CN118231812A - Quantitative lithium pre-forming method for high-nickel system high-energy lithium ion battery - Google Patents
Quantitative lithium pre-forming method for high-nickel system high-energy lithium ion battery Download PDFInfo
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Abstract
The invention provides a method for quantitatively pre-lithium of a high-nickel system high-energy lithium ion battery, which comprises the following steps: the lithium foil is adopted as a lithium supplementing raw material, and a fumed silica gel layer is coated on the surface of the lithium foil, wherein the size of the lithium foil and the edge of the pole piece form a micro-step structure, namely the size of a substrate active substance is larger than the size of the lithium foil; the invention completes the process of mutual matching and integration through the effective edge quantitative control, the hot flat pressing compound coordination mode and the continuous stable die cutting process, and the technical route realizes the low cost, high safety and high efficiency pre-lithiation of the battery assembly process, finally improves the first effect and the circulation stability of the assembled lithium ion battery and reduces the impedance of the lithium ion battery.
Description
Technical Field
The invention relates to the technical field of lithium battery manufacturing, in particular to a method for quantitatively pre-lithium of a high-nickel-system high-energy lithium ion battery.
Background
The lithium ion battery is paid attention to because of higher energy density and stable cycle performance, and the high-energy lithium ion battery constructed by a high-nickel system is gradually used as a development trend at present, for example, ternary materials are used, and the increase of the nickel content can be helpful for increasing the unit cell volume and increasing the reversible lithium intercalation amount of the materials. The corresponding negative electrode material also needs to have high energy characteristics, and for the traditional graphite negative electrode material, the silicon-oxygen negative electrode material has the advantages of high specific volume and high voltage window, so that the silicon-oxygen negative electrode material gradually becomes the first-choice negative electrode material of the high-energy lithium ion battery. However, the silicon-oxygen negative electrode still has a plurality of problems, wherein the silicon-based material is mainly used for irreversibly consuming lithium ions from the positive electrode in the first cycle, the formed irreversible phases such as Li 4SO4、Li2 O and the like cause irreversible capacity loss, and secondly, SEI films and volume expansion problems are formed, so that the first effect and capacity of the battery are reduced, and the high-energy advantage of the ternary positive electrode and the silicon-oxygen negative electrode system cannot be exerted.
At present, aiming at the problems of low initial efficiency and poor cycling stability of the system battery, the main solution is that the negative electrode is mainly pre-lithiated, an SEI film is formed by replacing lithium ions in the positive electrode in the first charge-discharge stage, and redundant doping products are not introduced while lithium ions are consumed by the positive electrode. The conventional negative electrode pre-lithium method is based on lithium powder or lithium foil pre-lithium.
Aiming at the existing technical route and technological method of lithium pre-preparation of the negative electrode, the powder pre-lithium method uses organic lithium powder as a raw material, and the conventional method is divided into spraying, blade coating and soaking, and the lithium powder suspension is prepared by adopting electrolyte in the pre-lithium process or directly adopts lithium powder as the raw material. The specific process is that, for example, organic lithium powder is mainly dispersed in an organic solvent through spray gun spraying, and the organic lithium powder is sprayed to the surface of the negative electrode through the spray gun, and in the spraying process, the negative electrode active material area needs to be repeatedly sprayed and lithium powder pollution cannot be caused to the tab in consideration of the uniformity of dispersion. The blade coating process is to place the lithium powder on the surface of the negative electrode plate in a flat manner, and complete the pre-lithium process through blade coating. The infiltration process is to immerse the negative electrode plate in the lithium powder solution and attach the lithium powder on the surface of the active material in a manner of lifting the electrode plate. The problems of difficult uniform dispersion of lithium powder, harm to the environment due to volatilization of a dispersion solvent, high atmosphere control cost, high powder danger degree and the like of the lithium powder are not solved yet in the amplification and industrialization related to the powder pre-lithium. For example, lithium powder layering phenomenon (lithium powder is low in density and easy to float in solution) is easy to occur in a lithium powder suspension in a spraying process, static electricity and scattering phenomenon are easy to occur in the environment of lithium powder in a blade coating process, and uniform adhesion of the lithium powder on the surface of a negative electrode cannot be realized in an infiltration process. The existing lithium powder is easy to have the technical problems of uneven powder distribution, easy volatilization of a dispersion solvent and easy scattering of powder in the lithium powder pre-preparation process, so that the pre-lithium safety is poor. The use of inert atmospheres and organic solvents brings about overall process costs and environmental problems.
Unlike lithium powder pre-lithium, lithium foil pre-lithium mainly adopts a mode of rolling and compounding a metal foil and a negative electrode plate to pre-lithiate the negative electrode material. For example, the metal lithium foil with a certain thickness and the negative electrode plate are compounded by rolling, the metal lithium foil is in close contact with the negative electrode in the compounding process, the integral pre-lithiation process is high in efficiency, and industrialization is easier to realize than the lithium powder pre-lithiation process. However, lithium foil pre-lithium also faces a plurality of problems, for example, the existing scheme mainly adopts 20 μm compact lithium foil as a main raw material, the total amount of the pre-lithium cannot be controlled, the utilization range of active lithium is exceeded, and dead lithium is easily generated in the circulation process to cause circulation attenuation. In addition, the existing lithium foil technology circuit avoids the safety problem caused by lithium powder pre-lithium, and the problems that electrolyte cannot infiltrate to the surface of a negative electrode material covered by a lithium foil after the electrolyte is filled into a battery cell and the like cannot meet the further industrialization requirement.
And in the rolling compounding process, the lithium foil is longitudinally extended under the action of compressive stress, so that the foil is easy to deform unevenly, and the pole piece subjected to pre-lithium is easy to cause the adhesion phenomenon of the cutter head and the foil in the die cutting process. For example, the existing pre-lithium process adopts the processes of cathode pole roll, pole roll and lithium foil secondary rolling and compounding, pole piece die cutting and battery core assembling. In the secondary rolling compounding process, the lithium foil is easy to cause overlarge unidirectional extension and deformation (longitudinal extension along the press roller) due to the ductility of the lithium foil. The negative electrode coil and the lithium foil are compounded and then subjected to die cutting, so that the problems of cutter head corrosion and later maintenance caused by direct contact of a die cutting head and the lithium foil are easily caused, burrs at the edge of the lithium foil are also caused, and the risk of short circuit of a battery exists, so that the performance of the battery is influenced.
Disclosure of Invention
Aiming at the technical problems, the invention provides a quantitative pre-lithium method for a high-nickel system high-energy lithium ion battery, which adopts a porous lithium foil for pre-lithium and is controlled from the aspects of a compound mode, edge quantitative control and die cutting process technology, so that a high-safety, low-pollution, accurate and efficient pre-treatment method is realized.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
A method for quantitatively pre-lithium of a high-nickel system high-energy lithium ion battery comprises the following steps:
(1) The method comprises the steps of adopting a lithium foil as a lithium supplementing raw material, conveying the lithium foil to a surface film coating mechanism, and coating fumed silica gel on the surface of the lithium foil to form a buffer layer;
(2) Respectively feeding the negative electrode coil and the lithium foil coated with the buffer layer to a pressure roller, adjusting coiled materials at different positions to the same plane, and loading the lithium foil on the negative electrode plate through a hot flat pressing composite mechanism, wherein the buffer layer is arranged between the lithium foil and the negative electrode plate; removing a release film on the surface of the lithium foil after hot flat pressing compounding and rolling to obtain a pre-lithium negative electrode roll;
(3) Die cutting is carried out on the anode coil after lithium preparation, and in the die cutting process, the cutter head is not directly contacted with the lithium foil; the edge distance between the lithium foil and the negative electrode plate is quantitatively controlled to form a micro-step structure, namely the size of the negative electrode plate is larger than that of the lithium foil. In the die cutting process, the cutter head is not directly contacted with the lithium foil, so that continuous operation of equipment is ensured to be unaffected; the lithium foil die-cutting machine has the advantages that the pole piece is not completely covered by the lithium foil, can continuously run in the die-cutting process, is compatible with the existing process equipment without replacement, and cannot cause corrosion and adhesion to the equipment.
The micro-step structure is easy to form a local enhanced electric field, the edge effect brought by the micro-step structure accelerates the activation process of lithium ions, and the phenomena of excessive lithium sources and low activation efficiency of the lithium sources caused by full coverage, namely, the phenomenon of circulating dead lithium caused by incapability of timely conversion, are avoided, and the system circulation stability is influenced.
The lithium foil in the step (1) is a porous lithium foil, the porosity of the porous lithium foil is 10% -15%, the pore diameter is 1 mu m, and the thickness is 3-10 mu m; the pore diameter is obviously larger than the radius of lithium ions (r Li + =2.84 nm) and the molecular diameter of the electrolyte, thereby being beneficial to the rapid shuttling of lithium ions and the permeation of the electrolyte.
The preparation method of the fumed silica gel in the step (1) comprises the following steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2, uniformly mixing to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 60-80 ℃ for 15-20s, and cooling to form the fumed silica gel; the fumed silica gel is coated on the surface of the lithium foil by a blade coating mode, and the gap between the blade edges is 5-50 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L, the concentration of fumed silica in the mixed dispersion liquid is 10-30 mg/ml, and the organic solvent comprises ethylene carbonate, dimethyl carbonate and tetraethylene glycol dimethyl ether; the fumed silica has a particle size of 0.2-0.5 μm. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel to promote the uniform deposition of active lithium ions.
The purpose of coating the silica gel layer: on the one hand, when the micro-step structure is constructed by utilizing the edge effect, the phenomenon of nonuniform lithium activation is easy to cause, the SiO 2 forms a network ion channel (a buffer layer is constructed), and on the premise of activating lithium ions of the micro-step structure, the uniform deposition of the lithium ions on the surface of the anode material through the network ion channel is promoted, so that the phenomenon of lithium precipitation caused by overlarge local current density and nonuniform conduction rate during lithium intercalation is avoided; on the other hand, the contact between the lithium foil and the negative electrode plate is solid-solid contact, and the solid-liquid contact is changed into interlayer solid-liquid contact after the gas phase SiO 2 mixed solution is added, so that the contact wettability is increased, and the conduction efficiency is improved.
The conditions of hot-pressing compounding in the step (2) are as follows: the temperature is 80-100 ℃, the flattening pressure is 8000-9000 kgf, and the flattening holding time is 20-25 s. When the hot flat pressure is less than 8000 kgf, the internal resistance of the high-nickel lithium ion battery is larger, so that the circulation stability is reduced. When the hot flat pressing pressure is more than 9000kgf, the corresponding lithium foil porosity is reduced, the self liquid retention capacity is reduced, active lithium ions cannot be effectively converted, and the first effect is reduced.
The hot flat pressing compounding mechanism in the step (2) is divided into a roll feeding part and a roll winding part, wherein the roll feeding part is used for unreeling, and the upper and lower lithium foils and the middle negative coiled material are conveyed to the hot flat pressing mechanism for hot pressing compounding, so that the pre-lithium of the negative pole piece is completed; the winding part uses winding mechanisms, the upper layer winding mechanism and the lower layer winding mechanism respectively retract the negative electrode roll pre-lithium foil upper layer release film and the lower layer release film, and the middle layer winding mechanism retracts the negative electrode coiled material after pre-lithium.
The release film refers to a separator film that is not tacky or has slight tackiness after contact with limited conditions of a lithium foil material.
In the step (3), the control ratio P Lithium ion battery = (full-size area of the electrode plate-S Lithium ion battery )/full-size area of the electrode plate is 100%, wherein the full-size area of the electrode plate does not contain a tab, S Lithium ion battery is the area of the lithium foil, and the edge control ratio P Lithium ion battery is 10% -15%; the length and width of the lithium foil are the same relative to the size reduction value of the battery negative electrode plate.
The edge effect capacity C of the lithium foil pre-lithium is: c=s Lithium ion battery *H Lithium ion battery *ρ Lithium ion battery *C Lithium foil ×0.9, where S Lithium ion battery is the area of the lithium foil, H Lithium ion battery is the thickness of the lithium foil, ρ Lithium ion battery is the metal density of the lithium foil, C Lithium foil is the theoretical gram capacity of lithium metal 3860 mAh/g, and 0.9 is the control coefficient.
The high-nickel system high-energy lithium ion battery is obtained by the quantitative pre-lithium method.
The invention has the following beneficial effects:
1. The lithium foil pre-lithium is adopted as a technical route of the lithium foil pre-lithium, and porous lithium foil is mainly adopted as a raw material, so that the safety is improved, and the environmental pollution is reduced; and the porous lithium foil is adopted as a raw material, the surface gaps are uniformly distributed, and the electrolyte can fully infiltrate to the surface of the anode active material after being filled, so that the circulation stability is improved.
2. According to the invention, the gel buffer layer is constructed by adopting fumed silica, the SiO 2 forms a network ion channel, on the premise of activating lithium ions by a micro-step structure, the uniform deposition of lithium ions on the surface of the anode material through the network ion channel is promoted, and the phenomenon of lithium precipitation caused by overlarge local current density and uneven conduction rate during lithium intercalation is avoided. On the other hand, the contact between the lithium foil and the negative electrode plate is solid-solid contact, and the solid-liquid contact is changed into interlayer solid-liquid contact after the gas phase SiO 2 mixed solution is added, so that the contact wettability is increased, and the conduction efficiency is improved.
3. The use of the lithium foil edge effect quantitative control method can avoid the problems of cycle dead lithium and polarization increase caused by excessive lithium source in the conventional lithium foil pre-lithium process; the quantitative lithium pre-forming and hot-pressing die-cutting integrated equipment is combined, and the problems of high cost, high danger and low efficiency in the technical process are solved. The integrated pre-lithium, hot pressing and die cutting are realized in the process, and the problems of poor composite effect and equipment loss are avoided. The whole technical route realizes the low-cost, high-safety and high-efficiency pre-lithiated lithium ion soft package battery assembly process of a high-nickel system.
4. The lithium powder pre-lithium or electrochemical pre-lithium needs to additionally use electrolyte or adopt an inert atmosphere environment under the condition of controlling the environment humidity, and the quantitative porous lithium foil pre-lithium method only needs to regulate the environment humidity without increasing the use of the electrolyte and the inert atmosphere, so that the overall process cost is effectively reduced.
5. Control precision and efficiency are improved: conventional lithium foil is pre-lithiated, and negative electrode winding secondary rolling is carried out in a rolling mode, so that the lithium foil is easy to cause unidirectional bad deformation, and the process flow progress is influenced. Through the pole roll die cutting procedure, the adhesion between a die cutting head and a lithium foil is easy to cause corrosion, and intermittent maintenance of equipment is required to be added in the process flow; and the edge burrs in the lithium foil die cutting process can be caused to damage the battery. In the conventional lithium foil pre-lithium method, the whole process flow cannot be continuously operated. The quantitative porous lithium foil pre-lithium method adopts a hot pressing process, avoids the bad deformation of the lithium foil or the adhesion phenomenon with a cutter head through size control and hot flat pressing regulation, can continuously operate without interruption, and effectively improves the pre-lithium precision and the assembly efficiency.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of the structure of the pole piece before and after pre-lithium.
Fig. 2 is a graph showing the cycle performance of pre-lithium soft-pack batteries before and after pre-lithium and at different thicknesses.
Fig. 3 is a graph of impedance performance before and after cycling of pre-lithium soft pack batteries of different thicknesses before and after pre-lithium.
Fig. 4 is a graph of cycling performance and impedance performance of pre-lithium soft pack batteries before and after coating the fumed silica gel layer.
Fig. 5 is a graph of the first-turn impedance performance of the edge-quantitatively controlled pre-lithium pouch cell.
Fig. 6 shows the first charge-discharge and cycling performance of a pre-lithium high-energy lithium ion battery.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without any inventive effort, are intended to be within the scope of the invention.
The negative electrode of the lithium ion battery used in the embodiment of the invention is a silicon-oxygen negative electrode material, and the positive electrode is a 9-series ternary material. The preparation and specific implementation process of the positive electrode comprises the following steps: (1) And mixing and stirring solvent NMP and solute PVDF to dissolve, obtaining a glue solution with 7% of solid content, and taking out for standby. (2) Adding ternary main materials of polycrystal 90ED and monocrystal 93SC into a homogenizing pot, wherein the adding ratio is 7: and 3, adding the conductive agent SP after dry mixing and stirring, and performing dispersion and stirring. (3) Adding the glue solution for standby in the dry-mixed main material, stirring, and then adding the CNT for high-speed stirring. (4) Adding NMP solvent to regulate the viscosity of the slurry to 5500-8000 mPa.s and the solid content to 72%, thus completing the preparation of the positive electrode slurry.
The preparation and specific implementation process of the negative electrode silica 550 are as follows: (1) And (3) spreading the graphite and silica 600 mixed dry powder in a homogenizing pot, and carrying out dry mixing and stirring. (2) PAA, SWCNT and deionized water are added and stirred at high speed. (3) Adding deionized water to regulate viscosity, and adding SBR to stir slowly at low speed. (4) And (3) regulating the viscosity of the slurry to 3000-5000 mPa.s and the solid content to 50%, thus completing the preparation of the cathode silica 550 slurry.
After the slurry preparation is finished, a slurry coating process is carried out, the anode slurry is coated to a 12 mu m aluminum foil, the cathode slurry is coated to a6 mu m copper foil, the surface density is controlled, and the coating of the pole piece is completed by adopting double-sided intermittent coating. And a rolling procedure, namely finishing the manufacturing of the pre-lithium pole piece of the earlier-stage 9-series system by double-sided rolling.
Example 1
The embodiment provides a method for quantitatively pre-lithium of a high-energy lithium ion battery, which comprises the following steps:
Pre-lithium by using a lithium foil with a thickness of 5 mu m and a porosity of 10%;
The cathode electrode is connected to an unreeling mechanism of the hot-pressing compound equipment in a rolling way, the unreeling mechanism on the lithium foil and the unreeling mechanism under the lithium foil are connected, the lithium foil is conveyed to a surface film coating mechanism, and the fumed silica gel is coated on the surface of the lithium foil in a blade coating way. And (3) rolling the cathode electrode roll and the coated lithium foil to a pressure roller, adjusting coiled materials at different positions to the same plane, and entering a hot-pressing compounding mechanism, wherein the hot-pressing compounding mechanism adopts double-plane hot pressing, the hot-pressing temperature is 80 ℃, the flat pressing pressure is 8000 kgf, and the flat pressing holding time is 20 s. And after the hot pressing is finished, the composite pole coil is conveyed to a tail end winding mechanism, and the upper part of the winding mechanism is connected with the release film winding and the lower part is connected with the release film winding.
The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (excluding a pole lug) is 75 mm x 105 mm, the size of a double-sided pre-lithium foil is 70 mm x 100 mm, the control ratio P Lithium ion battery is 11%, as shown in fig. 1, the cutter head is ensured not to be directly contacted with the lithium foil in the die cutting process, and the continuous operation of the equipment is ensured not to be influenced.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 70 ℃ for 18s, and cooling to form the fumed silica gel; wherein the fumed silica gel is coated on the surface of the lithium foil by a doctor blade method, and the gap between the doctor blade and the edge of the doctor blade is 25 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L, the concentration of fumed silica in the mixed dispersion liquid is 20 mg/ml, and the organic solvent is ethylene carbonate. The fumed silica particles have a size of 0.3. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Example 2
The embodiment provides a method for quantitatively pre-lithium of a high-energy lithium ion battery, which comprises the following steps:
Pre-lithium by using a lithium foil with a thickness of 3 mu m and a porosity of 10%;
the negative electrode is connected to the unreeling mechanism of the hot flat pressing compound device in a rolling way, the unreeling mechanism on the lithium foil and the unreeling mechanism under the lithium foil are connected, the lithium foil is conveyed to the surface film coating mechanism, and the mixed suspension is coated on the surface of the lithium foil in a blade coating way. And (3) rolling the cathode electrode roll and the coated lithium foil to a pressure roller, adjusting coiled materials at different positions to the same plane, and entering a hot leveling and pressing composite mechanism, wherein the hot leveling and pressing composite mechanism adopts double-plane hot leveling and pressing, the hot leveling and pressing temperature is 90 ℃, the leveling and pressing pressure is 9000 kgf, and the leveling and pressing holding time is 25 s. After the hot platen press is finished, the composite pole roll is conveyed to a tail end rolling mechanism, and the upper part of the rolling mechanism is connected with a release film rolling device, and the lower part of the rolling mechanism is connected with the release film rolling device;
The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (not including a pole lug) is 75 mm x 105 mm, the size of a double-sided pre-lithium foil is 68 mm x 98 mm, the control proportion P Lithium ion battery is 15%, the cutter head is ensured not to be in direct contact with the lithium foil in the die cutting process, and the continuous operation of the equipment is ensured not to be influenced.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent tetraethylene glycol dimethyl ether, then adding gas phase SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 60 ℃ for 20s, and cooling to form the fumed silica gel; fumed silica gel was coated onto the surface of the lithium foil by knife coating, with a doctor blade gap of 10 μm.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion was 1mol/L, the concentration of fumed silica in the mixed dispersion was 10 mg/ml, and the particle size of fumed silica was 0.5. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Example 3
The embodiment provides a method for quantitatively pre-lithium of a high-energy lithium ion battery, which comprises the following steps:
pre-lithium by using a lithium foil with a thickness of 7 mu m and a porosity of 12%;
the negative electrode is connected to the unreeling mechanism of the hot flat pressing compound device in a rolling way, the unreeling mechanism on the lithium foil and the unreeling mechanism under the lithium foil are connected, the lithium foil is conveyed to the surface film coating mechanism, and the mixed suspension is coated on the surface of the lithium foil in a blade coating way. And (3) rolling the cathode electrode roll and the coated lithium foil to a pressure roller, adjusting coiled materials at different positions to the same plane, and entering a hot leveling and pressing composite mechanism, wherein the hot leveling and pressing composite mechanism adopts double-plane hot leveling and pressing, the hot leveling and pressing temperature is 85 ℃, the leveling and pressing pressure is 8500 kgf, and the leveling and pressing holding time is 22 s. After the hot platen press is finished, the composite pole roll is conveyed to a tail end rolling mechanism, and the upper part of the rolling mechanism is connected with a release film rolling device, and the lower part of the rolling mechanism is connected with the release film rolling device;
The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (not including a pole lug) is 75 mm x 105 mm, the size of a double-sided pre-lithium foil is 69 mm x 99 mm, the control proportion P Lithium ion battery is 13%, the cutter head is ensured not to be directly contacted with the lithium foil in the die cutting process, and the continuous operation of the equipment is ensured not to be influenced.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in organic solvent dimethyl carbonate, then adding fumed SiO 2 to obtain mixed dispersion liquid, dissolving the mixed dispersion liquid at 80 ℃ for 15s, and cooling to form the fumed silica gel; fumed silica gel is coated on the surface of the lithium foil by a blade coating mode, and the gap between the blade edges is 5 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion is 1mol/L, the concentration of fumed silica in the mixed dispersion is 10-30 mg/ml, and the particle size of the fumed silica is 0.5 μm. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Example 4
The embodiment provides a method for quantitatively pre-lithium of a high-energy lithium ion battery, which comprises the following steps:
pre-lithium by using a lithium foil with a thickness of 10 mu m and a porosity of 15%;
The negative electrode is connected to the unreeling mechanism of the hot flat pressing compound device in a rolling way, the unreeling mechanism on the lithium foil and the unreeling mechanism under the lithium foil are connected, the lithium foil is conveyed to the surface film coating mechanism, and the mixed suspension is coated on the surface of the lithium foil in a blade coating way. Feeding the negative electrode coil and the coated lithium foil to a pressure roller, adjusting coiled materials at different positions to the same plane, entering a hot flat pressing composite mechanism, adopting double-plane hot flat pressing by the hot flat pressing composite mechanism, adopting hot flat pressing temperature of 80 ℃, flat pressing pressure of 8000 kgf, flat pressing holding time of 20 s, conveying the composite electrode coil to a tail end rolling mechanism after hot pressing is finished, and connecting a release film rolling above the rolling mechanism and a release film rolling below the rolling mechanism;
The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (not including a pole lug) is 75 mm x 105 mm, the size of a double-sided pre-lithium foil is 69 mm x 99 mm, the control proportion P Lithium ion battery is 13%, the cutter head is ensured not to be directly contacted with the lithium foil in the die cutting process, and the continuous operation of the equipment is ensured not to be influenced.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent of ethylene carbonate, adding fumed SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 75 ℃ for 20s, and cooling to form the fumed silica gel; fumed silica gel was coated onto the surface of the lithium foil by knife coating with a knife edge gap of 50 μm.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion was 1mol/L, the concentration of fumed silica in the mixed dispersion was 30 mg/ml, and the particle size of fumed silica was 0.2. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Example 5
The embodiment provides a method for quantitatively pre-lithium of a high-energy lithium ion battery, which comprises the following steps:
pre-lithium by using a lithium foil with a thickness of 5 mu m and a porosity of 12%;
the negative electrode is connected to the unreeling mechanism of the hot-pressing compound equipment in a rolling way, the lithium foil upper unreeling mechanism and the lithium foil lower unreeling mechanism are connected, the lithium foil is conveyed to the surface film coating mechanism, and the mixed suspension is coated on the surface of the lithium foil in a blade coating way. The negative electrode coil and the coated lithium foil are fed to a pressure roller and coiled materials at different positions are regulated to the same plane, the negative electrode coil and the coated lithium foil enter a hot-pressing compounding mechanism, the hot-pressing compounding mechanism adopts double-plane hot pressing, the hot-pressing temperature is 100 ℃, the flat pressing pressure is 8000 kgf, the flat pressing holding time is 20 s, the compound electrode coil is conveyed to a tail end rolling mechanism after the hot pressing is finished, and the upper part of the rolling mechanism is connected with a release film rolling mechanism, and the lower part of the rolling mechanism is connected with the release film rolling mechanism;
The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (not including a pole lug) is 75 mm x 105 mm, the size of a double-sided pre-lithium foil is 69 mm x 99 mm, the control proportion P Lithium ion battery is 13%, the cutter head is ensured not to be directly contacted with the lithium foil in the die cutting process, and the continuous operation of the equipment is ensured not to be influenced.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in organic solvent dimethyl carbonate, then adding fumed SiO 2 to obtain mixed dispersion liquid, dissolving the mixed dispersion liquid at 80 ℃ for 20s, and cooling to form the fumed silica gel; fumed silica gel was coated onto the surface of the lithium foil by knife coating, with a doctor blade gap of 40 μm.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion was 1mol/L, the concentration of fumed silica in the mixed dispersion was 15 mg/ml, and the particle size of fumed silica was 0.4. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Comparative example 1
This comparative example differs from example 1 in that the negative electrode sheet was not pre-lithiated. The negative electrode roll was transferred to a die cutting apparatus with die cut tab sizes (excluding tabs) of 75 mm by 105 mm.
Comparative example 2
This comparative example provides a method for quantifying pre-lithium in a high energy lithium ion battery, which differs from example 1 in that the porous lithium foil has a thickness of 20 μm, comprising the steps of:
pre-lithium by using a lithium foil with a thickness of 20 mu m and a porosity of 10%;
The negative electrode coil is connected to an unreeling mechanism of hot-pressing compounding equipment, a lithium foil upper unreeling mechanism and a lithium foil lower unreeling mechanism are connected, the lithium foil is conveyed to a surface film covering mechanism, fumed silica gel is coated on the surface of the lithium foil in a doctor-blading mode, rolls are conveyed to a pressure roller to adjust coiled materials at different positions to the same plane to enter the hot-pressing compounding mechanism, the hot-pressing compounding mechanism adopts double-plane hot pressing, the hot-pressing temperature is 80 ℃, the flat pressing pressure is 8000 kgf, the flat pressing holding time is 20: 20 s, the compound electrode coil is conveyed to a tail end rolling mechanism after the hot pressing is finished, and a release film is connected to the upper part of the rolling mechanism and the lower part of the rolling mechanism;
The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (not including a pole lug) is 75 mm x 105 mm, the size of a double-sided pre-lithium foil is 70 mm x 100 mm, the control ratio P Lithium ion battery is 11%, the cutter head is ensured not to be directly contacted with the lithium foil in the die cutting process, and the continuous operation of the equipment is ensured not to be influenced.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 70 ℃ for 18s, and cooling to form the fumed silica gel; wherein the fumed silica gel is coated on the surface of the lithium foil by a doctor blade method, and the gap between the doctor blade and the edge of the doctor blade is 25 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L, the concentration of fumed silica in the mixed dispersion liquid is 20 mg/ml, and the organic solvent is ethylene carbonate. The fumed silica particles have a size of 0.3. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Comparative example 3
The difference between this comparative example and example 1 is that the hot pressing pressure is 5500 kgf and the porosity of the lithium foil is 20%. The pre-lithium step is as follows:
Pre-lithium by using a lithium foil with a thickness of 5 mu m and a porosity of 20%;
The cathode electrode is connected to an unreeling mechanism of the hot-pressing compounding device in a rolling way, the unreeling mechanism is connected with a lithium foil upper unreeling mechanism and a lithium foil lower unreeling mechanism, the lithium foil is conveyed to a surface film covering mechanism, fumed silica gel is coated on the surface of the lithium foil in a blade coating mode, rolls are sent to a pressure roller to adjust coiled materials at different positions to the same plane to enter the hot-pressing compounding mechanism, the hot-pressing compounding mechanism adopts double-plane hot pressing, the hot-pressing temperature is 80 ℃, the flat pressing pressure is 5500 kgf, and the flat pressing holding time is 20 s. And after the hot pressing is finished, the composite pole coil is conveyed to a tail end winding mechanism, and the upper part of the winding mechanism is connected with the release film winding and the lower part is connected with the release film winding.
The compounded negative electrode coil is conveyed to die cutting equipment, the die cutting pole piece size (excluding the pole lugs) is 75 mm x 105 mm, the double-sided pre-lithium foil size is 70 mm x 100 mm, and the control proportion P Lithium ion battery is 11%.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 70 ℃ for 18s, and cooling to form the fumed silica gel; wherein the fumed silica gel is coated on the surface of the lithium foil by a doctor blade method, and the gap between the doctor blade and the edge of the doctor blade is 25 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L, the concentration of fumed silica in the mixed dispersion liquid is 20 mg/ml, and the organic solvent is ethylene carbonate. The fumed silica particles have a size of 0.3. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Comparative example 4
The difference between this comparative example and example 1 is that the hot pressing pressure is 11000 kgf, the porosity is 8%, and the pre-lithium procedure is as follows:
pre-lithium by using a lithium foil with a thickness of 5 mu m and a porosity of 8%;
The cathode electrode is connected to an unreeling mechanism of the hot-pressing compounding device in a rolling way, the unreeling mechanism is connected with a lithium foil upper unreeling mechanism and a lithium foil lower unreeling mechanism, the lithium foil is conveyed to a surface film covering mechanism, fumed silica gel is coated on the surface of the lithium foil in a blade coating mode, rolls are sent to a pressure roller to adjust coiled materials at different positions to the same plane to enter the hot-pressing compounding mechanism, the hot-pressing compounding mechanism adopts double-plane hot pressing, the hot-pressing temperature is 80 ℃, the flat pressing pressure is 11000 kgf, and the flat pressing holding time is 20 s. And after the hot pressing is finished, the composite pole coil is conveyed to a tail end winding mechanism, and the upper part of the winding mechanism is connected with the release film winding and the lower part is connected with the release film winding.
The compounded negative electrode coil is conveyed to die cutting equipment, the die cutting pole piece size (excluding the pole lugs) is 75 mm x 105 mm, the double-sided pre-lithium foil size is 70 mm x 100 mm, and the control proportion P Lithium ion battery is 11%.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 70 ℃ for 18s, and cooling to form the fumed silica gel; wherein the fumed silica gel is coated on the surface of the lithium foil by a doctor blade method, and the gap between the doctor blade and the edge of the doctor blade is 25 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L, the concentration of fumed silica in the mixed dispersion liquid is 20 mg/ml, and the organic solvent is ethylene carbonate. The fumed silica particles have a size of 0.3. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Comparative example 5
This comparative example provides a method for quantifying pre-lithium in a high energy lithium ion battery, differing from example 1 in that no fumed silica gel coating compounding is performed, comprising the steps of:
Pre-lithium by using a lithium foil with a thickness of 5 mu m and a porosity of 10%;
The negative electrode coil is connected to an unreeling mechanism of the hot-pressing compound device, the negative electrode coil and the lithium foil are fed to a pressure roller and are regulated to be on the same plane by connecting the lithium foil upper unreeling mechanism and the lithium foil lower unreeling mechanism, the coiled materials at different positions enter the hot-pressing compound device, the hot-pressing compound device adopts double-plane hot pressing, the hot-pressing temperature is 80 ℃, the flat pressing pressure is 8000 kgf, and the flat pressing holding time is 20 s. And after the hot pressing is finished, the composite pole coil is conveyed to a tail end winding mechanism, and the upper part of the winding mechanism is connected with the release film winding and the lower part is connected with the release film winding.
The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (not including a pole lug) is 75 mm x 105 mm, the size of a double-sided pre-lithium foil is 70 mm x 100 mm, the control ratio P Lithium ion battery is 11%, the cutter head is ensured not to be directly contacted with the lithium foil in the die cutting process, and the continuous operation of the equipment is ensured not to be influenced.
Comparative example 6
This comparative example provides a method for quantitatively pre-lithium of a high energy lithium ion battery, which is different from example 1 in that the overall pre-lithium, i.e., lithium foil and negative electrode tab (except tab) are the same size, comprises the following steps:
The method comprises the steps of pre-lithium by adopting lithium foil with the thickness of 5 mu m and the porosity of 10%, rolling a negative electrode to an unreeling mechanism of hot-pressing compounding equipment, connecting the lithium foil upper unreeling mechanism and the lithium foil lower unreeling mechanism, conveying the lithium foil to a surface film covering mechanism, coating fumed silica gel on the surface of the lithium foil in a blade coating mode, conveying the rolled materials to different positions of a pressure roller to the same plane, entering the hot-pressing compounding mechanism, hot-pressing the hot-pressing compounding mechanism by adopting double-plane hot-pressing, adopting the hot-pressing temperature of 80 ℃, the flat pressing pressure of 8000 kgf, the flat pressing holding time of 20 s, conveying the composite electrode roll to a tail end rolling mechanism after the hot-pressing is finished, and connecting a release film to roll above the rolling mechanism and connecting the release film to roll below the rolling mechanism;
And conveying the compounded negative electrode coil to die cutting equipment, wherein the die cutting pole piece (not including the pole lugs) is 75mm by 105 mm, and the size of the double-sided pre-lithium foil is 75mm by 105 mm, so that the lithium foil is fully pre-lithium.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 70 ℃ for 18s, and cooling to form the fumed silica gel; wherein the fumed silica gel is coated on the surface of the lithium foil by a doctor blade method, and the gap between the doctor blade and the edge of the doctor blade is 25 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L, the concentration of fumed silica in the mixed dispersion liquid is 20 mg/ml, and the organic solvent is ethylene carbonate. The fumed silica particles have a size of 0.3. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Comparative example 7
This comparative example provides a method for quantifying pre-lithium in a high energy lithium ion battery, which is different from example 1 in that the control ratio P Lithium ion battery is 8.9%, comprising the steps of:
The lithium foil with the thickness of 5 mu m and the porosity of 10% is adopted for pre-lithium, the cathode electrode is connected to an unreeling mechanism of hot-pressing compounding equipment, the lithium foil upper unreeling mechanism and the lithium foil lower unreeling mechanism are connected, the lithium foil is conveyed to a surface film covering mechanism, fumed silica gel is coated on the surface of the lithium foil in a blade coating mode, rolls are conveyed to pressure rollers to adjust rolls at different positions to the same plane, the rolls enter the hot-pressing compounding mechanism, the hot-pressing compounding mechanism adopts double-plane hot pressing, the hot-pressing temperature is 80 ℃, the flat pressing pressure is 8000 kgf, the flat pressing holding time is 20 s, the composite electrode roll is conveyed to a tail end winding mechanism after the hot pressing is finished, and the upper part of the winding mechanism is connected with a release film for winding and the lower part of the winding mechanism is connected with the release film for winding. The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (not including a pole lug) is 75 mm x 105 mm, the size of a double-sided pre-lithium foil is 71 mm x 101 mm, the control ratio P Lithium ion battery is 8.9%, the cutter head is ensured not to be directly contacted with the lithium foil in the die cutting process, and the continuous operation of the equipment is ensured not to be influenced.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 70 ℃ for 18s, and cooling to form the fumed silica gel; wherein the fumed silica gel is coated on the surface of the lithium foil by a doctor blade method, and the gap between the doctor blade and the edge of the doctor blade is 25 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L, the concentration of fumed silica in the mixed dispersion liquid is 20 mg/ml, and the organic solvent is ethylene carbonate. The fumed silica particles have a size of 0.3. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Comparative example 8
This comparative example provides a method for quantifying pre-lithium in a high energy lithium ion battery, which is different from example 1 in that the control ratio P Lithium ion battery is 21%, comprising the steps of:
The lithium foil with the thickness of 5 mu m and the porosity of 10% is adopted for pre-lithium, the cathode electrode is connected to an unreeling mechanism of hot-pressing compounding equipment, the lithium foil upper unreeling mechanism and the lithium foil lower unreeling mechanism are connected, the lithium foil is conveyed to a surface film covering mechanism, fumed silica gel is coated on the surface of the lithium foil in a blade coating mode, rolls are conveyed to pressure rollers to adjust rolls at different positions to the same plane, the rolls enter the hot-pressing compounding mechanism, the hot-pressing compounding mechanism adopts double-plane hot pressing, the hot-pressing temperature is 80 ℃, the flat pressing pressure is 8000 kgf, the flat pressing holding time is 20s, the composite electrode roll is conveyed to a tail end winding mechanism after the hot pressing is finished, and the upper part of the winding mechanism is connected with a release film for winding and the lower part of the winding mechanism is connected with the release film for winding. The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (not including a pole lug) is 75mm x 105 mm, the size of a double-sided pre-lithium foil is 65mm x 95mm, the control ratio P Lithium ion battery is 21%, the cutter head is ensured not to be directly contacted with the lithium foil in the die cutting process, and the continuous operation of the equipment is ensured not to be influenced.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 70 ℃ for 18s, and cooling to form the fumed silica gel; wherein the fumed silica gel is coated on the surface of the lithium foil by a doctor blade method, and the gap between the doctor blade and the edge of the doctor blade is 25 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L, the concentration of fumed silica in the mixed dispersion liquid is 20 mg/ml, and the organic solvent is ethylene carbonate. The fumed silica particles have a size of 0.3. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Comparative example 9
The comparative example provides a method for quantifying pre-lithium in a high-energy lithium ion battery, which is different from example 1 in that the control ratio P Lithium ion battery is 26%, and includes the following steps:
The lithium foil with the thickness of 5 mu m and the porosity of 10% is adopted for pre-lithium, the cathode electrode is connected to an unreeling mechanism of hot-pressing compounding equipment, the lithium foil upper unreeling mechanism and the lithium foil lower unreeling mechanism are connected, the lithium foil is conveyed to a surface film covering mechanism, fumed silica gel is coated on the surface of the lithium foil in a blade coating mode, rolls are conveyed to pressure rollers to adjust rolls at different positions to the same plane, the rolls enter the hot-pressing compounding mechanism, the hot-pressing compounding mechanism adopts double-plane hot pressing, the hot-pressing temperature is 80 ℃, the flat pressing pressure is 8000 kgf, the flat pressing holding time is 20s, the composite electrode roll is conveyed to a tail end winding mechanism after the hot pressing is finished, and the upper part of the winding mechanism is connected with a release film for winding and the lower part of the winding mechanism is connected with the release film for winding. The compounded negative electrode coil is conveyed to die cutting equipment, the size of a die cutting pole piece (not including a pole lug) is 75mm x 105 mm, the size of a double-sided pre-lithium foil is 63 mm x 93 mm, the control proportion P Lithium ion battery is 26%, the cutter head is not directly contacted with the lithium foil in the die cutting process, and continuous operation of the equipment is ensured not to be influenced.
The preparation method of the fumed silica gel comprises the steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2 to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 70 ℃ for 18s, and cooling to form the fumed silica gel; wherein the fumed silica gel is coated on the surface of the lithium foil by a doctor blade method, and the gap between the doctor blade and the edge of the doctor blade is 25 mu m.
The molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L, the concentration of fumed silica in the mixed dispersion liquid is 20 mg/ml, and the organic solvent is ethylene carbonate. The fumed silica particles have a size of 0.3. Mu.m. Wherein the high polymer material provides a framework structure, and the gas phase SiO 2 fills the framework and provides an ion channel.
Analysis of results:
(1) As shown in the cycle performance graphs of the pre-lithium soft-pack batteries with different thicknesses in fig. 2, the cycle test (0.2C) is performed by adopting a high-nickel soft-pack battery (positive electrode 3 layer/negative electrode 4 layer), and the initial discharge capacity of the non-pre-lithium battery in comparative example 1 is significantly lower than the discharge capacities of the pre-lithium batteries in example 1 and comparative example 2; the comparative example 1 has low initial discharge specific capacity, discharge capacity of 1.994Ah after 200 weeks of circulation, and capacity retention rate of 94.64%; example 1 a lithium foil thickness of 5 μm pre-lithium battery had a capacity of 2.107 Ah after 200 weeks of cycling, a capacity retention of 91.81%; comparative example 2a lithium foil having a thickness of 20 μm had a capacity of 1.874 Ah after 200 cycles and a capacity retention of 89.5%, and it was found that neither pre-lithium nor excessive pre-lithium caused a capacity drop of the lithium battery.
As shown in EIS diagrams before and after cycling of the pre-lithium soft-pack battery with different thicknesses in fig. 3, comparative example 1 (not pre-lithium) and comparative example 2 (20 μm pre-lithium) are similar to example 1 (5 μm pre-lithium) pre-lithium in terms of initial capacity, but in the cycling process, too much lithium foil of comparative example 2 cannot participate in the charging and discharging process of the battery, so that dead lithium phenomenon is caused, and a byproduct layer is gradually accumulated on the surface of a pole piece, so that the impedance in the later cycle is obviously larger than that of the non-pre-lithium battery of comparative example 1 and the pre-lithium battery of example 1. The importance of quantitative control of the edge effect based on the quantitative thickness is verified again, the conventional pre-lithium method cannot meet the requirement of quantitative control, the phenomenon that the pre-lithium is first effectively improved but the capacity decays too fast is easily caused, and the industrial application of the battery is seriously hindered.
(2) Preparing a 9-series high-nickel-system multilayer soft-package battery (positive electrode 3 layers and negative electrode 4 layers) by adopting the negative electrode plates of the example 1, the comparative example 3 and the comparative example 4 after finishing the die cutting of the electrode plates, and carrying out charge and discharge tests on different batteries by adopting 0.2C; the effect of pressure on the battery pre-lithium effect was examined and the results are shown in table 1:
TABLE 1 Effect of flat pressure on Pre-lithium Battery initial Effect and cyclability
Compared with the embodiment 1, increasing the flat pressing pressure can improve the compaction density of the lithium foil, and the porous lithium foil with high compaction density can increase the contact area with the surface of the negative electrode plate, so that the conversion efficiency of active lithium ions is facilitated, but too large pressure (such as the comparative example 4) can increase the compaction density and bring about the reduction of the porosity of the lithium foil, the lower porosity is easy to cause the reduction of the self liquid retaining capacity of the lithium foil material, and electrolyte cannot effectively infiltrate the lithium foil material, so that the internal resistance of the battery is increased; active lithium ions cannot be converted effectively, and the first effect is reduced. When the hot flat pressure is too small (as in comparative example 3), the internal resistance of the high-nickel lithium ion battery is large, so that the circulation stability is reduced.
(3) The cathode plates obtained in the embodiment 1 and the comparative example 5 are assembled into single-layer soft-package batteries respectively, and electrochemical alternating current impedance of the single-layer soft-package batteries in the embodiment 1 and the comparative example 5 is tested respectively, as shown in fig. 4, it can be seen that mass transfer and diffusion impedance inside the battery after SiO 2 gel is added is obviously smaller than that of the comparative example without SiO 2 gel, a network ion channel formed by the gel plays a role in promoting mass transfer, the whole capacity of the battery is further stabilized in the battery circulation process, and the lithium precipitation phenomenon caused by overlarge local current density and uneven conduction rate is effectively avoided on the premise of activating lithium ions by adopting a micro-step structure.
(4) The negative electrode sheets of example 1, comparative example 1 and comparative examples 6-9 after finishing the pole piece die cutting are adopted to prepare 9 series high nickel system multilayer soft package batteries (positive electrode 3 layers and negative electrode 4 layers), and different batteries are subjected to charge and discharge tests by adopting 0.2C; the porous lithium foil coverage area was quantitatively controlled by the edge effect control method, and the results are shown in table 2:
table 2 edge control effect on pre-lithium battery head efficiency and capacity
Example 1 quantitatively controls the ratio P Lithium ion battery to 11%, the double sided pre-lithium foil size to 70 mm x 100 mm, P Lithium ion battery < 10% compared to comparative examples 6 and 7, and P Lithium ion battery > 15% for comparative examples 8 and 9, example 1 has the highest initial efficiency and capacity.
The overall pre-lithium P Lithium ion battery of comparative example 6 is less than 10%, the edge effect of the capacity is weakened, the internal impedance is increased, as shown in fig. 5, the edge of comparative example 8 is controlled to be 5mm, P Lithium ion battery (21 percent) is more than 15%, the overall discharge capacity of the battery does not reach the design value, namely, the lithium source is insufficient, the 9-series ternary and silicon oxygen high-energy battery system cannot be met, the edge effect of the electrode plate of example 1 is controlled to be 11%, and the pre-lithiated high-energy lithium ion battery with low impedance, high capacity and stable circulation is realized.
Application example 1
The lithium ion soft package battery with high energy of the pre-lithium of the embodiment 1 is assembled by adopting a lamination process, the surface density of the high nickel anode material and the active material ratio of the silicon oxygen anode material are regulated and controlled, the N/P ratio is designed to be 0.95 according to the edge effect capacity C of the lithium foil pre-lithium so as to just meet the requirement of the lithium ion intercalation anode vacancy after the primary charging, and the lamination layers of 10 positive electrode layers and 11 negative electrode layers are laminated to complete the assembly of the battery core of the pole piece lamination.
The 0.1C primary charge and discharge is adopted, the discharge capacity reaches 8.805 Ah, the primary effect is improved to 90.51%, the discharge median voltage is 3.778V, the single energy density reaches 370.15 wh/kg, and the energy density is superior to that of the current mainstream lithium ion battery. The 0.3C test was used in the cycle test, and the capacity retention after 100 cycles exceeded 95% (as shown in FIG. 6). Compared with the prior high-energy lithium ion battery, the method has the technical problems that a thick electrode, a poor electrolyte, an ultrathin current collector and the like are required to be solved, and the pre-lithium process cannot be quantitative, the safety cannot be guaranteed, the energy consumption is high and the like. According to the invention, under a high-energy system, only the lithium foil hot-pressing composite process is ensured, and based on the thickness of the ultrathin porous lithium foil, the edge effect quantitative technical control is carried out on the whole, so that unnecessary technical and process requirements are reduced, and the pre-lithium efficiency and capacity improving effect can be effectively improved.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (10)
1. The method for quantitatively pre-lithium of the high-nickel system high-energy lithium ion battery is characterized by comprising the following steps of:
(1) The method comprises the steps of adopting a lithium foil as a lithium supplementing raw material, conveying the lithium foil to a surface film coating mechanism, and coating fumed silica gel on the surface of the lithium foil to form a buffer layer;
(2) Respectively feeding the negative electrode coil and the lithium foil coated with the buffer layer to a pressure roller, adjusting coiled materials at different positions to the same plane, and loading the lithium foil on the negative electrode plate through a hot flat pressing composite mechanism, wherein the buffer layer is arranged between the lithium foil and the negative electrode plate; removing a release film on the surface of the lithium foil after hot flat pressing compounding and rolling to obtain a pre-lithium negative electrode roll;
(3) Die cutting is carried out on the anode coil after lithium preparation, and in the die cutting process, the cutter head is not directly contacted with the lithium foil; the edge distance between the lithium foil and the negative electrode plate is quantitatively controlled to form a micro-step structure, namely the size of the negative electrode plate is larger than that of the lithium foil.
2. The method for quantitatively pre-lithium of the high-nickel-system high-energy lithium ion battery according to claim 1, wherein the method comprises the following steps of: the lithium foil in the step (1) is a porous lithium foil, the porosity of the porous lithium foil is 10% -15%, the pore diameter is 1 mu m, and the thickness is 3-10 mu m.
3. The method for quantitatively pre-lithium of the high-nickel-system high-energy lithium ion battery according to claim 2, wherein the method comprises the following steps of: the preparation method of the fumed silica gel in the step (1) comprises the following steps of dissolving acrylamide and methylene bisacrylamide in an organic solvent, adding fumed SiO 2, uniformly mixing to obtain a mixed dispersion liquid, dissolving the mixed dispersion liquid at 60-80 ℃ for 15-20s, and cooling to form the fumed silica gel; wherein, the fumed silica gel is coated on the surface of the lithium foil by a blade coating mode, and the gap between the blade edges is 5-50 mu m.
4. The method for quantitatively pre-lithium of the high-nickel-system high-energy lithium ion battery according to claim 3, wherein the method comprises the following steps of: the molar ratio of the acrylamide to the methylenebisacrylamide is 1:2, the concentration of acrylamide in the mixed dispersion liquid is 1mol/L; the concentration of the fumed silica in the mixed dispersion liquid is 10-30 mg/ml, and the particle size of the fumed silica is 0.2-0.5 mu m; the organic solvent includes ethylene carbonate, dimethyl carbonate and tetraethylene glycol dimethyl ether.
5. The method for quantitatively pre-lithium of the high-nickel-system high-energy lithium ion battery according to claim 3, wherein the method comprises the following steps of: the conditions of hot-pressing compounding in the step (2) are as follows: the temperature is 80-100 ℃, the flattening pressure is 8000-9000 kgf, and the flattening holding time is 20-25 s.
6. The method for quantitatively pre-lithium of the high-nickel-system high-energy lithium ion battery according to claim 5, wherein the method comprises the following steps of: the hot flat pressing compounding mechanism in the step (2) is divided into a roll feeding part and a roll winding part, wherein the roll feeding part is used for unreeling, and the upper and lower lithium foils and the middle negative coiled material are conveyed to the hot flat pressing mechanism for hot pressing compounding, so that the pre-lithium of the negative pole piece is completed; the winding part uses winding mechanisms, the upper layer winding mechanism and the lower layer winding mechanism respectively retract the negative electrode roll pre-lithium foil upper layer release film and the lower layer release film, and the middle layer winding mechanism retracts the negative electrode coiled material after pre-lithium.
7. The method for quantitatively pre-lithium of the high-nickel-system high-energy lithium ion battery according to claim 6, wherein the method comprises the following steps of: the release film refers to a separator film that is not tacky or has slight tackiness after contact with limited conditions of a lithium foil material.
8. The method for quantitatively pre-lithium of a high-nickel-system high-energy lithium ion battery according to any one of claims 1 to 7, wherein: in the step (3), the control ratio P Lithium ion battery = (full-size area of the electrode plate-S Lithium ion battery )/full-size area of the electrode plate is 100%, wherein the full-size area of the electrode plate does not contain a tab, S Lithium ion battery is the area of the lithium foil, and the edge control ratio P Lithium ion battery is 10% -15%; the length and width of the lithium foil need to be the same relative to the size reduction value of the battery negative electrode tab.
9. The method for quantitatively pre-lithium of the high-nickel-system high-energy lithium ion battery according to claim 8, wherein the method comprises the following steps of: the edge effect capacity C of the lithium foil pre-lithium is: c=s Lithium ion battery *H Lithium ion battery *ρ Lithium ion battery *C Lithium foil ×0.9, where S Lithium ion battery is the area of the lithium foil, H Lithium ion battery is the thickness of the lithium foil, ρ Lithium ion battery is the metal density of the lithium foil, C Lithium foil is the theoretical gram capacity of lithium metal 3860 mAh/g, and 0.9 is the control coefficient.
10. A high-nickel-system high-energy lithium ion battery obtained by the quantitative pre-lithium method of any one of claims 1 to 9.
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