High-specific-energy layered negative pole piece structure, electrode assembly, battery monomer, electrochemical device and electric equipment

Abstract

The utility model discloses a high-specific-energy layered negative pole piece structure, an electrode assembly, a battery monomer, an electrochemical device and electric equipment. The high-specific-energy layered negative pole piece structure sequentially comprises an active graphite layer, a lithium-loving coating, an active silicon-containing layer, a porous resin layer, a metal lithium layer and a graphene layer from at least one side of a current collector layer to the outside. Through the sequential design of the pole piece structure, the problems that the volume of a negative electrode material is seriously expanded and the negative electrode piece is easy to fall off are solved, the safety performance of the battery is improved, and the energy density and the cycle performance of a system are effectively improved.

Description

Technical Field

[0001] The utility model relates to the technical field of battery structure design, and particularly relates to a high specific energy layered negative electrode sheet structure. Background Art

[0002] With the rapid development of electric vehicles and portable electronic devices, the market demand for high energy density batteries is increasing day by day. Carbon-silicon negative electrode materials have become an important direction for promoting the development of battery technology due to their advantages such as high energy density, improved cycle stability, and Coulomb efficiency.

[0003] However, during the lithium intercalation process of silicon-based negative electrode materials, a huge volume expansion will occur, and the SEI film will repeatedly regenerate and break, resulting in the easy structural failure of silicon-carbon negative electrode materials during the cycle, thus affecting the cycle stability and life of the battery. Moreover, high specific energy silicon negative electrodes have a relatively high energy density, poor safety performance, large reactivity with lithium, and are prone to generating a large amount of heat, causing safety risks. Therefore, it is of great significance to optimize the structure design of carbon-silicon negative electrode materials to enable them to safely and effectively exert their best performance. Summary of the Utility Model

[0004] The utility model discloses a high specific energy layered negative electrode sheet structure in view of the problems in the prior art. By sequentially designing the sheet structure, the problems of serious volume expansion of the negative electrode material and easy detachment of the negative electrode sheet are solved, the safety performance of the battery is improved, and the system energy density and cycle performance are effectively increased.

[0005] The utility model is realized by the following technical solutions:

[0006] The utility model provides a high specific energy layered negative electrode sheet structure, which, from at least one side of the current collector layer outwards, sequentially includes an active graphite layer, a lithium-philic coating layer, an active silicon-containing layer, a porous resin layer, a metallic lithium layer, and a graphene layer.

[0007] In the design of the utility model, the active graphite layer and the active silicon-containing layer are separately coated, which can reduce the direct contact area between the silicon negative electrode and the current collector, lower the risk of electrode peeling caused by the significant volume expansion of the silicon negative electrode during charge and discharge, ensure the stability of electron transmission, optimize the electron transmission path, reduce the internal resistance of the battery, and thus improve the electrochemical performance and cycle stability of the battery.

[0008] The lithium-philic coating layer, as a buffer layer, placed between the graphite and silicon electrodes can absorb the volume change of the silicon electrode, change the deposition morphology of metallic lithium, is beneficial to improving the initial Coulomb efficiency of the battery, and can also reduce interfacial side reactions and enhance the cycle stability of the battery.

[0009] On the other side of the active silicon-containing layer, a porous resin layer is also provided, which can cooperate with the lithiumophilic coating as a buffer layer to absorb the volume expansion of the active silicon-containing layer and reduce the mechanical stress on the electrode structure. It can also cooperate with the lithiumophilic coating to induce further uniform upward deposition of lithium towards the bottom layer of the active graphite layer, which helps to control the deposition behavior of metallic lithium, reduce the formation of dendrites, and lower the volume expansion of the negative electrode.

[0010] In the present utility model, the metallic lithium layer and the silicon negative electrode layer are separated by a porous resin layer, which not only supplements lithium ions but also avoids direct contact with the silicon negative electrode; such a design also avoids the problem that when the silicon content is relatively high, the reactivity with lithium is large, easily generating a large amount of heat and causing safety risks.

[0011] A graphene layer is also provided outside the metallic lithium layer, which can provide a physical barrier to reduce unnecessary side reactions. In addition, the excellent electrochemical stability of the graphene layer can also prevent the active material from directly contacting the electrolyte, thereby reducing the occurrence of side reactions with the electrolyte and forming a more stable SEI film, which helps to improve the charge-discharge rate and overall Coulomb efficiency of the battery.

[0012] As a further solution, the current collector includes one of copper foil, copper composite metal foil, aluminum foil, titanium foil, and silver foil.

[0013] Further, the present utility model uses a porous copper foil, and the pore diameter of the copper foil is preferably 0.1 - 5 μm, and the porosity is preferably 20% - 50%.

[0014] Due to its high-porosity structure, the porous copper foil can increase the contact area between the active material and the electrolyte, improve the kinetic performance of the battery cell, and at the same time reserve space for the expansion of the active material and the extension of the electrode sheet, slowing down the thickness expansion caused by the volume change of the silicon-based negative electrode.

[0015] As a further solution, the active graphite layer can be selected from one of natural graphite layer, artificial graphite layer, composite graphite layer, hard carbon layer, and soft carbon layer.

[0016] As a further solution, the active silicon-containing layer can be selected from one of silicon particle layer, silicon-based alloy layer, silicon oxide layer, and silicon-carbon composite layer.

[0017] As a further solution, the lithiumophilic coating can be one of a liquid metal coating, a solid metal coating, an oxide coating, or a polymer coating; as some specific examples: the liquid metal coating includes one of a liquid metal gallium layer and a liquid metal Ga@Li layer; the solid metal coating includes one of a silver layer, a magnesium layer, a zinc layer, a cadmium layer, and a nickel layer; the oxide coating includes one of a titanium dioxide layer, a silicon dioxide layer, and an aluminum oxide layer; the polymer coating includes one of a polyvinylidene fluoride layer, a polyimide layer, and a polyacrylic acid layer.

[0018] Furthermore, the lithiumophilic coating is preferably a solid metal coating; the solid metal coating has a stronger affinity with lithium, a stable structure, can promote the uniform deposition of lithium, and has stronger conductivity, thereby improving the electrochemical performance of the battery.

[0019] As a further solution, the porous resin layer can be selected from a polystyrene porous resin layer, a polypropylene porous resin layer, a polyimide porous resin layer, or one of some synthetic resin adhesive layers; as some specific examples: the synthetic resin adhesive includes one of a urea-formaldehyde resin adhesive layer, a phenolic resin adhesive layer, and a melamine resin adhesive layer. The pore size range of the porous resin layer is preferably 5 - 50 μm, and the porosity is 65 - 85%.

[0020] As a further solution, the metallic lithium layer is one of metallic lithium, metallic lithium foil, or metallic lithium alloy foil.

[0021] As a further solution, the thickness of the active graphite layer or the active silicon-containing layer is preferably 10 - 150 μm, the thickness of the lithiumophilic coating is preferably 5 - 30 μm, the thickness of the porous resin layer is preferably 2 - 50 μm, the thickness of the metallic lithium layer is preferably 5 - 10 μm, and the thickness of the graphene layer is preferably 5 - 20 μm.

[0022] It is necessary for us to comprehensively adjust the thicknesses between the layers to enable it to exert the best performance advantages.

[0023] The present utility model also provides an electrode assembly, a battery cell, an electrochemical device, or an electrical equipment with a high specific energy layered negative electrode sheet structure.

[0024] The features and beneficial effects of the present utility model are as follows:

[0025] (1) In the present utility model, the graphite negative electrode and the silicon negative electrode are coated separately, which can avoid the damage to the battery structure caused by the volume expansion of the silicon negative electrode during the charge and discharge process of the battery, affecting its electron transfer efficiency, Coulomb efficiency, and battery cycle performance.

[0026] (2) In the present utility model, the lithiumophilic coating and the porous resin layer are coated on both sides of the silicon electrode, which can relieve the stress change caused by the volume expansion of the silicon electrode, prevent the shedding and fragmentation of the electrode material during the charge and discharge process, and can extend the cycle life of the battery. Moreover, the porous resin layer has a good ability to store metallic lithium, can effectively accommodate the metallic lithium deposited from the positive electrode to the negative electrode, and at the same time, the lithiumophilic coating can induce the metallic lithium deposited in the porous resin layer to further deposit uniformly upward towards the bottom layer of the lithium composite negative electrode, which helps to control the deposition behavior of metallic lithium, reduce the formation of dendrites, and reduce the volume expansion of the negative electrode.

[0027] (3) In the negative electrode tab of the present utility model, the optimized design of the thickness of each layer is beneficial to ensuring the overall mechanical stability of the electrode, reducing material fragmentation and peeling caused by volume changes during charge and discharge; maintaining the overall stability of the structure, and ensuring that each layer structure has a matching ability to embed and extract ions, preventing the risk of lithium plating due to uneven ion deposition, thereby improving the charge and discharge efficiency and power density of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 FIG. 1 is a schematic structural diagram of the negative electrode tab of Embodiment 1 of the present utility model.

[0030] DESCRIPTION OF THE REFERENCE NUMERALS:

[0031] 1. Current collector; 2. Active graphite layer; 3. Lithiophilic coating; 4. Active silicon-containing layer; 5. Porous resin layer; 6. Metallic lithium layer; 7. Graphene layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] It should be noted that, without conflict, the embodiments in the present utility model and the features in the embodiments can be combined with each other.

[0033] The present utility model provides a high specific energy layered negative electrode tab structure, which sequentially includes an active graphite layer, a lithiophilic coating, an active silicon-containing layer, a porous resin layer, a metallic lithium layer, and a graphene layer from at least one side of the current collector layer outward.

[0034] In the design of the present utility model, separating the active graphite layer and the active silicon-containing layer for coating can reduce the direct contact area between the silicon negative electrode and the current collector, and reduce the risk of electrode peeling caused by the significant volume expansion of the silicon negative electrode during charge and discharge. The volume change of the graphite negative electrode is relatively small. Placing the graphite negative electrode on the side close to the current collector can utilize its small volume change to maintain good contact between the electrode and the current collector, ensure the stability of electron transfer; optimize the electron transfer path, reduce the internal resistance of the battery, thereby improving the electrochemical performance and cycle stability of the battery. Moreover, since the graphite negative electrode has good thermal stability and chemical stability, while the silicon negative electrode may have safety risks under high temperature or overcharge conditions. Placing the graphite negative electrode close to the current collector can also serve as a safety barrier inside the battery to reduce safety risks.

[0035] Due to the significant volume expansion of the silicon electrode during charge and discharge processes, this may lead to the fragmentation of the electrode material and a decline in battery performance. The lithiophilic coating, as a buffer layer, placed between the graphite and silicon electrodes can absorb the volume change of the silicon electrode, reduce the impact on the graphite electrode, enhance the bonding strength between the graphite and silicon electrodes, and improve the overall structural stability of the electrode; thereby helping to reduce the shedding and fragmentation of the electrode material during charge and discharge processes and extend the cycle life of the battery. Placing the lithiophilic coating between the graphite and silicon electrodes, due to the high lithiophilicity of the lithiophilic coating, can also change the deposition morphology of metallic lithium, induce the uniform deposition of metallic lithium into the bottom layer of the active graphite layer, and the uniformly deposited metallic lithium; not only is beneficial to improving the initial Coulombic efficiency of the battery, but also can reduce interfacial side reactions and enhance the cycle stability of the battery.

[0036] On the other side of the active silicon-containing layer, there is also a porous resin layer. Since the active silicon-containing layer will undergo significant volume expansion during charge and discharge processes, the elasticity and compressibility of the porous resin layer can cooperate with the lithiophilic coating as a buffer layer to absorb this expansion and reduce the mechanical stress on the electrode structure. And the porous resin layer has good ability to transport metallic lithium. As the layer closely adjacent to the metallic lithium layer, it is beneficial to alleviate problems such as uneven deposition and lithium dendrites caused by excessive initial lithium amount brought by the metallic lithium layer, and cooperate with the lithiophilic coating to induce further uniform upward deposition of lithium into the bottom layer of the active graphite layer, which helps to control the deposition behavior of metallic lithium, reduce the formation of dendrites, and lower the volume expansion of the negative electrode.

[0037] Due to the volume change of the silicon negative electrode in the active silicon-containing layer during battery charge and discharge processes, it will lead to the consumption of lithium ion content. The arranged metallic lithium layer can supplement lithium to the high-silicon negative electrode system, make up for the first-cycle efficiency loss of the silicon negative electrode, and improve the energy density and cycle performance of the system. The present utility model separates the metallic lithium layer from the silicon negative electrode layer by a porous resin layer, which not only supplements lithium ions but also avoids direct contact with the silicon negative electrode; such a design also avoids the problem that when the silicon content is relatively high, it has a large reaction activity with lithium, is prone to generate a large amount of heat, and causes safety risks.

[0038] Due to the extremely high reaction activity of the metallic lithium layer, it is easy to react with moisture and oxygen in the air. There is also a graphene layer arranged outside the metallic lithium layer. This layer can provide a physical barrier to protect metallic lithium from the influence of the external environment, reduce unnecessary side reactions, and improve the battery capacity. In addition, the excellent electrochemical stability of the graphene layer can also prevent the active substance from directly contacting the electrolyte, thereby reducing the occurrence of side reactions with the electrolyte, forming a more stable SEI film, and further enhancing the cycle stability of the battery cell. Moreover, the graphene layer has an extremely high electron mobility. As the outermost layer of the negative electrode sheet, graphene can significantly improve the conductivity of the battery; this helps to improve the charge and discharge rate and the overall Coulombic efficiency of the battery.

[0039] As a further solution, the current collector includes one of copper foil, copper composite metal foil, aluminum foil, titanium foil, and silver foil.

[0040] Furthermore, the utility model uses a porous copper foil, the pore size of the copper foil is preferably 0.1-5 μm, and the porosity is preferably 20%-50%.

[0041] Due to its high porosity structure, porous copper foil can increase the contact area between the active material and the electrolyte, improve the dynamic performance of the battery cell, and also reserve space for the expansion of the active material and the extension of the electrode, slowing down the thickness expansion caused by the volume change of the silicon-based negative electrode.

[0042] As a further solution, the active graphite layer can be selected from one of a natural graphite layer, an artificial graphite layer, a composite graphite layer, a hard carbon layer, and a soft carbon layer.

[0043] As some specific examples, the natural graphite layer may be composed of natural graphite materials purchased from Qingdao Tianyuan Graphite Co., Ltd. and some necessary binders; the artificial graphite layer may be composed of artificial graphite material SN-P2H purchased from Snow New Materials Co., Ltd. and some necessary binders; the composite graphite layer may be composed of commercially available composite graphene material MAG-100 purchased from Snow New Materials Co., Ltd. and some necessary binders; the hard carbon layer may be composed of PHC-1 hard carbon material from Bester Co., Ltd. and some necessary binders; the soft carbon layer may be composed of PSCAM240 soft carbon material from Oplat New Materials Co., Ltd. and some necessary binders.

[0044] As a further solution, the active silicon-containing layer may be selected from one of a silicon particle layer, a silicon-based alloy layer, a silicon oxide layer, and a silicon-carbon composite material layer.

[0045] As some specific examples, the silicon particle layer may be composed of silicon particles Si13502 purchased from Zhongnuo New Materials Co., Ltd. and some necessary binders; the silicon-based alloy layer may be composed of FeSi45 ferrosilicon alloy powder purchased from Yuehan Metal Materials Co., Ltd. and some necessary binders; the silicon oxide layer may be composed of silicon oxide material YOB166 purchased from Tianmu Pioneer Battery Materials Co., Ltd. and some necessary binders; the silicon-carbon composite material layer may be composed of silicon-carbon composite material S0310 commercially available from Lanxi Zhide New Energy Materials Co., Ltd. and some necessary binders.

[0046] As a further solution, the lithiophilic coating can be one of a liquid metal coating, a solid metal coating, an oxide coating or a polymer coating; as some specific examples: the liquid metal coating includes one of a liquid metal gallium layer and a liquid metal Ga@Li layer; the solid metal coating includes one of a silver layer, a magnesium layer, a zinc layer, a cadmium layer and a nickel layer; the oxide coating includes one of a titanium dioxide layer, a silicon dioxide layer and an aluminum oxide layer; the polymer coating includes one of a polyvinylidene fluoride layer, a polyimide layer and a polyacrylic acid layer.

[0047] Furthermore, the lithiophilic coating is preferably a solid metal coating; the solid metal coating has a stronger affinity with lithium, a stable structure, can promote the uniform deposition of lithium, and has stronger conductivity, thereby improving the electrochemical performance of the battery.

[0048] As a further solution, the porous resin layer can be selected from a polystyrene porous resin layer, a polypropylene porous resin layer, a polyimide porous resin layer or some synthetic resin adhesive layers; as some specific examples: the synthetic resin adhesive layer includes one of a urea-formaldehyde resin adhesive layer, a phenolic resin adhesive layer and a melamine resin adhesive layer. The pore size range of the porous resin layer is preferably 5-50 μm, and the porosity is 65-85%.

[0049] As a further solution, the metallic lithium layer is one of metallic lithium, metallic lithium foil or metallic lithium alloy foil.

[0050] As a further solution, the thickness of the active graphite layer or the active silicon-containing layer is preferably 10-150 μm, the thickness of the lithiophilic coating is preferably 5-30 μm, the thickness of the porous resin layer is preferably 2-50 μm, the thickness of the metallic lithium layer is preferably 5-10 μm, and the thickness of the graphene layer is preferably 5-20 μm.

[0051] When the thicknesses of the active silicon-containing layer and the active graphite layer are too small, the capacity and energy density of the battery will be affected. When the thicknesses are too large, the internal resistance of the battery is likely to increase, and the conductivity and transmission efficiency will become low. If the thickness of its lithium-philic coating is too thin, it cannot relieve the volume expansion of the active silicon-containing layer, resulting in the coating cracking or peeling off, and it will also affect the uniform deposition of lithium ions to the bottom of the active graphite layer; while if it is too thick, it will increase the internal resistance of the battery; all of these will lead to a decrease in the Coulombic efficiency and cycle efficiency of the battery. When the thickness of the porous resin layer is too thick, it will lead to an increase in unnecessary battery internal resistance and cost, thereby reducing the Coulombic efficiency, and it will also prevent the uniform penetration of the electrolyte, resulting in insufficient electrolyte supply in some areas of the active silicon-containing layer and the active graphite layer; while when the thickness is too small, it will affect its function of transporting lithium ions, which may lead to uneven deposition of lithium ions transported to the active material layer, and at the same time, it may also damage the porous structure of the active material layer itself, and cannot play a buffering role in the volume expansion of the active silicon-containing layer, reducing the charge-discharge performance and cycle efficiency of the battery. If the thickness of the metallic lithium layer is too small, it will be difficult to achieve a better lithium supplement effect. If the thickness is too large, there will be a risk of lithium precipitation, and it will also cause the electrode sheet structure to be thicker and the mechanical properties to deteriorate, resulting in a decrease in the battery capacity and cycle performance. At the same time, as the outermost layer of the negative electrode sheet, if the thickness of the graphene layer is too low, it will not be able to provide sufficient protection, resulting in an increase in side reactions between the active material layer and the electrolyte, reducing the electrochemical stability and cycle efficiency of the battery; while if the graphene layer is too thick, it will also affect the deposition and stripping efficiency of lithium ions on the metallic lithium layer, thereby affecting the contact between lithium ions and the active material layer and reducing its utilization rate. Therefore, it is necessary for us to comprehensively adjust the thicknesses of each layer to make it play the best performance advantages.

[0052] The present invention also provides an electrode assembly, a battery cell, an electrochemical device or an electrical equipment with a high specific energy layered negative electrode sheet structure.

[0053] The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0054] An exemplary structure of the high specific energy and high safety negative electrode sheet structure provided by the present invention can be as Figure 1 shown. From both sides of the current collector 1 outwards in sequence, it includes an active graphite layer 2, a lithium-philic coating 3, an active silicon-containing layer 4, a porous resin layer 5, a metallic lithium layer 6, and a graphene layer 7.

[0055] As a specific example for the implementation of the present invention, the following detailed cases are provided:

[0056] Example 1

[0057] On both sides of the current collector 1, outward in sequence, there are an active graphite layer 2, a lithium-philic coating layer 3, an active silicon-containing layer 4, a porous resin layer 5, a metallic lithium layer 6, and a graphene layer 7. Among them, the current collector 1 uses a porous copper foil with a pore size of 5 μm and a porosity of 45%; the active graphite layer 2 uses an artificial graphite negative electrode with a thickness of 45 μm; the active silicon-containing layer 4 uses a silicon oxide negative electrode with a thickness of 45 μm; the lithium-philic coating layer is a metallic zinc coating material with a specific thickness of 10 μm; the porous resin layer is specifically the urea-formaldehyde resin purchased from Shenyang Yilaipukes Chemical Co., Ltd., with a purity of 99%, a thickness of 40 μm, and a particle size range of 10 μm; the metallic lithium layer is specifically a lithium foil layer with a thickness of 5 μm, and the lithium foil is from Tianjin Zhongneng Lithium Industry Co., Ltd. commercially available; the graphene layer is specifically a graphene layer with a purity of 97% purchased from Shanghai Macklin Biochemical Co., Ltd., with a thickness of 10 μm. It is obtained by coating these layers on the current collector in sequence. As Figure 1 shown.

[0058] Example 2

[0059] The difference from Example 1 is that: the active graphite layer 2 uses a composite graphite negative electrode, specifically the composite graphene material MAG-100 commercially available from Snow New Materials Co., Ltd., with a thickness of 35 μm; the others are the same.

[0060] Example 3

[0061] The difference from Example 1 is that: the active silicon-containing layer 4 uses a carbon-silicon composite material negative electrode, specifically the silicon-carbon composite material S0310 commercially available from Lanxi Zhide New Energy Materials Co., Ltd., with a thickness of 35 μm; the others are the same.

[0062] Example 4

[0063] The difference from Example 1 is that: the current collector 1 uses a 5-μm porous aluminum foil with a pore size of 5 μm and a porosity of 40%. The others are the same.

[0064] Example 5

[0065] The difference from Example 1 is that: on the outside of the active silicon-containing layer 4, there is a phenolic resin adhesive with a thickness of 40 μm and a particle size range of 15 μm. The phenolic resin adhesive is purchased from Shanghai Macklin Biochemical Co., Ltd., and the others are the same.

[0066] Example 6

[0067] The difference from Example 1 is that: on the outside of the porous resin layer 5, there is a 5-μm metallic lithium alloy foil layer, and the metallic lithium alloy foil layer is purchased from Guangdong Daxiao Chemical Co., Ltd., and the others are the same.

[0068] Comparative Example 1

[0069] The difference from Example 1 is that the lithiumophilic coating 3 is not provided, and the others are the same.

[0070] Comparative Example 2

[0071] The difference from Example 1 is that the graphene layer 7 is not provided, and the others are the same.

[0072] Comparative Example 3

[0073] The difference from Example 1 is that the porous resin layer 5 is not provided, and the others are the same.

[0074] Comparative Example 4

[0075] The difference from Example 1 is that the metallic lithium layer 6 is not provided, and the others are the same.

[0076] Comparative Example 5

[0077] The difference from Example 1 is that the positions of the active silicon-containing layer 4 and the active graphite layer 2 are swapped, that is, the active silicon-containing layer 4 is closer to the current collector layer side, and the others are the same.

[0078] Comparative Example 6

[0079] The difference from Example 1 is that the active silicon-containing layer 4 and the active graphite layer 2 are mixed evenly in a ratio of 1:1 and coated closer to the current collector layer side, followed by the lithiumophilic coating 3, the porous resin layer 5, the metallic lithium layer 6, and the graphene layer 7. The others are the same.

[0080] After the above-prepared electrode sheets are thoroughly dried and assembled into button cells, the assembled button cells are subjected to electrical performance tests, and the test results are shown in Table 1.

[0081] Test process:

[0082] (1) Discharge at 0.1C to 0.005V;

[0083] (2) Charge at 0.1C to 2V.

[0084] Cycle 100 times according to the above steps.

[0085] Among them, the negative electrode swelling rate = (the thickness of the negative electrode sheet after cycling - the thickness of the negative electrode sheet before cycling) / the thickness of the negative electrode sheet before cycling * 100%

[0086] Table 1 Electrode sheet layer settings and performance tests of the embodiments and comparative examples of the present invention

[0087]

[0088] According to the severity of lithium deposition, the lithium deposition situation is divided into 10 levels. The higher the value, the more severe the lithium deposition. The discrimination criteria for the lithium deposition situation of the 10 levels are shown in Table 2:

[0089] Table 2

[0090] Level Lithium plating condition 0 No lithium plating; 1 Dot-like lithium plating, with the lithium coverage rate on the negative electrode surface between 0% and 3%; 2 Very slight lithium plating, with the lithium coverage rate on the negative electrode surface between 3% and 5%; 3 Slight lithium plating, with the lithium coverage rate on the negative electrode surface between 5% and 15%; 4 Lithium plating appears in a very small part, with the lithium coverage rate on the negative electrode surface between 15% and 30%; 5 Lithium plating appears in a small part, with the lithium coverage rate on the negative electrode surface between 30% and 45%; 6 Lithium plating appears in part, with the lithium coverage rate on the negative electrode surface between 45% and 60%; 7 Lithium plating appears in the vast majority, with the lithium coverage rate on the negative electrode surface between 60% and 75%; 8 Lithium plating appears on almost the entire surface, with the lithium coverage rate on the negative electrode surface between 75% and 90%; 9 Lithium plating appears on the entire surface, with the lithium coverage rate on the negative electrode surface ≥90%;

[0091] As can be seen from Table 1, in Examples 1-6 and Comparative Examples 1-6, it can be seen that in the present utility model, the active graphite layer and the active silicon-containing layer are separately coated, and are arranged as an active graphite layer, a lithium-philic coating, an active silicon-containing layer, a porous resin layer, a metallic lithium layer, and a graphene layer from at least one side of the current collector layer outward, having better battery capacity and cycling performance. The high specific energy layered anode electrode sheet structure set in the present utility model shows excellent electrochemical performance for electrode sheets of different material systems, has a high battery capacity and cycling performance, and improves the first-cycle Coulombic efficiency.

[0092] It can be found from Example 1 and Comparative Example 1 that the battery specific capacity obtained by the high specific energy layered electrode sheet structure set in Example 1 of the present utility model is 582.69 mAh / g higher, and when the battery of the layered electrode sheet is cycled 100 times at 0.1C, the capacity retention rate > 93%, and the battery Coulombic efficiency is relatively high; while in Comparative Example 1, the lithium-philic coating is not provided, and it can be seen that the lithium deposition level is relatively high, the anode expansion rate is relatively high, and when the battery is cycled 100 times at 0.1C, the capacity retention rate is only 84%. It shows that the setting of the lithium-philic coating buffers the volume expansion of the active silicon-containing layer and induces uniform deposition of lithium ions; it is beneficial to improve the electrochemical performance.

[0093] It can be found from Example 1 and Comparative Example 2 that when the setting of the graphene layer is cancelled, the anode expansion rate and the lithium deposition level are relatively high, and the battery specific capacity and cycling performance are relatively low, indicating that the graphene layer set on the outermost layer of the anode electrode sheet plays a role in protecting the active material layer, further improving the battery capacity and Coulombic efficiency.

[0094] It can be found from Example 1 and Comparative Example 3 that setting the porous resin layer on one side of the active silicon-containing layer can effectively buffer the volume expansion brought by the silicon anode and can better transport lithium ions to promote the uniform deposition of lithium ions at the bottom of the active graphite layer.

[0095] It can be found from Example 1 and Comparative Example 4 that the specific capacity of Comparative Example 4 is only 560.88 mAh / g, and when it is cycled 100 times at 0.1C, the capacity retention rate is only 83%; it shows that the lithium supplementing effect of the metallic lithium layer can further improve the battery capacity and cycling performance.

[0096] It should be noted that the above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A high specific energy layered anode sheet structure, characterized in that, Outward from at least one side of the current collector, it sequentially includes an active graphite layer, a lithium-philic coating layer, an active silicon-containing layer, a porous resin layer, a metallic lithium layer, and a graphene layer.

2. The structure of a high specific energy layered negative electrode sheet according to claim 1, characterized in that, The current collector includes one of copper foil, copper composite metal foil, aluminum foil, titanium foil, and silver foil; The current collector uses a porous copper foil, and the pore diameter of the copper foil is 0.1 - 5 μm, and the porosity is 20% - 50%.

3. The high specific energy layered anode electrode structure according to claim 1, characterized in that, The active graphite layer includes one of natural graphite layer, artificial graphite layer, composite graphite layer, hard carbon layer, and soft carbon layer.

4. The high specific energy layered negative electrode sheet structure according to claim 1, characterized in that, The active silicon-containing layer includes one of silicon particle layer, silicon-based alloy layer, silicon oxide layer, and silicon-carbon composite material layer.

5. The high specific energy layered anode sheet structure according to claim 1, characterized in that, The lithium-philic coating layer includes one or more of liquid metal coating layer, solid metal coating layer, oxide coating layer, or polymer coating layer; The lithium-philic coating layer is a solid metal coating layer.

6. The structure of a high specific energy layered negative electrode sheet according to claim 1, wherein The porous resin layer includes one of polystyrene porous resin layer, polypropylene porous resin layer, polyimide porous resin layer, or some synthetic resin adhesive layers; the pore diameter range of the porous resin layer is 5 - 50 μm.

7. A high specific energy layered anode electrode sheet structure according to claim 1, characterized in that, The metallic lithium layer includes one of metallic lithium, metallic lithium foil, or metallic lithium alloy foil.

8. The high specific energy layered anode sheet structure according to claim 1, characterized in that The thickness of the active graphite layer or the active silicon-containing layer is 10 - 150 μm, the thickness of the lithium-philic coating layer is 5 - 30 μm, the thickness of the porous resin layer is 2 - 50 μm, the thickness of the metallic lithium layer is 5 - 10 μm, and the thickness of the graphene layer is 5 - 20 μm.

9. An electrode assembly, characterized in that, It has the high specific energy layered negative electrode sheet structure described in any one of claims 1 - 8.

10. An electrode monomer, characterized in that, It has the high specific energy layered negative electrode sheet structure described in any one of claims 1 - 8.

11. An electrochemical device, characterized in that, It has the high specific energy layered negative electrode sheet structure described in any one of claims 1 - 8.

12. An electrical device, characterized in that, It has the high specific energy layered negative electrode sheet structure described in any one of claims 1 - 8.

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