Formation and capacity determination method of lithium ion battery containing positive electrode lithium supplement additive
By setting different voltage ranges and charge/discharge strategies during the formation and capacity testing of lithium-ion batteries, the problem of insufficient delithiation of positive electrode lithium replenishment additives was solved, ensuring the chemical stability and energy density of lithium-ion batteries and improving the cycle life of batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- REPT BATTERO ENERGY CO LTD
- Filing Date
- 2023-03-21
- Publication Date
- 2026-06-02
AI Technical Summary
In the existing technology, the lithium-ion additives in the positive electrode do not fully delithiate lithium ions during the formation and capacity testing of lithium-ion batteries, resulting in lithium plating in the cell. Furthermore, the lithium plating overlaps with the voltage range of transition metal oxides, affecting the stability of the electrolyte and the cycle stability and energy density of the battery.
By employing specific formation and capacity testing methods and setting different voltage ranges and charge/discharge strategies, we can prevent the simultaneous delithiation of lithium by the positive electrode lithium supplementation additive and transition metal oxides, ensuring that lithium ions are fully extracted and forming a stable battery chemical system.
It achieves the full extraction of lithium additives in the positive electrode of lithium-ion batteries, maintains the internal chemical stability of the battery, improves the battery energy density and cycle life, and avoids lithium plating.
Smart Images
Figure CN116435622B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new energy technology, specifically to a method for the formation and capacity testing of a lithium-ion battery containing a positive electrode lithium supplementation additive. Background Technology
[0002] The rapid development of technologies such as electric vehicles and electronic devices has led to a continuous increase in demand for high-energy-density lithium-ion batteries. As a crucial measure to improve battery energy density, the application of high-specific-capacity anode materials has also attracted increasing attention. However, compared to traditional graphite-based materials, high-specific-capacity anode materials exhibit larger initial irreversible capacity and lower cycle stability, severely impacting battery energy density and lifespan. Therefore, for the practical application of high-capacity anodes, there is an urgent need to develop commercially available pre-lithiation technologies to compensate for irreversible capacity losses during initial operation and cycling.
[0003] Currently, the mainstream pre-lithiation methods are mainly divided into two types: negative electrode pre-lithiation and positive electrode pre-lithiation. Negative electrode pre-lithiation primarily involves adding lithium foil or lithium powder to the negative electrode sheet. However, due to the extremely reactive nature of lithium, the processing carries significant safety risks, high costs, and is difficult to commercialize on a large scale. Positive electrode pre-lithiation mainly involves adding positive electrode lithium-adding additives during the positive electrode slurry process. Utilizing the high initial delithiation capacity and low initial lithium insertion capacity of these additives, excess lithium ions are released from the positive electrode during the first charge, while the number of lithium insertion vacancies in the positive electrode does not significantly increase during the first discharge, thus replenishing the lithium ions in the entire battery. Positive electrode pre-lithiation has lower processing requirements, lower equipment requirements, lower safety risks, and is easier to mass-produce. Currently, the more mature positive electrode lithium-adding additives are Li5FeO4 and Li2NiO2, which are used in both lithium iron phosphate batteries and ternary lithium batteries. However, when conventional formation and capacity testing methods are applied to batteries containing positive electrode lithium replenishment additives, insufficient lithium removal by the lithium replenishment additives can lead to lithium plating in the cell. Furthermore, the voltage range during which the lithium replenishment additives remove a large amount of lithium overlaps with the voltage range during which the transition metal oxides remove a large amount of lithium. This results in the lithium replenishment additives and transition metal oxides removing lithium simultaneously at high voltages, which can affect the stability of other chemical elements such as electrolytes. Summary of the Invention
[0004] The purpose of this invention is to address the problems existing in the prior art by providing a formation and capacity testing method for lithium-ion batteries containing a positive electrode lithium replenishment additive. This invention proposes a formation and capacity testing process suitable for lithium iron phosphate, lithium cobalt oxide, and ternary battery systems, ensuring that the positive electrode lithium replenishment additive can fully extract lithium ions without compromising the stability of other chemical elements in the overall battery chemical system during the lithium removal process, thus ensuring the cycle stability and storage stability of the entire battery.
[0005] The objective of this invention can be achieved through the following methods:
[0006] This invention provides a method for the formation and capacity testing of a lithium-ion battery containing a positive electrode lithium supplementation additive, the method comprising the following steps:
[0007] S1. Assemble a negative electrode, an electrolyte, and a positive electrode into a lithium-ion battery; the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material; the positive electrode active material includes a lithium transition metal oxide and a lithium supplementation additive.
[0008] S2. Perform formation charging on the lithium-ion battery;
[0009] S3. Set the average voltage at which the lithium additive first extracts its specific capacity in the low percentage range to V1, the average voltage at which it first extracts its specific capacity in the high percentage range to V2, and the maximum operating voltage of the lithium transition metal oxide to V3.
[0010] S4. Determine if V3 is less than 4V, and perform capacity testing accordingly:
[0011] (1) If V3 is less than 4V, charge the lithium-ion battery according to the following steps:
[0012] ① Charge at a constant rate of 0.1-0.4C to 3.7-3.9V, then maintain constant voltage until the current is 0.01-0.1C, and let stand for 3-30 minutes;
[0013] ② Charge at a constant rate of 0.1-0.4C to V2±0.1V, then maintain constant voltage until the current is 0.01-0.1C, and let stand for 3-30 minutes;
[0014] ③ Charge at a constant rate of 0.01-0.1C to 4.1±0.1V, let stand for 3-30 minutes; then the capacity testing process is complete;
[0015] (2) If V3 is greater than or equal to 4V, charge and discharge the lithium-ion battery according to the following steps:
[0016] ① Charge at a constant rate of 0.1-0.4C to V2±0.1V, then maintain constant voltage until the current is 0.01-0.1C, and let stand for 3-30 minutes;
[0017] ② Discharge at a constant rate of 0.1-0.5C to V1±0.1V, and let stand for 3-30 minutes;
[0018] ③ Repeat steps ① and ② for charging and discharging 2-5 times; the more times it is repeated, the more complete the lithium removal by the lithium additive will be, but the longer the charging time will also be. Generally, repeating it 2 times is sufficient.
[0019] ④ Charge at a constant rate of 0.1-0.5C to V3±0.1V, and let stand for 3-30 minutes; then the capacity testing process is complete.
[0020] The primary purpose of this capacity grading process is to ensure that the extensive delithiation of lithium by the lithium-replenishing additive bypasses the voltage range where transition metal oxides (TMOs) undergo significant delithiation. This avoids the impact on the stability of the electrolyte and other chemical elements caused by the simultaneous delithiation of lithium by the lithium-replenishing additive and TMOs, thus maintaining the stability of the battery's internal chemical system. Using this process, the lithium-replenishing additive can fully delithigate lithium ions while the electrolyte remains stable. The TMOs also fully delithigate lithium ions, and the negative electrode can fully intercalate the lithium ions delithigate from the positive electrode, preventing lithium plating. Conventional capacity grading processes, when used with batteries containing lithium-replenishing additives, can lead to insufficient delithiation by the additives, resulting in lithium plating within the cell. For conventional cells without lithium-replenishing additives, using the above capacity grading process will not cause any negative effects other than increasing the grading time.
[0021] In one embodiment of the present invention, in step S1, the lithium transition metal oxide includes LiCoO2, LiFePO4, and Li x Ni y M 1-y One or more of O2; wherein 0.9≤x≤1.2, 0.5≤y<1, and M includes one or more of Co, Mn, Al, Mg, Ti, Fe, Cr, Mo, and Ca.
[0022] In one embodiment of the present invention, in step S1, the lithium-replenishing additive includes one or more of Li6CoO4, Li2NiO2, Li5FeO4, Li2O, Li3N, and their respective modified materials; the modification is coating modification and / or doping modification. The mass ratio of the lithium-replenishing additive to the positive electrode active material is 0.5-15%, preferably 1-5%.
[0023] In one embodiment of the present invention, the initial charging capacity of the lithium replenishment additive is 260-3000 mAh / g; preferably 400-3000 mAh / g. The larger the initial charging capacity of the lithium replenishment additive, the more significant the improvement in energy density. The irreversible capacity of the lithium replenishment additive is 250-3000 mAh / g; preferably 400-3000 mAh / g. The larger the irreversible capacity of the lithium replenishment additive, the better the cycle life.
[0024] In the secondary battery of the present invention, the positive electrode active material can be a positive electrode active material known in the art for use in secondary batteries. Optionally, the positive electrode active material can be selected from one or more of lithium transition metal oxides and their respective modified materials. The surface on which the positive electrode film layer is disposed has two surfaces opposite each other in its thickness direction. The positive electrode film layer can be disposed on either of the two surfaces, or disposed on both surfaces respectively.
[0025] In one embodiment of the present invention, in step S1, the lithium-ion battery includes one of a pouch battery, a prismatic battery, and a cylindrical battery. The pouch battery is subjected to capacity testing under a pressure of 0.1-0.4 MPa, while the prismatic and cylindrical batteries are subjected to capacity testing under a negative pressure of -65 to -75 kPa. Specifically: after the pouch battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing under a pressure of 0.1-0.4 MPa throughout, following the prescribed procedure, and then the pressure is removed to complete the cell fabrication. The prismatic or cylindrical batteries are subjected to capacity testing under a negative pressure of -65 to -75 kPa throughout, following the prescribed procedure to complete the cell fabrication.
[0026] As one embodiment of the present invention, the specific steps of formation charging in step S2 are as follows:
[0027] S2-1. Charge at a constant rate of 0.01-0.2C for 40-80 minutes, with a cutoff voltage of 3V±0.1V. Once the charging time reaches 40-80 minutes or the cutoff voltage reaches 3V±0.1V, proceed to the next step.
[0028] S2-2. Charge at a constant rate of 0.05-0.3C for 40-80 minutes, with a cutoff voltage of 3.4V±0.1V. Once the charging time reaches 40-80 minutes or the cutoff voltage reaches 3.4V±0.1V, proceed to the next step.
[0029] S2-33. Charge at a constant rate of 0.1-0.5C for 40-80 minutes, with a cutoff voltage of 3.7V±0.1V. Once the charging time reaches 40-80 minutes or the cutoff voltage reaches 3.7V±0.1V, proceed to the next step.
[0030] In step S3, the lower limit of the low percentage range is not less than 5%, and the upper limit is not more than 30%; the lower limit of the high percentage range is not less than 50%, and the upper limit is not more than 90%. The low percentage range is preferably 5%-30%, and the high percentage range is preferably 50%-90%, that is, the average voltage at which the lithium additive first extracts 5%-30% of its capacity is set as V1, and the average voltage at which it first extracts 50%-90% of its capacity is set as V2.
[0031] In one embodiment of the present invention, in step S3, the low percentage range is 5%-30%, and the high percentage range is 50%-90%.
[0032] When the lithium supplement additive is Li6CoO4, the average voltage (V1) for the first extraction of 5%-30% of the capacity is 3.5V, and the average voltage (V2) for the first extraction of 50%-90% of the capacity is 3.9V.
[0033] When the lithium supplement additive is Li2NiO2, the average voltage (V1) for the first extraction of 5%-30% of the capacity is 3.5V, and the average voltage (V2) for the first extraction of 50%-90% of the capacity is 4.0V.
[0034] When the lithium supplement additive is Li5FeO4, the average voltage (V1) for the first extraction of 5%-30% of the specific capacity is 3.6V, and the average voltage (V2) for the first extraction of 50%-90% of the specific capacity is 3.9V.
[0035] When the lithium supplement additive is Li2O, the average voltage (V1) for the first extraction of 5%-30% of the capacity is 2.3V, and the average voltage (V2) for the first extraction of 50%-90% of the capacity is 3.8V.
[0036] When the lithium supplement additive is Li3N, the average voltage (V1) for the first extraction of 5%-30% of the capacity is 3.8V, and the average voltage (V2) for the first extraction of 50%-90% of the capacity is 4.1V.
[0037] As one embodiment of the present invention, in step S4, when the transition metal oxide is only lithium iron phosphate (LiFePO4), V3 is less than 4V; when the transition metal oxide contains LiCoO2 and / or Li... x Ni y M 1-y When O2 is present, V3 is greater than or equal to 4V.
[0038] The purpose of step S2 is to form a stable SEI film.
[0039] In step S4, when V3 is less than 4V, the purpose of the first step of charging in step (1) is to fully delithigate the lithium transition metal oxide (such as LiFePO4), the purpose of the second step of charging is to allow the positive electrode lithium replenishment additive to remove most of the lithium ions in the first stage, and the purpose of the third step of charging is to allow the positive electrode lithium replenishment additive to remove the remaining lithium ions in the second stage. By separating the second and third steps from the first step, the reaction between the delithiation products generated by the positive electrode lithium replenishment additive during the simultaneous delithiation of lithium transition metal oxide and the electrolyte is avoided, thereby maintaining the internal electrochemical stability of the battery.
[0040] In step S4, when V3 is greater than or equal to 4V, the purpose of charging and discharging in steps ① and ② of step (2) within the V1-V2 range is to ensure that the positive electrode lithium replenishment additive is fully delithiated within the V1-V2 voltage range, thus preventing the delithiation products of the positive electrode lithium replenishment additive from affecting the electrolyte stability at higher voltages. The purpose of charging to V3 is to ensure that the lithium transition metal oxide is completely delithiated in the third stage.
[0041] In one embodiment of the present invention, in step S1, the positive current collector can be made of a material with good conductivity and mechanical strength, such as aluminum foil or carbon-coated aluminum foil, but is not limited thereto.
[0042] In one embodiment of the present invention, in step S1, the positive electrode film layer further includes a binder and a conductive agent. The binder includes one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. The conductive agent may include one or more of superconducting carbon, carbon black (such as Super P, acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode film layer is obtained by coating a positive electrode slurry and then drying and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, conductive agent, and binder in a solvent and stirring until homogeneous. The solvent includes N-methylpyrrolidone (NMP).
[0043] As one embodiment of the present invention, in step S1, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and including a negative electrode active material, wherein the negative electrode active material includes graphite and silicon oxide materials.
[0044] As one embodiment of the present invention, in step S1, the negative electrode current collector is a material with good conductivity and mechanical strength, such as copper foil, but is not limited thereto.
[0045] In one embodiment of the present invention, in step S1, the negative electrode film layer further includes a binder, a conductive agent, and other optional additives. The conductive agent may include one or more of superconducting carbon, carbon black (e.g., Super P, acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid (PAA), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). Other optional additives include thickeners (such as sodium carboxymethyl cellulose CMC-Na) and PTC thermistor materials. The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry coating is typically formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and optional additives in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone (NMP) or deionized water.
[0046] In one embodiment of the present invention, in step S1, the electrolyte is selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions). In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte lithium salt and a solvent. The lithium salt may be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiCIO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorodioxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate). The solvent can be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 14-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE). In the secondary battery of this application, there are no specific restrictions on the type of electrolyte; it can be selected according to requirements.
[0047] In one embodiment of the present invention, in step S1, the electrolyte further includes additives. The additives include negative electrode film-forming additives or positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.
[0048] In one embodiment of the present invention, step S1 further includes a separator membrane in the secondary battery. The separator membrane is disposed between the positive electrode and the negative electrode, serving as a separator. The secondary battery of this aspect does not have particular limitations on the type of separator membrane; any known porous separator membrane used in secondary batteries can be selected. For example, the separator membrane can be selected from one or more of the following: glass fiber film, non-woven fabric film, polyethylene film, polypropylene film, polyvinylidene fluoride film, and multilayer composite films comprising one or more of these materials.
[0049] In one embodiment of the present invention, in step S1, the lithium-ion battery further includes an outer packaging, which is used to encapsulate the positive electrode, the negative electrode, and the electrolyte. The outer packaging includes either a hard shell or a soft pack; a hard shell may be, for example, a hard plastic shell, an aluminum shell, or a steel shell; a soft pack may be, for example, a pouch-type soft pack. The material of the soft pack can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
[0050] As one embodiment of the present invention, in step S1, the secondary battery can be prepared using methods known in the art. For example, a positive electrode, a separator, and a negative electrode are formed into an electrode assembly through a winding process or a stacking process, wherein the separator is located between the positive and negative electrode sheets and serves to isolate them; the electrode assembly is placed in an outer package, an electrolyte is injected, and the package is sealed to obtain a secondary battery.
[0051] As one embodiment of the present invention, in step S1, the shape of the secondary battery is not particularly limited, and it can be cylindrical, square, pouch, or any other arbitrary shape.
[0052] Compared with the prior art, the present invention has the following beneficial effects:
[0053] (1) The unique feature of this invention is that it has customized a formation and capacity testing process suitable for batteries containing positive electrode lithium supplementation additives, targeting the delithiation characteristics of positive electrode lithium supplementation additives. This avoids the reaction between the delithiation products generated by the simultaneous delithiation of positive electrode lithium supplementation additives and the electrolyte when a large amount of lithium is delithiated from lithium transition metal oxides. This maintains the internal electrochemical stability of the battery and ensures that lithium ions are fully extracted from the positive electrode lithium supplementation additives, thereby improving the battery energy density and cycle life.
[0054] (2) Simultaneously, this invention has found that pouch batteries must undergo the entire formation and capacity testing process under a pressure of 0.1-0.4 MPa. If the pressure is too low or not carried out throughout the entire process, the oxygen generated after the lithium replenishment additives, especially Li5FeO4, are delithiated cannot be completely discharged, causing some oxygen to be reabsorbed by the electrode, resulting in black spots or lithium plating on the negative electrode. If the pressure is too high, the positive and negative electrodes will be subjected to excessive pressure, leading to excessively small electrode porosity and decreased electrolyte wettability, resulting in poor cycle performance. Square or cylindrical batteries must undergo the entire formation and capacity testing process under a negative pressure of -65 to -75 kPa according to the following prescribed procedure. If the pressure is too low or not carried out throughout the entire process, the oxygen generated after the lithium replenishment additives, especially Li5FeO4, are delithiated cannot be completely discharged, causing some oxygen to be reabsorbed by the electrode, resulting in black spots or lithium plating on the negative electrode. If the pressure is too high, the core structure may be damaged, leading to safety risks such as short circuits. Attached Figure Description
[0055] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:
[0056] Figure 1 These are disassembled images of the fully charged electrode sheet from Example 1;
[0057] Figure 2 The images are disassembled images of a fully charged electrode sheet for comparison. Detailed Implementation
[0058] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.
[0059] The electrolyte composition used in the embodiments and comparative examples of this invention is as follows: 10 wt% lithium hexafluorophosphate, 5 wt% lithium difluorosulfonyl imide, 0.5 wt% vinylene carbonate, 0.8 wt% lithium difluorophosphate, 8 wt% FEC content, and the balance being an organic solvent; the organic solvent is obtained by mixing ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate in a mass ratio of 20:70:5:5; the positive electrode current collector is aluminum foil, and the negative electrode current collector is copper foil.
[0060] Example 1
[0061] This embodiment provides a soft-pack stacked secondary battery:
[0062] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li5FeO4 + 96% NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 For O2), the V1 voltage of Li5FeO4 is 3.6V, and the V2 voltage is 3.9V; the maximum operating voltage of NCM811 is 4.2V.
[0063] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0064] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing (S1-S8 below) under a pressure of 0.3 MPa throughout the process, followed by evacuation to complete the cell fabrication:
[0065] S1, charge to 3V at a constant rate of 0.05C;
[0066] S2, charged to 3.4V at a constant rate of 0.1C;
[0067] S3, charged to 3.7V at a constant rate of 0.2C;
[0068] S4, charge at a constant rate of 0.3C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0069] S5, discharge at a constant rate of 0.3C to 3.6V, and let stand for 5 minutes;
[0070] S6, charge at a constant rate of 0.3C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0071] S7, discharge at a constant rate of 0.3C to 3.6V, and let stand for 5 minutes;
[0072] S8, charge at a constant rate of 0.3C to 4.2V, and let stand for 5 minutes;
[0073] The battery's minimum operating voltage is 2.8V, and its maximum operating voltage is 4.2V.
[0074] Example 2
[0075] This embodiment provides a square secondary battery:
[0076] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li2NiO2 + 96% LiFePO4, where the V1 voltage of Li2NiO2 is 3.5V and the V2 voltage is 4.0V; and the V3 voltage of LiFePO4 is 3.65V.
[0077] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0078] After the battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing (S1-S6 below) under a constant negative pressure of -70KPA, followed by degassing to complete the cell fabrication:
[0079] S1, charged at a constant rate of 0.05C for 60 minutes;
[0080] S2, charged at a constant rate of 0.1C for 60 minutes;
[0081] S3, charged at a constant 0.2C rate for 60 minutes;
[0082] S4, charge at a constant rate of 0.3C to 3.7V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0083] S5, charge at a constant rate of 0.1C to 4.0V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0084] S6, charged to 4.1V at a constant rate of 0.03C, then left to stand for 5 minutes.
[0085] The battery's minimum operating voltage is 2.0V, and its maximum operating voltage is 3.65V.
[0086] Example 3
[0087] This embodiment provides a soft-pack laminated secondary battery.
[0088] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li6CoO4 + 96% NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 For O2), the V1 voltage of Li6CoO4 is 3.5V and the V2 voltage is 3.9V; the V3 voltage of NCM811 is 4.2V.
[0089] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0090] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing (S1-S8 below) under a pressure of 0.1 MPa throughout the process, followed by evacuation to complete the cell fabrication:
[0091] S1, charge to 3V at a constant rate of 0.05C;
[0092] S2, charged to 3.4V at a constant rate of 0.1C;
[0093] S3, charged to 3.7V at a constant rate of 0.2C;
[0094] S4, charge at a constant rate of 0.2C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0095] S5, discharge at a constant rate of 0.3C to 3.5V, and let stand for 5 minutes;
[0096] S6, charge at a constant rate of 0.2C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0097] S7, discharge at a constant rate of 0.3C to 3.5V, and let stand for 5 minutes;
[0098] S8, charge at a constant rate of 0.3C to 4.2V, and let stand for 5 minutes;
[0099] The battery's minimum operating voltage is 2.8V, and its maximum operating voltage is 4.2V.
[0100] Example 4
[0101] This embodiment provides a soft-pack laminated secondary battery.
[0102] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li₂O + 96% NCM₈11 (LiNi 0.8 Co 0.1 Mn 0.1 For O2), the V1 voltage of Li2O is 2.3V and the V2 voltage is 3.8V; the V3 voltage of NCM811 is 4.2V.
[0103] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0104] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing (S1-S8 below) under a pressure of 0.3 MPa throughout the process, followed by evacuation to complete the cell fabrication:
[0105] S1, charge to 3V at a constant rate of 0.05C;
[0106] S2, charged to 3.4V at a constant rate of 0.1C;
[0107] S3, charged to 3.7V at a constant rate of 0.2C;
[0108] S4, charge at a constant rate of 0.3C to 3.8V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0109] S5, discharge at a constant rate of 0.2C to 2.3V, and let stand for 5 minutes;
[0110] S6, charge at a constant rate of 0.3C to 3.8V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0111] S7, discharge at a constant rate of 0.2C to 2.3V, and let stand for 5 minutes;
[0112] S8, charge at a constant rate of 0.4C to 4.2V, then let stand for 5 minutes;
[0113] The battery's minimum operating voltage is 2.8V, and its maximum operating voltage is 4.2V.
[0114] Example 5
[0115] This embodiment provides a soft-pack stacked secondary battery:
[0116] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li3N + 96% NCM523 (LiNi 0.5 Co 0.2 Mn 0.3 For O2), the V1 voltage of Li3N is 3.8V and the V2 voltage is 4.1V; the V3 voltage of NCM523 is 4.35V.
[0117] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0118] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing (e.g., S1-S8) under a constant pressure of 0.2 MPa, followed by evacuation to complete the cell fabrication:
[0119] S1, charge to 3V at a constant rate of 0.05C;
[0120] S2, charged to 3.4V at a constant rate of 0.1C;
[0121] S3, charged to 3.7V at a constant rate of 0.2C;
[0122] S4, charge at a constant rate of 0.3C to 4.1V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0123] S5, discharge at a constant rate of 0.3C to 3.8V, and let stand for 5 minutes;
[0124] S6, charge at a constant rate of 0.3C to 4.1V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0125] S7, discharge at a constant rate of 0.3C to 3.8V, and let stand for 5 minutes;
[0126] S8, charge at a constant rate of 0.3C to 4.35V, then let stand for 5 minutes;
[0127] The battery's minimum operating voltage is 2.8V, and its maximum operating voltage is 4.35V.
[0128] Example 6
[0129] This embodiment provides a soft-pack wound secondary battery:
[0130] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li5FeO4 + 96% LiCoO2, where the V1 voltage of Li5FeO4 is 3.6V and the V2 voltage is 3.9V; and the V3 voltage of LiCoO2 is 4.4V.
[0131] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0132] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing under a constant pressure of 0.2 MPa according to the following prescribed procedure, followed by degassing to complete the cell fabrication:
[0133] S1, charge to 3V at a constant rate of 0.05C;
[0134] S2, charged to 3.4V at a constant rate of 0.1C;
[0135] S3, charged to 3.7V at a constant rate of 0.2C;
[0136] S4, charge at a constant rate of 0.3C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0137] S5, discharge at a constant rate of 0.3C to 3.6V, and let stand for 5 minutes;
[0138] S6, charge at a constant rate of 0.3C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0139] S7, discharge at a constant rate of 0.3C to 3.6V, and let stand for 5 minutes;
[0140] S8, charge at a constant rate of 0.3C to 4.4V, then let stand for 5 minutes;
[0141] The battery's minimum operating voltage is 2.8V, and its maximum operating voltage is 4.4V.
[0142] Example 7
[0143] This embodiment provides a soft-pack stacked secondary battery:
[0144] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li5FeO4 + 96% LiFePO4. The V1 voltage of Li5FeO4 is 3.6V and the V2 voltage is 3.9V; the V3 voltage of LiFePO4 is 3.65V.
[0145] The negative electrode sheet comprises the following components by mass fraction: 96% graphite + 1% SP + 1.2% CMC + 1.8% SBR;
[0146] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing under a constant pressure of 0.4 MPa according to the following prescribed procedure, followed by degassing to complete the cell fabrication:
[0147] S1, charged at a constant rate of 0.05C for 60 minutes;
[0148] S2, charged at a constant rate of 0.1C for 60 minutes;
[0149] S3, charged at a constant 0.2C rate for 60 minutes;
[0150] S4, charge at a constant rate of 0.3C to 3.8V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0151] S5, charge at a constant rate of 0.1C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0152] S6, charged to 4.1V at a constant rate of 0.03C, then left to stand for 5 minutes.
[0153] The battery's minimum operating voltage is 2.0V, and its maximum operating voltage is 3.65V.
[0154] Comparative Example 1
[0155] This embodiment provides a soft-pack stacked secondary battery:
[0156] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li5FeO4 + 96% NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 For O2), the V1 voltage of Li5FeO4 is 3.6V and the V2 voltage is 3.9V; the V3 voltage of NCM811 is 4.2V.
[0157] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0158] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing under a constant pressure of 0.05 MPa according to the following prescribed procedure, followed by degassing to complete the cell fabrication:
[0159] S1, charge to 3V at a constant rate of 0.05C;
[0160] S2, charged to 3.4V at a constant rate of 0.1C;
[0161] S3, charged to 3.7V at a constant rate of 0.2C;
[0162] S4, charge at a constant rate of 0.3C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0163] S5, discharge at a constant rate of 0.3C to 3.6V, and let stand for 5 minutes;
[0164] S6, charge at a constant rate of 0.3C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0165] S7, discharge at a constant rate of 0.3C to 3.6V, and let stand for 5 minutes;
[0166] S8, charge at a constant rate of 0.3C to 4.2V, and let stand for 5 minutes;
[0167] The battery's minimum operating voltage is 2.8V, and its maximum operating voltage is 4.2V.
[0168] Comparative Example 2
[0169] This embodiment provides a soft-pack stacked secondary battery:
[0170] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li5FeO4 + 96% NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 For O2), the V1 voltage of Li5FeO4 is 3.6V and the V2 voltage is 3.9V; the V3 voltage of NCM811 is 4.2V.
[0171] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0172] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing under a constant pressure of 0.6 MPa according to the following prescribed procedure, followed by degassing to complete the cell fabrication:
[0173] S1, charge to 3V at a constant rate of 0.05C;
[0174] S2, charged to 3.4V at a constant rate of 0.1C;
[0175] S3, charged to 3.7V at a constant rate of 0.2C;
[0176] S4, charge at a constant rate of 0.3C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0177] S5, discharge at a constant rate of 0.3C to 3.6V, and let stand for 5 minutes;
[0178] S6, charge at a constant rate of 0.3C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0179] S7, discharge at a constant rate of 0.3C to 3.6V, and let stand for 5 minutes;
[0180] S8, charge at a constant rate of 0.3C to 4.2V, and let stand for 5 minutes;
[0181] The battery's minimum operating voltage is 2.8V, and its maximum operating voltage is 4.2V.
[0182] Comparative Example 3
[0183] This embodiment provides a soft-pack laminated secondary battery.
[0184] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li5FeO4 + 96% NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 For O2), the V1 voltage of Li5FeO4 is 3.6V and the V2 voltage is 3.9V; the V3 voltage of NCM811 is 4.2V.
[0185] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0186] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing under a constant pressure of 0.3 MPa according to the following prescribed procedure, followed by degassing to complete the cell fabrication:
[0187] S1, charge to 3V at a constant rate of 0.05C;
[0188] S2, charged to 3.4V at a constant rate of 0.1C;
[0189] S3, charged to 3.7V at a constant rate of 0.2C;
[0190] S4, charge at a constant rate of 0.3C to 4.2V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0191] The battery's minimum operating voltage is 2.8V, and its maximum operating voltage is 4.2V.
[0192] Comparative Example 4
[0193] This embodiment provides a soft-pack stacked secondary battery:
[0194] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li5FeO4 + 96% NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 For O2), the V1 voltage of Li5FeO4 is 3.6V, and the V2 voltage is 3.9V; the maximum operating voltage of NCM811 is 4.2V.
[0195] The negative electrode comprises the following components by mass fraction: 85.7% graphite + 9.5% SiO + 1.1% SP + 3% PAA + 0.6% SBR + 0.1% SWCNT;
[0196] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing under a constant pressure of 0.3 MPa according to the following prescribed procedure, followed by degassing to complete the cell fabrication:
[0197] S1, charge to 3V at a constant rate of 0.05C;
[0198] S2, charged to 3.4V at a constant rate of 0.1C;
[0199] S3, charged to 3.7V at a constant rate of 0.2C;
[0200] S4, charge at a constant rate of 0.3C to 3.9V, then maintain constant voltage until the current is 0.05C, and let stand for 5 minutes;
[0201] S5, discharge at a constant rate of 0.3C to 3.6V, and let stand for 5 minutes;
[0202] S6, charge at a constant rate of 0.3C to 4.2V, and let stand for 5 minutes;
[0203] The battery's minimum operating voltage is 2.8V, and its maximum operating voltage is 4.2V.
[0204] Comparative Example 5
[0205] This embodiment provides a soft-pack stacked secondary battery:
[0206] The positive electrode comprises the following components by mass fraction: 1.1% SP + 0.6% CNT + 1.1% PVDF + 1.2% Li5FeO4 + 96% LiFePO4, where the V1 voltage of Li5FeO4 is 3.6V and the V2 voltage is 3.9V; and the V3 voltage of LiFePO4 is 3.65V.
[0207] The negative electrode sheet comprises the following components by mass fraction: 96% graphite + 1% SP + 1.2% CMC + 1.8% SBR;
[0208] After the soft-pack battery is filled with electrolyte and allowed to stand, it is subjected to capacity testing under a constant pressure of 0.4 MPa according to the following prescribed procedure, followed by degassing to complete the cell fabrication:
[0209] S1, charged at a constant rate of 0.05C for 60 minutes;
[0210] S2, charged at a constant rate of 0.1C for 60 minutes;
[0211] S3, charged at a constant 0.2C rate for 60 minutes;
[0212] S4 is charged to 4.1V at a constant rate of 0.03C, then kept at a constant voltage until the current is 0.05C, and left to stand for 5 minutes; the minimum operating voltage of the battery is 2.0V, and the maximum operating voltage of the battery is 3.65V.
[0213] Application performance testing:
[0214] The batteries prepared in Examples 1-7 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1:
[0215] (1) 45-degree cycle life test: The test is conducted at 45°C.
[0216] Step 1: Discharge at a constant rate of 1C to the minimum operating voltage;
[0217] Step 2, let it sit for 5 minutes;
[0218] Step 3: Charge at a constant rate of 1C to the maximum operating voltage, and then maintain the voltage until the current is 0.05C;
[0219] Step 4: Let it sit for 5 minutes;
[0220] Step 5: Repeat steps 1 to 4 until the discharge capacity decays to 80% of the initial discharge capacity.
[0221] (2) Lithium plating test during full-charge and full-capacity testing:
[0222] Step 1: Charge the battery at a constant rate of 1C to its maximum operating voltage, then maintain the voltage until the current reaches 0.05C; Step 2: Let it stand for 5 minutes.
[0223] Step 3: Disassemble the battery cell and observe whether lithium is deposited on the surface of the negative electrode.
[0224] Table 1
[0225]
[0226]
[0227] Comparing Example 1 and Comparative Example 1, it can be seen that when the pressure during battery capacity testing is too low, some oxygen generated by the delithiation of Li5FeO4 remains in the electrode, leading to black spots and lithium plating. The disassembled image of the fully charged electrode in Example 1 is shown below. Figure 1 The disassembly image of the fully charged electrode sheet (compare to the original image) is shown below. Figure 2 .
[0228] Comparing Example 1 and Comparative Example 2, it can be seen that when the battery is subjected to excessive pressure during capacity formation, the positive and negative electrodes are subjected to too much pressure, which leads to excessively small electrode porosity and decreased electrolyte wettability, resulting in deterioration of cycle life.
[0229] Comparing Example 1 and Comparative Example 3, it can be seen that when the battery formation and capacity testing are not carried out according to the prescribed process, most of the Li5FeO4 is delithiated at high voltage. The released active oxygen reduces the stability of the electrolyte. Furthermore, the high-rate delithiation at high voltage prevents the negative electrode from embedding all the lithium ions in time, resulting in lithium plating. The combined effect leads to poor high-temperature cycling performance.
[0230] Comparing Example 1 and Comparative Example 4, it can be seen that when the number of charge-discharge cycles from V1 to V2 is reduced from 2 to 1 during the battery capacity grading process, Li5FeO4 does not fully release lithium ions, resulting in some residual active oxygen damaging the electrolyte stability during the cycling process and causing deterioration in cycling performance.
[0231] Comparing Example 7 with Comparative Example 5, it can be seen that when the battery in Comparative Example 5 is directly charged to 4.1V during the capacity grading process, Li5FeO4 rapidly releases lithium ions under high voltage, causing the negative electrode to not have enough time to insert all the lithium ions, resulting in lithium plating and deterioration of cycle performance.
[0232] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.
Claims
1. A method for forming and capacity testing a lithium-ion battery containing a positive electrode lithium replenishment additive, characterized in that, The separation and compatibilization method includes the following steps: S1. Assemble a negative electrode, an electrolyte, and a positive electrode into a lithium-ion battery; the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material; the positive electrode active material includes a lithium transition metal oxide and a lithium supplementation additive. S2. Perform formation charging on the lithium-ion battery; S3. Set the average voltage at which the lithium additive first extracts its specific capacity in the low percentage range to V1, the average voltage at which it first extracts its specific capacity in the high percentage range to V2, and the maximum operating voltage of the lithium transition metal oxide to V3. S4. Determine if V3 is less than 4V, and perform capacity testing accordingly: (1) If V3 is less than 4V, charge the lithium-ion battery according to the following steps: ① Charge at a constant rate of 0.1-0.4C to 3.7-3.9V, then maintain constant voltage until the current is 0.01-0.1C, and let stand; ② Charge at a constant rate of 0.1-0.4C to V2±0.1V, then maintain constant voltage until the current is 0.01-0.1C, and let stand; ③ Charge at a constant rate of 0.01-0.1C to 4.1±0.1V, let stand for 3-30 minutes; then the capacity testing process is complete; (2) If V3 is greater than or equal to 4V, charge and discharge the lithium-ion battery according to the following steps: ① Charge at a constant rate of 0.1-0.4C to V2±0.1V, then maintain constant voltage until the current is 0.01-0.1C, and let stand; ② Discharge at a constant rate of 0.1-0.5C to V1±0.1V, then let stand; ③ Repeat steps ① and ② for charging and discharging 2-5 times; ④ Charge at a constant rate of 0.1-0.5C to V3±0.1V, then let stand; then the capacity testing process is complete; In step S3, the lower limit of the low percentage range is not less than 5% and the upper limit is not more than 30%; the lower limit of the high percentage range is not less than 50% and the upper limit is not more than 90%.
2. The method for forming and compatibilizing according to claim 1, characterized in that, In step S1, the lithium transition metal oxide includes LiCoO2, LiFePO4, and Li x Ni y M 1-y One or more of O2; wherein 0.9≤x≤1.2, 0.5≤y<1, and M includes one or more of Co, Mn, Al, Mg, Ti, Fe, Cr, Mo, and Ca.
3. The method for forming and dissolving according to claim 1, characterized in that, In step S1, the lithium supplementation additive includes one or more of Li6CoO4, Li2NiO2, Li5FeO4, Li2O, Li3N and their respective modified materials.
4. The method for forming and compatibilizing according to claim 1, characterized in that, The mass ratio of lithium supplementation additives to positive electrode active materials is 0.5-15%.
5. The method for forming and compatibilizing according to claim 1, characterized in that, In step S1, the lithium-ion battery includes one of the following: a pouch battery, a prismatic battery, and a cylindrical battery. When the lithium-ion battery is a pouch battery, the formation and capacity testing in steps S2-S4 are carried out under a pressure of 0.1-0.4 MPa. When the lithium-ion battery is a square or cylindrical battery, the formation and capacity testing in steps S2-S4 are carried out under a negative pressure of -65 to -75 kPa.
6. The method for forming and compatibilizing according to claim 1, characterized in that, The specific steps of formation charging in step S2 are as follows: S2-1. Charge at a constant rate of 0.01-0.2C for 40-80 minutes, with a cutoff voltage of 3V±0.1V. Once the charging time reaches 40-80 minutes or the cutoff voltage reaches 3V±0.1V, proceed to the next step. S2-2. Charge at a constant rate of 0.05-0.3C for 40-80 minutes, with a cutoff voltage of 3.4V±0.1V. Once the charging time reaches 40-80 minutes or the cutoff voltage reaches 3.4V±0.1V, proceed to the next step. S2-33. Charge at a constant rate of 0.1-0.5C for 40-80 minutes, with a cutoff voltage of 3.7V±0.1V. Once the charging time reaches 40-80 minutes or the cutoff voltage reaches 3.7V±0.1V, proceed to step S3.
7. The method for forming and compatibilizing according to claim 1, characterized in that, In step S3, the low percentage range is 5%-30%, and the high percentage range is 50%-90%. When the lithium supplement additive is Li6CoO4, the average voltage V1 for the first extraction of 5%-30% of the specific capacity is 3.5V, and the average voltage V2 for the first extraction of 50%-90% of the specific capacity is 3.9V. When the lithium supplement additive is Li2NiO2, the average voltage V1 for the first extraction of 5%-30% of the specific capacity is 3.5V, and the average voltage V2 for the first extraction of 50%-90% of the specific capacity is 4.0V. When the lithium supplement additive is Li5FeO4, the average voltage V1 for the first extraction of 5%-30% of the specific capacity is 3.6V, and the average voltage V2 for the first extraction of 50%-90% of the specific capacity is 3.9V. When the lithium supplement additive is Li2O, the average voltage V1 for the first extraction of 5%-30% of the specific capacity is 2.3V, and the average voltage V2 for the first extraction of 50%-90% of the specific capacity is 3.8V. When the lithium supplement additive is Li3N, the average voltage V1 for the first extraction of 5%-30% of the capacity is 3.8V, and the average voltage V2 for the first extraction of 50%-90% of the capacity is 4.1V.
8. The method for forming and dissolving according to claim 1, characterized in that, In step S4, when the transition metal oxide is LiFePO4, V3 is less than 4V; when the transition metal oxide is LiCoO2 and / or Li x Ni y M 1-y When O2 is present, V3 is greater than or equal to 4V.
9. The method for forming and dissolving components according to claim 1, characterized in that, In step S1, the positive current collector includes one of aluminum foil and carbon-coated aluminum foil.