Positive electrode, lithium battery and device

Abstract

A positive electrode, a lithium battery and a device. A positive electrode comprises a positive electrode current collector, and a lithium replenishment layer and a positive electrode material layer which are sequentially stacked on at least one side of the positive electrode current collector, wherein the lithium replenishment layer comprises a first positive electrode lithium replenishment agent, the positive electrode material layer comprises a positive electrode active material and a second positive electrode lithium replenishment agent, the initial coulombic efficiency of the first positive electrode lithium replenishment agent is less than 30%, and the second positive electrode lithium replenishment agent can be decomposed to generate gas.

Description

Positive electrode, lithium battery and device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on October 31, 2023, with application number 202311444331.X and application name “Positive Electrode, Lithium Battery and Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present disclosure relates to the technical field of lithium-ion batteries, and in particular to a positive electrode, a lithium battery, and a device. Background Art

[0003] During the first charge of a lithium battery, a solid electrolyte film (SEI film) forms on the surface of the negative electrode, which consumes the active lithium ions in the lithium battery and reduces the battery's initial coulombic efficiency and energy density. In order to compensate for the irreversible consumption of active lithium during the first charge, the industry has adopted the measure of pre-adding a lithium replenisher that can provide active lithium ions to the lithium battery. Battery lithium replenishment methods are generally divided into positive electrode lithium replenishment and negative electrode lithium replenishment. Compared with the negative electrode lithium replenishment method of using highly chemically active metallic lithium to directly pre-lithiate the negative electrode, positive electrode lithium replenishment is safer and more compatible with existing battery preparation processes.

[0004] Among them, positive electrode lithium replenishment technology involves introducing a positive electrode lithium replenisher into the battery's positive electrode that undergoes an irreversible delithiation reaction during the initial charge, replenishing active lithium ions in the lithium battery. Positive electrode lithium replenishers are mainly divided into two categories. The first category is lithium-rich materials with low initial coulombic efficiency. After releasing lithium ions at a certain voltage, a portion of the main structure or delithiation products remains on the positive electrode side. The second category is sacrificial lithium replenishers that decompose at a certain voltage to produce lithium ions and gas. However, the use of either type of positive electrode lithium replenisher in a battery alone presents certain problems. For example, when using the first type of positive electrode lithium replenisher, the mixing of the positive electrode active material with the first type of positive electrode lithium replenisher increases the positive electrode liquid phase diffusion impedance, thereby reducing battery power performance. For example, the positive electrode coating formed by the mixing of the second type of positive electrode lithium replenisher with the positive electrode active material is in direct contact with the positive electrode current collector, making it difficult for the gases generated by its decomposition to be smoothly discharged. The residual gas will also increase the battery impedance and reduce the battery power performance.

[0005] Therefore, it is necessary to develop a solution that can take into account both good positive electrode lithium replenishment effect and battery power performance.

[0006] Summary of the Invention

[0007] In view of this, the present disclosure introduces for the first time a lithium-supplementing material with low coulombic efficiency and a sacrificial lithium-supplementing agent that can decompose and produce gas into the positive electrode of the battery at the same time, and through the reasonable arrangement of the distribution positions of the two, the battery can have both high battery energy density and good battery power performance.

[0008] Specifically, the first aspect of the present disclosure provides a positive electrode, including a positive electrode current collector and a lithium replenishing layer and a positive electrode material layer stacked in sequence on at least one side of the positive electrode current collector, wherein the lithium replenishing layer contains a first positive electrode lithium replenishing agent, and the positive electrode material layer contains a positive electrode active material and a second positive electrode lithium replenishing agent, wherein the first positive electrode lithium replenishing agent has a first coulombic efficiency of less than 30%, and the second positive electrode lithium replenishing agent can decompose to generate gas.

[0009] In the above-mentioned battery positive electrode provided by the embodiment of the present disclosure, the first positive electrode lithium replenisher and the second positive electrode lithium replenisher are simultaneously introduced and arranged in layers as described above, which can reduce the problems of high battery impedance and poor power performance caused by using the first and second positive electrode lithium replenishers alone, so that the battery has both high energy density and good power performance.

[0010] In one possible embodiment, the first positive electrode lithium supplement includes one or more of Li6CoO4, Li2MoO3, Li5FeO4, Li6MnO4, Li2NiO2, Li2CuO2, Li3PO4, Li4SiO4, Li2SiO3, Li3VO4, Li2VO3, Li5ReO6, Li2RuO3, Li2MnO3, Li2MoO3, Li2S, and LiF.

[0011] In a possible embodiment, the surface of the first positive electrode lithium supplement has a conductive coating layer.

[0012] In one possible embodiment, the lithium replenishing layer contains the following components in percentage by weight: 50%-90% of the first positive electrode lithium replenishing agent, 0-40% of the second positive electrode active material, 0.5-10% of the binder, and 0.5-10% of the conductive agent.

[0013] In a possible embodiment, the second positive electrode lithium supplement includes one or more of Li2CO3, Li3N, Li2O2, Li2O, Li2C2O4, Li2C4O4, Li2C3O5, and Li2C4O6.

[0014] In a possible embodiment, in the positive electrode material layer, the Dv50 of the second positive electrode lithium supplement is 20-500 nm, and the Dv50 of the positive electrode active material is 0.2-5 μm.

[0015] In a possible implementation, in the positive electrode material layer, the total mass of the second positive electrode lithium replenisher is 0.5-5% of the total mass of the positive electrode active material.

[0016] In a possible embodiment, the ratio of lithium replenishing capacity that can be provided by the first positive electrode lithium replenishing agent and the second positive electrode lithium replenishing agent is (0.2-2):1.

[0017] In a possible implementation, the single-surface areal density of the positive electrode material layer is greater than the single-surface areal density of the lithium supplement layer.

[0018] In one possible embodiment, the single-surface density of the lithium supplement layer is 0.5-50 g / m 2 .

[0019] In one possible embodiment, the single-surface density of the lithium supplement layer is 0.5-20 g / m 2 .

[0020] In a possible embodiment, the thickness of a single surface of the lithium replenishing layer is 0.1-100 μm.

[0021] In a possible implementation, the single-side thickness of the lithium replenishing layer is 0.5-10 μm.

[0022] In one possible embodiment, the positive electrode material layer includes n positive electrode material sublayers, n≥2, wherein the mass ratio of the second positive electrode lithium supplement to the positive electrode active material in each positive electrode material sublayer tends to increase from the positive electrode current collector toward the positive electrode material layer.

[0023] In one possible embodiment, the positive electrode material layer includes n positive electrode material sublayers, where n≥2, wherein the mass ratio of the second positive electrode lithium replenisher to the positive electrode active material in each positive electrode material sublayer increases layer by layer from the positive electrode current collector toward the positive electrode material layer.

[0024] In a possible embodiment, among the n layers of positive electrode material sub-layers, at least two adjacent layers satisfy the following conditions: m / (D m / D m-1 )-A m-1 ≥5%;

[0025] Among them, A m-1 A is the mass ratio of the second positive electrode lithium replenisher in the m-1th positive electrode material sublayer to the total second positive electrode lithium replenisher in the positive electrode material layer, m is the mass ratio of the second positive electrode lithium replenisher in the mth positive electrode material sublayer to the total second positive electrode lithium replenisher in the positive electrode material layer, D m-1 is the thickness of the m-1th positive electrode material sublayer, D m is the thickness of the mth positive electrode material sublayer, m is any integer from 2 to n; on the same side of the positive electrode current collector, the m-1th positive electrode material sublayer is closer to the positive electrode current collector than the mth positive electrode material sublayer.

[0026] In a possible embodiment, among the n layers of positive electrode material sub-layers, any two adjacent layers of the positive electrode material sub-layers satisfy: Am / (D m / D m-1 )-A m-1 ≥5%.

[0027] In a possible implementation, the mass proportion of the positive electrode active material in each of the positive electrode material sub-layers is greater than 80%.

[0028] In a second aspect, the present disclosure provides a lithium battery, comprising the positive electrode as described in the first aspect of the present disclosure.

[0029] Due to the use of the above-mentioned positive electrode, the lithium battery can achieve both high energy density and good power performance.

[0030] In a third aspect, the present disclosure provides a device having a lithium battery as described in the second aspect of the present disclosure, which device is an electrical device or an energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG1 is a schematic structural diagram of a positive electrode provided in an embodiment of the present disclosure.

[0032] FIG2 is another schematic structural diagram of a positive electrode provided in an embodiment of the present disclosure.

[0033] FIG3 is a schematic structural diagram of a lithium battery provided in an embodiment of the present disclosure.

[0034] FIG4 is a structural block diagram of a device provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0035] The technical solutions of the embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0036] Referring to Figures 1 and 2 , an embodiment of the present disclosure provides a positive electrode 100 comprising a positive electrode current collector 10, and a lithium replenishing layer 20 and a positive electrode material layer 30 stacked sequentially on at least one side of the positive electrode current collector 10. Specifically, on the same side of the positive electrode current collector 10, the lithium replenishing layer 20 is closer to the positive electrode current collector 10 relative to the positive electrode material layer 30, while the positive electrode material layer 30 is further away from the positive electrode current collector 10 relative to the lithium replenishing layer 20. The lithium replenishing layer 20 contains a first positive electrode lithium replenishing agent 201, and the positive electrode material layer 30 contains a positive electrode active material 302 and a second positive electrode lithium replenishing agent 301. The first positive electrode lithium replenishing agent 201 has a first coulombic efficiency of less than 30%, and the second positive electrode lithium replenishing agent 301 can decompose to release lithium ions and generate gas.

[0037] The above-mentioned positive electrode 100 contains two types of positive electrode lithium replenishing agents at the same time, and the second positive electrode lithium replenishing agent 301 that can decompose and produce gas is arranged in the positive electrode material layer 30 away from the positive electrode current collector 10, and the first positive electrode lithium replenishing agent 201 with low initial coulombic efficiency is arranged in the lithium replenishing layer 20 close to the positive electrode current collector 10. On the one hand, compared with the existing positive electrode having only the positive electrode material layer 30, under the condition that the total lithium replenishing capacity remains unchanged, the positive electrode of the present disclosure introduces two types of positive electrode lithium replenishing agents at the same time, the addition amount of the second positive electrode lithium replenishing agent 301 is reduced, and the decomposition gas production is correspondingly reduced; on the other hand, because the positive electrode material layer 30 containing the second positive electrode lithium replenishing agent 301 is arranged on the surface of the positive electrode 100 and away from the positive electrode current collector 10, the discharge path of the gas released by its decomposition is shortened, which is more conducive to gas discharge. In this way, the battery polarization is reduced during its decomposition process, the decomposition ratio and utilization rate of the second positive electrode lithium replenishing agent 301 are guaranteed, and the lithium replenishing utilization rate of the first positive electrode lithium replenishing agent 201 is also guaranteed. At the same time, less gas remains in the positive electrode 100, the battery impedance is also reduced, and the power performance is improved.

[0038] The first positive electrode lithium replenisher 201 typically has a particle size range of 3-10 μm. In existing positive electrodes with only a mixed layer containing the first positive electrode lithium replenisher 201 and a positive electrode active material, the particle size matching between the first positive electrode lithium replenisher 201 and the positive electrode active material 302 in the mixed layer is poor, and a dense stacking is generally not possible, which in turn reduces the compaction density of the positive electrode sheet and affects the battery energy density. Compared to existing positive electrodes with only a mixed layer containing the first positive electrode lithium replenisher 201 and a positive electrode active material, the presently disclosed positive electrode 100 simultaneously introduces two types of positive electrode lithium replenishers while maintaining the total lithium replenishment amount. The amount of the first positive electrode lithium replenisher 201 added is also reduced, and accordingly, the impact of the first positive electrode lithium replenisher 201 on reducing the positive electrode compaction density is also reduced. In addition, the first positive electrode lithium replenisher 201 generally has good conductivity after releasing active lithium ions. Placing it in the lithium replenisher layer 20 in contact with the positive electrode current collector 10 is also beneficial to ensuring a good conductive network of the overall positive electrode, thereby improving the utilization rate of the lithium replenisher, and at the same time reducing battery impedance and improving battery power performance.

[0039] Therefore, in the above-mentioned positive electrode 100 of the embodiment of the present disclosure, the first and second positive electrode lithium supplements are arranged in layers as above, which can produce a synergistic effect between the two types of lithium supplements and between the two types of lithium supplements and the battery positive electrode active material, so that the lithium supplement utilization rate of the two types of lithium supplements is improved, the energy density of the battery is improved, and the impedance of the battery is reduced and the power performance is improved.

[0040] It should be noted that the second positive electrode lithium replenisher 301 can decompose to release lithium ions. Since the main structure no longer exists after decomposing to release lithium ions and gas, lithium ions cannot be re-intercalated into it. This type of lithium replenisher can also be called a sacrificial lithium replenisher. Therefore, for this type of positive electrode lithium replenisher, the concept of "first coulombic efficiency" does not exist. The first positive electrode lithium replenisher 201, on the other hand, can release lithium ions at a higher voltage, leaving a portion of the main structure or delithiation products in the positive electrode 100. It has a certain ability to re-intercalate lithium ions, but its re-intercalation ability is relatively poor. In other words, its reversible lithium ion removal / intercalation ability is poor, and its first coulombic efficiency is low (less than 30%), far lower than the first coulombic efficiency of the positive electrode active material 302 (generally above 60%). The first coulombic efficiency of the first positive electrode lithium replenisher 201 can be determined by the ratio of the first-cycle discharge capacity to the first-cycle charge capacity of a battery made with it as the positive electrode active material 302. Specifically, the conditions for the first coulombic efficiency test of the first positive electrode lithium replenisher 201 are as follows: the buckle specification is CR2032, the positive electrode foil is carbon-coated aluminum foil, the positive electrode formula is the first positive electrode lithium replenisher 201: conductive agent: binder = 8:1:1 (mass ratio), the negative electrode is a metal lithium sheet, the separator is a PP separator with a thickness of 14μm, the electrolyte is 1M LiPF6 dissolved in a mixed solvent of EC / DMC / DEC / EMC = 1:1:1:1 (volume ratio), 0.1C charge to 4.5V, 0.1C discharge to 2.0V, the first cycle discharge capacity / first cycle charge capacity is the first coulombic efficiency.

[0041] In the embodiment of the present disclosure, the first positive electrode lithium supplement agent 201 may include one or more of Li6CoO4, Li2MoO3, Li5FeO4, Li6MnO4, Li2NiO2, Li2CuO2, Li3PO4, Li4SiO4, Li2SiO3, Li3VO4, Li2VO3, Li5ReO6, Li2RuO3, Li2MnO3, Li2MoO3, Li2S, LiF, etc., but is not limited thereto. In the embodiment of the present disclosure, the second positive electrode lithium supplement agent 301 may include one or more of Li2CO3, Li3N, Li2O2, Li2O, Li2C2O4, Li2C4O4, Li2C3O5, Li2C4O6, etc., but is not limited thereto.

[0042] The surface of the first positive lithium supplement 201 may or may not have a conductive coating. In some embodiments, the surface of the first positive lithium supplement 201 has a conductive coating. In this case, the first positive lithium supplement 201 has good conductivity, which helps ensure a good conductive network in the lithium supplement layer 20, reducing battery impedance and improving battery power performance.

[0043] In some embodiments of the present disclosure, the positive electrode active material 302 in the positive electrode material layer 30 can be selected from one or more of lithium iron phosphate, lithium iron manganese phosphate, lithium manganate, lithium cobalt oxide, lithium nickel manganate, lithium cobalt manganate ternary material, lithium nickel cobalt aluminum oxide ternary material, and lithium-rich lithium manganate. These positive electrode active materials 302 can be undoped or doped and modified, and their surfaces may or may not have a conductive coating. Generally, lithium iron phosphate and lithium iron manganese phosphate materials often have a conductive carbon coating.

[0044] In some embodiments of the present 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 the present disclosure, in the positive electrode material layer 30, the Dv50 of the second positive electrode lithium replenisher 301 is 20-500 nm, while the Dv50 of the positive electrode active material 302 is 0.2-5 μm. This allows the smaller-sized second positive electrode lithium replenisher 301 to be co-located with the larger-sized positive electrode active material 302, resulting in a high degree of particle size compatibility and a close stacking, without reducing the compaction density and energy density of the positive electrode 100. Furthermore, the second positive electrode lithium replenisher 301, which falls within this particle size range, produces an appropriate pore size after decomposition and releases active lithium, which can provide the positive electrode material layer 30 with appropriate porosity, thereby helping to reduce the overall impedance of the battery and improve power performance. Dv50 refers to the particle size corresponding to the cumulative volume fraction reaching 50% in a particle size distribution based on particle volume.

[0045] In the present disclosure, the lithium replenishing layer 20 may or may not contain the positive electrode active material 302. In the embodiment of the present disclosure, the lithium replenishing layer 20 may include the following components in percentage by weight: 50%-90% of the first positive electrode lithium replenishing agent 201, 0-40% of the second positive electrode active material, 0.5-10% of the binder, and 0.5-10% of the conductive agent. The selection range of the second positive electrode active material can refer to the description of the positive electrode active material 302 in the positive electrode material layer 30 in the previous part of the present disclosure. The second positive electrode active material and the positive electrode active material 302 in the positive electrode material layer 30 may be the same or different materials. Specifically, the mass percentage of the first positive electrode lithium replenishing agent 201 in the lithium replenishing layer 20 may be 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%, etc. The mass percentage of the binder or the conductive agent can be independently 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0046] In some embodiments of the present disclosure, when the content of the second positive electrode active material in the lithium replenishing layer 20 is zero, it is considered that the lithium replenishing layer 20 does not contain the positive electrode active material 302. This avoids the problem of increased positive electrode slurry viscosity and coating difficulties caused by directly mixing the first positive electrode lithium replenishing agent 201 with the positive electrode active material 302. The impact of deteriorating the compaction density of the positive electrode 100 due to poor matching of the particle sizes of the two is also greatly reduced. It also avoids the problem of increased positive electrode liquid phase diffusion impedance and slowed liquid phase lithium ion transmission speed caused by the dispersion of the first positive electrode lithium replenishing agent 201 in the positive electrode slurry, thereby helping to reduce battery impedance.

[0047] In some embodiments of the present disclosure, the single-surface areal density of the positive electrode material layer 30 is greater than that of the lithium-replenishing layer 20. The positive electrode material layer 30 is the primary capacity-providing layer of the battery, and having a higher single-surface areal density than the lithium-replenishing layer 20 helps ensure high energy density and discharge capacity of the battery. Taking the lithium-replenishing layer 20 as an example, the "single-surface areal density" here refers to the areal density of the lithium-replenishing layer 20 on one side of the positive electrode current collector 10, not the sum of the areal densities of the two lithium-replenishing layers 20 on either side of the positive electrode current collector 10.

[0048] In the embodiment of the present disclosure, the single surface density of the lithium supplement layer 20 is 0.5-50g / m 2 This can ensure that the lithium replenishing capacity of the first positive electrode lithium replenishing agent 201 is appropriate to a certain extent, and ensure that the overall performance of the lithium battery is good. It will not cause the lithium replenishing effect of the battery to be insignificant due to insufficient lithium replenishing capacity of the first positive electrode lithium replenishing agent 201, nor will it cause the lithium replenishing amount to exceed the reasonable level of the current battery design due to excessive addition of the first positive electrode lithium replenishing agent 201. In some embodiments, the single surface density of the lithium replenishing layer 20 is 0.5-20g / m 2 , for example, 0.8g / m 2 , 1.0g / m 2 , 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 、10.0g / m 2 、15.0g / m 2 , or 20.0g / m 2 This will help the battery to achieve both high positive electrode capacity and initial coulombic efficiency, as well as higher lithium supplement utilization.

[0049] In the embodiment of the present disclosure, the single surface density of the positive electrode material layer 30 is 50-1000 g / m 2 , for example, 60g / m 2 , 80g / m 2 , 100g / m 2 , 150g / m 2 , 200g / m 2 , 210g / m 2 , 220g / m 2 , 250g / m 2 , 300g / m 2 , 350g / m 2 , 400g / m 2 , 450g / m 2 In some embodiments, the single surface density of the positive electrode material layer 30 is 100-500 g / m 2 .

[0050] In the embodiment of the present disclosure, the thickness of a single surface of the lithium supplementing layer 20 is smaller than the thickness of a single surface of the positive electrode material layer 30. This is also conducive to ensuring a high energy density of the battery.

[0051] In the embodiment of the present disclosure, the thickness of the single side of the lithium replenishing layer 20 can be in the range of 0.1-100 μm, and can further be 0.1-50 μm, or 0.5-20 μm, etc. In some embodiments, the thickness of the single side of the lithium replenishing layer 20 is 0.5-10 μm, for example, specifically 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, etc. In this case, the lithium replenishing layer 20 containing the first positive electrode lithium replenishing agent 201 can ensure that the gas production of the positive electrode 100 is small and the battery impedance is low during the first charging of the battery, without reducing the total capacity of the positive electrode 100 or the energy density of the battery cell due to its excessive thickness. In the embodiment of the present disclosure, the single-sided thickness of the positive electrode material layer 30 can be in the range of 25-500μm, for example, 30μm, 50μm, 80μm, 100μm, 120μm, 150μm, 200μm, 220μm, 250μm, 300μm, 350μm, 400μm, or 450μm, etc.; in some embodiments, the single-sided thickness of the positive electrode material layer 30 is 50-250μm.

[0052] In the embodiment of the present disclosure, in the positive electrode material layer 30, the total mass of the second positive electrode lithium replenisher 301 is 0.5%-5% of the total mass of the positive electrode active material 302, for example, specifically 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. In this way, it can ensure that the second positive electrode lithium replenisher 301 replenishes the irreversible consumption of active lithium in the battery while not making the reversible capacity of the battery positive electrode 100 too small or the gas production of the positive electrode 100 too much. In this regard, whether the positive electrode material layer 30 is a single layer (as shown in Figure 1) or multiple layers (i.e., the number of layers ≥ 2, as shown in Figure 2), this parameter range applies. In some embodiments, in the positive electrode material layer 30, the total mass of the second positive electrode lithium replenisher 301 is 1-5% of the total mass of the positive electrode active material 302.

[0053] In the embodiment of the present disclosure, in the positive electrode 100, the ratio of the lithium replenishing capacity that can be provided by the first positive electrode lithium replenisher 201 and the second positive electrode lithium replenisher 301 is (0.2-2):1. In this case, it is more conducive to improving the comprehensive performance of the lithium battery, especially to reducing the DCIR value of the battery and improving the utilization rate of the lithium replenisher. Among them, the DCIR value represents the direct current internal resistance (DCIR) of the battery, which is one of the important parameters for measuring the performance of lithium-ion batteries. The measurement of the DCIR value takes into account all components of the battery internal resistance, so it is also called dynamic resistance. The size of the DCIR value has an important influence on the performance and service life of the battery. The smaller the DCIR value, the better the charge and discharge performance of the battery and the longer the service life. The larger the DCIR value, the worse the battery power performance. Among them, the lithium replenishing capacity provided by each lithium replenisher is equal to the product of its mass and its gram capacity. The gram capacity here is calculated according to the number of active lithium ions actually removed by each lithium replenisher when replenishing lithium, which is well known in the industry. For example, for Li5FeO4, its gram capacity corresponds to its theoretical gram capacity for releasing 4 lithium ions; for Li6CoO4, its gram capacity corresponds to its theoretical gram capacity for releasing 5 lithium ions; for Li2CuO2, its gram capacity corresponds to its theoretical gram capacity for releasing 1 lithium ion; for Li2CO3, its gram capacity corresponds to its theoretical gram capacity for releasing 2 lithium ions; for Li2C2O4, its gram capacity corresponds to its theoretical gram capacity for releasing 2 lithium ions; for Li3N, its gram capacity corresponds to its theoretical gram capacity for releasing 3 lithium ions.

[0054] In the present disclosure, when the positive electrode material layer 30 is a single layer (as shown in FIG1 ), the second positive electrode lithium replenisher 301 is uniformly dispersed in the positive electrode active material 302. In some embodiments of the present disclosure, the positive electrode material layer 30 is multi-layered, comprising n positive electrode material sub-layers, where n ≥ 2 (as shown in FIG2 ). The mass ratio of the second positive electrode lithium replenisher 301 to the positive electrode active material 302 in each positive electrode sub-coating layer increases from the positive electrode current collector 10 toward the lithium replenisher layer 20 (i.e., from the positive electrode current collector 10 toward the positive electrode material layer 30, as indicated by the arrows in FIG2 ).

[0055] The following explains the increasing trend of the above parameters. From the positive electrode current collector 10 to the lithium replenishing layer 20, each sub-coating of the positive electrode material layer 30 can be sequentially recorded as 31, 32...3n. In this way, the surface of the positive electrode current collector 10 is sequentially provided with the lithium replenishing layer 20, the first positive electrode material sub-layer 31, the second positive electrode material sub-layer 32, ..., the nth positive electrode material sub-layer 3n. If the mass ratio of the second positive electrode lithium replenishing agent 301 to the positive electrode active material 302 in the first positive electrode material sub-layer 31 is recorded as X1, the mass ratio of the second positive electrode lithium replenishing agent 301 to the positive electrode active material 302 in the second positive electrode material sub-layer 32 is recorded as X2, ..., the mass ratio of the second positive electrode lithium replenishing agent 301 to the positive electrode active material 302 in the nth positive electrode material sub-layer 3n is recorded as X n , then the above “increasing trend” can be expressed as: X1≤X2≤X3…≤X n , and X n >X1, where X1 is greater than 0. For example, the above “increasing trend” may be: first increasing, then unchanged, then increasing, or first unchanged, then increasing in sequence, or first unchanged, then increasing, then unchanged, then increasing, or a non-sequential increasing method such as increasing layer by layer (e.g., X1<X2<X3…<X n ).

[0056] The second positive electrode lithium replenisher 301 decomposes at a voltage greater than its delithiation potential to produce active lithium ions to replenish the battery, while also releasing gas. Therefore, after decomposition, it can leave pores at its original location, increasing the porosity of each positive electrode material sublayer. The present disclosure controls the mass ratio of the second positive electrode lithium replenisher 301 to the positive electrode active material 302 in each positive electrode material sublayer to increase in the direction away from the positive electrode current collector 10. This not only facilitates the smooth discharge of 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, but also reduces the degree of battery polarization caused by residual gas. Furthermore, after the decomposition of this type of lithium replenisher, the pores created in each positive electrode material sublayer also form a gradient pore structure. That is, the number of pores and porosity in the positive electrode material sublayer close to the positive electrode current collector 10 are fewer, while the porosity of the positive electrode material sublayer further away from the positive electrode current collector 10 is higher. The gradient pore structure helps to increase the overall porosity of the positive electrode 100 and reduce its pore tortuosity, thereby reducing the overall impedance of the battery and improving the power performance of the battery.

[0057] In some embodiments of the present disclosure, the mass ratio of the second positive lithium replenisher 301 to the positive active material 302 in each positive sub-coating increases layer by layer from the positive current collector 10 toward the lithium replenisher layer 20 (i.e., from the positive current collector 10 toward the positive electrode material layer 30, as indicated by the arrow in FIG2 ). This facilitates the smoother discharge of gases generated during the decomposition of the second positive lithium replenisher 301 in the positive electrode material layer 30. After decomposition, the second positive lithium replenisher 301 imparts a pore structure to the positive electrode material layer 30 in which the porosity increases in the direction of the arrow, further contributing to reduced battery impedance.

[0058] In some embodiments of the present disclosure, among n layers of positive electrode material sub-layers, at least two adjacent layers satisfy: A m / (D m / D m-1 )-A m-1 ≥5%; among them, A m-1 A is the mass ratio of the second positive electrode lithium replenishing agent 301 in the m-1th positive electrode material sublayer to the total second positive electrode lithium replenishing agent 301 in the positive electrode material layer 30, m is the mass ratio of the second positive electrode lithium replenishing agent 301 in the mth positive electrode material sublayer to the total second positive electrode lithium replenishing agent 301 in the positive electrode material layer 30, D m-1 is the thickness of the m-1th positive electrode material sublayer, D m is the thickness of the mth positive electrode material sublayer, m is any integer from 2 to n; on the same side of the positive electrode current collector 10, the m-1th positive electrode material sublayer is closer to the positive electrode current collector 10 than the mth positive electrode material sublayer. That is, when the thicknesses of the positive electrode material sublayers are substantially the same, at least two adjacent layers of the 1st to nth positive electrode material sublayers satisfy A m -A m-1≥5%, m is an integer between 2 and n. In this way, after the second positive electrode lithium supplement 301 is decomposed, the porosity of at least two adjacent positive electrode material sublayers can be clearly distinguished. The above-mentioned gradient pore structure has a better effect of reducing battery impedance and improving power performance. In some embodiments of the present disclosure, among the n layers of positive electrode material sublayers, any two adjacent layers of positive electrode material sublayers meet the following requirements: 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%, for example, 10%, 15%, 20%, 25%, 30%, 40%, 50%, or 60%, etc.

[0059] For example, in some embodiments, when the thickness of each cathode material sub-layer is substantially the same (ie, D m / D m-1 =1), the difference in mass percentage between the second positive electrode lithium replenishing agent 301 in any two adjacent positive electrode material sub-layers and the total mass of the second positive electrode lithium replenishing agent 301 in the positive electrode material layer 30 is greater than 5%. m / D m-1 = 1, among the n layers of positive electrode material sub-layers, any two adjacent layers of positive electrode material sub-layers satisfy: A m -A m-1 ≥5%, m is any integer from 2 to n. If the mass ratio of the second positive electrode lithium replenisher 301 in the first positive electrode material sublayer 31 to the total mass ratio of the second positive electrode lithium replenisher 301 in the positive electrode material layer 30 is recorded as A1, the mass ratio of the second positive electrode lithium replenisher 301 in the second positive electrode material sublayer 32 to the total mass ratio of the second positive electrode lithium replenisher 301 in the positive electrode material layer 30 is recorded as A2, ..., the mass ratio of the second positive electrode lithium replenisher 301 in the nth positive electrode material sublayer 3n to the total mass ratio of the second positive electrode lithium replenisher 301 in the positive electrode material layer 30 is recorded as A n , if D m / D m-1 =1, then |A2-A1|, |A3-A2|, ... |A n -A n-1 |are all ≥5%, preferably ≥10%. Wherein, 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%.

[0060] In the disclosed embodiment, the mass ratio of the positive electrode active material 302 in each positive electrode material sublayer is greater than 80%, preferably greater than 90%. This is conducive to ensuring that the reversible capacity provided by each positive electrode material sublayer is high, thereby ensuring a high reversible capacity of the overall positive electrode 100. Taking the first positive electrode material sublayer 31 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 is greater than 80%, and further greater than 90%.

[0061] In the present disclosure, the single-surface areal density of each positive electrode material sub-layer may be equal or unequal; in some embodiments of the present disclosure, the single-surface areal density of each positive electrode material sub-layer is equal. This helps to ensure that their stacked structure is more stable. It should be noted that the single-surface areal density mentioned here and the single-surface areal density of the positive electrode material layer 30 and the lithium supplement layer 20 mentioned above in this disclosure refer to the single-surface areal density of each positive electrode material sub-layer before the battery undergoes the first cycle (i.e., before formation).

[0062] In the present disclosure, the positive electrode current collector 10 may include, but is not limited to, aluminum foil, aluminum alloy foil, a polymer film coated with aluminum, or the aforementioned materials with a carbon coating on the surface. In some embodiments of the present disclosure, the positive electrode current collector 10 is aluminum foil. In the present disclosure, a stacked structure of a lithium replenishing layer 20 and a positive electrode material layer 30 may be formed on one surface of the positive electrode current collector 10 (as shown in Figures 1 and 2), or a stacked structure of a lithium replenishing layer 20 and a positive electrode material layer 30 may be formed on both opposite sides of the positive electrode current collector 10.

[0063] In the present disclosure, the lithium replenishing layer 20 may also contain a conductive agent; the positive electrode material layer 30 may also contain a conductive agent. Each conductive agent can be independently selected from one or more of conductive carbon black (such as acetylene black, Ketjen black, Super P, 350G carbon black, etc.), carbon nanotubes, graphene, carbon fibers, etc. Among them, the carbon nanotubes can be specifically single-walled carbon nanotubes or multi-walled carbon nanotubes, and the carbon fibers can be specifically arrayed carbon fibers. In some embodiments, the lithium replenishing layer 20 and the positive electrode material layer 30 may also contain one or more of a binder and a dispersant. Among them, each binder can be independently selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyolefins (such as polyethylene (PE), polypropylene (PP)), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyimide (PI), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), sodium alginate (SA), gelatin, etc., but is not limited thereto. Each dispersant can be selected from one or more of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), etc.

[0064] The lithium replenishing layer 20 can be formed by coating a primer slurry containing a first positive electrode lithium replenishing agent 201, a conductive agent, and a solvent, followed by drying. The coating method can include, but is not limited to, a combination of one or more methods such as spin coating, brush coating, spray coating, dip coating, and scraping. Similarly, the positive electrode material layer 30 can be formed by coating a positive electrode slurry containing a positive electrode active material 302, a second positive electrode lithium replenishing agent 301, a conductive agent, and a solvent, followed by drying. When the positive electrode material layer 30 is a single layer, the positive electrode slurry is of one type. When the positive electrode material layer 30 is a multi-layer layer, the type of positive electrode slurry used corresponds to the number of layers of the positive electrode material layer 30.

[0065] The solvents contained in each slurry may be the same or different and may be independently selected from one or more of pyrrolidones (e.g., N-methylpyrrolidone (NMP), N-ethylpyrrolidone, etc.), cyclic ethers (e.g., tetrahydrofuran, methyltetrahydrofuran), dimethyl sulfoxide, ketones (e.g., acetone, butanone), lactones (e.g., butyrolactone, caprolactone), etc., but are not limited thereto. The solid content of each slurry is not particularly limited, as long as the fluidity and uniformity of the slurry coating are met. Generally, the solid content of the primer slurry may be 1-50%. The solid content of the positive electrode slurry is in the range of 50%-70%.

[0066] In addition, each slurry can be applied simultaneously or sequentially, or applied on the coating formed by drying the previous slurry. Taking the case of a positive electrode material layer 30 as an example, a positive electrode slurry can be directly applied on the primer slurry (can be applied simultaneously or sequentially), and then dried together to remove the solvent, and then rolled. If double-sided coating is required, the above operation can be repeated on the other side of the positive electrode current collector 10. Alternatively, the above primer slurry can be applied on one side of the positive electrode current collector 10 and dried to form a lithium replenishing layer 20, and then the positive electrode slurry can be applied on the lithium replenishing layer 20 and dried to form a positive electrode material layer 30, and then rolled.

[0067] Referring to Figure 3 , another embodiment of the present disclosure provides a lithium battery 1 including the aforementioned positive electrode 100. Due to the use of the aforementioned positive electrode 100, the lithium battery 1 utilizes both types of lithium supplements at high rates, resulting in a high reversible capacity and improved energy density. Furthermore, the battery has low impedance and excellent power performance.

[0068] In the embodiment of the present disclosure, the lithium battery 1 further includes a negative electrode 11 , and a separator 111 and an electrolyte 112 disposed between the positive electrode 100 and the negative electrode 11 .

[0069] Among them, the negative electrode 11 generally includes a negative electrode current collector and a negative electrode material layer provided on the surface of at least one side of the negative electrode current collector. The negative electrode material layer generally contains a negative electrode active material, a conductive agent, and a binder. In the embodiment of the present disclosure, the negative electrode active material can be selected from one or more of carbon materials, silicon-based materials, tin-based materials, etc. Among them, the carbon material includes one or more of soft carbon, hard carbon, graphite, mesophase carbon microbeads, etc. The silicon-based material may include one or more of elemental silicon, silicon alloy, silicon oxide, silicon-carbon composite material, etc. The tin-based material may include one or more of elemental tin, tin oxide, tin-based alloy, tin-carbon compound, etc.

[0070] The separator 111 is used to separate the positive electrode 100 and the negative electrode 11, maintaining the insulation and liquid retention properties between the two. The separator 111, the positive electrode 100, and the negative electrode 11 together constitute the battery cell, which is housed in the battery casing and is soaked by the electrolyte 112 contained in the casing. In some embodiments of the present disclosure, the lithium battery 1 can be assembled by the following method: the positive electrode 100, the separator 111, and the negative electrode 11 are stacked in sequence to form a battery cell; the battery cell is housed in a battery casing, and the electrolyte is injected, and then the battery casing is sealed to produce a battery. The battery cell can be wound or laminated.

[0071] The separator can be any separator material used in batteries. For example, the separator may include, but is not limited to, single-layer PP (polypropylene) film, single-layer PE (polyethylene) film, double-layer PP / PE, double-layer PP / PP, triple-layer PP / PE / PP, and other polymer separators, or non-woven fabrics. The electrolyte includes an electrolyte salt and an organic solvent. The specific types and compositions of the electrolyte salt and organic solvent are conventional in the battery field and can be selected according to actual needs.

[0072] Referring to Figure 4 , an embodiment of the present disclosure further provides a device 2 comprising the lithium battery 1 described above. The device 2 can be a power-consuming device such as a vehicle (e.g., automobile, motorcycle, bicycle, etc.), an electric toy, a consumer electronics product (e.g., a mobile phone, laptop, tablet computer, pen-type computer, e-book player, wearable device, etc.), or an energy storage system. Powered by the lithium battery 1, the power-consuming device has a long operating life and fast charging speed.

[0073] The technical solution of the present disclosure is further described below in conjunction with a number of specific embodiments.

[0074] Example 1

[0075] A method for preparing a positive electrode, comprising:

[0076] The first positive electrode lithium replenishing agent (specifically Li5FeO4 with a carbon coating layer on the surface, the mass proportion of the coating layer material is 3wt%) is mixed with 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, and stirred evenly to obtain a primer slurry. The primer slurry is sprayed on the surface of the positive electrode current collector - aluminum foil, and then dried to form an aluminum foil with a lithium replenishing layer; wherein the single-side surface density of the lithium replenishing layer is 2.41g / m 2 , the coating thickness is 3±1μm.

[0077] The positive electrode active material - lithium iron phosphate (LFP, Dv50 is 3μm) is mixed with a binder PVDF, a carbon nanotube conductive agent, a graphene conductive agent, a second positive electrode lithium supplement agent (specifically Li2CO3 with Dv50 of 200nm), and a solvent NMP in a mass ratio of 100:2.5:1:0.5:1:60 to prepare a positive electrode slurry; the positive electrode slurry is coated on the above-mentioned lithium supplement layer and dried to form a single-side surface density of 200g / m 2 positive electrode material layer.

[0078] Repeat the above steps of forming the lithium replenishing layer and the positive electrode material layer on the other side of the aluminum foil, followed by roller pressing to obtain a ready-to-use positive electrode. In this positive electrode, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to the second positive electrode lithium replenishing agent is approximately 1:1.

[0079] Preparation of a lithium battery:

[0080] (1) Preparation of negative electrode: The negative electrode active material graphite, binder SBR, thickener CMC, conductive agent carbon black and solvent H2O were mixed uniformly in a mass ratio of 100:2:2:1:120 to prepare a negative electrode slurry. The negative electrode slurry was applied to the negative electrode current collector - copper foil, and after drying, a single-side surface density of 100g / m 2 negative electrode material layer.

[0081] (2) Battery assembly: The positive electrode, separator (specifically, a PP separator with a thickness of 14 μm), and negative electrode are stacked in sequence to obtain a battery cell; the stacked battery cell is then wound and placed in a battery casing. After assembly and drying, the prepared electrolyte is injected, and the battery casing is sealed with an air bag reserved to obtain a lithium battery for subsequent electrical performance testing.

[0082] Example 2

[0083] A preparation of a positive electrode, which differs from Example 1 in that: the positive electrode material layer is two layers, and a first positive electrode slurry and a second positive electrode slurry are simultaneously laminated and coated on one side of the lithium replenishing layer. After drying, the first positive electrode slurry forms a first positive electrode material sublayer, and the second positive electrode slurry forms a second positive electrode material sublayer. The first positive electrode material sublayer is close to the lithium replenishing layer, and the second positive electrode material sublayer is arranged on the side of the first positive electrode material sublayer away from the lithium replenishing layer; wherein the formula of the first positive electrode slurry in contact with the lithium replenishing layer is lithium iron phosphate: P VDF: carbon nanotubes: graphene: Li2CO3: NMP = 100: 2.6: 1: 0.5: 0.5: 60. The formula of the second positive electrode slurry away from the lithium supplement layer is lithium iron phosphate: PVDF: carbon nanotubes: graphene: Li2CO3: NMP = 100: 2.4: 1: 0.5: 1.5: 60. The surface density ratio of the first positive electrode material sublayer and the second positive electrode material sublayer is 1: 1. The single surface density of the total positive electrode material layer is still 200 g / m 2 In the positive electrode, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to that of the second positive electrode lithium replenishing agent is still 1:1.

[0084] According to the method described in Example 1, the positive electrode of Example 2 was assembled into a lithium battery.

[0085] Example 3

[0086] A method for preparing a positive electrode, comprising:

[0087] The first positive electrode lithium replenishing agent (specifically Li6CoO4 with a carbon coating layer on the surface, the coating material accounts for 2.5wt%) is mixed with a binder PVDF, a conductive agent carbon black, PVP, and NMP in a mass ratio of 10:1:1:0.2:90, and stirred evenly to obtain a primer slurry. The primer slurry is sprayed on the surface of the aluminum foil, and after drying, an aluminum foil current collector with a lithium replenishing layer is formed; wherein the single-side surface density of the lithium replenishing layer is 2.46g / m 2 , thickness is 3±1μm.

[0088] The positive electrode active material lithium iron phosphate (LFP, Dv50 is 3 μm) is mixed with the binder PVDF, carbon nanotubes, graphene, the second positive electrode lithium supplement (specifically Li2C2O4 with Dv50 of 150 nm), and the solvent NMP in a mass ratio of 100:2.5:1:0.5:1.4:60 to prepare a positive electrode slurry; the positive electrode slurry is applied on the above-mentioned lithium supplement layer, and after drying, a single-side surface density of 200 g / m is formed. 2 The total mass of the second positive electrode lithium supplement in the positive electrode material layer is 1.4% of the total mass of the positive electrode active material.

[0089] Repeat the above steps of forming the lithium replenishing layer and the positive electrode material layer on the other side of the aluminum foil, followed by roller pressing to obtain a positive electrode ready for use. In this positive electrode, the ratio of the lithium replenishing capacity of the first positive electrode replenishing agent to the second positive electrode replenishing agent is 1.2:1.

[0090] According to the method described in Example 1, the positive electrode of Example 3 was assembled into a lithium battery.

[0091] Example 4

[0092] A preparation of a positive electrode, which differs from Example 3 in that: the positive electrode material layer is two layers, and a double-layer coating is adopted, and the first positive electrode slurry and the second positive electrode slurry are simultaneously stacked and coated on one side of the lithium replenishing layer. After drying, the first positive electrode slurry forms a first positive electrode material sublayer, and the second positive electrode slurry forms a second positive electrode material sublayer. The first positive electrode material sublayer is close to the lithium replenishing layer, and the second positive electrode material sublayer is arranged on the side of the first positive electrode material sublayer away from the lithium replenishing layer; the formula of the first positive electrode slurry in contact with the lithium replenishing layer is lithium iron phosphate: P VDF: carbon nanotubes: graphene: Li2C2O4: NMP = 100: 2.6: 1: 0.5: 0.7: 60. The formula of the second positive electrode slurry away from the lithium supplement layer is lithium iron phosphate: PVDF: carbon nanotubes: graphene: Li2C2O4: NMP = 100: 2.4: 1: 0.5: 2.1: 60. The surface density ratio of the first positive electrode material sublayer and the second positive electrode material sublayer is controlled to be 1: 1. The single surface density of the total positive electrode material layer is still 200 g / m 2 In the positive electrode, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to that of the second positive electrode lithium replenishing agent is still 1.2:1.

[0093] According to the method described in Example 1, the negative electrode of Example 4 was assembled into a lithium battery.

[0094] Example 5

[0095] A method for preparing a positive electrode, comprising:

[0096] The first positive electrode lithium replenishing agent (specifically, Li2CuO2 without a coating layer) is mixed with a binder PVDF, a conductive agent carbon black, PVP, and NMP in a mass ratio of 10:1:1:0.2:90, and stirred evenly to obtain a primer slurry. The primer slurry is sprayed on the surface of an aluminum foil, and after drying, an aluminum foil current collector with a lithium replenishing layer is formed; wherein the single-side surface density of the lithium replenishing layer is 4g / m 2 , the coating thickness is 5±1μm.

[0097] The positive electrode active material lithium iron phosphate (LFP, Dv50 is 3μm) is mixed with the binder PVDF, carbon nanotubes, graphene, the second positive electrode lithium replenisher (specifically Li3N with Dv50 of 400nm), and the solvent NMP in a mass ratio of 100:2.5:1:0.5:1:60 to prepare a positive electrode slurry. The positive electrode slurry is applied to the above-mentioned lithium replenishing layer and dried to form a single-side surface density of 200g / m 2 positive electrode material layer.

[0098] Repeat the above steps of forming the lithium supplement layer and the positive electrode material layer on the other side of the aluminum foil, and then perform roller pressing to obtain the positive electrode to be used. According to the method described in Example 1, the positive electrode of Example 5 was assembled into a lithium battery.

[0099] Example 6

[0100] A preparation of a positive electrode, which differs from Example 5 in that: the positive electrode material layer is two layers, and a double-layer coating is adopted, and the first positive electrode slurry and the second positive electrode slurry are simultaneously stacked and coated on one side of the lithium replenishing layer. After drying, the first positive electrode slurry forms a first positive electrode material sublayer, and the second positive electrode slurry forms a second positive electrode material sublayer. The first positive electrode material sublayer is close to the lithium replenishing layer, and the second positive electrode material sublayer is arranged on the side of the first positive electrode material sublayer away from the lithium replenishing layer; wherein the formula of the first positive electrode slurry in contact with the lithium replenishing layer is Lithium iron phosphate: PVDF: carbon nanotubes: graphene: Li3N: NMP = 100: 2.6: 1: 0.5: 0.4: 60. The formula of the second positive electrode slurry away 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 surface density ratio of the first positive electrode material sublayer and the second positive electrode material sublayer is 1: 1. The single surface density of the total positive electrode material layer is still 200g / m 2 .

[0101] According to the method described in Example 1, the positive electrode of Example 6 was assembled into a lithium battery.

[0102] Example 7

[0103] The difference between Example 7 and Example 1 is that the first positive electrode lithium replenisher is Li5FeO4 without a conductive coating layer on the surface.

[0104] Example 8

[0105] The main difference between the positive electrode of Example 8 and Example 1 is that the lithium replenishing layer further contains positive electrode active material LFP.

[0106] The lithium replenishing layer is obtained by coating and drying the base coating slurry obtained by mixing the above-mentioned first positive electrode lithium replenishing agent with lithium iron phosphate (LFP, Dv50 is 3μm), binder PVDF, conductive agent carbon black, dispersant PVP, and solvent NMP in a mass ratio of 6:4:1:1:0.1:90. The single-side density of the lithium replenishing layer is 3.97g / m 2 , thickness is 4±1μm.

[0107] The positive electrode slurry with the same formulation as in Example 1 was coated on the lithium supplement layer and dried to form a single surface density of 198 g / m 2 positive electrode material layer.

[0108] Repeat the above steps of forming the lithium replenishing layer and the positive electrode material layer on the other side of the aluminum foil, and then perform roller pressing 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 second positive electrode lithium replenishing agent is still 1:1.

[0109] Example 9

[0110] The main difference between Example 9 and Example 1 is that in the positive electrode of Example 9, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to the second positive electrode lithium replenishing agent is 0.1:1. The formula composition of the primer slurry used to form the lithium replenishing layer in Example 9 is the same as that in Example 1, but the single-surface density of the lithium replenishing layer is 0.48g / m 2 , the coating thickness is 2±1μm.

[0111] The positive electrode active material lithium iron phosphate (LFP, Dv50 is 3 μm) is mixed with the binder PVDF, carbon nanotube conductive agent, graphene conductive agent, the second positive electrode lithium supplement agent (Li2CO3 with Dv50 of 200 nm), and the solvent NMP in a mass ratio of 100:2.5:1:0.5:2:60 to prepare a positive electrode slurry; the positive electrode slurry is coated on the above-mentioned lithium supplement layer and dried to form a single-side surface density of 200 g / m 2 The total mass of the second positive electrode lithium supplement in the positive electrode material layer is 2% of the total mass of the positive electrode active material.

[0112] Repeat the above steps of forming the lithium replenishing layer and the positive electrode material layer on the other side of the aluminum foil, and then perform roller pressing to obtain a positive electrode ready for use. In the positive electrode prepared in Example 9, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to the second positive electrode lithium replenishing agent is 0.1:1.

[0113] Example 10

[0114] The main difference between Example 10 and Example 1 is that the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to the second positive electrode lithium replenishing agent in Example 10 is 9:1. The formula composition of the primer slurry used to form the lithium replenishing layer in Example 10 is the same as that in Example 1, but the single-surface density of the lithium replenishing layer is 4.38 g / m 2 , the coating thickness is 5±1μm.

[0115] The positive electrode active material lithium iron phosphate (LFP, Dv50 is 3 μm) is mixed with the binder PVDF, carbon nanotube conductive agent, graphene conductive agent, the second positive electrode lithium supplement agent (Li2CO3 with Dv50 of 200 nm), and the solvent NMP in a mass ratio of 100:2.5:1:0.5:0.2:60 to prepare a positive electrode slurry; the positive electrode slurry is coated on the above-mentioned lithium supplement layer and dried to form a single-side surface density of 200 g / m 2 The total mass of the second positive electrode lithium supplement in the positive electrode material layer is 0.2% of the total mass of the positive electrode active material.

[0116] Repeat the above steps of forming the lithium replenishing layer and the positive electrode material layer on the other side of the aluminum foil, followed by roll pressing to obtain a ready-to-use positive electrode. In the positive electrode of Example 10, the lithium replenishing capacity ratio of the first positive electrode replenishing agent to the second positive electrode replenishing agent is 9:1; the total mass of the second positive electrode replenishing agent is 0.2% of the total mass of the positive electrode active material.

[0117] Example 11

[0118] The main difference between Example 11 and Example 1 is that the Dv50 of the second positive electrode lithium replenisher is 600 nm.

[0119] Example 12

[0120] The main difference between Example 12 and Example 1 is 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.

[0121] Example 13

[0122] The main difference between Example 13 and Example 1 is that the Dv50 of the second positive electrode lithium supplement is 500nm, and the Dv50 of the positive electrode active material - lithium iron phosphate (LFP) is 5μm.

[0123] Example 14

[0124] The main differences between the positive electrode of Example 14 and Example 1 are: in the positive electrode of Example 14, the total mass of the second positive electrode lithium replenisher is 0.5% of the total mass of the positive electrode active material; the ratio of the lithium replenishing capacity of the first positive electrode lithium replenisher to the second positive electrode lithium replenisher is approximately 3:1. The single surface density of the lithium replenisher layer is 3.65g / m 2, the thickness of single side is 4±1μm.

[0125] The positive electrode active material - lithium iron phosphate (LFP, Dv50 is 3μm) is mixed with a binder PVDF, a carbon nanotube conductive agent, a graphene conductive agent, a second positive electrode lithium supplement agent (specifically Li2CO3 with Dv50 of 200nm), and a solvent NMP in 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 on the above-mentioned lithium supplement layer and dried to form a single-side surface density of 200g / m 2 The total mass of the second positive electrode lithium supplement in the positive electrode material layer is 0.5% of the total mass of the positive electrode active material.

[0126] Repeat the above steps of forming the lithium supplement layer and the positive electrode material layer on the other side of the aluminum foil, and then roll-press to obtain the positive electrode to be used. According to the method described in Example 1, the positive electrode of Example 14 was assembled into a lithium battery.

[0127] Example 15

[0128] The main differences between Example 15 and Example 1 are: in the positive electrode of Example 15, the total mass of the second positive electrode lithium replenisher is 5% of the total mass of the positive electrode active material; the ratio of the lithium replenishing capacity of the first positive electrode lithium replenisher to the second positive electrode lithium replenisher is approximately 0.15:1. The single surface density of the lithium replenisher layer is 1.74g / m 2 , the thickness of single side is 2±1μm.

[0129] The positive electrode active material - lithium iron phosphate (LFP, Dv50 is 3μm) is mixed with a binder PVDF, a carbon nanotube conductive agent, a graphene conductive agent, a second positive electrode lithium supplement (specifically Li2CO3 with Dv50 of 200nm), and a solvent NMP in a mass ratio of 100:2.5:1:0.5:5:60 to prepare a positive electrode slurry; the positive electrode slurry is coated on the above-mentioned lithium supplement layer and dried to form a single-side surface density of 200g / m 2 The total mass of the second positive electrode lithium supplement in the positive electrode material layer is 5% of the total mass of the positive electrode active material.

[0130] Repeat the above steps of forming the lithium supplement layer and the positive electrode material layer on the other side of the aluminum foil, and then roll-press to obtain the positive electrode to be used. According to the method described in Example 1, the positive electrode of Example 15 was assembled into a lithium battery.

[0131] Example 16

[0132] The main difference between the positive electrode of Example 16 and Example 1 is that the lithium supplement layer also contains positive electrode active material (specifically LFP, Dv50 is 3μm), and the single surface density of the lithium supplement layer is 20g / m 2The thickness of the single surface is 12±1μm. The lithium replenishing layer is obtained by coating and drying the primer slurry obtained by mixing the above-mentioned first positive electrode lithium replenishing agent with LFP, binder PVDF, conductive agent carbon black, dispersant PVP, and solvent NMP in a mass ratio of 2:8:0.2:0.2:0.1:90. In addition, the single surface density of the positive electrode material layer is 180g / m 2 .

[0133] Correspondingly, in the positive electrode of Example 16, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to that of the second positive electrode lithium replenishing agent is approximately 2.12:1.

[0134] Example 17

[0135] The main difference between the positive electrode of Example 17 and Example 1 is that the single-surface density of the lithium supplement layer is 50g / m 2 The thickness of the single surface is 30±1μm. The lithium replenishing layer is obtained by coating and drying the primer slurry obtained by mixing the above-mentioned first positive electrode lithium replenishing agent with LFP, binder PVDF, conductive agent carbon black, dispersant PVP, and solvent NMP in a mass ratio of 0.8:9.2:0.2:0.2:0.1:90. In addition, the single surface density of the positive electrode material layer is 150g / m 2 .

[0136] In the positive electrode of Example 17, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to that of the second positive electrode lithium replenishing agent is approximately 2.55:1.

[0137] Example 18

[0138] The main difference between Example 18 and Example 1 is that in the positive electrode of Example 18, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to that of the second positive electrode lithium replenishing agent is about 2:1; wherein, the single surface density of the lithium replenishing layer is 4.81 g / m 2 , the thickness of single side is 5±1μm.

[0139] Example 19

[0140] The main difference between Example 19 and Example 2 in the preparation method is that the formula of the first positive electrode slurry in contact with the lithium replenishing layer is lithium iron phosphate: PVDF: carbon nanotubes: graphene: Li2CO3: NMP = 100: 2.6: 1: 0.5: 0.9: 60, and the formula of the second positive electrode slurry away from the lithium replenishing layer is lithium iron phosphate: PVDF: carbon nanotubes: graphene: Li2CO3: NMP = 100: 2.4: 1: 0.5: 1.1: 60.

[0141] In Example 19, the mass ratio of the second positive electrode lithium replenisher in the first positive electrode material sublayer formed by drying the first positive electrode slurry to the total mass ratio of the second positive electrode lithium replenisher in the positive electrode is 45%, and the mass ratio of the second positive electrode lithium replenisher in the second positive electrode material sublayer formed by drying the second positive electrode slurry to the total mass ratio of the second positive electrode lithium replenisher in the positive electrode is 55%. In addition, the surface density ratio of the first positive electrode material sublayer to the second positive electrode material sublayer remains 1:1, and the single surface surface density of the total positive electrode material layer remains 200g / m 2 ; In this positive electrode, the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to the second positive electrode lithium replenishing agent is still 1:1.

[0142] Example 20

[0143] A positive electrode, which differs from the positive electrode of Example 1 only in that the positive electrode active material is lithium manganese iron phosphate (LMFP) with a Dv50 of 1 μm.

[0144] Preparation of a lithium battery:

[0145] (1) Preparation of negative electrode: The negative electrode active material graphite, silicon-carbon composite material, binder SBR, thickener CMC, conductive agent carbon black and solvent H2O were mixed uniformly in a mass ratio of 90:10:2:2:1:120 to prepare a negative electrode slurry. The negative electrode slurry was applied to the negative electrode current collector - copper foil, and after drying, a single-side surface density of 80g / m 2 negative electrode material layer.

[0146] (2) Battery assembly: The positive electrode, separator (specifically, a PP separator with a thickness of 14 μm), and negative electrode are stacked in sequence to obtain a battery cell; the stacked battery cell is then wound and placed in a battery casing. After assembly and drying, the prepared electrolyte is injected, and the battery casing is sealed with an air bag reserved to obtain a lithium battery for subsequent electrical performance testing.

[0147] In order to highlight the beneficial effects of the present disclosure, the present disclosure also provides the following comparative examples 1-8.

[0148] Comparative Example 1

[0149] A preparation of a positive electrode, which is different from Example 1 in that: the positive electrode does not contain the first and second types of positive electrode lithium replenishers.

[0150] The preparation method of the positive electrode comprises: mixing lithium iron phosphate, PVDF as a binder, carbon nanotube conductive agent, graphene conductive agent, and NMP as a solvent in a mass ratio of 100:2.5:1:0.5:60 to prepare a positive electrode slurry. The positive electrode slurry is coated on an aluminum foil current collector and dried to form a single-side surface density of 200g / m 2 Repeat the above steps of forming the positive electrode material layer on the other side of the aluminum foil, and then roll-press to obtain the positive electrode.

[0151] According to the method described in Example 1, the positive electrode of Comparative Example 1 was assembled into a lithium battery.

[0152] Comparative Example 2

[0153] The difference between the positive electrode of Comparative Example 2 and Example 7 is that a mixed layer containing the first positive electrode lithium replenisher and the positive electrode active material is directly provided on the aluminum foil.

[0154] The preparation of the positive electrode in Comparative Example 2 specifically includes: mixing lithium iron phosphate, binder PVDF, carbon nanotube conductive agent, graphene conductive agent, first positive electrode lithium supplement agent (specifically Li5FeO4 without carbon coating layer on the surface, the coating layer material accounts for 3wt%), and solvent NMP in a mass ratio of 100:2.5:1:0.5:2:60 to prepare a positive electrode slurry. The positive electrode slurry is coated on an aluminum foil current collector and dried to form a single-side surface density of 200g / m 2 Repeat the above steps of forming the positive electrode material layer on the other side of the aluminum foil, and then roll-press to obtain the positive electrode.

[0155] According to the method described in Example 1, the positive electrode of Comparative Example 2 was assembled into a lithium battery.

[0156] Comparative Example 3

[0157] A positive electrode, which is different from Example 3 mainly in that a mixed layer containing a second positive electrode lithium replenisher and a positive electrode active material is directly provided on the aluminum foil.

[0158] Comparative Example 3 The preparation of the positive electrode specifically includes: mixing lithium iron phosphate, binder PVDF, carbon nanotubes, graphene, second positive electrode lithium supplement Li2C2O4, and solvent NMP in a mass ratio of 100:2.5:1:0.5:3:60 to prepare a positive electrode slurry. The positive electrode slurry is coated on an aluminum foil current collector and dried to form a single-side surface density of 200g / m 2 Repeat the above steps of forming the positive electrode material layer on the other side of the aluminum foil, and then roll-press to obtain the positive electrode.

[0159] According to the method described in Example 1, the positive electrode of Comparative Example 3 was assembled into a lithium battery.

[0160] Comparative Example 4

[0161] A positive electrode, which is different from Example 1 mainly in that: a positive electrode material layer without a lithium replenishing agent is provided on the aluminum foil, and a second lithium replenishing layer containing a second positive electrode lithium replenishing agent is provided on the positive electrode active material layer.

[0162] The slurry formula for forming the positive electrode material layer does not contain the second positive electrode lithium supplement, and the relative contents of other substances are the same as those in Example 1. The single surface density of the positive electrode material layer is still 200g / m 2 The slurry for forming the second lithium replenishing layer is obtained by mixing the second positive electrode lithium replenishing agent with 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 surface density of the second lithium replenishing layer is 4.6g / m 2 .

[0163] According to the method described in Example 1, the positive electrode of Comparative Example 4 was assembled into a lithium battery.

[0164] Comparative Example 5

[0165] A positive electrode, which differs from Example 1 in that: the positive electrode material layer containing the second positive electrode lithium replenishing agent in Example 1 is directly in contact with the aluminum foil, and the lithium replenishing layer in Example 1 is arranged on the side of the positive electrode material layer away from the aluminum foil.

[0166] According to the method described in Example 1, the positive electrode of Comparative Example 5 was assembled into a lithium battery.

[0167] Comparative Example 6

[0168] A positive electrode, which differs from Example 4 mainly in that: there is no lithium replenishing layer on the aluminum foil current collector, but instead a first positive electrode material sublayer and a second positive electrode material sublayer are directly stacked in sequence. In Comparative Example 6, the first positive electrode slurry formula for forming the first positive electrode material sublayer close to the current collector is lithium iron phosphate: PVDF: carbon nanotubes: graphene: Li2C2O4: NMP = 100: 2.6: 1: 0.5: 1.5: 60, and the second positive electrode slurry formula for forming the second positive electrode material sublayer 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 surface density ratio of the first positive electrode material sublayer formed by drying the first positive electrode slurry and the second positive electrode material sublayer formed by drying the second positive electrode slurry is controlled to be 1:1, and the single-surface surface density of the total positive electrode material layer is still 200 g / m 2 .

[0169] According to the method described in Example 1, the positive electrode of Comparative Example 6 was assembled into a lithium battery.

[0170] Comparative Example 7

[0171] A positive electrode is prepared, which is different from Comparative Example 1 in that the positive electrode active material is replaced by lithium iron phosphate with lithium manganese iron phosphate.

[0172] The preparation method of the positive electrode comprises: mixing lithium manganese iron phosphate, binder PVDF, carbon nanotube conductive agent, graphene conductive agent, and solvent NMP in a mass ratio of 100:2.5:1:0.5:60 to prepare a positive electrode slurry. The positive electrode slurry is coated on an aluminum foil current collector and dried to form a single-side surface density of 200g / m 2 Repeat the above steps of forming the positive electrode material layer on the other side of the aluminum foil, and then roll-press to obtain the positive electrode.

[0173] According to the method described in Example 1, the positive electrode of Comparative Example 7 was assembled into a lithium battery.

[0174] Comparative Example 8

[0175] A positive electrode, which is different from Example 7 in that: a lithium replenishing layer is provided on the aluminum foil, and a positive electrode material layer not containing a second positive electrode lithium replenishing agent is provided on the lithium replenishing layer.

[0176] The slurry formula for forming the lithium supplement layer is the same as that in Example 7, and the single-surface density of the lithium supplement layer is 4.82 g / m 2 , with a thickness of 5±1μm; the slurry forming the positive electrode material layer is a mixture of the positive electrode active material lithium iron phosphate (LFP, Dv50 is 3μm) and the binder PVDF, carbon nanotube conductive agent, graphene conductive agent, and solvent NMP in a mass ratio of 100:2.5:1:0.5:60. The single-sided surface density of the positive electrode material layer is 200g / m 2 .

[0177] In order to strongly support the beneficial effects brought about by the technical solution of the present disclosure, the lithium batteries of the above embodiments or comparative examples were subjected to the following performance tests:

[0178] a. Positive Electrode Gram Capacity Test: At room temperature (25°C), charge each battery at a constant current and constant voltage of 1 / 3C to a maximum voltage of 4.6V (C represents the battery capacity) for formation. Record the initial charge capacity (i.e., the charge capacity at formation). After aging (aging procedure: 100% SOC at 45°C for 48 hours, the same applies below), discharge at 1 / 3C to a minimum voltage of 2.0V and calculate the initial discharge capacity. Here, the positive electrode gram capacity = initial discharge capacity / mass of positive electrode active material. Initial coulombic efficiency η = initial discharge capacity / initial charge capacity.

[0179] b. Cycling Performance Test: At room temperature (25°C), charge each aged battery at a constant current and constant voltage rate of 1 / 3C to an upper voltage limit of 3.8V. Then discharge at a constant current and constant voltage rate of 1 / 3C to a lower voltage limit of 2.0V. Repeat this charge and discharge process 500 times, and record the capacity retention rate after 500 cycles. Capacity retention rate after 500 cycles = discharge capacity at the 500th cycle / discharge capacity at the first discharge after aging.

[0180] c. Battery Direct Current Internal Resistance (DCIR) Test: At room temperature (25°C), each aged battery was charged at a constant current of 1 / 3C to an upper voltage limit of 3.8V. It was then discharged at a constant current of 1 / 3C to a lower voltage limit of 2.0V. After three cycles, the battery was again charged at a constant current of 1 / 3C at 25°C to 50% SOC. The battery voltage after standing for one hour was recorded as V1. The battery was then discharged at 1.5C for 30 seconds, and the battery voltage at the end of discharge was recorded as V2. DCIR = (V1 - V2) / 1.5C.

[0181] d. Utilization rate test of lithium supplement materials:

[0182] Non-lithium-supplemented batteries corresponding to the lithium-supplemented batteries of the embodiments and comparative examples of the present disclosure were prepared: wherein, embodiments 1-20 and comparative examples 2-6 and 8 are all lithium-supplemented batteries, comparative example 1 is the non-lithium-supplemented battery corresponding to embodiments 1-19 and comparative examples 2-6, and comparative example 7 is the non-lithium-supplemented battery corresponding to embodiment 20. Each of the above batteries was charged at a constant current and constant voltage of 1 / 3C to an upper limit voltage of 4.6V for formation at room temperature (25°C), and discharged at a constant current and constant voltage of 1 / 3C to a lower limit voltage of 2.0V after aging. The discharge capacity of each lithium-supplemented battery was recorded as C1, and the discharge capacity of the corresponding non-lithium-supplemented battery was recorded as C2. The utilization rate of the lithium-supplemented material = (C1-C2) / (mass of the lithium-supplemented material × gram capacity of the lithium-supplemented material). The gram capacity of the lithium-supplemented material here is calculated based on the actual number of active lithium ions removed during lithium replenishment by various lithium-supplementing agents known in the industry.

[0183] The relevant test results are summarized in Table 1 below.

[0184] Table 1

[0185] From Examples 1 and 7 and Comparative Examples 1-2 and 4-5 in Table 1, it can be seen that when the positive electrode of the battery does not contain a lithium replenisher (Comparative Example 1), the positive electrode capacity and initial coulombic efficiency of the battery are both low, and the DCIR value is high. However, in Comparative Examples 2 and 4-5, where the positive electrode contains only one type of positive electrode lithium replenisher, or the positive electrode contains two types of positive electrode lithium replenishers but they are not distributed as in Example 1 of the present disclosure (the sum of the lithium replenishing capacity provided by the lithium replenisher in the positive electrode is close to that of Examples 1 and 7), although the positive electrode capacity and initial coulombic efficiency of the battery can be improved to a certain extent, the effect of reducing the DCIR value of the battery is not obvious, and the DCIR value impedance of the battery is still high (which can reflect the poor power performance of the battery). In Example 1 of the present disclosure, a lithium replenisher layer containing a first positive electrode lithium replenisher material is used as a bottom coating on the current collector, and a positive electrode material layer formed by distributing a second positive electrode lithium replenisher material in the positive electrode active material is provided on the bottom coating, which can increase the positive electrode capacity and reduce the battery impedance. In addition, similar phenomena can also be seen from the comparison between Comparative Example 3 and Example 3, and the comparison between Comparative Example 6 and Example 4.

[0186] In addition, from the comparison between Example 1 and Examples 9, 10, and 14, it can be seen that when the sum of the lithium replenishing capacities provided by the lithium replenishing agents in the positive electrode is close, and the composition of the lithium replenishing layer and the single-surface density of the positive electrode material layer are the same, when the ratio of the lithium replenishing capacity of the first positive electrode lithium replenishing agent to the second positive electrode lithium replenishing agent is in the range of (0.2-2):1, it is more conducive to improving the comprehensive performance of the lithium battery, especially reducing the DCIR value of the battery and improving the utilization rate of the lithium replenishing agent.

[0187] From the comparison of Examples 1, 12, and 13 with Example 11, it can be seen that when the composition, thickness, surface density, etc. 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 is different, the Dv50 of the second positive electrode lithium replenisher is in the range of 20-500nm and the Dv50 of the positive electrode active material is in the range of 0.2-5μm, which is more conducive to increasing the battery positive electrode gram capacity, thereby increasing the energy density of the positive electrode, and reducing the battery DCIR value.

[0188] Furthermore, a comparison between Example 1 and Example 7 reveals that, when other battery positive electrode parameters are the same, a conductive coating on the surface of the first positive electrode lithium replenisher is more conducive to reducing battery impedance and improving the utilization rate of the lithium replenisher material. A comparison between Example 20 and Comparative Example 7, in which the positive electrode active material is varied, also reveals similar phenomena to those observed between Example 1 and Comparative Example 1.

[0189] The above-described embodiments merely represent several implementation methods of the present disclosure. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the scope of the present disclosure, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A positive electrode (100), characterized in that: The invention comprises a positive electrode current collector (10), and a lithium replenishing layer (20) and a positive electrode material layer (30) which are sequentially stacked on at least one side of the positive electrode current collector (10), wherein the lithium replenishing layer (20) contains a first positive electrode lithium replenishing agent (201), and the positive electrode material layer (30) contains a positive electrode active material (302) and a second positive electrode lithium replenishing agent (301), wherein the first coulombic efficiency of the first positive electrode lithium replenishing agent (201) is less than 30%, and the second positive electrode lithium replenishing agent (301) can be decomposed to generate gas.

2. The positive electrode (100) according to claim 1, characterized in that The first positive electrode lithium supplement (201) includes one or more of Li6CoO4, Li2MoO3, Li5FeO4, Li6MnO4, Li2NiO2, Li2CuO2, Li3PO4, Li4SiO4, Li2SiO3, Li3VO4, Li2VO3, Li5ReO6, Li2RuO3, Li2MnO3, Li2MoO3, Li2S, and LiF.

3. The positive electrode (100) according to claim 1 or 2, characterized in that: The surface of the first positive electrode lithium supplement (201) has a conductive coating layer.

4. The positive electrode (100) according to any one of claims 1 to 3, characterized in that: The lithium replenishing layer (20) contains the following components in percentage by mass: 50%-90% of the first positive electrode lithium replenishing agent (201), 0-40% of the second positive electrode active material, 0.5-10% of a binder, and 0.5-10% of a conductive agent.

5. The positive electrode (100) according to any one of claims 1 to 4, characterized in that: The second positive electrode lithium supplement (301) includes one or more of Li2CO3, Li3N, Li2O2, Li2O, Li2C2O4, Li2C4O4, Li2C3O5, and Li2C4O6.

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

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

8. The positive electrode (100) according to any one of claims 1 to 7, characterized in that: The ratio of lithium replenishing capacity that can be provided by the first positive electrode lithium replenishing agent (201) and the second positive electrode lithium replenishing agent (301) is (0.2-2):

1.

9. The positive electrode (100) according to any one of claims 1 to 8, characterized in that: The single-surface surface density of the positive electrode material layer (30) is greater than the single-surface surface density of the lithium supplement layer (20).

10. The positive electrode (100) according to any one of claims 1 to 9, characterized in that: The single-surface density of the lithium supplement layer (20) is 0.5-50 g / m 2 .

11. The positive electrode (100) according to claim 10, characterized in that: The single-surface density of the lithium supplement layer (20) is 0.5-20 g / m 2 .

12. The positive electrode (100) according to any one of claims 1 to 11, characterized in that: The single-side thickness of the lithium supplement layer (20) is 0.1-100 μm.

13. The positive electrode (100) according to claim 12, characterized in that: The single-side thickness of the lithium supplement layer (20) is 0.5-10 μm.

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

15. The positive electrode (100) according to any one of claims 1 to 13, characterized in that: The positive electrode material layer (30) comprises n positive electrode material sublayers, where n≥2, wherein 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 layer by layer in a direction from the positive electrode current collector (10) to the positive electrode material layer (30).

16. The positive electrode (100) according to claim 14 or 15, characterized in that: Among the n layers of positive electrode material sublayers, at least two adjacent layers satisfy: A m / (D m / D m-1 )-A m-1 ≥5%; Among them, A m-1 is the mass ratio of the second positive electrode lithium replenisher (301) in the m-1th positive electrode material sublayer to the total second positive electrode lithium replenisher (301) in the positive electrode material layer (30), A m is the mass ratio of the second positive electrode lithium replenisher (301) in the mth positive electrode material sublayer to the total second positive electrode lithium replenisher (301) in the positive electrode material layer (30), D m-1 is the thickness of the m-1th positive electrode material sublayer, D m is the thickness of the mth positive electrode material sublayer, m is any integer between 2 and n; on the same side of the positive electrode current collector (10), the m-1th positive electrode material sublayer is closer to the positive electrode current collector (10) than the mth positive electrode material sublayer.

17. The positive electrode (100) according to claim 16, characterized in that: Among the n layers of positive electrode material sub-layers, any two adjacent layers of the positive electrode material sub-layers satisfy: A m / (D m / D m-1 )-A m-1 ≥5%.

18. The positive electrode (100) according to any one of claims 15 to 17, characterized in that: The mass proportion of the positive electrode active material (302) in each of the positive electrode material sub-layers is greater than 80%.

19. A lithium battery (1), characterized in that: It comprises the positive electrode (100) according to any one of claims 1 to 18.

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

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