A negative electrode current collector, a negative electrode sheet, and a battery including the negative electrode sheet

Abstract

The present application belongs to the technical field of batteries, and particularly relates to a negative electrode current collector, a negative electrode sheet and a battery comprising the negative electrode sheet. The present application effectively improves the porosity of the active material layer by designing a special coating with a functional additive and / or a porous structure on the current collector substrate, and can greatly improve the area density of the negative electrode sheet, while taking into account the charging capacity under a large area density; under the existing material system, both the active material layer and the current collector substrate have better adhesion, and the charging capacity of the negative electrode sheet under a high area density condition can be improved, and the negative electrode sheet with high porosity can also store a large amount of electrolyte, which well balances the energy density and the charging capacity, and can greatly improve the cycle life of the battery cell.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a negative electrode current collector, a negative electrode sheet and a battery comprising the negative electrode sheet. BACKGROUND

[0002] With the advent of the 5G era, the status of polymer lithium ion batteries is becoming increasingly important, and people's demand for the endurance of new electronic devices is gradually increasing, which requires lithium ion battery manufacturers to continuously and unreservedly improve the energy density of lithium ion batteries. Today, the development of various materials is increasingly close to the limit, and the development cost is also increasingly high. For lithium battery enterprises, further increasing the area density of the electrode sheet is a very effective way to improve the energy density, and the dependence on material technology is also the lowest. It is a general way that can be applied to various product systems. However, increasing the area density of the electrode sheet (the area density of the negative electrode sheet of the mass-produced battery on the market is generally 3.0-9.0 mg / cm 2 ), which will inevitably be accompanied by a loss of kinetics, resulting in lithium precipitation during the cycling process of the battery, and thus causing the performance of the battery to deteriorate. Therefore, the new generation of polymer lithium ion batteries must be technically innovative for the chemical system, so as to achieve the goal of balancing high energy density and fast charging capability. SUMMARY

[0003] In order to solve the problem that the energy density and fast charging capability of the chemical system of the polymer lithium ion battery at the present stage cannot be balanced, the application provides a negative electrode current collector, a negative electrode sheet and a battery comprising the negative electrode sheet. The use of the negative electrode current collector can improve the porosity of the functional layer and the active material layer in the negative electrode sheet, so that the obtained battery can support a capacity retention rate of 90% or more at 25℃, 1.2C rate for 800 cycles, which can effectively improve the charging capability of the negative electrode sheet, and thus achieve the goal of balancing high energy density and fast charging capability.

[0004] The purpose of the application is achieved by the following technical solutions:

[0005] A negative electrode current collector, comprising a current collector substrate and a functional layer; the functional layer is arranged on at least one side surface of the current collector substrate; and the functional layer has a porous structure.

[0006] A negative electrode current collector, comprising a current collector substrate and a functional coating layer; the functional coating layer is arranged on at least one side surface of the current collector substrate; and the functional coating layer comprises a functional additive, a dispersing agent, a conductive agent and a binder, and the functional additive comprises at least one of ammonium carbonate, ammonium bicarbonate, azodicarbonamide, benzoic acid, oxalic acid and p-toluene sulfonyl hydrazide.

[0007] A negative electrode sheet, comprising the above-mentioned negative electrode current collector.

[0008] A battery including the negative electrode sheet described above.

[0009] Advantages of the present application:

[0010] The present application provides a negative electrode current collector, a negative electrode sheet and a battery including the negative electrode sheet. The present application designs a special coating layer with functional additives (functional coating layer) and / or sets a coating layer with a porous structure (functional layer) on the current collector substrate, and after rolling, the coating layer containing functional additives is heated and volatilized to generate gas in the baking environment for removing the moisture of the electrode sheet, so as to obtain a current collector coating layer with a porous structure, effectively improve the porosity of the active material layer, and greatly improve the area density of the negative electrode sheet, while taking into account the charging capacity under high area density; under the existing material system, the active material layer and the current collector substrate have better adhesion, and the negative electrode sheet can effectively improve the charging capacity of the battery under high area density, and the negative electrode sheet with high porosity can also store a large amount of electrolyte, which well balances the energy density and the charging capacity, and greatly improves the cycle life of the battery cell. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 Structure diagram of the negative electrode current collector coated with the functional layer;

[0012] Figure 2 Cycle performance diagram of the battery cell made of the ordinary current collector of Comparative Example 1 and the functional current collector of Example 2 at 25℃;

[0013] Figure 3 Cycle performance diagram of the battery cell made of the ordinary current collector of Comparative Example 1 and the functional current collector of Example 2 at 45℃. DETAILED DESCRIPTION

[0014] <NEGATIVE ELECTRODE CURRENT COLLECTOR>

[0015] As described above, the present application provides a negative electrode current collector, which includes a current collector substrate and a functional layer; the functional layer is arranged on at least one side surface of the current collector substrate; and the functional layer has a porous structure.

[0016] According to the embodiment of the present application, the porosity of the functional layer is 1-15%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%.

[0017] According to the embodiment of the present application, the functional layer with the porous structure can effectively improve the porosity of the negative electrode sheet, and can greatly improve the area density of the negative electrode sheet, while ensuring the charging capacity under the large area density; under the existing material system, the active material layer and the current collector substrate can have better adhesion, and the negative electrode sheet can effectively improve the charging capacity of the battery under the high area density, and the negative electrode sheet with high porosity can also store a large amount of electrolyte, which can well balance the energy density and the charging capacity, and can greatly improve the cycle life of the battery.

[0018] According to the embodiment of the present application, the functional layer comprises a dispersant, a conductive agent and a binder.

[0019] According to the embodiment of the present application, the functional layer comprises the following components by mass:

[0020] The conductive agent is 1-10 parts by mass;

[0021] The dispersant is 1-10 parts by mass;

[0022] The binder is 5-15 parts by mass.

[0023] According to the embodiment of the present application, the functional layer is formed after the functional coating layer is thermally decomposed, the functional coating layer comprises a functional additive, a dispersant, a conductive agent and a binder, and the functional additive is selected from at least one of ammonium carbonate, ammonium bicarbonate, azodicarbonamide, benzoic acid, oxalic acid and p-toluene sulfonyl hydrazide.

[0024] According to the embodiment of the present application, the functional coating layer comprises the following components by mass:

[0025] The functional additive is 2-9 parts by mass;

[0026] The conductive agent is 1-10 parts by mass;

[0027] The dispersant is 1-10 parts by mass;

[0028] The binder is 5-15 parts by mass.

[0029] According to the embodiment of the present application, the functional coating layer satisfies: 1≤m 功能添加剂 / m 导电剂 ≤3;

[0030] wherein, m 功能添加剂 is the mass of the functional additive in the functional coating layer; and m 导电剂 is the mass of the conductive agent in the functional coating layer.

[0031] According to the embodiment of the present application, preferably, 1.5≤m 功能添加剂 / m 导电剂≤2.5. The mass of the functional additive affects the porosity of the negative electrode sheet. The pores left after the thermal decomposition of the functional additive make the distance between the particles in the negative electrode sheet larger, which affects the conductive network in the negative electrode sheet. In some embodiments, when the functional coating layer satisfies: 1≤m 功能添加剂 / m 导电剂 ≤3, by adjusting the mass of the functional additive and the conductive agent, a sufficient conductive network can be obtained inside the negative electrode sheet, while avoiding a significant reduction in the energy density of the battery.

[0032] The application also provides a negative electrode current collector, which comprises a current collector substrate and a functional coating layer; the functional coating layer is arranged on at least one side surface of the current collector substrate; the functional coating layer comprises a functional additive, a dispersant, a conductive agent and a binder, and the functional additive comprises at least one of ammonium carbonate, ammonium bicarbonate, azodicarbonamide, benzoic acid, oxalic acid and p-toluene sulfonyl hydrazide.

[0033] According to the embodiments of the application, by introducing the functional additive into the negative electrode current collector, and using the porous structure formed after the volatilization of the functional additive, the porosity of the active material layer can be effectively improved, and the areal density of the negative electrode sheet can be greatly improved, while the charging capacity under a large areal density is taken into account; under the existing material system, both the active material layer and the current collector substrate have better adhesion, and the negative electrode sheet can effectively improve the charging capacity of the battery under a high areal density, while the negative electrode sheet with high porosity can also store a large amount of electrolyte, which well balances the energy density and the charging capacity, and greatly improves the cycle life of the battery cell.

[0034] According to the embodiments of the application, the functional coating layer comprises the following components in mass parts:

[0035] functional additive 2-9 mass parts;

[0036] conductive agent 1-10 mass parts;

[0037] dispersant 1-10 mass parts;

[0038] binder 5-15 mass parts.

[0039] According to the embodiments of the application, the functional coating layer satisfies: 1≤m 功能添加剂 / m 导电剂 ≤3;

[0040] wherein m 功能添加剂 is the mass of the functional additive in the functional coating layer; and m 导电剂 is the mass of the conductive agent in the functional coating layer.

[0041] According to the embodiments of the application, preferably, 1.5≤m 功能添加剂 / m导电剂 ≤2.5. The mass of the functional additive affects the porosity of the negative electrode sheet. The pores left after the thermal decomposition of the functional additive make the distance between the particles in the negative electrode sheet larger, which affects the conductive network in the negative electrode sheet. In some embodiments, when the functional coating layer satisfies: 1≤m 功能添加剂 / m 导电剂 ≤3, by adjusting the mass of the functional additive and the conductive agent, a sufficient conductive network can be obtained inside the negative electrode sheet, while avoiding a significant reduction in the energy density of the battery.

[0042] According to an embodiment of the present application, the functional coating layer is prepared by the following method:

[0043] The functional additive, the conductive agent, the dispersant, the binder and water are mixed to obtain a mixed slurry; the mixed slurry is coated on the surface of the current collector substrate, rolled, and baked to prepare the negative electrode current collector.

[0044] According to an embodiment of the present application, the baking is baking at a low temperature, such as baking at a temperature lower than the decomposition temperature of the functional additive (such as a temperature less than or equal to 60°C), to ensure that the functional additive in the functional coating layer is not thermally decomposed to produce gas during the baking process, i.e., the functional additive remains in the functional coating layer. After the negative electrode current collector with the functional additive is coated with an active material layer and then subjected to baking treatment (at this time, the baking temperature is higher than the decomposition temperature of the functional additive), the gas volatilized by the thermal decomposition of the functional additive can increase the porosity of the active material layer.

[0045] <NEGATIVE ELECTRODE SHEET>

[0046] As described above, the present application also provides a negative electrode sheet, which comprises the above-mentioned negative electrode current collector.

[0047] According to an embodiment of the present application, the negative electrode sheet further comprises an active material layer; the active material layer is arranged on at least one side surface of the negative electrode current collector.

[0048] According to an embodiment of the present application, the negative electrode sheet satisfies:

[0049] 0.5≤H×W / C≤3.5;

[0050] H: the proportion of the mass of the functional additive in the functional coating layer to the total mass of the functional coating layer;

[0051] W: the proportion of the mass of the conductive agent in the functional coating layer to the total mass of the functional coating layer;

[0052] C: the area density of the negative electrode sheet, in g / cm 2 .

[0053] According to an embodiment of the present application, the negative electrode sheet satisfies:

[0054] 4.5≤P×Q / C≤6.5;

[0055] P: porosity of the negative electrode sheet;

[0056] Q: ratio of mass of the conductive agent in the functional layer to total mass of the functional layer;

[0057] C: areal density of the negative electrode sheet, in g / cm 2 .

[0058] According to an embodiment of the present application, H×W / C is 1.0, 1.5, 2.0, 2.5, 3; P×Q / C is 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4 or 6.5; when the negative electrode sheet satisfies 0.5≤H×W / C≤3.5 or 4.5≤P×Q / C≤6.5, the charging capacity of the negative electrode sheet and the energy density of the battery can be coordinated, and the charging capacity and the energy density of the battery cell can be ensured. When the formula is not satisfied, in some embodiments, the smaller the mass ratio of the functional additive, the smaller the porosity of the functional layer obtained, the smaller the porosity of the negative electrode sheet, and the smaller the charging capacity of the entire electrode sheet; in some embodiments, the larger the mass ratio of the functional additive, the larger the porosity of the functional layer obtained, the larger the porosity of the negative electrode sheet, and the energy density of the battery cell will decrease, i.e. the charging capacity and the energy density cannot be balanced.

[0059] According to an embodiment of the present application, the ratio H of mass of the functional additive in the functional coating layer to total mass of the functional coating layer is 2% to 30%, for example 2%, 3%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28% or 30%; the amount of the functional additive in such a functional layer can obtain a functional layer with sufficient porosity, which can greatly improve the areal density of the negative electrode sheet while balancing the charging capacity under large areal density.

[0060] According to an embodiment of the present application, the areal density C of the negative electrode sheet is 11 to 16 mg / cm 2 , for example 11, 12, 13, 14, 15 or 16 mg / cm 2 ; the negative electrode sheet with such an areal density can effectively improve the energy density of the battery, and also ensure that the negative electrode sheet does not lithiumize, specifically, the negative electrode sheet can support 1C charging without lithiumization, meeting the requirement of long cycle life.

[0061] According to an embodiment of the present application, the proportion W of the mass of the conductive agent in the functional coating layer to the total mass of the functional coating layer is 10-20wt%, for example 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%; the amount of the conductive agent in such a functional coating layer can ensure that sufficient conductive network is obtained inside the negative electrode sheet, while also avoiding a significant reduction in the energy density of the battery, effectively solving the problem that the pores left after volatilization of the functional additive make the distance between the particles in the negative electrode sheet too large, so that sufficient conductive network cannot be ensured inside the negative electrode sheet, resulting in a reduction in the charging capacity of the battery.

[0062] According to an embodiment of the present application, the functional layer can be formed after thermal decomposition of a functional coating layer, the functional coating layer comprising a functional additive, a dispersing agent, a conductive agent and a binder, the functional additive being selected from at least one of ammonium carbonate, ammonium bicarbonate, azodicarbonamide, benzoic acid, oxalic acid and p-toluene sulfonyl hydrazide.

[0063] According to an embodiment of the present application, the temperature of the thermal decomposition is higher than the temperature at which the functional additive is decomposed when heated, for example the temperature of the thermal decomposition is 100-120℃.

[0064] According to an embodiment of the present application, the porosity P of the negative electrode sheet is 20% or more, preferably 25-35%. With such a porosity, the charging and discharging capacity of the battery can be significantly improved, the kinetic performance of the battery is improved, and a battery with fast charging capacity is obtained.

[0065] According to an embodiment of the present application, the proportion Q of the mass of the conductive agent in the functional layer to the total mass of the functional layer is 10-30wt%, for example 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt% or 30wt%; the amount of the conductive agent in such a functional layer can ensure that sufficient conductive network is obtained inside the negative electrode sheet, while also avoiding a significant reduction in the energy density of the battery, effectively solving the problem that the pores left after volatilization of the functional additive make the distance between the particles in the negative electrode sheet too large, so that sufficient conductive network cannot be ensured inside the negative electrode sheet, resulting in a reduction in the charging capacity of the battery.

[0066] According to an embodiment of the present application, the functional layer has a porous structure formed by the gas generated by thermal decomposition of the functional additive in the slurry used to prepare the functional layer.

[0067] According to the embodiment of the present application, the active material layer has a porous structure, and the functional additive in the slurry for preparing the functional layer is volatilized along the thickness direction of the electrode sheet by the gas generated by the thermal decomposition, so that the porosity of the active material layer can be increased.

[0068] According to the embodiment of the present application, the active material layer comprises an active material, a dispersant, a conductive agent and a binder.

[0069] According to the embodiment of the present application, the mass percentage of each component in the active material layer is:

[0070] 85-98.5wt% of the active material, 0.5-5wt% of the conductive agent, 0.5-5wt% of the binder, and 0.5-5wt% of the dispersant.

[0071] According to the embodiment of the present application, the active material is selected from at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, soft carbon, lithium titanate, carbon nanofiber, and silicon-based material, wherein the silicon-based material comprises at least one of silicon oxide, silicon carbon, silicon, and silicon alloy.

[0072] According to the embodiment of the present application, the conductive agent is selected from one or more of conductive carbon black, acetylene black, ketjen black, carbon fiber, graphene, single-walled carbon nanotube, and multi-walled carbon nanotube.

[0073] According to the embodiment of the present application, the dispersant is selected from one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose.

[0074] According to the embodiment of the present application, the binder is selected from one or more of polyethylene, polyvinyl alcohol, polyvinyl chloride, polyvinyl fluoride, polyvinyl pyrrolidone, polytetrafluoroethylene, polypropylene, styrene butadiene rubber, epoxy resin, butadiene-based rubber binder, and acrylonitrile-based binder.

[0075] According to the embodiment of the present application, the current collector substrate is selected from one or more of copper foil, carbon-coated copper foil, and punched copper foil.

[0076] According to the embodiment of the present application, the peeling force between the active material layer and the negative electrode current collector (the current collector substrate with the functional layer) can be increased by more than 1.5 times compared with that of a common negative electrode sheet, wherein the common negative electrode sheet refers to the negative electrode sheet without the functional layer, i.e., the peeling force between the active material layer and the current collector substrate.

[0077] According to the embodiment of the present application, the peeling force between the active material layer and the negative electrode current collector (the current collector substrate with the functional layer) is more than 10N / m. The active material and the current collector are effectively connected, the stability of the electrode sheet is improved, and the energy density of the battery is also increased.

[0078] The application also provides a preparation method of the negative electrode sheet, comprising the following steps:

[0079] mixing the active material, the conductive agent, the binder and water to obtain an active material layer slurry;

[0080] coating the active material layer slurry on the surface of the negative electrode current collector, rolling, and baking to obtain the negative electrode sheet;

[0081] Alternatively, the negative electrode sheet is prepared by the following method:

[0082] mixing the functional additive, the conductive agent, the dispersant, the binder and water to obtain a mixed slurry; and mixing the active material, the conductive agent, the binder and water to obtain an active material layer slurry;

[0083] coating the mixed slurry and the active material layer slurry on the surface of the current collector substrate in sequence, rolling, and baking to obtain the negative electrode sheet.

[0084] According to the embodiment of the application, the baking temperature is higher than the thermal decomposition temperature of the functional additive, and the functional additive in the mixed slurry is thermally decomposed to generate gas during the baking process, and the generated gas volatilizes along the thickness direction of the electrode sheet, so that the porosity of the active material layer can be increased, and the fast charging capacity of the system can be greatly improved while ensuring a high surface density of the electrode sheet. Meanwhile, the negative electrode sheet also has good adhesion, which effectively prevents the separation of the active material layer and the current collector substrate.

[0085] According to the embodiment of the application, the mixed slurry comprises the following components by mass:

[0086] the functional additive 2-9 parts by mass;

[0087] the conductive agent 1-10 parts by mass;

[0088] the dispersant 1-10 parts by mass;

[0089] the binder 5-15 parts by mass;

[0090] water 56-91 parts by mass.

[0091] <Battery>

[0092] The application also provides a battery comprising the above negative electrode sheet.

[0093] According to the embodiment of the application, the energy density of the battery is 810 Wh / L or more.

[0094] According to the embodiment of the application, the battery is a lithium ion battery.

[0095] According to an embodiment of the present application, the battery further comprises a cathode sheet.

[0096] According to an embodiment of the present application, the cathode sheet comprises a cathode current collector and a cathode active material layer coated on at least one surface of the cathode current collector, the cathode active material layer comprising a cathode material.

[0097] In some embodiments, the cathode current collector is selected from one or more of an aluminum foil, a carbon-coated aluminum foil, and a punched aluminum foil.

[0098] In some embodiments, the cathode material is selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, lithium iron silicate, lithium cobaltate, a nickel-cobalt-manganese ternary material, a nickel-manganese / cobalt-manganese / nickel-cobalt binary material, lithium manganate, and a lithium-rich manganese-based material.

[0099] The application will be further described in conjunction with the specific examples. It should be understood that the following examples are only illustrative and explanatory of the application and should not be construed as limiting the scope of protection of the application. Any technology realized based on the above description of the application is encompassed within the scope of the application intended to be protected.

[0100] The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples are commercially available unless otherwise specified.

[0101] Preparation Example

[0102] (1) Preparation of a cathode sheet

[0103] A cathode active material 4.25V lithium cobaltate (LCO), a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black were mixed in a weight ratio of 97:1.5:1.5, N-methyl pyrrolidone (NMP) was added, and stirring was performed under the action of a vacuum stirrer until the mixed system became a uniform flowable cathode slurry; the cathode slurry was uniformly coated on an aluminum foil having a thickness of 12 μm; the coated aluminum foil was baked in an oven with 5 different temperature gradients, then dried in an oven at 120°C for 8 h, and then subjected to rolling and slitting to obtain the desired cathode sheet.

[0104] (2) Preparation of an active material slurry

[0105] A negative electrode active material graphite, a dispersant sodium carboxymethyl cellulose (CMC-Na), a binder styrene-butadiene rubber, and a conductive agent carbon black were mixed in a weight ratio of 96.5:1.5:1.5:0.5, deionized water was added, and a negative electrode slurry was obtained under the action of a vacuum stirrer, having a solid content of 40% to 49% and a viscosity of 2000 to 6000 mPa.s.

[0106] (3) Preparation of an electrolyte

[0107] In the glove box filled with argon (moisture <10 ppm, oxygen <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP) were mixed uniformly in a mass ratio of 1.5:1:2, 13wt.% LiPF6 based on the total mass of the non-aqueous electrolyte was slowly added to the mixed solution, stirred uniformly, and after passing the moisture and free acid detection, the required electrolyte was obtained.

[0108] (4) Preparation of the separator film

[0109] Asahi Kasei 5+2+2 oil-based separator was selected.

[0110] (5) Preparation of the lithium ion battery

[0111] The prepared positive electrode sheet, separator, and negative electrode sheet were stacked in order, and the separator was ensured to be between the positive and negative electrode sheets to play a role of isolation, and then an un-liquid-injected bare cell was obtained by winding. The bare cell was placed in an outer packaging foil, the prepared electrolyte was injected into the dried bare cell, then formation was carried out, and two-sealing was carried out to ensure that the residual liquid amount coefficient was above 1.3, and finally the soft package polymer lithium ion battery was completed after sorting and testing.

[0112] (6) 45℃ cycle test

[0113] The battery was placed in a (45±3)℃ environment for 3 hours, and when the cell body reached (45±3)℃, the battery was charged to 4.2V at 1.2C, then to 4.4V at 1.2C, then to 4.4V constant voltage to the cutoff current 0.05C, and then discharged to 3V at 1.2C. The initial capacity Q0 was recorded, and when the cycle reached the required number of times, the discharge capacity of the previous cycle was taken as the capacity Q2 of the battery, and the capacity retention rate (%) was calculated.

[0114] (7) 25℃ cycle test

[0115] The battery was placed in a (25±3)℃ environment for 3 hours, and when the cell body reached (25±3)℃, the battery was charged to 4.2V at 1.2C, then to 4.4V at 1.2C, then to 4.4V constant voltage to the cutoff current 0.05C, and then discharged to 3V at 1.2C. The initial capacity Q0 was recorded, and when the cycle reached the required number of times, the discharge capacity of the previous cycle was taken as the capacity Q2 of the battery, and the capacity retention rate (%) was calculated.

[0116] Comparative Example 1:

[0117] The prepared graphite slurry was coated on a 5μm thick copper foil using an extrusion coater, and the area density was 12.0mg / cm 2The coating process is completed, and the coated electrode sheets are prepared at a density of 1.8 g / cm³. 3 The compaction density is rolled, and the rolled electrode is placed in a 100℃ oven for high-temperature storage for 4 hours to prepare the A electrode. The A electrode is then used to prepare a soft-pack battery cell.

[0118] Comparative Example 2:

[0119] First, a 5μm thick copper foil needs to be carbonized. A gravure coating machine is used to prepare the carbonized copper foil, maintaining a total carbon coating thickness of 1–1.5μm on both sides. After the carbonized foil is prepared, the prepared graphite slurry is applied onto the carbonized copper foil using an extrusion coating machine, achieving an areal density of 12.0 mg / cm³. 2 The coating process is completed, and the coated electrode sheets are prepared at a density of 1.8 g / cm³. 3 The compaction density is rolled, and the rolled electrode is placed in a 100℃ oven for high-temperature storage for 4 hours to prepare the B electrode. The B electrode is then used to prepare a soft-pack battery cell.

[0120] Example 1:

[0121] (1) Prepare functional coating slurry. The slurry formula is CMC (6%) + SBR (8%) + SP (3%) + functional additive ammonium bicarbonate (2%) + deionized water (81%).

[0122] (2) The prepared functional coating slurry is applied to a 5μm thick copper foil using a gravure coating machine to prepare the functional coating current collector of the present invention, maintaining the total thickness of the double-sided functional layer at 1.5μm;

[0123] (3) After the functional coating current collector is prepared, the prepared graphite slurry is coated onto the functional coating current collector using an extrusion coating machine, with an areal density of 12.0 mg / cm³. 2 The coating process is completed, and the coated electrode sheets are prepared at a density of 1.8 g / cm³. 3 The compaction density is rolled, and the rolled electrode is placed in a 100℃ oven for high-temperature storage for 4 hours to prepare C electrode sheets, and then the C electrode sheets are used to prepare soft-pack cells.

[0124] Example 2:

[0125] (1) Prepare functional coating slurry. The slurry formula is CMC (6%) + SBR (8%) + SP (3%) + functional additive ammonium bicarbonate (4%) + deionized water (79%).

[0126] (2) The functional coating slurry prepared above is applied to a 5μm copper foil using a gravure coating machine to prepare the functional coating current collector of the present invention, maintaining the total thickness of the double-sided functional layer at 1.5μm;

[0127] (3) After the functional coating current collector is prepared, the prepared graphite slurry is coated on the functional coating current collector by using an extrusion coater, and the surface density is 12.0 mg / cm 2 , the coating process is completed, the coated pole piece is rolled according to the compaction density of 1.8 g / cm 3 , the rolled pole piece is placed into a 100℃ oven for high-temperature storage for 4h, the D pole piece is prepared, and a soft package battery is prepared by using the D pole piece.

[0128] Example 3:

[0129] (1) The functional coating slurry is prepared, and the slurry formula is CMC (6%) + SBR (8%) + SP (3%) + functional additive ammonium bicarbonate (6%) + deionized water (77%);

[0130] (2) The prepared functional coating slurry is coated on the 5μm copper foil by using a gravure coater to prepare the functional coating current collector, and the total thickness of the double-sided functional layer is maintained at 1.5μm;

[0131] (3) After the functional coating current collector is prepared, the prepared graphite slurry is coated on the functional coating current collector by using an extrusion coater, and the surface density is 12.0 mg / cm 2 , the coating process is completed, the coated pole piece is rolled according to the compaction density of 1.8 g / cm 3 , the rolled pole piece is placed into a 100℃ oven for high-temperature storage for 4h, the D pole piece is prepared, and a soft package battery is prepared by using the D pole piece.

[0132] Example 4:

[0133] (1) The functional coating slurry is prepared, and the slurry formula is CMC (6%) + SBR (8%) + SP (3%) + functional additive ammonium bicarbonate (0.5%) + deionized water (82.5%);

[0134] (2) The prepared functional coating slurry is coated on the 5μm copper foil by using a gravure coater to prepare the functional coating current collector, and the total thickness of the double-sided functional layer is maintained at 1.5μm;

[0135] (3) After the functional coating current collector is prepared, the prepared graphite slurry is coated on the functional coating current collector by using an extrusion coater, and the surface density is 12.0 mg / cm 2 , the coating process is completed, the coated pole piece is rolled according to the compaction density of 1.8 g / cm 3 , the rolled pole piece is placed into a 100℃ oven for high-temperature storage for 4h, the D pole piece is prepared, and a soft package battery is prepared by using the D pole piece.

[0136] Example 5:

[0137] (1) Prepare a functional coating slurry, the slurry formula is CMC (6%) + SBR (8%) + SP (3%) + functional additive ammonium bicarbonate (12%) + deionized water (71%);

[0138] (2) The above prepared functional coating slurry is coated on a 5μm copper foil by a gravure coater to prepare the functional coating current collector of the application, and the total thickness of the double-sided functional layer is maintained at 1.5μm;

[0139] (3) After the functional coating current collector is prepared, the above prepared graphite slurry is coated on the functional coating current collector by an extrusion coater, and the areal density is 12.0mg / cm 2 , the coating process is completed, the coated pole piece is rolled according to the compaction density of 1.8g / cm 3 , the rolled pole piece is placed in a 100℃ oven for high-temperature storage for 4h, an E pole piece is prepared, and a soft package battery is prepared using the E pole piece.

[0140] Table 1 Performance test of negative electrode current collector, negative electrode pole piece and battery prepared by examples and comparative examples

[0141]

[0142]

[0143] The peeling force refers to the peeling force between the active material layer and the negative electrode current collector.

[0144] From the above comparison, it can be seen that as the amount of functional additives increases, the energy density of the battery tends to decrease, but the edge of example 4 appears lithium precipitation due to the too small amount of additives, which further leads to the thickness of the soft package battery being too large, and the energy density is reduced, so the actual energy density result is the same as that of example 1.

[0145] The above describes the embodiments of the application. However, the application is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A negative electrode sheet characterized by comprising: The negative electrode sheet includes a negative electrode current collector; the negative electrode current collector includes a current collector substrate and a functional coating layer; the functional coating layer is arranged on at least one side surface of the current collector substrate; the functional coating layer includes a functional additive, a dispersant, a conductive agent and a binder, and the functional additive is at least one selected from the group consisting of ammonium carbonate, ammonium bicarbonate, azodicarbonamide, benzoic acid, oxalic acid and p-toluene sulfonyl hydrazide; The negative electrode sheet satisfies: 0.5≤H×W / C≤3.5; H: the proportion of the mass of the functional additive in the functional coating layer to the total mass of the functional coating layer; W: the proportion of the mass of the conductive agent in the functional coating layer to the total mass of the functional coating layer; C: areal density of the negative electrode sheet, in g / cm 2 ; The proportion H of the mass of the functional additive in the functional coating layer to the total mass of the functional coating layer is 2% to 30%; the proportion W of the mass of the conductive agent in the functional coating layer to the total mass of the functional coating layer is 10 to 20 wt%; the area density C of the negative electrode sheet is 11 to 16 mg / cm 2 .

2. The negative electrode sheet according to claim 1, characterized by The functional coating layer includes the following components by mass: functional additive 2-9 mass parts; conductive agent 1-10 mass parts; dispersant 1-10 mass parts; binder 5-15 mass parts.

3. The negative electrode sheet according to claim 2, characterized by The functional coating layer satisfies: 1≤m 功能添加剂 / m 导电剂 ≤3; wherein m 功能添加剂 is the mass of the functional additive in the functional coating layer; m 导电剂 is the mass of the conductive agent in the functional coating layer.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized by, The negative electrode sheet includes an active material layer; the active material layer is arranged on at least one side surface of the negative electrode current collector.

5. The negative electrode sheet according to claim 4, characterized by The active material layer has a porous structure; And / or, the peeling force between the active material layer and the negative electrode current collector is 10 N / m or more.

6. A negative electrode sheet characterized by comprising: The negative electrode sheet includes a negative electrode current collector; the negative electrode current collector includes a current collector substrate and a functional layer; the functional layer is arranged on at least one side surface of the current collector substrate; the functional layer has a porous structure; the functional layer includes a dispersant, a conductive agent and a binder; The negative electrode sheet satisfies: 3.4≤P×Q / C≤10; P: porosity of the negative electrode sheet; Q: the proportion of the mass of the conductive agent in the functional layer to the total mass of the functional layer; C: areal density of the negative electrode sheet, in g / cm 2 ; The porosity P of the negative electrode sheet is 20% or more; the proportion Q of the mass of the conductive agent in the functional layer to the total mass of the functional layer is 10-30 wt%; the area density C of the negative electrode sheet is 11-16 mg / cm 2 .

7. The negative electrode sheet according to claim 6, characterized by The porosity of the functional layer is 1-15%.

8. The negative electrode sheet according to claim 6, characterized by The functional layer includes the following components by mass: conductive agent 1-10 mass parts; dispersant 1-10 mass parts; binder 5-15 mass parts.

9. The negative electrode sheet according to any one of claims 6 to 8, wherein The negative electrode sheet includes an active material layer; the active material layer is arranged on at least one side surface of the negative electrode current collector.

10. The negative electrode sheet according to claim 9, wherein The active material layer has a porous structure; And / or, the peeling force between the active material layer and the negative electrode current collector is 10 N / m or more.

11. A battery including the negative electrode sheet according to any one of claims 1-10.

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