Active material, positive electrode material, positive electrode, battery, battery device and method

Abstract

The present invention provides a positive electrode active material for a lithium ion battery. The components and contents of the positive electrode active material for the lithium ion battery are: 40% to 60% of a lithium iron phosphate material and 40% to 60% of a ternary material, all percentages being percentages by mass. The operating upper limit voltage and the operating lower limit voltage are respectively controlled within the range of the upper limit voltage being greater than or equal to 3.85V and less than or equal to 4.1V, and the operating lower limit voltage being greater than or equal to 2V and less than or equal to 2.8V. This takes into account the operating voltage ranges of the lithium iron phosphate material and the ternary material, enables the battery to achieve the advantages of ultra-long service life of the lithium iron phosphate and ternary material batteries, and at the same time, can achieve the advantages of overall battery safety.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to an active substance, a positive electrode material, a positive electrode, a battery, a battery device and a method. Background Art

[0002] Currently, lithium iron phosphate (LiFePO4) and ternary materials are the mainstream materials for commercial batteries. These two cathode material systems typically have different operating voltage ranges. Typically, LiFePO4 batteries operate in a voltage range of 2.5-3.65V or 2.0-3.8V, with an operating platform around 3.2V; ternary materials operate in a voltage range of 2.8-4.2V or 4.40V, with an operating voltage platform around 3.7V. Due to their different voltage ranges, the two material systems cannot generally be used together.

[0003] The theoretical gram capacity of the positive electrode made of lithium iron phosphate material is 170mAh / g. The gram capacity after the first formation and delithiation is usually around 155mAh / g, and its energy density is low.

[0004] The positive electrode made of ternary materials has a high specific capacity and a high discharge platform, so the battery cell of the system has a higher energy density, but its safety is not as good as that of lithium iron phosphate materials.

[0005] Therefore, it is necessary to develop a new active material, positive electrode material, positive electrode, battery, battery device and method to improve some of the above problems existing in the prior art. Summary of the Invention

[0006] The object of the present invention is to provide an active material, a positive electrode material, a positive electrode, a battery, a battery device and a method, which can take into account the service life, safety and energy density of the battery.

[0007] To achieve the above-mentioned object, the present invention provides a lithium-ion battery positive electrode active material, which is composed of a lithium iron phosphate material and a ternary material. The content of the lithium iron phosphate material and the ternary material is: 40% to 60% of the lithium iron phosphate material and 40% to 60% of the ternary material, and all percentages are weight percentages.

[0008] The beneficial effect of the lithium ion battery positive electrode active material provided by the present invention is that: by mixing lithium iron phosphate material and ternary material to obtain a lithium ion battery positive electrode active material with a content of 40% to 60% of lithium iron phosphate material and 40% to 60% of ternary material, by controlling the operating upper limit voltage and the operating lower limit voltage of the battery made of the lithium ion battery positive electrode active material to be greater than or equal to 3.85v and less than or equal to 4.1v, and the operating lower limit voltage value is greater than or equal to 2v and less than or equal to 2.8v, taking into account the operating voltage range of lithium iron phosphate material and ternary material, the electrolyte oxidation problem of lithium iron phosphate material is controllable within this operating voltage range and there are fewer side reactions at the positive electrode interface, which can enable the battery to achieve the advantages of high safety and long service life of lithium iron phosphate material battery. In addition, between the upper limit voltage and the lower limit voltage, the lattice volume change degree of the ternary material is low, which can effectively reduce the structural attenuation of the positive electrode material itself. At the same time, the partial introduction of the ternary material can ultimately achieve the advantage of high energy density of the battery.

[0009] Optionally, the ternary material includes any one of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

[0010] The present invention provides a lithium ion battery positive electrode material and a pole piece. The lithium ion battery positive electrode material comprises an adhesive, a conductive agent and the lithium ion battery positive electrode active material.

[0011] The present invention provides a lithium ion battery positive electrode plate, comprising a current collector and the lithium ion battery positive electrode material coated or filled on the current collector.

[0012] The present invention provides a lithium ion battery, which comprises a pole core and an electrolyte. The pole core comprises a positive electrode, a negative electrode and a separator located between the positive electrode and the negative electrode.

[0013] Optionally, the electrolyte includes an electrolyte additive, wherein the electrolyte additive includes any one of a boron-containing additive, a sulfur-containing additive, or a carbonate additive. This advantageously stabilizes the interface between the electrode and the electrolyte, or forms a passivation film on the positive electrode surface, thereby reducing electrode surface degradation and oxidative decomposition of the electrolyte. This reduces the risk of battery bulging caused by gas generation within the battery, thereby improving battery safety.

[0014] The present invention provides a lithium-ion battery device, comprising the lithium-ion battery and a voltage control module, wherein the voltage control module comprises:

[0015] a storage unit for storing preset voltage values, wherein the voltage values ​​include an upper limit of an operating voltage V1, and the upper limit of the operating voltage V1 is greater than or equal to 3.85V and less than or equal to 4.1V;

[0016] A monitoring unit, configured to monitor the operating voltage of the lithium-ion battery and generate an operating voltage value V0;

[0017] A control unit, wherein the control unit, the storage unit and the monitoring unit are electrically connected, and when V0 is greater than or equal to V1, the voltage control module controls the lithium-ion battery to stop charging.

[0018] Optionally, the voltage value includes a lower limit voltage value V2, the lower limit voltage value V2 is greater than or equal to 2V and less than or equal to 2.8V, and when V0 is less than or equal to V2, the voltage control module controls the lithium-ion battery to stop discharging.

[0019] The beneficial effect of a lithium-ion battery device provided by the present invention is that: the control unit determines whether the operating voltage of the lithium-ion battery obtained by the monitoring unit is within the range from the lower limit voltage value pre-stored in the storage unit to the upper limit of the operating voltage. 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 the lithium iron phosphate material and the ternary material to form the positive electrode material operates within a voltage range suitable for both of the above two materials, while taking advantage of the high safety and long service life of the lithium iron phosphate material battery and the high energy density of the ternary material battery.

[0020] The present invention provides a lithium-ion battery operating method, which is applied to the lithium-ion battery to make the operating voltage value V0 of the lithium-ion battery less than or equal to the operating voltage upper limit V1, and the operating voltage upper limit V1 is greater than or equal to 3.85V and less than or equal to 4.1V.

[0021] Optionally, the operating voltage value V0 of the lithium-ion battery is greater than or equal to a lower limit voltage value V2, and the lower limit voltage value V2 is greater than or equal to 2V and less than or equal to 2.8V.

[0022] The beneficial effect of a lithium-ion battery operating method provided by the present invention is that: by judging whether the operating voltage of the lithium-ion battery is within the range from the preset lower limit voltage value to the upper limit of the operating voltage, 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 the lithium iron phosphate material and the ternary material to form the positive electrode material operates within a voltage range suitable for both of the aforementioned two materials, while taking advantage of the high safety and long service life of the lithium iron phosphate material battery and the high energy density of the ternary material battery.

[0023] The present invention provides a method for replenishing active lithium in a lithium-ion battery. The method is applied to the lithium-ion battery to charge the lithium-ion battery and raise the voltage of the lithium-ion battery to an activation voltage V3, wherein the activation voltage V3 is greater than or equal to 4.2V and less than or equal to 4.4V. The method has the beneficial effect of effectively replenishing lithium by charging the lithium-ion battery and raising the battery voltage to a range of greater than or equal to 4.2V and less than or equal to 4.4V during subsequent use of the secondary battery during charge and discharge cycles, thereby effectively improving battery capacity and cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 4 is a structural block diagram of the lithium-ion battery device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the invention belongs. The words "including" and similar words used in this article mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0026] In the existing technology, batteries made of ternary materials and lithium iron phosphate materials have different operating voltage ranges. If the lithium iron phosphate battery is operated above its suitable operating voltage range, there will be problems with safety and reliability in storage and gas production. The ternary material battery cannot exert the advantages of its material capacity within a lower operating voltage range.

[0027] To address the problems of the prior art, embodiments of the present invention provide a positive electrode active material for a lithium-ion battery. The composition and content of the positive electrode active material for a lithium-ion battery are as follows: 40% to 60% lithium iron phosphate material and 40% to 60% ternary material, with all percentages being by mass. The materials can be physically mixed during slurry preparation by simultaneously adding the two materials to a slurry containing an NMP solvent.

[0028] In some specific embodiments of the present invention, the content of the components in the lithium-ion battery positive electrode activation material can be 40% lithium iron phosphate material and 60% ternary material; 45% lithium iron phosphate material and 55% ternary material; 50% lithium iron phosphate material and 50% ternary material; 55% lithium iron phosphate material and 45% ternary material; 60% lithium iron phosphate material and 40% ternary material.

[0029] In the specific embodiment of the present invention, the lithium iron phosphate material used has the chemical formula LiFePO4. The full battery capacity of this material is 144mAh / g under the normal voltage range of 2.5~4.1V, the material particle size D50 is 1.1μm, and the carbon coating content is 1.2%. The ternary material used is Ni83 material with a single crystal morphology, and the chemical formula is LiNi 0.83 Co 0.07 Mn 0.10 O2, the full battery gram capacity of this material is 185mAh / g in the voltage range of 2.5~4.1V, and the full battery gram capacity is 197mAh / g in the voltage range of 2.5~4.20V during activation. The material particle size D50 is 4.9um.

[0030] In some embodiments of the present invention, the lithium-ion battery positive electrode active material is used to manufacture positive electrode materials for lithium-ion batteries.

[0031] In some embodiments of the present invention, the above-mentioned lithium iron phosphate material LFP and the ternary Ni83 material are mixed to obtain a lithium ion battery positive electrode active material with a mass percentage of 40% to 60% lithium iron phosphate material and 40% to 60% ternary material. By controlling the operating upper limit voltage and the operating lower limit voltage of the battery made of the lithium ion battery positive electrode active material within the range of the upper limit voltage being greater than or equal to 3.85v and less than or equal to 4.1v, and the operating lower limit voltage being greater than or equal to 2v and less than or equal to 2.8v, respectively, the operating voltage ranges of the lithium iron phosphate material and the ternary material are taken into account, while giving play to the advantages of high safety and long service life of the lithium iron phosphate material battery and the advantages of high energy density of the ternary material battery.

[0032] Specifically, the dissolution of iron ions in lithium iron phosphate cathode materials can lead to direct attenuation of battery capacity and increased self-discharge, and can even damage the solid electrolyte interface membrane, significantly reducing battery cycle performance. Lithium-ion batteries made from such cathode active materials control their upper operating voltage limit within the range of 3.85V to 4.1V, making iron dissolution relatively controllable and reducing side reactions at the cathode interface. For ternary materials, controlling the voltage within 4.1V can effectively reduce the H2 / H3 phase transition, reduce the volume shrinkage of the material after delithiation, effectively reduce the possibility of oxygen release, and improve the overall stability and safety of the cathode.

[0033] 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.

[0034] In some specific embodiments of the present invention, the ternary material includes: LiNi 0.83 Co 0.07 Mn 0.10 O2、LiNi 0.75 Co 0.1 Mn 0.154 O2 or LiNi 0.65 Co 0.1 Mn 0.25 Any one of O2.

[0035] An embodiment of the present invention provides a lithium-ion battery positive electrode material, which includes a binder, a conductive agent, and the above-mentioned lithium-ion battery positive electrode active material.

[0036] In some embodiments of the present invention, a lithium iron phosphate material and a ternary material of model Ni83 are respectively made into slurries through a series of process steps such as mixing, dissolving, and dispersing, and the slurry made of the lithium iron phosphate material and the slurry made of the ternary material are mixed with each other to obtain the lithium-ion battery positive electrode material and the pole piece, wherein the mass ratio of the lithium iron phosphate material to the ternary material is (1~1.5):(1~1.5).

[0037] An embodiment of the present invention provides a lithium-ion battery positive electrode, which includes a current collector and the above-mentioned lithium-ion battery positive electrode material coated or filled on the current collector.

[0038] An embodiment of the present invention provides a lithium-ion battery, comprising a core and an electrolyte, wherein the core comprises the lithium-ion battery positive electrode, negative electrode and separator.

[0039] In some embodiments of the present invention, the electrolyte includes an electrolyte additive, and the lithium-ion battery made of the lithium-ion battery positive electrode active material controls its operating upper limit voltage within the range of 3.85V to 4.1V. The electrolyte oxidation problem is also relatively controllable. By adding the electrolyte additive 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.

[0040] In some embodiments of the present invention, the electrolyte includes an electrolyte additive, a lithium salt and a solvent; the lithium salt includes any one of lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide; the solvent includes any one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethyl acrylate or propylene carbonate; the electrolyte additive is any one of a boron-containing additive, a sulfur-containing additive or a carbonate additive.

[0041] In some specific embodiments of the present invention, the electrolyte additive includes any one of a boron-containing additive, a sulfur-containing additive, or a carbonate additive.

[0042] In some specific embodiments of the present invention, the electrolyte additive includes any one of propene sulfite (PS), 1,3-propenyl sultone (PST), vinyl ethylene glycol (VEC) or adiponitrile (SN) to suppress the gas generation problem of the lithium-ion battery during storage, but the present invention is not limited thereto.

[0043] Figure 1 4 is a structural block diagram of the lithium-ion battery device according to an embodiment of the present invention.

[0044] The embodiment of the present invention provides a lithium ion battery device, referring to Figure 1 , the lithium-ion battery device includes the above-mentioned lithium-ion battery 1 and the voltage control module 2;

[0045] The voltage control module 2 includes:

[0046] The storage unit 202 is used to store preset voltage values, including an upper limit voltage V1 and a lower limit voltage V2. Specifically, for the lithium-ion battery 1 described above, the upper limit voltage V1 is greater than or equal to 3.85V and less than or equal to 4.1V, and the lower limit voltage V2 is greater than or equal to 2V and less than or equal to 2.8V.

[0047] The monitoring unit 201 is used to monitor the operating voltage of the lithium-ion battery 1 and generate an operating voltage value V0;

[0048] 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.

[0049] 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.

[0050] In some specific embodiments of the present invention, the control unit 203 includes a comparator and a switch provided 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 operating voltage upper limit V1 and lower limit voltage values ​​V2 stored in the storage unit 202. If the operating voltage value V0 is not within the numerical range from the lower limit voltage value V2 to the upper limit voltage V1, the comparator disconnects the switch to stop charging and discharging the lithium-ion battery 1.

[0051] In some specific embodiments of the present invention, the operating voltage upper limit V1 may be 3.85v, 3.95v, 4.05v or 4.1v.

[0052] 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.

[0053] An embodiment of the present invention provides a lithium-ion battery operating method, which is applied to the above-mentioned lithium-ion battery, so that the operating voltage value V0 of the lithium-ion battery is less than or equal to the operating voltage upper limit V1 and greater than or equal to the lower limit voltage value V2, the upper limit voltage V1 is greater than or equal to 3.85V and less than or equal to 4.1V, and the lower limit voltage value V2 is greater than or equal to 2V and less than or equal to 2.8V.

[0054] It should be noted that the steps of the above-mentioned lithium-ion battery operating method correspond to the structure and principle of the above-mentioned lithium-ion battery device, and therefore will not be described in detail here.

[0055] An embodiment of the present invention provides a method for replenishing active lithium in a lithium-ion battery. The method is applied to the above-mentioned lithium-ion battery, and the lithium-ion battery is charged to increase the voltage of the lithium-ion battery to an activation voltage V3, wherein the activation voltage V3 is greater than or equal to 4.2V and less than or equal to 4.4V, so as to reduce the loss of active lithium that occurs during the charge and discharge cycle of the lithium-ion battery during subsequent use. The lithium-ion battery is effectively replenished with lithium based on the actual state of the battery and the amount of active lithium loss.

[0056] In some specific embodiments of the present invention, after the cell capacity has decayed to a certain extent, the decay capacity is C loss , the lithium-ion battery is charged, the voltage of the lithium-ion battery is increased to an activation voltage V3, the activation voltage V3 is greater than or equal to 4.2V and less than or equal to 4.4V, and the increased charging capacity from V1 to V3 is not greater than the attenuation capacity C loss .

[0057] Examples 1-5 provide lithium-ion batteries with different content ratios of lithium iron phosphate materials and ternary materials at different operating voltages. For specific content ratios and operating voltage values, see Table 1. Comparative Examples 1-2 provide lithium iron phosphate material batteries and ternary material batteries, see Table 1.

[0058] Table 1

[0059]

[0060] The lithium-ion batteries of Examples 1-5 and the batteries of Comparative Examples 1-2 were respectively subjected to service life tests. Referring to Table 2, the lithium-ion batteries with a mass percentage of 40% to 60% lithium iron phosphate material and 40% to 60% ternary material had a better cycle capacity retention rate than the ternary material battery, and a better low-temperature energy retention rate than the lithium iron phosphate material battery.

[0061] Table 2

[0062]

[0063] The compaction density tests were performed on the lithium-ion batteries of Examples 1, 2, and 5 and the batteries of Comparative Examples 1-2, respectively. Referring to Table 3, the lithium-ion batteries with a mass percentage of 40% to 60% lithium iron phosphate material and 40% to 60% ternary material have a higher compaction density than the lithium iron phosphate material battery, and the energy density is also improved overall compared to the pure lithium iron phosphate material battery.

[0064] Table 3

[0065]

[0066] Comparative Examples 3-5 provide batteries with different content ratios of lithium iron phosphate materials and ternary materials at different operating voltages. The lithium-ion batteries of Examples 1, 2, and 5 and the batteries of Comparative Examples 1 to 5 are subjected to nail penetration abuse tests. Referring to Table 4, the nail penetration pass rate of the lithium-ion batteries with a mass percentage of 40% to 60% lithium iron phosphate material and 40% to 60% ternary material is better than that of the ternary material battery.

[0067] Table 4

[0068]

[0069] While the 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 of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A lithium-ion battery device, characterized in that: include: Voltage control module and lithium-ion battery; The voltage control module includes: a storage unit for storing preset voltage values, wherein the voltage values ​​include an upper limit of an operating voltage V1, wherein 3.85V≤V1≤4.1V; a monitoring unit for monitoring the operating voltage of the lithium-ion battery and generating an operating voltage value V0; a control unit, wherein the control unit includes a comparator and a switch provided in an output circuit of the lithium-ion battery; the control unit, the storage unit, and the monitoring unit are electrically connected, and when V0 is greater than or equal to V1, the voltage control module controls the lithium-ion battery to stop charging; The activation voltage of the lithium-ion battery is V3, wherein 4.2 V≤V3≤4.4 V. The activation voltage V3 is used to charge the lithium-ion battery after the cell capacity decays. The voltage of the lithium-ion battery is increased to the activation voltage V3, and the decay capacity is Closs. The increased charging capacity from V1 to V3 is not greater than the decay capacity Closs. The lithium-ion battery comprises: a battery cell and an electrolyte, wherein the battery cell comprises a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, and the positive electrode comprises a current collector and a positive electrode material, wherein the positive electrode material is coated or filled on the current collector; The positive electrode material includes a binder, a conductive agent and a lithium-ion battery positive electrode active material. The components and content of the lithium-ion battery positive electrode active material are as follows: the proportion of lithium iron phosphate material is X, the proportion of ternary material is Y, X+Y=100%, wherein 40%≤X≤60%, 40%≤Y≤60%.

2. The lithium-ion battery device according to claim 1, wherein: The voltage value also includes a lower limit voltage value V2, wherein 2V≤V2≤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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