Active materials, cathode materials, cathodes, batteries, battery devices and methods

Abstract

This invention provides a positive electrode active material for lithium-ion batteries, composed of lithium iron phosphate material with an olivine structure and a ternary material with a layered structure. The content of the lithium iron phosphate material and the ternary material is as follows: lithium iron phosphate material 60%–99%, ternary material 1%–40%, all percentages are by mass. During normal battery use, the upper limit voltage range is controlled between 3.8 and 4.0V. When there is a certain capacity decay in the system, the battery voltage can be increased to a voltage range greater than or equal to 4.1V and less than or equal to 4.4V for activation treatment. Under the activation voltage, the lithium-rich ternary material can replenish lithium in the battery to address the problem of active lithium loss after battery aging, thereby improving the overall battery life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more particularly to an active material, a positive electrode material, a positive electrode, a battery, a battery device, and a method. Background Technology

[0002] During the initial formation of a lithium-ion battery, the electrode material and electrolyte react at the solid-liquid interface to form a solid electrolyte interface (SEI) film. The formation of the SEI film consumes lithium ions within the battery, resulting in capacity loss. Furthermore, during actual use, lithium-ion batteries also experience unavoidable and irreversible lithium loss.

[0003] Therefore, it is necessary to develop a new type of active material, cathode material, cathode, battery, battery device and method to improve some of the problems existing in the prior art. Summary of the Invention

[0004] The purpose of this invention is to provide an active material, a positive electrode material, a positive electrode, a battery, a battery device, and a method that can replenish lithium in a battery to address the problem of active lithium loss during formation or subsequent use.

[0005] To achieve the above objectives, the present invention provides a positive electrode active material for lithium-ion batteries, which is composed of lithium iron phosphate material and ternary material, wherein the content of lithium iron phosphate material and ternary material is: 60% to 99% lithium iron phosphate material and 1% to 40% ternary material, and all percentages are by mass.

[0006] The beneficial effects of the lithium-ion battery positive electrode active material provided by this invention are as follows: By introducing ternary materials into lithium iron phosphate materials, the lithium-ion battery positive electrode material is made with a mass percentage of 60% to 99% lithium iron phosphate material and 1% to 40% ternary materials. The ternary material lattice stores relatively abundant lithium. When the active lithium content decreases during the initial formation and subsequent use of the lithium-ion battery using this material, the lithium-ion battery is charged to increase the battery voltage to a voltage range of greater than or equal to 4.1V and less than or equal to 4.4V. Under the activation voltage, the lithium in the lithium-rich ternary material can replenish the lithium in the battery, thereby improving the battery capacity and battery cycle life.

[0007] Optionally, the ternary material includes either lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

[0008] The present invention provides a lithium-ion battery cathode material, the lithium-ion battery cathode material comprising a binder, a conductive agent and the lithium-ion battery cathode active material.

[0009] The present invention provides a lithium-ion battery positive electrode, comprising a current collector and the lithium-ion battery positive electrode material coated or filled on the current collector.

[0010] The present invention provides a lithium-ion battery, the lithium-ion battery comprising an electrode core and an electrolyte, the electrode core comprising a positive electrode, a negative electrode and a separator located between the positive electrode and the negative electrode.

[0011] Optionally, the electrolyte includes electrolyte additives, which are any one of boron-containing additives, sulfur-containing additives, or carbonate additives. The beneficial effects are: by using electrolyte additives to stabilize the interface between the electrode and the electrolyte, or to form a passivation film on the positive electrode surface, the degradation of the electrode surface and the oxidative decomposition of the electrolyte are reduced, thereby lowering the risk of battery swelling due to gas generation inside the battery and improving battery safety.

[0012] This invention provides a lithium-ion battery device, including the lithium-ion battery and a voltage control module, wherein the voltage control module includes:

[0013] A storage unit is used to store a preset voltage value, the voltage value including an upper limit voltage value V1, the upper limit voltage value V1 being greater than or equal to 3.8V and less than or equal to 4.0V;

[0014] The monitoring unit is used to monitor the operating voltage of the lithium-ion battery and generate the operating voltage value V0.

[0015] The control unit, the storage unit, and the monitoring unit are electrically connected. When V0 is greater than or equal to V1, the voltage control module controls the lithium-ion battery to stop charging.

[0016] Optionally, the voltage value includes a lower limit voltage value V2, which is greater than or equal to 2V and less than or equal to 2.8V. When V0 is less than or equal to V2, the voltage control module controls the lithium-ion battery to stop discharging.

[0017] The beneficial effects of the lithium-ion battery device provided by the present invention are as follows: the control unit determines whether the operating voltage of the lithium-ion battery obtained by the monitoring unit is within the range of the lower limit voltage value to the upper limit voltage value pre-stored in the storage unit. If it is not within the range, the lithium-ion battery is controlled to terminate charging and discharging, so that the lithium-ion battery formed by mixing lithium iron phosphate material and ternary material to form the positive electrode material can work within the voltage range suitable for both materials. At the same time, the advantages of high safety and long service life of lithium iron phosphate material battery and high energy density of ternary material battery are brought into play.

[0018] The present invention provides a method for operating a lithium-ion battery, which is applied to the lithium-ion battery such that the operating voltage value V0 of the lithium-ion battery is less than or equal to the upper limit voltage value V1, wherein the upper limit voltage value V1 is greater than or equal to 3.8V and less than or equal to 4.0V.

[0019] Optionally, the operating voltage value V0 of the lithium-ion battery is greater than or equal to the lower limit voltage value V2, wherein the lower limit voltage value V2 is greater than or equal to 2V and less than or equal to 2.8V.

[0020] The beneficial effects of the lithium-ion battery operating method provided by the present invention are as follows: by determining whether the operating voltage of the lithium-ion battery is within the range of the preset lower voltage limit to the upper voltage limit, if it is not within the range, the lithium-ion battery is controlled to terminate charging and discharging, so that the lithium-ion battery formed by mixing lithium iron phosphate material and ternary material to form the positive electrode material can work within the voltage range suitable for both materials, while giving full play to the advantages of high safety and long service life of lithium iron phosphate material battery and the advantages of lithium richness and high energy density of ternary material battery.

[0021] This invention provides a method for replenishing active lithium in a lithium-ion battery. The method involves charging the lithium-ion battery to increase its voltage to an activation voltage V3, where V3 is greater than or equal to 4.1V and less than or equal to 4.4V. The beneficial effect is that lithium-ion batteries using this material in secondary batteries experience active lithium loss during initial formation and subsequent use. By charging the lithium-ion battery and increasing its voltage to a range greater than or equal to 4.1V and less than or equal to 4.4V, the lithium in the lithium-rich ternary material at the activation voltage can replenish the lithium in the battery, thereby improving battery capacity and cycle life. Attached Figure Description

[0022] Figure 1 This is a structural block diagram of the lithium-ion battery device described in an embodiment of the present invention;

[0023] Figure 2 These are the battery capacity cycle decay curves for Examples 1, 2, 4 and Comparative Examples 1, 2, 3;

[0024] Figure 3 These are the battery capacity cycle decay curves for Examples 2, 3, 4, 5, and 6. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0026] Currently, commercially available batteries primarily use lithium iron phosphate (LFP) and ternary cathode materials. These two cathode material systems typically have different operating voltage ranges. Generally, LFP batteries operate within a voltage range of 2.5–3.65V or 2.0–3.8V, with a plateau of approximately 3.2V; ternary cathode materials operate within a voltage range of 2.8–4.2V or 4.40V, with a plateau of approximately 3.7V. Due to these different voltage ranges, the two material systems cannot be mixed.

[0027] In existing technologies, the active lithium content of lithium iron phosphate batteries decreases during the initial formation and subsequent use. To improve battery capacity, lithium replenishment is necessary. However, excessive lithium replenishment at one time can easily lead to lithium plating on the negative electrode, while insufficient replenishment will not achieve the desired effect. Therefore, targeted lithium replenishment is crucial.

[0028] In existing technologies, the theoretical lifespan of ternary lithium-ion batteries is much shorter than that of lithium iron phosphate batteries.

[0029] To address the problems existing in the prior art, this invention provides a lithium-ion positive electrode active material. The composition and content of the lithium-ion battery positive electrode active material are: 60% to 99% lithium iron phosphate material and 1% to 40% ternary material. All percentages are by mass.

[0030] In some embodiments of the present invention, the lithium-ion positive electrode active material can be physically mixed during the preparation of the slurry, by simultaneously adding lithium iron phosphate material and ternary material to the slurry containing NMP solvent.

[0031] In some specific embodiments of the present invention, the content of the components in the positive electrode activation material of the lithium-ion battery can be: 60% lithium iron phosphate material and 40% ternary material; 65% lithium iron phosphate material and 35% ternary material; 70% lithium iron phosphate material and 30% ternary material; 75% lithium iron phosphate material and 25% ternary material; 80% lithium iron phosphate material and 20% ternary material; 85% lithium iron phosphate material and 15% ternary material; 90% lithium iron phosphate material and 10% ternary material; 95% lithium iron phosphate material and 5% ternary material; or 99% lithium iron phosphate material and 1% ternary material.

[0032] In a specific embodiment of the present invention, the lithium iron phosphate material LFP used has the chemical formula LiFePO4. This material has a full-cell specific capacity of 143 mAh / g in a voltage range of 2.5–3.85 V, a particle size D50 of 1.1 μm, and a carbon coating content of 1.2%. The ternary material used is NCM712 material with a near-single-crystal morphology and the chemical formula LiNi. 0.7 Co 0.1 Mn 0.2 O2, this material has a full-cell capacity of 110 mAh / g in the voltage range of 2.5 to 3.85 V and a full-cell capacity of 188 mAh / g in the activation voltage range of 2.5 to 4.25 V. The material particle size D50 is 4.3 μm.

[0033] In some embodiments of the present invention, the material is composed of lithium iron phosphate with an olivine structure and a ternary material with a layered structure.

[0034] In some embodiments of the present invention, the ternary material is of type NCM712.

[0035] In some embodiments of the present invention, the lithium-ion battery positive electrode active material is used in the manufacture of positive electrode materials for lithium-ion batteries.

[0036] In some embodiments of the present invention, the lithium-ion battery made from the positive electrode active material of the lithium-ion battery introduces a lithium-rich ternary material into the lithium iron phosphate material. The ternary material can not only replenish lithium but also participate in the operation of the battery as an electrode positive electrode material, thereby improving the energy density of the battery positive electrode.

[0037] In some embodiments of the present invention, lithium iron phosphate material and ternary material are mixed to obtain a lithium-ion battery positive electrode active material with a mass percentage of 60% to 99% lithium iron phosphate material and 1% to 40% ternary material. By controlling the upper and lower operating voltages of the battery made from the lithium-ion battery positive electrode active material within the range of an upper operating voltage greater than or equal to 3.8V and less than or equal to 4.0V, and a lower operating voltage greater than or equal to 2V and less than or equal to 2.8V, the operating voltage ranges of both lithium iron phosphate material and ternary material are taken into account, while leveraging the advantages of high safety and long service life of lithium iron phosphate battery and the high energy density of ternary material battery.

[0038] Specifically, the dissolution of iron ions in lithium iron phosphate cathode materials can lead to a direct decrease in battery capacity and an increase in battery self-discharge, and may even damage the solid electrolyte interface film, thereby greatly reducing the battery's cycle performance. Lithium-ion batteries made from the positive electrode active material of the lithium-ion battery control their upper operating voltage within the range of 3.8V to 4.0V, where iron dissolution is relatively controllable and side reactions at the positive electrode interface are relatively few.

[0039] In some embodiments of the present invention, the ternary material includes any one of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

[0040] In some specific embodiments of the present invention, the ternary material includes: LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 or LiNi 0.8 Co 0.1 Mn 0.2 Any of the following: O2.

[0041] This invention provides a lithium-ion battery cathode material, which includes a binder, a conductive agent, and the aforementioned lithium-ion battery cathode active material.

[0042] In some embodiments of the present invention, lithium iron phosphate material and ternary material are respectively prepared into slurries through a series of processes such as mixing, dissolving and dispersing. The slurry made of lithium iron phosphate material and the slurry made of ternary material are mixed together to obtain the lithium-ion battery cathode material, wherein the mass ratio of lithium iron phosphate material to ternary material is (60-99%):(40-1%).

[0043] This invention provides a lithium-ion battery positive electrode, which includes a current collector and the aforementioned lithium-ion battery positive electrode material coated or filled on the current collector.

[0044] This invention provides a lithium-ion battery, which includes an electrode core and an electrolyte. The electrode core includes the aforementioned positive electrode, negative electrode, and separator of the lithium-ion battery.

[0045] In some embodiments of the present invention, the electrolyte includes electrolyte additives, and the lithium-ion battery made of the positive electrode active material controls its upper operating voltage within the range of 3.8V to 4.0V. The electrolyte oxidation problem is also relatively controllable. By adding the electrolyte additives to form a passivation film or polymer film on the positive electrode surface, the degradation of the electrode surface and the oxidative decomposition of the electrolyte are reduced.

[0046] In some embodiments of the present invention, the electrolyte comprises a lithium salt, a solvent, and an electrolyte additive; the lithium salt comprises either lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide; the solvent comprises any one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, ethyl acrylate, or propylene carbonate; and the electrolyte additive is any one of boron-containing additives, sulfur-containing additives, or carbonate additives.

[0047] In some specific embodiments of the present invention, the electrolyte additive is any one of propylene sulfite (PS), 1,3-propenyl-sulfonyl lactone (PST), vinyl ethylene ester (VEC) or adiponitrile (SN) to suppress the gas generation problem during lithium-ion battery storage, but the present invention is not limited thereto.

[0048] Figure 1 This is a structural block diagram of the lithium-ion battery device described in an embodiment of the present invention.

[0049] This invention provides a lithium-ion battery device, referring to... Figure 1 The lithium-ion battery device includes the lithium-ion battery 1 and the voltage control module 2 described above.

[0050] The voltage control module 2 includes:

[0051] Storage unit 202 is used to store preset voltage values, including an upper limit voltage value V1 and a lower limit voltage value V2; specifically, for the lithium-ion battery 1 mentioned above, the upper limit voltage value V1 is greater than or equal to 3.8V and less than or equal to 4.0V, and the lower limit voltage value V2 is greater than or equal to 2V and less than or equal to 2.8V.

[0052] Monitoring unit 201 is used to monitor the operating voltage of the lithium-ion battery 1 and generate the operating voltage value V0;

[0053] The control unit 203, the storage unit 202 and the monitoring unit 201 are electrically connected. When V0 is greater than or equal to V1 or when V0 is less than or equal to V2, the voltage control module 2 controls the lithium-ion battery 1 to stop charging and discharging.

[0054] In some specific embodiments of this aspect, the monitoring unit 201 includes a battery voltage monitoring circuit directly connected to the lithium-ion battery 1 to obtain the voltage of the lithium-ion battery.

[0055] In some specific embodiments of the present invention, the control unit 203 includes a comparator and a switch disposed in the output circuit of the lithium-ion battery 1. The comparator receives the operating voltage value V0 from the monitoring unit 201 and compares it with the preset upper limit voltage value V1 and lower limit voltage value V2 stored in the storage unit 202. If the operating voltage value V0 is not within the range of the lower limit voltage value V2 to the upper limit voltage value V1, the comparator disconnects the switch to stop the lithium-ion battery 1 from charging and discharging.

[0056] In some specific embodiments of the present invention, the upper limit voltage value V1 can be 3.85V, 3.95V, or 4.0V.

[0057] In some specific embodiments of the present invention, the lower limit voltage value V2 can be 2V, 2.2V, 2.4V, 2.6V, 2.6V or 2.8V.

[0058] This invention provides a lithium-ion battery operating method applied to the aforementioned lithium-ion battery, wherein the operating voltage value V0 of the lithium-ion battery is less than or equal to the upper limit voltage value V1 and greater than or equal to the lower limit voltage value V2, wherein the upper limit voltage value V1 is greater than or equal to 3.8V and less than or equal to 4.0V, and the lower limit voltage value V2 is greater than or equal to 2V and less than or equal to 2.8V.

[0059] It should be noted that the steps of the above-described lithium-ion battery working method correspond to the structure and principle of the above-described lithium-ion battery device, so they will not be repeated here.

[0060] This invention provides a method for replenishing active lithium in a lithium-ion battery. Applied to the aforementioned lithium-ion battery, the method involves charging the lithium-ion battery to increase its voltage to an activation voltage V3, where V3 is greater than or equal to 4.1V and less than or equal to 4.4V. This improves the reduction of active lithium loss during charge-discharge cycles in subsequent use of the lithium-ion battery. Based on the actual state of the battery and the amount of active lithium loss, the method effectively replenishes lithium in the lithium-ion battery.

[0061] In some embodiments of the present invention, after a certain degree of capacity decay in the battery cell, the decay capacity is C. loss When charging the aforementioned lithium-ion battery, the voltage of the lithium-ion battery is increased to the activation voltage V3, wherein the activation voltage V3 is greater than or equal to 4.1V and less than or equal to 4.4V, and the increase in charging capacity from V1 to V3 is not greater than the capacity degradation C. loss .

[0062] Examples 1-6 provide lithium-ion batteries with a ratio range of 60-90% lithium iron phosphate material and 1%-40% ternary material. The specific content ratios and voltage values ​​are shown in Table 1. Comparative Examples 1-3 provide batteries with a ternary material ratio of 0.5% and a lithium iron phosphate material ratio of 99.5%, a lithium iron phosphate material battery, and a ternary material battery, respectively, as shown in Table 1.

[0063] Table 1

[0064] Comparative Example 1 99.5％ 0.5％ 2.0-4V / Example 1 99％ 1％ 2.0-4V / Example 2 90％ 10％ 2.0-4V 4.25V Example 3 90％ 10％ 2.0-4V Not activated Example 4 80％ 20％ 2.0-4V 4.25V Example 5 70％ 30％ 2.0-4V 4.25V Example 6 60％ 40％ 2.0-4V 4.25V Comparative Example 2 100％ 0％ 2.0-4V / Comparative Example 3 0 100％ 2.5-4.25V /

[0065] Figure 2 These are the battery capacity cycle decay curves for Examples 1, 2, 4 and Comparative Examples 1, 2, 3; Figure 3 These are the battery capacity cycle decay curves for Examples 2, 3, 4, 5, and 6.

[0066] The lifespan of the lithium-ion batteries described in Examples 1-6 and the batteries in Comparative Examples 1-3 were tested respectively. See [link to relevant documentation]. Figure 2 and Figure 3 The lithium-ion battery exhibits slow battery life degradation within its normal operating voltage range of 2.0–4V. When the battery system ages, i.e., after some active lithium has been consumed, the excess lithium can be released by recharging to increase the upper operating voltage, thereby restoring capacity and extending cycle life. The cycle capacity retention rate of this lithium-ion battery is superior to that of ternary lithium batteries and lithium iron phosphate batteries. Furthermore, experiments show that a ternary lithium content of less than 1% has no significant effect on battery life.

[0067] refer to Figure 3 Comparing Examples 3 and 4 reveals that after a certain degree of degradation during cycling, high-voltage activation treatment of the battery can achieve the corresponding capacity recovery, significantly improving the cell's cycle life. Comparing Examples 1-6 shows that as the proportion of ternary materials increases, the cycle life initially improves, but then decreases somewhat. This indicates that the improvement in cycle life is related to the increased proportion of lithium-rich ternary materials. As the proportion of ternary materials further increases, the degradation of side reactions in the cathode and electrolyte also increases, leading to a corresponding decrease in cycle life.

[0068] The compaction density of the lithium-ion batteries in Examples 1, 2, 3, and 4 and the batteries in Comparative Examples 2 and 3 were tested respectively. As shown in Table 2, the compaction density of the lithium-ion batteries was higher than that of the lithium iron phosphate battery in Comparative Example 2.

[0069] Table 2

[0070]

[0071] Low-temperature energy retention rate tests were conducted on the lithium-ion batteries of Examples 1, 2, 3, and 4, and the batteries of Comparative Examples 2 and 3, respectively. See Table 3. The energy retention rate of the lithium-ion batteries at -20 degrees Celsius was better than that of the lithium iron phosphate battery in Comparative Example 2.

[0072] Table 3

[0073]

[0074] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A lithium-ion battery device, characterized in that, Includes a voltage control module and a lithium-ion battery; The voltage control module includes: A storage unit is used to store a preset voltage value, the voltage value including an upper limit voltage value V1, the upper limit voltage value V1 being greater than or equal to 3.8V and less than or equal to 4.0V; The monitoring unit is used to monitor the operating voltage of the lithium-ion battery and generate the operating voltage value V0. The control unit includes a comparator and a switch disposed in the output circuit of the lithium-ion battery; the control unit, the storage unit, and the monitoring unit are electrically connected; when V0 is greater than or equal to V1, the voltage control module controls the lithium-ion battery to stop charging. The lithium-ion battery includes: an electrode core and an electrolyte. The electrode core includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes. The positive electrode includes: a current collector and a lithium-ion battery positive electrode material. The lithium-ion battery positive electrode material is coated or filled on the current collector. The lithium-ion battery positive electrode material includes a binder, a conductive agent, and a lithium-ion battery positive electrode active material. The composition and content of the lithium-ion battery positive electrode active material are: 60%~99% lithium iron phosphate material and 1%~40% ternary material, where the percentages are by mass. The activation voltage of the lithium-ion battery is V3, where 4.1V ≤ V3 ≤ 4.4V. This activation voltage V3 is used to charge the lithium-ion battery after its capacity has decayed, increasing the battery voltage to V3. The decayed capacity is C. loss The increase in charging capacity from segment V1 to segment V3 is not greater than the attenuation capacity C. loss .

2. The lithium-ion battery device according to claim 1, characterized in that, The voltage value includes a lower limit voltage value V2, which is greater than or equal to 2V and less than or equal to 2.8V. When V0 is less than or equal to V2, the voltage control module controls the lithium-ion battery to stop discharging.

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