising the following steps: firstly, a composite cathode active material is provided by mixing at least a first cathode active material and a second cathode active material, where the second cathode active material is a compound having an olivine structure. The first cathode active material has a degree of lithiation a, and the second cathode active material has a degree of lithiation b. The degree of lithiation b of the second cathode active material is lower than the degree of lithiation a of the first cathode active material. Next, the composite cathode active material is incorporated into the cathode, the anode active material is incorporated into the anode, and a lithium-ion battery is manufactured using the cathode and anode. Before or after incorporating the anode active material into the anode, the anode active material is pre-lithified.

[0085] The individual components of lithium-ion batteries are manufactured from the materials mentioned above.

[0086] Therefore, the lithium-ion battery described above can be obtained in particular by the method according to the present invention.

[0087] Anode active materials can be pre-lithified, in particular, by techniques known in the prior art for producing lithium intercalation compounds or alloys.

[0088] For example, a mixture of an anode active material and metallic lithium can be used. The mixture of anode active materials can then be stored for a period of up to two weeks, preferably up to one week, and particularly preferably up to five days. During this time, lithium can be intercalated (incorporated) into the anode active material, so that a pre-lithified anode active material is obtained.

[0089] In one embodiment, the anode active material can be pre-lithified by mixing it with a lithium precursor and then converting the lithium precursor to lithium.

[0090] In further embodiments, the anode active material and / or the anode can be pre-lithified by injecting lithium into the anode active material.

[0091] By storing the anode in an electrolyte for a predetermined time, for example, 2 minutes to 14 days, a stable SEI can be established on the anode.

[0092] Finally, pre-lithification of the anode active material can be performed by electrochemical treatment of the anode active material incorporated into the anode in a lithium-containing electrolyte. In this way, SEI can already be formed on the anode during pre-lithification. The SEI can be further completed by storing the anode in the electrolyte.

[0093] Other advantages and features of the present invention will become apparent from the following description and examples, and should not be understood in a limited sense.

[0094] Table 1 lists the substances and materials used in the examples.

[0095] [Table 1]

[0096] Example 1 (Reference Example) A mixture of 94% by mass of NMC 811, 3% by mass of PVdF, and 3% by mass of conductive carbon black is suspended in NMP at 20°C using a high-shear dissolution mixer. A uniform coating composition is obtained, spreading across an aluminum carrier foil rolled to a thickness of 15 μm. After peeling off the NMP, the basis weight is 22.0 mg / cm². 2 A composite cathode film was obtained.

[0097] An anode coating composition having the composition of 94% by mass of natural graphite, 2% by mass of SBR, 2% by mass of CMC, and 2% by mass of Super C65 is similarly prepared and applied to a 10 μm rolled copper support foil. The anode film thus produced has a basis weight of 12.2 mg / cm². 2 That is the case.

[0098] Anode having an anode film, separator (25 μm) made of polypropylene (PP), and liquid electrolyte (25 cm³) of a 1 M solution (3:7 w / w) of LiPF6 in EC / DMC. 2 An electrochemical cell having an active electrode region is used to assemble a cathode with a cathode film, which is then packed and sealed in a highly purified aluminum composite foil (thickness: 0.12 mm). A pouch cell with an external size of approximately 0.5 mm × 6.4 mm × 4.3 mm is obtained.

[0099] The cell is initially charged to 4.2V (C / 10), and then discharged to C / 10~2.8V.

[0100] The capacity during the first charge is 111mAh, and the capacity during the first discharge is 100mAh. As a result, approximately 10% of the total cell is lost during formation. This is equivalent to the approximately 10% loss expected when using natural graphite as the anode active material.

[0101] Example 2 (Lithium-ion battery according to the present invention) A mixture of 78.4% by mass of NMC 811, 15.6% by mass of FePO4, 3% by mass of PVdF, and 3% by mass of conductive carbon black was suspended in NMP at 20°C using a high-shear dissolution mixer. A uniform coating composition was obtained, spreading across an aluminum carrier foil rolled to a thickness of 15 μm. After removing the NMP, the basis weight was 21.8 mg / cm². 2 A cathode film was obtained.

[0102] The first cathode active material used, NMC 811, has a lithiumization degree of 1, while the second cathode active material used, FePO4, has a lithiumization degree b of 0.

[0103] An anode coating composition having the composition of 94% by mass of natural graphite, 2% by mass of SBR, 2% by mass of CMC, and 2% by mass of Super C65 is similarly prepared and applied to a 10 μm rolled copper support foil. The anode film thus produced has a basis weight of 12.2 mg / cm². 2 That is the case.

[0104] After pre-lithifying this anode film with 19mAh lithium, cell assembly is performed. From this, approximately 11mAh of lithium forms the SEI protective layer, and approximately 8mAh of lithium is intercalated into the graphite. As a result, the natural graphite is Li 0.08 The composition of C6 is such that it has a lithium degree γ of 0.08.

[0105] 20mAh lithium is equivalent to 0.75 mmol or 5.2 mg of lithium.

[0106] Using an anode with an anode membrane, a separator (25 μm), and an electrolyte of a 1 M solution of LiPF6 in EC / DMC (3:7 w / w), 25 cm 2 A cathode film is assembled into an electrochemical cell having an electrode region, and this is packed into aluminum composite foil (thickness: 0.12 mm) and sealed. A pouch cell with an outer shape of approximately 0.5 mm × 6.4 mm × 4.3 mm is obtained.

[0107] After weighing the electrolyte and final sealing of the cell according to the present invention, the opening voltage is approximately 2.9-3.5V, which is due to the potential difference between the partially delithified cathode and the pre-lithified anode. The nominal capacity of the lithium-ion battery is 100mAh, and the lithium-ion battery has a state of charge (SoC) of 8% immediately after manufacture.

[0108] The cell is initially charged to 4.2V (C / 10) and then discharged to C / 10 ~2.8V. After assembly and activation with the liquid electrolyte, the cell already has 8% SoC, so a charge of 92mAh is observed during further generation with C / 10, although the initial C / 10 discharge is 100mAh.

[0109] Therefore, the lithium-ion battery according to the present invention can achieve high capacity similar to that of the reference example.

[0110] Comparison of Examples The use of a composite cathode active material containing NMC 811 and FePO4 (Example 2) in the cathode of a lithium-ion battery reduces the use of the more expensive NMC 811 compared to the reference example. This invention demonstrates that the use of costly NMC 811 in cells can be reduced by 20.8% and replaced by the use of FePO4 instead.

[0111] Increase in basis weight of cathode film in Example 2 compared to the reference example (21.8 mg / cm²) 2 From 22.4 mg / cm³ 2 This is achieved by using different cathode compositions of FePO4 and pre-lithiumizing the anode to maintain the same reversible area capacity of the lithium-ion battery in the first discharge process. At the same time, it is possible to slightly reduce the total weight of the composite cathode active material while maintaining the same capacity battery.

[0112] The lithium-ion battery according to the present invention is not limited to graphite as the anode active material; anode active materials based on silicon or other anode active materials known in the prior art can also be advantageously used.

[0113] To manufacture lithium-ion batteries, an anode having a pre-lithified anode active material and a partially delithified composite cathode active material is used, so immediately after the manufacturing process and before the first discharge and / or charge process, the lithium-ion battery can already have a state of charge (SoC) in the range of 1-30%. This invention includes the following items. [Item 1] A lithium-ion battery having a cathode containing a composite cathode active material and an anode containing an anode active material. Here, the composite cathode active material includes at least a first and a second cathode active material, Here, the second cathode-active material is a compound having an olivine structure. The first cathode active material has a degree of lithiumization a, and the second cathode active material has a degree of lithiumization b. Here, prior to the first discharge and / or charge step of the lithium-ion battery, the degree of lithiumization b of the second cathode active material is lower than the degree of lithiumization a of the first cathode active material, and Herein, the anode active material is pre-lithified before the first discharge and / or charge step of the lithium-ion battery. [Item 2] The lithium-ion battery according to item 1, characterized in that the first cathode active material is selected from the group consisting of a layered oxide containing perlithiated oxide (OLO), a compound having an olivine structure, a compound having a spinel structure, and combinations thereof. [Item 3] A lithium-ion battery according to item 1 or 2, characterized in that the difference between the degree of lithiumization of the first cathode active material and the degree of lithiumization of the second cathode active material is 0.1 or more, preferably 0.5 or more. [Item 4] A lithium-ion battery according to any one of items 1 to 3, characterized in that the layered oxide contains nickel and cobalt, and is particularly a nickel-cobalt-manganese compound or a nickel-cobalt-aluminum compound. [Item 5] A lithium-ion battery according to any one of items 1 to 4, characterized in that the compound having an olivine structure in the first and / or second cathode active material includes an iron-based compound, an iron and manganese-based compound, or a cobalt and / or nickel-based compound. [Item 6] A lithium-ion battery according to any one of items 1 to 5, characterized in that, based on the total weight of the composite cathode active materials, the weight ratio of the second cathode active material is lower than the weight ratio of the first cathode active material. [Item 7] The lithium-ion battery according to any one of items 1 to 6, characterized in that the anode active material is selected from the group consisting of carbonaceous materials, silicon, silicon dioxide, silicon alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys, and mixtures thereof, preferably selected from the group consisting of synthetic graphite, natural graphite, graphene, mesocarbon, doped carbon, hard carbon, soft carbon, fullerene, silicon-carbon composite, silicon, surface-coated silicon, silicon dioxide, silicon alloys, lithium, aluminum alloys, indium, tin alloys, cobalt alloys, and mixtures thereof. [Item 8] A lithium-ion battery according to any one of items 1 to 7, characterized in that the anode active material is pre-lithified before the first discharge and / or charge step of the lithium-ion battery, such that the lithium-ion battery is in a state of charge (SoC) of 1 to 30%, preferably 3 to 25%, more preferably 5 to 20% before the first discharge and / or charge step of the lithium-ion battery. [Item 9] The following steps are included: - A step of providing a composite cathode active material by mixing a first cathode active material and a second cathode active material, wherein the second cathode active material is a compound having an olivine structure, the first cathode active material has a degree of lithium a, the second cathode active material has a degree of lithium b, and the degree of lithium b of the second cathode active material is lower than the degree of lithium a of the first cathode active material; - A process for providing an anode-active material; - A process of incorporating a composite cathode active material into the cathode and an anode active material into the anode; - The process of manufacturing a lithium-ion battery using a cathode and anode; Here, the anode active material is pre-lithified either before or after incorporating it into the anode. A method for manufacturing lithium-ion batteries. [Item 10] The method according to item 8, characterized by providing SEI to the anode before manufacturing a lithium-ion battery. [Item 11] The method according to item 8 or 9, characterized in that the lithium-ion battery is in a state of charge (SoC) in the range of 1 to 30% immediately after the manufacturing process and before the first discharge and / or charge process.

Claims

1. A lithium-ion battery having a cathode containing a composite cathode active material and an anode containing an anode active material. Here, the composite cathode active material includes at least a first and a second cathode active material, Here, the second cathode-active material is a compound having an olivine structure. The first cathode active material has a degree of lithiumization a, and the second cathode active material has a degree of lithiumization b. Here, the degree of lithiumization b of the second cathode active material is lower than the degree of lithiumization a of the first cathode active material, and Here, the anode active material is pre-lithified. The first cathode active material is selected from layered oxides containing perlithiated oxide (OLO), The aforementioned layered oxide is a nickel-cobalt-manganese compound. The compound having an olivine structure in the second cathode active material includes an iron-based compound, an iron and manganese-based compound, or a cobalt and / or nickel-based compound. The anode active material is selected from the group consisting of carbonaceous materials, silicon, silicon dioxide, silicon alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys, and mixtures thereof. The lithium-ion battery is characterized in that the anode active material is pre-lithified so that the lithium-ion battery is in a charge state (SoC) in the range of 1 to 30%.

2. The lithium-ion battery according to claim 1, characterized in that the difference between the degree of lithiumization of the first cathode active material and the degree of lithiumization of the second cathode active material is 0.1 or more.

3. A lithium-ion battery according to claim 1 or 2, characterized in that, based on the total weight of the composite cathode active materials, the weight ratio of the second cathode active material is lower than the weight ratio of the first cathode active material.

4. A lithium-ion battery according to any one of claims 1 to 3, characterized in that the anode active material is selected from the group consisting of synthetic graphite, natural graphite, graphene, mesocarbon, doped carbon, hard carbon, soft carbon, fullerene, silicon-carbon composite, silicon, surface-coated silicon, silicon dioxide, silicon alloy, lithium, aluminum alloy, indium, tin alloy, cobalt alloy, and mixtures thereof.

5. The following steps are included: - A step of providing a composite cathode active material by mixing a first cathode active material and a second cathode active material, wherein the second cathode active material is a compound having an olivine structure, the first cathode active material has a degree of lithium a, the second cathode active material has a degree of lithium b, and the degree of lithium b of the second cathode active material is lower than the degree of lithium a of the first cathode active material; - A process for providing an anode-active material; - A process of incorporating a composite cathode active material into the cathode and an anode active material into the anode; - The process of manufacturing a lithium-ion battery using a cathode and an anode; Here, the anode active material is pre-lithified either before or after incorporating it into the anode. The first cathode active material is selected from layered oxides containing perlithiated oxide (OLO), The aforementioned layered oxide is a nickel-cobalt-manganese compound. The compound having an olivine structure in the second cathode active material includes an iron-based compound, an iron and manganese-based compound, or a cobalt and / or nickel-based compound. The anode active material is selected from the group consisting of carbonaceous materials, silicon, silicon dioxide, silicon alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys, and mixtures thereof. A method for manufacturing a lithium-ion battery, characterized in that the lithium-ion battery is in a charged state (State of Charge) of 1 to 30% immediately after the manufacturing process.

6. The method according to claim 5, characterized in that SEI is provided to the anode before manufacturing the lithium-ion battery.

7. The lithium-ion battery according to any one of claims 1 to 4, wherein the second cathode active material is present in a proportion of 15.6 / 94 × 100 to 50% by mass, based on the total mass of the first and second cathode active materials.

8. The method according to any one of claims 5 to 6, wherein the second cathode active material is present in a proportion of 15.6 / 94 × 100 to 50% by mass, based on the total mass of the first and second cathode active materials.

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