Positive electrode, lithium battery and device

Abstract

Positive electrode, lithium battery, and apparatus. The positive electrode includes a positive electrode current collector and a lithium replenishment layer and a positive electrode material layer sequentially laminated on at least one side of the positive electrode current collector. The lithium replenishment layer contains a first positive electrode lithium replenishment, and the positive electrode material layer contains a positive electrode active material and a second positive electrode lithium replenishment. The initial Coulomb efficiency of the first positive electrode lithium replenishment is less than 30%, and the second positive electrode lithium replenishment can decompose to generate gas.

Description

[Technical Field]

[0001] This application claims priority under Chinese Patent Application No. 202311444331.X, filed with the China National Intellectual Property Administration on 31 October 2023 under the title "POSITIVE ELECTRODE, LITHIUM BATTERY, AND APPARATUS," which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to the technical field of lithium-ion batteries, and more specifically to cathodes, lithium batteries, and devices. [Background technology]

[0003] During the initial charging of a lithium battery, a solid electrolyte interface (SEI) forms on the negative electrode surface, consuming active lithium ions within the battery and reducing its initial Coulombic efficiency and energy density. To compensate for the irreversible consumption of active lithium during initial charging, the industry employs the practice of pre-adding a lithium replenisher that can supply active lithium ions to the lithium battery. Lithium replenishment methods for batteries are generally divided into positive electrode lithium replenishment methods and negative electrode lithium replenishment methods. Compared to negative electrode lithium replenishment methods, which involve pre-lithification of the negative electrode using highly chemically active metallic lithium, positive electrode lithium replenishment methods are safer and have better compatibility with existing battery manufacturing processes.

[0004] Cathode lithium replenishment technology replenishes active lithium ions in lithium batteries by introducing a cathode lithium replenisher into the battery's positive electrode that undergoes an irreversible delithiation reaction during the initial charge. Cathode lithium replenishers are mainly divided into two types. The first type is a lithium-rich material with low initial Coulomb efficiency, which, after lithium ions are extracted at a specific voltage, leaves part of the main structure or delithiation products on the positive electrode side. The second type is a sacrificial lithium replenisher that can decompose at a specific voltage to produce lithium ions and gas. However, these two types of cathode lithium replenishers have specific problems when used individually in batteries. For example, when using the first type of cathode lithium replenisher, the positive electrode active material is mixed with the first type of cathode lithium replenisher. This increases the liquid phase diffusion resistance of the positive electrode, further degrading the battery's output characteristics. For example, if a positive electrode coating formed by mixing a second type of positive electrode lithium replenisher with a positive electrode active material is in direct contact with the positive electrode current collector, the gas generated by the decomposition of the positive electrode lithium replenisher may not be released smoothly, and residual gas may increase the impedance of the battery, potentially degrading the battery's output characteristics.

[0005] Therefore, it is necessary to develop technical means that can achieve both a good positive electrode lithium replenishment effect and good battery output characteristics. [Overview of the project] [Means for solving the problem]

[0006] From this perspective, this disclosure shows that by simultaneously introducing a lithium replenishment material with low initial coulomb efficiency and a sacrificial lithium replenisher that can decompose to generate gas into the positive electrode of a battery, and by appropriately positioning the lithium replenishment material and the sacrificial lithium replenisher, the battery can achieve both high battery energy density and excellent battery output characteristics.

[0007] Specifically, according to a first aspect of the present disclosure, a positive electrode is provided, the positive electrode comprising a positive electrode current collector and a lithium replenishment layer and a positive electrode material layer sequentially laminated on at least one side of the positive electrode current collector, wherein the lithium replenishment layer comprises a first positive electrode lithium replenishment, and the positive electrode material layer comprises a positive electrode active material and a second positive electrode lithium replenishment, the initial Coulomb efficiency of the first positive electrode lithium replenishment being less than 30%, and the second positive electrode lithium replenishment being able to decompose to generate gas.

[0008] In the positive electrode provided in this embodiment of the present disclosure, the first positive electrode lithium replenisher and the second positive electrode lithium replenisher are introduced simultaneously and arranged in layers as described above, thereby reducing the problems of increased battery impedance and reduced output characteristics that occur when the first or second positive electrode lithium replenisher is used alone, and the battery can achieve both high energy density and good output characteristics.

[0009] In possible embodiments, the first cathode lithium replenisher comprises one or more of Li6CoO4, Li2MoO3, Li5FeO4, Li6MnO4, Li2NiO2, Li2CuO2, Li3PO4, Li4SiO4, Li2SiO3, Li3VO4, Li2VO3, Li5ReO6, Li2RuO3, Li2MnO3, Li2MoO3, Li2S, and LiF.

[0010] In possible embodiments, the first positive electrode lithium replenisher has a conductive coating layer.

[0011] In possible embodiments, the lithium replenishment layer comprises, by mass percentage, the following components: 50% to 90% of a first positive electrode lithium replenisher, 0% to 40% of a second positive electrode active material, 0.5% to 10% of a binder, and 0.5% to 10% of a conductive agent.

[0012] In possible embodiments, the second cathode lithium replenisher comprises one or more of Li2CO3, Li3N, Li2O2, Li2O, Li2C2O4, Li2C4O4, Li2C3O5, and Li2C4O6.

[0013] In possible embodiments, in the positive electrode material layer, the Dv50 of the second positive electrode lithium replenisher is 20 to 500 nm, and the DV50 of the positive electrode active material is 0.2 to 5 μm.

[0014] In possible embodiments, the total mass of the second cathode lithium replenisher in the cathode material layer is 0.5% to 5% of the total mass of the cathode active material.

[0015] In possible embodiments, the ratio of the lithium replenishment capacity provided by the first positive electrode lithium replenisher to the lithium replenishment capacity provided by the second positive electrode lithium replenisher is (0.2 to 2):1.

[0016] In possible embodiments, the single-sided density of the positive electrode material layer is greater than the single-sided density of the lithium replenishment layer.

[0017] In possible embodiments, the single-sided surface density of the lithium replenishment layer is 0.5 to 50 g / m². 2 That is the case.

[0018] In possible embodiments, the single-sided surface density of the lithium-replenished layer is 0.5 to 20 g / m². 2 That is the case.

[0019] In possible embodiments, the lithium replenishment layer has a single-sided thickness of 0.1 to 100 μm.

[0020] In possible embodiments, the lithium replenishment layer has a single-sided thickness of 0.5 to 10 μm.

[0021] In possible embodiments, the positive electrode material layer comprises n positive electrode material sublayers (n≧2), and the mass ratio of the second positive electrode lithium replenisher to the positive electrode active material in each positive electrode material sublayer tends to increase in the direction from the positive electrode current collector to the positive electrode material layer.

[0022] In a possible embodiment, the positive electrode material layer comprises n positive electrode material sublayers (n≧2), and in the direction from the positive electrode current collector toward the positive electrode material layer, the mass ratio of the second lithium replenishing agent for positive electrode to the positive electrode active material in each positive electrode material sublayer increases sequentially layer by layer.

[0023] In a possible embodiment, among the n positive electrode material sublayers, at least two adjacent layers satisfy the following relationship: A m / (D m / D m-1 )-A m-1 ≧5% Here, A m-1 is the mass ratio of the second positive electrode lithium replenishing agent in the (m-1)-th positive electrode material sublayer to the total amount of the second positive electrode lithium replenishing agent in the positive electrode material layer, A m is the mass ratio of the second positive electrode lithium replenishing agent in the m-th positive electrode material sublayer to the total amount of the second positive electrode lithium replenishing agent in the positive electrode material layer, D m-1 is the thickness of the (m-1)-th positive electrode material sublayer, D m is the thickness of the m-th positive electrode material sublayer, m is any integer in the range from 2 to n, and on the same side of the positive electrode current collector, the (m-1)-th positive electrode material sublayer is arranged closer to the positive electrode current collector than the m-th positive electrode material sublayer.

[0024] In a possible embodiment, among the n positive electrode material sublayers, any two adjacent positive electrode material sublayers satisfy A m / (D m / D m-1 )-A m-1 ≧5%.

[0025] In a possible embodiment, the mass percentage of the positive electrode active material in each positive electrode material sublayer is greater than 80%.

[0026] According to a second aspect, the present disclosure provides a lithium battery comprising the positive electrode according to the first aspect of the present disclosure.

[0027] By employing the above-described positive electrode, lithium batteries can achieve both high energy density and excellent power output characteristics.

[0028] According to a third aspect, the Disclosure provides an apparatus having a lithium battery according to a second aspect of the Disclosure, which is an electrical device or an energy storage system. [Brief explanation of the drawing]

[0029] [Figure 1] Figure 1 is a structural diagram of a positive electrode according to an embodiment of this disclosure. [Figure 2] Figure 2 is a diagram of another structure of the positive electrode according to an embodiment of this disclosure. [Figure 3] Figure 3 is a structural diagram of a lithium battery according to an embodiment of the present disclosure. [Figure 4] Figure 4 is a block diagram of the structure of the apparatus according to an embodiment of the present disclosure. [Modes for carrying out the invention]

[0030] Referring to the attached diagrams, the technical solutions in the embodiments of this disclosure will be described below.

[0031] Refer to Figures 1 and 2. One embodiment of the present disclosure provides a positive electrode 100 comprising a positive electrode current collector 10 and a lithium replenishment layer 20 and a positive electrode material layer 30 sequentially laminated on at least one side of the positive electrode current collector 10. That is, on the same side of the positive electrode current collector 10, the lithium replenishment layer 20 is positioned closer to the positive electrode current collector 10, and the positive electrode material layer 30 is positioned further away from the positive electrode current collector 10 than the lithium replenishment layer 20. The lithium replenishment layer 20 comprises a first positive electrode lithium replenishment 201, and the positive electrode material layer 30 comprises a positive electrode active material 302 and a second positive electrode lithium replenishment 301. The initial Coulomb efficiency of the first positive electrode lithium replenishment 201 is less than 30%. The second positive electrode lithium replenishment 301 is capable of decomposing to release lithium ions and generate gas.

[0032] The aforementioned positive electrode 100 contains two types of positive electrode lithium replenishers simultaneously. The second positive electrode lithium replenisher 301, which can decompose to generate gas, is placed in the positive electrode material layer 30 spaced apart from the positive electrode current collector 10, while the first positive electrode lithium replenisher 201, which has a low initial Coulomb efficiency, is placed in the lithium replenishment layer 20 close to the positive electrode current collector 10. On the other hand, compared to a conventional positive electrode having only a positive electrode material layer 30, when the total lithium replenishment capacity is the same, the positive electrode of this disclosure contains two types of positive electrode lithium replenishers simultaneously, so the amount of the second positive electrode lithium replenisher 301 added is reduced, and consequently the amount of gas generated by the decomposition of the second positive electrode lithium replenisher 301 is also reduced. On the other hand, since the positive electrode material layer 30 containing the second positive electrode lithium replenisher 301 is located on the surface of the positive electrode 100 and away from the positive electrode current collector 10, the gas discharge path released by the decomposition of the second positive electrode lithium replenisher 301 is shortened, making gas discharge easier. As a result, during the decomposition process of the second positive electrode lithium replenisher 301, the polarization of the battery is reduced, ensuring the decomposition rate and utilization rate of the second positive electrode lithium replenisher 301, as well as ensuring the lithium replenishment efficiency of the first positive electrode lithium replenisher 201. In addition, the amount of gas remaining in the positive electrode 100 is reduced, the battery impedance is lowered, and the output characteristics of the battery are improved.

[0033] The typical particle size of the first positive electrode lithium replenisher 201 is generally in the range of 3 to 10 μm. In conventional positive electrodes having only a mixed layer containing the first positive electrode lithium replenisher 201 and the positive electrode active material, the particle size compatibility between the first positive electrode lithium replenisher 201 and the positive electrode active material 302 in the mixed layer is not high, and a dense laminated structure cannot usually be formed, reducing the compressive density of the positive electrode sheet and adversely affecting the energy density of the battery. Compared to conventional positive electrodes having only a mixed layer containing the first positive electrode lithium replenisher 201 and the positive electrode active material, the positive electrode 100 of this disclosure simultaneously comprises two types of positive electrode lithium replenishers under the condition that the total amount of lithium replenishment is the same, reducing the amount of the first positive electrode lithium replenisher 201 added, and as a result, the effect of the first positive electrode lithium replenisher 201 on reducing the compressive density of the positive electrode is also reduced. Furthermore, the first positive electrode lithium replenisher 201 generally has good conductivity after releasing active lithium ions. Placing the first positive electrode lithium replenisher 201 in the lithium replenishment layer 20 that is in contact with the positive electrode current collector 10 also contributes to ensuring the formation of a good conductive network throughout the positive electrode. As a result, the utilization rate of the lithium replenisher is improved, the battery impedance is reduced, and the output characteristics of the battery are improved.

[0034] Therefore, in the positive electrode 100 according to this embodiment of the disclosure, by arranging the first positive electrode lithium replenisher and the second positive electrode lithium replenisher in layers as described above, a synergistic effect can be obtained between the two types of lithium replenishers and between the two types of lithium replenishers and the positive electrode active material of the battery. As a result, the utilization rate of the two types of lithium replenishers is improved, the energy density of the battery is improved, the battery impedance is reduced, and the output characteristics are improved.

[0035] It should be noted that the second positive electrode lithium replenisher 301 can decompose and release lithium ions. After releasing lithium ions and gas, the main structure of the second positive electrode lithium replenisher 301 is absent, and lithium ions cannot be reinserted into the second positive electrode lithium replenisher 301. This type of lithium replenisher is sometimes called a sacrificial lithium replenisher. Therefore, the concept of "initial Coulomb efficiency" does not apply to this type of positive electrode lithium replenisher. However, the first positive electrode lithium replenisher 201 can release lithium ions at a relatively high voltage, and a part of the main structure or delithiation products remain in the positive electrode 100, giving it a certain ability to reinsert lithium ions, although this ability is relatively low. That is, its reversible lithium ion release / insertion ability is low, and its initial Coulomb efficiency is low (less than 30%), which is significantly lower than the initial Coulomb efficiency of the positive electrode active material 302 (generally over 60%). The initial Coulomb efficiency of the first positive electrode lithium replenisher 201 can be determined from the ratio of the initial discharge capacity to the initial charge capacity in a coin cell manufactured using the first positive electrode lithium replenisher 201 as the positive electrode active material 302. Specifically, the measurement conditions for the initial Coulomb efficiency of the first positive electrode lithium replenisher 201 are as follows: the coin cell is of type CR2032, the positive electrode foil is carbon-coated aluminum foil, the composition of the positive electrode is first positive electrode lithium replenisher 201:conductive agent:binder = 8:1:1 (mass ratio), the negative electrode is a metallic lithium sheet, the separator is a 14 μm thick PP separator, and the electrolyte is 1 M LiPF6 dissolved in a mixed solvent of EC / DMC / DEC / EMC = 1:1:1:1 (volume ratio). The electrolyte is then charged to 4.5 V at 0.1 C and discharged to 2.0 V at 0.1 C. The initial discharge capacity / initial charge capacity at this time is the initial Coulomb efficiency.

[0036] In embodiments of this disclosure, the first cathode lithium replenisher 201 may include, but is not limited to, one or more of Li6CoO4, Li2MoO3, Li5FeO4, Li6MnO4, Li2NiO2, Li2CuO2, Li3PO4, Li4SiO4, Li2SiO3, Li3VO4, Li2VO3, Li5ReO6, Li2RuO3, Li2MnO3, Li2MoO3, Li2S, and LiF. In embodiments of this disclosure, but is not limited to, the second cathode lithium replenisher 301 may include, but is not limited to, one or more of Li2CO3, Li3N, Li2O2, Li2O, Li2C2O4, Li2C4O4, Li2C3O5, and Li2C4O6.

[0037] The surface of the first positive electrode lithium replenisher 201 may or may not have a conductive coating layer. In some embodiments, the surface of the first positive electrode lithium replenisher 201 has a conductive coating layer. In this case, the conductivity of the first positive electrode lithium replenisher 201 is good, which contributes to ensuring the formation of a good conductive network in the lithium replenishment layer 20, thereby contributing to a reduction in battery impedance and an improvement in the battery's output characteristics.

[0038] In some embodiments of this disclosure, the positive electrode active material 302 in the positive electrode material layer 30 can be selected from one or more of the following: lithium iron phosphate, lithium iron manganese phosphate, lithium manganate, lithium cobalt oxide, nickel manganese lithium oxide, cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium-rich lithium manganate material, etc. These positive electrode active materials 302 may or may not be doped, may be doped, may be modified, and may or may not have a conductive coating layer on their surface. Generally, lithium iron phosphate and lithium iron manganese phosphate materials have a conductive carbon coating layer.

[0039] In some embodiments of this disclosure, in the positive electrode material layer 30, the particle size of the second positive electrode lithium replenisher 301 is smaller than the average particle size of the positive electrode active material 302. In some embodiments of this disclosure, in the positive electrode material layer 30, the Dv50 of the second positive electrode lithium replenisher 301 is 20 to 500 nm, and the Dv50 of the positive electrode active material 302 is 0.2 to 5 μm. As a result, the second positive electrode lithium replenisher 301, which has a relatively small particle size, and the positive electrode active material 302, which has a relatively large particle size, are arranged in the same layer, increasing the particle size compatibility between the two and enabling the formation of a dense laminated structure, thus preventing a decrease in the compressive density and energy density of the positive electrode 100. In addition, the second positive electrode lithium replenisher 301 that satisfies the particle size range can decompose and release active lithium, and then form appropriate pore sizes, so that the positive electrode material layer 30 has an appropriate pore structure, contributing to a reduction in the overall impedance of the battery and an improvement in output characteristics. Dv50 refers to a particle size where the cumulative volume fraction reaches 50% in the particle size distribution based on particle volume.

[0040] In this disclosure, the lithium replenishment layer 20 may or may not contain the positive electrode active material 302. In embodiments of this disclosure, the lithium replenishment layer 20 may contain, by mass percentage, the following components: first positive electrode lithium replenishment 201 50% to 90%, second positive electrode active material 0% to 40%, binder 0.5% to 10%, and conductive agent 0.5% to 10%. The range of selection for the second positive electrode active material can be found by referring to the above description of the positive electrode active material 302 in the positive electrode material layer 30 in this disclosure. The second positive electrode active material may be the same as or different from the positive electrode active material 302 in the positive electrode material layer 30. Specifically, the mass percentage of the first positive electrode lithium replenishment 201 in the lithium replenishment layer 20 may be 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%, etc. Furthermore, the mass percentage of the binder or conductive agent may be 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, etc.

[0041] In some embodiments of this disclosure, when the content of the second positive electrode active material in the lithium replenishment layer 20 is 0, the lithium replenishment layer 20 is said not to contain the positive electrode active material 302. This avoids the problems of increased viscosity and coating difficulties in the positive electrode slurry that occur when the first positive electrode lithium replenishment agent 201 and the positive electrode active material 302 are directly mixed. It also significantly reduces the adverse effect on the compressive density of the positive electrode 100 due to poor particle size compatibility. Furthermore, it avoids the problems of increased liquid phase diffusion resistance and decreased liquid phase transport rate of lithium ions in the positive electrode that occur when the first positive electrode lithium replenishment agent 201 is dispersed in the positive electrode slurry, thereby contributing to a reduction in battery impedance.

[0042] In some embodiments of this disclosure, the single-sided density of the positive electrode material layer 30 is greater than the single-sided density of the lithium replenishment layer 20. The positive electrode material layer 30 is the main capacity supply layer of the battery, and setting the single-sided density of the positive electrode material layer 30 higher than that of the lithium replenishment layer 20 contributes to ensuring a high energy density and discharge capacity of the battery. The lithium replenishment layer 20 is used as an example. In this specification, "single-sided density" refers to the surface density of the lithium replenishment layer 20 formed on one side of the positive electrode current collector 10, and does not refer to the sum of the surface densities of the two lithium replenishment layers 20 formed on both sides of the positive electrode current collector 10.

[0043] In one embodiment of this disclosure, the single-sided surface density of the lithium replenishment layer 20 is 0.5 to 50 g / m². 2 This allows the lithium replenishment capacity of the first positive electrode lithium replenisher 201 to be controlled within an appropriate range, enabling the overall performance of the lithium battery to be maintained at a relatively good level. This avoids a deficiency in lithium replenishment effect due to insufficient lithium replenishment capacity of the first positive electrode lithium replenisher 201, and prevents excessive addition of the first positive electrode lithium replenisher 201, ensuring that the amount of lithium replenishment does not exceed the reasonable range for current battery design. In some embodiments, the single-sided density of the lithium replenishment layer 20 is 0.5 to 20 g / m². 2 For example, 0.8 g / m 2 1.0 g / m2 1.2g / m 2 1.5g / m 2 , 2g / m 2 2.5g / m 2 3.0g / m 2 4.0g / m 2 5.0g / m 2 6.0g / m 2 7.0g / m 2 8.0g / m 2 9.0g / m 2 10.0 g / m 2 15.0 g / m 2 , or 20.0 g / m 2 This contributes to both a high positive electrode specific capacity (per gram) and a high initial Coulomb efficiency of the battery, as well as a high utilization rate of lithium replenishment.

[0044] In the embodiments of this disclosure, the single-sided surface density of the positive electrode material layer 30 is 50 to 1000 g / m². 2 For example, 60g / m 2 80g / m 2 100g / m 2 150g / m 2 200g / m 2 210g / m² 2 220g / m 2 250g / m 2 300g / m 2 350g / m 2 400g / m 2 450g / m 2 And so on. In some embodiments, the single-sided density of the positive electrode material layer 30 is 100 to 500 g / m². 2 That is the case.

[0045] In the embodiments of this disclosure, the thickness of one side of the lithium replenishment layer 20 is less than the thickness of one side of the positive electrode material layer 30. This also contributes to ensuring a high energy density of the battery.

[0046] In embodiments of this disclosure, the single-sided thickness of the lithium replenishment layer 20 may be in the range of 0.1 to 100 μm, and further in the range of 0.1 to 50 μm, 0.5 to 20 μm, etc. In some embodiments, the single-sided thickness of the lithium replenishment layer 20 is in the range of 0.5 to 10 μm, for example, 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, or 9 μm. In this case, the lithium replenishment layer 20 containing the first positive electrode lithium replenishment agent 201 can prevent a decrease in the overall capacity of the positive electrode 100 and the energy density of the battery cell due to an excessive thickness of the lithium replenishment layer 20 when the amount of gas generated by the positive electrode 100 is relatively small and the battery impedance is relatively low during the initial charging of the battery. In embodiments of this disclosure, the single-sided thickness of the positive electrode material layer 30 may be in the range of 25 to 500 μm, for example, 30 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 200 μm, 220 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, etc. In some embodiments, the single-sided thickness of the positive electrode material layer 30 is in the range of 50 to 250 μm.

[0047] In one embodiment of this disclosure, in the positive electrode material layer 30, the total mass of the second positive electrode lithium replenisher 301 is 0.5% to 5% of the total mass of the positive electrode active material 302, specifically, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. This allows the second positive electrode lithium replenisher 301 to replenish the irreversible consumption of active lithium in the battery, prevent an excessive decrease in the reversible capacity of the battery's positive electrode 100, and protect the positive electrode 100 from the generation of excess gas. This parameter range is applicable whether one or more positive electrode material layers 30 are a single layer (shown in Figure 1) or multiple layers (two or more layers, shown in Figure 2). In some embodiments, the total mass of the second positive electrode lithium replenisher 301 is 1% to 5% of the total mass of the positive electrode active material 302.

[0048] In embodiments of this disclosure, the ratio of the lithium replenishment capacity provided by the first positive electrode lithium replenisher 201 to the lithium replenishment capacity provided by the second positive electrode lithium replenisher 301 in the positive electrode 100 is (0.2~2):1. This contributes to improving the overall performance of the lithium battery and is particularly advantageous in reducing the battery's DCIR value and improving the utilization rate of the lithium replenisher. Here, the DCIR value represents the direct current internal resistance of the battery and is one of the important parameters for evaluating the performance of a lithium-ion battery. Since the measurement of the DCIR value takes into account all elements of the battery's internal resistance, it is also called dynamic resistance. The magnitude of the DCIR value has a significant impact on the battery's performance and lifespan. A smaller DCIR value indicates better battery charge / discharge performance and a longer lifespan. A larger DCIR value indicates poorer battery output characteristics. The lithium replenishment capacity provided by each lithium replenisher is equal to the product of the mass of the lithium replenisher and the specific capacity (per gram) of the lithium replenisher. In this specification, the specific capacity (per gram) is calculated by a method known in the art, based on the amount of active lithium ions actually released when lithium is replenished in each lithium replenisher. For example, the specific capacity (per gram) of Li5FeO4 corresponds to the theoretical specific capacity (per gram) that releases 4 lithium ions. The specific capacity (per gram) of Li6CoO4 corresponds to the theoretical specific capacity (per gram) that releases 5 lithium ions. The specific capacity (per gram) of Li2CuO2 corresponds to the theoretical specific capacity (per gram) that releases 1 lithium ion. The specific capacities (per gram) of Li2CO3 and Li2C2O4 correspond to the theoretical specific capacities (per gram) that release 2 lithium ions, respectively. The specific capacity (per gram) of Li3N corresponds to the theoretical specific capacity (per gram) that releases 3 lithium ions.

[0049] In this disclosure, when the positive electrode material layer 30 is a single layer (as shown in Figure 1), the second positive electrode lithium replenisher 301 is uniformly dispersed in the positive electrode active material 302. In some embodiments of this disclosure, the positive electrode material layer 30 is a multi-layer structure and includes n (n≧2) positive electrode material sublayers (as shown in Figure 2). In the direction from the positive electrode current collector 10 toward the lithium replenishment layer 20 (i.e., the direction from the positive electrode current collector 10 toward the positive electrode material layer 30, indicated by the arrow in Figure 2), the mass ratio of the second positive electrode lithium replenisher 301 to the positive electrode active material 302 in each positive electrode subcoating layer tends to increase.

[0050] The increasing trend of the aforementioned parameters is described below. In the direction from the positive electrode current collector 10 toward the lithium replenishment layer 20, the sub-coating layers of the positive electrode material layer 30 are sequentially represented as 31, 32, ..., 3n. As a result, the lithium replenishment layer 20, the first positive electrode material sub-layer 31, the second positive electrode material sub-layer 32, ..., and the nth positive electrode material sub-layer 3n are sequentially formed on the surface of the positive electrode current collector 10. Let X1 be the mass ratio of the second positive electrode lithium replenishment 301 to the positive electrode active material 302 in the first positive electrode material sub-layer 31, let X2 be the mass ratio of the second positive electrode lithium replenishment 301 to the positive electrode active material 302 in the second positive electrode material sub-layer 32, ..., and let X be the mass ratio of the second positive electrode lithium replenishment 301 to the positive electrode active material 302 in the nth positive electrode material sub-layer 3n. n Let's assume that in this case, "having an increasing trend" means X1 ≤ X2 ≤ X3 ... ≤ X n , and X n >X1, where X1 is greater than 0. For example, the aforementioned "increasing trend" specifically refers to cases where an increase occurs, then remains unchanged, and then increases further, or where there is a period of no change followed by a sequential increase, or where there is a period of no change followed by an increase, then remains unchanged again, and then increases further in a discontinuous manner, or where each layer increases sequentially (for example, X1 <X2<X3…<X n In that case, it can be.

[0051] The second positive electrode lithium replenisher 301 decomposes at a voltage higher than its own delithiation potential, generating active lithium ions to replenish the battery while simultaneously releasing gas. Therefore, after decomposition, pores may be formed at the original positions of the second positive electrode lithium replenisher 301, thereby increasing the porosity of each positive electrode material sublayer. In this disclosure, in each positive electrode material sublayer, the mass ratio of the second positive electrode lithium replenisher 301 to the positive electrode active material 302 is controlled to increase in the direction away from the positive electrode current collector 10. This makes it possible to smoothly discharge the gas generated by the decomposition of the second positive electrode lithium replenisher 301 in each positive electrode material sublayer close to the positive electrode current collector 10, thereby reducing the degree of battery polarization caused by residual gas. In addition, the pores formed within each positive electrode material sublayer after the decomposition of the lithium replenisher form a gradient porous structure. That is, the number of pores and porosity are relatively small in the positive electrode material sublayers close to the positive electrode current collector 10, while the porosity is higher in the positive electrode material sublayers further away from the positive electrode current collector 10. Such a gradient porous structure improves the overall porosity of the positive electrode 100 and reduces the curvature of the pores, thereby reducing the overall impedance of the battery and improving the output characteristics of the battery.

[0052] In some embodiments of this disclosure, in the direction from the positive electrode current collector 10 toward the lithium replenishment layer 20 (i.e., the direction from the positive electrode current collector 10 toward the positive electrode material layer 30, as indicated by the arrow in Figure 2), the mass ratio of the second positive electrode lithium replenishment 301 to the positive electrode active material 302 in each positive electrode subcoating layer increases sequentially with each layer. This further facilitates the smooth discharge of gas generated during the decomposition of the second positive electrode lithium replenishment 301 in the positive electrode material layer 30, and enables the positive electrode material layer 30 after decomposition to have a pore structure in which the porosity sequentially increases along the direction of the arrow, thereby further contributing to the reduction of battery impedance.

[0053] In some embodiments of this disclosure, of the n positive electrode material sublayers, at least two adjacent layers satisfy the following condition: A m / (D m / D m―1 )-A m-1 ≥5% Here, A m-1 A is the mass ratio of the second positive electrode lithium replenisher 301 in the (m-1)th positive electrode material sublayer to the total amount of the second positive electrode lithium replenisher 301 in the positive electrode material layer 30, Am is the mass ratio of the second positive electrode lithium replenisher 301 in the mth positive electrode material sublayer to the total amount of the second positive electrode lithium replenisher 301 in the positive electrode material layer 30, and D m-1 D is the thickness of the (m-1)th positive electrode material sublayer. m is the thickness of the m-th positive electrode material sublayer, where m is any integer between 2 and n. On the same side of the positive electrode current collector 10, the (m-1)-th positive electrode material sublayer is closer to the positive electrode current collector 10 than the m-th positive electrode material sublayer. That is, if the thicknesses of the positive electrode material sublayers are approximately the same, then from the first positive electrode material sublayer to the nth positive electrode material sublayer, at least two adjacent layers satisfy the following condition: A m -A m-1 ≥5% Here, m is an integer within the range of 2 to n. In this way, after the second positive electrode lithium replenisher 301 decomposes, the porosity of at least two adjacent positive electrode material sublayers can be clearly distinguished, and the aforementioned gradient porous structure has a relatively good effect on reducing battery impedance and improving output performance. In some embodiments of the present disclosure, in n positive electrode material sublayers, any two adjacent positive electrode material sublayers satisfy the following conditions. A m / (D m / D m-1 )-A m-1 ≥5% In some embodiments, A m / (D m / D m-1 )-A m-1 ≥10% These are, for example, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, etc.

[0054] For example, in some embodiments, the thickness of each positive electrode material sublayer is approximately the same (i.e., D m / D m-1 =1) The difference in mass percentage of the second cathode lithium replenisher 301 in any two adjacent cathode material sublayers in the total mass of the second cathode lithium replenisher 301 in the cathode material layer 30 is greater than 5%. In other words, D m / D m-1 If = 1, any two adjacent positive electrode material sublayers among the n positive electrode material sublayers are A m -A m-1 The condition ≥ 5% is satisfied, where m is any integer in the range of 2 to n. Let A1 be the mass ratio of the second positive electrode lithium replenisher 301 in the first positive electrode material sublayer 31 to the total amount of the second positive electrode lithium replenisher 301 in the positive electrode material layer 30, and A2 be the mass ratio of the second positive electrode lithium replenisher 301 in the second positive electrode material sublayer 31 to the total amount of the second positive electrode lithium replenisher 301 in the positive electrode material layer 30, ... and let A2 be the mass ratio of the second positive electrode lithium replenisher 301 in the nth positive electrode material sublayer 3n to the total amount of the second positive electrode lithium replenisher 301 in the positive electrode material layer 30. n In that case, D m / D m-1 If = 1, then |A2-A1|, |A3-A2|, ..., |A n -A n-1 All | values ​​are 5% or greater, preferably 10% or greater. A1 is greater than 0. In some embodiments, when n=2, A1=20%, A2=80%, or A1=30%, A2=70%, or A1=40%, A2=60%, or A1=45%, A2=55%. When n=3, A1=23%, A2=33%, A3=44%, or A1=20%, A2=30%, A3=50%, or A1=10%, A2=30%, A3=60%.

[0055] In embodiments of this disclosure, the mass percentage of the positive electrode active material 302 in each positive electrode material sublayer exceeds 80%, preferably exceeds 90%. This contributes to ensuring that each positive electrode material sublayer provides a relatively high reversible capacity, and as a result, the entire positive electrode 100 has a relatively high reversible capacity. The first positive electrode material sublayer 31 is used as an example. Specifically, the ratio of the mass of the positive electrode active material 302 in the first positive electrode material sublayer 31 to the total mass of the first positive electrode material sublayer 31 exceeds 80%, and moreover exceeds 90%.

[0056] In this disclosure, the single-sided surface density of the positive electrode material sublayers may be the same or different. In some embodiments of this disclosure, the surface density of each positive electrode material sublayer can be the same. This contributes to ensuring a more stable stacked structure. The single-sided surface density referred to herein and the single-sided surface density of the positive electrode material layer 30 and lithium replenishment layer 20 described above in this disclosure all refer to the single-sided surface density of each positive electrode material sublayer before the first cycle (i.e., formation) of the battery.

[0057] In this disclosure, the positive electrode current collector 10 may include, but is not limited to, aluminum foil, aluminum alloy foil, a polymer film material coated with metallic aluminum, or the aforementioned material with a carbon coating. In some embodiments of this disclosure, the positive electrode current collector 10 is aluminum foil. In this disclosure, a laminated structure having a lithium replenishment layer 20 and a positive electrode material layer 30 (shown in Figures 1 and 2) may be formed on one side of the positive electrode current collector 10. Alternatively, a laminated structure having a lithium replenishment layer 20 and the positive electrode material layer 30 may be formed on each of the opposing sides of the positive electrode current collector 10.

[0058] In this disclosure, the lithium replenishment layer 20 may further contain a conductive agent, and the cathode material layer 30 may also contain a conductive agent. Each conductive agent can be independently selected from one or more of the following: conductive carbon black (e.g., acetylene black, Ketjen black, Super P, 350G carbon black, etc.), carbon nanotubes, graphene, carbon fibers, etc. Specifically, carbon nanotubes may be single-walled carbon nanotubes or multi-walled carbon nanotubes, and carbon fibers may be arranged carbon fibers. In some embodiments, the lithium replenishment layer 20 and the cathode material layer 30 may further contain one or more of the following: binders and dispersants. Each binder can be independently selected from one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyolefins (e.g., polyethylene (PE), polypropylene (PP)), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyimide (PI), styrene-butadiene rubber (SBR), sodium carboxymethylcellulose (CMC), sodium alginate (SA), gelatin, etc., but is not limited to these. Each dispersant can be selected from one or more of the following: polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), etc.

[0059] The lithium replenishment layer 20 can be formed by applying and drying a primer coating slurry containing a first positive electrode lithium replenishment agent 201, a conductive agent, and a solvent. The coating method may include, but is not limited to, one or more combinations of methods such as spin coating, brush coating, spray coating, dip coating, and blade coating. Similarly, the positive electrode material layer 30 can be formed by applying and drying a positive electrode slurry containing a positive electrode active material 302, a second positive electrode lithium replenishment agent 301, a conductive agent, and a solvent. If the positive electrode material layer 30 is a single layer, there is one type of positive electrode slurry; if the positive electrode material layer 30 has multiple layers, the number of types of positive electrode slurry used corresponds to the number of layers in the positive electrode material layer 30.

[0060] The solvents contained in the various slurries may be the same or different, and can be independently selected from one or more of the following: pyrrolidones (e.g., N-methylpyrrolidone (NMP), N-ethylpyrrolidone, etc.), cyclic ethers (e.g., tetrahydrofuran, methyltetrahydrofuran), dimethyl sulfoxides, ketones (e.g., acetone, or butanone), and lactones (e.g., butyrolactone, caprolactone), but are not limited to these. The solid content concentration of the various slurries is not particularly limited and can satisfy the fluidity and uniformity during coating. Generally, the solid content concentration of the primer coating slurry is in the range of 1% to 50%. The solid content concentration of the positive electrode slurry is in the range of 50% to 70%.

[0061] In addition, the various slurries may be laminated simultaneously or sequentially, or coated on top of a coating formed by the drying of the previous slurry. For example, if the positive electrode material layer 30 is a single layer, the positive electrode slurry is coated directly onto the primer coating slurry (coated simultaneously or sequentially), then dried together to remove the solvent, and then rolled. If double-sided coating is required, the above steps can be repeated on the other side of the positive electrode current collector 10. Alternatively, a lithium replenishment layer 20 may be formed by applying a primer coating slurry to one side of the positive electrode current collector 10 and drying it, then the positive electrode slurry may be applied onto the lithium replenishment layer 20 and dried to form the positive electrode material layer 30, and then rolled.

[0062] Refer to Figure 3. One embodiment of the present disclosure further provides a lithium battery 1. The lithium battery 1 includes a positive electrode 100 according to an embodiment of the present disclosure. By using the positive electrode 100, the utilization rate of the two types of lithium replenishers in the lithium battery 1 is increased, and the battery has a high reversible capacity and improved energy density. The battery also has a relatively low impedance and relatively good output characteristics.

[0063] In embodiments of this disclosure, the lithium battery 1 comprises a negative electrode 11, a separator 111 and an electrolyte 112 disposed between the positive electrode 100 and the negative electrode 11.

[0064] The negative electrode 11 typically includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector. The negative electrode material layer generally includes a negative electrode active material, a conductive agent, and a binder. In one embodiment of this disclosure, the negative electrode active material can be selected from one or more carbon-based materials, silicon-based materials, tin-based materials, etc. Carbon-based materials include one or more soft carbon, hard carbon, graphite, mesophase carbon microbeads, etc. Silicon-based materials can include one or more elemental silicon, silicon alloys, silicon oxides, silicon-carbon composite materials, etc. Tin-based materials can include one or more elemental tin, tin oxide, tin alloys, tin-carbon compounds, etc.

[0065] The separator 111 is configured to separate the positive electrode 100 from the negative electrode 11, thereby maintaining insulation and fluid retention between the positive electrode 100 and the negative electrode 11. The separator 111, the positive electrode 100, and the negative electrode 11 together constitute a battery cell of the battery. The battery cell is housed in a battery housing and is moistened by an electrolyte 112 housed within the housing. In some embodiments of this disclosure, the lithium battery 1 can be assembled by the following method: stacking the positive electrode 100, the separator 111, and the negative electrode 11 sequentially to form a battery cell, housing the battery cell in a battery housing, injecting the electrolyte, and sealing the battery case to form the battery. The battery cell may be wound or stacked.

[0066] Any separator material can be used in a battery. For example, the separator includes, but is not limited to, polymer separators such as single-layer PP (polypropylene) film, single-layer PE (polyethylene) film, PP / PE double-layer film, PP / PP double-layer film, PP / PE / PP triple-layer film, and nonwoven fabric. The electrolyte includes an electrolyte salt and an organic solvent, and the specific types and compositions of the electrolyte salt and organic solvent are well-known choices in the battery field and can be selected according to actual requirements.

[0067] Refer to Figure 4. According to embodiments of the present disclosure, a further apparatus 2 is provided. Apparatus 2 includes a lithium battery 1 according to embodiments of the present disclosure. Apparatus 2 may be an electrical device such as a vehicle (e.g., automobile, motorcycle, or bicycle), an electric toy, or a 3C product (e.g., a mobile phone, laptop computer, tablet computer, pen-input computer, e-book reader, wearable device, etc.), an energy storage system, etc. The electrical device powered by the aforementioned lithium battery 1 has a long operating time and a fast charging speed. [Examples]

[0068] The technical solutions of this disclosure will be further described with reference to several specific examples below.

[0069] (Example 1) The method for manufacturing the positive electrode includes the following steps.

[0070] A first positive electrode lithium replenisher (specifically, Li5FeO4 having a carbon coating layer, with a mass percentage of the coating material being 3 wt%) is mixed with a binder (PVDF), a conductive agent (carbon black), a dispersant (PVP), and a solvent (NMP) in a mass ratio of 10:1:1:0.1:90 and uniformly stirred to obtain a primer coating slurry. The primer coating slurry is spray-coated onto the surface of an aluminum foil, which is the positive electrode current collector, and then dried to form an aluminum foil having a lithium replenishment layer. Here, the surface density of the lithium replenishment layer on one side is 2.41 g / m². 2The coating thickness is 3±1μm.

[0071] A cathode slurry is prepared by uniformly mixing lithium iron phosphate (LFP, Dv50 3 μm), the cathode active material, with PVDF as a binder, carbon nanotubes as conductive agents, graphene as a conductive agent, a second cathode lithium replenisher (specifically Li2CO3 with a Dv50 of 200 nm), and NMP as a solvent in a mass ratio of 100:2.5:1:0.5:1:60. The cathode slurry is then applied to a lithium replenishment layer and dried to achieve a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed.

[0072] The above-described process of forming the lithium replenishment layer and the positive electrode material layer is repeated on the opposite side of the aluminum foil, and then a rolling process is performed to obtain a positive electrode for use. In the positive electrode, the ratio of the lithium replenishment capacity of the first lithium replenishment for the positive electrode to the lithium replenishment capacity of the second lithium replenishment for the positive electrode is approximately 1:1.

[0073] The manufacturing method for lithium batteries includes the following steps:

[0074] (1) Fabrication of the negative electrode: A negative electrode slurry is prepared by uniformly mixing graphite (the negative electrode active material), SBR (the binder), CMC (the thickener), carbon black (the conductive agent), and H2O (the solvent) in a mass ratio of 100:2:2:1:120. The negative electrode slurry is applied to copper foil, which is the negative electrode current collector, and dried to achieve a single-sided surface density of 100 g / m². 2 This forms the negative electrode material layer.

[0075] (2) Battery assembly: The aforementioned positive electrode, separator (specifically, a 14 μm thick PP separator), and negative electrode are sequentially stacked to obtain a battery cell. Next, the stacked battery cell is wound and housed in a battery housing. After assembly and drying, the prepared electrolyte is injected, the battery housing is sealed, and an airbag is secured to manufacture a lithium battery for subsequent electrical performance testing.

[0076] (Example 2) A method for fabricating a positive electrode is provided. This embodiment differs from Example 1 in that it has two positive electrode material layers, and the first positive electrode slurry and the second positive electrode slurry are laminated onto one side of the lithium replenishment layer. After drying, the first positive electrode slurry forms the first positive electrode material sublayer, and the second positive electrode slurry forms the second positive electrode material sublayer. The first positive electrode material sublayer is positioned close to the lithium replenishment layer. The second positive electrode material sublayer is positioned on the side of the first positive electrode material sublayer that is spaced away from the lithium replenishment layer. The composition of the first positive electrode slurry in contact with the lithium replenishment layer is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li2CO3:NMP=100:2.6:1:0.5:0.5:60. The composition of the second cathode slurry separated from the lithium replenishment layer is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li2CO3:NMP = 100:2.4:1:0.5:1.5:60. The ratio of the surface density of the first cathode material sublayer to the surface density of the second cathode material sublayer is 1:1. The single-sided surface density of the entire cathode material layer remains 200 g / m². 2 Therefore, at the positive electrode, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenisher to the lithium replenishment capacity of the second positive electrode lithium replenisher remains 1:1.

[0077] A lithium battery is assembled using the positive electrode of Example 2, according to the method described in Example 1.

[0078] (Example 3) The method for manufacturing the positive electrode includes the following steps.

[0079] A first positive electrode lithium replenisher (specifically, Li6CoO4 with a carbon coating layer, where the mass percentage of the coating material is 2.5 wt%) is mixed with a binder (PVDF), conductive materials carbon black, PVP, and NMP in a mass ratio of 10:1:1:0.2:90 and uniformly stirred to obtain a primer coating slurry. The primer coating slurry is spray-coated onto the surface of aluminum foil and then dried to form an aluminum foil current collector having a lithium replenishment layer. Here, the surface density of the lithium replenishment layer on one side is 2.46 g / m². 2 The thickness is 3±1μm.

[0080] A cathode slurry is prepared by uniformly mixing the cathode active material (lithium iron phosphate (LFP, Dv50 is 3 μm)) with a binder (PVDF), carbon nanotubes, graphene, a second cathode lithium replenisher (specifically, Li2C2O4 with a Dv50 of 150 nm), and the solvent NMP in a mass ratio of 100:2.5:1:0.5:1.4:60. The cathode slurry is then applied to a lithium replenishment layer and dried to achieve a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed. In the positive electrode material layer, the total mass of the second positive electrode lithium replenisher is 1.4% of the total mass of the positive electrode active material.

[0081] The above-described process for forming the lithium replenishment layer and the positive electrode material layer is repeated on the opposite side of the aluminum foil, and then a rolling process is performed to obtain the positive electrode to be used. In the positive electrode, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenishment to the lithium replenishment capacity of the second positive electrode lithium replenishment is 1.2:1.

[0082] A lithium battery is assembled using the positive electrode of Example 3, according to the method described in Example 1.

[0083] (Example 4) A method for manufacturing a cathode is provided, which differs from Example 3 in that it comprises two cathode material layers and employs a two-layer coating. A first cathode slurry and a second cathode slurry are sequentially coated onto one side of the lithium replenishment layer. After drying, the first cathode slurry forms the first cathode material sublayer, and the second cathode slurry forms the second cathode material sublayer. The first cathode material sublayer is close to the lithium replenishment layer, and the second cathode material sublayer is located on the side of the first cathode material sublayer that is spaced away from the lithium replenishment layer. The composition of the first cathode slurry in contact with the lithium replenishment layer is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li2C2O4:NMP=100:2.6:1:0.5:0.7:60. The composition of the second cathode slurry separated from the lithium replenishment layer is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li2C2O4:NMP = 100:2.4:1:0.5:2.1:60. The ratio of the surface density of the first cathode material sublayer to the surface density of the second cathode material sublayer is controlled to be 1:1. The single-sided surface density of the entire cathode material layer remains 200 g / m². 2 Therefore, at the positive electrode, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenisher to the lithium replenishment capacity of the second positive electrode lithium replenisher remains 1.2:1.

[0084] A lithium battery is assembled using the negative electrode of Example 4, following the method described in Example 1.

[0085] (Example 5) The manufacturing method for the positive electrode includes the following steps.

[0086] A lithium replenisher for the first positive electrode (specifically, Li2CuO2 without a coating layer) is mixed with a binder (PVDF), conductive materials carbon black, PVP, and NMP in a mass ratio of 10:1:1:0.2:90 and uniformly stirred to obtain a primer coating slurry. The primer coating slurry is spray-coated onto the surface of aluminum foil and then dried to form an aluminum foil current collector having a lithium replenishment layer. Here, the surface density of the lithium replenishment layer on one side is 4 g / m². 2 The coating thickness is 5 ± 1 μm.

[0087] A cathode slurry is prepared by uniformly mixing lithium iron phosphate (LFP, Dv50 3 μm), which is the cathode active material, with a binder consisting of PVDF, carbon nanotubes, graphene, a second cathode lithium replenisher (specifically Li3N, Dv50 400 nm), and a solvent, NMP, in a mass ratio of 100:2.5:1:0.5:1:60. The cathode slurry is then applied to the aforementioned lithium replenishment layer and dried to achieve a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed.

[0088] The above-described process for forming the lithium replenishment layer and the positive electrode material layer is repeated on the opposite side of the aluminum foil, and then it is rolled to obtain the positive electrode to be used. The positive electrode of Example 5 is assembled into a lithium battery according to the method described in Example 1.

[0089] (Example 6) This embodiment provides a method for manufacturing a cathode that differs from Example 5 in that it has two cathode material layers and employs a two-layer coating process. The first cathode slurry and the second cathode slurry are sequentially coated onto one side of the lithium replenishment layer. After drying, the first cathode slurry forms the first cathode material sublayer, and the second cathode slurry forms the second cathode material sublayer. The first cathode material sublayer is close to the lithium replenishment layer, and the second cathode material sublayer is located on the side of the first cathode material sublayer that is spaced away from the lithium replenishment layer. The composition of the first cathode slurry in contact with the lithium replenishment layer is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li3N:NMP=100:2.6:1:0.5:0.4:60. The composition of the second cathode slurry separated from the lithium replenishment layer is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li3N:NMP = 100:2.4:1:0.5:1.6:60. The ratio of the surface density of the first cathode material sublayer to the surface density of the second cathode material sublayer is 1:1. The single-sided surface density of the entire cathode material layer remains 200 g / m². 2 That is the case.

[0090] A lithium battery is assembled using the positive electrode of Example 6 according to the method described in Example 1.

[0091] (Example 7) Example 7 differs from Example 1 in that the first positive electrode lithium replenishing agent is Li5FeO4 having no conductive coating layer on the surface.

[0092] (Example 8) The positive electrode of Example 8 is mainly different from Example 1 in that the lithium replenishing layer further contains the positive electrode active material LFP.

[0093] The lithium replenishing layer is formed by applying a primer coating slurry obtained by mixing the aforementioned first positive electrode lithium replenishing agent, lithium iron phosphate (LFP, Dv50 is 3 μm), PVDF as a binder, carbon black as a conductive agent, PVP as a dispersant, and NMP as a solvent at a mass ratio of 6:4:1:1:0.1:90, followed by drying. The areal density per one side of the lithium replenishing layer is 3.97 g / m 2 and the thickness is 4±1 μm.

[0094] A positive electrode slurry having the same composition as that of Example 1 is applied onto the lithium replenishing layer and dried, so that an areal density per one side of 198 g / m 2 positive electrode material layer is formed.

[0095] The aforementioned steps of forming the lithium replenishing layer and the positive electrode material layer are repeated on the opposite side of the aluminum foil, and then a rolling treatment is performed to obtain a positive electrode. In the positive electrode of Example 8, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to the lithium replenishing capacity of the second positive electrode lithium replenishing agent is still 1:1.

[0096] (Example 9) In the positive electrode of Example 9, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenisher to the lithium replenishment capacity of the second positive electrode lithium replenisher is 0.1:1, which is the main difference between Example 9 and Example 1. The composition of the primer coating slurry for forming the lithium replenishment layer in Example 9 is the same as in Example 1, but the single-sided surface density of the lithium replenishment layer is 0.48 g / m². 2 The coating thickness is 2 ± 1 μm.

[0097] A cathode slurry is prepared by uniformly mixing lithium iron phosphate (LFP, Dv50 of 3 μm), which is the cathode active material, with PVDF as a binder, carbon nanotubes as a conductive agent, graphene as a conductive agent, a second cathode lithium replenisher (Li2CO3 with a Dv50 of 200 nm), and NMP as a solvent in a mass ratio of 100:2.5:1:0.5:2:60. The positive electrode slurry is applied onto the aforementioned lithium replenishment layer and dried, resulting in a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed. In the positive electrode material layer, the total mass of the second positive electrode lithium replenisher is 2% of the total mass of the positive electrode active material.

[0098] The above-described process for forming the lithium replenishment layer and the positive electrode material layer is repeated on the opposite side of the aluminum foil, and then a rolling process is performed to obtain the positive electrode to be used. In the positive electrode manufactured in Example 9, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenishment to the lithium replenishment capacity of the second positive electrode lithium replenishment is 0.1:1.

[0099] (Example 10) Example 10 differs from Example 1 mainly in that the ratio of the lithium replenishment capacity of the first positive electrode lithium replenisher to the lithium replenishment capacity of the second positive electrode lithium replenisher is 9:1. The composition of the primer coating slurry for forming the lithium replenishment layer in Example 10 is the same as in Example 1, but the single-sided density of the lithium replenishment layer is 4.38 g / m². 2 The coating thickness is 5 ± 1 μm.

[0100] A positive electrode slurry is prepared by uniformly mixing lithium iron phosphate (LFP, Dv50 of 3 μm), which is the positive electrode active material, with PVDF as a binder, carbon nanotubes as a conductive agent, graphene as a conductive agent, a second positive electrode lithium replenisher (Li2CO3 with a Dv50 of 200 nm), and NMP as a solvent in a mass ratio of 100:2.5:1:0.5:0.2:60. The positive electrode slurry is then applied to the lithium replenishment layer and dried to obtain a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed. In the positive electrode material layer, the total mass of the second positive electrode lithium replenisher is 0.2% of the total mass of the positive electrode active material.

[0101] The above-described process for forming the lithium replenishment layer and the positive electrode material layer is repeated on the opposite side of the aluminum foil, and then a rolling process is performed to obtain the positive electrode to be used. In the positive electrode manufactured in Example 10, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenishment to the lithium replenishment capacity of the second positive electrode lithium replenishment is 9:1, and the total mass of the second positive electrode lithium replenishment is 0.2% of the total mass of the positive electrode active material.

[0102] (Example 11) Example 11 differs from Example 1 mainly in that the Dv50 of the second cathode lithium replenisher is 600 nm.

[0103] (Example 12) Example 12 differs from Example 1 mainly in that the Dv50 of the second positive electrode lithium replenisher is 20 nm, and the Dv50 of the positive electrode active material, lithium iron phosphate (LFP), is 0.2 μm.

[0104] (Example 13) Example 13 differs from Example 1 mainly in that the Dv50 of the second positive electrode lithium replenisher is 500 nm, and the Dv50 of the positive electrode active material, lithium iron phosphate (LFP), is 5 μm.

[0105] (Example 14) The positive electrode of Example 14 is mainly different from Example 1 in that the total mass of the second positive electrode lithium replenishing agent is 0.5% of the total mass of the positive electrode active material, and the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to the lithium replenishing capacity of the second positive electrode lithium replenishing agent is about 3:1. The areal density of one side of the lithium replenishing layer is 3.65g / m 2 and the thickness of one side is 4±1μm.

[0106] Lithium iron phosphate (LFP, Dv50 is 3μm) as the positive electrode active material is uniformly mixed with PVDF as the binder, carbon nanotubes as the conductive agent, graphene as the conductive agent, the second positive electrode lithium replenishing agent (specifically Li₂CO₃ with Dv50 of 200nm), and NMP as the solvent at a mass ratio of 100:2.5:1:0.5:0.5:60 to prepare a positive electrode slurry. The positive electrode slurry is applied onto the lithium replenishing layer and dried, so that a single-side areal density of 200g / m 2 of the positive electrode material layer is formed. In the positive electrode material layer, the total mass of the second positive electrode lithium replenishing agent is 0.5% of the total mass of the positive electrode active material.

[0107] The aforementioned steps of forming the lithium replenishing layer and the positive electrode material layer are repeated on the opposite side of the aluminum foil, followed by a rolling treatment to obtain the positive electrode to be used. A lithium battery is assembled using the positive electrode of Example 14 according to the method described in Example 1.

[0108] (Example 15) Example 15 is mainly different from Example 1, and in the positive electrode of Example 15, Example 15 is mainly different from Example 1 in that the total mass of the second positive electrode lithium replenishing agent is 5% of the total mass of the positive electrode active material, and the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to the lithium replenishing capacity of the second positive electrode lithium replenishing agent is about 0.15:1. The areal density of one side of the lithium replenishing layer is 1.74g / m 2 and the thickness of one side is 2±1μm.

[0109] A cathode slurry is prepared by uniformly mixing lithium iron phosphate (LFP, Dv50 of 3 μm), the cathode active material, with PVDF as a binder, carbon nanotubes as conductive agents, graphene as a conductive agent, a second cathode lithium replenisher (specifically Li2CO3 with a Dv50 of 200 nm), and the solvent NMP in a mass ratio of 100:2.5:1:0.5:5:60. The cathode slurry is then applied to a lithium replenishment layer and dried to achieve a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed. In the positive electrode material layer, the total mass of the second positive electrode lithium replenisher is 5% of the total mass of the positive electrode active material.

[0110] The above-described process for forming the lithium replenishment layer and the positive electrode material layer is repeated on the opposite side of the aluminum foil, and then a rolling process is performed to obtain the positive electrode to be used. A lithium battery is assembled using the positive electrode of Example 15 according to the method described in Example 1.

[0111] (Example 16) The positive electrode of Example 16 further contains a lithium replenishment layer containing positive electrode active material (specifically, LFP with a Dv50 of 3 μm), and the single-sided surface density of the lithium replenishment layer is 20 g / m². 2 This differs from Example 1 mainly in that the thickness on one side is 12 ± 1 μm. The lithium replenishment layer is obtained by applying a primer coating slurry, which is obtained by mixing the aforementioned first positive electrode lithium replenisher, LFP, PVDF as a binder, carbon black as a conductive agent, PVP as a dispersant, and NMP as a solvent in a mass ratio of 2:8:0.2:0.2:0.1:90, and then drying it. In addition, the surface density on one side of the positive electrode material layer is 180 g / m². 2 That is the case.

[0112] Therefore, in the positive electrode of Example 16, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenisher to the lithium replenishment capacity of the second positive electrode lithium replenisher is approximately 2.12:1.

[0113] (Example 17) The positive electrode in Example 17 has a lithium replenishment layer with a single-sided surface density of 50 g / m². 2This differs from Example 1 mainly in that the thickness on one side is 30 ± 1 μm. The lithium replenishment layer is obtained by applying a primer coating slurry, which is obtained by mixing the aforementioned first positive electrode lithium replenisher, LFP, PVDF as a binder, carbon black as a conductive agent, PVP as a dispersant, and NMP as a solvent in a mass ratio of 0.8:9.2:0.2:0.2:0.1:90, and then drying it. In addition, the surface density on one side of the positive electrode material layer is 150 g / m². 2 That is the case.

[0114] In the positive electrode manufactured in Example 17, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenisher to the lithium replenishment capacity of the second positive electrode lithium replenisher is 2.55:1.

[0115] (Example 18) In the positive electrode of Example 18, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenisher to the lithium replenishment capacity of the second positive electrode lithium replenisher is approximately 2:1, and the single-sided surface density of the lithium replenishment layer is 4.81 g / m². 2 Example 18 differs from Example 1 mainly in that its single-sided thickness is 5±1μm.

[0116] (Example 19) The manufacturing method of Example 19 differs from Example 2 mainly in that the composition of the first positive electrode slurry in contact with the lithium replenishment layer is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li2CO3:NMP=100:2.6:1:0.5:0.9:60, and the composition of the second positive electrode slurry separated from the lithium replenishment layer is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li2CO3:NMP=100:2.4:1:0.5:1.1:60.

[0117] In Example 19, the mass ratio of the second cathode lithium replenisher in the first cathode material sublayer formed by drying the first cathode slurry to all of the second cathode lithium replenisher in the cathode is 45%, and the mass ratio of the second cathode lithium replenisher in the second cathode material sublayer formed by drying the second cathode slurry to all of the second cathode lithium replenisher in the cathode is 55%. In addition, the ratio of the surface density of the first cathode material sublayer to the surface density of the second cathode material sublayer is still 1:1, and the single-sided surface density of the entire cathode material layer is still 200 g / m². 2 Therefore, at the positive electrode, the ratio of the lithium replenishment capacity of the first positive electrode lithium replenisher to the lithium replenishment capacity of the second positive electrode lithium replenisher remains 1:1.

[0118] (Example 20) A positive electrode is provided, and it differs from the positive electrode of Example 1 only in that the positive electrode active material is lithium iron manganese phosphate (LMFP) with a Dv50 of 1 μm.

[0119] The manufacturing method for lithium batteries includes the following steps:

[0120] (1) Manufacturing of the negative electrode: The negative electrode slurry is prepared by uniformly mixing graphite (the negative electrode active material), silicon-carbon composite material, SBR (the binder), CMC (the thickener), carbon black (the conductive agent), and H2O (the solvent) in a mass ratio of 90:10:2:2:1:120. The negative electrode slurry is applied to copper foil, which is the negative electrode current collector, and dried to achieve a single-sided surface density of 80 g / m². 2 This forms the negative electrode material layer.

[0121] (2) Battery assembly: The positive electrode, separator (specifically, a 14 μm thick PP separator), and negative electrode are sequentially stacked to obtain a battery element. The stacked battery element is then wound and housed in a battery housing. After assembly and drying, the prepared electrolyte is injected, the battery housing is sealed, and an airbag is secured to manufacture a lithium battery for subsequent electrical performance testing.

[0122] To more clearly demonstrate the beneficial effects of this disclosure, Comparative Examples 1-8 are further provided in this disclosure.

[0123] (Comparative Example 1) A method for manufacturing a positive electrode is provided, which differs from Example 1 in that the positive electrode does not contain a first type of positive electrode lithium replenisher and a second type of positive electrode lithium replenisher.

[0124] The method for manufacturing the positive electrode includes the following steps: Lithium iron phosphate, PVDF as a binder, carbon nanotubes as a conductive agent, graphene as a conductive agent, and NMP as a solvent are uniformly mixed in a mass ratio of 100:2.5:1:0.5:60 to prepare a positive electrode slurry. The positive electrode slurry is applied to an aluminum foil current collector and dried to obtain a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed. The above process of forming the positive electrode material layer is repeated on the opposite side of the aluminum foil, and then a rolling process is performed to obtain the positive electrode.

[0125] A lithium battery is assembled using the positive electrode of Comparative Example 1 according to the method described in Example 1.

[0126] (Comparative Example 2) The positive electrode of Comparative Example 2 differs from that of Example 7 in that the mixed layer containing the first positive electrode lithium replenisher and the positive electrode active material is directly placed on the aluminum foil.

[0127] The method for manufacturing the positive electrode of Comparative Example 2 specifically includes the following steps: Lithium iron phosphate, PVDF as a binder, carbon nanotubes as a conductive agent, graphene as a conductive agent, a first positive electrode lithium replenisher (specifically, Li5FeO4 without a carbon coating layer on its surface, with a mass percentage of 3 wt% of the coating layer material), and NMP as a solvent are uniformly mixed in a mass ratio of 100:2.5:1:0.5:2:60 to prepare a positive electrode slurry. The positive electrode slurry is applied to an aluminum foil current collector and dried to obtain a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed. The above process of forming the positive electrode material layer is repeated on the opposite side, and then a rolling process is performed to obtain the positive electrode.

[0128] A lithium battery is assembled using the positive electrode of Comparative Example 2 according to the method described in Example 1.

[0129] (Comparative Example 3) The main difference from Example 3 is that a positive electrode is provided, and a mixed layer containing a second positive electrode lithium replenisher and a positive electrode active material is placed directly on the aluminum foil.

[0130] The method for manufacturing the positive electrode of Comparative Example 3 specifically includes the following steps: Lithium iron phosphate, PVDF as a binder, carbon nanotubes, graphene, a second positive electrode lithium replenisher Li2C2O4, and NMP as a solvent are uniformly mixed in a mass ratio of 100:2.5:1:0.5:3:60 to prepare a positive electrode slurry. The positive electrode slurry is applied to an aluminum foil current collector and dried to obtain a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed. The above process of forming the positive electrode material layer is repeated on the opposite side of the aluminum foil, and then a rolling process is performed to obtain the positive electrode.

[0131] A lithium battery is assembled using the positive electrode of Comparative Example 3 according to the method described in Example 1.

[0132] (Comparative Example 4) This invention differs from Example 1 in that a positive electrode is provided, a positive electrode material layer without a lithium replenisher is placed on aluminum foil, and a second lithium replenisher layer containing a second positive electrode lithium replenisher is placed on the positive electrode material layer.

[0133] The slurry composition of the positive electrode material layer is the same as in Example 1, except that it does not contain the second positive electrode lithium replenisher. The single-sided density of the positive electrode material layer remains 200 g / m². 2 The slurry for forming the second lithium replenishment layer is obtained by mixing the second cathode lithium replenisher, the binder PVDF, the conductive agent carbon black, the dispersant PVP, and the solvent NMP in a mass ratio of 10:1:1:0.1:90. The single-sided density of the second lithium replenishment layer is 4.6 g / m².2 That is the case.

[0134] A lithium battery is assembled using the positive electrode of Comparative Example 4, according to the method described in Example 1.

[0135] (Comparative Example 5) A positive electrode is provided, and unlike Example 1, the positive electrode material layer containing the second positive electrode lithium replenisher in Example 1 is in direct contact with the aluminum foil, and the lithium replenishment layer in Example 1 is positioned on the side of the positive electrode material layer that is separated from the aluminum foil.

[0136] A lithium battery is assembled using the positive electrode of Comparative Example 5, according to the method described in Example 1.

[0137] (Comparative Example 6) The main difference from Example 4 is that a positive electrode is provided, and a lithium replenishment layer is not provided on the aluminum foil current collector. Instead, the first positive electrode material sublayer and the second positive electrode material sublayer are directly and sequentially laminated. In Comparative Example 6, the composition of the first positive electrode slurry for forming the first positive electrode material sublayer adjacent to the current collector is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li2C2O4:NMP=100:2.6:1:0.5:1.5:60. The composition of the second positive electrode slurry for forming the second positive electrode material sublayer spaced away from the current collector is lithium iron phosphate:PVDF:carbon nanotubes:graphene:Li2C2O4:NMP=100:2.4:1:0.5:4.6:60. The ratio of the surface density of the first positive electrode material sublayer formed by drying the first positive electrode slurry to the surface density of the second positive electrode material sublayer formed by drying the second positive electrode slurry is controlled to be 1:1. The single-sided surface density of the entire positive electrode material layer remains 200 g / m². 2 That is the case.

[0138] A lithium battery is assembled using the positive electrode of Comparative Example 6 according to the method described in Example 1.

[0139] (Comparative Example 7) A method for manufacturing a positive electrode is provided, and the positive electrode differs from Comparative Example 1 in that the positive electrode active material is replaced from lithium iron phosphate to lithium iron manganese phosphate.

[0140] The method for manufacturing the positive electrode includes the following steps: Lithium iron manganese phosphate, PVDF as a binder, carbon nanotubes as a conductive agent, graphene as a conductive agent, and NMP as a solvent are uniformly mixed in a mass ratio of 100:2.5:1:0.5:60 to prepare a positive electrode slurry. The positive electrode slurry is applied to an aluminum foil current collector and dried to obtain a single-sided surface density of 200 g / m². 2 A positive electrode material layer is formed. The above process of forming the positive electrode material layer is repeated on the opposite side of the aluminum foil, and then a rolling process is performed to obtain the positive electrode.

[0141] A lithium battery is assembled using the positive electrode of Comparative Example 7 according to the method described in Example 1.

[0142] (Comparative Example 8) This invention differs from Example 7 in that a positive electrode is provided, a lithium replenishment layer is provided on aluminum foil, and a second positive electrode material layer without lithium replenishment is provided on the lithium replenishment layer.

[0143] The slurry composition for forming the lithium replenishment layer is the same as in Example 7, and the single-sided density of the lithium replenishment layer is 4.82 g / m². 2 The thickness is 5 ± 1 μm. The slurry for forming the positive electrode material layer is obtained by uniformly mixing lithium iron phosphate (LFP, Dv50 is 3 μm), which is the positive electrode active material, PVDF as a binder, carbon nanotubes as a conductive agent, graphene as a conductive agent, and NMP as a solvent in a mass ratio of 100:2.5:1:0.5:60. The single-sided density of the positive electrode material layer is 200 g / m². 2 That is the case.

[0144] To more fully substantiate the beneficial effects brought about by the technical solutions of this disclosure, the following performance tests are performed on the lithium batteries of each of the above-described embodiments and comparative examples.

[0145] a. Positive electrode specific capacity (per gram) test: At room temperature (25°C), each battery is charged at a constant current and voltage rate of 1 / 3C, and charged to an upper voltage limit of 4.6V to perform a formation (where C is the battery capacity). The initial charge capacity (i.e., the charge capacity at the time of formation) is recorded. After aging (the aging process involves storing the batteries at 45°C for 48 hours under 100% SOC conditions, and the same applies hereafter), the batteries are discharged at 1 / 3C to a lower voltage limit of 2.0V, and the initial discharge capacity is calculated. Positive electrode specific capacity (per gram) = Initial discharge capacity / Mass of positive electrode active material Initial Coulomb efficiency η = Initial discharge capacity / Initial charge capacity

[0146] b. Cycle performance test: At room temperature (25°C), the aged battery is charged at a constant current and voltage of 1 / 3C until it reaches an upper voltage of 3.8V, and then discharged at 1 / 3C until it reaches a lower voltage of 2.0V. The above charge-discharge process is repeated 500 times, and the capacity retention rate after 500 cycles is recorded. Capacity retention rate after 500 cycles = Discharge capacity at the 500th cycle / First discharge capacity after aging

[0147] c. Battery DC Internal Resistance (DCIR) Test: At room temperature (25°C), the aged battery is charged to its upper voltage limit of 3.8V with a constant current of 1 / 3C, and then discharged to its lower voltage limit of 2.0V with 1 / 3C. After 3 cycles, the battery is charged to 50% SOC with a constant current of 1 / 3C at 25°C. The battery voltage after standing for 1 hour is recorded as V1. Next, the battery is discharged at 1.5C for 30 seconds, and the battery voltage after discharge is recorded as V2. DCIR = (V1 - V2) / 1.5C.

[0148] d. Lithium replenishment material utilization rate test: Non-lithium-rechargeable batteries corresponding to each lithium-rechargeable battery in the examples and comparative examples of this disclosure are prepared: Examples 1-20 and Comparative Examples 2-6 and 8 are lithium-rechargeable batteries, Comparative Example 1 corresponds to a non-lithium-rechargeable battery corresponding to Examples 1-19 and Comparative Examples 2-6, and Comparative Example 7 corresponds to a non-lithium-rechargeable battery corresponding to Example 20. At room temperature (25°C), the aforementioned batteries are charged to an upper voltage limit of 4.6V with a constant current and voltage of 1 / 3C, and after aging, are discharged to a lower voltage limit of 2.0V with 1 / 3C. The discharge capacity of each lithium-rechargeable battery is denoted as C1, and the discharge capacity of the corresponding non-lithium-rechargeable battery is denoted as C2. The utilization rate of lithium replenishment material = (C1 - C2) / (mass of lithium replenishment material × specific volume of lithium replenishment material (per gram)). Here, the specific capacity (per gram) of the lithium replenishment material is calculated using a method known in the field, based on the amount of active lithium ions actually released during the lithium replenishment process of each lithium replenishment agent.

[0149] The relevant test results are summarized in Table 1 below.

[0150] [Table 1]

[0151] From Examples 1 and 7, and Comparative Examples 1-2, 4 and 5 in Table 1, it can be seen that when the positive electrode does not contain a lithium replenisher (Comparative Example 1), the battery has a low positive electrode specific capacity (per gram) and initial Coulomb efficiency, and a high DCIR value. Furthermore, for Comparative Examples 2 and 4-5, where the positive electrode contains only one type of positive electrode lithium replenisher, or where the positive electrode contains two types of positive electrode lithium replenishers but they are not dispersed as in Example 1 of this disclosure (the total lithium replenishment capacity provided by the lithium replenishers in the positive electrode is approximately the same as in Examples 1 and 7), the positive electrode specific capacity (per gram) and initial Coulomb efficiency of the battery are improved, but the DCIR value of the battery is not significantly reduced, and the DCIR impedance of the battery still shows a high value (indicating poor output characteristics of the battery). However, by using a lithium replenishment layer containing the first positive electrode lithium replenishment material used in Example 1 of this disclosure as a base layer on the current collector, and further by placing a positive electrode material layer formed by dispersing the second positive electrode lithium replenishment material in the positive electrode active material on top of the base layer, the positive electrode specific capacity (per gram) can be improved and the impedance of the battery can be reduced. In addition, a similar trend can be understood from the comparison between Comparative Example 3 and Example 3, and between Comparative Example 6 and Example 4.

[0152] Furthermore, from a comparison of Examples 1, 9, 10, and 14, it is understood that when the total lithium replenishment capacity provided by the lithium replenisher in the positive electrode is approximately the same, and the composition of the lithium replenishment layer and the single-sided density of the positive electrode material layer are the same, a ratio of the lithium replenishment capacity of the first positive electrode lithium replenisher to the lithium replenishment capacity of the second positive electrode lithium replenisher within the range of (0.2~2):1 contributes to improving the overall performance of the lithium battery, and in particular to reducing the DCIR value of the battery and improving the utilization rate of the lithium replenisher.

[0153] From a comparison of Examples 1, 12, and 13 with Example 11, it is understood that when the composition, thickness, and surface density of each layer in the positive electrode are the same, but the Dv50 of the second positive electrode lithium replenisher and / or the positive electrode active material are different, having the Dv50 of the second positive electrode lithium replenisher in the range of 20 to 500 nm and the Dv50 of the positive electrode active material in the range of 0.2 to 5 μm contributes to improving the positive electrode specific capacity (per gram) of the battery, and further contributes to improving the energy density of the positive electrode and reducing the DCIR value of the battery.

[0154] Furthermore, a comparison between Example 1 and Example 7 reveals that, when other parameters in the positive electrode of the battery are the same, providing a conductive coating layer on the surface of the first positive electrode lithium replenisher contributes to reducing battery impedance and improving the utilization rate of the lithium replenishment material. A similar trend to that observed between Example 1 and Comparative Example 1 is also observed in the comparison between Example 20, in which the positive electrode active material was changed, and Comparative Example 7.

[0155] The above embodiments are merely illustrative of some embodiments of the present disclosure, and although the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present disclosure. Those skilled in the art can make various modifications and improvements without departing from the spirit of the present disclosure, all of which fall within the scope of the present disclosure. Therefore, the scope of the present disclosure shall be defined by the appended claims.

Claims

1. The positive electrode (100) The device comprises a positive electrode current collector (10), and lithium replenishment layers (20) and positive electrode material layers (30) sequentially laminated on at least one side of the positive electrode current collector (10), The lithium replenishment layer (20) comprises a first positive electrode lithium replenishment agent (201), and the positive electrode material layer (30) comprises a positive electrode active material (302) and a second positive electrode lithium replenishment agent (301). The initial Coulomb efficiency of the first positive electrode lithium replenisher (201) is less than 30%, and the second positive electrode lithium replenisher (301) is capable of decomposing to generate gas, positive electrode (100).

2. The first positive electrode lithium replenishing agent (201) is Li ６ CoO ４ , Li ２ MoO ３ , Li 5 FeO ４ , Li ６ MnO ４ , Li ２ NiO ２ , Li ２ CuO ２ , Li ３ PO ４ , Li ４ SiO ４ , Li ２ SiO ３ , Li ３ VO ４ , Li ２ VO ３ , Li 5 ReO ６ , Li ２ RuO ３ , Li ２ MnO ３ , Li ２ MoO ３ , Li ２ S, and one or more of LiF, the positive electrode (100) according to claim 1.

3. The positive electrode (100) according to claim 1 or 2, wherein the surface of the first positive electrode lithium replenisher (201) has a conductive coating layer.

4. The positive electrode (100) according to any one of claims 1 to 3, wherein the lithium replenishment layer (20) contains, by mass percentage, 50% to 90% of the first positive electrode lithium replenishment agent (201), 0% to 40% of the second positive electrode active material, 0.5% to 10% of the binder, and 0.5% to 10% of the conductive agent.

5. The second positive electrode lithium replenisher (301) is Li ２ CO ３ Li ３ N, Li ２ O ２ Li ２ O, Li ２ C ２ O ４ Li ２ C ４ O ４ Li ２ C ３ O 5 , and Li ２ C ４ O ６ A positive electrode (100) according to any one of claims 1 to 4, comprising one or more of the following.

6. The positive electrode (100) according to any one of claims 1 to 5, wherein in the positive electrode material layer (30), the Dv50 of the second positive electrode lithium replenisher (301) is 20 to 500 nm, and the Dv50 of the positive electrode active material (302) is 0.2 to 5 μm.

7. The positive electrode (100) according to any one of claims 1 to 6, wherein in the positive electrode material layer (30), the total mass of the second positive electrode lithium replenisher (301) is 0.5% to 5% of the total mass of the positive electrode active material (302).

8. A positive electrode (100) according to any one of claims 1 to 7, wherein the ratio of the lithium replenishment capacity provided by the first positive electrode lithium replenisher (201) to the lithium replenishment capacity provided by the second positive electrode lithium replenisher (301) is (0.2 to 2):

1.

9. The positive electrode (100) according to any one of claims 1 to 8, wherein the single-sided surface density of the positive electrode material layer (30) is greater than the single-sided surface density of the lithium replenishment layer (20).

10. The single-sided surface density of the lithium replenishment layer (20) is 0.5 to 50 g / m². ２ The positive electrode (100) according to any one of claims 1 to 9.

11. The single-sided surface density of the lithium replenishment layer (20) is 0.5 to 20 g / m². ２ The positive electrode (100) according to claim 10.

12. The positive electrode (100) according to any one of claims 1 to 11, wherein the thickness of one side of the lithium replenishment layer (20) is 0.1 to 100 μm.

13. The positive electrode (100) according to claim 12, wherein the thickness of one side of the lithium replenishment layer (20) is 0.5 to 10 μm.

14. The positive electrode (100) according to any one of claims 1 to 13, wherein the positive electrode material layer (30) includes n (n≧2) positive electrode material sublayers, and in the direction from the positive electrode current collector (10) toward the positive electrode material layer (30), the mass ratio of the second positive electrode lithium replenisher (301) to the positive electrode active material (302) tends to increase in each positive electrode material sublayer.

15. The positive electrode (100) according to any one of claims 1 to 13, wherein the positive electrode material layer (30) includes n (n≧2) positive electrode material sublayers, and in the direction from the positive electrode current collector (10) toward the positive electrode material layer (30), the mass ratio of the second positive electrode lithium replenisher (301) to the positive electrode active material (302) in each positive electrode material sublayer increases sequentially from layer to layer.

16. Of the n positive electrode material sublayers, at least two adjacent layers are A ｍ / (D ｍ / D ｍ－１ )-A ｍ－１ ≧5% Satisfying the conditions, A ｍ－１ A is the mass ratio of the second positive electrode lithium replenisher (301) in the (m-1)th positive electrode material sublayer to the total amount of the second positive electrode lithium replenisher (301) in the positive electrode material layer (30), ｍ D is the mass ratio of the second positive electrode lithium replenisher (301) in the m-th positive electrode material sublayer to the total amount of the second positive electrode lithium replenisher (301) in the positive electrode material layer (30), and D ｍ－１ D is the thickness of the (m-1)th positive electrode material sublayer. ｍ is the thickness of the m-th positive electrode material sublayer, where m is an integer in the range of 2 to n. The positive electrode (100) according to claim 14 or 15, wherein on the same side as the positive electrode current collector (10), the (m-1)th layer is closer to the positive electrode current collector (10) than the mth layer.

17. In the aforementioned n positive electrode material sublayers, any two adjacent positive electrode material sublayers are A ｍ / (D ｍ / D ｍ－１ )-A ｍ－１ ≧5% A positive electrode (100) according to claim 16 that satisfies the following conditions.

18. The positive electrode (100) according to any one of claims 15 to 17, wherein the mass percentage of the positive electrode active material (302) in each positive electrode material sublayer exceeds 80%.

19. A lithium battery (1) comprising the positive electrode (100) according to any one of claims 1 to 18.

20. A device (2) comprising the lithium battery (1) according to claim 19, wherein the device (2) is an electrical device or an energy storage system.

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